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Arterial blood gas analysis utility in predicting lung injury in blunt chest trauma
Journal Pre-proof Arterial blood gas analysis utility in predicting lung injury in blunt chest trauma Maria Viviana Carlino, Mario Guarino, Arturo Izzo, Daniele Carbone, Maria Immacolata Arnone, Costantino Mancusi, Alfonso Sforza
PII:
S1569-9048(19)30308-8
DOI:
https://doi.org/10.1016/j.resp.2019.103363
Reference:
RESPNB 103363
To appear in:
Respiratory Physiology & Neurobiology
Received Date:
23 August 2019
Revised Date:
15 November 2019
Accepted Date:
19 December 2019
Please cite this article as: Carlino MV, Guarino M, Izzo A, Carbone D, Arnone MI, Mancusi C, Sforza A, Arterial blood gas analysis utility in predicting lung injury in blunt chest trauma, Respiratory Physiology and amp; Neurobiology (2019), doi: https://doi.org/10.1016/j.resp.2019.103363
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.
Arterial blood gas analysis utility in predicting lung injury in blunt chest trauma Maria Viviana Carlino1 MD, Mario Guarino1 MD, Arturo Izzo1 MD, Daniele Carbone1 RN, Maria Immacolata Arnone1-2 MD, Costantino Mancusi2 MD, Alfonso Sforza1 MD.
1. Emergency Department, C. T. O. Hospital, Naples. 2. Federico II University Hospital, Naples.
Financial/nonfinancial disclosures: None declared.
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Declarations of interest: none. Correspondence to: Dr. Maria Viviana Carlino
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Ospedale C.T.O. (Azienda Ospedaliera dei Colli) Viale Colli Aminei, 21
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80141 Naples, Italy Phone: +393337007873
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E- mail: [email protected]
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Highlights
More severe hypoxemia, oxyhemoglobin hyposaturation and higher alveolar-arterial oxygen gradient are associated with the diagnosis of lung injury in patients with blunt chest trauma. The combination of different arterial blood gas analysis variables may be a fast approach to identify which patients with blunt chest trauma are at risk of having lung injury and so which patients are likely to benefit from chest CT scan.
Abstract
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Background: thoracic trauma is one of the leading causes of death in all age groups and accounts for 25–50% of all traumatic injuries. With the term lung injury in blunt chest trauma, we identified a spectrum of conditions: lung contusion, pneumothorax and haemothorax. The aim of this study was
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to evaluate the utility of arterial blood gas analysis parameters in predicting lung injury in blunt chest trauma.
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Methods: we included 51 patients presenting to the Emergency Department of “C.T.O.” Hospital in Naples (Italy) for blunt chest trauma. The patients were assigned to the Lung Injury Group or to the
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Non-Lung Injury Group basing on CT scan findings. For each patient, we calculated the alveolararterial oxygen gradient (AaDO2), the AaDO2 augmentation, the arterial partial pressure of oxygen
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deficit (PaO2 Deficit) and the ratio between arterial partial pressure of oxygen and fraction of inspired oxygen (P/F). Areas under the curve (AUC) and receiver operating characteristic (ROC) curve were
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used to compare the performance of each different test in relation to the detection of lung injury in
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blunt chest trauma.
Results: patients with lung injury had lower oxygen saturation, arterial partial pressure of oxygen, P/F and higher PaO2 Deficit, AaDO2, AaDO2 augmentation than patients without lung injury. PaO2 Deficit, AaDO2 and AaDO2 augmentation showed a good accuracy to predict lung injury in blunt chest trauma.
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Conclusion: our study demonstrates that the combination of different arterial blood gas analysis variables may be a fast approach for identifying patients with lung injury in the setting of blunt chest trauma in the Emergency Department.
Keywords: lung contusion, pneumothorax, haemothorax, alveolar-arterial oxygen gradient, hypoxemia, partial pressure of oxygen.
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Introduction
Trauma causes an estimated 10% of deaths worldwide and is the third common cause of death after malignancy and vascular disease (1). In 2016, there were 20,360 deaths among children and
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adolescents in the United States, more than 60% resulted from injury-related causes (2). Thoracic trauma is one of the leading causes of death in all age groups and accounts for 25–50% of all traumatic
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injuries (3). With the term lung injury (LI) in blunt chest trauma, we will identify a spectrum of
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conditions: lung contusion, pneumothorax and haemothorax. Lung contusion is an entity involving injury to the alveolocapillary membrane, without any tear or cut in the lung tissue. This results in
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accumulation of blood and other fluids within the lung tissue that interferes with gas exchange leading to hypoxemia (4). Lung contusion occurs in 25-35% of all blunt chest traumas and it is the most
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common type of lung injury in this setting (5). Pneumothorax is a leakage of gas from the air spaces of the lung parenchyma or tracheobronchial tree into the pleural space, it occurs in 15–38% of patients
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suffering from blunt chest trauma and is usually associated with rib fracture (6). Traumatic injuries to the thorax often result in the accumulation of blood within the pleural space (haemothorax) (7). Hemothorax following penetrating and non-penetrating trauma may be the result of cardiac, great vessel, pulmonary parenchymal or chest wall injury (8). Pulmonary contusion can be absent on the initial chest radiography, in 6 hours after injury 21% of contusions observed on chest computed tomography scan were not visualized on the initial chest radiography (9). In severely traumatized 3
patients, pneumothorax can be missed on the supine anterior-posterior chest radiography in up to 30% of patients (10). The initial chest radiography can show no evidence of hemothorax, furthermore chest computed tomography scan is superior to chest radiography in identifying an hemothorax (9). Nowadays little evidence exists on which patients are likely to benefit from chest computed tomography (CT) scan after blunt chest trauma. The current literature indicates to evaluate the mechanism of injury, patient history (including patient characteristics), physical examination, findings detected by radiography and ultrasonography of the chest (11). There are no studies about
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the utility of arterial blood gas analysis in predicting which trauma patients are at risk of having relevant chest injuries and so which patients are likely to benefit from chest CT scan. The purpose of this study is to evaluate the utility of arterial blood gas analysis parameters in predicting lung injury
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in blunt chest trauma.
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Material and Methods
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This observational study was conducted in the Emergency Department (ED) of “C.T.O.” hospital in Naples (Italy) from 23 April 2018 to 24 July 2019. Informed consent was obtained from each patient included in the study, our research satisfies the Helsinki criteria. We examined 51 patients admitted
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to the ED for blunt chest trauma. Patients with previous history of pulmonary diseases or heart failure were excluded. All patients received a diagnostic work-up including: patient history, clinical
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examination, an arterial blood gas analysis on room air, routine blood tests, ultrasound examination
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of chest and abdomen, chest radiography for ribs and parenchyma and a CT scan of the thorax performed during the assessment in the ED. For each patient we determined vital signs, number of ribs fractures detected by chest x-ray and CT scan, severity of the injury using the Injury Severity Score (ISS) (12) and pain intensity assessment using the 0 to 10 Numerical Rating Scale (NRS) (13). The ISS is used for the classification of multiple-trauma patients. Each injury is given up to 6 points and the score describes six regions of the body: external, limbs, abdomen, chest, face, head and neck. The calculation is made using the same codes assigned to each of the 2000 diagnoses included in the 4
AIS (Abbreviated Injury Scale), grouped according to the 6 regions of the body. The highest AIS points are taken into consideration, one for every region of the body. These are then squared and then the scores for the three most affected different anatomic regions are added. The sum total is the ISS score, which ranges from 1 to 75 (14). For each patient, as gas exchange index through the alveolocapillary membrane, we determined the alveolar-arterial oxygen gradient (AaDO2) and the alveolar-arterial oxygen gradient augmentation
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(AaDO2 augmentation). The alveolar-arterial oxygen gradient was calculated as follows (15): AaDO2 (mmHg)=150-1.25PaCO2-PaO2,
where PaCO2 is the partial pressure of carbon dioxide in arterial blood (mmHg) and PaO2 is the partial
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pressure of oxygen in arterial blood (mmHg). Measurements of arterial blood gases were obtained while the patient breathed room air. The estimated normal gradient (mmHg) was calculated as follows
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(16):
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(Age/4) + 4.
We did not directly calculate the alveolar PO2 but considering the alveolar gas equation
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PAO2=FiO2*(Pbar-PH2O)-PCO2*(FiO2+(1-FiO2)/RER) (17) we can obtain the following equation:
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PAO2=PiO2-PACO2/RER (18)
Where PAO2 is the alveolar PO2, FiO2 is the inspired oxygen fraction, Pbar is the barometric pressure,
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PH2O is the saturated vapour pressure of water at body temperature (47 mmHg at 37°C), RER is the respiratory exchange ratio VCO2 (carbon dioxide output)/VO2(oxygen consumption) and its value is around 0.8, PiO2 is the partial pressure of oxygen in inspired gas reaching the alveoli (at sea level and on room air the PiO2 is approximately 150 mm Hg), PACO2 is the alveolar partial pressure of carbon dioxide. Taking into account that the CO2 is easily diffusible the PACO2 in our equation can be replaced by PaCO2. Our equation becomes PAO2=150- PaCO2/0.8, moreover PaCO2/0.8 can be 5
replaced by PaCO2*1.25. In conclusion, the AaDO2 can be calculated with the equation: AaDO2= PAO2-PaO2= 150-1.25PaCO2-PaO2. When breathing air, the AaDO2 provides a sensitive measure of gas exchange efficiency but is dependent on age. A number of different studies have sampled relatively small numbers of individuals in different populations to determine the distribution of the AaDO2 in normal individuals. In all studies, the mean AaDO2 increases with age, as do the confidence intervals around the mean. A
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simplified formula for the normal AaDO2 when breathing air is (Age in years/4)+4 mmHg (18). The alveolar-arterial oxygen gradient augmentation was calculated as follows: AaDO2 augmentation (mmHg)= AaDO2-estimated normal gradient.
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For each patient, as measurement of hypoxemia (19), we determined oxygen saturation, PaO2, PaO2
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Deficit, P/F and the arterial/alveolar oxygen tension ratio (a‑ A oxygen tension ratio). PaO2 decreases with age, this is in part due to an increase in the alveolar-arterial oxygen partial pressure difference
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with age. This has been attributed to increased ventilation-perfusion disturbances as a consequence of changes in closing volume with advancing years (20). Owing to the natural decline in normal
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arterial oxygen levels with age, the estimated normal PaO2 (mmHg) was calculated as follows (21)
100- Age/3.
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(22):
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The PaO2 Deficit was calculated as follows: PaO2 Deficit (mmHg) =estimated normal PaO2-arterial blood gas analysis PaO2. The P/F was calculated as the ratio between arterial partial pressure of oxygen by blood gas analysis (in mmHg) and fraction of inspired oxygen. The PaO2/FiO2 ratio assesses the hypoxemia at different levels of FiO2 but the PaO2/FiO2 ratio has some limitations, in fact while the alveolar-arterial oxygen gradient can differentiate whether hypoxemia is due to alveolar hypoventilation or ventilation6
perfusion mismatch, the PaO2/FiO2 ratio is unable to determine the underlying mechanism of hypoxemia (19). The arterial/alveolar oxygen tension ratio (a‑ A oxygen tension ratio) was calculated as the ratio between PaO2 and PAO2 (23), the normal ratio varies between 0.75 and 1.0. Based on CT scan findings, considered as the gold standard, the 51 patients were assigned to the Lung Injury Group (LIG) in presence of lung injury (42 patients) or to the Non-Lung Injury Group (NLIG)
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in absence of lung injury (9 patients). Data were analyzed using SPSS version 21.0 (SPSS, Chicago, Illinois, USA). Continuous data are expressed as mean ± 1 standard deviation and categorical variables as percentages. Quantitative
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variables were compared by using Student’s t-test while chi-square distribution was used to compare categorical variables. A p-value <0.05 was considered statistically significant. Areas under the curve
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(AUC) and receiver operating characteristic (ROC) curve were used to compare the performance of
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each different test in relation to the detection of lung injury in blunt chest trauma. The performance of chest x-ray, to detect rib fractures and lung injury, was analyzed and compared to the gold standard (chest computed tomography scan) using sensitivity, specificity, positive predictive value, negative
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predictive value and the accuracy defined by the proportion of true results. Confidence intervals (CI)
value.
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Results
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at 95% were calculated for sensitivity, specificity, positive predictive value, and negative predictive
Our study population included 51 patients (30 males) with a mean age of 61 years. The cause of injury was: fall-related injury in 33 patients (64,7%), motor vehicle crash in 14 patients (27,5%), bike crash in 2 patients (3,9%), pedestrian struck by vehicle in 1 patient (2%) and kicks in 1 patient (2%). Lung contusion was detected in 16 patients (31,4%), haemothorax in 10 patients (19,6%), pneumothorax in 2 patients (3,9%), the combination of these lung injuries in 14 patients (27,5%) and absence of 7
lung injury in 9 patients (17,6%). The baseline characteristics of the two subgroups based on the presence/absence of lung injury are detailed in table 1. Patients with lung injury had lower oxygen saturation, PaO2, P/F, a‑ A oxygen tension ratio, heart rate and higher PaO2 Deficit, AaDO2, AaDO2 augmentation, ISS and number of ribs fractures detected by chest x-ray and CT scan, than patients without lung injury (table 1, all p<0,05). The receiver operating characteristic curve (figure 1) demonstrates that the number of ribs fractures detected by chest x-ray and CT scan, PaO2 Deficit, AaDO2, AaDO2 augmentation and ISS are useful
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in predicting lung injury in blunt chest trauma, while testing PaO2, Oxygen saturation, P/F and a‑ A oxygen tension ratio to evaluate the ability of each one to predict lung injury, they showed an AUC of 0,123-0,089-0,123-0,176 respectively. Table 2 shows the performance of chest x-ray, to detect rib
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fractures and lung injury, compared to the gold standard (chest computed tomography scan).
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Discussion
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Hypoxemia is defined as a decrease in the partial pressure of oxygen in the blood and it can be due to various mechanisms: ventilation/perfusion mismatch, right-to-left shunt, diffusion impairment, hypoventilation and low inspired PO2 (19). Patients with pulmonary contusion manifest hypoxemia
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due to inflammation, increased alveolo-capillary permeability, ventilation/perfusion mismatching, increased intrapulmonary shunting and a loss of compliance (4). Hemothorax related to trauma can
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be due to rib fractures, causing bleeding from an intercostal vessel or associated pulmonary
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parenchymal injury as the source of the hemorrhage, more significant hemothoraces may be secondary to a major injury, such as an intrathoracic vascular structure (24). Pneumothorax related to blunt chest trauma can develop if the visceral pleura is lacerated subsequently to a rib fracture dislocation. Sudden chest compression abruptly increases the alveolar pressure causing alveolar rupture, consequently the air enters in the interstitial space dissecting toward either the visceral pleura or the mediastinum. A pneumothorax develops when the visceral or the mediastinal pleura ruptures, allowing air to enter into the pleural space (25). The main mechanisms of hypoxemia in 8
pneumothorax and hemothorax are the presence of intrapulmonary shunt and ventilation-perfusion imbalance (26). There are different measurement of hypoxemia (19) and among them, in our study, oxygen saturation, PaO2, P/F, PaO2 Deficit and a‑ A oxygen tension ratio showed a statistically significative difference between the two groups (all p<0,05), underlining the major grade of hypoxemia of the lung injury group. Furthermore, among the different measurement of hypoxemia, the PaO2 Deficit showed a good accuracy (AUC 0,828) to predict lung injury in blunt chest trauma. Also the heart rate showed a statistically significative difference between the two groups (p<0,05),
number of patients treated with beta blockers for hypertension.
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probably the lung injury group had lower heart rate than patients without lung injury due to a major
The AaDO2 indicates the integrity of the alveolocapillary membrane and is used as an index of gas
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exchange, the factors influencing it are diffusion gradient, ventilation-perfusion imbalance and true
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shunt (15). In our study, patients with lung injury had higher AaDO2 and AaDO2 augmentation than patients without lung injury (all p<0,05) underlining alveolocapillary membrane damage and the
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consequent worsening of gas exchange in the lung injury group. Furthermore, AaDO2 and AaDO2 augmentation showed a good accuracy (AUC 0,839-0,808 respectively) to predict lung injury in blunt
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chest trauma.
We tested the ability of various parameters to predict lung injury, everyone showes advantages and
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disadvantages. The PaO2 can be used as an index of patient oxygenation status, in fact this parameter is related to lung diffusion properties and perfusion, however it is not useful in some cases (anemia
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and decreased cardiac output). The P/F is frequently used in clinical practice to assess the severity of hypoxemia but it does not take into consideration the PaCO2, it is dependent on the FiO2 and it is not helpful in differentiating between different causes of hypoxaemia. The AaDO2 can differentiate whether hypoxemia is due to alveolar hypoventilation or ventilation/perfusion mismatch, but it is not useful when a patient breathes supplemental O2. The arterial/alveolar oxygen tension ratio provides a uniform guide to gas exchange function and it is relatively unaffected by FiO2. 9
We tested different variables (PaO2 Deficit, AaDO2, AaDO2 augmentation, PaO2, Oxygen saturation, P/F, a‑ A oxygen tension ratio, number of ribs fractures detected by chest x-ray and CT scan and the ISS) to evaluate the ability of each one to predict lung injury in blunt chest trauma. Although the ISS was the best variable in the prediction showing an excellent accuracy (AUC 0,935), each one of the three tested blood gas analysis variables (PaO2 Deficit, AaDO2, AaDO2 augmentation) showed a good accuracy (AUC 0,828-0,839-0,808 respectively) equal to the variable number of ribs fractures detected by CT scan (AUC 0,835). Considering that the Injury Severity Score is a retrospective index
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of anatomical injury used to estimate the probability of survival (27), it is not useful as tool to predict lung injury in blunt chest trauma at patient presentation to the ED. On the other hand, also the variable number of ribs fractures detected by CT scan is non instantaneously avaible while the arterial blood
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gas analysis is readily obtainable in patients presenting to the ED for blunt chest trauma. In our study, chest x-ray compared to the gold standard CT scan shows excellent specificity (100%) but low
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sensitivity (56,25%) in the detection of lung injury, confirming previous findings (28). Furthermore,
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in accordance with prior reports (6), not all rib fractures are identified on the initial chest radiograph (Accuracy 59%). While PaO2 Deficit, AaDO2 and AaDO2 augmentation showed a good accuracy to predict lung injury, PaO2, Oxygen saturation, P/F and a‑ A oxygen tension ratio showed a fail
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accuracy underlining that the age-related blood gas analysis variables (PaO2 Deficit, AaDO2, AaDO2 augmentation) have a better prediction capacity than the standard gas analysis variables (PaO2,
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Oxygen saturation, P/F and a‑ A oxygen tension ratio).
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Our study demonstrates that the combination of different arterial blood gas analysis variables may be a fast approach to identify which patients with blunt chest trauma are at risk of having lung injury and so which patients are likely to benefit from chest CT scan. Our study has some limitations. First, the population sample could be larger. In particular, to avoid the excessive unnecessary exposition of the patients to CT scans radiation, the group of patients without lung injury is very small. Also, probably, our arterial blood gas analysis approach is not 10
applicable in patients with previous history of pulmonary diseases or heart failure, in fact they were excluded from the study. Conclusion More severe hypoxemia, oxyhemoglobin hyposaturation and higher alveolar-arterial oxygen gradient are associated with the diagnosis of lung injury in patients with blunt chest trauma. Arterial blood gas analysis requires few minutes and has a reliable diagnostic ability to identify patients with lung injury
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in the setting of blunt chest trauma.
MVC and AS conceived the paper and wrote the manuscript. MG, AI, DC, MIA and CM contributed to the
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discussion and edited the manuscript.
References
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1. Computed Tomography in Blunt Chest Trauma. Sarita Magu, Ashok Yadav and Shalini Agarwal. The Indian Journal of Chest Diseases & Allied Sciences. 2009;Vol.51, 75-81.
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2. The Major Causes of Death in Children and Adolescents in the United States. R. M. Cunningham, M. A. Walton, P. M. Carter. N Engl J Med. 2018 Dec 20;379(25):2468-2475.
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3. Emergency thoracotomy in thoracic trauma—a review. P.A. Hunt, I. Greaves, W.A. Owens. Injury. 2006 Jan;37(1):1-19. 4. Lung Contusion: A Clinico-Pathological Entity with Unpredictable Clinical Course. Farooq Ahmad Ganie, Hafeezulla Lone, Ghulam Nabi Lone, Mohd Lateef Wani, Shyam Singh, Abdual Majeed Dar, Nasir-u-din Wani, Shadab nabi wani, Nadeem-ul Nazeer. Bull Emerg Trauma. 2013 Jan;1(1):7-16. 5. Traumatic injuries: Imaging of thoracic injuries. Gavelli G, Canini R, Bertaccini P, Battista G, Bnà C, Fattori R. Eur Radiol 2002;12(6):1273-94. 6. Spectrum of Blunt Chest Injuries. Nisa Thoongsuwan, Jeffrey P. Kanne, and Eric J. Stern. J Thorac Imaging. Volume 20, Number 2, May 2005. 11
7. Management of haemothoraces in blunt thoracic trauma: study protocol for a randomised controlled trial. David A Carver, Alexsander K Bressan, Colin Schieman, Sean C Grondin, Andrew W Kirkpatrick, Rohan Lall, Paul B McBeth, Michael B Dunham, Chad G Ball. BMJ Open 2018;8:e020378. . 8. Acute Traumatic Hemothorax. Symbas PN. Ann Thorac Surg. 1978 Sep;26(3):195-6. 9. Imaging of chest trauma: radiological patterns of injury and diagnostic algorithms. Fritz M. Lomoschitz, Edith Eisenhuber, Ken F. Linnau, Philipp Peloschek, Maria Schoder, Alexander A. Bankier. European Journal of Radiology 48 (2003) 61-70. 10. Distribution of pneumothorax in the supine and semirecumbent critically ill adult. Tocino IM, Miller MH, Fairfax WR. Am J Roentgenol 1985;144(5):901-5.
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11. Predictors of abnormal chest CT after blunt trauma: a critical appraisal of the literature. Brink M, Kool DR, Dekker HM, Deunk J, Jager GJ, van Kuijk C, Edwards MJ, Blickman JG. Clin Radiol. 2009 Mar;64(3):27283. 12. The injury severity score: an update. Baker SP and O’Neill B. J Trauma. 1976; 16: 882–885.
13. Pain assessment. Haefeli M, Elfering A. Eur Spine J. 2006 Jan;15 Suppl 1:S17-24. Epub 2005 Dec 1.
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14. Review Trauma severity scores. C A Restrepo-Álvarez, C O Valderrama-Molina, N Giraldo-Ramírez, A Constain-Franco, A Puerta, A L León, F Jaimes. Rev colomb anestesiol. 2016;44(4):317–323.
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15. Prognostic role of alveolar-arterial oxygen pressure difference in acute pulmonary embolism. Hsu JT, Chu CM, Chang ST, Cheng HW, Cheng NJ, Ho WC, Chung CM. Circ J. 2006 Dec;70(12):1611-6.
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16. Use of the alveolar-arterial oxygen gradient in the diagnosis of pulmonary embolism. McFarlane MJ, Imperiale TF. Am J Med. 1994 Jan;96(1):57-62.
na
17. A theoretical study of the composition of the alveolar air at altitude. FENN WO, RAHN H, OTIS AB. Am J Physiol. 1946 Aug;146:637-53. 18. Gas exchange and ventilation-perfusion relationships in the lung. Petersson J, Glenny RW. Eur Respir J. 2014 Oct;44(4):1023-41.
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19. Mechanisms of hypoxemia. M Sarkar, N Niranjan and PK Banyal. Lung India. 2017 Jan-Feb; 34(1): 47– 60.
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20. Analysis of possible factors influencing PaO2 and (PaO2--PaO2) in patients awaiting operation. Gillies ID, Petrie A, Morgan M, Sykes MK. Br J Anaesth. 1977 May;49(5):427-37. 21. F. Schiraldi, G. Guiotto. Equilibrio acido-base Ossigeno Fluidi & elettroliti. 2012 McGraw-Hill. 22. BTS guideline for emergency oxygen use in adult patients. O'Driscoll BR, Howard LS, Davison AG and Society., British Thoracic. Thorax. 2008 Oct;63 Suppl 6:vi1-68. 23. The arterial-alveolar oxygen tension ratio. An index of gas exchange applicable to varying inspired oxygen concentrations. Gilbert R, Keighley JF. Am Rev Respir Dis. 1974 Jan;109(1):142-5. 24. Hemothorax related to trauma. DM Meyer. Thorac Surg Clin. 2007 Feb;17(1):47-55. 12
25. Principles of diagnosis and management of traumatic pneumothorax. A Sharma and P Jindal. J Emerg Trauma Shock. 2008 Jan-Jun; 1(1): 34–41. 26. Pneumothorax. WI Choi. Tuberc Respir Dis (Seoul). 2014 Mar;76(3):99-104. 27. Injury Severity Score (ISS) vs. ICD-derived Injury Severity Score (ICISS) in a patient population treated in a designated Hong Kong trauma centre. Wong SS, Leung GK. Mcgill J Med. 2008 Jan;11(1):9-13.
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28. The use of chest computed tomography versus chest X-ray in patients with major blunt trauma. Traub M, Stevenson M, McEvoy S, Briggs G, Lo SK, Leibman S, Joseph T. Injury. 2007 Jan;38(1):43-7.
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Figures and tables captions Figure 1. Receiver operating characteristic (ROC) curve comparing accuracy of different test in
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relation to the detection of lung injury in blunt chest trauma.
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Table 1. Baseline characteristics of the two subgroups based on the presence/absence of lung injury.
LIG (n=42) 62,88±19,73 40,48% 137,58±17,91 80,63±13,5 79,21±15,49 18,63±2,12
NLIG (n=9) 53,11±20,29 44,44% 146,67±12,50 86,67±11,18 90,44±9,24 18,71±3,77
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Age (years) 0,186 Sex (female) 0,830 Systolic BP (mm Hg) 0,156 Diastolic BP (mm Hg) 0,219 Heart rate (bpm) 0,043 Respiratory rate 0,936 (breaths/min) Oxygen saturation (%) 94,62±4,18 98,11±0,78 0,017 0 to 10 NRS 7,14±1,65 7,25±1,58 0,868 Number of ribs 2,88±2,03 1,14±1,47 0,04 fractures detected by chest x-ray Number of ribs 3,67±1,87 1,33±1,23 0,001 fractures detected by CT scan PaO2 (mmHg) 64,45±11,46 78,78±8,01 0,001 PaO2/FiO2 306,92±54,59 375,17±38,23 0,001 Arterial/alveolar 0,64±0,11 0,77±0,09 0,001 oxygen tension ratio PaO2 Deficit (mmHg) 14,59±11,32 3,52±10,85 0,01 pH 7,43±0,04 7,44±0,03 0,372 AaDO2 (mmHg) 36,92±11,64 24,00±9,99 0,003 AaDO2 augmentation 17,16±11,31 7,94±9,87 0,028 (mmHg) Lactate level 1,29±0,88 1,00±0,41 0,365 (mmol/L) ISS 16,43±6,98 6,67±2,78 0,000 LIG = Lung Injury Group; NLIG = Non-Lung Injury Group; BP = blood pressure; NRS = Numerical Rating Scale; CT scan = computed tomography scan; PaO2 = partial pressure of oxygen in arterial blood; AaDO2 = alveolar-arterial oxygen gradient; ISS = Injury Severity Score.
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Table 2. Sensitivity, specificity, positive and negative predictive value and accuracy of chest x-ray in the diagnosis of rib fractures and lung injury. Sensitivity (%) (95% CI) 55,56% (38-72)
Specificity (%) (95% CI) 100% (31-100)
PPV (%) (95% CI)
NPV (%) (95% CI)
Accuracy (%)
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Performance of 100% 15,79% 59% chest x-ray to (80-100) (4-40) detect rib fractures Performance of 56,25% 100% 100% 33,33% 64,1% chest x-ray to (38-73) (56-100) (78-100) (16-57) detect lung injury PPV = positive predictive value; NPV = negative predictive value; CI = confidence interval.
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PII:
S1569-9048(19)30308-8
DOI:
https://doi.org/10.1016/j.resp.2019.103363
Reference:
RESPNB 103363
To appear in:
Respiratory Physiology & Neurobiology
Received Date:
23 August 2019
Revised Date:
15 November 2019
Accepted Date:
19 December 2019
Please cite this article as: Carlino MV, Guarino M, Izzo A, Carbone D, Arnone MI, Mancusi C, Sforza A, Arterial blood gas analysis utility in predicting lung injury in blunt chest trauma, Respiratory Physiology and amp; Neurobiology (2019), doi: https://doi.org/10.1016/j.resp.2019.103363
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Arterial blood gas analysis utility in predicting lung injury in blunt chest trauma Maria Viviana Carlino1 MD, Mario Guarino1 MD, Arturo Izzo1 MD, Daniele Carbone1 RN, Maria Immacolata Arnone1-2 MD, Costantino Mancusi2 MD, Alfonso Sforza1 MD.
1. Emergency Department, C. T. O. Hospital, Naples. 2. Federico II University Hospital, Naples.
Financial/nonfinancial disclosures: None declared.
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Declarations of interest: none. Correspondence to: Dr. Maria Viviana Carlino
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Ospedale C.T.O. (Azienda Ospedaliera dei Colli) Viale Colli Aminei, 21
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80141 Naples, Italy Phone: +393337007873
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E- mail: [email protected]
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Highlights
More severe hypoxemia, oxyhemoglobin hyposaturation and higher alveolar-arterial oxygen gradient are associated with the diagnosis of lung injury in patients with blunt chest trauma. The combination of different arterial blood gas analysis variables may be a fast approach to identify which patients with blunt chest trauma are at risk of having lung injury and so which patients are likely to benefit from chest CT scan.
Abstract
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Background: thoracic trauma is one of the leading causes of death in all age groups and accounts for 25–50% of all traumatic injuries. With the term lung injury in blunt chest trauma, we identified a spectrum of conditions: lung contusion, pneumothorax and haemothorax. The aim of this study was
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to evaluate the utility of arterial blood gas analysis parameters in predicting lung injury in blunt chest trauma.
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Methods: we included 51 patients presenting to the Emergency Department of “C.T.O.” Hospital in Naples (Italy) for blunt chest trauma. The patients were assigned to the Lung Injury Group or to the
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Non-Lung Injury Group basing on CT scan findings. For each patient, we calculated the alveolararterial oxygen gradient (AaDO2), the AaDO2 augmentation, the arterial partial pressure of oxygen
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deficit (PaO2 Deficit) and the ratio between arterial partial pressure of oxygen and fraction of inspired oxygen (P/F). Areas under the curve (AUC) and receiver operating characteristic (ROC) curve were
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used to compare the performance of each different test in relation to the detection of lung injury in
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blunt chest trauma.
Results: patients with lung injury had lower oxygen saturation, arterial partial pressure of oxygen, P/F and higher PaO2 Deficit, AaDO2, AaDO2 augmentation than patients without lung injury. PaO2 Deficit, AaDO2 and AaDO2 augmentation showed a good accuracy to predict lung injury in blunt chest trauma.
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Conclusion: our study demonstrates that the combination of different arterial blood gas analysis variables may be a fast approach for identifying patients with lung injury in the setting of blunt chest trauma in the Emergency Department.
Keywords: lung contusion, pneumothorax, haemothorax, alveolar-arterial oxygen gradient, hypoxemia, partial pressure of oxygen.
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Introduction
Trauma causes an estimated 10% of deaths worldwide and is the third common cause of death after malignancy and vascular disease (1). In 2016, there were 20,360 deaths among children and
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adolescents in the United States, more than 60% resulted from injury-related causes (2). Thoracic trauma is one of the leading causes of death in all age groups and accounts for 25–50% of all traumatic
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injuries (3). With the term lung injury (LI) in blunt chest trauma, we will identify a spectrum of
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conditions: lung contusion, pneumothorax and haemothorax. Lung contusion is an entity involving injury to the alveolocapillary membrane, without any tear or cut in the lung tissue. This results in
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accumulation of blood and other fluids within the lung tissue that interferes with gas exchange leading to hypoxemia (4). Lung contusion occurs in 25-35% of all blunt chest traumas and it is the most
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common type of lung injury in this setting (5). Pneumothorax is a leakage of gas from the air spaces of the lung parenchyma or tracheobronchial tree into the pleural space, it occurs in 15–38% of patients
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suffering from blunt chest trauma and is usually associated with rib fracture (6). Traumatic injuries to the thorax often result in the accumulation of blood within the pleural space (haemothorax) (7). Hemothorax following penetrating and non-penetrating trauma may be the result of cardiac, great vessel, pulmonary parenchymal or chest wall injury (8). Pulmonary contusion can be absent on the initial chest radiography, in 6 hours after injury 21% of contusions observed on chest computed tomography scan were not visualized on the initial chest radiography (9). In severely traumatized 3
patients, pneumothorax can be missed on the supine anterior-posterior chest radiography in up to 30% of patients (10). The initial chest radiography can show no evidence of hemothorax, furthermore chest computed tomography scan is superior to chest radiography in identifying an hemothorax (9). Nowadays little evidence exists on which patients are likely to benefit from chest computed tomography (CT) scan after blunt chest trauma. The current literature indicates to evaluate the mechanism of injury, patient history (including patient characteristics), physical examination, findings detected by radiography and ultrasonography of the chest (11). There are no studies about
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the utility of arterial blood gas analysis in predicting which trauma patients are at risk of having relevant chest injuries and so which patients are likely to benefit from chest CT scan. The purpose of this study is to evaluate the utility of arterial blood gas analysis parameters in predicting lung injury
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in blunt chest trauma.
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Material and Methods
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This observational study was conducted in the Emergency Department (ED) of “C.T.O.” hospital in Naples (Italy) from 23 April 2018 to 24 July 2019. Informed consent was obtained from each patient included in the study, our research satisfies the Helsinki criteria. We examined 51 patients admitted
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to the ED for blunt chest trauma. Patients with previous history of pulmonary diseases or heart failure were excluded. All patients received a diagnostic work-up including: patient history, clinical
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examination, an arterial blood gas analysis on room air, routine blood tests, ultrasound examination
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of chest and abdomen, chest radiography for ribs and parenchyma and a CT scan of the thorax performed during the assessment in the ED. For each patient we determined vital signs, number of ribs fractures detected by chest x-ray and CT scan, severity of the injury using the Injury Severity Score (ISS) (12) and pain intensity assessment using the 0 to 10 Numerical Rating Scale (NRS) (13). The ISS is used for the classification of multiple-trauma patients. Each injury is given up to 6 points and the score describes six regions of the body: external, limbs, abdomen, chest, face, head and neck. The calculation is made using the same codes assigned to each of the 2000 diagnoses included in the 4
AIS (Abbreviated Injury Scale), grouped according to the 6 regions of the body. The highest AIS points are taken into consideration, one for every region of the body. These are then squared and then the scores for the three most affected different anatomic regions are added. The sum total is the ISS score, which ranges from 1 to 75 (14). For each patient, as gas exchange index through the alveolocapillary membrane, we determined the alveolar-arterial oxygen gradient (AaDO2) and the alveolar-arterial oxygen gradient augmentation
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(AaDO2 augmentation). The alveolar-arterial oxygen gradient was calculated as follows (15): AaDO2 (mmHg)=150-1.25PaCO2-PaO2,
where PaCO2 is the partial pressure of carbon dioxide in arterial blood (mmHg) and PaO2 is the partial
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pressure of oxygen in arterial blood (mmHg). Measurements of arterial blood gases were obtained while the patient breathed room air. The estimated normal gradient (mmHg) was calculated as follows
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(16):
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(Age/4) + 4.
We did not directly calculate the alveolar PO2 but considering the alveolar gas equation
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PAO2=FiO2*(Pbar-PH2O)-PCO2*(FiO2+(1-FiO2)/RER) (17) we can obtain the following equation:
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PAO2=PiO2-PACO2/RER (18)
Where PAO2 is the alveolar PO2, FiO2 is the inspired oxygen fraction, Pbar is the barometric pressure,
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PH2O is the saturated vapour pressure of water at body temperature (47 mmHg at 37°C), RER is the respiratory exchange ratio VCO2 (carbon dioxide output)/VO2(oxygen consumption) and its value is around 0.8, PiO2 is the partial pressure of oxygen in inspired gas reaching the alveoli (at sea level and on room air the PiO2 is approximately 150 mm Hg), PACO2 is the alveolar partial pressure of carbon dioxide. Taking into account that the CO2 is easily diffusible the PACO2 in our equation can be replaced by PaCO2. Our equation becomes PAO2=150- PaCO2/0.8, moreover PaCO2/0.8 can be 5
replaced by PaCO2*1.25. In conclusion, the AaDO2 can be calculated with the equation: AaDO2= PAO2-PaO2= 150-1.25PaCO2-PaO2. When breathing air, the AaDO2 provides a sensitive measure of gas exchange efficiency but is dependent on age. A number of different studies have sampled relatively small numbers of individuals in different populations to determine the distribution of the AaDO2 in normal individuals. In all studies, the mean AaDO2 increases with age, as do the confidence intervals around the mean. A
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simplified formula for the normal AaDO2 when breathing air is (Age in years/4)+4 mmHg (18). The alveolar-arterial oxygen gradient augmentation was calculated as follows: AaDO2 augmentation (mmHg)= AaDO2-estimated normal gradient.
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For each patient, as measurement of hypoxemia (19), we determined oxygen saturation, PaO2, PaO2
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Deficit, P/F and the arterial/alveolar oxygen tension ratio (a‑ A oxygen tension ratio). PaO2 decreases with age, this is in part due to an increase in the alveolar-arterial oxygen partial pressure difference
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with age. This has been attributed to increased ventilation-perfusion disturbances as a consequence of changes in closing volume with advancing years (20). Owing to the natural decline in normal
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arterial oxygen levels with age, the estimated normal PaO2 (mmHg) was calculated as follows (21)
100- Age/3.
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(22):
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The PaO2 Deficit was calculated as follows: PaO2 Deficit (mmHg) =estimated normal PaO2-arterial blood gas analysis PaO2. The P/F was calculated as the ratio between arterial partial pressure of oxygen by blood gas analysis (in mmHg) and fraction of inspired oxygen. The PaO2/FiO2 ratio assesses the hypoxemia at different levels of FiO2 but the PaO2/FiO2 ratio has some limitations, in fact while the alveolar-arterial oxygen gradient can differentiate whether hypoxemia is due to alveolar hypoventilation or ventilation6
perfusion mismatch, the PaO2/FiO2 ratio is unable to determine the underlying mechanism of hypoxemia (19). The arterial/alveolar oxygen tension ratio (a‑ A oxygen tension ratio) was calculated as the ratio between PaO2 and PAO2 (23), the normal ratio varies between 0.75 and 1.0. Based on CT scan findings, considered as the gold standard, the 51 patients were assigned to the Lung Injury Group (LIG) in presence of lung injury (42 patients) or to the Non-Lung Injury Group (NLIG)
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in absence of lung injury (9 patients). Data were analyzed using SPSS version 21.0 (SPSS, Chicago, Illinois, USA). Continuous data are expressed as mean ± 1 standard deviation and categorical variables as percentages. Quantitative
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variables were compared by using Student’s t-test while chi-square distribution was used to compare categorical variables. A p-value <0.05 was considered statistically significant. Areas under the curve
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(AUC) and receiver operating characteristic (ROC) curve were used to compare the performance of
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each different test in relation to the detection of lung injury in blunt chest trauma. The performance of chest x-ray, to detect rib fractures and lung injury, was analyzed and compared to the gold standard (chest computed tomography scan) using sensitivity, specificity, positive predictive value, negative
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predictive value and the accuracy defined by the proportion of true results. Confidence intervals (CI)
value.
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Results
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at 95% were calculated for sensitivity, specificity, positive predictive value, and negative predictive
Our study population included 51 patients (30 males) with a mean age of 61 years. The cause of injury was: fall-related injury in 33 patients (64,7%), motor vehicle crash in 14 patients (27,5%), bike crash in 2 patients (3,9%), pedestrian struck by vehicle in 1 patient (2%) and kicks in 1 patient (2%). Lung contusion was detected in 16 patients (31,4%), haemothorax in 10 patients (19,6%), pneumothorax in 2 patients (3,9%), the combination of these lung injuries in 14 patients (27,5%) and absence of 7
lung injury in 9 patients (17,6%). The baseline characteristics of the two subgroups based on the presence/absence of lung injury are detailed in table 1. Patients with lung injury had lower oxygen saturation, PaO2, P/F, a‑ A oxygen tension ratio, heart rate and higher PaO2 Deficit, AaDO2, AaDO2 augmentation, ISS and number of ribs fractures detected by chest x-ray and CT scan, than patients without lung injury (table 1, all p<0,05). The receiver operating characteristic curve (figure 1) demonstrates that the number of ribs fractures detected by chest x-ray and CT scan, PaO2 Deficit, AaDO2, AaDO2 augmentation and ISS are useful
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in predicting lung injury in blunt chest trauma, while testing PaO2, Oxygen saturation, P/F and a‑ A oxygen tension ratio to evaluate the ability of each one to predict lung injury, they showed an AUC of 0,123-0,089-0,123-0,176 respectively. Table 2 shows the performance of chest x-ray, to detect rib
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fractures and lung injury, compared to the gold standard (chest computed tomography scan).
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Discussion
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Hypoxemia is defined as a decrease in the partial pressure of oxygen in the blood and it can be due to various mechanisms: ventilation/perfusion mismatch, right-to-left shunt, diffusion impairment, hypoventilation and low inspired PO2 (19). Patients with pulmonary contusion manifest hypoxemia
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due to inflammation, increased alveolo-capillary permeability, ventilation/perfusion mismatching, increased intrapulmonary shunting and a loss of compliance (4). Hemothorax related to trauma can
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be due to rib fractures, causing bleeding from an intercostal vessel or associated pulmonary
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parenchymal injury as the source of the hemorrhage, more significant hemothoraces may be secondary to a major injury, such as an intrathoracic vascular structure (24). Pneumothorax related to blunt chest trauma can develop if the visceral pleura is lacerated subsequently to a rib fracture dislocation. Sudden chest compression abruptly increases the alveolar pressure causing alveolar rupture, consequently the air enters in the interstitial space dissecting toward either the visceral pleura or the mediastinum. A pneumothorax develops when the visceral or the mediastinal pleura ruptures, allowing air to enter into the pleural space (25). The main mechanisms of hypoxemia in 8
pneumothorax and hemothorax are the presence of intrapulmonary shunt and ventilation-perfusion imbalance (26). There are different measurement of hypoxemia (19) and among them, in our study, oxygen saturation, PaO2, P/F, PaO2 Deficit and a‑ A oxygen tension ratio showed a statistically significative difference between the two groups (all p<0,05), underlining the major grade of hypoxemia of the lung injury group. Furthermore, among the different measurement of hypoxemia, the PaO2 Deficit showed a good accuracy (AUC 0,828) to predict lung injury in blunt chest trauma. Also the heart rate showed a statistically significative difference between the two groups (p<0,05),
number of patients treated with beta blockers for hypertension.
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probably the lung injury group had lower heart rate than patients without lung injury due to a major
The AaDO2 indicates the integrity of the alveolocapillary membrane and is used as an index of gas
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exchange, the factors influencing it are diffusion gradient, ventilation-perfusion imbalance and true
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shunt (15). In our study, patients with lung injury had higher AaDO2 and AaDO2 augmentation than patients without lung injury (all p<0,05) underlining alveolocapillary membrane damage and the
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consequent worsening of gas exchange in the lung injury group. Furthermore, AaDO2 and AaDO2 augmentation showed a good accuracy (AUC 0,839-0,808 respectively) to predict lung injury in blunt
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chest trauma.
We tested the ability of various parameters to predict lung injury, everyone showes advantages and
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disadvantages. The PaO2 can be used as an index of patient oxygenation status, in fact this parameter is related to lung diffusion properties and perfusion, however it is not useful in some cases (anemia
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and decreased cardiac output). The P/F is frequently used in clinical practice to assess the severity of hypoxemia but it does not take into consideration the PaCO2, it is dependent on the FiO2 and it is not helpful in differentiating between different causes of hypoxaemia. The AaDO2 can differentiate whether hypoxemia is due to alveolar hypoventilation or ventilation/perfusion mismatch, but it is not useful when a patient breathes supplemental O2. The arterial/alveolar oxygen tension ratio provides a uniform guide to gas exchange function and it is relatively unaffected by FiO2. 9
We tested different variables (PaO2 Deficit, AaDO2, AaDO2 augmentation, PaO2, Oxygen saturation, P/F, a‑ A oxygen tension ratio, number of ribs fractures detected by chest x-ray and CT scan and the ISS) to evaluate the ability of each one to predict lung injury in blunt chest trauma. Although the ISS was the best variable in the prediction showing an excellent accuracy (AUC 0,935), each one of the three tested blood gas analysis variables (PaO2 Deficit, AaDO2, AaDO2 augmentation) showed a good accuracy (AUC 0,828-0,839-0,808 respectively) equal to the variable number of ribs fractures detected by CT scan (AUC 0,835). Considering that the Injury Severity Score is a retrospective index
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of anatomical injury used to estimate the probability of survival (27), it is not useful as tool to predict lung injury in blunt chest trauma at patient presentation to the ED. On the other hand, also the variable number of ribs fractures detected by CT scan is non instantaneously avaible while the arterial blood
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gas analysis is readily obtainable in patients presenting to the ED for blunt chest trauma. In our study, chest x-ray compared to the gold standard CT scan shows excellent specificity (100%) but low
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sensitivity (56,25%) in the detection of lung injury, confirming previous findings (28). Furthermore,
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in accordance with prior reports (6), not all rib fractures are identified on the initial chest radiograph (Accuracy 59%). While PaO2 Deficit, AaDO2 and AaDO2 augmentation showed a good accuracy to predict lung injury, PaO2, Oxygen saturation, P/F and a‑ A oxygen tension ratio showed a fail
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accuracy underlining that the age-related blood gas analysis variables (PaO2 Deficit, AaDO2, AaDO2 augmentation) have a better prediction capacity than the standard gas analysis variables (PaO2,
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Oxygen saturation, P/F and a‑ A oxygen tension ratio).
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Our study demonstrates that the combination of different arterial blood gas analysis variables may be a fast approach to identify which patients with blunt chest trauma are at risk of having lung injury and so which patients are likely to benefit from chest CT scan. Our study has some limitations. First, the population sample could be larger. In particular, to avoid the excessive unnecessary exposition of the patients to CT scans radiation, the group of patients without lung injury is very small. Also, probably, our arterial blood gas analysis approach is not 10
applicable in patients with previous history of pulmonary diseases or heart failure, in fact they were excluded from the study. Conclusion More severe hypoxemia, oxyhemoglobin hyposaturation and higher alveolar-arterial oxygen gradient are associated with the diagnosis of lung injury in patients with blunt chest trauma. Arterial blood gas analysis requires few minutes and has a reliable diagnostic ability to identify patients with lung injury
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in the setting of blunt chest trauma.
MVC and AS conceived the paper and wrote the manuscript. MG, AI, DC, MIA and CM contributed to the
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discussion and edited the manuscript.
References
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1. Computed Tomography in Blunt Chest Trauma. Sarita Magu, Ashok Yadav and Shalini Agarwal. The Indian Journal of Chest Diseases & Allied Sciences. 2009;Vol.51, 75-81.
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2. The Major Causes of Death in Children and Adolescents in the United States. R. M. Cunningham, M. A. Walton, P. M. Carter. N Engl J Med. 2018 Dec 20;379(25):2468-2475.
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3. Emergency thoracotomy in thoracic trauma—a review. P.A. Hunt, I. Greaves, W.A. Owens. Injury. 2006 Jan;37(1):1-19. 4. Lung Contusion: A Clinico-Pathological Entity with Unpredictable Clinical Course. Farooq Ahmad Ganie, Hafeezulla Lone, Ghulam Nabi Lone, Mohd Lateef Wani, Shyam Singh, Abdual Majeed Dar, Nasir-u-din Wani, Shadab nabi wani, Nadeem-ul Nazeer. Bull Emerg Trauma. 2013 Jan;1(1):7-16. 5. Traumatic injuries: Imaging of thoracic injuries. Gavelli G, Canini R, Bertaccini P, Battista G, Bnà C, Fattori R. Eur Radiol 2002;12(6):1273-94. 6. Spectrum of Blunt Chest Injuries. Nisa Thoongsuwan, Jeffrey P. Kanne, and Eric J. Stern. J Thorac Imaging. Volume 20, Number 2, May 2005. 11
7. Management of haemothoraces in blunt thoracic trauma: study protocol for a randomised controlled trial. David A Carver, Alexsander K Bressan, Colin Schieman, Sean C Grondin, Andrew W Kirkpatrick, Rohan Lall, Paul B McBeth, Michael B Dunham, Chad G Ball. BMJ Open 2018;8:e020378. . 8. Acute Traumatic Hemothorax. Symbas PN. Ann Thorac Surg. 1978 Sep;26(3):195-6. 9. Imaging of chest trauma: radiological patterns of injury and diagnostic algorithms. Fritz M. Lomoschitz, Edith Eisenhuber, Ken F. Linnau, Philipp Peloschek, Maria Schoder, Alexander A. Bankier. European Journal of Radiology 48 (2003) 61-70. 10. Distribution of pneumothorax in the supine and semirecumbent critically ill adult. Tocino IM, Miller MH, Fairfax WR. Am J Roentgenol 1985;144(5):901-5.
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11. Predictors of abnormal chest CT after blunt trauma: a critical appraisal of the literature. Brink M, Kool DR, Dekker HM, Deunk J, Jager GJ, van Kuijk C, Edwards MJ, Blickman JG. Clin Radiol. 2009 Mar;64(3):27283. 12. The injury severity score: an update. Baker SP and O’Neill B. J Trauma. 1976; 16: 882–885.
13. Pain assessment. Haefeli M, Elfering A. Eur Spine J. 2006 Jan;15 Suppl 1:S17-24. Epub 2005 Dec 1.
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14. Review Trauma severity scores. C A Restrepo-Álvarez, C O Valderrama-Molina, N Giraldo-Ramírez, A Constain-Franco, A Puerta, A L León, F Jaimes. Rev colomb anestesiol. 2016;44(4):317–323.
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15. Prognostic role of alveolar-arterial oxygen pressure difference in acute pulmonary embolism. Hsu JT, Chu CM, Chang ST, Cheng HW, Cheng NJ, Ho WC, Chung CM. Circ J. 2006 Dec;70(12):1611-6.
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16. Use of the alveolar-arterial oxygen gradient in the diagnosis of pulmonary embolism. McFarlane MJ, Imperiale TF. Am J Med. 1994 Jan;96(1):57-62.
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17. A theoretical study of the composition of the alveolar air at altitude. FENN WO, RAHN H, OTIS AB. Am J Physiol. 1946 Aug;146:637-53. 18. Gas exchange and ventilation-perfusion relationships in the lung. Petersson J, Glenny RW. Eur Respir J. 2014 Oct;44(4):1023-41.
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19. Mechanisms of hypoxemia. M Sarkar, N Niranjan and PK Banyal. Lung India. 2017 Jan-Feb; 34(1): 47– 60.
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20. Analysis of possible factors influencing PaO2 and (PaO2--PaO2) in patients awaiting operation. Gillies ID, Petrie A, Morgan M, Sykes MK. Br J Anaesth. 1977 May;49(5):427-37. 21. F. Schiraldi, G. Guiotto. Equilibrio acido-base Ossigeno Fluidi & elettroliti. 2012 McGraw-Hill. 22. BTS guideline for emergency oxygen use in adult patients. O'Driscoll BR, Howard LS, Davison AG and Society., British Thoracic. Thorax. 2008 Oct;63 Suppl 6:vi1-68. 23. The arterial-alveolar oxygen tension ratio. An index of gas exchange applicable to varying inspired oxygen concentrations. Gilbert R, Keighley JF. Am Rev Respir Dis. 1974 Jan;109(1):142-5. 24. Hemothorax related to trauma. DM Meyer. Thorac Surg Clin. 2007 Feb;17(1):47-55. 12
25. Principles of diagnosis and management of traumatic pneumothorax. A Sharma and P Jindal. J Emerg Trauma Shock. 2008 Jan-Jun; 1(1): 34–41. 26. Pneumothorax. WI Choi. Tuberc Respir Dis (Seoul). 2014 Mar;76(3):99-104. 27. Injury Severity Score (ISS) vs. ICD-derived Injury Severity Score (ICISS) in a patient population treated in a designated Hong Kong trauma centre. Wong SS, Leung GK. Mcgill J Med. 2008 Jan;11(1):9-13.
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28. The use of chest computed tomography versus chest X-ray in patients with major blunt trauma. Traub M, Stevenson M, McEvoy S, Briggs G, Lo SK, Leibman S, Joseph T. Injury. 2007 Jan;38(1):43-7.
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Figures and tables captions Figure 1. Receiver operating characteristic (ROC) curve comparing accuracy of different test in
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relation to the detection of lung injury in blunt chest trauma.
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Table 1. Baseline characteristics of the two subgroups based on the presence/absence of lung injury.
LIG (n=42) 62,88±19,73 40,48% 137,58±17,91 80,63±13,5 79,21±15,49 18,63±2,12
NLIG (n=9) 53,11±20,29 44,44% 146,67±12,50 86,67±11,18 90,44±9,24 18,71±3,77
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Age (years) 0,186 Sex (female) 0,830 Systolic BP (mm Hg) 0,156 Diastolic BP (mm Hg) 0,219 Heart rate (bpm) 0,043 Respiratory rate 0,936 (breaths/min) Oxygen saturation (%) 94,62±4,18 98,11±0,78 0,017 0 to 10 NRS 7,14±1,65 7,25±1,58 0,868 Number of ribs 2,88±2,03 1,14±1,47 0,04 fractures detected by chest x-ray Number of ribs 3,67±1,87 1,33±1,23 0,001 fractures detected by CT scan PaO2 (mmHg) 64,45±11,46 78,78±8,01 0,001 PaO2/FiO2 306,92±54,59 375,17±38,23 0,001 Arterial/alveolar 0,64±0,11 0,77±0,09 0,001 oxygen tension ratio PaO2 Deficit (mmHg) 14,59±11,32 3,52±10,85 0,01 pH 7,43±0,04 7,44±0,03 0,372 AaDO2 (mmHg) 36,92±11,64 24,00±9,99 0,003 AaDO2 augmentation 17,16±11,31 7,94±9,87 0,028 (mmHg) Lactate level 1,29±0,88 1,00±0,41 0,365 (mmol/L) ISS 16,43±6,98 6,67±2,78 0,000 LIG = Lung Injury Group; NLIG = Non-Lung Injury Group; BP = blood pressure; NRS = Numerical Rating Scale; CT scan = computed tomography scan; PaO2 = partial pressure of oxygen in arterial blood; AaDO2 = alveolar-arterial oxygen gradient; ISS = Injury Severity Score.
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Table 2. Sensitivity, specificity, positive and negative predictive value and accuracy of chest x-ray in the diagnosis of rib fractures and lung injury. Sensitivity (%) (95% CI) 55,56% (38-72)
Specificity (%) (95% CI) 100% (31-100)
PPV (%) (95% CI)
NPV (%) (95% CI)
Accuracy (%)
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Performance of 100% 15,79% 59% chest x-ray to (80-100) (4-40) detect rib fractures Performance of 56,25% 100% 100% 33,33% 64,1% chest x-ray to (38-73) (56-100) (78-100) (16-57) detect lung injury PPV = positive predictive value; NPV = negative predictive value; CI = confidence interval.
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