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The use of pulse oximetry to exclude pneumonia in children
The Use of Pulse Oximetry to Exclude Pneumonia in Children DAVID A. TANEN, MD AND DOUGLAS R. TROCINSKI, MD The objective of this study was to determine whether pulse oximetry alone or in conjunction with the clinical examination is predictive of pneumonia in children who present to the emergency department with respiratory complaints. A retrospective comparison of children with radiographic pneumonia with children with respiratory complaints and negative chest radiography was used. The study took place in an emergency department of a large academic, tertiary care hospital. All children less than 24 months of age who presented with a respiratory complaint and underwent chest radiography during a 1-year period were included. Charts of children with radiographic pneumonia were compared with charts of children without pneumonia, retrospectively. Data abstracted onto data collection forms included: pulse oximetry measurement, vital signs, general appearance, lung examination, and final radiology interpretation of chest radiographs. Pneumonia was defined as a chest radiograph showing any opacity consistent with pneumonia as read by a board-prepared or -certified radiologist. A total of 803 children qualified for the study. Radiograph interpretations were available for 762, and 10.5% were found to have radiographic pneumonia. The median pulse oximetry reading of children with radiographic pneumonia was 97% (interquartile range 95th-98th percentile) compared with 98% (interquartile range 96th-99th percentile) in the control group. Forty-five percent (35 of 78) of the children with radiographic pneumonia showed oxygen saturations of 98% or higher with greater than 10% (8 of 78) displaying oxygen saturations of 100%. By using logistic regression, pulse oximetry was not found to be a statistically significant predictive variable for radiographic pneumonia. Pulse oximetry could not be used to rule out the presence of radiographic pneumonia in children less than 2 years of age who presented with respiratory complaints. (Am J Emerg Med 2002; 20:521-523. This is a US government work. There are no restrictions on its use.)
Acute respiratory infection in children less than 24 months of age represents one of the most common presentations to the emergency department (ED). The causes of most of these illnesses are viruses but a small proportion are caused by bacteria. The decision on what to base therapy is complicated by a physical examination that is often unreliable in the detection of pneumonia.1-5 Over the past decade, pulse oximetry has been used with increasing frequency as
From the Department of Emergency Medicine, Naval Medical Center, San Diego, CA. Manuscript received May 21, 2001, accepted January 1, 2002. Supported by the Chief, Bureau of Medicine and Surgery, Navy Department, Washington, DC, Clinical Investigation Program, #97087 as required by NSHSBETHINST 6000.41A. The views expressed in this article are those of the author and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government. Address reprint requests to David A Tanen, MD, Department of Emergency Medicine, Naval Medical Center, 34800 Bob Wilson Drive, San Diego, CA 92134-5000. E-mail: [email protected] Key Words: Pulse oximetry, pneumonia, chest radiography. This is a US government work. There are no restrictions on its use. 0735-6757/02/2006-0007$0.00/0 doi:10.1053/ajem.2002.34794
a fifth vital sign.6-11 Previous studies have used opacities on chest radiographs as a gold standard in the diagnosis of pneumonia and have shown that low oxygen saturation correlates with severity of disease.1,2,5,12 We questioned whether a normal oxygen saturation, alone or in conjunction with the physical examination, correlates with the absence of radiographic pneumonia. The purpose of this study was to determine if pulse oximetry, alone or in conjunction with vital signs and clinical examination, could obviate the need to obtain a chest radiograph in the work-up of children with acute respiratory infections. MATERIALS AND METHODS A retrospective chart review of children less than 24 months who presented with respiratory complaints to the ED of a large tertiary care military hospital was initiated. The ED experiences an average of 60,000 patient visits annually, of which 30% are children. The study group consisted of children who presented to the ED over a 1-year period and underwent chest radiography. Inclusion criteria included all children, ages newborn to 24 months of age, who presented to the ED during the period of August 1, 1996, through July 31, 1997, and had chest radiographs (standard posteroanterior and lateral) while in the ED. Exclusion criteria included children on home oxygen or with a tracheostomy. All children were evaluated under the direct supervision of residency-trained staff emergency medicine physicians. Chest radiographs were interpreted by staff radiologists, and the finding of an opacity on the radiograph was considered to be the gold standard for pneumonia in this population. Pulse oximetry measurements were recorded by nurses with patients breathing room air. There were 807 visits that met the inclusion criteria. Four children were excluded (2 with tracheostomies and 2 on home oxygen). Of the remaining 803 visits, 80 radiographs were noted to have an opacity in their lung fields. The emergency treatment records (ETRs) of 78 of the 80 positives were obtained. The ETRs of 156 radiologically normal children of the original 803 were randomly chosen on a month-to-month basis, with a 2:1 ratio, to decrease the influence of staff variability in reading chest radiographs of control to pneumonia patients. Of the 78 children with pneumonia, all ETRs contained heart rate, respiratory rate, and temperature. Seventy-six ETRs recorded a pulse oximetry reading. The presenting heart rate, respiratory rate, and temperature were recorded and were used for analysis. General appearance and lung examination were noted on 77 patients. The controls were selected to contain complete vital signs including pulse 521
AMERICAN JOURNAL OF EMERGENCY MEDICINE ■ Volume 20, Number 6 ■ October 2002
522
FIGURE 1. Histogram showing the distribution of oxygen saturations recorded among children with radiographic pneumonia.
oximetry measurements. Of the 156 controls, general appearance was noted on all ETRs, and lung findings were noted on 155. General appearance was scored in a binary fashion where 0 indicated a healthy, nontoxic, or well-appearing child, and 1 indicated anything else. Lung examination was scored in a binary fashion where 0 indicated a normal examination, and 1 represented any abnormal lung sounds or findings. Opacities were recorded in a binary fashion with 0 indicating no opacity and 1 representing any opacity on chest radiograph as read by a board-prepared or board-certified radiologist. Data were analyzed by using step-wise logistic regression using radiographic opacity as the dependent variable and oxygen saturation and clinical findings as independent variables. A P value of greater than .05 was taken as the criterion for removal of a variable in backward step-wise regression. A rank-sum test was used to compare the pulse oximetry measurements from the 2 groups because the normality assumption of a t test was rejected by a ShapiroWilk test of normality (P ⬍ .001 for both groups). Institutional review board approval was obtained. RESULTS In our study population of children under the age of 24 months, 803 chest radiographs were obtained and analyzed. Chest radiograph results were analyzed on a month-tomonth basis. Five percent of chest radiograph reports could not be found. Of radiographs reported, 80 (10.5%) chest radiographs revealed opacities. The median pulse oximetry reading of children with radiographic pneumonia was 97% (interquartile range 95th-
98th percentile) compared with 98% (interquartile range 96th-99th percentile) in the control group. Forty-five percent (35 of 78) of children with radiographic pneumonia showed oxygen saturations of 98% or higher with greater than 10% (8 of 78) displaying oxygen saturations of 100% (Fig 1). To determine the predictive value of pulse oximetry for pneumonia in relation to other recorded variables, logistic regression was performed. Means and standard error of the mean of vital signs were recorded along with the percent of positive abnormalities on lung examinations and general appearances (Table 1). This analysis revealed that only lung examination, age, and respiratory rate were predictive of opacity (P ⫽ .015) and that their predictive power was weak (R2 ⫽ .072). Pulse oximetry was found to be nonpredictive of opacity (Table 2). DISCUSSION Pulse oximetry has become commonplace in most EDs. Studies have previously shown that low pulse oximetry readings clinically correlate with pulmonary pathology.1,2,7,9,10,12 However, previous studies have not examined whether normal pulse oximetry readings correlate with the absence of radiographic evidence of pneumonia. Our findings suggest that pulse oximetry is not a useful modality in excluding pneumonia in infants and should not influence the decision of whether a chest radiograph should be obtained. These findings may be explained by the fact that for hypoxemia to occur, a significant ventilation-perfusion mismatch must be present. In our group, it is possible that many of the opacities represented small or round pneumonias that did not induce a substantial ventilation-perfusion mismatch.
TABLE 1. Comparison of Infants With Radiographic Pneumonia Versus Control Groups With Means and SEM of the Continuous Variables and Tallies (%) of Abnormalities in General Appearance and Lung Examination
Pneumonia Controls
Number
Age
Respiratory Rate
Heart Rate
Temperature
General Appearance
Lung Examination
78 156
12 mo ⫾ 0.8 10 mo ⫾ 0.6
42 ⫾ 1.5 37 ⫾ 0.9
159 ⫾ 2.3 159 ⫾ 2.1
101.8 ⫾ 0.3 101.4 ⫾ 0.2
32% 22%
52% 36%
TANEN AND TROCINSKI ■ PULSE OXIMETRY AND PNEUMONIA
523
TABLE 2. Outcome of Logistic Regression as Predicted By Heart Rate, Temperature, General Appearance, Pulse Oximetry, Age, Respiratory Rate, and Lung Examination
bronchiolitis, which may have lowered the mean oxygen saturation of the group, thereby limiting the difference found between groups. Review of the data collection forms revealed that 21 of 156 (13.5%) children in the control group had evidence of wheezing. However, had these patients been excluded from analysis, the mean oxygen saturation of the control group would have remained unchanged at 97.4%. Interrater variability between radiologists was not measured but final interpretation of the chest radiographs was completed by board-prepared or board-certified radiologists. A 2:1 ratio of control to opacity radiographs read on a month-to-month basis was used to decrease the influence of radiologist variability in reading chest radiographs. The study defined opacities as the gold standard for pneumonia, against which other variables were compared. Opacities found on chest radiographs in fact may not represent pneumonia and may indicate atelectasis, thymus, or tumor. However, the emergency medicine physician faced with a child with a respiratory illness who detects an opacity on the chest radiograph will most likely treat that opacity as pneumonia and therefore is a useful marker clinically. Arranging follow-up radiographs to document resolution is of paramount importance to rule out other etiologies for the opacity. In conclusion, pulse oximetry, alone or in combination with vital signs, general appearance, and lung examination, could not be used to rule out the presence of radiographic pneumonia in children less than 2 years of age who present with upper-respiratory complaints. Further prospective investigation is warranted to clarify the role of pulse oximetry in conjunction with other clinical variables to predict the likelihood of pneumonia.
Independent Variables
Regression Result
P Value
Heart rate Temperature General appearance Pulse oximetry Lung examination Age Respiratory rate
Removed Removed Removed Removed Retained Retained Retained
.855* .269* .212* .190* .015 .013 .002
*P value of variables removed from predictive model. The R2 for lung examination, age, and respiratory rate was .072.
Further, pulse oximetry may fail to detect a small ventilation-perfusion mismatch that did not result in an abnormal hemoglobin oxygen saturation. Although differences in pulse oximetry measurements between the 2 groups was statistically significant, a 1% difference in oxygen saturation is not clinically useful. The fact that 45% of children with radiographic evidence of pneumonia had oxygen saturations of 98% or higher clearly shows that oxygen saturation alone cannot be used to exclude the presence of pneumonia. Because a small statistical difference between the oxygen saturations of the 2 groups was detected, the possibility was explored that if pulse oximetry was combined with the traditional vital signs, general appearance, and lung examination; it may yield useful clinical information. Again, through logistic regression analysis, pulse oximetry was shown to have no statistically significant or clinically predictive value for detecting pneumonia. Logistic regression did find the results of the lung examination, age, and respiration rate to have predictive ability. However, respiration rate is known to be correlated with age, as was also evidenced in our study (regression of respiration rate on age showed P ⫽ .003). To examine the effect of age alone, logistic regression of opacity on age was performed and it was not statistically significant (P ⫽ .058). The apparent influence of age in the original logistic regression was thus likely owing to its correlation with respiratory rate, and can be eliminated as a predictor of pneumonia. Therefore, only respiration rate and the lung examination are predictive variables for opacity, albeit weak (R2 ⫽ .072). Limitations to this retrospective study include possible bias in documentation of general appearance and lung examination based on the chest radiograph findings and final diagnosis. This may account for the documentation of increased lung findings and ill appearance of children with opacities. All children who had pneumonia and did not receive chest radiography were excluded from this study. It is unclear how this would have affected the results, however, given the previously identified association between low pulse oximetry and pneumonia,1,2,7,9,10,12 it is doubtful whether the sickest children or those needing hospitalization would have been excluded. Another limitation is that the control group probably contained children with reactive airway disease, asthma, or
REFERENCES 1. Margolis P, Gadomski A: Does this infant have pneumonia? JAMA 1998;279:308-13 2. Zukin DD, Hoffman JR, Cleveland RH, et al: Correlation of pulmonary signs and symptoms with chest radiographs in the pediatric age group. Ann Emerg Med 1986;15:792-6 3. Weber MW, Usen S, Palmer A, et al: Predictors of hypoxaemia in hospital admissions with acute lower respiratory tract infection in a developing country. Arch Dis Child 1997;76:310-4 4. Cherian T, Simoes E, John TJ, et al: Evaluation of simple clinical signs for the diagnosis of acute lower respiratory tract infection. Lancet 1988;8603:125-8 5. Harari M, Shann F, Spooner V, et al: Clinical signs of pneumonia in children. Lancet 1991;338:928-30 6. Mower WR, Sachs C, Nicklin EL, et al: Pulse oximetry as a fifth pediatric vital sign. Pediatrics 1997;99:681-6 7. Maneker AJ, Petrack EM, Kyug SE: Contribution of routine pulse oximetry to evaluation and management of patients with respiratory illness in a pediatric emergency department. Ann Emerg Med 1995;25:36-40 8. Summers RL, Anders RM, Woodward LH, et al: Effect of routine pulse oximetry measurements on ED triage classification. Am J Emerg Med 1998;16:5-7 9. Mower WR, Sachs C, Nicklin EL, et al: Effect of routine emergency department triage pulse oximetry screening on medical management. Chest 1995;108:1297-302 10. Madico G, Gilman RH, Jabra A, et al: The role of pulse oximetry. Its use as an indicator of severe respiratory disease in Peruvian children living at sea level. Arch Pediatr Adolesc Med 1995;149:1259-63 11. Panacek EA: The use of pulse oximetry in the emergency department. J Emerg Med 1995;13:816-7 12. Lozano JM, Steinhoff M, Ruiz JG, et al: Clinical predictors of acute radiological pneumonia and hypoxaemia at high altitude. Arch Dis Child 1994;71:323-7
Acute respiratory infection in children less than 24 months of age represents one of the most common presentations to the emergency department (ED). The causes of most of these illnesses are viruses but a small proportion are caused by bacteria. The decision on what to base therapy is complicated by a physical examination that is often unreliable in the detection of pneumonia.1-5 Over the past decade, pulse oximetry has been used with increasing frequency as
From the Department of Emergency Medicine, Naval Medical Center, San Diego, CA. Manuscript received May 21, 2001, accepted January 1, 2002. Supported by the Chief, Bureau of Medicine and Surgery, Navy Department, Washington, DC, Clinical Investigation Program, #97087 as required by NSHSBETHINST 6000.41A. The views expressed in this article are those of the author and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government. Address reprint requests to David A Tanen, MD, Department of Emergency Medicine, Naval Medical Center, 34800 Bob Wilson Drive, San Diego, CA 92134-5000. E-mail: [email protected] Key Words: Pulse oximetry, pneumonia, chest radiography. This is a US government work. There are no restrictions on its use. 0735-6757/02/2006-0007$0.00/0 doi:10.1053/ajem.2002.34794
a fifth vital sign.6-11 Previous studies have used opacities on chest radiographs as a gold standard in the diagnosis of pneumonia and have shown that low oxygen saturation correlates with severity of disease.1,2,5,12 We questioned whether a normal oxygen saturation, alone or in conjunction with the physical examination, correlates with the absence of radiographic pneumonia. The purpose of this study was to determine if pulse oximetry, alone or in conjunction with vital signs and clinical examination, could obviate the need to obtain a chest radiograph in the work-up of children with acute respiratory infections. MATERIALS AND METHODS A retrospective chart review of children less than 24 months who presented with respiratory complaints to the ED of a large tertiary care military hospital was initiated. The ED experiences an average of 60,000 patient visits annually, of which 30% are children. The study group consisted of children who presented to the ED over a 1-year period and underwent chest radiography. Inclusion criteria included all children, ages newborn to 24 months of age, who presented to the ED during the period of August 1, 1996, through July 31, 1997, and had chest radiographs (standard posteroanterior and lateral) while in the ED. Exclusion criteria included children on home oxygen or with a tracheostomy. All children were evaluated under the direct supervision of residency-trained staff emergency medicine physicians. Chest radiographs were interpreted by staff radiologists, and the finding of an opacity on the radiograph was considered to be the gold standard for pneumonia in this population. Pulse oximetry measurements were recorded by nurses with patients breathing room air. There were 807 visits that met the inclusion criteria. Four children were excluded (2 with tracheostomies and 2 on home oxygen). Of the remaining 803 visits, 80 radiographs were noted to have an opacity in their lung fields. The emergency treatment records (ETRs) of 78 of the 80 positives were obtained. The ETRs of 156 radiologically normal children of the original 803 were randomly chosen on a month-to-month basis, with a 2:1 ratio, to decrease the influence of staff variability in reading chest radiographs of control to pneumonia patients. Of the 78 children with pneumonia, all ETRs contained heart rate, respiratory rate, and temperature. Seventy-six ETRs recorded a pulse oximetry reading. The presenting heart rate, respiratory rate, and temperature were recorded and were used for analysis. General appearance and lung examination were noted on 77 patients. The controls were selected to contain complete vital signs including pulse 521
AMERICAN JOURNAL OF EMERGENCY MEDICINE ■ Volume 20, Number 6 ■ October 2002
522
FIGURE 1. Histogram showing the distribution of oxygen saturations recorded among children with radiographic pneumonia.
oximetry measurements. Of the 156 controls, general appearance was noted on all ETRs, and lung findings were noted on 155. General appearance was scored in a binary fashion where 0 indicated a healthy, nontoxic, or well-appearing child, and 1 indicated anything else. Lung examination was scored in a binary fashion where 0 indicated a normal examination, and 1 represented any abnormal lung sounds or findings. Opacities were recorded in a binary fashion with 0 indicating no opacity and 1 representing any opacity on chest radiograph as read by a board-prepared or board-certified radiologist. Data were analyzed by using step-wise logistic regression using radiographic opacity as the dependent variable and oxygen saturation and clinical findings as independent variables. A P value of greater than .05 was taken as the criterion for removal of a variable in backward step-wise regression. A rank-sum test was used to compare the pulse oximetry measurements from the 2 groups because the normality assumption of a t test was rejected by a ShapiroWilk test of normality (P ⬍ .001 for both groups). Institutional review board approval was obtained. RESULTS In our study population of children under the age of 24 months, 803 chest radiographs were obtained and analyzed. Chest radiograph results were analyzed on a month-tomonth basis. Five percent of chest radiograph reports could not be found. Of radiographs reported, 80 (10.5%) chest radiographs revealed opacities. The median pulse oximetry reading of children with radiographic pneumonia was 97% (interquartile range 95th-
98th percentile) compared with 98% (interquartile range 96th-99th percentile) in the control group. Forty-five percent (35 of 78) of children with radiographic pneumonia showed oxygen saturations of 98% or higher with greater than 10% (8 of 78) displaying oxygen saturations of 100% (Fig 1). To determine the predictive value of pulse oximetry for pneumonia in relation to other recorded variables, logistic regression was performed. Means and standard error of the mean of vital signs were recorded along with the percent of positive abnormalities on lung examinations and general appearances (Table 1). This analysis revealed that only lung examination, age, and respiratory rate were predictive of opacity (P ⫽ .015) and that their predictive power was weak (R2 ⫽ .072). Pulse oximetry was found to be nonpredictive of opacity (Table 2). DISCUSSION Pulse oximetry has become commonplace in most EDs. Studies have previously shown that low pulse oximetry readings clinically correlate with pulmonary pathology.1,2,7,9,10,12 However, previous studies have not examined whether normal pulse oximetry readings correlate with the absence of radiographic evidence of pneumonia. Our findings suggest that pulse oximetry is not a useful modality in excluding pneumonia in infants and should not influence the decision of whether a chest radiograph should be obtained. These findings may be explained by the fact that for hypoxemia to occur, a significant ventilation-perfusion mismatch must be present. In our group, it is possible that many of the opacities represented small or round pneumonias that did not induce a substantial ventilation-perfusion mismatch.
TABLE 1. Comparison of Infants With Radiographic Pneumonia Versus Control Groups With Means and SEM of the Continuous Variables and Tallies (%) of Abnormalities in General Appearance and Lung Examination
Pneumonia Controls
Number
Age
Respiratory Rate
Heart Rate
Temperature
General Appearance
Lung Examination
78 156
12 mo ⫾ 0.8 10 mo ⫾ 0.6
42 ⫾ 1.5 37 ⫾ 0.9
159 ⫾ 2.3 159 ⫾ 2.1
101.8 ⫾ 0.3 101.4 ⫾ 0.2
32% 22%
52% 36%
TANEN AND TROCINSKI ■ PULSE OXIMETRY AND PNEUMONIA
523
TABLE 2. Outcome of Logistic Regression as Predicted By Heart Rate, Temperature, General Appearance, Pulse Oximetry, Age, Respiratory Rate, and Lung Examination
bronchiolitis, which may have lowered the mean oxygen saturation of the group, thereby limiting the difference found between groups. Review of the data collection forms revealed that 21 of 156 (13.5%) children in the control group had evidence of wheezing. However, had these patients been excluded from analysis, the mean oxygen saturation of the control group would have remained unchanged at 97.4%. Interrater variability between radiologists was not measured but final interpretation of the chest radiographs was completed by board-prepared or board-certified radiologists. A 2:1 ratio of control to opacity radiographs read on a month-to-month basis was used to decrease the influence of radiologist variability in reading chest radiographs. The study defined opacities as the gold standard for pneumonia, against which other variables were compared. Opacities found on chest radiographs in fact may not represent pneumonia and may indicate atelectasis, thymus, or tumor. However, the emergency medicine physician faced with a child with a respiratory illness who detects an opacity on the chest radiograph will most likely treat that opacity as pneumonia and therefore is a useful marker clinically. Arranging follow-up radiographs to document resolution is of paramount importance to rule out other etiologies for the opacity. In conclusion, pulse oximetry, alone or in combination with vital signs, general appearance, and lung examination, could not be used to rule out the presence of radiographic pneumonia in children less than 2 years of age who present with upper-respiratory complaints. Further prospective investigation is warranted to clarify the role of pulse oximetry in conjunction with other clinical variables to predict the likelihood of pneumonia.
Independent Variables
Regression Result
P Value
Heart rate Temperature General appearance Pulse oximetry Lung examination Age Respiratory rate
Removed Removed Removed Removed Retained Retained Retained
.855* .269* .212* .190* .015 .013 .002
*P value of variables removed from predictive model. The R2 for lung examination, age, and respiratory rate was .072.
Further, pulse oximetry may fail to detect a small ventilation-perfusion mismatch that did not result in an abnormal hemoglobin oxygen saturation. Although differences in pulse oximetry measurements between the 2 groups was statistically significant, a 1% difference in oxygen saturation is not clinically useful. The fact that 45% of children with radiographic evidence of pneumonia had oxygen saturations of 98% or higher clearly shows that oxygen saturation alone cannot be used to exclude the presence of pneumonia. Because a small statistical difference between the oxygen saturations of the 2 groups was detected, the possibility was explored that if pulse oximetry was combined with the traditional vital signs, general appearance, and lung examination; it may yield useful clinical information. Again, through logistic regression analysis, pulse oximetry was shown to have no statistically significant or clinically predictive value for detecting pneumonia. Logistic regression did find the results of the lung examination, age, and respiration rate to have predictive ability. However, respiration rate is known to be correlated with age, as was also evidenced in our study (regression of respiration rate on age showed P ⫽ .003). To examine the effect of age alone, logistic regression of opacity on age was performed and it was not statistically significant (P ⫽ .058). The apparent influence of age in the original logistic regression was thus likely owing to its correlation with respiratory rate, and can be eliminated as a predictor of pneumonia. Therefore, only respiration rate and the lung examination are predictive variables for opacity, albeit weak (R2 ⫽ .072). Limitations to this retrospective study include possible bias in documentation of general appearance and lung examination based on the chest radiograph findings and final diagnosis. This may account for the documentation of increased lung findings and ill appearance of children with opacities. All children who had pneumonia and did not receive chest radiography were excluded from this study. It is unclear how this would have affected the results, however, given the previously identified association between low pulse oximetry and pneumonia,1,2,7,9,10,12 it is doubtful whether the sickest children or those needing hospitalization would have been excluded. Another limitation is that the control group probably contained children with reactive airway disease, asthma, or
REFERENCES 1. Margolis P, Gadomski A: Does this infant have pneumonia? JAMA 1998;279:308-13 2. Zukin DD, Hoffman JR, Cleveland RH, et al: Correlation of pulmonary signs and symptoms with chest radiographs in the pediatric age group. Ann Emerg Med 1986;15:792-6 3. Weber MW, Usen S, Palmer A, et al: Predictors of hypoxaemia in hospital admissions with acute lower respiratory tract infection in a developing country. Arch Dis Child 1997;76:310-4 4. Cherian T, Simoes E, John TJ, et al: Evaluation of simple clinical signs for the diagnosis of acute lower respiratory tract infection. Lancet 1988;8603:125-8 5. Harari M, Shann F, Spooner V, et al: Clinical signs of pneumonia in children. Lancet 1991;338:928-30 6. Mower WR, Sachs C, Nicklin EL, et al: Pulse oximetry as a fifth pediatric vital sign. Pediatrics 1997;99:681-6 7. Maneker AJ, Petrack EM, Kyug SE: Contribution of routine pulse oximetry to evaluation and management of patients with respiratory illness in a pediatric emergency department. Ann Emerg Med 1995;25:36-40 8. Summers RL, Anders RM, Woodward LH, et al: Effect of routine pulse oximetry measurements on ED triage classification. Am J Emerg Med 1998;16:5-7 9. Mower WR, Sachs C, Nicklin EL, et al: Effect of routine emergency department triage pulse oximetry screening on medical management. Chest 1995;108:1297-302 10. Madico G, Gilman RH, Jabra A, et al: The role of pulse oximetry. Its use as an indicator of severe respiratory disease in Peruvian children living at sea level. Arch Pediatr Adolesc Med 1995;149:1259-63 11. Panacek EA: The use of pulse oximetry in the emergency department. J Emerg Med 1995;13:816-7 12. Lozano JM, Steinhoff M, Ruiz JG, et al: Clinical predictors of acute radiological pneumonia and hypoxaemia at high altitude. Arch Dis Child 1994;71:323-7