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Incidence of Pneumothorax and Pneumomediastinum in Patients with Aspiration Pneumonia Requiring Ventilatory Support
Incidence of Pneumothorax and Pneumomediastinum in Patients with Aspiration Pneumonia Requiring Ventilatory Support* Francisco]. de Latorre, M.D.; Antonio Tomasa, M.D.; Jorge Klamburg, M.D.; Cristobal Leon, M.D.; Manuel Soler, M.D.; and Jorge Rius, M.D.
In a prospective study of patients with ventilatory support, six (38 percent) of 16 patients who bad ventilatory support because of aspiration pneumonia developed pneumothorax and pneumomediastinum. In contrast, the incidence of barotrauma in the entire group of pa-
tients who bad ventilatory support during a year was 4 percent (22/ SS3) (P < 0.001). This greater incidence in the gronp with aspiration pneumonia was also observed when patients who were receiving ventilatory support with positive end-esplratory pre8811re were excluded.
pneumothorax and pneumomediastinum are two of the complications encountered in patients during ventilatory therapy. These complications are more frequent under certain circumstances, such as ventilatory support using positive end-expiratory pressure (PEEP), 1 necrotizing pneumonia,2 intubation of the right bronchus,1 chronic airway obstruction,3·4 or the use of volume-cycled ventilators.4 In a recent retrospective review of patients with aspiration pneumonia, we found a high incidence of pneumothorax and pneumomediastinum.~> The purpose of the present prospective study was to investigate the incidence of pneumothorax and pneumomediastinum in patients with or without aspiration pneumonia who were receiving ventilatory support.
ventilatory support included all disease states leading to respiratory failure. Posttraumatic patients were excluded. Sixteen of the 553 patients had suffered pulmonary aspiration of gastric contents. The diagnosis of aspiration was made when vomiting and aspiration were witnessed. Removal of gastric contents from the trachea was possible in eight of the patients. The primary illness, the factors predisposing to aspiration, the clinical status at the beginning of mechanical ventilation, the type of ventilator, and the PEEP employed when barotrauma occurred are summarized in Table 1. None of these patients had preexisting pulmonary disease (chronic airway obstruction or restrictive pulmonary disease). Twenty-two of the 553 patients requiring ventilatory support had evidence of pulmonary barotrauma. The diagnosis of pneumothorax or pneumomediastinum or both was confirmed by x-ray films. Five patients with ventilatory support and pneumothorax secondary to other therapeutic measures (external cardiac massage, subclavian venipuncture, or insertion of chest tube) were not included in this study. The statistical significance of the variables studied was analyzed by means of the x.2 test.
MATERIALS AND METHODS
The present study was performed in a multidisciplinary intensive care unit of 18 beds. Five hundred and fifty-three consecutive patients receiving ventilatory support were included. They made up the whole of the patients receiving ventilatory therapy in our intensive care unit during the 12month period from January to December 1975. 11le length of ventilatory support varied from a few hours to 170 days, with a mean of four days. The ages of the patients ranged from 7 to 91 years (mean, 49 years) . Pressure-cycled devices (bird Mark 8) were used in 355 patients and volume-cycled devices (Engstrom ER 300, Bennett MAl, or Servo Ventilator 900) were used in 139 patients. In 59 patients, both types were used. The indications for the °From the Servicio de Cuidados Intensivos, Ciudad Sanitaria de Ia Seguridad Social, Barcelona, Spain. Manuscript received July 27, 1976; revision accepted November2.
CHEST, 72: 2, AUGUST, 1977
fu:suLTS The overall incidence of barotrauma was 4 percent (22/553) . Pneumothorax or pneumomediastinum. or both developed in six ( 38 percent) of 16 patients with aspiration pneumonia. The incidence of these complications in this group is very high, as compared to the rest of the patients with ventilatory support, in which the incidence was only 3 percent (16/537) (P < 0.001). The primary illness of these 16 patients and the circumstances in which barotrauma occurred (type of ventilator and PEEP) are presented in Table 2. This increased incidence, statistically significant, was still observed when patients
PNEUMOTHORAX AND PNEUMOMEDIASTINUM IN ASPIRATION PNEUMONIA 141
Table 1--CUnical Data from Paliem. lftth A•pirarion Pneumonia at the
Group and Case, Age Barotrauma 1, 24
FlO, and Type of Ventilation
pH
PaO,, PaCO,, mm Hg mm Hg
Primary Illness
0.40, mechanical
7.32
55
41
Cesarean section**
0.40, mechanical 0.51, mechanical 0.35, spontaneous 1.00, mechanical 0.31, spontaneous
7.36
70
42
7.26
69
45
7.43
48
34
Carbon monoxide poisoning Occlusion of bowel** Drug intoxication
7.54
79
22
7.21
135
55
0.40, spontaneous
7.40
47
35
Carbon monoxide poisoning
2, 27
0.40, spontaneous
7.38
96
26
Eclampsia (sedation)
3, 50
0.40, spontaneous 0.40, mechanical
7.24
69
35
Alcoholic stupor
7.48
86
28
Drug intoxication
5, 36
0.40, mechanical
7.32
72
36
Eclampsia (sedation)
6, 72
0.40, mechanical 0.21, spontaneous 0.40, mechanical 0.40, mechanical 1.00, mechanical
7.36
62
45
7.46
47
7.39
2, 19
3, 80 4,23 5, 31 6, 61
No barotrauma 1, 36
4, 15
7, 41
8, 75 9, 64 10,44
Eclampsia (sedation) Carcinoma of colon••
Be~nniRB
Infiltration on Chest X-Ray Film
o/ Mechanical J' entilolion
Type of Ventilator•
PEEP, em
H,o•
Outcome
Right lung and left lower lobe Bilateral
v
0
Died
v
10
Died
Bilateral
p
0
Lived
Right lower lobe Bilateral
Pt
0
Died
v
10
Died
Bilateral
Pt
0
Died
Right lower lobe and left lung Right upper and left lower lobes Left lung
p
0
Lived
Vt
0
Lived
p
0
Died
p
0
Lived
p
0
Lived
Drug intoxication
Right lung and left lower lobe Right and left lower lobes Right lung
p
0
Lived
28
Alcoholic stupor
Right lung
v
0
Lived
53
26
Bilateral
v
0
Died
7.27
78
51
Occlusion of bowel** Drug intoxication
Bilateral
p
0
Died
7.40
62
34
Evisceration • •
Bilateral
v
12
Lived
•v,
Volume-preset device; and P, pressure-preset device. Type of ventilat<>r and PEEP are those used when pulmonary barotrauma occurred. •• Aspiration in induction of anesthesia. tPatients who also received ventilatory support with other type of ventilator.
receiving ventilatory support with PEEP were excluded ( Fig 1 ) . Pneumothorax, pneumomediastinum, and subcutaneous emphysema occurred after the first hours and up to 34 days of continuous ventilatory support. Pneumothorax occurred on the left side in seven cases and on the right side in seven cases. In three of these 14 cases, pneumomediastinum or subcutaneous emphysema or both were associated with the pneumothorax. Bilateral pneumothorax occurred in six cases and was associated with pneumomediastinum and subcutaneous emphysema in three of them. The two other patients had pneumomediastinum (with subcutaneous emphysema in one of them) . 142 DE LATORRE ET AL
Except for three of the patients, pneumomediastinum and subcutaneous emphysema preceded or occurred simultaneously with the detection of pneumothorax. Patients using volume-cycled devices had an incidence of barotrauma of 9 percent ( 13/139), as compared to 1 percent ( 5/355) of the patients who used pressure-cycled devices ( P < 0.001) and to 7 percent ( 4/59) of the patients in whom both types of machines were used (P > 0.1; not significant). Seventy-three of 553 patients had preexisting pulmonary disease (chronic airway obstruction). Six ( 8 percent) of these 73 patients developed pneumothorax and pneumomediastinum. This incidence is CHEST, 72: 2, AUGUST, 1977
Table
Case, Age 1, 2, 3, 4, 5, 6, 7,
70 34 74 74 21 72 36
8, 32 9, 59 10, 28 11, 16 12,47 13, 18 14, 23 15,66 16, 42
Data /rom Patient. Aapiralion. Pneumonia
~linical
Primary Illness*
Type of Ventilator**
Right lobar pneuPeritonitis; ARDS CAO Bronchopneumonia Bronchopneumonia CAO Right lobar pneumonia Pulmonary involvement of lymphosarcoma CAO Mitral stenosis; pulmonary edema Meningioma; pulmonary edema Mitral stenosis; pulmonary edema Drug intoxication Bronchopneumonia CAO Status asthmaticus
tc~ilhoul
PEEP, em
H,o••
Outcome
v
0 10 0 0 0 0 0
Died Died Died Died Lived Died Died
v
0
Died
v v
0 0
Died Died
v
0
Lived
p
0
Lived
v v
0 8 0 0
Died Died Died Lived
Pt
v
Vt
v v p
p
Pt
*CAO, Chronic airway obstruction; and ARDS, adult respiratory distress syndrome. ••v, Volume-preset device; and P, pressure-preset device. Type of ventilator and PEEP are those used when pulmonary barotrauma occurred. tPatients who also received ventilatory support with other type of ventilator.
higher than the 4 percent ( 18/480) observed in patients with ventilatory support without previous chronic airway obstruction, although this difference was not of statistical significance. None of the 73 patients with chronic airway obstruction received ventilatory support with PEEP. If a fractional concentration of oxygen in the inspired gas ( FI
PATIENTS WITHOUT ASPIRATION PNEUMONIA
~
PATIENTS
WITH
ASPIRATION PNEUMONIA
50
..."'z
"' 0
u
..
40
6/16
30
~
20 10
TOTAL
PATIENTS VENTILATED"
PATIENTS
WITHOUT
PEEP+
• P< 0.001 + P< 0.001
1. Incidence of pneumothorax or pneumomediastinum or both in patients with and without aspiration pneumonia who are receiving ventilatory support. FiGURE
CHEST, 72: 2, AUGUST, 1977
above 60 mm Hg, PEEP was used. This method of ventilation was used in 33 of 553 cases. Five ( 15 percent) of these 33 patients developed pneumothorax or pneumomediastinum or both, and this represents a significant increase in the incidence of barotrauma if we compare it with the patients ventilated without PEEP (3 percent or 17/520) (P < 0.025). · The mortality in 22 patients with barotrauma was 77 percent ( 17I 22); this is a very high value, as compared to the 33 percent ( 180/553) that was the overall mortality in the patients with ventilatory support ( P < 0.001) . DiscuSSION
Positive-pres.sure ventilation may cause alveolar rupture; with the production of pneumothorax, pneumomediastinum, and subsequent subcutaneous emphysema. Although the overpressured airway is the mechanism of alveolar rupture, there are several factors which may predispose to the development of barotrauma. u.s A report has postulated that the use of volumecycled devices may be followed by an increased incidence of iatrogenic pneumothorax,' and we have also observed this in our patients. Patients with more pulmonary damage are generally ventilated with volume-preset ventilators. This factor should be considered in any conclusions that are drawn; however, patients with volume-cycled deviees are exposed to a peak airway pressure higher than those ventilated ·with pressure-cycled devices. Therefore, when volume-cycled ventilators are employed, the highest airway pres.sure should be kept within a range of values where the risk of pneumothorax is minimum. 3 In spite of a recent study which does not report an augmented incidence of barotrauma in patients receiving therapy with PEEP,3 we have found an increased number of cases of pneumothorax and pneumomediastinum in this group, as other investigators have observed.1 We have found a very high incidence of pneumothorax and pneumomediastinum in 16 patients with aspiration pneumonia. In a retrospective study,6 we had already observed an incidence of barotrauma of 27 percent ( 4/ 15) in patients with aspiration pneumonia who were receiving ventilatory support. Nevertheless, we have not found aspiration pneumonia reported as a precipitating factor for barotrauma in ·a review of published studies on pneumothorax and pneumomediastinum during mechanical ventilation.l-4.6-8 This incidence of pneumothorax in patients with aspiration pneumonia, by far higher than that seen in patients receiving ventilatory ther-
PNEUMOTHORAX AND PNEUMOMEDIASnNUM IN ASPIRAnOH PNEUMONIA 143
1
(
apy because of other conditions ( P < 0.001), was still observed when we excluded those patients receiving ventilatory support with PEEP (Fig 1), a treatment that may by itself predispose to the development of pneumothorax. Acute respiratory failure following aspiration of gastric contents is accompanied by a pulmonary injury that extends from the tracheobr~nchial tree to the periphery of the lung, with areas of frank necrosis.&-11 The necrosis of bronchiolar and alveolar walls may predispose to the development of pneumothorax and pneumomediastinum, as in necrotizing pneumonia. 2 If further work confirms· this higher incidence of barotrauma in patients with aspiration pneumonia who are receiving ventilatory support, it will seem reasonable to include these patientS among those at high risk of developing pneumothorax when they are receiving ventilatory therapy. Barotrauma should be carefully sought in these patients, and a thoracostomy tube should be immediately inserted in case of a positive diagnosis. 1 ACKNOWLEDGMENT: We would like to thank Dr. Juan Padro and Dr. Ramon Peracaula for their assistance in the clinical follow-up of the cases, and Dr. Cafetano Pennanyer and Dr. Jaime Guardia for their helpfu revision of this manuscript. REFERENCES
1 Zwillich CW, Pierson DJ, Creagh CE, et al: Complica-
tions of assisted ventilation: A prospective study of 354 consecutive episodes. Am J Med 57:161-170, 1974 2 Fleming WH, Bowen JC, Hatcher CR: Early complications of long-tenn respiratory support. J Thorac Cardi~ vase Surg 64:729-737, 1972 3 Kumar A, Pontoppidan H, Falke KJ, et al: Pulmonary barotrauma during mechanical ventilation. Crit Care Med
1:181-186, 1973
4 Steier M, Ching N, Roberts EB, ell al: Pneumothorax complicating continuous ventilatory support. J Thorac Cardiovasc Surg 67: 17-23, 1974 5 de Latorre FJ, Tomasa A, Klamberg J, et al: Edema pulmonar agudo por inhalacion de contenido gastrico (sindrome de Mendelson). Rev Clin Esp, to be published 6 Zimmerman JE, Dumbar BS, Klingenmaier CH: Management of subcutaneous emphysema, pneumomediastinum and pneumothorax during respiratory therapy. Crit Care Med 3:69-73, 1975 1 Nennhaus HP, Javid H, Julian OC: Alveolar and pleural rupture: Hazards of positive pressure respiration. Arch Surg 94:136-141, 1967 8 Lareng L, Jorda MF, Brouchet A, et al: Les pneum~ thorax sous respirateur artificiel. Anesth Anal (Paris)
29:651-659, 1972 9 Lewinski A: Evaluation of methods employed in the treatment of the chemical pneumonitis of aspiration. Anesthesiology 26:37-44, 1965 10 Alexander IGS : The ultrastructure of the pulmonary alveolar vessels in Mendelson's (acid pulmonary aspiration) syndrome. Br J Anaesth 40:408-414, 1968 11 Toung TJK, Bordos D, Benson DW, et al : Aspiration pneumonia: Experimental evaluation of albumin and steroid therapy. Ann Surg 183:179-184, 1976
Call for Abstracts, International Union Against Tuberculosis The XXIV Conference of the International Union Against Tuberculosis will be held in Brussels, Belgium, September 3-9, 1978. Summaries of proposed presentations (not more than 300 words) should be submitted by September 30, 1977, in quintuplicate, English or French. Send to: International Union Against Tuberculosis, 3 Rue Georges Ville, 65 116 Paris, France.
144 DE LATORRE ET Al
CHEST, 72: 2, AUGUST, 1977
In a prospective study of patients with ventilatory support, six (38 percent) of 16 patients who bad ventilatory support because of aspiration pneumonia developed pneumothorax and pneumomediastinum. In contrast, the incidence of barotrauma in the entire group of pa-
tients who bad ventilatory support during a year was 4 percent (22/ SS3) (P < 0.001). This greater incidence in the gronp with aspiration pneumonia was also observed when patients who were receiving ventilatory support with positive end-esplratory pre8811re were excluded.
pneumothorax and pneumomediastinum are two of the complications encountered in patients during ventilatory therapy. These complications are more frequent under certain circumstances, such as ventilatory support using positive end-expiratory pressure (PEEP), 1 necrotizing pneumonia,2 intubation of the right bronchus,1 chronic airway obstruction,3·4 or the use of volume-cycled ventilators.4 In a recent retrospective review of patients with aspiration pneumonia, we found a high incidence of pneumothorax and pneumomediastinum.~> The purpose of the present prospective study was to investigate the incidence of pneumothorax and pneumomediastinum in patients with or without aspiration pneumonia who were receiving ventilatory support.
ventilatory support included all disease states leading to respiratory failure. Posttraumatic patients were excluded. Sixteen of the 553 patients had suffered pulmonary aspiration of gastric contents. The diagnosis of aspiration was made when vomiting and aspiration were witnessed. Removal of gastric contents from the trachea was possible in eight of the patients. The primary illness, the factors predisposing to aspiration, the clinical status at the beginning of mechanical ventilation, the type of ventilator, and the PEEP employed when barotrauma occurred are summarized in Table 1. None of these patients had preexisting pulmonary disease (chronic airway obstruction or restrictive pulmonary disease). Twenty-two of the 553 patients requiring ventilatory support had evidence of pulmonary barotrauma. The diagnosis of pneumothorax or pneumomediastinum or both was confirmed by x-ray films. Five patients with ventilatory support and pneumothorax secondary to other therapeutic measures (external cardiac massage, subclavian venipuncture, or insertion of chest tube) were not included in this study. The statistical significance of the variables studied was analyzed by means of the x.2 test.
MATERIALS AND METHODS
The present study was performed in a multidisciplinary intensive care unit of 18 beds. Five hundred and fifty-three consecutive patients receiving ventilatory support were included. They made up the whole of the patients receiving ventilatory therapy in our intensive care unit during the 12month period from January to December 1975. 11le length of ventilatory support varied from a few hours to 170 days, with a mean of four days. The ages of the patients ranged from 7 to 91 years (mean, 49 years) . Pressure-cycled devices (bird Mark 8) were used in 355 patients and volume-cycled devices (Engstrom ER 300, Bennett MAl, or Servo Ventilator 900) were used in 139 patients. In 59 patients, both types were used. The indications for the °From the Servicio de Cuidados Intensivos, Ciudad Sanitaria de Ia Seguridad Social, Barcelona, Spain. Manuscript received July 27, 1976; revision accepted November2.
CHEST, 72: 2, AUGUST, 1977
fu:suLTS The overall incidence of barotrauma was 4 percent (22/553) . Pneumothorax or pneumomediastinum. or both developed in six ( 38 percent) of 16 patients with aspiration pneumonia. The incidence of these complications in this group is very high, as compared to the rest of the patients with ventilatory support, in which the incidence was only 3 percent (16/537) (P < 0.001). The primary illness of these 16 patients and the circumstances in which barotrauma occurred (type of ventilator and PEEP) are presented in Table 2. This increased incidence, statistically significant, was still observed when patients
PNEUMOTHORAX AND PNEUMOMEDIASTINUM IN ASPIRATION PNEUMONIA 141
Table 1--CUnical Data from Paliem. lftth A•pirarion Pneumonia at the
Group and Case, Age Barotrauma 1, 24
FlO, and Type of Ventilation
pH
PaO,, PaCO,, mm Hg mm Hg
Primary Illness
0.40, mechanical
7.32
55
41
Cesarean section**
0.40, mechanical 0.51, mechanical 0.35, spontaneous 1.00, mechanical 0.31, spontaneous
7.36
70
42
7.26
69
45
7.43
48
34
Carbon monoxide poisoning Occlusion of bowel** Drug intoxication
7.54
79
22
7.21
135
55
0.40, spontaneous
7.40
47
35
Carbon monoxide poisoning
2, 27
0.40, spontaneous
7.38
96
26
Eclampsia (sedation)
3, 50
0.40, spontaneous 0.40, mechanical
7.24
69
35
Alcoholic stupor
7.48
86
28
Drug intoxication
5, 36
0.40, mechanical
7.32
72
36
Eclampsia (sedation)
6, 72
0.40, mechanical 0.21, spontaneous 0.40, mechanical 0.40, mechanical 1.00, mechanical
7.36
62
45
7.46
47
7.39
2, 19
3, 80 4,23 5, 31 6, 61
No barotrauma 1, 36
4, 15
7, 41
8, 75 9, 64 10,44
Eclampsia (sedation) Carcinoma of colon••
Be~nniRB
Infiltration on Chest X-Ray Film
o/ Mechanical J' entilolion
Type of Ventilator•
PEEP, em
H,o•
Outcome
Right lung and left lower lobe Bilateral
v
0
Died
v
10
Died
Bilateral
p
0
Lived
Right lower lobe Bilateral
Pt
0
Died
v
10
Died
Bilateral
Pt
0
Died
Right lower lobe and left lung Right upper and left lower lobes Left lung
p
0
Lived
Vt
0
Lived
p
0
Died
p
0
Lived
p
0
Lived
Drug intoxication
Right lung and left lower lobe Right and left lower lobes Right lung
p
0
Lived
28
Alcoholic stupor
Right lung
v
0
Lived
53
26
Bilateral
v
0
Died
7.27
78
51
Occlusion of bowel** Drug intoxication
Bilateral
p
0
Died
7.40
62
34
Evisceration • •
Bilateral
v
12
Lived
•v,
Volume-preset device; and P, pressure-preset device. Type of ventilat<>r and PEEP are those used when pulmonary barotrauma occurred. •• Aspiration in induction of anesthesia. tPatients who also received ventilatory support with other type of ventilator.
receiving ventilatory support with PEEP were excluded ( Fig 1 ) . Pneumothorax, pneumomediastinum, and subcutaneous emphysema occurred after the first hours and up to 34 days of continuous ventilatory support. Pneumothorax occurred on the left side in seven cases and on the right side in seven cases. In three of these 14 cases, pneumomediastinum or subcutaneous emphysema or both were associated with the pneumothorax. Bilateral pneumothorax occurred in six cases and was associated with pneumomediastinum and subcutaneous emphysema in three of them. The two other patients had pneumomediastinum (with subcutaneous emphysema in one of them) . 142 DE LATORRE ET AL
Except for three of the patients, pneumomediastinum and subcutaneous emphysema preceded or occurred simultaneously with the detection of pneumothorax. Patients using volume-cycled devices had an incidence of barotrauma of 9 percent ( 13/139), as compared to 1 percent ( 5/355) of the patients who used pressure-cycled devices ( P < 0.001) and to 7 percent ( 4/59) of the patients in whom both types of machines were used (P > 0.1; not significant). Seventy-three of 553 patients had preexisting pulmonary disease (chronic airway obstruction). Six ( 8 percent) of these 73 patients developed pneumothorax and pneumomediastinum. This incidence is CHEST, 72: 2, AUGUST, 1977
Table
Case, Age 1, 2, 3, 4, 5, 6, 7,
70 34 74 74 21 72 36
8, 32 9, 59 10, 28 11, 16 12,47 13, 18 14, 23 15,66 16, 42
Data /rom Patient. Aapiralion. Pneumonia
~linical
Primary Illness*
Type of Ventilator**
Right lobar pneuPeritonitis; ARDS CAO Bronchopneumonia Bronchopneumonia CAO Right lobar pneumonia Pulmonary involvement of lymphosarcoma CAO Mitral stenosis; pulmonary edema Meningioma; pulmonary edema Mitral stenosis; pulmonary edema Drug intoxication Bronchopneumonia CAO Status asthmaticus
tc~ilhoul
PEEP, em
H,o••
Outcome
v
0 10 0 0 0 0 0
Died Died Died Died Lived Died Died
v
0
Died
v v
0 0
Died Died
v
0
Lived
p
0
Lived
v v
0 8 0 0
Died Died Died Lived
Pt
v
Vt
v v p
p
Pt
*CAO, Chronic airway obstruction; and ARDS, adult respiratory distress syndrome. ••v, Volume-preset device; and P, pressure-preset device. Type of ventilator and PEEP are those used when pulmonary barotrauma occurred. tPatients who also received ventilatory support with other type of ventilator.
higher than the 4 percent ( 18/480) observed in patients with ventilatory support without previous chronic airway obstruction, although this difference was not of statistical significance. None of the 73 patients with chronic airway obstruction received ventilatory support with PEEP. If a fractional concentration of oxygen in the inspired gas ( FI
PATIENTS WITHOUT ASPIRATION PNEUMONIA
~
PATIENTS
WITH
ASPIRATION PNEUMONIA
50
..."'z
"' 0
u
..
40
6/16
30
~
20 10
TOTAL
PATIENTS VENTILATED"
PATIENTS
WITHOUT
PEEP+
• P< 0.001 + P< 0.001
1. Incidence of pneumothorax or pneumomediastinum or both in patients with and without aspiration pneumonia who are receiving ventilatory support. FiGURE
CHEST, 72: 2, AUGUST, 1977
above 60 mm Hg, PEEP was used. This method of ventilation was used in 33 of 553 cases. Five ( 15 percent) of these 33 patients developed pneumothorax or pneumomediastinum or both, and this represents a significant increase in the incidence of barotrauma if we compare it with the patients ventilated without PEEP (3 percent or 17/520) (P < 0.025). · The mortality in 22 patients with barotrauma was 77 percent ( 17I 22); this is a very high value, as compared to the 33 percent ( 180/553) that was the overall mortality in the patients with ventilatory support ( P < 0.001) . DiscuSSION
Positive-pres.sure ventilation may cause alveolar rupture; with the production of pneumothorax, pneumomediastinum, and subsequent subcutaneous emphysema. Although the overpressured airway is the mechanism of alveolar rupture, there are several factors which may predispose to the development of barotrauma. u.s A report has postulated that the use of volumecycled devices may be followed by an increased incidence of iatrogenic pneumothorax,' and we have also observed this in our patients. Patients with more pulmonary damage are generally ventilated with volume-preset ventilators. This factor should be considered in any conclusions that are drawn; however, patients with volume-cycled deviees are exposed to a peak airway pressure higher than those ventilated ·with pressure-cycled devices. Therefore, when volume-cycled ventilators are employed, the highest airway pres.sure should be kept within a range of values where the risk of pneumothorax is minimum. 3 In spite of a recent study which does not report an augmented incidence of barotrauma in patients receiving therapy with PEEP,3 we have found an increased number of cases of pneumothorax and pneumomediastinum in this group, as other investigators have observed.1 We have found a very high incidence of pneumothorax and pneumomediastinum in 16 patients with aspiration pneumonia. In a retrospective study,6 we had already observed an incidence of barotrauma of 27 percent ( 4/ 15) in patients with aspiration pneumonia who were receiving ventilatory support. Nevertheless, we have not found aspiration pneumonia reported as a precipitating factor for barotrauma in ·a review of published studies on pneumothorax and pneumomediastinum during mechanical ventilation.l-4.6-8 This incidence of pneumothorax in patients with aspiration pneumonia, by far higher than that seen in patients receiving ventilatory ther-
PNEUMOTHORAX AND PNEUMOMEDIASnNUM IN ASPIRAnOH PNEUMONIA 143
1
(
apy because of other conditions ( P < 0.001), was still observed when we excluded those patients receiving ventilatory support with PEEP (Fig 1), a treatment that may by itself predispose to the development of pneumothorax. Acute respiratory failure following aspiration of gastric contents is accompanied by a pulmonary injury that extends from the tracheobr~nchial tree to the periphery of the lung, with areas of frank necrosis.&-11 The necrosis of bronchiolar and alveolar walls may predispose to the development of pneumothorax and pneumomediastinum, as in necrotizing pneumonia. 2 If further work confirms· this higher incidence of barotrauma in patients with aspiration pneumonia who are receiving ventilatory support, it will seem reasonable to include these patientS among those at high risk of developing pneumothorax when they are receiving ventilatory therapy. Barotrauma should be carefully sought in these patients, and a thoracostomy tube should be immediately inserted in case of a positive diagnosis. 1 ACKNOWLEDGMENT: We would like to thank Dr. Juan Padro and Dr. Ramon Peracaula for their assistance in the clinical follow-up of the cases, and Dr. Cafetano Pennanyer and Dr. Jaime Guardia for their helpfu revision of this manuscript. REFERENCES
1 Zwillich CW, Pierson DJ, Creagh CE, et al: Complica-
tions of assisted ventilation: A prospective study of 354 consecutive episodes. Am J Med 57:161-170, 1974 2 Fleming WH, Bowen JC, Hatcher CR: Early complications of long-tenn respiratory support. J Thorac Cardi~ vase Surg 64:729-737, 1972 3 Kumar A, Pontoppidan H, Falke KJ, et al: Pulmonary barotrauma during mechanical ventilation. Crit Care Med
1:181-186, 1973
4 Steier M, Ching N, Roberts EB, ell al: Pneumothorax complicating continuous ventilatory support. J Thorac Cardiovasc Surg 67: 17-23, 1974 5 de Latorre FJ, Tomasa A, Klamberg J, et al: Edema pulmonar agudo por inhalacion de contenido gastrico (sindrome de Mendelson). Rev Clin Esp, to be published 6 Zimmerman JE, Dumbar BS, Klingenmaier CH: Management of subcutaneous emphysema, pneumomediastinum and pneumothorax during respiratory therapy. Crit Care Med 3:69-73, 1975 1 Nennhaus HP, Javid H, Julian OC: Alveolar and pleural rupture: Hazards of positive pressure respiration. Arch Surg 94:136-141, 1967 8 Lareng L, Jorda MF, Brouchet A, et al: Les pneum~ thorax sous respirateur artificiel. Anesth Anal (Paris)
29:651-659, 1972 9 Lewinski A: Evaluation of methods employed in the treatment of the chemical pneumonitis of aspiration. Anesthesiology 26:37-44, 1965 10 Alexander IGS : The ultrastructure of the pulmonary alveolar vessels in Mendelson's (acid pulmonary aspiration) syndrome. Br J Anaesth 40:408-414, 1968 11 Toung TJK, Bordos D, Benson DW, et al : Aspiration pneumonia: Experimental evaluation of albumin and steroid therapy. Ann Surg 183:179-184, 1976
Call for Abstracts, International Union Against Tuberculosis The XXIV Conference of the International Union Against Tuberculosis will be held in Brussels, Belgium, September 3-9, 1978. Summaries of proposed presentations (not more than 300 words) should be submitted by September 30, 1977, in quintuplicate, English or French. Send to: International Union Against Tuberculosis, 3 Rue Georges Ville, 65 116 Paris, France.
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