AUSTRALIAN PAEDIATRIC JOURNAL
Aust. paediat. J.
(1975) 11:195 200
Pneumothorax by MARY E. DWYER* f i o m the Department of Anaesthesia, Royal Children’s Hospital, Melbourne. Dwyer, Mary E. (1975). Aust. paediat. J., 11, 195-200. Pneumothorax. Between 1967 and 1973, 112 infants and children with pneumothorax were treated in the Intensive Care Unit at the Royal Children’s Hospital. These are discussed in relation to etiology and management. Particular attention is paid to the effect of prophylactic antibiotics against the virulent Pseudomonas pyocyaneus seen in 1968-69, to the beneficial effects of small catheters for tracheal suction, and to the Stocks ‘bullet’ which obviates the need to interrupt the respirator circuit.
A pneumothorax is a potentially life threatening condition, particularly when the intrapleural air is under tension, as is common in patients receiving positive pressure ventilation. Early diagnosis and prompt treatment are important in reducing morbidity and mortality. Patients and Management This paper reviews 112 children with a pneumothorax treated in the Intensive Care Unit (ICU) between 1967 and 1973. There were two main groups of patients: GROUP 1 The majority were under 3 months of age and the pneumothorax was associated with pulmonary disease and abnormal alveolar aeration. The common causes of abnormality of aeration were: (a) the ‘air-block syndrome’ in which interstitial emphysema is caused by uneven expansion, overdistension and rupture of alveoli (Grosfield, Clatworthy and Frye, 1970);
Received 15 October, 1975 *Staff Anaethetist.
(b) pulmonary infection; and (c) congenital diaphragmatic hernia.
GROUP II These were older children, with a pneumothorax resulting from abnormal pressures applied to normal lungs. Causes included trauma, excessive positive pressure during resuscitation, and air leak from sources other than the lung, e.g. a ruptured oesophagus or a tracheostomy incision. The management of patients requiring intubation included the use of Portex@ nasotracheal tubes, warmed humidified air with supplemental oxygen, and endotracheal suction, usually at half hourly intervals. Tracheal aspirates were cultured daily. Routine antibiotic therapy was introduced in 1969, at a time when virulent infections due to gram-negative organisms, particularly Pseudomonas pyocyaneus, were rife. These organisms have now become less common, and the routine use of antibiotics has been discontinued. Continuous positive airways pressure (CPAP) and continuous positive pressure ventilation (CPPV) have been used in addition to intermittent positive pressure respiration (IPPR) in selected patients since 1970 (Stocks, 1973). Tracheal suction in newborn infants has been carried out with a 5 F.G. suction catheter, instead of a 6 F.G. catheter, since the beginning of 1974.
196
AUSTRALIAN PAEDIATRIC JOURNAL
In patients receiving CPAF’ or CPPV, the catheter was passed into the trachea through a ‘bullet’ device fitted into the respirator circuit (Fig. 1 and 2). This device, designed by John Stocks, allows the introduction of a suction catheter without disconnecting the circuit from the patient.
Fig. 1.
The bullet is a metal cylinder with a central hole that fits snugly into the Y-piece of a Bird@ connector. The diameter of the hole is such as to accept a 5, 6, or 8 F.G. catheter. The rim on the bullet fits against the top of the Bird connector, creating a gas-tight fit. A cap is placed over the hole and removed during suction when the catheter is passed through the bullet into the endotracheal tube. The diagnosis of pneumothorax is based on clinical signs of a shift of the mediastinum to the opposite side, hyper-resonance on percussion, and diminished breath sounds, signs which may be confusing in small infants who are being ventilated, especially if they are paralysed. Apparent abdominal distension may be a sign of a large tension pneumothorax. If there is any reason to suspect a pneumothorax, an erect chest X-ray is taken. Drainage of the pneumothorax is best performed via an intercostal catheter attached to an underwater seal. The catheter is usually inserted in the second intercostal space, in the anterior mid-clavicular line. In the newborn, a more lateral point of insertion may result in the end of the catheter being in the chest wall, and the position of the catheter should be checked by X-rays of the chest taken in two planes. Results The causes of the pneumothorax in the 112 patients studied are shown in Table I; 37 (53%) of
TABLE I Group I
(a) ‘Air-block’ syndrome (b) Pulmonary Infection (c) Diaphragmatic Hernia
No of Patients
Deaths
33 31 6
7 11 4
70
22
-
-
21 11 7 3
7 2 1 1
42 112
33
Group I1
Trauma Positive Pressure Respiration Oesophageal rupture Tracheostomy
Fig. 2.
Total
11
Pneumothorax
Mary E. Dwyer
patients in Group I developed a pneumothorax while in ICU, whereas all but 6 (14%)of Group I1 had a pneumothorax at the time of admission to the unit. These 6 all developed a pneumothorax following rupture of the oesophagus. A tension pneumothorax was common, occurring in 63% of the patients, as shown in X-rays, and listed in Table I1 which shows that the incidence was much higher (97%) in association with positive pressure respiration than in the patients not receiving positive pressure ventilation (47%).
TABLE I1 Incidence of Radiological Evidence of Tension Pneumothorax
Patients receiving CPAP or CPPV Patients not treated with
positive pressure
Tension
No Tension
35(97%)
1 (3%)
36(47%) 40(53%) _ _ _ 71(63%) 41
Group I (a) ‘Air-block’syndrome (33patients, 30%) In this group 29 of the 33 patients were less than 12 days old, and the pneumothorax was most commonly associated with hyaline membrane disease or aspiration pneumonia. In 16 patients the pneumothorax was on the right side; 6 were on the left, and there was a pneumothorax on both sides in 11. Tension pneumothorax occurred in 57% of the 33 patients in this group. The weight on admission was recorded in 22 infants who had no ventilatory assistance before the development of pneumothorax, and only 3 of the 22 weighed less than 3 kg, a proportion similar to others reported (Srouji, 1967; Malan and Heese, 1966).
(b) Pulmonary infection. There were 31 patients (28%) with pulmonary infection. Approximately 2 were admitted each year, except in 1968 and 1973 when there were 10 and 9 respectively. The number of patients, and the mortality related to different infecting organisms, are summarized in Table 111. In all but
197
TABLE 111 Infection Owanism
N o of Datients
Deaths
Miscellaneous
4 6 14 7
1 2 6 2
Total
31
11
Staphylococcus aureus
Klebsiella Pseudomonas pyocyanea
4 patients, the gram-negative pulmonary infection developed while the patient was intubated and ventilated.for another condition, and only 3 of these 4 patients were more than 3 months of age. In 1968, 7 patients developed an infection due to gram-negative organisms; 6 of the 7 died, and Pseudomonas pyocyaneus was the causal organism in 5 patients. At that time prophylactic antibiotic treatment was not given unless a positive bacteriological, identification had been made. Routine administration of prophylactic antibiotics (Carbenicillin@ and/or Gentamkin@) to intubated patients was introduced in the unit in 1969, but has been discontinued as the incidence of gram-negative infections has declined and since 1969 only one death has been associated with infection. Control of infection was the only major change in management at that time. In all but 3 patients the pneumothorax was right sided or bilateral, and this preponderance on the right side has been noted by others (Yu, Liew, Robinson, 1975). The explanation may be that a suction catheter can be forced on into the right lower lobe while attempting to pass it through an endotracheal tube, and an area of traumatized lung may subsequently rupture into the pleural cavity. Recurrence of pleural air, was common in these cases, due to slow closure of the bronchopleural communication.
(c) Congenital diaphragmatic hernia ( 6 patients). Diaphragmatic hernia in the newborn is often associated with hypoplasia of the ipsilateral lung and often also of the contralateral lung. Attempts to produce normal tidal volumes while ventilating these patients can lead to the use of extremely high pressures with consequent rupture of an alveolus into the pleural cavity. The hernia was on the left side in all 6 patients, but a pneumothorax on the right side was the cause of death in 2 patients. It is largely because of the risk of
198 AUSTRALIAN PAEDIATRIC JOURNAL
rupturing the contralateral (‘good’) lung that it is preferable t o . transfer these patients to a specialized centre without intubating them, but providing supplemental oxygen en route. Trauma Table IV shows the causes of pneumothorax following trauma in 2 1 patients (19%), almost all of whom were pedestrians struck by a motor vehicle. All of them sustained multiple injuries such as fractured ribs, contusions of the underlying lung and brain injury. 3 patients who were given an intracaxdiac injection of adrenaline during resuscitation for cardiac arrest all developed a left sided penumothorax, suggesting that needle puncture was the etiological factor. One girl ruptured her trachea when she fell on to a garden tap. She developed bilateral pneumothoraces with extensive surgical emphysema, and recovered after intubation and tracheal repair. TABLE IV
(21 patients) Post - Traumatic Pneumothorax Cause of trauma
N o of patients
Vehicle accident Intracardiac injection of adrenaline Blunt trauma to neck
Deaths
17
4
3 1
-
3
7 -
21
-
Positive Pressure Respiration Excessive positive pressure applied to patients with normal lungs was responsible for the development of a pneumothorax in 11 patients, and in 1 0 of them there was radiological evidence of tension. A pneumothorax sometimes occurs during resuscitation for respiratory or cardiac arrest. The causes of a pneumothorax occurring during
anaesthesia were a sandbag occluding the expiratory limb of a T-piece in one, and in the other a soft endotracheal tube became kinked. Oesophageal rupture Rupture of the oesophagus, with leakage of the oesophageal contents and mediastinitis spreading into the pleural cavity, may lead to a pneumothorax when air is swallowed and reaches the pleural cavity. One patient aged 2 days presented with a pneumothorax secondary to rupture of the oesophagus following two episodes of vomiting, and recovered. In 6 patients, oesophageal atresia had been repaired, but leakage at the anastomosis lead to a right sided pneumothorax. One death occurred in this group, in an infant with a hypoplastic left ventricle. Tracheostomy 3 patients developed a pneumothorax following tracheostomy. The apical pleura may be damaged during the initial dissection, especially when the incision is low, or alternatively air may enter the mediastinum from an open neck wound, and then rupture into the pleural cavity. Intercostal ccrtheters Mismanagement of an intercostal drain tube may cause a pneumothorax, e.g. if the end of the intended underwater seal is not below the level of the fluid, or if the tubing becomes disconnected, or the dressing around the tube, where it emerges from the skin, is not occlusive. An underwater drainage system may be incorrectly connected so that the end of the pleural tube is above the water but the outlet is below the water level, thus leading to a tension pneumothorax from obstruction of the outlet. CPAP and CPPV The diagnosis and the mortality rates of the two groups of newborn infants managed with CPAP or CPPV in 1973 and 1 9 7 4 are summarized in Table V. In .1973, 11 patients (47%) developed a
TABLE V Diagnosis Year
Age
1973 1974
1-6 days 1-8 days
Aspiration Pneumonia
5 4
H.M.D.
Apnoea
Total
Deaths
16 17
2 6
23 27
7 3
Mary E. Dwyer
F’neumothorax
pneumothorax, 10 of them while receiving CPAP or CPPV. In 1974, there were 8 cases (30%), only one of which occurred after admission to ICU, and in that instance the pneumothorax was detected soon after thoracotomy for ligation of a patent ductus arteriosus. The results are summarized in Table Vl, in which incidence of pneumothorax in this group, and the duration of CPAP or CPPV, are set out. Discussion Morbidity and mortality from a pneumothorax present at the time of admission to ICU can be reduced by careful management. Control of infection, reduction in cross-infection, and prophylactic antibiotic therapy when indicated, have reduced the mortality significantly. A pneumothorax occurs when the endobronchial or alveolar pressure is sufficient to ivpture an alveolus, causing air to escape into the pleural cavity. Rosen (1970) described experimental evidence which showed that the newborn human lung can be distended to 35 cm H 2 0 with rupture occurring in only 4% of cases. Pulmonary disease causing unequal aeration of the alveoli may cause a ‘ball-valve’ effect resulting in alveolar rupture at one site (Chernick and Avery 1963; Grosfeld, Clatworthy and Frye, 1970). In these circumstances the pressure in the ruptured alveolus could be higher than 35 cm H20, although the pressure in the trachea may be lower. The high pressure required to cause a rupture probably explains the low incidence of spontaneous pneumothorax in low birth weight infants (Malan and Heese,1966). The introduction of the ‘bullet’, and the use of smaller catheters for pertubal suction, was associated with a marked reduction in pneumothorax in infants in 1974 (Table VI).
Tracheal suction in infants, if prolonged or performed with high negative pressure through a relatively large catheter, can lead to atelectasis and hypoxaemia (Brandstater and Muallen, 1969), and this appears to be associated with a higher incidence of neonatal pneumothorax. The Stocks ‘bullet’ obviates the need to interrupt the circuit and helps to reduce these complications. Control of suction pressure, sucking only as the catheter is being withdrawn, and using a catheter of appropriate diameter, all tend to minimize the adverse effects of suction. The external diameter of the suction catheter relative to the minimum internal diameter of the airway should be 50-60% (Poole, Abrahams and Fisk, 1974). Care in the selection and positioning of endotracheal tubes, and the use of the lowest reasonable inflating pressure in patients receiving assisted ventilation, will help to prevent the development of a pneumothorax. Low gas flows, especially in newborn infants, will prevent the development of excessive pressure during inspiration delivered by manual ventilation (Oztalay and Beard, 1963). Faulty technique is the most common cause of a pneumothorax in a patient with normal lungs. Diagnosis of a pneumothorax depends primarily on an awareness that it is a possible complication, and the diagnosis should be anticipated when treating a condition known to predispose to its occurrence, or when unexplained hypoxia develops suddenly. A pneumothorax should also be considered when an intubated patient receiving positive pressure ventilation becomes difficult to ventilate despite attention t o the airway. Management of pneumothorax depends upon the degee of respiratory distress. If this is minor, removal of the pleural air may not be required, but in almost all patients drainage is required to prevent progressive accumulation of air. A large
TABLE VI Incidence of Pneumothorax in Infants o n CPAP or CPPV Duration of CPAP or CPPR
1-5days 6-10 days 1 O+ days
Total No. of Neonates on CPAP or CPPR
1973
12 5 6
1974 21
No. of Pneumothoraces On Admission to ICU Developed in ICU 1973
1974
1973
1974
6 1 0
2 3
0 0 1
-
1
1 0 0
-
-
-
-
23
27
1
7
10
-
-
-
5
-
199
-
5
-
1
-_
200
AUSTRALIAN PAEDIATRIC JOURNAL
pneumothorax leads to a fall in Pa02, and may also cause a rise in intrathoracic pressure, obstructing the venous return and thus decreasing cardiac output. A significant leak of air from the lungs into the pleural space and thence along an intercostal drain, increases the dead space and the degree of respiratory distress, so that intubation and ventilation may be required, even if it was unnecessary before the development of the pneumo thorax. Conclusions
A pneumothorax is a potentially life-threatening complication of several diseases, and also IPPR and CPAP. The diagnosis may be difficult, especially in infants. In some circumstances, rapid diagnosis and urgent treatment are essential. When kept in mind, a pneumothorax may be either prevented or treated effectively, and in the majority of cases its occurrence should make little difference to the ultimate outcome. During the period under review, the introduction in 1969 of prophylactic antibiotics for intubated patients led to a reduction in the mortality from gram-negative infections which were prevalent at that time. The maintenance of positive pressure and a constant tension of oxygen in inspired air during suction, by use of the ‘bullet’ devised by John Stocks in 1973, and the use of smaller catheters, has been associated with a decreased incidence of pneumothorax in infants treated in the Intensive Care Unit.
REFERENCES Brandstater, B. and Muallen, M. (1969). Atelectasis following tracheal suction in infants. Amesthesiology, 31 : 468. Chemick, V. and Avery, M.E. (1963). Spontaneous Alveolar Rupture at-Birth. Pediatrics, 32 : 816. Grosfeld, J.L., Clatworth, H.W. and Frye, T.R. (1970). Surgical therapy in neonatal airblock syndrome. J. Thor. and Cardiovasc. Surg. 60 : 392-401. Malan, A.F. and Heese, H. de V (1966). Spontaneous pneumothorax in the newborn. Acta Paediatrica Scandanavica, 55 : 224-228. Oztalay, A.G. and Beard, A.G. (1963). Tension pneumothorax: Possible etiologic role of high intratracheal pressure. J. Paed 63 : 530-6. Poole, J.L., Abrahams, N. and Fisk, G.C. (1974). Endotracheal suction. Anaesthesia and Intensive Care. 2 : 131-141. Rosen, M., Lawrence, K.M., and Mapleson, W.W. (1973). Artificial expansion of the newborn human lung. Brit. J . Anaes. 45 : 535-545. Srouji, M.N. (1967). Pneumothorax and Pneumomediastinum in the first three davs of life. I. Pediatric Surgery. 2 : 410-418. Stocks, J.G. (1973). The Management of Respiratory Failure in Infancy. Anaesthesia and Intensive Care. 1 : 486-506. Yu, V.Y.H., Liew, S.W. and Roberton, N.R.C. (1975). Pneumothorax in the Newborn. Arch. Dis. Childhood, 50 : 449-453.
Acknowledgement This review was initiated by the late Dr. J.G. Stocks who was working with the author on it when his untimely death occurred. The review has been completed, and it is hoped that this paper conveys some of John Stocks’ ideas and innovations, which have helped to reduce morbidity and mortality from pneumothorax.
afl-pndenceto: ~ ~ p ~ & ~ ~ ~ ~ n a e s t h e s i a , ~ ~Children’s ~ aHospital, l Parkville, Vic. 3052.
Aust. paediat. J.
(1975) 11:195 200
Pneumothorax by MARY E. DWYER* f i o m the Department of Anaesthesia, Royal Children’s Hospital, Melbourne. Dwyer, Mary E. (1975). Aust. paediat. J., 11, 195-200. Pneumothorax. Between 1967 and 1973, 112 infants and children with pneumothorax were treated in the Intensive Care Unit at the Royal Children’s Hospital. These are discussed in relation to etiology and management. Particular attention is paid to the effect of prophylactic antibiotics against the virulent Pseudomonas pyocyaneus seen in 1968-69, to the beneficial effects of small catheters for tracheal suction, and to the Stocks ‘bullet’ which obviates the need to interrupt the respirator circuit.
A pneumothorax is a potentially life threatening condition, particularly when the intrapleural air is under tension, as is common in patients receiving positive pressure ventilation. Early diagnosis and prompt treatment are important in reducing morbidity and mortality. Patients and Management This paper reviews 112 children with a pneumothorax treated in the Intensive Care Unit (ICU) between 1967 and 1973. There were two main groups of patients: GROUP 1 The majority were under 3 months of age and the pneumothorax was associated with pulmonary disease and abnormal alveolar aeration. The common causes of abnormality of aeration were: (a) the ‘air-block syndrome’ in which interstitial emphysema is caused by uneven expansion, overdistension and rupture of alveoli (Grosfield, Clatworthy and Frye, 1970);
Received 15 October, 1975 *Staff Anaethetist.
(b) pulmonary infection; and (c) congenital diaphragmatic hernia.
GROUP II These were older children, with a pneumothorax resulting from abnormal pressures applied to normal lungs. Causes included trauma, excessive positive pressure during resuscitation, and air leak from sources other than the lung, e.g. a ruptured oesophagus or a tracheostomy incision. The management of patients requiring intubation included the use of Portex@ nasotracheal tubes, warmed humidified air with supplemental oxygen, and endotracheal suction, usually at half hourly intervals. Tracheal aspirates were cultured daily. Routine antibiotic therapy was introduced in 1969, at a time when virulent infections due to gram-negative organisms, particularly Pseudomonas pyocyaneus, were rife. These organisms have now become less common, and the routine use of antibiotics has been discontinued. Continuous positive airways pressure (CPAP) and continuous positive pressure ventilation (CPPV) have been used in addition to intermittent positive pressure respiration (IPPR) in selected patients since 1970 (Stocks, 1973). Tracheal suction in newborn infants has been carried out with a 5 F.G. suction catheter, instead of a 6 F.G. catheter, since the beginning of 1974.
196
AUSTRALIAN PAEDIATRIC JOURNAL
In patients receiving CPAF’ or CPPV, the catheter was passed into the trachea through a ‘bullet’ device fitted into the respirator circuit (Fig. 1 and 2). This device, designed by John Stocks, allows the introduction of a suction catheter without disconnecting the circuit from the patient.
Fig. 1.
The bullet is a metal cylinder with a central hole that fits snugly into the Y-piece of a Bird@ connector. The diameter of the hole is such as to accept a 5, 6, or 8 F.G. catheter. The rim on the bullet fits against the top of the Bird connector, creating a gas-tight fit. A cap is placed over the hole and removed during suction when the catheter is passed through the bullet into the endotracheal tube. The diagnosis of pneumothorax is based on clinical signs of a shift of the mediastinum to the opposite side, hyper-resonance on percussion, and diminished breath sounds, signs which may be confusing in small infants who are being ventilated, especially if they are paralysed. Apparent abdominal distension may be a sign of a large tension pneumothorax. If there is any reason to suspect a pneumothorax, an erect chest X-ray is taken. Drainage of the pneumothorax is best performed via an intercostal catheter attached to an underwater seal. The catheter is usually inserted in the second intercostal space, in the anterior mid-clavicular line. In the newborn, a more lateral point of insertion may result in the end of the catheter being in the chest wall, and the position of the catheter should be checked by X-rays of the chest taken in two planes. Results The causes of the pneumothorax in the 112 patients studied are shown in Table I; 37 (53%) of
TABLE I Group I
(a) ‘Air-block’ syndrome (b) Pulmonary Infection (c) Diaphragmatic Hernia
No of Patients
Deaths
33 31 6
7 11 4
70
22
-
-
21 11 7 3
7 2 1 1
42 112
33
Group I1
Trauma Positive Pressure Respiration Oesophageal rupture Tracheostomy
Fig. 2.
Total
11
Pneumothorax
Mary E. Dwyer
patients in Group I developed a pneumothorax while in ICU, whereas all but 6 (14%)of Group I1 had a pneumothorax at the time of admission to the unit. These 6 all developed a pneumothorax following rupture of the oesophagus. A tension pneumothorax was common, occurring in 63% of the patients, as shown in X-rays, and listed in Table I1 which shows that the incidence was much higher (97%) in association with positive pressure respiration than in the patients not receiving positive pressure ventilation (47%).
TABLE I1 Incidence of Radiological Evidence of Tension Pneumothorax
Patients receiving CPAP or CPPV Patients not treated with
positive pressure
Tension
No Tension
35(97%)
1 (3%)
36(47%) 40(53%) _ _ _ 71(63%) 41
Group I (a) ‘Air-block’syndrome (33patients, 30%) In this group 29 of the 33 patients were less than 12 days old, and the pneumothorax was most commonly associated with hyaline membrane disease or aspiration pneumonia. In 16 patients the pneumothorax was on the right side; 6 were on the left, and there was a pneumothorax on both sides in 11. Tension pneumothorax occurred in 57% of the 33 patients in this group. The weight on admission was recorded in 22 infants who had no ventilatory assistance before the development of pneumothorax, and only 3 of the 22 weighed less than 3 kg, a proportion similar to others reported (Srouji, 1967; Malan and Heese, 1966).
(b) Pulmonary infection. There were 31 patients (28%) with pulmonary infection. Approximately 2 were admitted each year, except in 1968 and 1973 when there were 10 and 9 respectively. The number of patients, and the mortality related to different infecting organisms, are summarized in Table 111. In all but
197
TABLE 111 Infection Owanism
N o of Datients
Deaths
Miscellaneous
4 6 14 7
1 2 6 2
Total
31
11
Staphylococcus aureus
Klebsiella Pseudomonas pyocyanea
4 patients, the gram-negative pulmonary infection developed while the patient was intubated and ventilated.for another condition, and only 3 of these 4 patients were more than 3 months of age. In 1968, 7 patients developed an infection due to gram-negative organisms; 6 of the 7 died, and Pseudomonas pyocyaneus was the causal organism in 5 patients. At that time prophylactic antibiotic treatment was not given unless a positive bacteriological, identification had been made. Routine administration of prophylactic antibiotics (Carbenicillin@ and/or Gentamkin@) to intubated patients was introduced in the unit in 1969, but has been discontinued as the incidence of gram-negative infections has declined and since 1969 only one death has been associated with infection. Control of infection was the only major change in management at that time. In all but 3 patients the pneumothorax was right sided or bilateral, and this preponderance on the right side has been noted by others (Yu, Liew, Robinson, 1975). The explanation may be that a suction catheter can be forced on into the right lower lobe while attempting to pass it through an endotracheal tube, and an area of traumatized lung may subsequently rupture into the pleural cavity. Recurrence of pleural air, was common in these cases, due to slow closure of the bronchopleural communication.
(c) Congenital diaphragmatic hernia ( 6 patients). Diaphragmatic hernia in the newborn is often associated with hypoplasia of the ipsilateral lung and often also of the contralateral lung. Attempts to produce normal tidal volumes while ventilating these patients can lead to the use of extremely high pressures with consequent rupture of an alveolus into the pleural cavity. The hernia was on the left side in all 6 patients, but a pneumothorax on the right side was the cause of death in 2 patients. It is largely because of the risk of
198 AUSTRALIAN PAEDIATRIC JOURNAL
rupturing the contralateral (‘good’) lung that it is preferable t o . transfer these patients to a specialized centre without intubating them, but providing supplemental oxygen en route. Trauma Table IV shows the causes of pneumothorax following trauma in 2 1 patients (19%), almost all of whom were pedestrians struck by a motor vehicle. All of them sustained multiple injuries such as fractured ribs, contusions of the underlying lung and brain injury. 3 patients who were given an intracaxdiac injection of adrenaline during resuscitation for cardiac arrest all developed a left sided penumothorax, suggesting that needle puncture was the etiological factor. One girl ruptured her trachea when she fell on to a garden tap. She developed bilateral pneumothoraces with extensive surgical emphysema, and recovered after intubation and tracheal repair. TABLE IV
(21 patients) Post - Traumatic Pneumothorax Cause of trauma
N o of patients
Vehicle accident Intracardiac injection of adrenaline Blunt trauma to neck
Deaths
17
4
3 1
-
3
7 -
21
-
Positive Pressure Respiration Excessive positive pressure applied to patients with normal lungs was responsible for the development of a pneumothorax in 11 patients, and in 1 0 of them there was radiological evidence of tension. A pneumothorax sometimes occurs during resuscitation for respiratory or cardiac arrest. The causes of a pneumothorax occurring during
anaesthesia were a sandbag occluding the expiratory limb of a T-piece in one, and in the other a soft endotracheal tube became kinked. Oesophageal rupture Rupture of the oesophagus, with leakage of the oesophageal contents and mediastinitis spreading into the pleural cavity, may lead to a pneumothorax when air is swallowed and reaches the pleural cavity. One patient aged 2 days presented with a pneumothorax secondary to rupture of the oesophagus following two episodes of vomiting, and recovered. In 6 patients, oesophageal atresia had been repaired, but leakage at the anastomosis lead to a right sided pneumothorax. One death occurred in this group, in an infant with a hypoplastic left ventricle. Tracheostomy 3 patients developed a pneumothorax following tracheostomy. The apical pleura may be damaged during the initial dissection, especially when the incision is low, or alternatively air may enter the mediastinum from an open neck wound, and then rupture into the pleural cavity. Intercostal ccrtheters Mismanagement of an intercostal drain tube may cause a pneumothorax, e.g. if the end of the intended underwater seal is not below the level of the fluid, or if the tubing becomes disconnected, or the dressing around the tube, where it emerges from the skin, is not occlusive. An underwater drainage system may be incorrectly connected so that the end of the pleural tube is above the water but the outlet is below the water level, thus leading to a tension pneumothorax from obstruction of the outlet. CPAP and CPPV The diagnosis and the mortality rates of the two groups of newborn infants managed with CPAP or CPPV in 1973 and 1 9 7 4 are summarized in Table V. In .1973, 11 patients (47%) developed a
TABLE V Diagnosis Year
Age
1973 1974
1-6 days 1-8 days
Aspiration Pneumonia
5 4
H.M.D.
Apnoea
Total
Deaths
16 17
2 6
23 27
7 3
Mary E. Dwyer
F’neumothorax
pneumothorax, 10 of them while receiving CPAP or CPPV. In 1974, there were 8 cases (30%), only one of which occurred after admission to ICU, and in that instance the pneumothorax was detected soon after thoracotomy for ligation of a patent ductus arteriosus. The results are summarized in Table Vl, in which incidence of pneumothorax in this group, and the duration of CPAP or CPPV, are set out. Discussion Morbidity and mortality from a pneumothorax present at the time of admission to ICU can be reduced by careful management. Control of infection, reduction in cross-infection, and prophylactic antibiotic therapy when indicated, have reduced the mortality significantly. A pneumothorax occurs when the endobronchial or alveolar pressure is sufficient to ivpture an alveolus, causing air to escape into the pleural cavity. Rosen (1970) described experimental evidence which showed that the newborn human lung can be distended to 35 cm H 2 0 with rupture occurring in only 4% of cases. Pulmonary disease causing unequal aeration of the alveoli may cause a ‘ball-valve’ effect resulting in alveolar rupture at one site (Chernick and Avery 1963; Grosfeld, Clatworthy and Frye, 1970). In these circumstances the pressure in the ruptured alveolus could be higher than 35 cm H20, although the pressure in the trachea may be lower. The high pressure required to cause a rupture probably explains the low incidence of spontaneous pneumothorax in low birth weight infants (Malan and Heese,1966). The introduction of the ‘bullet’, and the use of smaller catheters for pertubal suction, was associated with a marked reduction in pneumothorax in infants in 1974 (Table VI).
Tracheal suction in infants, if prolonged or performed with high negative pressure through a relatively large catheter, can lead to atelectasis and hypoxaemia (Brandstater and Muallen, 1969), and this appears to be associated with a higher incidence of neonatal pneumothorax. The Stocks ‘bullet’ obviates the need to interrupt the circuit and helps to reduce these complications. Control of suction pressure, sucking only as the catheter is being withdrawn, and using a catheter of appropriate diameter, all tend to minimize the adverse effects of suction. The external diameter of the suction catheter relative to the minimum internal diameter of the airway should be 50-60% (Poole, Abrahams and Fisk, 1974). Care in the selection and positioning of endotracheal tubes, and the use of the lowest reasonable inflating pressure in patients receiving assisted ventilation, will help to prevent the development of a pneumothorax. Low gas flows, especially in newborn infants, will prevent the development of excessive pressure during inspiration delivered by manual ventilation (Oztalay and Beard, 1963). Faulty technique is the most common cause of a pneumothorax in a patient with normal lungs. Diagnosis of a pneumothorax depends primarily on an awareness that it is a possible complication, and the diagnosis should be anticipated when treating a condition known to predispose to its occurrence, or when unexplained hypoxia develops suddenly. A pneumothorax should also be considered when an intubated patient receiving positive pressure ventilation becomes difficult to ventilate despite attention t o the airway. Management of pneumothorax depends upon the degee of respiratory distress. If this is minor, removal of the pleural air may not be required, but in almost all patients drainage is required to prevent progressive accumulation of air. A large
TABLE VI Incidence of Pneumothorax in Infants o n CPAP or CPPV Duration of CPAP or CPPR
1-5days 6-10 days 1 O+ days
Total No. of Neonates on CPAP or CPPR
1973
12 5 6
1974 21
No. of Pneumothoraces On Admission to ICU Developed in ICU 1973
1974
1973
1974
6 1 0
2 3
0 0 1
-
1
1 0 0
-
-
-
-
23
27
1
7
10
-
-
-
5
-
199
-
5
-
1
-_
200
AUSTRALIAN PAEDIATRIC JOURNAL
pneumothorax leads to a fall in Pa02, and may also cause a rise in intrathoracic pressure, obstructing the venous return and thus decreasing cardiac output. A significant leak of air from the lungs into the pleural space and thence along an intercostal drain, increases the dead space and the degree of respiratory distress, so that intubation and ventilation may be required, even if it was unnecessary before the development of the pneumo thorax. Conclusions
A pneumothorax is a potentially life-threatening complication of several diseases, and also IPPR and CPAP. The diagnosis may be difficult, especially in infants. In some circumstances, rapid diagnosis and urgent treatment are essential. When kept in mind, a pneumothorax may be either prevented or treated effectively, and in the majority of cases its occurrence should make little difference to the ultimate outcome. During the period under review, the introduction in 1969 of prophylactic antibiotics for intubated patients led to a reduction in the mortality from gram-negative infections which were prevalent at that time. The maintenance of positive pressure and a constant tension of oxygen in inspired air during suction, by use of the ‘bullet’ devised by John Stocks in 1973, and the use of smaller catheters, has been associated with a decreased incidence of pneumothorax in infants treated in the Intensive Care Unit.
REFERENCES Brandstater, B. and Muallen, M. (1969). Atelectasis following tracheal suction in infants. Amesthesiology, 31 : 468. Chemick, V. and Avery, M.E. (1963). Spontaneous Alveolar Rupture at-Birth. Pediatrics, 32 : 816. Grosfeld, J.L., Clatworth, H.W. and Frye, T.R. (1970). Surgical therapy in neonatal airblock syndrome. J. Thor. and Cardiovasc. Surg. 60 : 392-401. Malan, A.F. and Heese, H. de V (1966). Spontaneous pneumothorax in the newborn. Acta Paediatrica Scandanavica, 55 : 224-228. Oztalay, A.G. and Beard, A.G. (1963). Tension pneumothorax: Possible etiologic role of high intratracheal pressure. J. Paed 63 : 530-6. Poole, J.L., Abrahams, N. and Fisk, G.C. (1974). Endotracheal suction. Anaesthesia and Intensive Care. 2 : 131-141. Rosen, M., Lawrence, K.M., and Mapleson, W.W. (1973). Artificial expansion of the newborn human lung. Brit. J . Anaes. 45 : 535-545. Srouji, M.N. (1967). Pneumothorax and Pneumomediastinum in the first three davs of life. I. Pediatric Surgery. 2 : 410-418. Stocks, J.G. (1973). The Management of Respiratory Failure in Infancy. Anaesthesia and Intensive Care. 1 : 486-506. Yu, V.Y.H., Liew, S.W. and Roberton, N.R.C. (1975). Pneumothorax in the Newborn. Arch. Dis. Childhood, 50 : 449-453.
Acknowledgement This review was initiated by the late Dr. J.G. Stocks who was working with the author on it when his untimely death occurred. The review has been completed, and it is hoped that this paper conveys some of John Stocks’ ideas and innovations, which have helped to reduce morbidity and mortality from pneumothorax.
afl-pndenceto: ~ ~ p ~ & ~ ~ ~ ~ n a e s t h e s i a , ~ ~Children’s ~ aHospital, l Parkville, Vic. 3052.
