Pneumothorax in the newborn has a significant mortality and morbidity. Early diagnosis would be likely to improve the outlook. Forty-two consecutive cases of pneumothorax that developed after admission to a tertiary referral neonatal medical intensive care unit over 4 y from 1993 to 1996 were reviewed. The time of onset of the pneumothorax was determined by retrospective evaluation of the computerized trend of transcutaneous carbon dioxide (tcpCO 2 ) and oxygen tensions. The timing of the occurrence in the notes and x-rays determined the time of clinical diagnosis noted at the time. The difference was the time the condition was undiagnosed. The overall mortality before discharge was 45% (19cases), four patients succumbing within 2 h. The median time (range) between onset of pneumothorax and clinical diagnosis was 127 min (45-660 min). In most cases, the endotracheal tube was aspirated and the transcutaneous blood gas sensor was repositioned, and in at least 40% of the cases, the baby was reintubated before the diagnosis was made. Reference centiles were constructed for level of tcpCO 2 and slope of the trended tcpCO 2 over various time intervals (in minutes) from 729 infants from 23 to 42 wk gestation who needed intensive care during the first 7 d of life from the same time period. The 5-min tcpCO 2 trend slopes were compared in index and matched control infants. The presence of five consecutive and overlapping 5-min slopes greater than the 90th centile showed good discrimination for a pneumothorax (area under the receiver operating characteristic curve, 89%). We concluded that 1) the clinical diagnosis of pneumothorax was late, occurring when infants decompensate; 2) trend monitoring of tcpCO 2 might allow the diagnosis to be made earlier if used properly; and 3) use of reference centiles of the trended slopes of tcpCO 2 might be used for automatic decision support in the future. Abbreviations tcpCO 2 , transcutaneous carbon dioxide tension tcpO 2 , transcutaneous oxygen tension FiO 2 , fraction of inspired oxygen ROC, receiver operating characteristic AUC, area under the curve A pneumothorax is a life-threatening complication of ventilatory assistance in the neonatal unit and has a high mortality (1, 2) and morbidity (3) Pneumothoraces are generally thought to develop rapidly. They are usually diagnosed once the infant has decompensated sufficiently to make it obvious that there is a serious clinical problem. Under these circumstances, it may be only a short period before the baby is critically ill because of the development of tension within the thoracic cavity. This problem is becoming less common, but this may mean that junior medical and nursing staff caring for these infants have become less familiar with the condition. As a consequence, the diagnosis may be made even later in the clinical course and the staff may have less skill in the emergency treatment. It is probable that the earlier a pneumothorax is drained, the less damage will occur from hypoxia, hypercarbia, and venous and arterial pressure chan...
