The causes of death of 550 infants and children dying in hospital over a ten year period were analysed as a prelude to the main study. Serial measurements of blood gas tensions and pH were made in 50 children with acute lower respiratory tract infections, 21 with acute asthma, 25 with cystic fibrosis, and 23 newly born infants in the first hour of life. Arterial blood lactate and pyruvate concentrations were measured in 35 children with acute or chronic hypoxaemia. The effects of treatment, particularly oxygen and alkali therapy on these variables were investigated. Measurements were also made of the concentrations of oxygen attainable in tents and incubators, tested under ideal, and routine working conditions.
The analysis of deaths shows that respiratory disorders, particularly pneumonia, account for approximately 25 per cent of 'medical' deaths in hospital. The main conclusions, in answer to the questions posed in Section I, p. 7, are enumerated:
1. Hypoxaemia, an increase in carbon dioxide retention and metabolic acidosis are commonly present in acute lower respiratory tract infections and severe acute asthma. In cystic fibrosis, an increase in Pco2, often well compensated, occurs only in the late stages of the disease.
2. Clinical signs are unreliable as estimates of Po2, Pco2 and pH in acute respiratory illnesses. In cystic fibrosis there is a good relation between the clinical 'grade' in groups of patients and arterial oxygen tension. There are, however, no reliable methods of predicting blood gas tensions in individual patients.
3. Metabolic acidosis in acute respiratory disorders is due, at least in part, to the accumulation of lactic acid. Measurements of blood lactate and lactate /pyruvate ratio as indices of hypoxia are of limited value in routine clinical practice.
4. In acute lower respiratory tract infections and acute asthma hypoxaemia is not invariably relieved by the administration of 40 per cent oxygen. There appears to be no danger of producing CO2 narcosis with oxygen in acute respiratory infections. During exacerbations of infection in cystic fibrosis and in severe asthma with ventilatory failure, however, oxygen is potentially hazardous.
5. The administration of sodium bicarbonate is of value in the treatment of severe respiratory failure in asthma, and is an important adjunct to intermittent positive pressure respiration (IPPR) in the manage- ment of asphyxiated newly born infants.
6. In acute respiratory infections in infancy a Pco2 above 65 mm Hg and pH below 7.20 are of grave prognostic significance in the absence of prompt treatment. In cystic fibrosis sustained hypercapnia is usually a terminal occurrence.
7. Therapeutic concentrations of oxygen in tents are often difficult to maintain in routine practice.
