Basic and Clinical Studies on Mouth Occlusion Pressure in Healthy Subjects and Patients with Pulmonary and Muscular Diseases

Mouth occlusion pressure was studied in 197 healthy subjects classed by age and sex group, and in patients with various diseases. Among the patients, there were 10 patients with fibrosing lung disease, 10 patients with pulmonary emphysema, 27 patients with chronic bronchitis, 48 patients with pneumoconiosis and 49 patients with Duchenne's muscular dystrophy. The following results were obtained.

1. There was no difference in the relationship of alveolar Pco2 to P0.1 when rebreathing was performed using a 100 % O2 or a mixture of 7 % CO2, 50 % O2 and balance with N2 as the initial gas. In the study of 18 healthy subjects, two different types of relationship between alveolar Pco2 and P0.1, namely linear and exponential relationship were observed.

2. There was a significant decrease in functional residual capacity in the supine position in comparison with the sitting position in 15 healthy males studied, but there was no change in the values of P0.1 during room air breathing at rest between the two positions.

3. The mean values and standard deviations of P0.1 in healthy adults and healthy children were 1.61±0.13 cmH2O and 2.87 ±0.38 cmH2O respectively. No difference by sex could be observed.

4. In comparison with the healthy subjects, a significant increase of P0.1 (P<0.001) was observed in patients with fibrosing lung disease, pulmonary emphysema, chronic bronchitis and patients with pneumoconiosis.

5. In comparison with the healthy subjects, the P0.1 decreased significantly (P<0.001) in patients with Duchenne's muscular dystrophy for both adults' and children's groups.

6. The rebreathing is a valuable method for obtaining the ventilatory curve to CO2, and the P0.1 is a simple method which can be used clinically to evaluate the neural activity of the respiratory center.