[Effects of hypopressure on blood gases and spirograms of patients suffering from chronic respiratory failure].

We examined the effects of hypopressure on blood gases and spirograms of patients suffering from chronic respiratory failure, and compared them with those of normal subjects, using the environmental control unit (ECU). The patients consisted of 2 with idiopathic interstitial pneumonia (IIP), 1 with pulmonary fibrosis due to RA, 3 with bronchiectasis, 2 with chronic bronchitis and 1 with diffuse panbronchiolitis (DPB). We examined their blood gases and spirograms under the condition of 760 mmHg pressure, 25 degrees C temperature and 60% humidity. Then the pressure of ECU decreased to 670 mmHg in 20 minutes, while the temperature and humidity were kept the same. The patients stayed in the hypopressured ECU for 1 hour, and were reexamined. The pressure of 670 mmHg is that of an altitude of about 1,000 m and that of the cabin pressure of commercial aircraft flying at about 9,000 m. The PaO2 of the patients decreased from 74.7 +/- 13.8 torr to 61.8 +/- 9.5 torr significantly. We found, however, the significant decrease of PaO2 in normal subjects from 97.2 +/- 7.8 torr to 80.4 +/- 6.5 torr under the same conditions. The rates of the decreased gases were almost same in both groups. Some patients showed remarkable decreases in VC and FEV1.0 under the hypopressure. No patients or control subject complained of subjective symptoms.