HYPOXIC VENTILATORY RESPONSES AND GAS-EXCHANGE IN PATIENTS WITH PARKINSONS-DISEASE

Ventilatory responses to isocapnic, progressive hypoxic rebreathing (H VR), in supine and sitting positions, lung ventilation and gas exchang e while breathing air and during 5 min of breathing 11% O-2 in N-2 wer e studied in 12 healthy young (20-28 years), 5 old (57-73 years) male subjects, and in 7 male patients with Parkinson's disease (PD) aged 55 -67 years. The piecewise linear approximation technique was used for e valuation of the ventilatory response curves, which allowed a separate analysis of slopes during minor and severe hypoxia. It has been shown that body position affected HVR. In the range of PETO2 from 60 to 35 mm Hg, the ventilatory response in the sitting position was higher tha n supine: in young persons by 43%, in healthy old persons by 76%, and in the PD patients by 211%. No significant differences in HVR to minor hypoxia (PETO2 from 100 to 60 mm Hg) were found in the 3 groups. Duri ng severe hypoxia (PETO2 from 60 to 35 mm Hg) the slope of minute vent ilation versus O-2 was 4.6 (supine) and 2.6 (sitting) times greater in healthy old men than PD patients' slopes. PD patients compared to old controls had 32% lower alveolar ventilation, 10% lower PETO2 and 15% elevation of PETCO2 while breathing air; similar differences were foun d while the patients were breathing 11% O-2. The reduced alveolar vent ilation under severe hypoxia in patients with PD could not be attribut ed to mechanical restriction of lung function. We suggest that the dis crepancy in HVR under minor and severe hypoxia results from dysfunctio n in chemoreception associated with Parkinsonism.