Effect of oxygen on sleep and breathing in patients with interstitial lung disease at moderate altitude

To investigate the impact of oxygen on sleep and breathing in patients with interstitial lung disease (ILD) in Mexico City, at 2,240 m of altitude.

Nineteen ILD patients with a mean FVC of 58 +/- 17% pred. (SD) and a mean PaO(2) of 51 +/- 6 mm Hg were recruited from a pulmonary clinic in a tertiary referral center. In addition, 14 normal control subjects, matched for age and gender, were studied. All patients underwent two consecutive full polysomnographies (PSG), one breathing room air and one breathing supplementary oxygen through nasal prongs, in random order. Controls were studied for one night breathing room air.

The mean oxygen saturation (SaO(2)) in ILD patients was 82.3 +/- 9.1% during sleep on air and 94.8 +/- 2.9% on oxygen (p < 0.001). In controls it was 92.9 +/- 1.9% (p < 0.001). Sleep efficiency was similar in patients and controls (75 vs. 82%, p > 0.05) and did not change with oxygen (77%). Arousal index was 12.4 +/- 6.9.h(-1) in ILD patients breathing room air and 12.9 +/- 9.1.h(-1) breathing oxygen while in controls it was 11.4 +/- 5.4.h(-1). Breathing frequency (f) during sleep was 24.7 +/- 4.2 in ILD patients and decreased breathing oxygen to 22.5 +/- 3.6 (p < 0.001) but was still higher than in controls (15.6 +/- 2.7; p < 0.001). Similarly, the heart rate (HR) in ILD and controls was 79 +/- 12 and 68 +/- 8, respectively (p < 0.001), and decreased to 68 +/- 4 when patients breathed oxygen (p < 0.001).

Oxygen substantially decreases HR and f, but does not normalize the f in ILD patients. The impact of hypoxia on sleep efficiency and arousal index was not demonstrable in our patients acclimatized to moderate altitude.