[Continuous oximetry monitoring in patients undergoing home oxygen therapy for chronic respiratory failure]

We investigated the clinical usefulness of continuous nocturnal oxygen saturation monitoring in patients undergoing home oxygen therapy (HOT). The subjects were 11 patients with chronic respiratory disease in the process of healing from acute exacerbation. None were mechanically ventilated. Each subject underwent full overnight oximetry. One patient was excluded from further investigation because of periodic desaturation suggestive of sleep apnea. The remaining 10 subjects included 5 patients with sequelae of pulmonary tuberculosis, 2 with diffuse panbronchiolitis, 1 with chronic pulmonary emphysema, 1 with chronic bronchitis, and 1 with kyphoscoliosis. All underwent full overnight and 30 min daytime oximetry monitoring for 23.7 +/- 7.4 (mean +/- SD) consecutive days. Daytime oximetry was performed when subjects were awake and resting in supine position. Mean nocturnal oxygen saturation (NmSpO2) and mean daytime oxygen saturation (DmSpO2) were calculated from data obtained from 0:00 through 5:00 hrs and from data obtained during a stable 10 min daytime period, respectively. The difference between NmSpO2 and DmSpO2 (delta SpO2), the percentage of total sleep time with SpO2 < or = 90% (DST 90) and nocturnal lowest oxygen saturation (NLSpO2) were calculated once daily for each subject. There were significant (p < 0.05) correlations between NmSpO2 and NLSpO2, between NmSpO2 and DST 90, and between NLSpO2 and DST 90 in all subjects. However, significant (p < 0.05) correlations between NmSpO2 and DmSpO2 were observed in only 6. During acute exacerbation, NmSpO2 was lower than DmSpO2, and delta SpO2 increased. Conversely, with the amelioration of acute symptoms, delta SpO2 decreased and NmSpO2 was higher than DmSpO2. There was a significant (p < 0.05) reverse correlation between NmSpO2 and delta SpO2 in 9 subjects. We concluded that monitoring nocturnal oxygen saturation is clinically useful to assessments of oxygenation status in patients undergoing HOT, and that it may assist the early diagnosis of acute exacerbation of respiratory failure.