ARTERIAL OXYGEN-SATURATION IN CHRONIC CONGESTIVE-HEART-FAILURE

Continuous, 24-hour, ambulatory pulse oximetry was used in 10 subjects with New York Heart Association functional class II to III heart fail ure and in 5 age-matched controls to test the prevailing view that art erial oxygen saturation is preserved during wakefulness in chronic mil d to moderate heart failure. Subjects with heart failure were stabiliz ed on digitalis and diuretics at the time of the study. All subjects m aintained time-activity logs, with an emphasis on self-reported sleep and wakefulness. A desaturation event was defined as a decrease in art erial oxygen saturation greater-than-or-equal-to 4% from baseline last ing >5 seconds. Variables assessed included total desaturation events, decrease in arterial oxygen saturation duration/event, nadir of arter ial oxygen saturation/event, and desaturation index ([cumulative desat uration time/total monitoring time] x 100). The ratio of self-reported wakefulness:sleep desaturation time was 47:53% for subjects with hear t failure versus 64:36% for controls (p = NS). Mean (+/- SEM) time of arterial oxygen saturation < 90% was 123 +/- 67 minutes for subjects w ith heart failure versus 22 +/- 25 minutes for controls (p < 0.01). To tal desaturations were 220 +/- 63 and 76 +/- 35 (p = NS) for the heart failure and control groups, respectively. The heart failure group had a statistically, significantly greater decrease in arterial oxygen sa turation, and a longer duration and deeper nadir of the desaturation e vent than did the age-matched control group. The desaturation index wa s 21 +/- 3% and 4 +/- 1% for the heart failure and control groups, res pectively (p < 0.01). Both the heart failure and control groups showed a circadian pattern in arterial oxygen saturation profiles. It is con cluded that arterial oxygen saturation is not preserved during self-re ported wakefulness in chronic mild to moderate heart failure, showing significant desaturation events as compared with control subjects.