Qualidade de Sono e Parâmetros de Dessaturação Nocturna em Doentes com Doença Pulmonar Obstrutiva Crónica e Hipoxémia entre 55-70 mmHg

Abstract

Nocturnal desaturation is well recnognized in patients with chronic respiratory failure (CRF). Alveolar hypoventilation, particulary in REM sleep, is frequently assumed as the main physiopathological mechanism. This ocurrence is important in patients with mild basal hypoxemia (PaO2 55-70 mmHg) because of the particular position of the PaO2 in the oxyhemoglobin desaturation curve. However, disturbances of the quality of sleep that alter the normal structure of sleep in patients with chronic obstructive pulmonary disease (COPD) has been described in the literature. The objective of this study is to evaluate how the quality of sleep could afect the parameters of nocturnal desaturation and the definition of a patient as a desaturator. Twenty patients (15 men; 5 women; 68.2 ± 6.1 yrs) with stabilized CRF secondary to COPD (FEV1 = 1.024 ± 0.431 L; 47 ± 16.5% predicted) were submited to a polysomnographic study in two consecutive nights in ambient air, free of sedative medication and under usual broncodilator medication. In the first night of sleep the general pattern was insomnia and fragmented sleep (increase in sleep latency time, number of arousals and a decrease in the efficiency of sleep) with a consequent reduction in the time spent in 3-4 and REM sleep. In the second night of study a significant reduction of sleep latency time (72 ± 65.5 vs. 28 ± 31.4 mn; p = 0.008) and an increase in efficiency of sleep (52 ± 26.5 vs. 76 ± 13.4%; p < 0.0001) was seen, without any significant variation in the number of aroulsals and of the time in slow wave sleep but with a significant increase in REM sleep (6 ± 4.8 vs. 11 ± 6.5 %; p < 0.01). No significant differences were noted in the nocturnal desaturation parameters over the two nights although there was a large individual variability. Correlation between individual variation in sleep parameters and variation in desaturation parameters was significant for the variation in minimal saturation with variation in total sleep time (r = 0.559) and for the variation in time spent with SaO2 < 80 % with the time spent in REM sleep (r = 0.471). Using two definitions of desaturator patient – 1) more than 5 minutes with a SaO2 < 90% with at least one episode with minimal SaO2 < 85%; 2) more than 30% of the recorded time with SaO2 < 90% - it was concluded that for the first criteria 11/20 patients were desaturators on the second night vs 7/20 on first night (p = 0.002) and for the second criteria 9/20 vs. 7/20 for the second and first night respectively (p = 0.012). It was concluded that patients with COPD and mild hypoxemia show a bad quality of sleep with a “first night effect”. No significant variation in nocturnal desaturation parameters was seen in a second night of sleep but the intensity of the desaturation and the classification of a patient as desaturator can be affected. REV PORT PNEUMOL 2001; VII (2):