Physiologic correlates of sleep quality in severe emphysema

Sleep quality is poor in severe emphysema. We hypothesized that in addition to nocturnal oxygen desaturation, the severity of airflow obstruction and degree of thoracic hyperinflation are responsible.

Twenty-five patients (14 males, 64 ± 6 [ ± SD] yrs, BMI 24.7 ± 4.2 kg/m(2)) with severe emphysema (FEV(1) = 28 ± 8% predicted, TLC = 125 ± 14% predicted) were studied. Measurements included spirometry, lung volumes, arterial blood gas, length of the diaphragm's zone of apposition (LZAP) and a polysomnogram.

Total sleep time (TST) was 227 ± 93 minutes with a sleep efficiency (SE) of 56 ± 21%. The mean SaO(2), lowest SaO(2), and% TST with a SaO(2) < 90% were 90 ± 5%, 83 ± 8% and 29 ± 40%, respectively. TST correlated with FEV(1)% (r = 0.5, p = 0.02), FVC% (r = 0.4, p = 0.03) and LZAP (r = 0.5, p = 0.01). SE correlated with FEV(1)% (r = 0.5, p = 0.02) and LZAP (r = 0.5, p = 0.01), but not with FVC% (r = 0.4, p = 0.07). Additionally, TST and SE correlated negatively with residual volume% (r = -0.4, p = 0.046, and r = -0.4, p = 0.03, respectively). There was no correlation between TST and SE and measures of nocturnal oxygenation. Multiple linear regression was used to predict TST, with 50% (r(2) = 0.49) explained by a combination of LZAP (27%), mean SaO(2) (23%), and the lowest SaO(2) (< 1%). To predict SE, 44% (r(2) = 0.43) was explained by a combination of LZAP (29%), mean SaO(2) (14%), and the lowest SaO(2) (1%).

Although parameters of respiratory function and mechanics correlate with sleep quality, both nocturnal oxygenation and measurements of respiratory function/mechanics predict sleep quality in severe emphysema.