title: Influence of sleep on lung volume in asthmatic patients and normal subjects.
abstract: To assess the effect of sleep on functional residual capacity (FRC) in normal subjects and asthmatic patients, 10 adult subjects (5 asthmatic patients with nocturnal worsening, 5 normal controls) were monitored overnight in a horizontal volume-displacement body plethysmograph. With the use of a single inspiratory occlusion technique, we determined that when supine and awake, asthmatic patients were hyperinflated relative to normal controls (FRC = 3.46 +/- 0.18 and 2.95 +/- 0.13 liters, respectively; P less than 0.05). During sleep FRC decreased in both groups, but the decrease was significantly greater in asthmatic patients such that during rapid-eye-movement (REM) sleep FRC was equivalent between the asthmatic and normal groups (FRC = 2.46 +/- 0.23 and 2.45 +/- 0.09 liters, respectively). Specific pulmonary conductance decreased progressively and significantly in the asthmatic patients during the night, falling from 0.047 +/- 0.007 to 0.018 +/- 0.002 cmH2O-1.s-1 (P less than 0.01). There was a significant linear relationship through the night between FRC and pulmonary conductance in only two of the five asthmatic patients (r = 0.55 and 0.65, respectively). We conclude that 1) FRC falls during sleep in both normal subjects and asthmatic patients, 2) the hyperinflation observed in awake asthmatic patients is diminished during non-REM sleep and eliminated during REM sleep, and 3) sleep-associated reductions in FRC may contribute to but do not account for all the nocturnal increase in airflow resistance observed in asthmatic patients with nocturnal worsening.
authors.affiliation: Department of Medicine, Denver Veterans Administration Medical Center, Colorado.
authors.forename: R D
authors.initials: RD
authors.lastname: Ballard
authors.forename: C G
authors.initials: CG
authors.lastname: Irvin
authors.forename: R J
authors.initials: RJ
authors.lastname: Martin
authors.forename: J
authors.initials: J
authors.lastname: Pak
authors.forename: R
authors.initials: R
authors.lastname: Pandey
authors.forename: D P
authors.initials: DP
authors.lastname: White
mesh_terms: D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D005541:Forced Expiratory Volume / Q000502:physiology; D005652:Functional Residual Capacity / Q000502:physiology*; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D010993:Plethysmography, Whole Body / Q000295:instrumentation; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology