Am. J. Respir. Crit. Care Med., Vol 152, No. 1, 07 1995, 193-198.
Influence of sleep on pulmonary capillary volume in normal and asthmatic subjects
JA Desjardin, JM Sutarik, BY Suh and RD Ballard
Department of Medicine, Denver Veterans Affairs Medical Center, Colorado 80220, USA.
To determine the effect of sleep upon intrapulmonary blood volume (as
reflected by measurements of pulmonary capillary volume (VC), 5 normal
subjects and 15 asthmatic patients were monitored overnight in our sleep
laboratory. VC was determined before and after sleep from four measurements
of DLCO using a single-breath technique, with subjects inspiring different
oxygen concentrations for each measurement. Spirometry was performed in the
supine posture before presleep VC measurements and immediately upon
awakening before postsleep VC measurements. As defined by a > or = 15%
overnight reduction in FEV1, 10 asthmatic subjects demonstrated nocturnal
worsening. FEV1 decreased from 61.2 +/- 15.1 to 40.9 +/- 16.2% of predicted
(p = 0.0001) in the 10 asthmatic patients with nocturnal worsening.
Asthmatic patients with nocturnal worsening also demonstrated a 15.7 +/-
16.6% increase in VC from presleep to awakening (p = 0.02). Normal subjects
and asthmatic patients without nocturnal worsening exhibited no significant
overnight change in FEV1 or VC. We conclude that in asthmatic patients with
nocturnal worsening sleep is likely associated with an increase in
intrapulmonary blood volume.
