Document Detail

Effect of end-expiratory lung volume on upper airway collapsibility in sleeping men and women.
MedLine Citation:
PMID:  20576839     Owner:  NLM     Status:  MEDLINE    
The relationship between changes in absolute end-expiratory lung volume (EELV) and collapsibility has not been rigorously quantified. We hypothesized that pharyngeal collapsibility varies inversely with absolute lung volume in sleeping humans during 1) conventional and 2) isovolume measurements of passive critical pressure (Pcrit). Eighteen healthy subjects (11 male, 7 female) slept in a negative pressure ventilator for measurements of pharyngeal collapsibility (Pcrit) during non-rapid eye movement sleep. EELV was 1) allowed to vary with changes in nasal pressure for conventional Pcrit measurements and 2) controlled by maintaining a fixed pressure difference across the respiratory system (P(RS)) from the nose to the body surface for isovolume Pcrit measurements at elevated EELV (P(RS) = +10 cmH(2)O), reduced EELV (P(RS) = -5 cmH(2)O), and functional residual capacity (FRC; P(RS) = 0 cmH(2)O). In each condition, the absolute EELV was determined and the corresponding Pcrit was derived from upper airway pressure-flow relationships. In the entire group, Pcrit varied inversely with EELV (P < 0.001). Pcrit decreased as EELV increased from the conventional to the FRC isovolume condition by -3.5 ± 1.0 cmH(2)O/l (P < 0.003). Subjects with a conventional Pcrit below -2 cmH(2)O exhibited greater reductions in EELV and correspondingly greater decreases in the FRC isovolume compared with the conventional Pcrit (P < 0.001). The overall response, ΔPcrit/ΔEELV, was -2.0 ± 0.2 cmH(2)O/l (P < 0.001) and did not differ between men and women (P = 0.16). Nevertheless, men and women differed significantly in FRC (2.63 ± 0.16 vs. 1.88 ± 0.13 liters, P <0.05) and FRC isovolume Pcrit (-2.3 ± 0.8 vs. -7.2 ± 1.2 cmH(2)O, P < 0.05), implying that the men had larger lungs and more collapsible airways than the women. The ΔPcrit/ΔEELV response was independent of sex, conventional Pcrit, body mass index, and neck, waist, and hip circumferences. We conclude that Pcrit varies inversely with absolute EELV, which may lead to 1) an underestimation of the magnitude of quantitative differences in Pcrit across the spectrum from health (negative Pcrit) to disease (positive Pcrit) and 2) increases in sleep apnea susceptibility in obesity.
Samuel B Squier; Susheel P Patil; Hartmut Schneider; Jason P Kirkness; Philip L Smith; Alan R Schwartz
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2010-06-24
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  109     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2010 Oct 
Date Detail:
Created Date:  2010-10-13     Completed Date:  2011-05-23     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  977-85     Citation Subset:  IM    
Johns Hopkins Sleep Disorders Center, Johns Hopkins School of Medicine, Baltimore, Maryland , USA.
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MeSH Terms
Expiratory Reserve Volume
Forced Expiratory Volume
Lung / physiopathology*
Lung Compliance*
Lung Volume Measurements
Pharynx / physiopathology*
Pulmonary Ventilation*
Respiratory Mechanics*
Sex Factors
Sleep Apnea Syndromes / physiopathology*
Ventilators, Negative-Pressure
Vital Capacity
Young Adult
Grant Support
Comment In:
J Appl Physiol (1985). 2010 Oct;109(4):949-50   [PMID:  20671037 ]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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