TY - JOUR
T1 - Effect of end-expiratory lung volume on upper airway collapsibility in sleeping men and women
AU - Squier, Samuel B.
AU - Patil, Susheel P.
AU - Schneider, Hartmut
AU - Kirkness, Jason P.
AU - Smith, Philip L.
AU - Schwartz, Alan R.
PY - 2010/10
Y1 - 2010/10
N2 - 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 measurementsof passive critical pressure (Pcrit). Eighteen healthy subjects (11 male, 7female) 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 acrossthe respiratory system (PRS) from the nose to the body surface for isovolume Pcrit measurements at elevated EELV (PRS = +10 cmH2O), reducedEELV (PRS = -5 cmH2O), and functional residual capacity (FRC; PRS = 0 cmH2O). 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 2O/l (P < 0.003).Subjects with a conventional Pcrit below -2 cmH2O 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 cmH2O/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 cmH2, 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.
AB - 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 measurementsof passive critical pressure (Pcrit). Eighteen healthy subjects (11 male, 7female) 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 acrossthe respiratory system (PRS) from the nose to the body surface for isovolume Pcrit measurements at elevated EELV (PRS = +10 cmH2O), reducedEELV (PRS = -5 cmH2O), and functional residual capacity (FRC; PRS = 0 cmH2O). 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 2O/l (P < 0.003).Subjects with a conventional Pcrit below -2 cmH2O 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 cmH2O/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 cmH2, 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.
KW - Critical pressure
KW - Pharyngeal collapsibility
KW - Sleep apnea
UR - http://www.scopus.com/inward/record.url?scp=78149316220&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=78149316220&partnerID=8YFLogxK
U2 - 10.1152/japplphysiol.00080.2010
DO - 10.1152/japplphysiol.00080.2010
M3 - Article
C2 - 20576839
AN - SCOPUS:78149316220
SN - 8750-7587
VL - 109
SP - 977
EP - 985
JO - Journal of applied physiology
JF - Journal of applied physiology
IS - 4
ER -