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Thoracic gas compression during forced expiration is greater in men than women.

ABSTRACT: Intrapleural pressure during a forced vital capacity (VC) maneuver is often in excess of that required to generate maximal expiratory airflow. This excess pressure compresses alveolar gas (i.e., thoracic gas compression [TGC]), resulting in underestimated forced expiratory flows (FEFs) at a given lung volume. It is unknown if TGC is influenced by sex; however, because men have larger lungs and stronger respiratory muscles, we hypothesized that men would have greater TGC. We examined TGC across the "effort-dependent" region of VC in healthy young men (n = 11) and women (n = 12). Subjects performed VC maneuvers at varying efforts while airflow, volume, and esophageal pressure (POES ) were measured. Quasistatic expiratory deflation curves were used to obtain lung recoil (PLUNG ) and alveolar pressures (i.e., PALV = POES -PLUNG ). The raw maximal expiratory flow-volume (MEFVraw ) curve was obtained from the "maximum effort" VC maneuver. The TGC-corrected curve was obtained by constructing a "maximal perimeter" curve from all VC efforts (MEFVcorr ). TGC was examined via differences between curves in FEFs (?FEF), area under the expiratory curves (?AEX ), and estimated compressed gas volume (?VGC) across the VC range. Men displayed greater total ?AEX (5.4 ± 2.0 vs. 2.0 ± 1.5 L2 ·s-1 ; p < .001). ?FEF was greater in men at 25% of exhaled volume only (p < .05), whereas ?VGC was systematically greater in men across the entire VC (main effect; p < .05). PALV was also greater in men throughout forced expiration (p < .01). Taken together, these findings demonstrate that men display more TGC, occurring early in forced expiration, likely due to greater expiratory pressures throughout the forced VC maneuver.

SUBMITTER: Gideon EA

PROVIDER: S-EPMC7090372 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Thoracic gas compression during forced expiration is greater in men than women.

Gideon Elizabeth A EA Cross Troy J TJ Cayo Brooke E BE Betts Aaron W AW Merrell Dallin S DS Coriell Catherine L CL Hays Lauren E LE Duke Joseph W JW

Physiological reports 20200301 6

Intrapleural pressure during a forced vital capacity (VC) maneuver is often in excess of that required to generate maximal expiratory airflow. This excess pressure compresses alveolar gas (i.e., thoracic gas compression [TGC]), resulting in underestimated forced expiratory flows (FEFs) at a given lung volume. It is unknown if TGC is influenced by sex; however, because men have larger lungs and stronger respiratory muscles, we hypothesized that men would have greater TGC. We examined TGC across t ...[more]

PMID: 32207254

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Project description:Spirometric parameters are the mainstay for diagnosis of COPD, but cannot distinguish airway obstruction from emphysema. We aimed to develop a computer model that quantifies airway collapse on forced expiratory flow-volume loops. We then explored and validated the relationship of airway collapse with computed tomography (CT) diagnosed emphysema in two large independent cohorts.A computer model was developed in 513 Caucasian individuals with ?15 pack-years who performed spirometry, diffusion capacity and CT scans to quantify emphysema presence. The model computed the two best fitting regression lines on the expiratory phase of the flow-volume loop and calculated the angle between them. The collapse was expressed as an Angle of collapse (AC) which was then correlated with the presence of emphysema. Findings were validated in an independent group of 340 individuals.AC in emphysema subjects (N?=?251) was significantly lower (131°?±?14°) compared to AC in subjects without emphysema (N?=?223), (152°?±?10°) (p?<?0.0001). Multivariate regression analysis revealed AC as best indicator of visually scored emphysema (R2?=?0.505, p?<?0.0001) with little significant contribution of KCO, %predicted and FEV1, %predicted to the total model (total R2?=?0.626, p?<?0.0001). Similar associations were obtained when using CT-automated density scores for emphysema assessment. Receiver operating characteristic (ROC) curves pointed to 131° as the best cut-off for emphysema (95.5% positive predictive value, 97% specificity and 51% sensitivity). Validation in a second group confirmed the significant difference in mean AC between emphysema and non-emphysema subjects. When applying the 131° cut-off, a positive predictive value of 95.6%, a specificity of 96% and a sensitivity of 59% were demonstrated.Airway collapse on forced expiration quantified by a computer model correlates with emphysema. An AC below 131° can be considered as a specific cut-off for predicting the presence of emphysema in heavy smokers.

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Thoracic gas compression during forced expiration is greater in men than women.

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Thoracic gas compression during forced expiration is greater in men than women.

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