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.

Quantifying tidal expiratory flow limitation using a vector-based analysis technique

“…expiratory flow limitation), leading to thoracic gas compression. As a result, forced expiratory flows measured at the mouth may be underestimated, particularly at effort independent lung volumes (Guenette et al 2010, Gideon et al 2020. Furthermore, Gideon et al (2020) demonstrated that males show more thoracic gas compression than females due to greater expiratory pressure generation throughout the FVC manoeuvre secondary to greater respiratory muscle mass and power (Gideon et al 2020).…”

“…As a result, forced expiratory flows measured at the mouth may be underestimated, particularly at effort independent lung volumes (Guenette et al 2010, Gideon et al 2020. Furthermore, Gideon et al (2020) demonstrated that males show more thoracic gas compression than females due to greater expiratory pressure generation throughout the FVC manoeuvre secondary to greater respiratory muscle mass and power (Gideon et al 2020). The relatively lower transpulmonary pressure during tidal breathing results in less thoracic gas compression facilitating greater expiratory flows (Yuan et al 2014).…”