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

• Published in: Physiological reports Vol. 8; no. 6; pp. e14404 - n/a
• Main Authors: Gideon, Elizabeth A., Cross, Troy J., Cayo, Brooke E., Betts, Aaron W., Merrell, Dallin S., Coriell, Catherine L., Hays, Lauren E., Duke, Joseph W.
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.03.2020; John Wiley and Sons Inc; Wiley
• Subjects: Adolescent; Adult; alveolar pressure; Alveoli; area under the curve; Catheters; Compression; Esophagus; Exhalation; Female; flow volume loop; Gases; Gender differences; Humans; Laboratories; Lung; Lung - physiology; lung recoil pressure; Lung Volume Measurements; Male; Maximal Expiratory Flow-Volume Curves; Muscles; Original Research; Physiology; Pressure; Pressure transducers; Respiratory Conditions Disorder and Diseases; respiratory mechanics; Sex Characteristics; Thorax; Thorax - physiology; Vital Capacity; Women; Young Adult; United States > US; lung recoil pressure; area under the curve; alveolar pressure; respiratory mechanics; flow volume loop
• ISSN: 2051-817X; 2051-817X
• DOI: 10.14814/phy2.14404

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. We sought to examine whether sex influences the degree to which thoracic gas compression (TGC) underestimates forced expiratory flows at a given lung volume during forced expiration. Men displayed greater TGC than women, particularly at 25% of the forced expired volume. This greater TGC was likely due to greater expiratory pressures generated by men throughout the maneuver. Failure to appropriately account for TGC results in a greater underestimation of expiratory airflow in men, primarily during the early phase of forced expiration.