Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, USA.
Department of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA.
Physiol Rep. 2020 Mar;8(6):e14404. 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 (P ) were measured. Quasistatic expiratory deflation curves were used to obtain lung recoil (P ) and alveolar pressures (i.e., P = P -P ). The raw maximal expiratory flow-volume (MEFV ) 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 (MEFV ). TGC was examined via differences between curves in FEFs (∆FEF), area under the expiratory curves (∆A ), and estimated compressed gas volume (∆VGC) across the VC range. Men displayed greater total ∆A (5.4 ± 2.0 vs. 2.0 ± 1.5 L ·s ; 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). P 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.
在用力肺活量（VC）操作期间，胸内压通常超过产生最大呼气流量所需的压力。这种过压会压缩肺泡气体（即胸内气体压缩[TGC]），导致在给定的肺容积下低估强制呼气流量（FEF）。目前尚不清楚 TGC 是否受性别影响；然而，由于男性的肺更大，呼吸肌更强壮，我们假设男性会有更大的 TGC。我们在健康的年轻男性（n = 11）和女性（n = 12）中检查了 VC 的“依赖于努力”区域的 TGC。受试者在不同的努力下进行 VC 操作，同时测量气流、体积和食管压力（P ）。使用准静态呼气衰减曲线获得肺回缩（P ）和肺泡压力（即 P = P -P ）。从“最大努力”VC 操作中获得原始最大呼气流量-容积（MEFV ）曲线。通过从所有 VC 努力中构建“最大周长”曲线来获得 TGC 校正曲线（MEFV ）。通过比较 FEF 之间的曲线差异（∆FEF）、呼气曲线下的面积（∆A ）和 VC 范围内估计的压缩气体体积（∆VGC）来检查 TGC。男性显示出更大的总∆A（5.4 ± 2.0 对 2.0 ± 1.5 L ·s ；p < 0.001）。只有在呼出量的 25%时，男性的∆FEF 才更大（p < 0.05），而在整个 VC 中，男性的∆VGC 系统地更大（主要影响；p < 0.05）。男性在整个用力呼气过程中 P 也更高（p < 0.01）。综上所述，这些发现表明男性表现出更多的 TGC，在用力呼气早期发生，可能是由于整个用力 VC 操作过程中的呼气压力更大。
