Klas J V, Dempsey J A
John Rankin Laboratory of Pulmonary Medicine, Department of Preventive Medicine, University of Wisconsin, Madison.
Am Rev Respir Dis. 1989 Jan;139(1):150-6. doi: 10.1164/ajrccm/139.1.150.
We determined the efficiency with which maximal exercise ventilatory output could be mimicked voluntarily. Five normal subjects exercised to maximal volitional effort and flow:volume and pressure:volume loops, and end-expiratory lung volume (EELV) and breathing pattern were measured. All subjects increased expiratory flow rate and reduced EELV sufficiently so that the forced vital capacity loop was approximated during at least some portion of expiration, but the generation of pleural pressure remained effective, i.e., equal to or only slightly in excess of that required to produce maximal expiratory flow (Pmax). Subsequently, while at rest, subjects used visual feedback and were able to closely mimic the flow:volume, EELV, and breath-timing achieved in maximal exercise; however: (1) expiratory pressures were excessive and usually exceeded average Pmax; (2) abdominal expiratory muscle activity was increased, as indicated by positive shifts in expiratory gastric pressure; and (3) total ventilatory work was increased 15 to 40% greater than that achieved in maximal exercise. Maximal voluntary efforts (MVV) caused EELV to increase and ventilatory work was increased 20 to 300% greater than during maximal exercise. We conclude that accurate determination of maximal effective ventilatory output available for maximal exercise or precise quantitation of the metabolic cost of producing maximal exercise ventilation requires replication of the pressure:volume, breath-timing, and EELV characteristics achieved in maximal exercise.
我们测定了最大运动通气输出可被自主模拟的效率。五名正常受试者进行运动至最大自主努力和流量，测量流量：容积和压力：容积环、呼气末肺容积（EELV）及呼吸模式。所有受试者充分提高呼气流量率并降低EELV，使得在呼气的至少某些部分期间近似于用力肺活量环，但胸膜压力的产生仍然有效，即等于或仅略高于产生最大呼气流量（Pmax）所需的压力。随后，在静息时，受试者使用视觉反馈，能够紧密模拟最大运动时达到的流量：容积、EELV和呼吸时间；然而：（1）呼气压力过高，通常超过平均Pmax；（2）腹部呼气肌活动增加，表现为呼气时胃内压正向变化；（3）总通气功比最大运动时增加15%至40%。最大自主努力（MVV）导致EELV增加，通气功比最大运动时增加20%至300%。我们得出结论，准确测定最大运动时可用的最大有效通气输出或精确量化产生最大运动通气的代谢成本需要复制最大运动时达到的压力：容积、呼吸时间和EELV特征。
