Elliott A R, Prisk G K, Guy H J, Kosonen J M, West J B
Department of Medicine, University of California, San Diego, La Jolla 92093-0931, USA.
J Appl Physiol (1985). 1996 Jul;81(1):33-43. doi: 10.1152/jappl.1996.81.1.33.
Gravity is known to influence the mechanical behavior of the lung and chest wall. However, the effect of sustained microgravity (microG) on forced expirations has not previously been reported. Tests were carried out by four subjects in both the standing and supine postures during each of seven preflight and four postflight data-collection sessions and four times during the 9 days of microG exposure on Spacelab Life Sciences-1. Compared with preflight standing values, peak expiratory flow rate (PEFR) was significantly reduced by 12.5% on flight day 2 (FD2), 11.6% on FD4, and 5.0% on FD5 but returned to standing values by FD9. The supine posture caused a 9% reduction in PEFR. Forced vital capacity and forced expired volume in 1 s were slightly reduced (approximately 3-4%) on FD2 but returned to preflight standing values on FD4 and FD5, and by FD9 both values were slightly but significantly greater than standing values. Forced vital capacity and forced expiratory volume in 1 s were both reduced in the supine posture (approximately 8-10%). Forced expiratory flows at 50% and between 25 and 75% of vital capacity did not change during microG but were reduced in the supine posture. Analysis of the maximum expiratory flow-volume curve showed that microG caused no consistent change in the curve configuration when individual in-flight days were compared with preflight standing curves, although two subjects did show a slight reduction in flows at low lung volumes from FD2 to FD9. The interpretation of the lack of change in curve configuration must be made cautiously because the lung volumes varied from day to day in flight. Therefore, the flows at absolute lung volumes in microG and preflight standing are not being compared. The supine curves showed a subtle but consistent reduction in flows at low lung volumes. The mechanism responsible for the reduction in PEFR is not clear. It could be due to a lack of physical stabilization when performing the maneuver in the absence of gravity or a transient reduction in respiratory muscle strength.
众所周知，重力会影响肺和胸壁的力学行为。然而，持续微重力对用力呼气的影响此前尚未见报道。在“太空实验室生命科学 - 1”号上，四名受试者在七次飞行前和四次飞行后的数据收集阶段，分别以站立和仰卧姿势进行了测试，在微重力暴露的9天中还进行了四次测试。与飞行前站立值相比，呼气峰值流速（PEFR）在飞行日2（FD2）显著降低了12.5%，在FD4降低了11.6%，在FD5降低了5.0%，但在FD9时恢复到站立值。仰卧姿势导致PEFR降低了9%。用力肺活量和1秒用力呼气量在FD2时略有降低（约3 - 4%），但在FD4和FD5时恢复到飞行前站立值，到FD9时这两个值均略高于站立值且具有显著差异。用力肺活量和1秒用力呼气量在仰卧姿势时均降低（约8 - 10%）。肺活量50%时以及肺活量25%至75%之间的用力呼气流量在微重力期间没有变化，但在仰卧姿势时降低。对最大呼气流量 - 容积曲线的分析表明，与飞行前站立曲线相比，当比较各个飞行日内的曲线时，微重力并未导致曲线形态出现一致变化，不过有两名受试者在从FD2到FD9期间，低肺容积时的流量略有降低。由于飞行中肺容积每日不同，所以对曲线形态缺乏变化的解读必须谨慎。因此，微重力状态下与飞行前站立时的绝对肺容积流量并未进行比较。仰卧曲线在低肺容积时显示出流量有细微但一致的降低。PEFR降低的机制尚不清楚。这可能是由于在没有重力的情况下进行该动作时缺乏身体稳定性，或者是呼吸肌力量的短暂下降。
