Wheatley J R, West S, Cala S J, Engel L A
Thoracic Medicine Unit, Westmead Hospital, Sydney, Australia.
Eur Respir J. 1990 Jun;3(6):625-32.
To examine the relationship between end-expiratory lung volume and respiratory muscle work during acute bronchoconstriction, we measured the work of breathing in nine asthmatic subjects, in whom bronchoconstriction was induced with histamine aerosol. When the forced expiratory volume in one second (FEV1) fell below 60% of the control value, work was measured at the spontaneously hyperinflated lung volume (VLS), at a volume equivalent to the control functional residual capacity (FRC) and at a volume 30% of vital capacity (VC) above the control FRC. Hyperinflation to VLS caused a 39% decrease in the total positive work per breath from 2.8 +/- 0.4 to 1.7 +/- 0.1 J, entirely due to a decrease in expiratory work per breath from 1.6 +/- 0.4 to 0.10 +/- 0.05 J. Inspiratory work did not change at any lung volume, because the increase in inspiratory elastic work due to hyperinflation was offset by the decrease in flow resistive work. Breathing above VLS did not alter the total positive muscle work, but did increase the negative work of the inspiratory muscles from 0.4 +/- 0.1 to 0.8 +/- 0.1 J.breath. We conclude that during induced asthma spontaneous hyperinflation minimizes the total respiratory muscle work and may constitute a mechanism for minimizing energy expenditure.
为研究急性支气管收缩期间呼气末肺容积与呼吸肌功之间的关系，我们测量了9名哮喘患者的呼吸功，这些患者通过组胺气雾剂诱发支气管收缩。当一秒用力呼气容积（FEV1）降至对照值的60%以下时，在肺自发过度充气容积（VLS）、相当于对照功能残气量（FRC）的容积以及高于对照FRC 30%肺活量（VC）的容积下测量功。过度充气至VLS使每呼吸总正功从2.8±0.4焦耳降至1.7±0.1焦耳，下降了39%，这完全是由于每呼吸呼气功从1.6±0.4焦耳降至0.10±0.05焦耳。在任何肺容积下吸气功均未改变，因为过度充气导致的吸气弹性功增加被气流阻力功的减少所抵消。在VLS以上呼吸并未改变总正肌功，但确实使吸气肌的负功从0.4±0.1焦耳/呼吸增加至0.8±0.1焦耳/呼吸。我们得出结论，在诱发哮喘期间，自发过度充气可使总呼吸肌功最小化，可能构成一种使能量消耗最小化的机制。
