无创正压通气不同压力支持水平对正常人呼吸做功的影响

The Effect of Non-invasive Pressure Support Levels on Work of Breathing of in Normal Volunteers

目的 :观察无创正压通气 (NIPPV)不同压力水平对正常人呼吸做功的影响 ,为临床合理地应用NIPPV提供理论依据。方法 :选择 9例正常人行NIPPV并寻找出“最舒适”的吸气压力水平 (IPAP) ,在此压力基础上增加或减少 2 5 %的压力 ,构成低IPAP、最舒适IPAP和高IPAP三个压力水平 ,每一IPAP水平通气 15min以上 ,比较不同压力水平呼吸做功改变。结果 :受试者认为“最舒适”的IPAP为 (11.33± 3.2 0 )cmH2 O ,EPAP为 (4 .5 6± 0 .88)cmH2 O[相当于PSV水平为 (6 .77± 3.2 0 )cmH2 O]。与自主呼吸相比 ,NIPPV增加VE的同时 ,总的呼吸做功(Wtot)明显增加 (P <0 .0 5 ) ,而受试者吸气肌做功占总的吸气做功的百分比 (Wi,p/Wi)明显减少 (P <0 .0 5 )。在最舒适IPAP时 ,Wi,p/Wi降低到基础值的 14 %± 9%。这种变化趋势与IPAP的水平相关。结论 :NIPPV可以显著降低吸气肌肉做功。吸气肌做功减少的比例与IPAP的水平相关。研究的结果为NIPPV时PSV的参数设定提供了生理学的依据。

Objective: In order to provide scientific evidence to guide the proper setting of pressure support levels in non invasive ventilation (NIPPV),the change of work of breathing (WOB) after different levels of pressure support was investigated in normal volunteers. Methods: 9 normal volunteers were recruited in the study. The most comfortable level of inspiratory pressure (CIPAP) was chosen according to the subjects feeling after a trial of different levels of IPAP. On the basis of CIPAP,a 25% increase or decrease of IPAP (HIAPA and LIPAP) were set. The three levels of IPAP were used for the NIPPV with 15 minute duration for each level. Work of breathing (WOB) was measured with esophageal pressure and lung volume monitoring on the basis of Campbells diagram. Rerults: It was shown that CIPAP was 11.33±3.20 cmH 2O and most comfortable expiratory pressure (EPAP) was 4.56±0.88 cmH 2O,in equivalence to the most comfortable pressure support level at 6.77±3.20 cmH 2O. As compared with spontaneous breathing(SB),NIPPV increased minute ventilation (VE) and total WOB (Wtot)( P< 0.05),while it reduced the subjects inspiratory muscles WOB expressed as percentage of total inspiratory WOB (Wi,p/Wi). At CIPAP level,(Wi,p/Wi) was reduced to 14%±9% of the SB level. The tendency of change in WOB was related to level of IPAP( P< 0.05). Conclusion:NIPPV was able to decrease the subjects inspiratory WOB and unload their inspiratory muscles in normal volunteers. This change was related to the level of inspiratory pressure.