Vitacca M, Lanini B, Nava S, Barbano L, Portal R, Clini E, Ambrosino N
Divisione di Pneumologia Riabilitativa, Fondazione S. Maugeri IRCCS, Istituto Scientifico di Gussago, BS, Italy.
Monaldi Arch Chest Dis. 2004 Apr-Jun;61(2):81-5. doi: 10.4081/monaldi.2004.704.
In severe stable hypercapnic COPD patients the amount of pressure time product (PTP) spent to counterbalance their dynamic intrinsic positive end expiratory pressure (PEEPi,dyn) is high: no data are available on the best setting of non invasive pressure support ventilation (NPSV) to reduce the inspiratory muscle workload due to PEEPi,dyn.
The objectives of this randomised controlled physiological study were: 1. To measure the inspiratory muscle workload due to PEEPi,dyn 2. To measure the effects on this parameter of two settings of NPSV in stable COPD patients with chronic hypercapnia admitted in a Pulmonary Division of two Rehabilitation Centers. Twenty-three stable COPD patients with chronic hypercapnia on domiciliary nocturnal NPSV for 30 +/- 20 months were submitted to an evaluation of breathing pattern, PEEPi,dyn, inspiratory muscle workload and its partitioning during both assisted and unassisted ventilation. Two settings of NPSV were randomly applied for 30 minutes each: i- "at patient's comfort" (C): Inspiratory pressure support (IPS) was the maximal tolerated pressure able to reduce awake PaCO2 with the addition of a pre-set level of external PEEP (PEEPe); ii- "physiological setting" (PH): the level of IPS able to achieve a > 40% and < 90% decrease in transdiaphragmatic pressure in comparison to spontaneous breathing (SB). A PEEPe level able to reduce PEEPi,dyn by at least 50% was added.
During SB the tidal diaphragmatic pressure-time product (PTPdi/b) was 17.62 +/- 7.22 cmH2O*sec, the component due to PEEPi,dyn (PTPdiPEEPi,dyn) being 38 +/- 17% (range: 16-65%). Compared to SB,PTPdiPEEPi,dyn was reduced significantly with both settings, the reduction being greater with PH compared to C.
In conclusion in severe COPD patients with chronic hypercapnia the inspiratory muscle workload due to PEEPidyn is high and is reduced by NPSV at a greater extent when ventilator setting is tailored to patient's mechanics.
在重度稳定型高碳酸血症慢性阻塞性肺疾病（COPD）患者中，用于抵消其动态内在呼气末正压（PEEPi,dyn）所花费的压力时间乘积（PTP）量很高：目前尚无关于无创压力支持通气（NPSV）最佳设置以减少因PEEPi,dyn导致的吸气肌工作量的数据。
这项随机对照生理学研究的目的是：1. 测量因PEEPi,dyn导致的吸气肌工作量；2. 测量在两个康复中心的肺病科收治的慢性高碳酸血症稳定COPD患者中，两种NPSV设置对该参数的影响。23例在家中接受夜间NPSV治疗30±20个月的慢性高碳酸血症稳定COPD患者，在辅助通气和自主通气期间接受呼吸模式、PEEPi,dyn、吸气肌工作量及其分配的评估。两种NPSV设置各随机应用30分钟：i - “患者舒适度设置”（C）：吸气压力支持（IPS）是能够在添加预设水平的外部呼气末正压（PEEPe）的情况下降低清醒时动脉血二氧化碳分压（PaCO2）的最大耐受压力；ii - “生理设置”（PH）：与自主呼吸（SB）相比，能够使跨膈压降低>40%且<90%的IPS水平。添加能够使PEEPi,dyn至少降低50%的PEEPe水平。
在SB期间，潮式膈肌压力时间乘积（PTPdi/b）为17.62±7.22 cmH2O*秒，因PEEPi,dyn导致的部分（PTPdiPEEPi,dyn）为38±17%（范围：16 - 65%）。与SB相比，两种设置均使PTPdiPEEPi,dyn显著降低，与C相比，PH降低幅度更大。
总之，在重度慢性高碳酸血症COPD患者中，因PEEPidyn导致的吸气肌工作量很高，当通气设置根据患者力学特性进行调整时，NPSV能更大程度地降低该工作量。
