Yan S, Kayser B, Tobiasz M, Sliwinski P
Montreal Chest Institute Research Centre, Montreal, Quebec, Canada.
Am J Respir Crit Care Med. 1996 Oct;154(4 Pt 1):938-44. doi: 10.1164/ajrccm.154.4.8887589.
Intrinsic positive end-expiratory pressure (PEEPi) due to dynamic hyperinflation has been measured as a plateau airway opening pressure during airway occlusion (PEEPi,stat). PEEPi has also been dynamically determined as a fall in esophageal pressure (Pes) before the inspiratory flow starts (PEEPi,dyn). The aims of the current study were to systematically compare PEEPi,stat and PEEPi,dyn and to explain the underlying mechanisms of their difference. The study was performed in healthy subjects with dynamic hyperinflation induced by expiration through a Starling resistor. The Campbell diagram was constructed for each subject by determining the static pressure-volume curves of the lung (Pst,[l]) and chest wall (Pst,[w]). For a given end-expiratory volume, PEEPi,stat was measured on the Campbell diagram as the pressure difference between Pst(w) and -Pst(l). PEEPi,dyn was measured as mentioned above. The effects of respiratory muscle recruitment on PEEPi,dyn were estimated by the Pes values when Pes started to fall relative to Pst(w). We found that: (1) there was a great variability of the PEEPi,dyn/PEEPi,stat ratio among and within subjects; (2) expiratory muscle recruitment was evident on most occasions; (3) persistent inspiratory muscle activity during expiration was present in some subjects; (4) the Pes values at the start of inspiratory flow were frequently on the left of -Pst(l), which contributed to the difference between PEEPi,stat and PEEPi,dyn and implied a greater dynamic than static elastance presumably due to viscoelastic properties; (5) chest wall distortions characterized by inflation of the abdomen with deflation of the rib cage during the initial inspiratory efforts were observed in three subjects. In conclusion, interpretation of PEEPi,dyn needs to be cautious because both expiratory and tonic inspiratory muscle activities that lead to significant over- or underestimation of PEEPi by PEEPi,dyn, respectively, are associated with acute dynamic hyperinflation. In addition, the effects of viscoelastic properties and chest wall distortions on PEEPi,dyn need to be further investigated.
由于动态肺过度充气导致的内在呼气末正压（PEEPi）已被测量为气道阻塞期间的平台气道开口压力（静态PEEPi，PEEPi,stat）。PEEPi也已被动态确定为吸气气流开始前食管压力（Pes）的下降（动态PEEPi，PEEPi,dyn）。本研究的目的是系统比较PEEPi,stat和PEEPi,dyn，并解释它们差异的潜在机制。该研究在通过Starling阻力器呼气诱导动态肺过度充气的健康受试者中进行。通过确定肺（Pst,[l]）和胸壁（Pst,[w]）的静态压力-容积曲线，为每个受试者构建坎贝尔图。对于给定的呼气末容积，在坎贝尔图上测量PEEPi,stat，作为Pst(w)与-Pst(l)之间的压力差。PEEPi,dyn如上述进行测量。当Pes相对于Pst(w)开始下降时，通过Pes值估计呼吸肌募集对PEEPi,dyn的影响。我们发现：（1）受试者之间和受试者内部PEEPi,dyn/PEEPi,stat比值存在很大变异性；（2）大多数情况下呼气肌募集明显；（3）一些受试者在呼气期间存在持续的吸气肌活动；（4）吸气气流开始时的Pes值经常在-Pst(l)的左侧，这导致了PEEPi,stat和PEEPi,dyn之间的差异，并暗示可能由于粘弹性特性导致动态弹性大于静态弹性；（5）在三名受试者中观察到在初始吸气努力期间以腹部膨胀和胸廓收缩为特征的胸壁变形。总之，对PEEPi,dyn的解释需要谨慎，因为导致PEEPi,dyn分别显著高估或低估PEEPi的呼气和强直性吸气肌活动均与急性动态肺过度充气有关。此外，粘弹性特性和胸壁变形对PEEPi,dyn的影响需要进一步研究。
