Laghi F, Tobin M J
Division of Pulmonary and Critical Care Medicine, Edward Hines Jr. Veterans Administration Hospital, and Loyola University of Chicago Stritch School of Medicine, Hines, Illinois 60141, USA.
Eur Respir J. 1997 Mar;10(3):530-6.
The clinical application of transdiaphragmatic twitch pressure (Pdi,tw) response to phrenic nerve stimulation has been hindered by the requirement for placement of oesophageal and gastric balloons. Investigators have reported that mouth twitch pressure (Pmo,tw) estimates Pdi,tw accurately at lung volumes above and below functional residual capacity (FRC). However, it is not known whether Pmo,tw estimates Pdi,tw accurately when stimulation is performed at FRC during relaxed conditions. The aim of this study was to develop a simple method whereby measurements of Pmo could be used to predict oesophageal twitch pressure (Poes,tw) and possibly Pdi,tw at FRC. The study was performed in 11 healthy volunteers during phrenic nerve stimulation. At FRC, 9 of the 11 subjects showed a poor correlation between Pmo,tw and Poes,tw, and between Pmo,tw and Pdi,tw, probably due to varying degrees of glottic closure. Stimulations performed while subjects maintained an inspiratory flow of approximately 50 mL x s(-1), or at the point of reattaining FRC during an inspiration preceded by a limited exhalation, produced good correlations between Pmo,tw and Poes,tw (r=0.97 in both instances) and Pmo,tw and Pdi,tw (r=0.96 and r=0.95, respectively), with a steep slope. The respective slopes for the Pmo,tw Poes,tw relationship were 0.88 and 0.94, and for the Pmo,tw Pdi,tw relationship, 0.59 and 0.54. Unfortunately, these manoeuvres produced a significant increase in transpulmonary pressure (3.6+/-0.6 (SE) and 5.6+/-1.4 cmH2O, respectively), suggesting change in diaphragmatic length. Stimulations delivered while subjects performed an inspiratory effort or during exhalation against a high resistance preceded by a limited inhalation could not be used to predict Poes,tw and Pdi,tw from Pmo,tw. In conclusion, although transdiaphragmatic and oesophageal twitch pressure could be predicted from mouth twitch pressure during some inspiratory manoeuvres mouth twitch pressure was not reliable for the prediction of the oesophageal and transdiaphragmatic twitch pressure at functional residual capacity during relaxed conditions in healthy volunteers.
膈神经刺激引起的经膈抽搐压力（Pdi,tw）反应的临床应用因需要放置食管和胃内气囊而受到阻碍。研究人员报告称，在功能残气量（FRC）以上和以下的肺容积时，口腔抽搐压力（Pmo,tw）能准确估计Pdi,tw。然而，尚不清楚在放松状态下于FRC进行刺激时，Pmo,tw是否能准确估计Pdi,tw。本研究的目的是开发一种简单方法，通过该方法可利用Pmo的测量值来预测FRC时的食管抽搐压力（Poes,tw）以及可能的Pdi,tw。本研究在11名健康志愿者接受膈神经刺激期间进行。在FRC时，11名受试者中有9名的Pmo,tw与Poes,tw之间以及Pmo,tw与Pdi,tw之间相关性较差，这可能是由于声门关闭程度不同所致。当受试者保持约50 mL·s⁻¹的吸气流量时进行刺激，或在有限呼气后的吸气过程中重新达到FRC的时刻进行刺激，Pmo,tw与Poes,tw之间（两种情况下r均为0.97）以及Pmo,tw与Pdi,tw之间（分别为r = 0.96和r = 0.95）呈现出良好的相关性，且斜率较陡。Pmo,tw与Poes,tw关系的各自斜率分别为0.88和0.94，Pmo,tw与Pdi,tw关系的斜率分别为0.59和0.54。不幸的是，这些操作使跨肺压显著增加（分别为3.6±0.6（标准误）和5.6±1.4 cmH₂O），提示膈肌长度发生了变化。在受试者进行吸气努力时或在有限吸气后的高阻力呼气期间进行刺激，无法根据Pmo,tw来预测Poes,tw和Pdi,tw。总之，尽管在某些吸气操作过程中，经膈和食管抽搐压力可通过口腔抽搐压力来预测，但在健康志愿者放松状态下于功能残气量时，口腔抽搐压力对于预测食管和经膈抽搐压力并不可靠。
