Keenan Joseph C, Cortes-Puentes Gustavo A, Adams Alexander B, Dries David J, Marini John J
University of Minnesota, Minneapolis, Minnesota and Regions Hospital, Saint Paul, Minnesota.
Hennepin County Medical Center, Minneapolis, Minnesota.
Respir Care. 2016 Nov;61(11):1536-1542. doi: 10.4187/respcare.04813. Epub 2016 Oct 18.
Esophageal pressure measurement for computation of transpulmonary pressure (P) has begun to be incorporated into clinical use for evaluating forces across the lungs. Gaps exist in our understanding of how esophageal pressure (and therefore P), a value measured at a single site, responds when respiratory system compartments are asymmetrically affected by whole-lung atelectasis or unilateral injury as well as changes in chest wall compliance. We reasoned that P would track with aerated volume changes as estimated by functional residual capacity (FRC) and tidal volume. We examined this hypothesis in the setting of asymmetric lungs and changes in intra-abdominal pressure.
This study was conducted in the animal laboratory of a university-affiliated hospital. Models of unilateral atelectasis and unilateral and bilateral lung injury exposed to intra-abdominal hypertension (IAH) in 10 deeply sedated mechanically ventilated swine. Atelectasis was created by balloon occlusion of the left main bronchus. Unilateral lung injury was induced by saline lavage of isolated right lung. Diffuse lung injury was induced by saline lavage of both lungs. The peritoneum was insufflated with air to create a model of pressure-regulated IAH. We measured esophageal pressures, airway pressures, FRC by gas dilution, and oxygenation.
FRC was reduced by IAH in normal lungs (P < .001) and both asymmetric lung pathologies (P < .001). P at end-expiration was decreased by IAH in bilateral (P = .001) and unilateral lung injury (P = .003) as well as unilateral atelectasis (P = .019). In the setting of both lung injury models, end-expiratory P showed a moderate correlation in tracking with FRC.
P tracks with aerated lung volume in the setting of thoracic asymmetry and changes in intra-abdominal pressure. However, used alone, it cannot distinguish the relative contributions of air-space distention and recruitment of lung units.
用于计算跨肺压（P）的食管压力测量已开始应用于临床，以评估作用于肺部的力。当呼吸系统各腔室受到全肺肺不张、单侧损伤以及胸壁顺应性变化的不对称影响时，我们对食管压力（进而P，一个在单一部位测量的值）如何反应的理解存在差距。我们推测P会随着功能残气量（FRC）和潮气量估计的充气量变化而变化。我们在不对称肺和腹腔内压力变化的情况下检验了这一假设。
本研究在一所大学附属医院的动物实验室进行。对10只深度镇静、机械通气的猪建立单侧肺不张、单侧和双侧肺损伤并暴露于腹腔高压（IAH）的模型。通过球囊阻塞左主支气管造成肺不张。通过对孤立的右肺进行盐水灌洗诱导单侧肺损伤。通过对双侧肺进行盐水灌洗诱导弥漫性肺损伤。向腹膜内注入空气以建立压力调节的IAH模型。我们测量了食管压力、气道压力、通过气体稀释法测量的FRC以及氧合情况。
IAH使正常肺（P < .001）以及两种不对称肺病变（P < .001）中的FRC降低。IAH使双侧肺损伤（P = .001）、单侧肺损伤（P = .003）以及单侧肺不张（P = .019）时的呼气末P降低。在两种肺损伤模型中，呼气末P与FRC的变化呈中度相关。
在胸廓不对称和腹腔内压力变化的情况下，P与充气肺容积相关。然而，单独使用时，它无法区分气腔扩张和肺单位复张的相对贡献。
