From the Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, and Harvard Medical School, Boston, Massachusetts.
Anesthesiology. 2018 Jun;128(6):1187-1192. doi: 10.1097/ALN.0000000000002159.
The effects of prone positioning on esophageal pressures have not been investigated in mechanically ventilated patients. Our objective was to characterize effects of prone positioning on esophageal pressures, transpulmonary pressure, and lung volume, thereby assessing the potential utility of esophageal pressure measurements in setting positive end-expiratory pressure (PEEP) in prone patients.
We studied 16 patients undergoing spine surgery during general anesthesia and neuromuscular blockade. We measured airway pressure, esophageal pressures, airflow, and volume, and calculated the expiratory reserve volume and the elastances of the lung and chest wall in supine and prone positions.
Esophageal pressures at end expiration with 0 cm H2O PEEP decreased from supine to prone by 5.64 cm H2O (95% CI, 3.37 to 7.90; P < 0.0001). Expiratory reserve volume measured at relaxation volume increased from supine to prone by 0.15 l (interquartile range, 0.25, 0.10; P = 0.003). Chest wall elastance increased from supine to prone by 7.32 (95% CI, 4.77 to 9.87) cm H2O/l at PEEP 0 (P < 0.0001) and 6.66 cm H2O/l (95% CI, 3.91 to 9.41) at PEEP 7 (P = 0.0002). Median driving pressure, the change in airway pressure from end expiration to end-inspiratory plateau, increased in the prone position at PEEP 0 (3.70 cm H2O; 95% CI, 1.74 to 5.66; P = 0.001) and PEEP 7 (3.90 cm H2O; 95% CI, 2.72 to 5.09; P < 0.0001).
End-expiratory esophageal pressure decreases, and end-expiratory transpulmonary pressure and expiratory reserve volume increase, when patients are moved from supine to prone position. Mean respiratory system driving pressure increases in the prone position due to increased chest wall elastance. The increase in end-expiratory transpulmonary pressure and expiratory reserve volume may be one mechanism for the observed clinical benefit with prone positioning.
机械通气患者的俯卧位对食管压力的影响尚未得到研究。我们的目的是描述俯卧位对食管压力、跨肺压和肺容积的影响，从而评估在俯卧位患者中使用食管压力测量来设置呼气末正压（PEEP）的潜在效用。
我们研究了 16 例在全身麻醉和神经肌肉阻滞下接受脊柱手术的患者。我们测量了气道压力、食管压力、气流和容量，并计算了仰卧位和俯卧位时的呼气储备量和肺及胸壁的弹性。
在 0 cm H2O PEEP 时，仰卧位到俯卧位时的食管压力在呼气末降低了 5.64 cm H2O（95%置信区间，3.37 至 7.90；P < 0.0001）。在松弛容积时测量的呼气储备量从仰卧位到俯卧位增加了 0.15 l（四分位间距，0.25，0.10；P = 0.003）。在 PEEP 为 0 时，胸壁弹性从仰卧位到俯卧位增加了 7.32（95%置信区间，4.77 至 9.87）cm H2O/l（P < 0.0001），在 PEEP 为 7 时增加了 6.66 cm H2O/l（95%置信区间，3.91 至 9.41）（P = 0.0002）。在 PEEP 为 0 和 7 时，气道压力从呼气末到吸气平台的变化即驱动压中位数在俯卧位时增加（3.70 cm H2O；95%置信区间，1.74 至 5.66；P = 0.001 和 3.90 cm H2O；95%置信区间，2.72 至 5.09；P < 0.0001）。
患者从仰卧位转为俯卧位时，呼气末食管压力降低，呼气末跨肺压和呼气储备量增加。由于胸壁弹性增加，俯卧位时平均呼吸驱动压增加。呼气末跨肺压和呼气储备量的增加可能是俯卧位观察到的临床益处的机制之一。
