Ziehr David R, Alladina Jehan, Wolf Molly E, Brait Kelsey L, Malhotra Atul, La Vita Carolyn, Berra Lorenzo, Hibbert Kathryn A, Hardin C Corey
Division of Pulmonary and Critical Care Medicine, Department of Medicine, Massachusetts General Hospital, Boston, MA.
Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA.
Crit Care Explor. 2021 Jun 15;3(6):e0471. doi: 10.1097/CCE.0000000000000471. eCollection 2021 Jun.
Prone positioning improves clinical outcomes in moderate-to-severe acute respiratory distress syndrome and has been widely adopted for the treatment of patients with acute respiratory distress syndrome due to coronavirus disease 2019. Little is known about the effects of prone positioning among patients with less severe acute respiratory distress syndrome, obesity, or those treated with pulmonary vasodilators.
We characterize the change in oxygenation, respiratory system compliance, and dead-space-to-tidal-volume ratio in response to prone positioning in patients with coronavirus disease 2019 acute respiratory distress syndrome with a range of severities. A subset analysis of patients treated with inhaled nitric oxide and subsequent prone positioning explored the influence of pulmonary vasodilation on the physiology of prone positioning.
Retrospective cohort study of all consecutively admitted adult patients with acute respiratory distress syndrome due to coronavirus disease 2019 treated with mechanical ventilation and prone positioning in the ICUs of an academic hospital between March 11, 2020, and May 1, 2020.
Respiratory system mechanics and gas exchange during the first episode of prone positioning.
Among 122 patients, median (interquartile range) age was 60 years (51-71 yr), median body mass index was 31.5 kg/m (27-35 kg/m), and 50 patients (41%) were female. The ratio of Pao to Fio improved with prone positioning in 90% of patients. Prone positioning was associated with a significant increase in the ratio of Pao to Fio (from median 149 [123-170] to 226 [169-268], < 0.001) but no change in dead-space-to-tidal-volume ratio or respiratory system compliance. Supine ratio of Pao to Fio, respiratory system compliance, positive end-expiratory pressure, and body mass index did not correlate with absolute change in the ratio of Pao to Fio with prone positioning. However, patients with ratio of Pao to Fio less than 150 experienced a greater relative improvement in oxygenation with prone positioning than patients with ratio of Pao to Fio greater than or equal to 150 (median percent change in ratio of Pao to Fio 62 [29-107] vs 30 [10-70], = 0.002). Among 12 patients, inhaled nitric oxide prior to prone positioning was associated with a significant increase in the ratio of Pao to Fio (from median 136 [77-168] to 170 [138-213], = 0.003) and decrease in dead-space-to-tidal-volume ratio (0.54 [0.49-0.58] to 0.46 [0.44-0.53], = 0.001). Subsequent prone positioning in this subgroup further improved the ratio of Pao to Fio (from 145 [122-183] to 205 [150-232], = 0.017) but did not change dead-space-to-tidal-volume ratio.
Prone positioning improves oxygenation across the acute respiratory distress syndrome severity spectrum, irrespective of supine respiratory system compliance, positive end-expiratory pressure, or body mass index. There was a greater relative benefit among patients with more severe disease. Prone positioning confers an additive benefit in oxygenation among patients treated with inhaled nitric oxide.
俯卧位可改善中重度急性呼吸窘迫综合征的临床结局，并且已被广泛用于治疗2019冠状病毒病所致的急性呼吸窘迫综合征患者。对于病情较轻的急性呼吸窘迫综合征患者、肥胖患者或接受肺血管扩张剂治疗的患者，俯卧位的影响鲜为人知。
我们描述了不同严重程度的2019冠状病毒病急性呼吸窘迫综合征患者在俯卧位时氧合、呼吸系统顺应性和死腔与潮气量比值的变化。对接受吸入一氧化氮治疗并随后进行俯卧位的患者进行亚组分析，探讨肺血管扩张对俯卧位生理的影响。
设计、场所和参与者：对2020年3月11日至2020年5月1日期间在一所学术医院重症监护病房接受机械通气和俯卧位治疗的所有连续入院的成年2019冠状病毒病急性呼吸窘迫综合征患者进行回顾性队列研究。
首次俯卧位期间的呼吸系统力学和气体交换。
122例患者中，年龄中位数（四分位间距）为60岁（51 - 71岁），体重指数中位数为31.5 kg/m²（27 - 35 kg/m²），50例患者（41%）为女性。90%的患者俯卧位时氧分压与吸入氧分数值的比值升高。俯卧位与氧分压与吸入氧分数值的比值显著增加相关（从中位数149[123 - 170]升至226[169 - 268]，P < 0.001），但死腔与潮气量比值或呼吸系统顺应性无变化。仰卧位时氧分压与吸入氧分数值的比值、呼吸系统顺应性、呼气末正压和体重指数与俯卧位时氧分压与吸入氧分数值比值的绝对变化无关。然而，氧分压与吸入氧分数值比值小于15０的患者在俯卧位时氧合的相对改善大于氧分压与吸入氧分数值比值大于或等于15０的患者（氧分压与吸入氧分数值比值的中位数变化百分比62[29 - 107] vs 30[10 - 70]，P = 0.002）。在１２例患者中，俯卧位前吸入一氧化氮与氧分压与吸入氧分数值的比值显著增加相关（从中位数136[77 - 168]升至170[138 - 213]，P = 0.003），且死腔与潮气量比值降低（从0.54[0.49 - 0.58]降至0.46[0.44 - 0.53]，P = 0.001）。该亚组随后的俯卧位进一步改善了氧分压与吸入氧分数值的比值（从145[122 - 183]升至205[150 - 232]，P = 0.017），但未改变死腔与潮气量比值。
俯卧位可改善整个急性呼吸窘迫综合征严重程度范围内的氧合，与仰卧位呼吸系统顺应性、呼气末正压或体重指数无关。病情较重的患者相对获益更大。俯卧位对接受吸入一氧化氮治疗的患者在氧合方面具有附加益处。
