CHEST：俯卧位可更好地改善肥胖的ARDS患者的氧合和预后

肥胖患者出现肺不张和急性呼吸窘迫综合征（ARDS）的风险较高。已知俯卧位（PP）可以减少普通人出现肺不张的机会，并可改善伴有严重低氧血症的ARDS患者的氧合和预后；但该体位对于肥胖的ARDS患者的效果，人们了解的仍很少。为了加深对这一问题的认识，来自法国蒙彼利埃大学医院、圣埃洛伊医院重症监护和移植科的Audrey De Jong及其同事进行了一项研究，研究结果在线发表于2013年2月28日的《CHEST》杂志上。研究结果显示：俯卧位对于肥胖患者是安全的。与非肥胖患者相比，该体位似乎可以更好地改善肥胖患者的氧合效果。

该研究是一项病例对照性临床研究，其研究对象主要为应用了俯卧位姿势、且属于病态肥胖的ARDS患者，对照组则为与之相匹配的非肥胖的ARDS患者。研究者将病态肥胖定义为：体重指数（BMI）≥35公斤/平方米；非肥胖定义为BMI＜30公斤/平方米。而ARDS患者的诊断标准则为：PaO2/FiO2比值≤200毫米汞柱。研究的主要终点是应用俯卧位姿势的安全性和并发症；次要终点则包括：应用俯卧位姿势对患者氧合作用的影响（观察俯卧位姿势结束时的PaO2/FiO2比值），患者应用机械通气的时间、患者在ICU内住留的时间，以及患者的医院内感染率和死亡率。

该研究的主要结果为：在2005年1月至2009年12月期间，共有149例患者被确诊为ARDS。研究者对其中33例肥胖患者与相匹配的33例非肥胖患者进行了对照研究。肥胖组患者与非肥胖患者使用俯卧位的中位数时间分别为9（6-11）小时、和8（7-12）小时。研究者共收集到了51个并发症，其中25个发生于肥胖组患者，另26个则发生于非肥胖组患者。2组患者中出现至少一个并发症者的例数相同，均为10例（30%）。肥胖组患者的PaO2/FiO2比值从俯卧前的118±43增至俯卧后的222±84毫米汞柱；而非肥胖组患者的该比值则从俯卧前的113±43增至俯卧后的174±80毫米汞柱。2组比较，肥胖组患者的增幅明显更大（P=0.03）。此外，肥胖组患者在住院90天时的死亡率显著低于非肥胖组（27% 对48%）；但2组患者的机械通气时间、ICU的住留时间、以及医院内感染率等均无明显差异。

该研究结果显示：俯卧位对于肥胖患者似乎是安全的。与非肥胖患者相比，该体位似乎可以更好地改善肥胖患者的氧合效果。肥胖患者可能是一组更能从俯卧体位中受益的ARDS亚组患者。

Feasibility and Effectiveness of Prone Position in Morbidly Obese Patients With ARDS: A Case-Control Clinical Study.
BACKGROUND
Obese patients are at risk for developing atelectasis and ARDS. Prone position (PP) may reduce atelectasis, and it improves oxygenation and outcome in severe hypoxemic patients with ARDS, but little is known about its effect in obese patients with ARDS.
METHODS
Morbidly obese patients (BMI ≥ 35 kg/m2) with ARDS (Pao2/Fio2 ratio ≤ 200 mm Hg) were matched to nonobese (BMI < 30 kg/m2) patients with ARDS in a case-control clinical study. The primary end points were safety and complications of PP; the secondary end points were the effect on oxygenation (Pao2/Fio2 ratio at the end of PP), length of mechanical ventilation and ICU stay, nosocomial infections, and mortality.
RESULTS
Between January 2005 and December 2009, 149 patients were admitted for ARDS. Thirty-three obese patients were matched with 33 nonobese patients. Median (25th-75th percentile) PP duration was 9 h (6-11 h) in obese patients and 8 h (7-12 h) in nonobese patients (P = .28). We collected 51 complications: 25 in obese and 26 in nonobese patients. The number of patients with at least one complication was similar across groups (n = 10, 30%). Pao2/Fio2 ratio increased significantly more in obese patients (from 118 ± 43 mm Hg to 222 ± 84 mm Hg) than in nonobese patients (from 113 ± 43 mm Hg to 174 ± 80 mm Hg; P = .03). Length of mechanical ventilation, ICU stay, and nosocomial infections did not differ significantly, but mortality at 90 days was significantly lower in obese patients (27% vs 48%, P < .05).
CONCLUSIONS
PP seems safe in obese patients and may improve oxygenation more than in nonobese patients. Obese patients could be a subgroup of patients with ARDS who may benefit the most of PP.