Östberg Erland, Auner Udo, Enlund Mats, Zetterström Henrik, Edmark Lennart
a Department of Anaesthesia and Intensive Care , Västerås and Köping Hospital , Västerås , Sweden.
b Department of Radiology , Västerås Hospital , Västerås , Sweden.
Ups J Med Sci. 2017 Jun;122(2):92-98. doi: 10.1080/03009734.2017.1294635. Epub 2017 Apr 24.
Following preoxygenation and induction of anaesthesia, most patients develop atelectasis. We hypothesized that an immediate restoration to a low oxygen level in the alveoli would prevent atelectasis formation and improve oxygenation during the ensuing anaesthesia.
We randomly assigned 24 patients to either a control group (n = 12) or an intervention group (n = 12) receiving an oxygen washout procedure directly after intubation. Both groups were, depending on body mass index, ventilated with a positive end-expiratory pressure (PEEP) of 6-8 cmHO during surgery. The atelectasis area was studied by computed tomography before emergence. Oxygenation levels were evaluated by measuring blood gases and calculating estimated venous admixture (EVA).
The atelectasis areas expressed as percentages of the total lung area were 2.0 (1.5-2.7) (median [interquartile range]) and 1.8 (1.4-3.3) in the intervention and control groups, respectively. The difference was non-significant, and also oxygenation was similar between the two groups. Compared to oxygenation before the start of anaesthesia, oxygenation at the end of surgery was improved in the intervention group, mean (SD) EVA from 7.6% (6.6%) to 3.9% (2.9%) (P = .019) and preserved in the control group, mean (SD) EVA from 5.0% (5.3%) to 5.6% (7.1%) (P = .59).
Although the oxygen washout restored a low pulmonary oxygen level within minutes, it did not further reduce atelectasis size. Both study groups had small atelectasis and good oxygenation. These results suggest that a moderate PEEP alone is sufficient to minimize atelectasis and maintain oxygenation in healthy patients.
在预充氧和诱导麻醉后，大多数患者会发生肺不张。我们假设在肺泡中立即恢复低氧水平可预防肺不张的形成，并改善随后麻醉期间的氧合。
我们将24例患者随机分为对照组（n = 12）或干预组（n = 12），干预组在插管后直接接受氧冲洗程序。两组均根据体重指数在手术期间以6 - 8 cmH₂O的呼气末正压（PEEP）进行通气。在苏醒前通过计算机断层扫描研究肺不张面积。通过测量血气和计算估计静脉血掺杂（EVA）来评估氧合水平。
干预组和对照组中，肺不张面积占全肺面积的百分比分别为2.0（1.5 - 2.7）（中位数[四分位间距]）和1.8（1.4 - 3.3）。差异无统计学意义，两组的氧合情况也相似。与麻醉开始前的氧合相比，干预组手术结束时的氧合得到改善，平均（标准差）EVA从7.6%（6.6%）降至3.9%（2.9%）（P = 0.019），而对照组保持不变，平均（标准差）EVA从5.0%（5.3%）升至5.6%（7.1%）（P = 0.59）。
尽管氧冲洗在数分钟内恢复了较低的肺内氧水平，但并未进一步减小肺不张的大小。两个研究组的肺不张面积均较小且氧合良好。这些结果表明，仅适度的PEEP就足以使健康患者的肺不张最小化并维持氧合。
