Ribeiro Bruno M, Tucci Mauro R, Victor Júnior Marcus H, Melo Jose R, Gomes Susimeire, Nakamura Maria A M, Morais Caio C A, Beraldo Marcelo A, Lima Cristhiano A S, Alcala Glasiele C, Amato Marcelo B P
Laboratorio de Pneumologia LIM-09, Disciplina de Pneumologia, Instituto de Cardiologia (Incor), Hospital das Clinicas da Faculdade de Medicina da Universidade de Sao Paulo, Sao Paulo, Brazil.
Laboratorio de Pneumologia LIM-09, Disciplina de Pneumologia, Instituto de Cardiologia (Incor), Hospital das Clinicas da Faculdade de Medicina da Universidade de Sao Paulo, Sao Paulo, Brazil; Electronics Engineering, Aeronautics Institute of Technology, Sao Jose dos Campos, Brazil.
Anesthesiology. 2024 Apr 1;140(4):752-764. doi: 10.1097/ALN.0000000000004903.
Lower fractional inspired oxygen tension (Fio2) during general anesthesia can reduce lung atelectasis. The objectives are to evaluate the effect of two Fio2 (0.4 and 1) during low positive end-expiratory pressure (PEEP) ventilation over lung perfusion distribution, volume, and regional ventilation. These variables were evaluated at two PEEP levels and unilateral lung atelectasis.
In this exploratory study, 10 healthy female piglets (32.3 ± 3.4 kg) underwent mechanical ventilation in two atelectasis models: (1) bilateral gravitational atelectasis (n = 6), induced by changes in PEEP and Fio2 in three combinations: high PEEP with low Fio2 (Fio2 = 0.4), zero PEEP (PEEP0) with low Fio2 (Fio2 = 0.4), and PEEP0 with high Fio2 (Fio2 = 1); and (2) unilateral atelectasis (n = 6), induced by left bronchial occlusion, with the left lung aerated (Fio2 = 0.21) and low aerated (Fio2 = 1; n = 5 for this step). Measurements were conducted after 10 min in each step, encompassing assessment of respiratory mechanics, oxygenation, and hemodynamics; lung ventilation and perfusion by electrical impedance tomography; and lung aeration and perfusion by computed tomography.
During bilateral gravitational atelectasis, PEEP reduction increased atelectasis in dorsal regions, decreased respiratory compliance, and distributed lung ventilation to ventral regions with a parallel shift of perfusion to the same areas. With PEEP0, there were no differences between low and high Fio2 in respiratory compliance (23.9 ± 6.5 ml/cm H2O vs. 21.9 ± 5.0; P = 0.441), regional ventilation, and regional perfusion, despite higher lung collapse (18.6 ± 7.6% vs. 32.7 ± 14.5%; P = 0.045) with high Fio2. During unilateral lung atelectasis, the deaerated lung had a lower shunt (19.3 ± 3.6% vs. 25.3 ± 5.5%; P = 0.045) and lower computed tomography perfusion to the left lung (8.8 ± 1.8% vs. 23.8 ± 7.1%; P = 0.007).
PEEP0 with low Fio2, compared with high Fio2, did not produce significant changes in respiratory system compliance, regional lung ventilation, and perfusion despite significantly lower lung collapse. After left bronchial occlusion, the shrinkage of the parenchyma with Fio2 = 1 enhanced hypoxic pulmonary vasoconstriction, reducing intrapulmonary shunt and perfusion of the nonventilated areas.
全身麻醉期间较低的吸入氧分数（Fio2）可减少肺不张。目的是评估在低呼气末正压（PEEP）通气期间两种Fio2（0.4和1）对肺灌注分布、容积和区域通气的影响。在两个PEEP水平和单侧肺不张情况下对这些变量进行了评估。
在这项探索性研究中，10只健康雌性仔猪（32.3±3.4 kg）在两种肺不张模型中接受机械通气：（1）双侧重力性肺不张（n = 6），通过三种PEEP和Fio2组合诱导：高PEEP与低Fio2（Fio2 = 0.4）、零PEEP（PEEP0）与低Fio2（Fio2 = 0.4）、PEEP0与高Fio2（Fio2 = 1）；（2）单侧肺不张（n = 6），通过左支气管阻塞诱导，左肺通气（Fio2 = 0.21）和低通气（Fio2 = 1；此步骤n = 5）。在每个步骤10分钟后进行测量，包括呼吸力学、氧合和血流动力学评估；通过电阻抗断层扫描评估肺通气和灌注；通过计算机断层扫描评估肺通气和灌注。
在双侧重力性肺不张期间，PEEP降低会增加背部区域的肺不张，降低呼吸顺应性，并将肺通气分布到腹部区域，同时灌注也平行转移到相同区域。在PEEP0时，低Fio2和高Fio2在呼吸顺应性（23.9±6.5 ml/cm H2O对21.9±5.0；P = 0.441）、区域通气和区域灌注方面无差异，尽管高Fio2时肺萎陷更高（18.6±7.6%对32.7±14.5%；P = 0.045）。在单侧肺不张期间，萎陷肺的分流较低（19.3±3.6%对25.3±5.5%；P = 0.045），计算机断层扫描显示左肺灌注较低（8.8±1.8%对23.8±7.1%；P = 0.007）。
与高Fio2相比，低Fio2的PEEP0在呼吸系统顺应性、区域肺通气和灌注方面未产生显著变化，尽管肺萎陷明显更低。左支气管阻塞后，Fio2 = 1时实质组织的收缩增强了缺氧性肺血管收缩，减少了肺内分流和未通气区域的灌注。
