Mosing Martina, Waldmann Andreas D, Gent Thom C, Hosgood Giselle, Sieber-Ruckstuhl Nadja S, Dennler Matthias, Herrmann Peter, Unger Karin
Clinical Department for Small Animals and Horses, Clinical Center for Small Animals, University of Veterinary Medicine, Vienna, Austria.
Section of Anaesthesiology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
Front Vet Sci. 2025 Mar 6;12:1545683. doi: 10.3389/fvets.2025.1545683. eCollection 2025.
Atelectasis is a common occurrence during anesthesia, and positive end-expiratory pressure (PEEP) ventilation and recruitment maneuvers (RM) can be used to mitigate this. However, both techniques may be associated with side effects in healthy lungs, and close monitoring is indicated. This study aimed to evaluate the effects of PEEP and RM in healthy dogs and to compare functional lung monitoring methods by electrical impedance tomography (EIT), volumetric capnography (VCap), and blood gas analysis with the gold-standard anatomical monitoring provided by computed tomography (CT).
Nine healthy Beagle dogs underwent anesthesia and mechanical ventilation three times. After 35 min using zero end-expiratory pressure (ZEEP), CT images, VCap, EIT measurements, and arterial blood gas samples were taken. Thereafter, either (1) ZEEP was continued, (2) PEEP initiated or (3) an RM was performed followed by PEEP. Ten minutes after changing the ventilation mode all measurements were repeated. Only one ventilation mode was employed during each anesthesia.
During RM, we found a significant increase in the percentage of overaerated lung (V) ( < 0.001), while the amount of normally aerated lung (V), poorly aerated lung and non-aerated lung decreased ( ≤ 0.001). VCap showed an increase in airway dead space (VD/VT) ( = 0.002), and a decrease in alveolar dead space (VD/VT). For PEEP, an increase in airway dead space ( = 0.003) was found. For both groups, the amount of carbon dioxide exhaled per breath (VTCO) decreased ( = 0.001), and EIT showed a shift of the center of ventilation to the dependent lung areas ( = 0.021 and = 0.046, respectively). Oxygenation was superior in RM compared to ZEEP ( = 0.033). The arterial partial pressure of carbon dioxide decreased in RM ( = 0.012). Positive associations were found between V and VD/VT ( = 0.004), V and VD/VT ( = 0.004), V and V with VTCO ( = 0.002 for both). Negative associations were found between V and VD/VT ( = 0.004) and non-dependent silent spaces ( = 0.050), and V with oxygenation ( = 0.030).
While RM may be effective in improving gas exchange, it appears to be not benign in healthy lungs, and PEEP might be the preferable strategy to avoid lung collapse during anesthesia. Functional monitoring - EIT, VCap, blood gas analysis - does not detect changes corresponding to anatomical findings on CT.
肺不张是麻醉期间的常见情况，呼气末正压（PEEP）通气和肺复张手法（RM）可用于缓解这种情况。然而，这两种技术在健康肺中都可能伴有副作用，因此需要密切监测。本研究旨在评估PEEP和RM对健康犬的影响，并通过电阻抗断层扫描（EIT）、容积式二氧化碳描记法（VCap）以及血气分析等功能肺监测方法与计算机断层扫描（CT）提供的金标准解剖学监测进行比较。
9只健康的比格犬接受3次麻醉和机械通气。在使用零呼气末正压（ZEEP）35分钟后，采集CT图像、VCap、EIT测量值和动脉血气样本。此后，要么（1）继续使用ZEEP，（2）开始使用PEEP，要么（3）先进行RM然后使用PEEP。改变通气模式10分钟后，重复所有测量。每次麻醉期间仅采用一种通气模式。
在RM期间，我们发现过度充气肺（V）的百分比显著增加（<0.001），而正常充气肺（V）、充气不良肺和未充气肺的量减少（≤0.001）。VCap显示气道死腔（VD/VT）增加（=0.002），肺泡死腔（VD/VT）减少。对于PEEP，发现气道死腔增加（=0.003）。对于两组，每呼吸呼出的二氧化碳量（VTCO）均减少（=0.001），EIT显示通气中心向肺依赖区偏移（分别为=0.021和=0.046）。与ZEEP相比，RM时氧合情况更好（=0.033）。RM时动脉血二氧化碳分压降低（=0.012）。发现V与VD/VT（=0.004）、V与VD/VT（=0.004）、V和V与VTCO之间呈正相关（两者均为=0.002）。发现V与VD/VT（=0.004）和非依赖静区（=0.050）以及V与氧合之间呈负相关（=0.030）。
虽然RM可能有效改善气体交换，但在健康肺中似乎并非无害，PEEP可能是麻醉期间避免肺萎陷的更可取策略。功能监测——EIT、VCap、血气分析——未检测到与CT上解剖学发现相对应的变化。
