Gas exchange was significantly impaired, and the impairment was mainly due to lung volume but also a reduction of the gas exchange coefficient. (Image source: Thinkstock)

Gas exchange was significantly impaired, and the impairment was mainly due to lung volume but also a reduction of the gas exchange coefficient. (Image source: Thinkstock)

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Lung diffusion for carbon monoxide (DLCO) is commonly used to examine the diffusing capacity of the lung for carbon monoxide, a common assessment of pulmonary gas exchange. Similarly, pulmonary surfactant protein type B (SPB) can serve as a marker of damage to the alveolar-capillary membrane. Impaired oxygenation during anesthesia, even for patients with normal preoperative lung function, is a common finding.

Dr. Fabiano Di Marco, Pneumologia, Ospedale San Paolo, Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milan, Italy, and colleagues used DLCO to examine how anesthesia, muscle paralysis, and positive pressure ventilation affected DLCO and SPB in 45 consecutive patients undergoing scheduled extrathoracic surgery without laparoscopy. The authors discuss their results in the article “The Effects of Anesthesia, Muscle Paralysis, and Ventilation on the Lung Evaluated by Lung Diffusion for Carbon Monoxide and Pulmonary Surfactant Protein B,” which was published in this month’s issue of Anesthesia & Analgesia.

During anesthesia, the authors used volume-controlled ventilation, 6 to 8 mL/kg of predicted body weight. Total intravenous anesthesia was used so as not to interfere with DLCO measurements. They found that gas exchange was significantly impaired. The impairment was mainly due to a reduction in lung volume but also to a reduction of the gas exchange coefficient. Though these reductions were seen immediately after induction, there was no further decrease in value at 1 and 3 hours after anesthesia initiation.

The authors found no differences between smokers and nonsmokers. Alveolar damage, related to an increase in SPB, was  Finally, lung damage was directly correlated with dynamic lung strain and reduced perfusion of the aerated lung.

Given the popularity of lung injury manuscripts, this paper will likely be heavily cited in future publications.