Diffusion capacity of lungs for carbon monoxide may help evaluate severity of lung disorders preoperatively

In conjunction with spirometry and lung volumes, the diffusion capacity of the lungs for carbon monoxide (DLCO) is advised for evaluating parenchymal and non-parenchymal lung disorders. In the majority of cardiac surgery facilities, the preoperative DLCO is not regularly monitored. DLCO is used to evaluate the severity of restrictive and obstructive lung disorders, pulmonary vascular disease, and preoperative risk. Patients who survive coronavirus disease-2019 (COVID-19) commonly develop lung complications.

Recent published case series examined preoperative pulmonary function evaluations that included chest X-ray, high-resolution computed tomography of the chest, arterial blood gas analysis at room air, and spirometry with DLCO measurement. DLCO was measured using a single-breath approach with the SPIRO AIR® volumetric PFT (pulmonary function test) System (Medisoft, Sorinnes, Belgium).

Lung is the organ most often affected by COVID-19. Endothelial damage and alveolar-capillary micro-thrombosis have been identified as factors driving pulmonary vascular disease in these individuals. Interstitial lung disease and pulmonary fibrosis are characterized by a drop in DLCO and Kco (transfer coefficient) due to the thickening of the alveolar-capillary membrane. An isolated decrease in DLCO is indicative of pulmonary capillary bed loss due to early parenchymal lung disease. Unlike spirometric measurements, DLCO is less influenced by the patient's exertion.

This case series demonstrates that COVID-19 survivors undergoing cardiac surgery may have DLCO impairment. Long-term studies are required to determine if the evaluation of diffusing capacity (DLCO) in addition to spirometry should be incorporated in regular clinical follow-up of COVID-19 survivors.

Reference –

Singh, Ajmer,; Nanda, Chinmaya; Mehta, Yatin Diffusion capacity for carbon monoxide in patients recovered from COVID-19: A useful parameter to assess pulmonary function, Journal of Anaesthesiology Clinical Pharmacology: Volume 38 - Issue Suppl 1 - p S151-S153

doi: 10.4103/joacp.joacp_250_21