Gas exchange is measured through several means, including Diffusing capacity for carbon monoxidePulse oximetryArterial blood gas samplingDiffusing Capacity for Carbon MonoxideThe diffusing capacity of the lungs for carbon monoxide (DLCO) is a measure of the ability of gas to transfer from the alveoli across the alveolar epithelium and the capillary endothelium to the red blood cells. The DLCO depends not only on the area and thickness of the blood-gas barrier but also on the volume of blood in the pulmonary capillaries. The distribution of alveolar volume and ventilation also affects the measurement.DLCO is measured by sampling end-expiratory gas for carbon monoxide (CO) after patients inspire a small amount of carbon monoxide, hold their breath, and exhale. Measured DLCO should be adjusted for alveolar volume (which is estimated from dilution of helium) and the patient’s hematocrit. DLCO is reported as mL/minute/mm Hg and as a percentage of a predicted value expressed as a z-score (1)...
