Usually, an average of two or more attempts is considered for DLCO calculation in the single breath-holding technique.Īnother method to calculate DLCO is the intrabreath method, which is calculated during exhalation. The recommended timing method used is the Jones and Meade method, which measures breath holding time at thirty percent of inspiratory time up to half of the sampling time. Total lung volume, initial and final CO concentration, and breath-holding time are used to calculate DLCO. The collected gas is analyzed for CO and tracer concentrations. Subsequently, the patient exhales out completely, and exhaled gas is collected for analysis after excluding the initial amount of gas from dead space. The patient is then asked to hold his breath for 10 seconds at total lung capacity (TLC). It separates air within the alveoli from blood flowing in the pulmonary capillaries. The respiratory membrane forms the diffusing barrier. In brief, during a ten-second breath-hold, DLCO measures uptake of CO per unit time per mm of driving pressure of CO (cc of CO/sec/mm of Hg). Among other potential gases for evaluating diffusing capacity, oxygen is not preferred since its uptake is limited by cardiac uptake and total body consumption. Inhaled CO is used for this test due to its high affinity for hemoglobin (200 to 250 times that of oxygen).
Carbon monoxide (CO) has a high affinity for hemoglobin, and it follows the same pathway as that of oxygen to finally bind with hemoglobin. DLCO is a measurement to assess the lungs' ability to transfer gas from inspired air to the bloodstream. Spirometry is the most common and widely used lung function test, followed by diffusing capacity of the lungs for carbon monoxide (DLCO). Pulmonary function tests are performed to assess lung function.
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