An Assessment of the Steady-state Carbon Monoxide Method of Estimating Pulmonary Diffusing Capacity

For the past three years we have been using Bates's steady-state carbon monoxide technique for estimating the efficiency of gas transfer through the lungs as a routine laboratory procedure (Bates, Boucot, and Dormer, 1955). This paper reports certain formal investigations carried out to assess the usefulness and accuracy of the method and to help us to choose which of three ways in which the results can be expressed would be the most informative. These were the apparent diffusing capacity (D1), percentage uptake of carbon monoxide, and what we have called the " conductance " of the lungs (C), a term we took from Dornhorst (1952). Numerous investigators have used the first two indices (see Bates and others, 1955; Forster, 1957), but the last has not to our knowledge been used before. We chose a somewhat simplified version of Bates's method in preference to the single-breath technique described