On the Prediction of Pulmonary Diffusing Capacity with a Steady State Carbon Monoxide Method in Chronic Lung Diseases

Abstract

In 25 patients with chronic obstructive pulmonary diseases, DL_CO was estimated under steady state conditions during mild to moderate exercise. The values calculated according to Filley et al. were significantly lower than values corrected for CO capillary back pressure as suggested by Linderholm, but values predicted according to Holmgren's equation given for normal individuals were significantly higher. A new equation is proposed for the prediction of DL_CO, which is derived from the high correlation between Filley's and Linderholm's values. Its precision was demonstrated in 35 patients with different lung diseases. The equation is written DL_CO corrected for CO back pressure'=—0.528 + 1.095 x DL_CO uncorrected, SD ± 0.367.

Key Words:

• Calculations
• comparison
• CO steady state
• diffusing capacity
• prediction equation
• pulmonary diseases