Pulmonary Diffusing Capacity Changes to Posture and Acute Exercise in Healthy Volunteers: a Randomised Test-retest Relaibility Study

The combined measurement of the pulmonary diffusing capacity to carbon monoxide (CO) and nitric oxide (NO) (DLCO/NO) has recently been standardised and validated for clinical use. It involves a very short breath-hold time (≤5 seconds), and it may be repeated up to 12 times without affecting measurements, and it is thus ideal for assessing acute changes in pulmonary diffusing capacity and its components during various physiological manoeuvres. The aim of the present study is to compare the test-retest reliability of pulmonary diffusing capacity measurements during postural changes (sitting vs. supine) vs. rest-to-exercise. DLCO/NO will either be measured in the sitting position during rest vs. exercise or in the sitting and supine posture, and this will be repeated within 1-7 days in 20 healthy individuals that will be randomised to one of the two interventions. Statistically,the test-retest relaibility of sitting-to-supine vs. rest-to-exercise changes in DLCO/NO will be compared by parametric methods.