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Repeatability of the single‐breath method for estimation of pulmonary blood‐flow: comparison among four data‐reduction procedures

1986; Wiley; Volume: 6; Issue: 3 Linguagem: Inglês

10.1111/j.1475-097x.1986.tb00621.x

1365-2281

P. Christensen, J. Grønlund,

Chronic Obstructive Pulmonary Disease (COPD) Research

Summary. The single‐breath method of Kim, Rahn and Farhi (1966) enables the estimation of the pulmonary blood‐flow from the P co 2 vs. P co 2 curve recorded during a prolonged expiration. Studies on the repeatability of the method have given very different results. At one extreme the estimated pulmonary blood flows ranged from —47 to 173 litre/min and at the other extreme the repeatability was found to be better than that usually reported for invasive methods. A possible explanation for these important differences is the use of different data‐reduction procedures to calculate the pulmonary blood‐flow from the measured P co 2 and P o 2 values. In the present study we have investigated the repeatability of the single‐breath method in 20 test subjects using four previously published data‐reduction procedures. Furthermore, we have studied the sensitivity of the estimated pulmonary blood‐flow to measurement noise for each of the four data‐reduction procedures, by using a previously described technique based on computer simulations. Three of the data‐reduction procedures gave standard deviations on repeated single determinations of the pulmonary blood‐flow of about 1 litre/min whereas the last method gave results which fluctuated wildly from one determination to the next. The simulation showed that about 1/3 of the random variations can be ascribed to the measurement noise in P co 2 and P o 2 .