A Method for the Continuous Measurement and Display of Pulmonary Resistance in Man

1. We have validated a method for the continuous display and ‘on-line’ measurement of total pulmonary resistance in man, using a hybrid digital/analog computer.

2. The basic variables, which are measured by standard techniques, are flow rate of the mouth (V̇) and oesophageal pressure (P_oes), and these are the only analog inputs necessary to the computer.

3. Resistance (R_{L, cont}) is calculated continuously as: R_{L, cont} = (P_oes - V/C)/V̇ where V is tidal volume and C is the dynamic compliance. R_{L, cont} is continuously displayed as an analog signal on an oscilloscope.

4. Changes in resistance, measured by this method over a wide range of values in three subjects, showed an almost exact correlation with those measured by a standard method (Mead-Whittenberger).