An evaluation of the vitalograph pulmonary monitor

The Vitalograph pulmonary monitor has recently been altered by the manufactures to read in litres per minute. In 200 pairs of measurements comparing the monitor to the Wright peak flow meter (PFM) the mean difference between the instrument was 0.57 litres/min and there was a strong positive correlation (r = 0.92). The mean within subject coefficient of variation was 5.8% (range 2.6% to 10.7%). There was a statistical difference (P less than 0.05) in measurements obtained with different monitors but in practical terms this difference was small. The monitor is pocket-sized and light and is therefore suitable for following changes in peak expiratory flow away from the physiology laboratory.