Effects of a Bacteriological Filter on VO2max Measured by a Computerized Metabolic System

Purpose: To determine the effects of a purple bacteriological filter (PF) on the measured maximal oxygen uptake (VO_2max) during a maximal treadmill test as well as its effect on the expiratory flow measurements during a pulmonary function test. Methods: Male (n=7) and female (n=7) runners (18-35 years old) completed two continuous graded exercise tests (GXTs) followed by pulmonary function tests (PFT); one with a purple filter (PF) and one with no filter (NF). The GXT consisted of running at a constant speed on a treadmill while gradually increasing the grade until volitional exhaustion was reached. Following each of the GXTs two pulmonary function tests were performed under the same filter conditions used in the GXT. Testing was conducted over two consecutive days, and the order of the testing was randomized. Results: Mean values for maximal ventilation (V_Emax), VO_2max, and test duration were larger for the NF condition, however peak expiratory flow (PEF) was the only variable that proved to be statistically significant (pEmax was 4.33 ± 8.93 L/min higher and VO_2max was 1.1 ± 2.7 ml/kg/min higher, compared to the PF condition. There was a significant interaction between order of testing and V_Emax (p2max (pConclusion: The PF does not appear to have a large effect on VO_2mas, FVC, FEV₁, and FEV₁/FVC% values. However, PEF was significantly affected and V_Emax trended towards significance with a near-significant p-value of 0.051. When including order in the analysis, there does appear to be an order effect as participants increased VO_2max and V_Emax values from day 1 to day 2 regardless of condition order. Overall, VO_2max and V_Emax were not greatly affected by the presence of the purple bacteriological filter inserted between the expired gas hose and pneumotachometer.