The incidence of VO2 plateau at VO2max in a cardiac diseased population using different sampling techniques

Abstract

Introduction: Historically, the gold standard criteria used to confirm „true‟ VO2max has been a plateau inVO2 despite an increase in exercise workload. More recently, it has been shown that shorter sampling intervals increase the ability to detect a VO2 plateau. To the best of our knowledge, these techniques have only been utilized on healthy populations. Purpose: To investigate the incidence of VO2 plateau at VO2max in a cardiovascular-diseased (CVD) population using four different sampling techniques (15 breath moving average, 15 second time averaging, 30 second time averaging, and 60 second time averaging) and three different VO2 plateau criteria (≤50mL·min-1, ≤80mL·min-1, ≤150mL·min-1). Methods: In a cross sectional study design, 69 people (62 ± 10 years) with recently diagnosed CVD performed a modified Balke maximal exercise test (10:07 ± 2:24 min). Participants were classified as maximal (n=57) if the test was self-terminated due to fatigue or classified as symptomlimited (n=12) if symptoms presented during testing. Gas exchange data (VO2, VCO2, RER and VE) were obtained breath-by-breath and averaged using the four different sampling intervals. The mean of the final two VO2 data points were considered VO2max in the maximal test population and VO2peak in the symptom-limited group. Attainment of VO2max was confirmed using three different VO2 plateau criteria. Results: Chi Square analysis revealed a significant (p<0.05) relationship between sampling technique and incidence of VO2 plateau at VO2max in all VO2 plateau criteria (χ2(3)=68.48 (≤50mL·min-1); χ2(3)=54.43 (≤80 mL·min-1); χ2(3)=10.49 (≤150mL·min-1). Sampling interval technique had an association with the incidence of VO2 plateau with the strongest effect in the ≤50mL·min-1 criteria (Cramer‟s V=0.548, p<0.05). Mean VO2max was significantly different between all sampling intervals (F = 79.26, p<0.05) except between the 15 breath moving average and 15 second time average. Conclusion: The incidence of VO2 plateau at VO2max is altered by the manipulation of the sampling interval in people with CVD. To increase the likelihood of measuring „true‟ VO2max we recommend using 15 breath moving average sampling intervals with a VO2 plateau defined as ≤50 mL·min-1 for any future maximal exercise testing in people with CVD.