Open AccessCardiodynamic variables measured by impedance cardiography during a 6-minute walk test are reliable predictors of peak oxygen consumption in young healthy adults
Author(s) -
Fang Liu,
Raymond C. C. Tsang,
Alice Jones,
Mingchao Zhou,
Kaiwen Xue,
Miao-Ling Chen,
Yulong Wang
Publication year - 2021
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0252219
Subject(s) - impedance cardiography , stroke volume , vo2 max , medicine , cardiology , heart rate , linear regression , mathematics , exercise prescription , cardiac output , regression analysis , statistics , physical therapy , blood pressure , hemodynamics
Accurate prediction of aerobic capacity is necessary to guide appropriate exercise prescription. It is common to use 6-minute walk distance (6MWD) to predict peak oxygen uptake (VO 2peak ) in the clinical environment. The aim of this study was to determine whether prediction of VO 2peak can be improved by the inclusion of cardiovascular indices derived by impedance cardiography (ICG) during the 6MWT. A total of 62 healthy university students aged 21±1 years completed in separate days, a cardiopulmonary exercise test (CPET) and two 6MWTs (30 min apart), during which heart rate (HR), stroke volume (SV) and cardiac output (CO) were measured by ICG (PhysioFlow ® PF07 Enduro TM ). The CPET was conducted with the Ergoselect 200 Ergoline and oxygen consumption measured by a MasterScreen TM CPX breath-by-breath metabolic cart. Multiple regression analyses were conducted to generate VO 2peak prediction equations using 6MWD with, or without the cardiovascular indices recorded at the end of the best performed 6MWT as predictor variables. The mean peak HR (bpm), SV (ml) and CO (L/min) recorded during 6MWT were 156±18, 95.6±9, 15±2.8 and during CPET were 176±16, 91.3±8, 16.2±2.7, respectively. Analyses revealed the following VO 2peak prediction equation: VO 2peak = 100.297+(0.019x6MWD)+(-0.598xHR 6MWT )+(-1.236xSV 6MWT ) + (8.671 x CO 6MWT ). This equation has a squared multiple correlation ( R 2 ) of 0.866, standard error of the estimate (SEE) of 2.28 mL/kg/min and SEE:VO 2peak (SEE%) of 7.2%. Cross-validation of equation stability using predicted residual sum of squares (PRESS) statistics showed a R 2 ( R p 2 ), SEE (SEE p ) and SEE p % of 0.842, 2.38 mL/kg/min and 7.6% respectively. The minimal shrinkage of R 2 implied regression model stability. Correlation between measured and predicted VO 2peak using this equation was strong (r = 0.931, p<0.001). When 6MWD alone was used as the predictor for VO 2peak , the generated equation had a lower R 2 (0.549), and a higher SEE (4.08 mL/kg/min) and SEE% (12.9%). This is the first study which included cardiac indices during a 6MWT as variables for VO 2peak prediction. Our results suggest that inclusion of cardiac indices measured during the 6MWT more accurately predicts VO 2peak than using 6MWD data alone.