Relationship between oxygen pulse and arteriovenous oxygen difference in healthy subjects: Effect of exercise intensity

Estimation of peak oxygen pulse from body mass, resting heart rate, age, gender and systolic blood pressure in Chinese adults aged 20-39

Background

Peak oxygen pulse (O2Ppeak) can reflect the condition of cardiovascular function and provide supplementary information for maximal oxygen uptake, but its direct measurement requires the precise instruments under the guidance of professionals, and the subjects should strive to the state of exhaustion.

Objectives

The aim of the present cross-sectional study was to establish a prediction equation to estimate O2Ppeak of Chinese adults aged 20-39, from routine measures of anthropometry and cardiovascular function.

Methods

252 adults (20-39 years old) were recruited and randomly allocated to the validation group (n = 226) and the cross-validation group (n = 26). To be included in the study, subjects were required to be healthy, none-professional sports experience (healthy individuals who are not athletes or have had experience as athletes), and no medication taken recently. Subjects with cardiovascular diseases, lung disease and musculoskeletal diseases were excluded. The subjects' anthropometric and cardiovascular variables were measured and each subject performed a maximal exercise test on an electromagnetic cycle ergometer.

Results

The O2Ppeak estimated equation was developed using multiple linear regression models, O2Ppeak = 30.394 + 0.083 x body mass (kg) - 0.090 x resting heart rate (bpm) - 0.157 x age (years) - 2.710 x gender (1 = male, 2 = female) - 0.035 x systolic blood pressure (mmHg). The equation had the coefficient of determination (R2) = 0.804 and the standard error of estimate (SEE) = 1.619 ml/beat. An ANOVA and Akaike's information criterion (AIC) were tested. Bland-Altman graphs were plotted to examine the distribution of bias. Cross-validation estimated O2Ppeak and directly measured O2Ppeak did not show significant difference while had a strong positive correlation (r = 0.89, p < 0.001).

Conclusions

The established equation has high effectiveness and reliability to predict O2Ppeak of adults aged 20-39.

Revisiting cardiac output estimated noninvasively from oxygen uptake during exercise: an exploratory hypothesis-generating replication study

Stringer et al. [J Appl Physiol (1985) 82: 908-912, 1997] developed a method from invasive data to estimate cardiac output during incremental exercise testing based on Fick's principle. The authors proposed that the arterio-mixed venous oxygen content difference increases linearly with percentage of maximal O2 consumption. We hypothesized an S-shaped pattern in the published data and calculated the inflection point of this curve and of the standard resting oxygen dissociation curve. Using a partial F test, we compared the linear model with a third-order polynomial model, which showed a better fit to the data [F(2,101) = 9.5, P < 0.001]. This finding was reproduced in a dataset published by Åstrand et al. in 1964 [F(2, 122) = 10.6, P < 0.001]. The inflection point of the curve coincided with the lactate acidosis threshold [first ventilatory threshold (VT1)] as measured by Stringer et al. (VT1 at 50% and inflection point at 56% [95% CI, 52.9 to 60.7] of maximal O2 consumption). The inflection point of the standard resting oxygen dissociation curve was calculated at a partial pressure of 21.5 mmHg and a saturation of 36%, matching the "critical capillary Po2" concept of Stringer et al. (21.2 mmHg). We conclude that the arterio-mixed venous oxygen content difference increases in an S-shaped manner with percentage of maximal oxygen consumption and that the inflection point of this curve may correspond to VT1 and that of the in vivo oxygen dissociation curve. Further research is needed to confirm these findings and improve the method.NEW & NOTEWORTHY In 1997, Stringer, Hansen, and Wasserman developed a method for estimating cardiac output during incremental exercise testing. They observed that the arterio-mixed venous oxygen content difference increases linearly with the percentage of maximal O2 consumption. This increase may be better modelled by an S-shaped function, the inflection point of which may be related to the first ventilatory threshold and the inflection point of the oxygen dissociation curve. This finding may help to improve the method.

Early Cardiopulmonary Fitness after Heart Transplantation as a Determinant of Post-Transplant Survival

BACKGROUND

Decreased peak oxygen consumption during exercise (peak Vo₂) is a well-established prognostic marker for mortality in ambulatory heart failure. After heart transplantation, the utility of peak Vo₂ as a marker of post-transplant survival is not well established.

METHODS AND RESULTS

We performed a retrospective analysis of adult heart transplant recipients at the Hospital of the University of Pennsylvania who underwent cardiopulmonary exercise testing within a year of transplant between the years 2000 to 2011. Using time-to-event models, we analyzed the hazard of mortality over nearly two decades of follow-up as a function of post-transplant percent predicted peak Vo₂ (%Vo₂). A total of 235 patients met inclusion criteria. The median post-transplant %Vo₂ was 49% (IQR 42 to 60). Each standard deviation (±14%) increase in %Vo₂ was associated with a 32% decrease in mortality in adjusted models (HR 0.68, 95% CI 0.53 to 0.87, p = 0.002). A %Vo₂ below 29%, 64% and 88% predicted less than 80% survival at 5, 10, and 15 years, respectively.

CONCLUSIONS

Post-transplant peak Vo₂ is a highly significant prognostic marker for long-term post-transplant survival. It remains to be seen whether decreased peak Vo₂ post-transplant is modifiable as a target to improve post-transplant longevity.

Interchangeability and optimization of heart rate methods for estimating oxygen uptake in ergometer cycling, level treadmill walking and running

Background

The heart rate (HR) method enables estimating oxygen uptake (V̇O₂) in physical activities. However, there is a paucity in knowledge about the interchangeability of this method when applied to cycling, walking and running. Furthermore, with the aim of optimization, there is a need to compare different models for establishing HR-V̇O₂ relationships.

Methods

Twenty-four physically active individuals (12 males and 12 females) participated. For each participant, two models of HR-V̇O₂ relationships were individually established in ergometer cycling, level treadmill walking and running. Model 1 consisted of five submaximal workloads, whereas model 2 included also a maximal workload. Linear regression equations were used to estimate V̇O₂ at seven intensity levels ranging between 25 and 85% of heart rate reserve (HRR). The estimated V̇O₂ levels were compared between the exercise modalities and models, as well as with data from a previous study.

Results

A high level of resemblance in estimated V̇O₂ was noted between running and cycling as well as between running and walking, with both model 1 and model 2. When comparing walking and cycling, the V̇O₂ levels for given intensities of %HRR were frequently slightly higher in walking with both models (range of significant differences: 5–12%). The variations of the estimated individual V̇O₂ values were reduced when using model 2 compared to model 1, both between and within the exercise modalities.

Conclusion

The HR method is optimized by more workloads and wider ranges. This leads to overall high levels of interchangeability when HR methods are applied in ergometer cycling, level treadmill walking and running.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-022-01524-w.