Background: The oxygen uptake efficiency slope (OUES) is the most important index for accurately measuring cardiopulmonary function in patients with acute ischemic heart disease. However, the relationship between the OUES variables and important cardiopulmonary function parameters remain unelucidated for patients with acute ischemic heart disease, which accounts for the largest proportion of heart disease.
Objects: The present cross sectional clinical study aimed to determine the multiple relationships among the cardiopulmonary function variables mentioned above in adults with acute ischemic heart disease.
Methods: A convenience sample of 110 adult inpatients with ischemic heart disease (age: 57.4 ± 11.3 y; 95 males, 15 females) was enrolled at the hospital cardiac rehabilitation center. The correlation between the important cardiopulmonary function indicators including peak oxygen uptake (VO2 peak), minute ventilation (VE)/carbon dioxide production (VCO2) slope, heart rate recovery (HRR), and ejection fraction (EF) and OUES was confirmed.
Results: This study showed that OUES was highly correlated with VO2 peak, VE/VCO2 slope, and HRR parameters.
Conclusion: The OUES can be used as an accurate indicator for cardiopulmonary function. There are other factors that influence aerobic capacity besides EF, so there is no correlation with EF. Effective cardiopulmonary rehabilitation programs can be designed based on OUES during submaximal exercise in patients with acute ischemic heart disease.

INTRODUCTION
MATERIALS AND METHODS
    1. Participants and Experimental Procedure
    2. Cardiopulmonary Exercise Test
    3. Oxygen Uptake Efficiency Slope
    4. VO2 Peak
    5. VE/VCO2 Slope
    6. Heart Rate Recovery
    7. Echocardiography
    8. Statistical Analysis
RESULTS
DISCUSSION
CONCLUSIONS
FUNDING
ACKNOWLEDGEMENTS
CONFLICTS OF INTEREST
AUTHOR CONTRIBUTIONS
ORCID
REFERENCES

• Jeong Jae Lee(Sports Movement Artificial-Intelligence Robotics Technology (SMART) Institute, Department of Physical Therapy, Yonsei University, Wonju, Rehabilitation Team, Myongji Hospital, Goyang, Korea)
• Chan-hee Park(Sports Movement Artificial-Intelligence Robotics Technology (SMART) Institute, Department of Physical Therapy, Yonsei University, Wonju)
• Joshua (Sung) Hyun You(Sports Movement Artificial-Intelligence Robotics Technology (SMART) Institute, Department of Physical Therapy, Yonsei University, Wonju) Corresponding Author