High-intensity interval training to improve cardiorespiratory fitness in a patient with frailty and multimorbidity: A case report.

Abstract

Background: Low cardiorespiratory fitness predicts worse postoperative outcomes, exacerbated by age and frailty. Preoperative High-Intensity Interval Training (HIIT) improves cardiorespiratory fitness and postoperative outcomes but is challenging to implement in frailty due to perceived risks.

Purpose: The aim of this case report was to demonstrate feasibility of HIIT in a patient with frailty and multimorbidity.

Case presentation: An 83-year-old frail male with atrial fibrillation and limited mobility presenting with locally advanced rectal cancer was assessed as unfit for major surgery unless his cardiorespiratory fitness improved. Initial cardiopulmonary exercise testing demonstrated low cardiorespiratory fitness (peak oxygen consumption ($\dot{V}$O_2peak) of 11.45 mL·min^-1·kg^-1). He subsequently underwent 15 supervised HIIT sessions targeting a Rating of Perceived Exertion ≥ 15.

Outcomes: The patient demonstrated initial substantial improvements in his physical condition, increasing maximal work rate from 27.5 W to 55 W. However, there was no additional progress following session eight. At his post-exercise CPET he rapidly fatigued, resulting in a $\dot{V}$O_2peak of 7.4 mL·min^-1kg^-1. Clinical investigations revealed a worsening anemia with a hemoglobin of 92 g/L caused by an undiagnosed synchronous cecal tumor which was corrected preoperatively. Postoperatively, the patient recovered without complications and was successfully discharged home.

Conclusion: Personalized HIIT improved exercise duration and work rate and was associated with positive postoperative outcomes in this patient with frailty and multimorbidity. A unique feature of this case was the unexpected loss of training progress and $\dot{V}$O_2peak deterioration post-HIIT, which prompted further clinical investigations. These identified a worsening anemia and resulted in important changes in both the preoperative and intraoperative treatment.