September 22, 2022

Reduced exercise capacity in ICU survivors

ICU survivors who have impaired exercise capacity months after discharge may have damaged muscle mitochondria — the energy powerhouses of the cell, Vanderbilt researchers propose.

Intensive care unit (ICU) patients can suffer from reduced ability to exercise for years after their critical illness.

To explore the mechanisms that drive this lingering impairment, Matthew Mart, MD, MSCI, and colleagues investigated the exercise capacity of 14 patients treated for respiratory failure and/or shock in the ICU six months after discharge.

Oxygen consumption and heart rate were monitored during cardiopulmonary exercise testing on stationary bicycles and six-minute walk testing.

Low exercise capacity was present in 11 of the 14 patients. Their physiological responses to exercise were suggestive of impaired muscle oxygen utilization observed in patients with mitochondrial myopathies (mitochondrial dysfunction within muscle). As the “powerhouse” of the cell responsible for converting oxygen to energy, mitochondria are vital during exercise.

Reporting in the journal Intensive Care Medicine Experimental. the researchers hypothesize that damage to mitochondria during early critical illness may contribute to long-term impaired exercise capacity in ICU patients. They recommend future studies of mitochondrial function in ICU survivors to confirm these results.

Co-authors are Wesley Ely, MD, MPH, James Tolle, MD, Mayur Patel, MD, MPH, and Nathan Brummel, MD, MSCI. This study was supported by National Institutes of Health grants AG054864, HL087738, and TR002243, and by the Vanderbilt University Medical Center Arthur and Lisa Wheeler Critical Care Research Grant.