Why women are not small men: sex-related differences in perioperative cardiopulmonary exercise testing

Abstract

Background: The use of preoperative cardiopulmonary exercise testing (CPET) to evaluate the risk of adverse perioperative outcomes is increasingly prevalent. CPET-derived information enables personalised perioperative care and enhances shared decision-making. Sex-related differences in physical fitness are reported in non-perioperative literature. However, little attention has been paid to sex-related differences in the context of perioperative CPET. Aim: We explored differences in the physical fitness variables reported in a recently published multi-centre study investigating CPET before colorectal surgery. We also report the inclusion rate of females in published perioperative CPET cohorts that are shaping guidelines and clinical practice. Methods: We performed a post hoc analysis of the trial data of 703 patients who underwent CPET prior to major elective colorectal surgery. We also summarised the female inclusion rate in peer-reviewed published reports of perioperative CPET. Results: Fitness assessed using commonly used perioperative CPET variables-oxygen consumption at anaerobic threshold (AT) and peak exercise-was significantly higher in males than in females both before and after correction for body weight. In studies contributing to the development of perioperative CPET, 68.5% of the participants were male. Conclusion: To our knowledge, this is the first study to describe differences between males and females in CPET variables used in a perioperative setting. Furthermore, there is a substantial difference between the inclusion rates of males and females in this field. These findings require validation in larger cohorts and may have significant implications for both sexes in the application of CPET in the perioperative setting.

Editorial: Prime time to recommend sex‐specific cardiorespiratory fitness threshold values for pre‐operative risk stratification

“…Additional support for their approach comes from Elmariah et al 13 who found that women with heart failure had lower VȮ 2peak values than their male counterparts, yet had better 1-year survival outcomes. Thomas et al 14 also found significantly lower VȮ 2peak and AT values in females awaiting major colorectal surgery but also reported no sex differences in mortality or morbidity. Like Rose and colleagues, the respective authors both concluded that the application of universal CRF thresholds was inappropriate and called for sex-specific pre-operative CPET thresholds to be included in future guidelines.…”

“…The sex‐specific thresholds (dashed lines) represent the reformulated female (V̇O 2peak <11.9 mL kg −1 min −1 and V̇E/V̇CO 2 ‐AT >35) and male (V̇O 2peak 14.9 mL kg −1 min −1 and V̇E/V̇CO 2 ‐AT >33) specific thresholds proposed by Rose et al to normalise and account for the well‐recognised sex‐differences in cardiorespiratory fitness. Panel A based upon data shown by Kaminsky et al, 12 and Panel B adapted from Thomas et al 14 …”

‘Fit for surgery’: the relationship between cardiorespiratory fitness and postoperative outcomes

“…Female inclusion rate in peer‐reviewed publications of perioperative CPET is reported at only 31% and may have a bearing on the interpretation of data (Thomas et al., 2020). Surprisingly, despite evidence that CRF is lower in females across the lifespan, given smaller body size, skeletal muscle mass, peak cardiac output and Hb concentration (Jackson et al., 2009; Fleg et al., 2005), sex is not considered during surgical risk stratification.…”

Assessing cardiorespiratory fitness relative to sex improves surgical risk stratification

“…Preoperative CPET is used to identify patients with low CRF which is an established predictor of survival following major intra‐abdominal surgery 5–9 . When comparing the sexes, female patients demonstrate lower preoperative CRF than males 10 . However, to what extent sex differences in CRF influence preoperative risk stratification and corresponding ‘normalization’ approaches to optimize the latter has not previously been investigated.…”

“…[5][6][7][8][9] When comparing the sexes, female patients demonstrate lower preoperative CRF than males. 10 However, to what extent sex differences in CRF influence preoperative risk stratification and corresponding 'normalization' approaches to optimize the latter has not previously been investigated.…”