Discriminating circulatory problems with reduced stroke volume from de-conditioning in which the muscles cannot consume O2 normally by gas exchange parameters is difficult.
We performed combined stress echo and cardio-pulmonary (CPET) tests in 110 patients (20 normal effort capacity, 54 attenuated stroke volume response, 36 de-conditioning) to evaluate multiple hemodynamic parameters and oxygen content difference (A-VO2 Difference) in four predefined activity levels to assess which of the gas measures may help in the discrimination.
Reduced anaerobic threshold (AT), low unchanging peak O2 pulse, periodic breathing, shallow ΔVO2/Δ work rate (WR) ratio, and high VE/VCO2 slope were all associated with abnormal stroke volume response (p<0.05 for all). The best discriminator was VE/VCO2 slope to peak VO2 ratio (≥2.7; AUC 0.79: p<0.0001). The optimal gas exchange model included ΔVO2/Δ work rate<8.6, VE/VCO2 slope to peak VO2 ratio ≥2.7, and periodic breathing (AUC of 0.84, p<0.0001).
The best single gas exchange parameter to discriminate between circulatory problems to de-conditioning is VE/VCO2 slope to peak VO2 ratio.