A simplified approach for the estimation of the ventilatory compensation point

Incremental cardiopulmonary exercise test with gas exchange measurement is the gold standard for the identification of the ventilatory compensation point (VCP). It has previously been demonstrated that the change in the slope of increment of minute ventilation over HR (ΔV˙E/ΔHR) can be used alternatively to the ventilatory equivalent for CO₂ (V˙E/V˙CO₂) method for detection of VCP in healthy subjects undergoing cycle ergometer (C) incremental exercise. The same evaluation during treadmill (T) incremental exercise and comparison between C and T have not yet been performed.

We analyzed, during both C and T incremental exercises, the V˙E/HR and the respiratory rate (RR)/HR relationships, expressed either as slope or as an absolute value. We hypothesized that changes in the slope of increment of the two relationships could represent a reliable method for VCP detection, regardless of exercise mode and protocol.

Fourteen healthy male subjects (age = 31 ± 7 yr (mean ± SD)) underwent two T incremental exercises--fast (FT) and slow (ST) protocols (8 km·h⁻¹, 2% (F(T)) and 1% (S(T)) grade per minute)--and one C incremental exercise (30 W·min⁻¹). O₂ uptake (V˙O₂), V˙CO₂, V˙E, HR, and RR were measured breath by breath.

A good between-method agreement in the detection of VCP by the ΔV˙(E)/ΔV˙CO₂, ΔV˙(E)/ΔHR, and the ΔRR/ΔHR slope changes was found in both T protocols and C. No differences (C vs T and F(T) vs S(T)) were found in the slope of the ΔV˙(E)/ΔHR and ΔRR/ΔHR relationships after the VCP and in the V˙(E)/HR and RR/HR absolute values at VCP.

In healthy young males, the ΔV˙E/ΔHR and ΔRR/ΔHR relationships during T and C incremental exercises can be reliably used to detect the VCP as an alternative to the ventilatory equivalent method.