Siebold E; Division of Sport and Exercise Medicine, Basel, Switzerland.
Infanti L; Gruber HJ; Stehle GT; et al

European Journal of Applied Physiology. 126(7):4113-4126, 2026 Jul.

Respiratory gas exchange during cardiopulmonary exercise testing (CPET) is
commonly measured using either a mixing chamber (MC) or a breath-by-breath
(BxB) technique. MC measurements reduce the impact of erratic ventilatory
patterns, thereby improving the accuracy of oxygen uptake ([Formula: see
text]) values, but often lack adequate temporal resolution for ventilatory
thresholds (VTs) determination. Accordingly, BxB is preferred when both
[Formula: see text] and VTs determination are sought simultaneously.
Recently, an adaptive mixing chamber (aMC) with high temporal resolution
was developed. The aims of this study were to examine the concordance of
aMC- and BxB-derived gas exchange data and to determine if the aMC
provides adequate temporal resolution for the assessment of VTs. Fourteen
healthy, recreationally active individuals (7 females, 7 males; 23.6 +/-
1.4 yr; 171.8 +/- 9.0 cm; 67.9 +/- 11.1 kg) performed a maximal CPET on a
treadmill with gas exchanges being measured simultaneously using BxB and
aMC techniques. Compared with BxB measurement, [Formula: see text] values
at peak effort were 5.0 +/- 7.8% lower using the aMC (P = 0.0419). Similar
bias was observed for [Formula: see text] values obtained at submaximal
workloads. Notably, the aMC provided adequate temporal resolution to
identify VTs among all participants in whom they could be measured with
confidence using BxB (n = 13/14). The aMC provides consistently and
reproducibly lower [Formula: see text] values compared with BxB
acquisition and provides adequate temporal resolution to determine VTs
during incremental effort CPET. This newly developed technology appears to
integrate the well-established strengths of both conventional MC and BxB
gas exchange measurement techniques. NEW & NOTEWORTHY COSMED recently
developed an adaptive mixing chamber (aMC) designed to pair the accuracy
of traditional mixing chambers with improved temporal resolution. This
study establishes the agreement between the aMC and breath-by-breath (BxB)
systems and demonstrates that the aMC consistently enabled ventilatory
threshold detection whenever BxB did. These findings indicate that the aMC
retains optimal gas-exchange measurement quality while enabling reliable
ventilatory threshold identification.