Mapelli M; Centro Cardiologico Monzino IRCCS, Milan, Italy.
Puttini F; Mattavelli I; Salvioni E; Galotta A; Ferrarini G;
Canevari M; Willixhofer R; Caputo R; Costantino S; Biroli M; Lustri C;
Grandi D; Teglia A; Valenti M; Agostoni P
Headings added by Dr Older

Background Body posture influences cardiovascular and respiratory responses during
exercise, yet in a clinical setting, differences in body positions are not
considered when comparing different methodologies analyzing physical
effort, such as cardiopulmonary exercise testing (CPET), stress echo, or
invasive hemodynamic. We aimed to investigate how upright (UP),
semirecumbent (SR), and supine (SP) positions affect key CPET variables
and cardiac output (CO) in healthy adults.
Methods Twelve healthy volunteers (30.9
+/- 4.4 yr; 50% female) performed three randomized CPETs in UP, SR, and SP
positions. Breath-by-breath gas exchange data [oxygen uptake (Vo2) carbon
dioxide production (Vco2), minute ventilation (Ve), tidal volume (TV),
respiratory rate (RR)] and hemodynamic parameters [CO by thoracic
bioimpedance, stroke volume (SV), heart rate (HR)] were continuously
monitored. Data were analyzed at rest, anaerobic threshold, iso-watt
stages, and peak exercise.
Results At rest and submaximal workloads, HR decreased,
and SV increased with more reclined positions, maintaining CO. Ve and TV
were lower in SR and SP positions, whereas RR and peripheral oxygen
saturation ([Formula: see text]) were unchanged. At peak exercise, Vo2,
Vco2, workload, and exercise duration declined progressively from UP to SP
(Vo2: 2,587 +/- 1,009, 2,520 +/- 982, 2,269 +/- 847 mL/min; P < 0.001),
with lower Ve driven by reduced TV. Despite reduced metabolic and
ventilatory demands, CO was unchanged via increased SV. Dyspnea perception
was lower in reclined postures. Body posture modulates cardiopulmonary
responses during exercise. Semirecumbent and supine positions reduce Vo2
and Ve preserving CO.
Conclusons These findings highlight the importance of
posture-specific reference values for accurate interpretation in clinical
practice. NEW & NOTEWORTHY Body position during exercise testing
profoundly affects cardiopulmonary responses, even in healthy individuals.
Results obtained in different postures are not directly comparable.
Upright, semirecumbent, and supine exercise produce systematic changes in
oxygen uptake, ventilation, workload, and dyspnea, with lower performance
in reclined positions. Despite this, cardiac output is preserved through
adjustments in heart rate and stroke volume, indicating that
posture-rather than cardiac dysfunction-drives differences. Without
posture-specific reference values, disease severity may be misinterpreted.