OBJECTIVEMeasures of ventilation-CO₂output relationship have been shown to be more prognostic than peak O₂uptake in assessing life expectancy in patients with chronic heart failure (CHF). Because both the ratios (VE/Vco₂) and slopes (VE-vs-Vco₂) of ventilation-co₂ output of differing durations can be used, we aim to ascertain which measurements best predicted CHF life expectancy.

METHODSTwo hundred and seventy-one CHF patients with NYHA class II-IV underwent incremental cardiopulmonary exercise testing (CPET) and were followed-up for a median duration of 479 days. Four different linear regression VE-vs- Vco₂ slopes were calculated from warm-up exercise onset to: 180 s, anaerobic threshold (AT), ventilatory compensation point (VCP); and peak exercise. Five VE/Vco₂ ratios were calculated for the following durations: rest (120 s), warm-up (30 s), AT (60 s), lowest value (90 s), and peak exercise (30 s). Death or heart transplant were considered end-points. Multiple statistical analyses were performed.

RESULTSCHF patients had high lowest VE/Vco₂ (41.0 ± 9.2, 141 ± 30%pred), high VE/Vco₂ at AT (42.5 ± 10.4, 145 ± 35%pred), and high VE-vs-Vco₂ slope to VCP (37.6 ± 12.1, 126 ± 41%pred). The best predictor of death was a higher lowest VE/Vco₂ (≥ 42, ≥ 141%pred), whereas the VE-vs-Vco₂slope to VCP was less variable than other slopes. For death prognosis in 6 months, %pred values were superior: for longer times, absolute values were superior.

CONCLUSIONThe increased lowest VE/Vco₂ ratio easily identifiable and simply measured during exercise, is the best measurement to assess the ventilation-co₂output relationship in prognosticating death in CHF patients.

Carbon Dioxide ; metabolism ; Chronic Disease ; Disease Progression ; Exercise Test ; Heart Failure ; diagnosis ; mortality ; physiopathology ; Humans ; Life Expectancy ; Respiratory Function Tests

OBJECTIVETo observe oxygen uptake efficiency plateau (OUEP, i.e.highest V˙O2/V˙E) and carbon dioxide output efficiency (lowest V˙E/V˙CO2) parameter changes during exercise in normal subjects.

METHODSFive healthy volunteers performed the symptom limited maximal cardiopulmonary exercise test (CPET) at Harbor-UCLA Medical Center. V˙O2/V˙E and V˙E/V˙CO2 were determined by both arterial and central venous catheters. After blood gas analysis of arterial and venous sampling at the last 30 seconds of every exercise stage and every minute of incremental loading, the continuous parameter changes of hemodynamics, pulmonary ventilation were monitored and oxygen uptake ventilatory efficiency (V˙O2/V˙E and V˙E/V˙CO2) was calculated.

RESULTSDuring CPET, as the loading gradually increased, cardiac output, heart rate, mixed venous oxygen saturation, arteriovenous oxygen difference, minute ventilation, minute alveolar ventilation, tidal volume, alveolar ventilation and pulmonary ventilation perfusion ratio increased near-linearly (P < 0.05-0.01, vs.resting); arterial oxygen concentration maintained at a high level without significant change (P > 0.05); stroke volume, respiratory rate, arterial partial pressure of carbon dioxide, arterial blood hydrogen ion concentration and dead space ventilation ratio significantly changed none-linearly (compare resting state P < 0.05-0.01).OUE during exercise increased from 30.9 ± 3.3 at resting state to the highest plateau 46.0 ± 4.7 (P < 0.05 vs.resting state), then, declined gradually after anaerobic threshold (P < 0.05-0.01, vs.OUEP) and reached 36.6 ± 4.4 at peak exercise. The V˙E/V˙CO2 during exercise decreased from the resting state (39.2 ± 6.5) to the minimum value (24.2 ± 2.4) after AT for a few minutes (P > 0.05 vs.earlier stage), then gradually increased after the ventilatory compensation point (P < 0.05 vs.earlier stage) and reached to 25.9 ± 2.7 at peak exercise.

CONCLUSIONSCardiac and lung function as well as metabolism change during CPET is synchronous.In the absence of pulmonary limit, appearing before and after anaerobic threshold, OUEP and lowest V˙E/V˙CO2 could be used as reliable parameters representing the circulatory function.

Arteries ; Blood Gas Analysis ; Blood Pressure ; Carbon Dioxide ; metabolism ; Cardiac Output ; Exercise ; physiology ; Exercise Test ; Heart ; Heart Rate ; Hemodynamics ; Humans ; Lung ; Oxygen ; metabolism ; Oxygen Consumption