Ventilatory inefficiency during graded exercise in COPD: A pragmatic approach

Abstract

Background/Objective The current approach to measuring ventilatory (in)efficiency (V′E‐V′CO2 slope, nadir and intercept) presents critical drawbacks in the evaluation of COPD subjects, owing mainly to mechanical ventilatory constraints. Thus, we aimed to compare the current approach with a new method we have developed for ventilatory efficiency calculation. Methods The new procedure was based on measuring the amount of CO2 cleared by the lungs (V′CO2, L/min) plotted against a predefined range of increase in minute ventilation (V′E) (ten‐fold increase based on semilog scale) during incremental exercise to symptom‐limited maximum tolerance. This value was compared to a hypothetical predicted maximum CO2 output at the predicted maximal voluntary ventilation, defining ventilatory efficiency (ηV′E, %). The results were used to compare 30 subjects with COPD (II‐IV Global Initiative for Chronic Obstructive Lung Disease, GOLD) and 10 non‐COPD smokers, to establish the best discriminative physiological variable for disease severity through logistic multinomial regression. Results The new approach was more sensitive to progressive deterioration of airway obstruction, resulting in worse ηV′E as lung function worsens throughout the GOLD panel (ηV′E (%), p < .001), when compared with V′E‐V′CO2 slope (p = .715) or V′E‐V′CO2 nadir (p = .070), besides showing the best model based on the logistic regression approach. Conclusion Although requiring more complex calculations compared to the current procedure, the new approach is highly sensitive to true ventilatory/gas‐exchange deterioration, even throughout more severe pulmonary lung function in COPD subjects.

Ventilatory efficiency (η⩒E) of the exercise: A detailed method report

“…The method presented herein is an alternative to the ⩒ E- ⩒CO 2 slope, and the first effort at a detailed description of ventilatory efficiency of the exercise (η ⩒ E ), that is consistent with the true designation of “efficiency” in biology/physiology [13] , characterized by the following criteria: (i) “efficiency is a measure of performance that characterizes an actual performance relative to a perfect level” , (ii) and “ must be preferentially presented as a fraction (percentage) of a single process” . This paper substantially improves the method previously published by the same author for validation [ 6 , 14 ].…”

“…However, there are several points that remain inconclusive with respect to the reliability of the ⩒ E- ⩒CO 2 slope. Thus, among the limitations of the ⩒ E- ⩒CO 2 slope are (i) the recognized effects of ventilatory mechanical constraints in down-shifting the ⩒ E- ⩒CO 2 slope [5 , 6] , (ii) the imprecise use of the designation “ventilatory efficiency” with respect to the ⩒ E- ⩒CO 2 slope [ 7 , 8 ], (iii) the imprecise application of linear regression for a quadratic function, that fits better when using the whole exercise time-frame, including the post respiratory compensation point (RCP) data [1] , (iv) the use of a smaller sample of data points for the linear segment of the ⩒ E- ⩒CO 2 response, excluding data on remarkable physiological ventilatory responses after the RCP [9] , and (v) the effects of primary hyperventilation [7] . In addition, (vi) severe acidosis could up-shift the ⩒ E- ⩒CO 2 slope at the level comparable with cardiopulmonary disease (slope > 35) in athletes [10] , and (vii) recently, several limitations of the ⩒ E- ⩒CO 2 slope for endpoint prognostication in cardiopulmonary diseases were described [ 11 , 12 ].…”

Carotid-body modulation through meditation in stage-I hypertensive subjects: Study protocol of a randomized and controlled study

“…Incremental CPET followed the routine of our laboratory and has been previously published. [ 55 , 56 ] First, after strict recommendations for abstinence from stimulants and depressants and using only habitual medication, the individuals will be stimulated to pedal to 60 cycles minute -1 after 2-minutes of rest and 2-minutes of warm-up toward maximum work rate tolerance, meaning that they cannot pedal for more than 10 seconds over 50 cycles minute -1 under the stimulus of the examiner, and present subjective signs of intense exhaustion. The initial power of “0” W during the warm-up was increased by 16 W/minute -1 .…”

Ineficiência Ventilatória Comparável no Desempenho Máximo e Submáximo em Indivíduos com DPOC e ICC: Uma Abordagem Inovadora

“…Em pacientes com DPOC, baixa eficiência ventilatória durante o TECP está comumente associada à hiperinsuflação dinâmica, alta restrição ventilatória, e restrição à expansão do volume corrente (V T ). 5 Este fenótipo significa que mesmo naqueles com DPOC avançada, não é raro que haja ausência de padrão de hiperventilação de IC durante o TECP, 8 - 10 o que significa que a inclinação do não aumenta em conjunto com os fatores implicados com a ventilação anormalmente alta. Portanto, como fazer comparações de eficiência ventilatória entre pacientes usando a inclinação do pode ser desafiador, nós recentemente descrevemos um método alternativo para avaliar a eficiência ventilatória, cujo o propósito é permitir a comparação direta entre tipos de pacientes.…”