Exercise End-Tidal CO 2 Predicts Central Sleep Apnea in Patients With Heart Failure

Abstract

BACKGROUND:Increased CO 2 chemosensitivity and augmented exercise ventilation are characteristic of patients with heart failure (HF) with central sleep apnea (CSA). Th e aim of this study was to test the hypothesis that decreased end-tidal CO 2 by cardiopulmonary exercise testing predicts CSA in patients with HF.

Resting End-Tidal Carbon Dioxide Predicts Respiratory Complications in Patients Undergoing Thoracic Surgical Procedures

“…In our study, _ VE/ _ VCO 2 slope correlated with peak exercise PETCO 2 (rho ¼ À0.79; p < 0.01) and also with resting PETCO 2 (rho ¼ À0.59; p < 0.01), a finding suggesting that the mechanisms underlying elevated _ VE/ _ VCO 2 and decreased PETCO 2 may not be limited to exercise and may also be present at rest. This concept is supported by other studies showing that patients with high _ VE/ _ VCO 2 and low PETCO 2 at peak exercise had increased _ VE/ _ VCO 2 and low PETCO 2 at rest [6,7]. Therefore, the common underlying mechanisms of _ VE/ _ VCO 2 and PETCO 2 may explain the PETCO 2 association with pulmonary complications and may justify its use as a prognostic marker for perioperative risk assessment.…”

“…Underlying mechanisms that alter _ VE/ _ VCO 2 seem to operate during exercise as well as at rest. Indeed, patients with an increased _ VE/ _ VCO 2 ratio and a low partial pressure of end-tidal CO 2 (PETCO 2 ) during peak exercise have been shown to have an increased _ VE/ _ VCO 2 ratio and a low PETCO 2 at rest also [6,7], a finding suggesting that resting ventilatory measurements may have value for risk prediction. Identification of a simple, easy to obtain resting ventilatory measurements that effectively predicts respiratory complications and death after thoracotomy may be useful because many patients are not able or are unwilling to perform CPET [8].…”

Pulmonary Limitations in Heart Failure

“…P ET CO 2 may be decreased by hyperventilation and by increased dead space ventilation, i.e., by the same factors which determine V E /VCO 2 6 , suggesting the parameters are closely related 61 . In our previous studies we have shown HF patients with low P ET CO 2 and increased V E /VCO 2 at peak exercise also exhibit low P ET CO 2 and increased V E /VCO 2 at rest 7,66 suggesting factors which promote high V E /VCO 2 and low P ET CO 2 may not be limited to exercise.…”

“…Ventilatory control is frequently abnormal in patients with advanced HF and manifests as hyperventilation at rest 5 , during exercise 6 and with sleep 7 . The presence of hyperventilation has been associated with decreased functional capacity 6 , more severe symptoms 42 and increased mortality 43 in HF patients.…”

“…Heart failure directly impacts 1) lung mechanics due to congestion and increased heart size which promote airway obstruction and lung restriction 1,2 , 2) high pulmonary pressures as well as pulmonary congestion contributes to remodeling of the pulmonary capillaries, increased ventilation-perfusion mismatch and decreased alveolar-capillary diffusion 3,4 and 3) disordered ventilatory control including hyperventilation at rest, during exercise and with sleep [5][6][7] . These pulmonary system changes cause decreased breathing reserve combined with enhanced ventilation for a given metabolic demand (minute ventilation (⩒E)/pulmonary carbon dioxide output (⩒CO 2 ) ratio) at rest and during exercise 7,8 . In this review, we discuss heart failure (HF) related changes in lung mechanics, gas exchange and ventilatory control as well as their impact on the limitation of exercise capacity, sleep disordered breathing and prognosis of HF patients.…”