Ventilatory response to exercise in cardiopulmonary disease: the role of chemosensitivity and dead space

Abstract

The lungs and heart are irrevocably linked in their oxygen (O) and carbon dioxide (CO) transport functions. Functional impairment of the lungs often affects heart function and The steepness with which ventilation (') rises with respect to CO production (' ) ( the '/' slope) is a measure of ventilatory efficiency and can be used to identify an abnormal ventilatory response to exercise. The '/' slope is a prognostic marker in several chronic cardiopulmonary diseases independent of other exercise-related variables such as peak O uptake (' ). The '/' slope is determined by two factors: 1) the arterial CO partial pressure ( ) during exercise and 2) the fraction of the tidal volume () that goes to dead space () ( the physiological dead space ratio (/)). An altered set-point and chemosensitivity are present in many cardiopulmonary diseases, which influence'/' by affecting Increased ventilation-perfusion heterogeneity, causing inefficient gas exchange, also contributes to the abnormal'/' observed in cardiopulmonary diseases by increasing / During cardiopulmonary exercise testing, the during exercise is often not measured and/ is only estimated by taking into account the end-tidal CO partial pressure ( ); however, is not accurately estimated from in patients with cardiopulmonary disease. Measuring arterial gases ( and ) before and during exercise provides information on the real (and not "estimated")/ coupled with a true measure of gas exchange efficiency such as the difference between alveolar and arterial O partial pressure and the difference between arterial and end-tidal CO partial pressure during exercise.

Structure characterization and anticoagulant activity of a novel polysaccharide from Leonurus artemisia (Laur.) S. Y. Hu F

“…42 However, when the body is in a high coagulation state or when anticoagulation and brinolysis are weakened, thromboembolic diseases occur. 43 Thrombosis oen causes local blood coagulation in the vascular system, leading to health-related diseases including strokes and heart attacks. 44 Risk factors for thrombosis include abnormal hyperlipidemia, hyperglycemia elevated blood pressure and cancer.…”

The great breathlessness of cardiopulmonary diseases

“…The V′E/V′CO 2 versus PaCO 2 plot may thus be more informative than VD/VTphys to differentiate pulmonary and extrapulmonary determinants of hyperventilation. As also discussed by WEATHERALD et al [3] it is important to avoid under-estimation or over-estimations of PACO 2 by PETCO 2 in patients with abnormal breathing patterns [3]. This problem is minimised by measuring P(a−ET)CO 2 at the anaerobic threshold.…”

“…Excessive ventilation of high V′A/Q′ regions, or increased dead space ventilation does not affect PaCO 2 . However, as underscored by WEATHERALD et al [3], when both determinants of increased V′E/V′CO 2 coexist, quantifying the contribution of each is not simple.…”

“…WEATHERALD et al [3] discuss the two mean determinants of increased V′E/V′CO 2 : increased chemosensitivity and altered alveolar ventilation/perfusion (V′A/Q′) matching [3]. This differential diagnosis relies basically on a measurement of arterial partial pressure of carbon dioxide (PaCO 2 ).…”

Preface

“…The potential for high indices of ventilatory inefficiency (V′E-V′CO 2 or the minimum ventilatory equivalent (V′E/V′CO 2 min)) to trigger uncomfortable respiratory sensations in cardio-respiratory disease has long been recognised [26,27]. More recently, several studies have demonstrated that a high ventilatory inefficiency is an early sign of impaired gas exchange efficiency (increased "wasted" ventilation) and/or excessive afferent stimuli to ventilation (as recently reviewed in [28]) as it is related to a high respiratory neural drive and dyspnoea in symptomatic smokers [29,30] and patients with mild COPD [31,32], heart failure [8], heart failure-COPD [33,34], ILD [35] and pulmonary hypertension (PH) [36,37]. Thus, the use of different indices of the V′E-V′CO 2 relationship has proved useful in the interpretation of CPET responses in patients with unexplained or disproportionate exertional dyspnoea [38].…”