Ventilatory response to exercise in cardiopulmonary disease: the role of chemosensitivity and dead space. Issue 2 (8th February 2018)

• Record Type: Journal Article
• Authors: Weatherald, Jason; Sattler, Caroline; Garcia, Gilles; Laveneziana, Pierantonio
• Is Part Of: European respiratory journal. Volume 51:Issue 2(2018)
• Publication Date: 2018-02-08
• Subjects: Respiratory organs -- Diseases -- Periodicals; Respiration -- Periodicals; 616.2
• DOI: 10.1183/13993003.00860-2017
• Languages: English
• ISSNs: 0903-1936

Abstract

The lungs and heart are irrevocably linked in their oxygen (O2 ) and carbon dioxide (CO2 ) transport functions. Functional impairment of the lungs often affects heart function and vice versa . The steepness with which ventilation ( V ′E ) rises with respect to CO2 production ( V ′CO2 ) ( i.e. the V ′E / V ′CO2 slope) is a measure of ventilatory efficiency and can be used to identify an abnormal ventilatory response to exercise. The V ′E / V ′CO2 slope is a prognostic marker in several chronic cardiopulmonary diseases independent of other exercise-related variables such as peak O2 uptake ( V ′O2 ). The V ′E / V ′CO2 slope is determined by two factors: 1) the arterial CO2 partial pressure ( P aCO2 ) during exercise and 2) the fraction of the tidal volume ( V T ) that goes to dead space ( V D ) ( i.e. the physiological dead space ratio ( V D / V T )). An altered P aCO2 set-point and chemosensitivity are present in many cardiopulmonary diseases, which influence V ′E / V ′CO2 by affecting P aCO2 . Increased ventilation–perfusion heterogeneity, causing inefficient gas exchange, also contributes to the abnormal V ′E / V ′CO2 observed in cardiopulmonary diseases by increasing V D / V T . During cardiopulmonary exercise testing, the P aCO2 during exercise is often not measured and V D / V T is only estimated by taking into account the end-tidal CO2 partial pressure ( P ETCO2 ); however, P aCO2 is not accurately estimated from P ETCO2 in patients with cardiopulmonary disease. Measuring arterial gases ( P aO2 and P aCO2 ) before and during exercise provides information on the real (and not "estimated") V D / V T coupled with a true measure of gas exchange efficiency such as the difference between alveolar and arterial O2 partial pressure and the difference between arterial and end-tidal CO2 partial pressure during exercise. The "appropriate" V ′ E exercise response depends on V ′ CO2, arterial P CO2, V D / V T and respiratory mechanics http://ow.ly/M1IZ30gGNIw