Continuous reduction in cerebral oxygenation during endurance exercise in patients with pulmonary arterial hypertension

Abstract

Background Patients with pulmonary arterial hypertension (PAH) have lower cerebral blood flow (CBF) and oxygenation compared to healthy sedentary subjects, the latter negatively correlating with exercise capacity during incremental cycling exercise. We hypothesized that patients would also exhibit altered CBF and oxygenation during endurance exercise, which would correlate with endurance time. Methods Resting and exercise cardiorespiratory parameters, blood velocity in the middle cerebral artery (MCAv; transcranial doppler) and cerebral oxygenation (relative changes in cerebral tissue oxygenation index (ΔcTOI) and cerebral deoxyhemoglobin (ΔcHHb); near‐infrared spectroscopy) were continuously monitored in nine PAH patients and 10 healthy‐matched controls throughout endurance exercise. Cardiac output (CO), systemic blood pressure (BP) and oxygen saturation (SpO2), ventilatory metrics and end‐tidal CO2 pressure (PETCO2) were also assessed noninvasively. Results Despite a lower workload and endurance oxygen consumption, similar CO and systemic BP, ΔcTOI was lower in PAH patients compared to controls (p < .01 for interaction). As expected during exercise, patients were characterized by an altered MCAv response to exercise, a lower PETCO2 and SpO2, as wells as a higher minute‐ventilation/CO2 production ratio (trueV˙normalE/V˙CO2 ratio). An uncoupling between changes in MCAv and PETCO2 during the cycling endurance exercise was also progressively apparent in PAH patients, but absent in healthy controls. Both cHHb and ΔcTOI correlated with trueV˙normalE/V˙CO2 ratio (r = 0.50 and r = −0.52; both p < .05 respectively), but not with endurance time. Conclusion PAH patients present an abnormal cerebrovascular profile during endurance exercise with a lower cerebral oxygenation that correlate with hyperventilation but not endurance exercise time. These findings complement the physiological characterization of the cerebral vascular responses to exercise in PAH patients.

Exertional Desaturation in Idiopathic Pulmonary Fibrosis: The Role of Oxygen Supplementation in Modifying Cerebral-Skeletal Muscle Oxygenation and Systemic Hemodynamics

“…Based on the aforementioned, the purpose of this cross-over, placebo controlled, clinical trial was to investigate in a group of IPF patients, without resting hypoxemia, the acute effects of oxygen administration (fraction of inspired oxygen, FiO 2 0.40) during steady-state submaximal exercise (as compared to the delivery of medical air [sham oxygen, FiO 2 0.21]) on cerebral and skeletal muscle oxygenation and systemic hemodynamic profile and whether the above improvements coexist with enhancements in exercise duration, perception of leg fatigue, and severity of dyspnea. Considering data in patients with other pulmonary disease showing that the reduction in cerebral oxygenation is also a contributing factor to impaired exercise performance [20,23,24], we tested the hypothesis that oxygen supplementation during exercise improves cerebral oxygenation (increases cerebral-O 2 Hb and prevents the rise in HHb) and prolongs cycling duration in patients with IPF exertion-induced hypoxemia.…”

Exercise intolerance in pulmonary arterial hypertension: insight into central and peripheral pathophysiological mechanisms

“…Recently, we [5] and others [105,106] demonstrated that patients with PAH also have lower CBF and impaired regulatory mechanisms, altering the buffering of blood pressure changes and potentially explaining why patients with PAH are more prone to syncope after Valsalva-induced decreases in blood pressure [107]. At exercise, cerebral oxygenation was also markedly impaired during incremental [5,106] and endurance exercise [108], tightly correlating with the exercise capacity of patients with PAH [5]. Interestingly, oxygen supplementation significantly enhanced cerebral oxygenation, maximal workload and endurance time during exercise, attesting of its probable relevance for exercise tolerance in patients with PAH [109].…”

Early Detection and Correction of Cerebral Desaturation With Noninvasive Oxy-Hemoglobin, Deoxy-Hemoglobin, and Total Hemoglobin in Cardiac Surgery: A Case Series

“…The ΔHHbi represents the relative change in deoxygenated hemoglobin. ΔHHbi increases during hypoxia, 27 increased cerebral metabolic rate‚ and venous congestion. 20 The ΔcHbi is the only parameter that is not measured directly but calculated.…”

“…[22][23][24][25] Other instruments such as the NIRO 300 and Oxiplex TS have also been used to provide similar information, but their clinical use in cardiac surgery has not been detailed extensively. 22,[26][27][28] We hereby present the first case series in the literature describing our preliminary experience in adults using hemoglobin chromophores with complementary information from other noninvasive monitoring devices. The goal of this case series is to introduce readers to this new modality and present easily identifiable patterns that may further characterize the mechanisms of cerebral desaturation.…”

“…22–25 Other instruments such as the NIRO 300 and Oxiplex TS have also been used to provide similar information, but their clinical use in cardiac surgery has not been detailed extensively. 22,26–28…”