Cardiac Reserve and Pulmonary Gas Exchange Kinetics in Patients With Stroke

Abstract

Background and Purpose-Cardiovascular and pulmonary factors contributing to impaired peak oxygen uptake (V O 2 ) in patients with stroke (SP) are not well known. We assessed cardiovascular function, pulmonary gas exchange, and ventilation in SP and healthy age, gender, and activity-matched control subjects. Methods-Ten hemiparetic SP and 10 control subjects were enrolled. Subjects completed cycle ergometry testing to assess peak and reserve V O 2 , carbon dioxide production, ventilation (tidal volume; breathing frequency; minute ventilation), and cardiac output. V O 2 , carbon dioxide production, and minute ventilation were measured throughout peak exercise recovery (off-kinetics) and at exercise onset (on-kinetics) along with heart rate during low-level exercise. Results-Peak V O 2 was 43% lower (PϽ0.001) in SP secondary to reduced peak and reserve cardiac output and minute ventilation. The impaired cardiac output reserve (PϽ0.001) was due to a 34% lower heart rate reserve (Pϭ0.001). The impaired minute ventilation reserve (Pϭ0.013) was due to a 41% lower tidal volume reserve (Pϭ0.009). Stroke volume and breathing frequency reserve were preserved. V O 2 off-kinetics were 29% slower in SP (PϽ0.001) and related to peak V O 2 (RϭϪ0.72, PϽ0.001) and peak cardiac output (RϭϪ0.75, PϽ0.001) for the study group. Additionally, carbon dioxide production (Pϭ0.016) and minute ventilation (Pϭ0.023) off-kinetics were prolonged in SP. V O 2 on-kinetics were 29% slower (Pϭ0.031) during low-level exercise in SP. Conclusions-The impaired peak V O 2 in SP is secondary to a decline in peak and reserve cardiac output and ventilation.Prolonged

Discrepancy Between Cardiac and Physical Functional Reserves in Stroke

“…4,8 The underlying physiological limitations of this finding have not been well defined, restricting the ability to target therapies. Some explanations include bedrest-induced deconditioning, concomitant left ventricular dysfunction, the associated severity of neurological involvement, and the increased aerobic requirements of walking.…”

“…10 Only 1 previous study has assessed Q T during exercise in people with stroke. 4 The authors argued that reduced peak VO 2 is secondary to a decline in peak and reserve Q T , 4 which was assessed in only 4 patients and therefore needs to be considered with caution. The present study, however, suggests that peak cardiac function is not diminished, whereas maximal arterial-venous oxygen difference is reduced by 26% in stroke participants.…”

“…2,3 To date, limited information is available on measures of cardiac function and performance during exercise in stroke survivors. 4 Cardiac power output, a direct and integrative measure of overall cardiac function (ie, cardiac pumping capability) that incorporates both pressure and flow domains of the cardiovascular system, 5 has not been reported in stroke survivors yet. The aims of this study were to define (1) whether maximal aerobic capacity is limited by the cardiovascular system to supply oxygen or by the capacity of the skeletal muscles to use oxygen in these individuals; and (2) cardiac pumping capability in individuals after stroke.…”

Impaired cardiorespiratory fitness after aneurysmal subarachnoid hemorrhage

“…Patients and controls performed identical CPET measurements, which allowed better interpretation of CPET outcome. Including a comparison group is a commonly used method when studying cardiorespiratory responses in patients, including patients after stroke (39,40).…”

Respiratory Changes in Patients with Stroke

“…According to Teixeira -Salmela et al (2005) (8) , changes in lung ventilation may occur after stroke due to reduction of the contribution of the abdominal compartment during the respiratory cycle. The Tomczak et al study (2008) (26) demonstrated that, after stroke, those individuals presented reduced electromyographic activity of the paretic diaphragm muscle and lower values of forced vital capacity (FVC), 1 st second forced expiratory volume (FEV1) and tidal volume (Vt) when compared to predictive values. Almeida et al (2011) (16) evaluated the effects of hemiplegia on pulmonary function in 20 patients with chronic stroke compared to 14 healthy subjects.…”