Chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) patients show a marked reduction in exercise capacity compared to that of healthy age-matched individuals. While inadequate gas exchange and resulting hypoxemia appears as the primary factor in COPD, an impaired cardiac output is the predominant explanation for the reduced oxygen delivery in CHF. However, the extent of the contributions of other systemic factors remains unclear. In light of the potential interactions between cardiac output (Qc) and pulmonary hyperinflation, there is surprisingly little data thus far on ventilatory constraints in CHF and on the role of blood flow delivery in COPD which may further limit the exercise capacity. Thus, the purpose of this study was to compare the slope of the Qc versus oxygen uptake (VO2) response through several submaximal cycling loads in patients with moderately severe COPD and with that of moderate to severe CHF patients as well as age-matched healthy control subjects (CTRL). Also examined was the possibility that ventilatory constraints such as dynamic hyperinflation contribute to an abnormal stroke volume response in both diseases. Cardiac output was measured using the CO 2-rebreathing equilibrium technique during baseline conditions and cycling at 20, 40 and 65% of peak power in 17 COPD (Age: 64 +/- 8 yrs; FEV 1/FVC: 37 +/- 11%; FEV1: 41 +/- 15 % predicted), 10 CHF (Age: 57+/- 10 yrs; FEV1/FVC: 73.8 +/- 5.6%; FEV 1: 93 +/- 13% predicted) and 10 age-matched CTRL subjects. Inspiratory capacity (IC) was also measured for the determination of dynamic hyperinflation during the steady state exercise bouts. The results indicate that while the absolute Qc values are lower in COPD and in CHF than in CTRL during 65% peak power cycling (11.30 +/- 2.38 vs 12.40 +/- 2.08 vs 15.63 +/- 2.15 L•min-1 respectively, p < 0.01), likely due to their lower exercise metabolic demand. The Qc/VO2 response to increasing levels of exercise intensity was lower or normal in CHF patients compared to CTRL, while normal or hyperdynamic in most COPD patients. Indeed, the majority of patients with COPD exhibited Qc/VO2 slopes greater than 7.0, which may be indicative of a peripheral muscle bioenergetic disturbance that may drive the need for greater oxygen delivery, and thus result in an exaggerated central circulatory response.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.97901 |
| Date | January 2006 |
| Creators | Baril, Jacinthe. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Kinesiology and Physical Education.) |
| Rights | © Jacinthe Baril, 2006 |
| Relation | alephsysno: 002481236, proquestno: AAIMR24611, Theses scanned by UMI/ProQuest. |
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