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Clinical Investigations: CARDIOLOGY |

Ventilatory Constraints During Exercise in Patients With Chronic Heart Failure*

Bruce D. Johnson, PhD; Kenneth C. Beck, PhD; Lyle J. Olson, MD; Kathy A. O’Malley; Thomas G. Allison, PhD; Ray W. Squires, PhD; Gerald T. Gau, MD, FCCP
Author and Funding Information

*From the Divisions of Cardiovascular (Drs. Johnson, Olson, Allison, Squires, and Gau) and Thoracic Diseases (Dr. Beck and Ms. O’Malley), Department of Internal Medicine, Mayo Clinic and Foundation, Rochester, MN. The study was supported by the Mayo Foundation and Human Health Services grant MO1-RR00585, General Clinical Research Centers, Division of Research Resources, National Institutes of Health.

Correspondence to: Bruce D. Johnson, PhD, Division of Cardiovascular Diseases, Baldwin 2B, Mayo Clinic, Rochester, MN 55905; e-mail: johnson.bruce@mayo.edu



Chest. 2000;117(2):321-332. doi:10.1378/chest.117.2.321
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We examined the degree of ventilatory constraint in patients with a history of chronic heart failure (CHF; n = 11; mean ± SE age, 62 ± 4 years; cardiac index [CI], 2.0 ± 0.1; and ejection fraction [EF], 24 ± 2%) and in control subjects (CTLS; n = 8; age, 61 ± 5 years; CI, 2.6 ± 0.3) by plotting the tidal flow-volume responses to graded exercise in relationship to the maximal flow-volume envelope (MFVL). Inspiratory capacity (IC) maneuvers were performed to follow changes in end-expiratory lung volume (EELV) during exercise, and the degree of expiratory flow limitation was assessed as the percent of the tidal volume (Vt) that met or exceeded the expiratory boundary of the MFVL. CHF patients had significantly (p < 0.05) reduced baseline pulmonary function (FVC, 76 ± 4%; FEV1, 78 ± 4% predicted) relative to CTLS (FVC, 99 ± 4%; FEV1, 102 ± 4% predicted). At peak exercise, oxygen consumption (V̇o2) and minute ventilation (V̇e) were lower in CHF patients than in CTLS (V̇o2, 17 ± 2 vs 32 ± 2 mL/kg/min; V̇e, 56 ± 4 vs 82 ± 6 L/min, respectively), whereas V̇e/carbon dioxide output was higher (42 ± 4 vs 29 ± 5). In CTLS, EELV initially decreased with light exercise, but increased as V̇e and expiratory flow limitation increased. In contrast, the EELV in patients with CHF remained near residual volume (RV) throughout exercise, despite increasing flow limitation. At peak exercise, IC averaged 91 ± 3% and 79 ± 4% (p < 0.05) of the FVC in CHF patients and CTLS, respectively, and flow limitation was present over > 45% of the Vt in CHF patients vs < 25% in CTLS (despite the higher V̇e in CTLS). The least fit and most symptomatic CHF patients demonstrated the lowest EELV, the greatest degree of flow limitation, and a limited response to increased inspired carbon dioxide during exercise, all consistent with V̇e constraint. We conclude that patients with CHF commonly breathe near RV during exertion and experience expiratory flow limitation. This results in V̇e constraint and may contribute to exertional intolerance.

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