Analysis of respiratory muscle strength and its relationship with functional capacity between different field tests in patients with heart failure

ABSTRACT

Objective

To analyze respiratory muscle strength of patients with heart failure (HF) and correlate with functional capacity.

Methods

This cross-sectional study involved patients with compensated HF of both sexes, aged above 18 years. Respiratory muscle strength was assessed by measuring maximum inspiratory (MIP) and expiratory pressures (MEP) using a manovacuometer. Patients were randomized into two groups to assess functional capacity: six-minute walk test (6MWT) and incremental shuttle walk test (ISWT).

Results

Forty-eight patients were evaluated (23 from 6MWT and 25 from ISWT group). Most were male (67.8%), with mean age of 62.3 years and left ventricular ejection fraction of 40.8%. Mean predicted values of MIP [81.2% (74.7–87.8%)] and MEP [95.6% (88.2–103.0%)] did not indicate respiratory muscle weakness. The higher the New York Heart Association (NYHA) functional class, the lower the MIP (p = .011) and MEP (p = .016) values. Physically active patients presented higher respiratory muscle strength than those sedentary (MIP: 104.5 vs. 71.9 cmH₂O, p < .001; MEP: 120.0 vs. 91.1 cmH₂O, p = .004). Functional capacity was impaired [6MWT: 416.0 m (372.8–459.3 m); ISWT: 304 m (263.4–344.9 m)], and distance covered in the ISWT was shorter than 6MWT group (p < .001). Distance covered in the ISWT group presented a moderate positive correlation with MIP (r = 0.45; p = .022) and MEP (r = 0.41; p = .041).

Conclusion

Most patients with HF presented respiratory muscle strength close to predicted values; however, sedentary patients and those with high NYHA functional class, showed reduced MIP and MEP. Functional capacity was reduced, and MIP and MEP correlated with distance covered in the ISWT.

KEYWORDS:

• Heart failure
• maximum respiratory pressure
• physical fitness
• respiratory muscles

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.