We tested the hypothesis that inspiratory muscle loading could result in exaggerated
peripheral vasoconstriction in resting and exercising limbs and that inspiratory muscle
training (IMT) could attenuate this effect in patients with chronic heart failure
(CHF) and inspiratory muscle weakness.
Inspiratory muscle training improves functional capacity of patients with CHF, but
the mechanisms of this effect are unknown.
Eighteen patients with CHF and inspiratory muscle weakness (maximal inspiratory pressure
<70% of predicted) and 10 healthy volunteers participated in the study. Inspiratory
muscle loading was induced by the addition of inspiratory resistance of 60% of maximal
inspiratory pressure, while blood flow to the resting calf (CBF) and exercising forearm
(FBF) were measured by venous occlusion plethysmography. For the patients with CHF,
blood flow measurements as well as ultrasound determination of diaphragm thickness
were made before and after a 4-week program of IMT.
With inspiratory muscle loading, CHF patients demonstrated a more marked reduction
in resting CBF and showed an attenuated rise in exercising FBF when compared with
control subjects. After 4 weeks of IMT, CHF patients presented hypertrophy of the
diaphragm and improved resting CBF and exercise FBF with inspiratory muscle loading.
In patients with CHF and inspiratory muscle weakness, inspiratory muscle loading results
in marked reduction of blood flow to resting and exercising limbs. Inspiratory muscle
training improves limb blood flow under inspiratory loading in these patients.