Adjunctive Inspiratory Muscle Training During a Rehabilitation Program in Patients With Breast Cancer: An Exploratory Double-Blind, Randomized, Controlled Pilot Study

Abstract

Objective: To investigate whether inspiratory muscle training (IMT) offered adjunctively to an exercise training program reduces symptoms of dyspnea in survivors of breast cancer.

Design: Double-blind, parallel-group, randomized controlled trial.

Setting: Outpatient rehabilitation program in a university hospital.

Participants: Ninety-eight female patients with breast cancer who completed adjuvant treatment and subsequently entered cancer rehabilitation were screened for participation. Inclusion criteria were reduced inspiratory muscle strength and/or symptoms of dyspnea. Twenty patients (N=20) were randomly assigned to an intervention group (n=10) or a control group (n=10).

Intervention: Both groups received a 3-month exercise training program in combination with either IMT (intervention) or sham-IMT (control).

Main outcome measures: Changes in dyspnea intensity perception (10-point Borg Scale) at comparable time points (isotime) during constant work rate cycling was the primary outcome. Secondary outcomes included changes in respiratory muscle function, exercise capacity, and changes in symptoms of dyspnea during daily life (Transitional Dyspnea Index [TDI]).

Results: The intervention group achieved a larger reduction in exertional dyspnea at isotime compared with the control group (-1.8 points; 95% CI, -3.7 to 0.13; P=.066). The intervention group also exhibited larger improvements in dyspnea during daily life (TDI score, +2.9 points; 95% CI, 0.5-5.3; P=.022) and improved both respiratory muscle endurance (+472 seconds; 95% CI, 217-728; P=.001) and cycling endurance (+428 seconds; 95% CI, 223-633; P=.001) more than the control group.

Conclusions: Because of the limited sample size all obtained findings need to be interpreted with caution. The study offers initial insights into the potential of adjunctive IMT in selected survivors of breast cancer. Larger multicenter studies should be performed to further explore the potential role and general acceptance of this intervention as a rehabilitation tool in selected patients after breast cancer treatment.

Keywords: BDI, Baseline Dyspnea Index; Breast neoplasms; Breathing exercises; Dyspnea; Exercise; IMT, inspiratory muscle training; MID, minimal important difference; Muscle strength; PImax, maximal inspiratory pressure; Physical therapy modalities; Randomized controlled trial; Rehabilitation; TDI, Transitional Dyspnea Index.

Fig 1

Consolidated Standards of Reporting Trials flow diagram displaying the progress of participants through the phases of the study.

Fig 2

Adjuvant treatments received by study participants.

Fig 3

Mean inspiratory resistance during weekly inspiratory muscle training sessions throughout the intervention period. Training resistance is expressed as percentage baseline maximal inspiratory pressure measured from residual volume. Percentage adherence to prescribed training sessions is displayed under weekly averages of training resistance. Values are mean ± SE.

Fig 4

Dyspnea intensity, sensation of leg discomfort, and VE assessed during constant work rate cycling tests. Pre- and-postactive intervention measures of (A) dyspnea intensity, (C) leg discomfort, and (E) VE. Pre- and postcontrol intervention measures of (B) dyspnea intensity, (C) leg discomfort, and (E) VE. Values are mean ± SE. Abbreviation: VE, ventilation. *Paired-samples t test: P<.05, post vs preintervention. ^†Two-way repeated measures analysis of variance: P=.01 for pre- to postassessment effect.