A Pilot Study of Inspiratory Muscle Training to Improve Exercise Capacity in Patients with Fontan Physiology.

Wu FM; Opotowsky AR; Denhoff ER; Gongwer R; Gurvitz MZ; Landzberg MJ;
Shafer KM; Valente AM; Uluer AZ; Rhodes J.

Seminars in Thoracic & Cardiovascular Surgery. 30(4):462-469, 2018 Winter.
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Comment in: Semin Thorac Cardiovasc Surg. 2018 Winter;30(4):470-471; PMID:

While the Fontan procedure has improved life expectancy, patients with
single ventricle physiology have impaired exercise capacity due to limited
increase in pulmonary blood flow during activity. Enhancing the “thoracic
pump” using inspiratory muscle training (IMT) may ameliorate this
impairment. Adult nonsmokers with Fontan physiology were recruited through
Boston Children’s Hospital’s outpatient clinic. Participants underwent
cardiopulmonary exercise testing and pulmonary function testing, followed
by 12 weeks of IMT and then repeat testing. The primary endpoint was
change in % predicted peak oxygen consumption (VO2). Secondary endpoints
were changes in other exercise metrics. Eleven patients (6 male) were
enrolled. Median ages at time of enrollment and Fontan completion were
28.8 years (25.7, 45.5) and 7.8 years (3.9, 16.5), respectively. Average
baseline maximal inspiratory pressure (MIP) was normal; only 2 patients
had MIP <70% predicted. Peak work rate improved significantly from
baseline after 12 weeks of IMT (116.5 +/- 45.0 to 126.8 +/- 47.0 W,
P=0.019). Peak VO2 tended to improve (baseline 68.1 +/- 14.3, change + 5.3
+/- 9.6% predicted, P=0.12), as did VE/VCO2 slope (34.1 +/- 6.7 to 31.4
+/- 3.6, P=0.12). There was no change in peak tidal volume or MIP. In a
small cohort of Fontan patients with mostly normal MIP, IMT was associated
with significant improvement in peak work rate and a trend toward higher
peak VO2 and improved ventilatory efficiency. Larger studies are needed to
determine if this reflects true lack of effect or whether this pilot study
was underpowered for effect size, and whether IMT is more narrowly useful
for patients with impaired MIP.