Safety of different types of loaded breathing in adult Fontan patients

Abstract

<b>Introduction:</b> Fontan patients have a passive pulmonary circulation and limited exercise capacity, possibly related to weak respiratory muscles. They may thus benefit from respiratory muscle training (RMT). To which degree RMT poses a circulatory risk has not been tested. <b>Methods:</b> 16 adult Fontan patients (9m:7f; 29±8y) underwent lung function, respiratory muscle strength and incremental cardiopulmonary exercise testing (CPET). On a different day, three different types of RMT procedures were performed for up to 10min in randomized order: 1) normocapnic hyperpnea (HYP); 2) respiratory muscle sprint interval "training" (RMSIT); and 3) resistive breathing at 30% and 60% of maximal inspiratory (PI30, PI60) and expiratory pressure (PE30, PE60) with duty cycle 0.7. Heart rate (HR), peripheral oxygen saturation (SpO₂), systolic blood pressure (SBP), as well as stroke volume (SV) and cardiac output (CO) were recorded continuously. An electrocardiogram was monitored for adverse events. <b>Results:</b> No adverse events occurred. SV decreased compared to rest during PE30 only (p&lt;0.05). HR increased during HYP, RMSIT, PE30, and PE60 (all p&lt;0.05) but did not reach maximum CPET levels. CO was stable in all RMT, except for a rise during HYP (p&lt;0.05). SBP was elevated in all RMT (all p&lt;0.001) but did not reach maximum CPET levels. SpO₂ decreased during PE60 only (p&lt;0.01). <b>Conclusion:</b> Short RMT activities are safe in asymptomatic adult Fontan patients. Physiological responses depend on type of RMT and do not reach maximum CPET levels. First trainings should be monitored specifically when applying high positive intrathoracic pressures.