Exploring relationships between inspiratory muscle strength and functional capacity in childhood cancer survivors: a pilot study.

Childhood cancer survivors (CCS) experience short- and long-term side effects from cancer treatment that often impair functional capacity. Inspiratory muscle weakness is a potential mechanism for reduced functional capacity. The objective of this pilot study was to examine the relationship between inspiratory muscle strength and functional capacity in 10 CCS. Inspiratory muscle strength was measured by maximal inspiratory pressure (MIP) while functional capacity was measured by the two-minute walk test (2MWT), the physiological cost index and hemodynamic response to exercise according to changes in heart rate, blood pressure and rate-pressure product (RPP). Overall, MIP and 2MWT distance were below predicted values. Hemodynamic responses to the 2MWT were consistent with little variation, except for elevated diastolic blood pressure (DBP) response. MIP had significant relationships with resting DBP (Spearman's rank correlation coefficient [rs] = -0.70; p = 0.03) and DBP response (rs = 0.72; p = 0.02). Time since completion of cancer treatment had a significant positive relationship with RPP response (rs = 0.67; p = 0.03). Inspiratory muscle weakness in childhood cancer could be an indicator of skeletal muscle dysfunction and should be considered when symptoms of dyspnea or poor functional capacity arise. Inspiratory muscle strength was found to be related to changes in blood pressure in CCS. Future studies should further investigate these relationships and the impact of inspiratory muscle training on hemodynamics and functional capacity in CCS.