Title: Evaluation of Sex-Based Differences of Diaphragm Fatigue using Electrical Phrenic Nerve Stimulation
Supervisors: Dr. William Sheel
Committee members: Dr. Tania Lam, Dr. Jean-Sébastien Blouin
Abstract:
The diaphragm is a skeletal muscle found within the chest cavity primarily responsible for inspiration. Under conditions of physical activity, diaphragmatic contraction increases to match ventilation to metabolic demands. Like other skeletal muscles, increased contraction of the diaphragm can lead to fatigue, evidenced by a reduction in the diaphragms force producing ability, measured as transdiaphragmatic pressure (Pdi). Previous research has demonstrated that sex-based differences in diaphragm fatigue exist, such that females demonstrate greater resistance to fatigue compared to males. The underlying physiological mechanisms responsible for sex-based differences in diaphragm fatigue remain unknown. Peripheral mechanisms responsible for fatigue can be evaluated based on the stimulation frequency used to evoke Pdi using electrical bilateral phrenic nerve stimulation (BPNS). Fatigue can then be classified as high frequency fatigue, or low frequency fatigue.
Twenty-two participants (n=11 females, n=11 males) will be recruited and undergo pressure threshold loading (PTL) until task failure. Pre- and post PTL, BPNS will be administered at 5 Hz, 10 Hz, 20 Hz, 50 Hz, and 100 Hz while recording evoked Pdi. Balloon tipped catheters will be placed in the esophagus and the stomach to measure esophageal pressure (Pes) and gastric pressure (Pga), respectively. Pdi is found by subtracting Pga from Pes.
It is hypothesized that following PTL, when compared to males, females will: (1) show less high frequency diaphragm fatigue; and (2) females will recover from high frequency fatigue at an accelerated rate compared to low frequency fatigue.
This research aims to address a critical gap in the literature by exploring sex-based differences in diaphragm fatigue. The findings have the potential to impact sex-specific therapeutic interventions and training protocols aimed at improving respiratory muscle endurance and overall respiratory healthy.