Effect of Cyclooxygenase Inhibition on the Inspiratory Muscle Metaboreflex-Induced Cardiovascular Consequences in Men

Inspiratory muscle metaboreflex activation increases mean arterial pressure (MAP) and limb vascular resistance (LVR) and decreases limb blood flow (Q_L). Cyclooxygenase (COX) inhibition has been found to attenuate limb skeletal muscle metaboreflex-induced increases in muscle sympathetic nerve activity. We hypothesized that compared to placebo (PLA), COX inhibition would attenuate inspiratory muscle metaboreflex-induced 1) increases in MAP and LVR and 2) decreases in Q_L. Seven men (22±1 years) were recruited and orally consumed ibuprofen (IB, 10mg/kg) or PLA 90 min prior to performing the cold pressor test (CPT) for 2 min and inspiratory resistive breathing task (IRBT) for 14.9±2.0min at 65% of maximal inspiratory pressure. Breathing frequency was 20 breaths per min with a 50% duty cycle during the IRBTs. MAP was measured via automated oscillometry, Q_L was determined via Doppler ultrasound, and LVR was calculated as MAP divided by Q_L. EMG was recorded on the leg to ensure no muscle contraction occurred. The 65% IRBT led to greater increases (p=0.02) in 6-keto-PGF_1α with PLA compared to IB. IB, compared to PLA, led to greater (p<0.01) increases in MAP (IB: 17±7mmHg vs. PLA: 8±5mmHg) and LVR (IB: 69±28% vs. PLA: 52±22%) at the final min of the 65% IRBT. The decrease in Q_L was not different (p=0.72) between IB (-28±11%) and PLA (-27±9%) at the final min. The increase in MAP during the CPT was not different (p=0.87) between IB (25±11mmHg) and PLA (24±6mmHg). Contrary to our hypotheses, COX inhibition led to greater inspiratory muscle metaboreflex-induced increases in MAP and LVR.

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