Eff ects of single and bilateral limb immersion on systemic and cerebral hemodynamic responses to the cold pressor test
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abstract
The cold pressor test (CPT) involves cold water immersion of either upper or lower limb(s), and elicits increases in sympathetic nervous activity, heart rate (HR), and mean arterial pressure (MAP) via stimulation of pain receptors. Due to differential pain sensitivity between upper and lower
limbs and the effects of limb exposure area, it is unclear
how choice of CPT protocol may differentially affect systemic and cerebral hemodynamic responses. Our objective was to assess systemic and cerebral hemodynamic, and ventilatory responses to different CPT protocols (hand (CPTH), foot (CPTF), bilateral feet (CPTBF)). Twenty-three (14M;9F) healthy young adults (23.6±2.5 years) participated in three 3-min CPT protocols during a single visit. HR, MAP, middle cerebral artery blood velocity (MCAv) and cerebrovascular conductance index (MCACVCi), and end-tidal carbon dioxide (PETCO2) were averaged over the final 30s of each minute of each CPT protocol. We hypothesized CPTBF would elicit greatest physiological responses due to increased exposure area. Statistical analyses were performed using two-way repeated measures ANOVAs (time-protocol interaction). We found significant effects of the time-protocol interaction on HR (p = 0.01) and MAP (p = 0.009). Significant main effects of CPT protocol on HR (CPTHHRpeak 79±19BPM, CPTFHRpeak 80±15BPM, CPTBFHRpeak 90±21BPM; p < 0.001), and MAP (CPTHMAPpeak100±9mmHg, CPTFMAPpeak 98±9mmHg, CPTBFMAPpeak 102±12mmHg; p = 0.04) were identified. We also observed significant main effects of time (change from baseline; p < 0.05) for HR, MAP, MCACVCi, PETCO2. Our findings suggest systemic hemodynamics are variable across CPT protocols, with greatest physiological responses occurring in CPTBF. We conclude choice of limb(s) in CPT protocols may lead to differential hemodynamic responses and should be considered when designing future CPT studies.
