Effects of single and bilateral limb immersion on systemic and cerebral hemodynamic responses to the cold pressor test.

ABSTRACT

The cold pressor test (CPT) involves cold water immersion of either the upper or lower limb(s) and elicits autonomic and hemodynamic increases via stimulation of pain and cutaneous thermoreceptors. It is unclear whether the choice of limb(s) in CPT studies differentially affects systemic and cerebral hemodynamic responses. Herein, we assessed systemic and cerebral hemodynamic and ventilatory responses to different CPT protocols of the hand (CPTH), foot (CPTF), or bilateral feet (CPTBF). We hypothesized CPTBF would elicit greatest physiological responses due to increased exposure area to the cold stimulus. Methods. Twenty-eight (14M;14F) healthy young adults [23.4 (SD 2.4) years] participated in three 3-minute CPT protocols during a single visit. Mean arterial pressure (MAP), heart rate (HR), middle cerebral artery blood velocity (MCAv) and cerebrovascular conductance index, and end-tidal carbon dioxide (PETCO2), and pain perception were recorded throughout CPT protocols. Results. There was a time-CPT protocol interaction on systolic (p=0.02) and diastolic blood pressure (p<0.01), MAP (p<0.01), HR (p<0.001), presented as mean(SD). MCAv and cerebrovascular conductance index did not change with CPTs. Peak delta HR from baseline occurred in CPTBF (Δ13.6(15.5)BPM) compared to CPTH (Δ4.85(12.6)BPM; p=0.01) and CPTF (Δ4.04(13.3)BPM; p=0.02). Delta MAP was greater in CPTH (Δ12.3(7.95)mmHg) and CPTBF (Δ12.9(9.24)mmHg) compared to CPTF (Δ8.42(7.12)mmHg; p<0.01). Perceived pain was higher in CPTBF compared to single limb protocols (p≤0.01). Conclusion. Our findings suggest choice of limb(s) in CPT protocols affects systemic hemodynamic responses and should be considered when designing CPT studies.