Skin vasomotor reflexes during inspiratory gasp: standardization by spirometric control does not improve reproducibility.

Arteriovenous anastomoses (AVA) in skin microcirculation are mediated by the sympathetic stimuli. The inspiratory gasp test (IG test) triggers the sympathetic nervous system, resulting in a decrease in AVA skin blood flow, as measured by laser Doppler fluxmetry (LDF). We studied the reproducibility of the IG test under carefully standardized respiratory conditions. In each of 19 healthy (young) volunteers with a mean skin temperature during the experiment above 28 degrees C 13 IG tests were performed, either under spirometric control or uncontrolled and by using a negative pressure transducer. Starting the IG test end-inspiratory results in the most pronounced absolute LDF decrease [140 PU (70-490)], median (minimum-maximum) as compared to starting end-expiratory [100 PU (40-260)] and during inspiration [110 PU (50-350)], respectively, p < 0.001 and p < 0.001. Inspiration as fast as possible results in a larger absolute LDF decrease [150 PU (40-450)], compared to inspiration in 5 s [120 PU (60-340); p < 0.02] and in 10 s [130 PU (40-350); p < 0.05]. Continuously sucking negative mouth pressure results in a larger LDF decrease [140 PU (30-420)] in comparison with taking one deep breath and holding it for 10 s [110 PU (30-270); p < 0.01]. However, standardization of the IG test did not improve its reproducibility.