RESUMO
Objective To quantify the temporal changes in the volume of blood flow to the skin of the forearm and lower leg during static maximum inspiratory breath-holding of different durations.Methods Blood flow to the skin of the forearm and lower leg were continuously measured with laser Doppler flowmetry in 12 healthy subjects.They were randomly selected to hold their breath for 10,20 or 40 seconds,or as long as possible.The volume of skin blood flow,the onset latency and the recovery latency were measured before,during and after the breath holding.Results Blood flow decreased significantly during each breath-hold with any durations.The magnitude of the decrease and its latencies were similar with all the durations.The average volume of skin blood flow and it's minimum value during each breath-hold were significantly lower in the forearms than in the lower legs.However,the average onset latency (4.41 ±0.44 s) and the average recovery latency (5.95 ±0.59 s) in the forearms were significantly shorter than in the lower legs (4.83 ± 0.70 s for onset and 7.33 ± 0.91 s for recovery).Conclusion The volume of skin blood flow decreases during a static maximum inspiratory breath-hold,and the magnitude of the increase is not related to the duration of the breath-hold.The generalized increase in skin sympathetic vasoconstrictor activity during a static breath-hold is greater in the forearm than in the lower leg.