Evaluation of the use of an integration-type laser-Doppler flowmeter with a temperature-loading instrument for measuring skin blood flow in elderly subjects during cooling load: comparison with younger subjects.

An integration-type laser-Doppler flowmeter, equipped with a temperature-load instrument, for measuring skin blood flow (ILD-T), and analytical parameters developed in a previous study were used to compare changes in the skin blood flow in the forehead and cheek in elderly subjects (in their 60s and 70s) with those in younger subjects (in their teens to 50s). Age-related differences in skin blood flow in the forehead and cheek in response to cooling were evaluated in 90 healthy women in their teens to 70s (mean age: 17.2 +/- 0.33 years for teenagers; 24.3 +/- 0.76 years for those aged 20-29 years; 34.8 +/- 1.12 years for those aged 30-39 years; 43.3 +/- 0.78 years for those aged 40-49 years; 53.8 +/- 1.13 years for those aged 50-59 years; 63.5 +/- 0.55 years for those aged 60-69 years; 72.2 +/- 0.70 years for those aged 70-79 years). The measurement was performed continuously for 5 min: for 1 min at a sensor temperature of 30 degrees C, for 2 min after the setting of the sensor temperature had been changed to 10 degrees C, and for 2 min after the temperature setting had been cancelled. The parameters analyzed were (1) skin temperature in a resting state before measurement ( T(rest)), (2) mean skin blood flow in 1 min at a sensor temperature of 30 degrees C ( F(30 degrees C)), (3) minimum skin blood flow at a sensor temperature of 10 degrees C ( F(min)), (4) slope of the blood flow plot during the period from the beginning of cooling at 10 degrees C to F(min) ( S(fall)), (5) time required for the sensor temperature to reach 10 degrees C (Delta t(s)), (6) maximum skin blood flow during the period from the end of cooling to the end of measurement ( F(max)), (7) slope of the blood flow plot during the period from F(min) to F(max) ( S(rise)), (8) rate of decrease of the skin blood flow during cooling: FDR = ( F(min)/ F(30 degrees C))x100, (9) recovery rate of the skin blood flow after the end of cooling: FRR = ( F(max)/ F(30 degrees C))x100. When correlations among the above nine parameters were evaluated by combining all age groups, significant correlations ( P < 0.01) were observed between F(30 degrees C) and F(min), F(30 degrees C) and F(max), F(30 degrees C) and S(fall), F(min) and F(max), and F(max) and S(rise) in the forehead. In the cheek, significant correlations ( P < 0.01) were observed in all these combinations except between F(max) and S(rise). When these analytical parameters were compared among the age groups, F(30 degrees C), T(rest), F(max), and S(rise) decreased significantly ( P < 0.02 for F(30 degrees C) and T(rest), P < 0.01 for F(max) and S(rise)) and S(fall) increased significantly ( P < 0.03) in the forehead with aging. However, no significant change with aging was observed in FDR, Delta t(s), F(min), and FRR. In the cheek, FDR increased significantly ( P < 0.03), and S(rise) decreased significantly ( P < 0.01) with aging. However, no significant change with aging was observed in F(30 degrees C), T(rest), F(max), S(fall), Delta t(s), F(min), and FRR. Thus, the decrease in the skin blood flow during cooling showed no marked quantitative change with age, but, with aging, the rate of this decrease was clearly reduced in the forehead. In the cheek, on the other hand, the skin blood flow decreased markedly with aging, but no clear change was observed in the rate of this decrease. By using ILD-T and examining various parameters obtained, the skin hemodynamics in the forehead and cheek during cooling from 30 degrees C to 10 degrees C could be analyzed, and differences in the hemodynamics between the forehead and cheek and between elderly and younger individuals were clarified. This instrument is expected to be clinically useful.