These results suggest that: (1) similar epidermal protection may be attained with SCS and MCS for Deltat(total)

Many commercially available dermatologic lasers utilize cryogen spray cooling for epidermal protection. A previous tissue culture study demonstrated that single cryogen spurts (SCS) of 80 ms or less were unlikely to cause cryo-injury in light-skinned individuals. More recently, multiple cryogen spurts (MCS) have been incorporated into commercial devices, but the effects of MCS have not been evaluated. The aim was to study an in vitro tissue culture model and the epidermal and dermal effects of SCS vs patterns of shorter MCS with the same preset total cryogen delivery time (Deltat(c)) and provide an explanation for noted differences. Four different spurt patterns were evaluated: SCS: one 40-ms cryogen spurt; MCS2: two 20-ms cryogen spurts; MCS4: four 10-ms cryogen spurts; MCS8: eight 5-ms cryogen spurts. Actual Deltat(c) and total cooling time (Deltat(Total)) were measured for each spurt pattern. RAFT tissue culture specimens were exposed to cryogen spurt patterns and biopsies were taken immediately and at days 3 and 7. Actual Deltat(c) was increased while Deltat(Total) remained relatively constant as the preset Deltat(c) of 40 ms was delivered as shorter MCS. Progressively more epidermal damage was noted with exposure to the MCS patterns. No dermal injury was noted with either SCS or MCS. For a constant preset Deltat(c) of 40 ms, delivering cryogen in patterns of shorter MCS increased the actual Deltat(c) and consequently the observed epidermal cryo-injury as compared to an SCS.

Cryogen spray cooling (CSC) is used to minimize the risk of epidermal damage during various laser dermatologic surgeries. However, as the application of single or multiple cryogen spurts becomes available on some commercial lasers devices, it is necessary to determine the optimal CSC parameters for different laser surgeries. The objective of this study was to measure the time the sprayed surface of a human skin phantom (HSP) remains below water freezing temperature 0°C, referred to as subzero time (t s ), and below the cryogen boiling temperature -26°C, referred to as residence time (t r ), as well as the minimum surface temperature (T min ) and the time at which T min occurs (t Tmin ) for two HSP-initial temperatures (20 °C and 70 °C) during and after the application of single (SCS) and multiple cryogen spurts (MCS). For this propose, a HSP was used to measure t s , t r , T min , and t Tmin for nine sequences: one SCS of ∆t T = TCT = 40 ms; four MCS sequences, all adding to a ∆t T of 40 ms but with different TCT up to 110 ms and, finally; four SCS that matched the TCT of the four MCS sequences, but lead to different ∆t T . Our results show that the differences between SCS and MCS sequences with the same TCT are negligible for all variables measured (t s , t r , T min , t Tmin ). Moreover, in this interval (40 ms≤ TCT ≤ 110 ms), this variables show a remarkable linear dependence with the TCT. Keywords: dynamic cooling, cooling selectivity, cryo-injury, port wine stain. INTRODUCTIONCSC is particularly necessary for treatment of superficial vascular lesions, since it permits [1]: (1) accurate control of the cryogen application time (typically 5-100 milliseconds) and, consequently, cooling time and; (2) high heat transfer rates as cryogen is deposited onto the skin and evaporates at the sprayed surface. These two characteristics are instrumental to achieve efficient and spatially selective epidermal cooling.Despite these advantages, some authors have expressed concerns that CSC may induce cryo-injury [2]. With this in mind, different studies of CSC have been developed employing computational models [3], epoxy phantoms [4], and more recently an In-Vitro Skin Model (RAFT) [5] to study the effect of short cryogens spurts on HSP.In this work, we investigate systematically the thermal response of skin phantoms by measuring the time (t Tmin ) and magnitude at which the minimum surface temperature (T min ) is reached, as well as the time the sprayed surface remains below 0 °C (subzero time, t s ) and -26 °C (residence time, t r ), and examine the differences between SCS and MCS sequences.

Objective To describe and compare characteristics of older adults who drive after drinking and those who do not, whether an intervention addressing at-risk drinking reduces risk among those reporting driving after drinking, and reasons reported for driving after drinking. Methods Secondary data analysis of a randomized trial testing the efficacy of a multifaceted intervention to reduce at-risk drinking among adults with a mean age of 68 years in primary care (N=631). Results Almost a quarter of at-risk drinkers reported driving after drinking (N=154). Compared to those who did not drive after drinking, those who did were more likely to be younger, male and working. They consumed a higher average number of drinks per week, had more reasons they were considered at-risk drinkers, and were more likely to meet at-risk drinking criteria due to amount of drinking and binge drinking. Those driving after drinking at baseline reduced the frequency of this behavior at 3- and 12-months and there were no statistically significant differences in the proportions of persons still engaging in driving after drinking among those who were assigned to intervention or control groups. Reasons for driving after drinking included not thinking it was a problem and having to get home. Conclusions Driving after drinking is common in this population of older, at-risk drinkers recruited in primary care settings, and, like younger adults, men and those reporting binge drinking are more likely to engage in this behavior. Given this behavior is dangerous and the population of older adults is fast growing, interventions addressing driving after drinking are needed.