Background: Negative pressure wound therapy (NPWT) is an intensely investigated topic, but its mechanism of action accounts for one of the least understood ones in the area of wound healing. Apart from a misleading nomenclature, by far the most used diagnostic tool to investigate NPWT, the laser Doppler, also has its weaknesses regarding the detection of changes in blood flow and velocity. The aim of the present study is to explain laser Doppler readings within the context of NPWT influence. Methods: The cutaneous microcirculation beneath an NPWT system of 10 healthy volunteers was assessed using two different laser Dopplers (O2C/Rad-97®). This was combined with an in vitro experiment simulating the compressing and displacing forces of NPWT on the arterial and venous system. Results: Using the O2C, a baseline value of 194 and 70 arbitrary units was measured for the flow and relative hemoglobin, respectively. There was an increase in flow to 230 arbitrary units (p = 0.09) when the NPWT device was switched on. No change was seen in the relative hemoglobin (p = 0.77). With the Rad-97®, a baseline of 92.91% and 0.17% was measured for the saturation and perfusion index, respectively. No significant change in saturation was noted during the NPWT treatment phase, but the perfusion index increased to 0.32% (p = 0.04). Applying NPWT compared to the arteriovenous-vessel model resulted in a 28 mm and 10 mm increase in the venous and arterial water column, respectively. Conclusions: We suspect the vacuum-mediated positive pressure of the NPWT results in a differential displacement of the venous and arterial blood column, with stronger displacement of the venous side. This ratio may explain the increased perfusion index of the laser Doppler. Our in vitro setup supports this finding as compressive forces on the bottom of two water columns within a manometer with different resistances results in unequal displacement.

OBJECTIVE: We aimed to explore the link between local vasodilation and pain perception in elderly subjects, testing the hypothesis that altered local cutaneous blood flow participates in the decrease in pain tolerance with age.
METHODS: Sixty-eight young and 83 older participants performed a pain tolerance test in which they hold their hand in an airtight box in which air temperature was regulated at 65 °C until the pain became unbearable. Participants continuously estimated pain intensity. Skin temperature and local blood flow in the box-exposed hand were continuously monitored.
RESULTS: In the young group, 97% of subjects resisted pain until the end of the test, whereas only 53% in the elderly group managed to do so, indicating that pain tolerance is impaired in the elderly. Among all participants, the skin temperature associated with the first pain sensation was below the threshold for nociceptor activation (43 °C). Interestingly, blood flow in the elderly group was correlated with pain judgment, whereas no such correlation was observed in the young.
CONCLUSIONS: Our results suggest that the local vasodilator response induced by local heating may be involved in pain perception and may influence thermal pain tolerance with aging. These results could contribute to a better understanding of vascular deficits and the development of chronic pain in vascular pathologies.

OBJECTIVE: To evaluate whether in juvenile localized scleroderma (JLS), non-invasive imaging can differentiate affected from non-affected skin and whether imaging correlates with a validated skin score [Localised Scleroderma Cutaneous Assessment Tool (LoSCAT)].
METHODS: A total of 25 children with JLS were recruited into a prospective study and a single \'target\' lesion was selected. High-frequency ultrasound (HFUS, measuring skin thickness), infrared thermography (IRT, skin temperature), laser Doppler imaging (LDI, skin blood flow) and multispectral imaging (MSI, oxygenation) were performed at four sites: two of affected skin (centre and inner edge of lesion) and two of non-affected skin (1 cm from the edge of the lesion \'outer\' and contralateral non-affected side) at four visits at 3 month intervals.
RESULTS: Differences between affected and non-affected skin were detected with all four techniques. Compared with non-affected skin, affected skin was thinner (P < 0.001), with higher temperature (P < 0.001-0.006), perfusion (P < 0.001-0.039) and oxygenation (P < 0.001-0.028). Lesion skin activity (LoSCAT) was positively correlated with centre HFUS [r = 0.32 (95% CI 0.02, 0.61), P = 0.036] and negatively correlated with centre LDI [r = -0.26 (95% CI -0.49, -0.04), P = 0.022]. Lesion skin damage was positively correlated with centre and inner IRT [r = 0.43 (95% CI 0.19, 0.67), P < 0.001 and r = 0.36 (95% CI 0.12, 0.59), P = 0.003, respectively] and with centre and inner LDI [r = 0.37 (95% CI 0.05, 0.69), P = 0.024 and r = 0.41 (95% CI 0.08, 0.74), P = 0.015, respectively].
CONCLUSIONS: Non-invasive imaging can detect differences between affected and non-affected skin in JLS and may help to differentiate between activity (thicker, less well-perfused skin) and damage (thinner, highly perfused skin).

A laser doppler flowmetry (LDF) test can reflect the pulp vitality caused by the change in pulp blood flow (PBF). This study aimed to investigate the PBF of the permanent maxillary incisors using LDF and to calculate the clinical reference range and coincidence rate for pulp vitality using PBF as an indicator.
School-age children (7-12 years) were recruited randomly. A total of 455 children (216 female and 239 male) were included in this study. An additional 395 children (7-12 years) who attended the department due to anterior tooth trauma from October 2015 to February 2018 were included to assess the clinical occurrence rate. The PBF was measured using LDF equipment and an LDF probe.
The clinical reference range of PBF values for the permanent maxillary incisors (teeth 11, 12, 21, and 22) in children were from 7 to 14 perfusion units (PU), 11 (6.016; 11.900 PU), 12 (6.677; 14.129 PU), 21 (6.043;11.899 PU), and 22 (6.668; 14.174 PU). There was a statistically significant correlation between PBF and children\'s age (p < 0.000) without any significant gender discrimination (p = 0.395). For all incisors, for any age group, the PBF detection value of the lateral incisors was significantly higher than that of the central incisors (p < 0.05). The clinical coincidence rate of detecting PBF in the traumatic teeth was 90.42% and the sensitivity and specificity were 36.99% and 99.88%, respectively.
The determination of the PBF clinical reference range and clinical coincidence rate for the permanent maxillary incisors in children using LDF provided a promising theoretical basis for clinical applications.

The aim of the present study was to evaluate the effect of platelet-rich plasma injection on the survival of experimentally developed subdermal plexus skin flaps in cats. Two flaps, 2 cm wide and 6 cm long were created bilaterally in the dorsal midline in 8 cats. Each flap was randomized to 1 of 2 groups: platelet-rich plasma injection and control. After flap development, the flaps were immediately placed back on the recipient bed. Then 1.8 mL of platelet-rich plasma was equally injected into 6 different parts of the treatment flap. All flaps were evaluated macroscopically daily and on days 0, 7, 14, and 25 by planimetry, Laser Doppler flowmetry, and histology. Mean flap survival on day 14 was 80.437 % (±22.745) for the treatment group and 66.516 % (±24,12) for the control group with no statistically significant difference between the 2 groups (P = .158). Histologically, a significant difference was found between the base of the PRP and the control flap in edema score on day 25 (P = .034). In conclusion, there is no evidence to support the use of platelet-rich plasma in subdermal plexus flaps in cats. However, the use of platelet-rich plasma may aid in reducing edema of subdermal plexus flaps.

Microcirculation is a critical factor in burn wound healing. Remote ischemic conditioning (RIC) has been shown to improve microcirculation in healthy skin and demonstrated ischemic protective effects on heart, kidney, and liver cells. Therefore, we examined microcirculatory effects of RIC in partial thickness burn wounds. The hypothesis of this study is that RIC improves cutaneous microcirculation in partial thickness burn wounds. Twenty patients with partial thickness burn wounds within 48 hours after trauma were included in this study. RIC was performed with an upper arm blood pressure cuff on a healthy upper arm using three ischemia cycles (5 min inflation to 200 mm Hg) followed by 10-minute reperfusion phases. The third and final reperfusion phase lasted 20 minutes. Microcirculation of the remote (lower/upper extremities or torso) burn wound was continuously quantified, using a combined Laser Doppler and white light spectrometry. The capillary blood flow in the burn wounds increased by a maximum of 9.6% after RIC (percentage change from baseline; P < .01). Relative hemoglobin was increased by a maximum of 2.8% (vs. baseline; P < .01), while cutaneous tissue oxygen saturation remained constant (P > .05). RIC improves microcirculation in partial thickness burn wounds by improving blood flow and elevating relative hemoglobin.

Delayed graft function (DGF) after renal transplantation is a relevant clinical problem affecting long-term organ function. The early detection of patients at risk is crucial for postoperative monitoring and treatment algorithms. In this prospective cohort study, allograft perfusion was evaluated intraoperatively in 26 kidney recipients by visual and formal perfusion assessment, duplex sonography, and quantitative microperfusion assessment using O2C spectrometry and ICG fluorescence angiography. The O2C tissue spectrometry device provides a quantitative method of microperfusion assessment that can be employed during kidney transplantation as an easy-to-use and highly sensitive alternative to ICG fluorescence angiography. Intraoperative microvascular flow and velocity in the allograft cortex after reperfusion predicted DGF with a sensitivity of 100% and a specificity of 82%. Threshold values of 57 A.U. for microvascular flow and 13 A.U. for microvascular velocity were identified by an ROC analysis. This study, therefore, confirmed that impairment of microperfusion of the allograft cortex directly after reperfusion was a key indicator for the occurrence of DGF after kidney transplantation. Our results support the combined use of intraoperative duplex sonography, for macrovascular quality control, and quantitative microperfusion assessment, such as O2C spectrometry, for individual risk stratification to guide subsequent postoperative management.

Cutaneous microcirculatory perfusion is commonly measured using laser Doppler flowmetry (LDF) probes, which provide a continuous, non-invasive quantification of skin blood flow (SkBF). However, inhomogeneities in the skin\'s microvasculature density contribute to a decrease in reproducibility whenever an LDF probe is removed and replaced, as is the case during pre- and post-intervention or between-day measurements. Therefore, this study aimed to determine whether increasing the total number of individual LDF probes in a localized area improves the reproducibility of the measurement. Seven laser Doppler probes were secured in a custom-made acrylic holder designed to attach to the skin\'s surface easily. SkBF, local skin temperature (Tsk), and blood pressure (BP) were assessed in 11 participants (6 M, 5 F, 42 ± 15 years). SkBF and Tsk were measured from the dorsal forearm (arm trial) for 5 min. Next, the multi-laser device was moved to the lateral side of the calf (leg trial), and measurements were obtained for 5 min. Each arm and leg trial was cyclically repeated three times, and all trials were separated by intermissions lasting 10-15 min. The average SkBF and the cutaneous vascular conductance (CVC) from all possible LDF probe combinations were not statistically different across the three arm and leg trials. Two-way mixed-effects models with absolute agreement were used to compute the intraclass correlation coefficient (ICC) for CVC, and the minimum ICC increased with the addition of LDF probes. The ICC of the average CVC from seven LDF probes was 0.96 between the arm trials and 0.91 between the leg trials, which suggests that there is excellent reliability and little difference between trials following the removal and replacement of the device. Moreover, all individual ICC values from ≥3 LDF probe combinations were greater than 0.70 (i.e., good reliability). These data suggest that SkBF measurements with multiple laser Doppler probes in a custom-made holder have excellent reproducibility after replacing the probes within the same participant. Therefore, this application could provide more reproducible assessments between repeated measurements (e.g., before and after exercise or clinical procedures) where the LDF probes must be removed and replaced within the same location.

An ideal local anesthetic would be effective, minimally reduce pulpal blood flow (PBF), and not require injection. This study compared the effects of 3% tetracaine plus 0.05% oxymetazoline nasal spray (Kovanaze; KNS) and injections using 2% lidocaine with 1:100,000 epinephrine (LE) or 3% mepivacaine plain (MP) on PBF, anesthetic efficacy, and participant preference.
In a double-blind cross-over design, 20 subjects randomly received a test anesthetic and placebo at each of 3 visits (KNS/mock infiltration; mock nasal spray/LE; or mock nasal spray/MP). Nasal sprays and infiltration apical to a maxillary central incisor were delivered ipsilaterally. PBF was evaluated by laser Doppler flowmetry, and local anesthetic success was assessed with electric pulp testing. Postoperative pain levels, participant preference, and adverse events were also assessed.
LE injections demonstrated significant reductions in PBF at all time intervals compared with baseline (P < .05), whereas KNS and MP did not. Pulpal anesthesia success rates were higher for LE (85%) compared with MP (35%) and KNS (5%). Participants reported significantly higher postoperative pain levels for KNS compared with LE and MP. Additionally, KNS was the least preferred of the anesthetics administered and resulted in more reported adverse events.
Although KNS showed no significant effect on PBF, it was not effective in achieving pulpal anesthesia as used in this study.

Laser Doppler was used to measure toe blood pressure (TBP) in 40 consecutive patients with various degree of peripheral arterial disease. The aim of this methodological study was to increase the usefulness of TBP by exploring the interchangeability between TBP from the first and second toe and by investigating daily routine reproducibility and measurement variability. According to our study design pressure values were based on three measurements that were averaged. At simultaneous measurements, TBP of the first toe was 71 mm Hg (standard deviation [SD] 25) compared with 70 mm Hg (SD 25) on the second toe. The correlation ( r ) between first and second toe pressure measurements was 0.84 and intraclass correlation coefficient (ICC) was 0.84. The difference between TBP on the first and second toe was not related to gender, diabetes, or magnitude of the pressures. Repeated TBP measurements of the right first toe after disconnection of cuffs, 5 to 10 minutes rest, and reconnection of cuffs had a coefficient of variation (CV) of 9% and an ICC of 0.93. CV for toe-brachial index (TBI) was 8%. Our results show that measurements of TBP from the second toe to a large extent are interchangeable with those assessed from the first toe and can be used in clinical situations where measurements from the first toe are not feasible. Flow detection with three averaged laser Doppler measurements generates TBP and TBI with low variability.