Transcutaneous application of the gaseous CO2 for improvement of the microvascular function in patients with diabetic foot ulcers.

INTRODUCTION: Microvascular function is impaired in patients with diabetes mellitus (DM) and is involved in numerous DM complications. Several microvascular-supporting interventions have been proposed of which the transcutaneous application of gaseous CO2 (hereinafter CO2 therapy) is one of the most promising. The aim of present study was to determine the effect of repeated CO2 therapies on the cutaneous microvascular function in DM patients with diabetic foot ulcers. METHODOLOGY: A total of 42 subjects with at least one chronic diabetic foot ulcer were enrolled in the study. They were divided into the experimental group (21 subjects aged 64.6 ±â€¯11.6 years) that underwent 4-week-long treatment with transcutaneous application of gaseous CO2 (hereinafter CO2 therapies), and the placebo group (21 subjects aged 65.0 ±â€¯10.7 years) that underwent 4-week-long placebo treatment with transcutaneous application of air. Before the first and after the last treatment in both groups, laser Doppler (LD) flux in foot cutaneous microcirculation, heart rate, and arterial blood pressure measurements were carried out during rest and local thermal hyperaemia (LTH) provocation test. RESULTS: In the experimental group the following statistically significant changes were observed after the completed treatment 1) increased mean relative powers of LD flux signals during rest in the frequency bands related to NO-independent endothelial (0.07 ±â€¯0.055 vs. 0.048 ±â€¯0.059, p = 0.0058), NO-mediated endothelial (0.154 ±â€¯0.101 vs. 0.113 ±â€¯0.108, p = 0.015), and neurogenic (0.17 ±â€¯0.107 vs. 0.136 ±â€¯0.098, p = 0.018) activity; 2) decreased resting LD flux (35 ±â€¯29 PU vs. 52 ±â€¯56 PU; p = 0.038); and 3) increased peak LD flux as a function of baseline during LTH (482 ±â€¯474%BL vs. 287 ±â€¯262%BL, p = 0.036); there were no statistically significant changes observed in the placebo group. No systemic effects were observed in none of the two groups by means of mean values of heart rate and arterial blood pressure. CONCLUSIONS: Repeated CO2 therapies improves the microvasular function in DM patients without any systemic side effects.

The effect of transcutaneous application of gaseous CO2 on diabetic chronic wound healing-A double-blind randomized clinical trial.

Chronic wounds in diabetics are difficult to treat, therefore, adjuvant therapies have been investigated. Bathing in CO2 -rich water (spa therapy) has been known in Europe for decades for its positive effect on peripheral vascular disorders. Recently, much effort has been invested in developing optimal application methods of CO2 . Uses include subcutaneous injections of CO2 , bathing in CO2 -enriched water, and transcutaneous application of CO2 . To verify the effect of transcutaneous application of gaseous CO2 on the healing of chronic diabetic wounds, a randomized double-blind clinical research was designed. The research included 30 and 27 wounds in the study and control groups, respectively. In addition to standard treatment, patients in the study group received 20 therapies with medical-grade CO2 gas and the control group received the same treatment with air. Results showed significantly faster healing in the study group: 20 of the 30 wounds in the study group were healed compared with none in the control group. Mean wound surface and volume in the study group was reduced significantly (surface: 96%, P = .001, volume: 99%, P = .003) compared with a small reduction in the control group (surface: 25%, P = .383, volume: 27%, P = .178). Considering our results, transcutaneous application of gaseous CO2 is an effective adjuvant therapy in diabetic chronic wound treatment.

Feasibility of assessing ultra-short-term pulse rate variability from video recordings.

OBJECTIVES: Remote photoplethysmography (rPPG) is a promising non-contact measurement technique for assessing numerous physiological parameters: pulse rate, pulse rate variability (PRV), respiratory rate, pulse wave velocity, blood saturation, blood pressure, etc. To justify its use in ultra-short-term (UST) PRV analysis, which is of great benefit for several healthcare applications, the agreement between rPPG- and PPG-derived UST-PRV metrics was studied. APPROACH: Three time-domain metrics-standard deviation of normal-to-normal (NN) intervals (SDNN), root mean square of successive NN interval differences (RMSSD), and the percentage of adjacent NN intervals that differ from each other by more than 50 ms (pNN50)-were extracted from 56 video recordings in a publicly available data set. The selected metrics were calculated on the basis of three groups of 10 s recordings and their average, two groups of 30 s recordings and their average, and a group of 60 s recordings taken from the full-length recordings and then compared with metrics derived from the corresponding reference (PPG) pulse waveform signals by using correlation and effect size parameters, and Bland-Altman plots. MAIN RESULTS: The results show there is stronger agreement as the recording length increases for SDNN and RMSSD, yet there is no significant change for pNN50. The agreement parameters reach r = 0.841 (p < 0.001), r = 0.529 (p < 0.001), and r = 0.657 (p < 0.001), estimated median bias -1.52, -2.28 ms and -1.95% and a small effect size for SDNN, RMSSD, and pNN50 derived from the 60 s recordings, respectively. SIGNIFICANCE: Remote photoplethysmography-derived UST-PRV metrics manage to capture UST-PRV metrics derived from reference (PPG) recordings well. This feature is highly desirable in numerous applications for the assessment of one's health and well-being. In future research, the validity of rPPG-derived UST-PRV metrics compared to the gold standard electrocardiography recordings is to be assessed.

A wavelet-based decomposition method for a robust extraction of pulse rate from video recordings.

BACKGROUND: Remote photoplethysmography (rPPG) is a promising optical method for non-contact assessment of pulse rate (PR) from video recordings. In order to implement the method in real-time applications, it is necessary for the rPPG algorithms to be capable of eliminating as many distortions from the pulse signal as possible. METHODS: In order to increase the degrees-of-freedom of the distortion elimination, the dimensionality of the RGB video signals is increased by the wavelet transform decomposition using the generalized Morse wavelet. The proposed Continuous-Wavelet-Transform-based Sub-Band rPPG method (SB-CWT) is evaluated on the 101 publicly available RGB facial video recordings and corresponding reference blood volume pulse (BVP) signals taken from the MMSE-HR database. The performance of the SB-CWT is compared with the performance of the state-of-the-art Sub-band rPPG (SB). RESULTS: Median signal-to-noise ratio (SNR) for the proposed SB-CWT ranges from 6.63 to 10.39 dB and for the SB from 4.23 to 6.24 dB. The agreement between the estimated PRs from rPPG pulse signals and the reference signals in terms of the coefficients of determination ranges from 0.81 to 0.91 for SB-CWT and from 0.41 to 0.47 for SB. All the correlation coefficients are statistically significant (p < 0.001). The Bland-Altman plots show that mean difference range from 5.37 to 1.82 BPM for SB-CWT and from 22.18 to 18.80 BPM for SB. DISCUSSION: The results show that the proposed SB-CWT outperforms SB in terms of SNR and the agreement between the estimated PRs from RGB video signals and PRs from the reference BVP signals.

Effect of transcutaneous application of gaseous carbon dioxide on cutaneous microcirculation.

BACKGROUND: The inefficient healing of chronic wounds is a result of poor blood perfusion at the wound and surrounding tissues. Artificially applied carbon dioxide (CO2) has the potential to improve the perfusion and oxygenation of tissues, hence is useful for the healing of chronic wounds. OBJECTIVE: The aim of the present study was to determine the effect of a transcutaneous application of physiological vasodilator gaseous CO2 on cutaneous blood flow. METHODS: Laser Doppler (LD) flux in cutaneous microcirculation, skin temperature, electrocardiogram and arterial blood pressure were measured simultaneously in a group of 33 healthy men, aged 21-28 years, during rest and a 35-minute CO2 therapy. One lower limb of each subject represented the studied extremity, being exposed to gaseous CO2. The contralateral limb was the control, being exposed to air. Each limb was sealed in a plastic bag. RESULTS: During CO2 therapy the LD flux in the studied extremity increased from 5.8 PU ± 3.9 PU to 30.3 PU ± 16.7 PU (mean ± standard deviation; paired t-test, p <  0.001), while that in the control extremity did not change significantly. CONCLUSIONS: Our results confirm a local vasodilatory effect of applied CO2 therapy. This finding indicates its potential clinical use.