Measuring Transcutaneous Oxygenation to Validate the Duration Required to Achieve Electrode Equilibration.

The objective of this study was to investigate the influence of blood transfusion and haemodilution on cerebral oxygenation and haemodynamics in relation to changes in cerebral blood flow velocity (CBFV) and other relevant physiological variables in newborn infants. Thirteen preterm infants with anaemia (haematocrit < 0.33) and ten infants with polycythaemia (haematocrit > 0.65) were studied during blood transfusion and haemodilution respectively using adult red blood cells and partial plasma exchange transfusion. Changes in cerebral concentrations of oxyhaemoglobin (cO2Hb), deoxyhaemoglobin (cHHb), total haemoglobin (ctHb), (oxidized-reduced) cytochrome aa3 (cCyt.-aa3) were continuously measured using near infrared spectrophotometry throughout the whole procedure. Simultaneously, changes of mean CBFV in the internal carotid artery were continuously measured using pulsed Doppler ultrasound. Heart rate, transcutaneous partial pressure of oxygen and carbon dioxide, and arterial O2 saturation were continuously and simultaneously measured. Blood transfusion resulted in increase of cO2Hb, cHHb, ctHb and red cell transport (product of CBFV and haematocrit), whereas CBFV decreased. The increase of cO2Hb exceeded that of cHHb, reflecting improvement of cerebral O2 supply. Haemodilution resulted in a decrease of cO2Hb, cHHb and ctHb, whereas CBFV increased. Red cell transport was unchanged. The decrease of cO2Hb exceeded that of cHHb, reflecting decreased cerebral O2 supply. cCyt.aa3 decreased after blood transfusion and remained unchanged after haemodilution, but the reliability of these results is uncertain. With the exception of a small, but significant increase in transcutaneous partial pressure of oxygen after blood transfusion, the other variables showed no changes. Each blood withdrawal during exchange transfusion resulted in only a significant increase in heart rate without changes in the other variables measured, suggesting unchanged cerebral perfusion. In newborn infants blood transfusion in anaemia results in improvement of cerebral oxygenation, but haemodilution in polycythaemia does not improve cerebral oxygenation despite possible improvement of cerebral perfusion.

To describe the use of a transcutaneous blood gas monitoring system in critically ill dogs, determine if transcutaneous and arterial blood gas values have good agreement, and verify if clinical or laboratory variables are correlated with differences between transcutaneous and arterial blood gas measurements. Prospective observational study. University teaching hospital ICU. Twenty-three client-owned dogs. In critically ill dogs undergoing arterial blood gas monitoring, a transcutaneous blood gas monitor was used to measure transcutaneous partial pressure of carbon dioxide (PtcCO2 ) and transcutaneous partial pressure of oxygen (PtcO2 ) values 30 minutes after sensor placement, which were compared to PaCO2 and PaO2 values measured simultaneously. Clinical and laboratory variables were concurrently recorded to determine if they were correlated with the difference between transcutaneous and arterial blood gas measurements. Bland-Altman analysis revealed a mean bias of 4.6 ± 26.3 mm Hg (limits of agreement [LOA]: -46.9/+56.1 mm Hg) between PtcO2 and PaO2 and a mean bias of 9.3 ± 8.5 mm Hg (LOA: -7.5/+26.0 mm Hg) between PtcCO2 and PaCO2 . The difference between PtcCO2 -PaCO2 was strongly negatively correlated with HCO3 (-) (r(2) = 0.52, P < 0.001) and PaCO2 (r(2) = 0.58, P < 0.001) and weakly positively correlated with diastolic blood pressure (r(2) = 0.21, P = 0.044), whereas the difference between PtcCO2 -PaCO2 was moderately negatively correlated with diastolic blood pressure (r(2) = 0.33, P = 0.008). Agreement between transcutaneous and arterial PO2 and PCO2 measurements in these critically ill dogs was inferior to that reported in similar adult and pediatric human studies. The transcutaneous monitor consistently over-estimated PaO2 and PaCO2 and should not be used to replace arterial blood gas measurements in critically ill dogs requiring blood gas interpretation.

The aim of this study was to investigate the effect of five chair designs on interface pressure distribution and tissue perfusion in the buttock-thigh region. Prolonged sitting has been found to contribute to the symptoms of work-related low back pain. Studies have found that chair design affects users' sitting posture and comfort. As sitting applies pressure to the user, it is necessary to investigate how chair design affects sitting pressure and tissue perfusion during sitting. We tested five chair designs (Suspension A, Suspension B, Foam A, Foam B, and bicompliant) on 15 young, healthy females. Sitting interface pressure and buttock-thigh tissue perfusion (in terms oftranscutaneous partial pressure of oxygen and carbon dioxide, tcPO2 and tcPCO2, respectively) were measured during 10-min sitting on each chair. We found that chair design significantly affected the distribution of the sitting pressure (p < .001) and buttock-thigh tissue perfusion (p < .023). Average pressure and total contact area were found highest in both foam designs, and the average pressure was the lowest in one of the suspension designs. Across all tested chair designs, the anterior portion of the seat sustained the lowest contact pressure. It was also found that tcPO2 was the lowest (p < .003) and tcPCO2 was the highest (p < .001) in tissue around ischial tuberosity for all chair designs. Chair design and materials of the seat significantly affect the sitting interface pressure distribution and tissue perfusion in sitting area. Further evaluation of these outcomes may provide useful information to correlate chair design with sitting comfort.

The responses of intracranial pressure (ICP) to hyperbaric oxygen (HBO) therapy and arterial gas pressures were investigated. ICP was measured through a ventricular or spinal drainage catheter in patients with brain tumor or cerebrovascular disease. Changes in ICP, heart rate (HR), arterial blood pressure (ABP), and transcutaneous partial pressure of carbon dioxide (PtcCO2) or oxygen (PtcO2) were recorded continuously during air or 100% O2 breathing at 1 and 2.5 atmospheres absolute (ATA). HR and PtcCO2 decreased and mean ABP was unchanged during HBO inhalation. ICP was reduced at the beginning and tended to increase gradually during HBO inhalation. The change from air to O2 without altering respiratory frequency and volume caused a gradual increase of ICP and PtcCO2 with a transient ICP reduction in an artificially respirated patient. Intentionally reduced respiration to maintain PtcCO2 at the value at 2.5 ATA with air caused the ICP to return to near the value at 2.5 ATA with air even during HBO inhalation. These findings suggest that reduced ICP is initially due to direct cerebral vasoconstriction caused by hyperoxia and is maintained mainly by induced hypocapnia during HBO inhalation. Care is required when giving HBO therapy to patients with a high ICP and/or who are respirated artificially.

Introduction: Diabetes accounts for more than 50% of lower extremity amputation, of which 85% of lower limb amputation in diabetic patients are preceded by foot ulcers. The increasing prevalence of ischaemic ulcers has made ischaemia probably the most important cause of Diabetic Foot Ulcers (DFUs) today. Modalities for assessment of vasculopathy include clinical examination of pulses, Ankle Brachial Pressure Index (ABI), Toe Brachial Pressure Index (TBI), Transcutaneous partial pressure of Oxygen (TCpO2), Duplex imaging, Magnetic Resonance (MR) and Computed Tomography Angiography (CTA). Aim: This study was aimed at evaluation of ABI and TBI in assessment of vasculopathy in DFUs and their association with the various surgical outcomes. Materials and Methods: This study was done as a cross-sectional study on 100 patients with diabetic foot, from December 2016 to April 2018, with prospective follow-up till the outcome of “ulcer healed”, “minor/major amputation” with healing of the amputation stump, was achieved. The multimodality approach for treatment of DFU was taken. Variables like age, gender, duration of present ulcer, previous history of ulcers and interventions, comorbidities, history of smoking and duration of diabetes were recorded and assessed. The examination included examination of peripheral pulses, presence of neuropathy, measurement of ABI and TBI. Investigations included HbA1c levels, swab or pus cultures from the ulcers, objective evaluation of Peripheral Arterial Disease (PAD) by Duplex Ultrasonography and CT Angiography where an intervention was contemplated. The data was entered in MS Excel spreadsheet and analysis was done using Statistical Package for Social Sciences (SPSS) version 21.0. Results: The mean age was 62.55±9.21 years, with maximum patients belonging to the age group 61-70 years (38%) followed by 51-60 years age group (33%). Smoking as a risk factor was present in 59% of all the patients. A total of 53 patients underwent amputation among which 28 were smokers (52.8%). Neuropathy was present in 47.22% (n=51), with 60.87% of all patients with neuropathy undergoing amputation which was significant (p-value=0.005). When defined by ABI alone (ABI &lt;0.9), 46.3% patients had PAD, however, using TBI &lt;0.7 for defining PAD, incidence of PAD increased to 68.31% patients. Thus identifying 21 more patients with PAD as compared to ABI. Poor glycaemic control was significantly associated with poor outcome in the form of amputation (p&lt;0.001). Patients who underwent major amputation had a mean ABI of 0.54±0.22, for minor amputation the mean ABI was 0.85±0.19 and for those who had healed ulcers, had a mean ABI of 0.61±0.27. The cut-off value for ABI to predict amputation was &gt;0.51 with a sensitivity of 77.14 and a specificity of 56.1, which was not found to be significant (p-value=0.0796). The mean TBI for the diabetic feet was 0.25±0.12 for major amputation, 0.42±0.26 for minor amputation and 0.61±0.19 for ulcer healed. With a cut-off value of ≤0.3, the sensitivity and specificity for predicting amputation were 68.75 and 88.68 respectively which was found to be significant (p&lt;0.001). Conclusion: The ABI has been found to under-report ischemia as compared to TBI in diabetic patients. TBI also correlates better with the outcome of a DFU. Thus, making TBI a part of assessment of vasculopathy in DFU patients who have not undergone toe amputations, would help in correctly identifying ischemia and early institution of possible intervention in such patients.

Transcutaneous oxygen and carbon dioxide pressure monitoring to determine severity of limb ischemia and to predict surgical outcome

The mutual effects of systolic ankle arterial pressures, positional manoeuvres, and calf artery occlusions on transcutaneous oxygen partial pressures (tcpO2) were studied in 388 legs of 258 patients with peripheral arterial occlusive disease (PAOD). The tcpO2-vs-perfusion pressure relationship could be satisfactorily fitted by a non-linear regression model deduced from the tcpO2 theory. Flow-insensitive ranges of tcpO2-vs-flow hyperbolas were reduced by both leg lowering and moving the electrode towards proximal measuring sites. Lower tcpO2 values were found in case of occluded compared to patent calf arteries at ankle arterial pressure indices below 0.4. The tcpO2 positional variability increased with worsening hemodynamic compensation and was most pronounced in critical limb ischaemia (ischaemic rest pain, non-healing ulcerations). According to a retrospective analysis, a critical ischaemia could be assumed if supine and sitting tcpO2-values exceed neither 10 nor 45 mmHg, respectively.

Ten patients with moderate to severe arterial peripheral vascular disease (PVD) were monitored during treatment with inductive pulsed electromagnetic diathermy therapy. The therapy consisted of 20 daily treatments lasting one-half hour each per day and spread over one month. The application of the electromagnetic energy to the mid-anterior thigh and plantar surface of the foot of the treated leg was accomplished by the use of two inductive application heads and resulted in tissue heating. Patient measurements included surface temperature, transcutaneous partial pressure of oxygen (tcpO/sub 2/), segmental Doppler blood pressure, and superficial blood flow measured with a laser Doppler flowmeter, in addition to the patients subjective assessments of their overall condition. Temperature measurements indicated a repeatable heating pattern for each patient. The maximum temperature was not reached within 20 minutes of heating at the maximum output, while at 10% of maximum output for 10 minutes after maximum output a temperature plateau was reached. TcpO/sub 2/ indicates that the non-treated limb was also affected by the treatment. Sixty percent (60%) of the subjects indicated their belief that the therapy had some discernible therapeutic effect on their condition. The remaining 40% of the subjects experienced no perceptible change during or after the treatment. Based upon the small sample of patients the studies suggest that there is a maximum heating rate applicable to long duration heating using this modality of diathermy. The principle effect on PVD for the subjects studied appears to have been the stimulation of vasodilation. >

Limited resources and the expense of Activated Protein C (APC) (drotrecogin alfa) may contribute to the reluctance to utilize this drug in sepsis. Employing the PROWESS criteria resulted in absolute reduction in 28-day mortality of 6.1%, representing a relative risk reduction of 19.4%. Additional patient categorization and selection may lead to less frequent drug use with the same survival advantage. We used transcutaneous partial pressure of oxygen (PtcO2) as an indicator of microcirculatory perfusion to identify which septic patients may benefit from APC. Nineteen patients consecutively admitted with severe sepsis or septic shock that fulfilled the PROWESS criteria for APC treatment. APC was administered to patients with the PROWESS selection criteria, only if the PtcO2 information demonstrated tissue ischemia. Nineteen patients met the PROWESS criteria. Ten patients demonstrated poor tissue perfusion using PtcO2 monitors and received APC. Nine patients had adequate tissue perfusion and did not receive APC. There were no differences in age, gender, APACHE II scores, lactate levels, or organ failure between the two groups. The 10 patients who received APC had a mortality of 3 of 10 (30%). The survivors of this group uniformly converted to PtcO2 values consistent with survival within 12 hours to 24 hours of drug administration. The nine patients who did not receive APC had a mortality of 2 of 9 (22%), not statistically significant from those who received the drug (p = 0.89). Withholding APC did not result in an increase in mortality from severe sepsis in those patients who demonstrated adequate PtcO2 values. The transcutaneous oxygen measurement may be a useful adjuvant in addition to the other selection criteria for better identification of patients who may benefit from APC.

Predictive value of transcutaneous oxygen pressure and amputation success by use of supine and elevation measurements

Objective To evaluate the accuracy of continuous noninvasive partial pressure of carbon dioxide monitoring in the old diabetic patients undergoing general anesthesia. Methods Sixty-six old diabetic patients of both sexes, aged 65-76 yr, weighing 49-95 kg, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, undergoing elective surgery under general anesthesia, were included in this study.Transcutaneous partial pressure of carbon dioxide(TcPCO2)was monitored by a noninvasive transcutaneous carbon dioxide monitor.Arterial blood samples were collected at 30 and 60 min after endotracheal intubation, partial pressure of arterial carbon dioxide(PaCO2)was monitored, and TcPCO2 and end-tidal pressure of carbon dioxide(PETCO2)were recorded.Bland-Altman analysis was used to measure the agreement. Results At 30 min after intubation, the results of Bland-Altman analysis showed that the mean difference between PaCO2 and TcPCO2 was 1.3, 95% confidence interval(CI)was 1.0-1.6, and the limit of agreement was -1.1-3.7; the mean difference between PaCO2 and PETCO2 was -3.2, 95%CI: -3.6--2.8, and the limit of agreement was -6.6-0.2.At 60 min after intubation, the results of Bland-Altman analysis showed that the mean difference between PaCO2 and TcPCO2 was 1.4, 95% CI was 1.1-1.7, and the limit of agreement was -1.0-3.4; the mean difference between PaCO2 and PETCO2 was -3.1, 95%CI was -3.5--2.7, and the limit of agreement was -6.7-0.5.The repeatability coefficients of PaCO2, TcPCO2 and PETCO2 were 2.1, 2.3 and 2.3, respectively, at 30 and 60 min after intubation. Conclusion Continuous noninvasive partial pressure of carbon dioxide monitoring provides good accuracy and can be used as an alternative to PaCO2 monitoring, and the accuracy is higher than that of PETCO2 for the old diabetic patients undergoing general anesthesia. Key words: Carbon dioxide; Monitoring, physiologic; Diabetes mellitus; Anesthesia, general

Background: Critical limb ischemia (CLI) is an advanced stage of peripheral arterial disease (PAD) associated with high morbidity and mortality. Functional improvement and lower amputation rates have been reported in clinical studies using intramuscular (IM) injection of autologous bone marrow mononuclear cells (ABMMNC) into ischemic limbs. Aldehyde Dehydrogenase-Bright (ALDH br ) cells are a highly potent subpopulation of ABMMNC and preclinical studies suggest that ALDH br cells may contribute more effectively to angiogenesis. Therefore, we investigated the safety and efficacy of ALDH br compared to ABMMNC in CLI patients who were not candidate for revascularization. Methods: 21 patients (mean age 72, 13 men) with ankle-brachial index (ABI) &lt; 0.5 and Rutherford category (RC) 4 – 5, were randomized to receive 10 IM injections of either ALDH br cells (n=11) or ABMMNCs (n=10) into the gastrocnemius muscle of the affected limb. Primary outcomes at 3 months were safety and efficacy based on ABI, transcutaneous partial pressure of oxygen (tcPO 2 ), RC, and ischemic ulcer grade. Paired t-test or Wilcoxon sign test was used for statistical analysis. Results: The mean number of ALDH br cells and ABMMNCs implanted were 1.33 × 10 6 and 1.207 × 10 6 . There were no significant clinical differences between the two groups at baseline. There was no adverse reaction to IM injections. One amputation occurred in each group. One death occurred in ALDH br patients, which was not related to the therapy. At 3 months in ALDH br group, ABI and RC improved 0.14 (p=0.025) and 0.64 (p=0.04), respectively. In the ABMMNC group, there were non significant changes in ABI and RC (0.08 and 0.67, respectively). No significant changes from baseline were noted in tcPO 2 and ischemic ulcer grade in either group. Conclusion: IM implantation of ALDHbr cells appears to be safe and our efficacy measures will be the first to compare selected from unselected cells in treatment of critical limb ischemia. Table: ABI, RC and tcPO2 in both groups

BACKGROUNDCarbon dioxide concentration under ophthalmic drapes increases during eye surgery under local anaesthesia. A new prototype has been designed which combines continuous suction of carbon dioxide enriched air and continuous...

Partial pressures of oxygen and carbon dioxide in bone and their correlation with bone‐blood flow: Effect of decreased arterial supply and venous congestion on intraosseous oxygen and carbon dioxide in an animal model

Research data suggests that ultrasound-assisted wound debridement (UAWD) can effectively promote the healing of diabetic foot ulcers (DFU). However, existing research is not consistent with this viewpoint. Therefore, we conducted this study to investigate the effect of UAWD on the healing of diabetic foot ulcers. From the establishment of the database to January 2024, we searched 8 databases to study the effectiveness and safety of UAWD in the treatment of DFU. Two authors independently screened the qualifications of the articles, while two authors extracted relevant data. Statistical analysis was conducted using Review Manager 5.4 and STATA 18.0 software. A total of 11 randomized controlled studies were included, with 6 countries and 696 participants participating. Our findings showed that UAWD was associated with a significant benefit in healing rate (OR = 2.60, 95% CI: [1.67, 4.03], P < 0.0001, I2 = 25%), wound healing time (MD = -11.94, 95% CI: [-23.65, -0.23], P = 0.05, I2 = 99%), percentage reduction in wound size (MD = 14.2, 95% CI: [10.8, 17.6], P = 0.47, I2 = 32%), effectiveness of treatment (OR = 10.3, 95% CI: [4.68, 22.66], P < 0.00001, I2 = 0%). Moreover, UAWD did not cause any significant adverse reactions. However, there was no obvious difference in wound blood perfusion (MD = 0.25, 95% CI: [-0.01, 0.52], P = 0.06, I2 = 90%), transcutaneous oxygen partial pressure (MD = 14.34, 95% CI: [-10.03, 38.71], P = 0.25, I2 = 98%). UAWD can significantly improve wound healing rate, shorten wound healing time, accelerate wound area reduction, and improve clinical treatment effectiveness without significant adverse reactions. Although there is no significant difference in transcutaneous oxygen pressure and wound blood flow perfusion between UAWD and SWC. So we look forward to more scientifically blinded, placebo-controlled, high-quality studies in the future, to enable researchers to obtain more complete and accurate analytical data, in order to improve the scientific and credibility of the evidence. https://www.crd.york.ac.uk/prospero/, identifier CRD42024501198.