Bayesian fusion of algorithms for the robust estimation of respiratory rate from the photoplethysmogram

Respiratory rate (RR) is a key vital sign that is monitored to assess the health of patients. With the increase of the availability of wearable devices, it is important that RR is extracted in a robust and noninvasive manner from the photoplethysmogram (PPG) acquired from pulse oximeters and similar devices. However, existing methods of noninvasive RR estimation suffer from a lack of robustness, resulting in the fact that they are not used in clinical practice. We propose a Bayesian approach to fusing the outputs of many RR estimation algorithms to improve the overall robustness of the resulting estimates. Our method estimates the accuracy of each algorithm and jointly infers the fused RR estimate in an unsupervised manner, with aim of producing a fused estimate that is more accurate than any of the algorithms taken individually. This approach is novel in the literature, where the latter has so far concentrated on attempting to produce single algorithms for RR estimation, without resulting in systems that have penetrated into clinical practice. A publicly-available dataset, Capnobase, was used to validate the performance of our proposed model. Our proposed methodology was compared to the best-performing individual algorithm from the literature, as well as to the results of using common fusing methodologies such as averaging, median, and maximum likelihood (ML). Our proposed methodology resulted in a mean-absolute-error (MAE) of 1.98 breaths per minute (bpm), outperformed other fusing strategies (mean fusion: 2.95 bpm; median fusion: 2.33 bpm; ML: 2.30 bpm). It also outperformed the best single algorithm (2.39 bpm) and the benchmark algorithm proposed for use with Capnobase (2.22 bpm). We conclude that the proposed fusion methodology can be used to combine RR estimates from multiple sources derived from the PPG, to infer a reliable and robust estimation of the respiratory rate in an unsupervised manner.

Improvement of Microcirculation and Healing of Venous Hypertension and Ulcers With Crystacide ®: Evaluation With a Microcirculatory Model, Including Free Radicals, Laser Doppler Flux, and PO2/PCO2 Measurements

In 32 patients with chronic venous insufficiency and venous hypertension associated with ulcerations, the effects of the local application of a hydrogen peroxide cream (Crystacide) applied onto the skin was evaluated using a complex, proportional, microcirculatory model to assess and quantify venous microangiopathy after local treatment. A comparative group treated without Crystacide was included. Laser Doppler flowmetry was used to assess skin perfusion (flux and venoarteriolar response) in association with transcutaneous PO2 and PCO2 measurements. Local plasma free radicals were evaluated in the area surrounding the venous ulcer using the D-Roms test. Crystacide was applied around and on the ulcer for 10 days. Crystacide was more effective than the control treatments. PO2 was increased (improved, P < .05), and plasma free radicals, PCO2, and laser Doppler flowmetry were decreased (improving toward normal values, P < .05). Also, the ulcerated area was significantly smaller at 10 days in the Crystacide group in comparison with controls (P < .05). In the proportional microcirculatory model, all parameters indicated an important level of improvement significantly larger than in controls. In conclusion, in chronic venous insufficiency and venous ulcerations, local treatment with Crystacide (10 days) improves the microcirculation and decreases skin free radicals, thus improving healing.

Spinal Cord Stimulation in the Treatment of Peripheral Vascular Disease: Results of a Single-Center Study of 258 Patients

This report is of a retrospective study of data from 258 patients who received spinal cord stimulation (SCS) for the treatment of peripheral vascular disease as a result of arteriosclerosis. The patients’ clinical outcomes were monitored over a period of 18 months. In patients with a low baseline transcutaneous oxygen pressure (TcPO2) value of <10 mm Hg, limb survival at 18 months of follow-up (estimated by use of Kaplan-Meier survival analysis) was 77.8%, and this was even higher, at 89.5%, in patients with a medium baseline TcPO2 value of 10-30 mm Hg. This successful treatment was accompanied by a sustained increase in TcPO2 values to approximately 30 mm Hg in both of these groups. In looking at diabetic and nondiabetic patients, there is no difference in limb survival as a result of the treatment. It is concluded that SCS is an effective therapy in improving limb survival in patients with peripheral vascular disease. In addition, TcPO2 values at baseline may be a useful predictor of treatment outcome.

Quality of the assessment of primary and secondary endpoints in claudication and critical leg ischemia trials

Clinical trials in peripheral arterial disease (PAD) require an accurate definition of the disease for inclusion; they typically use treadmill testing, questionnaires and hemodynamic measures as primary and secondary endpoints. Trials of new pharmacologic therapies for PAD often employ multiple clinical sites with presumed expertise in the diagnosis and management of PAD as well as in clinical trials. However, considerable variability has been observed in the assessment of endpoints used in PAD trials, as well as a marked placebo response with treadmill testing. This variability and placebo response impact adversely on overall trial integrity, necessitate an inflated sample size, and may contribute to the large number of recently negative claudication trials. We hypothesized that site monitoring visits for evaluating testing methods would identify and characterize several critical issues that would contribute to poor testing quality. One hundred sites participating in three claudication trials for which peak walking time on the treadmill was the primary endpoint, and 16 sites participating in a critical leg ischemia study for which transcutaneous oxygen tension (TcPO2) was the primary endpoint were evaluated. Each site was visited one or more times by a clinical monitor trained in conducting a ‘site endpoint evaluation visit’ focusing on equipment, physical set-up of the room in which testing was to be conducted, and the site staff’s ability to conduct each of the specific measurements. Full reports were generated that covered a number of technical issues for each measurement and data were extracted from these reports to summarize the testing problems encountered at each site. Problems with treadmill testing were common. For example, 92% of sites had problems with their treadmill equipment, 58% did not perform proper treadmill familiarization, 24% did not start the treadmill test appropriately, 24% did not conduct the test properly, and 15% did not properly conclude the test to determine the peak walking time of the participant. Similar problems were encountered with the ankle-brachial index test, the administration of questionnaires and measurement of the TcPO2. Major deficiencies were identified at the majority of sites in the assessment of primary and secondary endpoints in PAD trials. These errors and improper testing provide a potential explanation for the wide variability and placebo responses observed in claudication and critical leg ischemia trials. Site interventions need to address these deficiencies in measurement to improve the quality of PAD trials.

Exercise transcutaneous oxygen pressure measurement has good sensitivity and specificity to detect lower extremity arterial stenosis assessed by computed tomography angiography

Peripheral artery disease (PAD) is a highly prevalent disease diagnosed by the use of ankle-brachial index (ABI) at rest. In some clinical conditions (diabetes, renal insufficiency, advanced age), ABI can be falsely normal and other tests are required for the PAD diagnosis (American Heart Association statement). This study was conducted to determine the accuracy of exercise transcutaneous oxygen pressure measurement (exercise-TcPo2) in detection of arterial stenosis ≥50% using computed tomography angiography (CTA) as the gold standard.We retrospectively analyzed consecutive patients referred to our vascular unit (University Hospital, Rennes, France) for exercise-TcPo2 testing from 2014 to 2015. All included patients had a CTA performed within 3 months of the exercise-TcPo2 test. Exercise-TcPo2 was performed on treadmill (10% slope; 2 mph speed). We calculated the Delta from Resting Oxygen Pressure (DROP) index (expressed in mm Hg) at the proximal and distal levels. Two blinded physicians performed stenosis quantification on CTA. The receiver operating characteristic (ROC) curve was used to define a cutoff point to detect arterial stenosis ≥50%, stenosis ≥60%, and stenosis ≥70%.A total of 34 patients (mean age 64 ± 2 years old; 74% men) were analyzed. The highest areas under the curve (AUC) were found for 60% stenosis at both proximal and distal levels. For stenosis ≥50%, sensitivity and specificity of proximal minimal DROP were 80.9% [67.1-89.7], 81.0% [59.3-92.7] respectively. For stenosis ≥50%, sensitivity and specificity of distal minimal DROP were 73.2% [60.3-83.1], 83.3% [53.8-96.2], respectively. For stenosis ≥60%, sensitivity and specificity of proximal minimal DROP were 82.5% [67.6-91.5] and 85.7% [67.7-94.8] respectively. For stenosis ≥60%, sensitivity and specificity of distal minimal DROP were 80.4% [67.3-89.1] and 88.2% [64.2-97.7], respectively. For stenosis ≥70%, sensitivity and specificity of proximal minimal DROP were 85.7% [67.7-94.8] and 75.0% [59.6-85.9] respectively. For stenosis ≥70%, sensitivity and specificity of distal minimal DROP were 86.0% [72.2-93.7] and 76.0% [56.1-88.7], respectively.Exercise-TcPo2 using a proximal minimal DROP value ≤-15 mm Hg or a distal minimal DROP value ≤-16 mm Hg is accurate to diagnose arterial stenosis especially stenosis ≥60% on the lower limbs. Exercise-TcPo2 is safe and noninvasive test that might be used in second line for PAD diagnosis.

Transcutaneous Oxygen and Carbon Dioxide Levels with Iloprost Administration in Diabetic Critical Limb Ischemia

Iloprost, a prostacyclin analogue, is a treatment option for surgically unsuitable diabetic chronic critical limb ischemia (CLI), although its outcome is difficult to be anticipated clinically. Whether transcutaneous (tc) oxygen tension (PO2) predicts the response to iloprost in diabetic CLI is unclear at this point and, in that same context, the prognostic role of tc carbon dioxide tension (PCO2), another ischemia-sensitive parameter, is unknown. Supine and dependent tcPO2 and tcPCO2 were measured at baseline and after 4 weeks of iloprost treatment in 31 limbs of 26 type-2 diabetic arteriopaths with CLI not amenable to surgery. Success was defined as pain relief and significant reduction of analgesics. Clinical outcome was stratified by baseline tcPO2 and tcPCO2 tertiles, and likelihood ratios (LR) quantified the increase from pretest chances given a certain result. Iloprost succeeded in 16 (52%) and failed in 15 limbs (48%) and post-treatment tcPO2 followed a parallel course. Failures increased by ascending baseline tcPCO2 and descending tcPO2 tertiles; successes behaved specularly. Predictions of failure based on elevated tcPCO2 (>53 mm Hg) were more efficient than relying on depressed tcPO2 (LR 10.7 vs 3.6); success was almost certain when tcPO2 was >23 mm Hg (LR = 17.8). Dependent determinations were less useful than supine measurements for prognostic use. Elevated tcPCO2 predicted failure efficiently and high tcPO2 was a useful prognostic tool for success of iloprost, suggesting that their combined use may allow better prognostic stratification and improve the therapeutic approach to diabetic CLI.

Cerebral microvascular blood flow and CO2 reactivity in pulmonary arterial hypertension

Hypocapnia and endothelial dysfunction might impair microvascular cerebral blood flow (CBF_micr) and cerebrovascular reactivity to CO₂ (CVR_CO2). Pulmonary arterial hypertension (PAH) is characteristically associated with chronic alveolar hyperventilation and microvascular endothelial dysfunction. We therefore determined CBF_micr (pre-frontal blood flow index (BFI) by the indocyanine green-near infrared spectroscopy methodology) during hypocapnia and hypercapnia in 25 PAH patients and 10 gender- and age-matched controls. Cerebral BFI was lower in patients than controls at similar transcutaneous PCO₂ (PtcCO₂) levels in both testing conditions. In fact, while BFI increased from hypocapnia to hypercapnia in all controls, it failed to increase in 17/25 (68%) patients. Thus, BFI increased to a lesser extent from hypo to hypercapnia ("Δ") in patients, i.e., they showed lower Δ BFI/Δ PtcCO₂ ratios than controls. In conclusion, CBF_micr and CVR_CO2 are lessened in clinically stable, mildly-impaired patients with PAH. These abnormalities might be associated with relevant clinical outcomes (hyperventilation and dyspnea, cognition, cerebrovascular disease) being potentially amenable to pharmacological treatment.

The risk factors of intraoperative anesthesia adverse events in children with laryngeal diseases

BACKGROUND

This study aimed to investigate the risk factors of intraoperative anesthesia adverse events (IAAEs) in children with laryngeal diseases.

METHODS

We retrospectively recruited 118 children with laryngeal diseases who underwent surgical therapy. Based on medical history and preoperative imaging diagnosis, the baseline data, including sex, age, weight, onset age, the number of operation, the degree of airway obstruction, the nature of disease, the location of disease, complications, tracheotomy, and trachea intubation, were defined and recorded. IAAEs, such as pulse oxygen saturation (SpO2) decline, heart rate (HR) decline, emergency orotracheal intubation, emergency tracheotomy, and remaining intubated postoperatively, were also recorded. The risk factors for IAAEs were identified using multivariate logistic regression model.

RESULTS

Increasing severity of airway obstruction and the presence of pneumonia were risk factors for SpO2 and HR decline in children with laryngeal diseases. Older age, supraglottic rather than subglottic disease, and trachea intubation rather than unprotected airway during surgery were protective factors for SpO2 decline. Furthermore, severe airway obstruction increased risks of emergency orotracheal intubation and remaining intubated postoperatively, whereas supraglottic rather than subglottic disease were protective factors for emergency orotracheal intubation and remaining intubated postoperatively. Only HR decline was found to be associated with the presence of congenital heart disease.

CONCLUSIONS

The severe airway obstruction increases the risk of SpO2 decline and HR decline as well as the possibility of perioperative emergency orotracheal intubation and remaining intubated postoperatively, whereas supraglottic surgery and surgery performed under endotracheal intubation reduce the incidence rates of these IAAEs in children with laryngeal diseases.

α-ketoglutarate is associated with delayed wound healing in diabetes

AIM

A high level of matrix metalloproteinase 9 (MMP-9) is a predictor of poor wound healing in diabetic foot ulcers. In skin keratinocytes, site-specific DNA demethylation plays an important role in MMP-9 expression. Ten-eleven translocation enzyme 2 (TET2) protein, one member of TET family, could rely on α-ketoglutarate (α-KG) as cosubstrate to exhibit catalytic activity of DNA demethylation. Here, we aimed to explore the changes of α-KG and its relationship with MMP-9 and TET2 during diabetic wound healing.

METHODS

Seventy-one cases of patients with diabetic foot ulcers and 53 cases of nondiabetic ulcers were enrolled. Serum, urine and wound fluids were collected for measurement of α-KG levels and MMP-9 expression. Skin tissues were collected for the measurement of TET2 and MMP-9 expression. Clinical parameters were collected, and transcutaneous oxygen pressure (TcPO2) levels of feet were detected.

RESULTS

The levels of α-KG, TET2 and MMP-9 were significantly increased in diabetic wound compared with nondiabetic wound (P = 0·010, 0·016 and 0·025). There was a significant correlation between a low TcPO2 and a high α-KG level of wound fluids (r = -0·395, P = 0·002). Further analysis showed that α-KG concentration had a positive correlation with both haemoglobin A1c (HbA1C) and 2 h postprandial blood glucose (PBG) (r = 0·393, P = 0·005; r = 0·320, P = 0·025, respectively).

CONCLUSIONS

The levels of α-KG, TET2 and MMP-9 were significantly increased in diabetic wound compared with nondiabetic wound. Elevated α-KG was related to local hypoxia ischaemia status and systematic poor glycaemic control.

Microvascular Changes in the Diabetic Foot

Impairment of the microcirculation of diabetic patients may contribute to secondary complications in the lower extremity, such as foot infections and ulcerations. These microcirculatory changes, which are mainly functional rather than structural, are responsible for the impaired ability of the microvasculature to vasodilate in response to injury. Dysfunction of vascular endothelial cells and vascular smooth muscle cells both contribute to the reduction in vasodilation that is observed in diabetic patients. Nerve-axon reflex related microvascular vasodilation is also impaired in the diabetic population, and there is a growing belief that both the failure of the vessels to dilate and the impairment of the nerve axon reflex are major causes for impaired wound healing in diabetic patients. Further studies are necessary to clarify the precise etiology of endothelial and smooth muscle dysfunction in diabetic patients so that potential therapeutic interventions may be identified.

Noninvasive Monitoring of Carbon Dioxide in Infants and Children With Congenital Heart Disease: End-Tidal Versus Transcutaneous Techniques

End-tidal CO2(ETCO2) monitoring and transcutaneous (TC) CO2monitoring were prospectively compared in 53 patients, 1 month to 16 years of age, with congenital heart disease (CHD). There were 32 patients with cyanotic CHD and 21 with acyanotic CHD. The TC-PaCO2difference was 2 ± 1 mm Hg and the ET-PaCO2difference was 5 ± 3 mm Hg ( P< .0001). The TC-PaCO2difference was≤2 mm Hg in 30 of 53 patients and≤5 mm Hg in 53 of 53 patients. The ETPaCO2difference was≤2 mm Hg in 9 of 53 patients and≤5 mm Hg in 30 of 53 patients ( P< .001). No variation in the TC-PaCO2difference was noted based on the type of CHD (acyanotic vs cyanotic) or age. The ET-PaCO2difference was greater in patients with cyanotic versus acyanotic CHD (7 ± 3 mm Hg vs 4 ± 2 mm Hg, P< .0001) and in patients≤1 year of age versus patients ≥1 year of age (6 ± 3 mm Hg vs 4 ± 2, P= .008). In infants and children with CHD, TC monitoring provides a more accurate estimation of PaCO2than ET monitoring.

The validity of transcutaneous oxygen measurements in predicting healing of diabetic foot ulcers

INTRODUCTION

In 2002 Fife and Strauss (Fife, et al. Wound Rep Reg, 10:198-207; Strauss, et al. Foot Ankle Intl, 23:933-937) studied the predictability of transcutaneous oxygen measurements (TCOMs) for healing diabetic foot ulcers (DFUs). This paper analyzes the validity of the two studies and combines their information to predict which DFU will heal with adjunctive hyperbaric oxygen (HBO₂) treatments.

METHODS

A statistical review of the Fife and Strauss papers was performed. The numbers presented in the papers were subjected to analyses to compare like by like data as well as test for p-values and odds ratios for predicting healing of DFUs with HBO₂.

RESULTS

In the Strauss paper 143 subjects were studied in retrospective and prospective series. In those TCOMs which exceed 200 mmHg with HBO₂ healing occurred in 87.5% even if the room air TCOM was ⟨ 30 mmHg (p ⟨ 0.001). The Fife paper studied retrospectively a subset of 221 patients who had TCOMs with HBO₂. Failure rates for healing decreased progressively from 35.7% to 14.3%, with TCOMs grouped in 100-mmHg increments from 200 mmHg to 699 mmHg. This resulted in absence of statistical significance for any 100-mmHg range over 200 mmHg with HBO₂ due to the small number of subjects for each 100-mmHg grouping.

CONCLUSIONS

Although differences exist between the study designs, each complements the other. If TCOMs exceed 200 mmHg with HBO₂, both authors observed that almost 90% of DFUs healed regardless of the room air readings when HBO₂ was used as an adjunct to management.

Transcutaneous Oximetry May Predict Wound Healing Complications In Preoperatively Radiated Soft Tissue Sarcoma

BACKGROUND

Preoperative radiation is frequently used in management of soft tissue sarcoma. We hypothesize that anoxic tissue from preoperative radiation contributes to surgical wound complications and that transcutaneous oximetry (TcO2) measurements made preoperatively can predict wounds at risk.

METHODS

Ten consecutive patients were prospectively enrolled. TcO2 was recorded at five time points. Wound complications (defined as major or minor) and healing outcomes were recorded out to 120 days postoperatively. Means between groups with and without wound complications were compared by use of a Student's t-test (p < 0.05).

RESULTS

There were three major and one minor wound complication. During the time from radiation to surgery, patients with wound complications had a 13.1 mmHg decrease in mean TcO2 while those who healed uneventfully had an increase of 2.3 mm Hg (p=0.09). Patients with complications had a low preoperative TcO2 of 18.7 mmHg compared to those without complications (18.7 vs. 33.4 mmHg; p=0.09). No patient with a TcO2 greater than 25 mmHg immediately preoperatively developed a wound complication.

CONCLUSIONS

This data suggests an earlier recovery of tissue oxygenation in patients that healed without complication. The TcO2 measurement immediately preceding surgery seems to be the most important in predicting wound complications. Larger scale investigation may determine if TcO2 measurement is a viable clinical tool to aid in risk assessment for potential wound complications.

[Our experience with the measurement of transcutaneous oxygen tension for evaluation of blood circulation in peripheral arteries in patients with critical ischemic disease of lower limbs]

INTRODUCTION

The measurement of transcutaneous oxygen pressure (TcpO2) is a non-invasive method to quantify skin oxygenation at capillary level and their nutritive ability needed to heal the ischemic defect. TcpO2 pressure values below 30 mm Hg are specific for critical limb ischemia and predict complicated healing. The purpose of this study was to verify the cut-off pressure in patient unable to undergo vascular reconstruction, and to verify the possibility of using this method to evaluate the effectiveness of vascular reconstructive surgery.

METHODS

The group included 52 patients (35 men and 17 women). The mean age of patients in the group was 66.5 years (max. 85, min. 44).

RESULTS

In our group of patients we confirmed that the TcpO2 values of successfully healed ischemic wounds were equal or greater than 30 mm Hg (mean TcpO2 value at the dorsum of the foot was 37.0 mm Hg ± 9.5 mm Hg), compared to the group of unsuccessfully healed patients whose values were lower (mean TcpO2 value at the dorsum of the foot was 9.0 mm Hg ± 5.3 mm Hg).

CONCLUSION

TcpO2 is a suitable method in predicting the healing of ischemic defects and any possible need for surgical or endovascular revascularization. Thanks to its non-invasive nature and undemanding measurement, it surely helps to make better decisions in choosing the therapeutic procedure needed to heal the defect.

Diagnostic Studies for the Evaluation of Peripheral Artery Disease

Atherosclerosis is a systemic disease that may affect multiple vascular territories including the coronary, cerebral and peripheral circulation. Peripheral arterial disease (PAD) is a common manifestation of atherosclerosis and has an important impact on quality of life as well as morbidity in affected individuals. The diagnosis of PAD can be challenging and the clinician must know the different methods available and the limitations of each of them. In this article we review noninvasive methods used in the diagnosis of PAD in detail as well as the indications for conventional invasive angiography.

Diagnosis and assessment of peripheral arterial disease in the diabetic foot

Approximately half of all patients with a diabetic foot ulcer have co-existing peripheral arterial disease. Identifying peripheral arterial disease among patients with foot ulceration is important, given its association with failure to heal, amputation, cardiovascular events and increased risk of premature mortality. Infection, oedema and neuropathy, often present with ulceration, may adversely affect the performance of diagnostic tests that are reliable in patients without diabetes. Early recognition and expert assessment of peripheral arterial disease allows measures to be taken to reduce the risk of amputation and cardiovascular events, while determining the need for revascularization to promote ulcer healing. When peripheral arterial disease is diagnosed, the extent of perfusion deficit should be measured. Patients with a severe perfusion deficit, likely to affect ulcer healing, will require further imaging to define the anatomy of disease and indicate whether a revascularization procedure is appropriate.

[Optimization of blood gas analysis in intensive care units : Reduction of preanalytical errors and improvement of workflow]

BACKGROUND

Point of care testing with blood gas analysis (BGA) is an important factor for intensive care medicine. Continuous efforts to optimize workflow, improve safety for the staff and avoid preanalytical mistakes are important and should reflect quality management standards.

AIM

In a prospective observational study it was investigated whether the implementation of a new system for BGA using labeled syringes and automated processing of the specimens leads to improvements compared to the previously used procedure.

MATERIAL AND METHODS

In a 4-week test period the time until receiving the final results of the BGA with the standard method used in the clinical routine (control group) was compared to the results in a second 4-week test period using the new labeled syringes and automated processing of the specimens (intervention group). In addition, preanalytical mistakes with both systems were checked during routine daily use. Finally, it was investigated whether a delay of 10 min between taking and analyzing the blood samples alters the results of the BGA.

RESULTS

Preanalytical errors were frequently observed in the control group where non-deaerated samples were recorded in 87.3 % but in the intervention group almost all samples (98.9 %) were correctly deaerated. Insufficient homogenization due to omission of manual pivoting was seen in 83.2 % in the control group and in 89.9 % in the intervention group; however, in the intervention group the samples were homogenized automatically during the further analytical process. Although a survey among the staff revealed a high acceptance of the new system and a subjective improvement of workflow, a measurable gain in time after conversion to the new procedure could not be seen. The mean time needed for a complete analysis process until receiving the final results was 244 s in the intervention group and 201 s in the control group. A 10-min delay between taking and analyzing the blood samples led to a significant and clinically relevant elevation of the values for partial pressure of oxygen (pO2) in both groups compared to the results when analyzing the samples immediately (118.4 vs. 148.6 mmHg in the control group and 115.3 vs. 123.7 mmHg in the intervention group). When using standard syringes the partial pressure of carbon dioxide (pCO2) was significantly lower (40.5 vs. 38.3 mmHg) whereas no alterations were seen when using the labeled syringes.

CONCLUSION

The implementation of a new BGA system with labeled syringes and automated processing of the specimens was possible without any difficulties under daily clinical routine conditions in this 10-bed intensive care unit (ICU). A gain of time could not be measured but a reduction in preanalytical errors using the labeled syringes with automated processing was found. Delayed analysis of blood samples can lead to significant changes in pO2 and pCO2 depending on the type of syringe used.

[Surgical prevention of acute stroke in atherosclerotic carotid stenosis]

The results of carotid endarterectomy performed in 687 patients for the symptomatic and asymptomatic carotid stenosis. Operation in most patients was performed under general anesthesia with intraoperative transcranial oximetry monitoring. Early good and satisfactory postoperative results in patients with symptomatic atherosclerotic carotid stenosis were 95.9% in asymptomatic and 97.2% in symptomatic patients. Hemodynamically significant restenosis over 50% of chink in 3 years follow-up was found in 3.4% patients. Eversion endarterectomy application permite to reduce the duration of the operation. Transcranial oximetry application during surgery helps to realise best surgical tactics and is helpful on decision to use or not an intraoperative shunt.

Alteration in regional tissue oxygenation of preterm infants during placement in the semi-upright seating position

We investigated whether the cerebral (rSO2-C %) and renal (rSO2-R %) tissue oxygenation of preterm infants is altered by repositioning from the supine to semi-upright position for pre-discharge car seat testing. Near-infrared spectroscopy was used to measure rSO2-C and rSO2-R, which were recorded simultaneously with vital signs in 15 preterm infants for 30 minutes in supine, 60 minutes in the semi-upright (at 45 degrees in a car seat), and 30 minutes in the post-semi-upright (supine) position. Changes in rSO2-C and SO2-R were mostly within 1 Standard Deviation (SD) of baseline mean levels in the supine position. Decrease in rSO2-C and rSO2-R (more than 1SD below baseline mean) was recorded in 26.7% and 6.6% of infants respectively, which persisted even after adjustment for variation in heart and respiratory rate, and pulse oximeter measured oxygen saturation (P, 0.0001). Re-positioning the infants from the car seat to supine position was associated with normalization of the rSO2-C. Alteration in rSO2-C and rSO2-R in a car seat was independent from the gestational and post-conception age, weight and presence of anemia. We concluded that approximately one-third of preterm infants show minor reduction of cerebral tissue oxygenation in the semi-upright (car seat) position.

[The importance of transcutaneous oxygen tension monitoring in diabetic patient with complications]

Monitoring of transcutaneous perfusion pressure of tissue oxygen (tcpO₂) is a simple, non-invasive method performed in diagnostic process of chronic diabetic complications. Primary, tcpO₂is used as an indicator of microcirculatory function. Properly placed and fixed Clark electrode is able to detect with high accuracy partial oxygen pressure on the skin surface by polarographic system of dissolved oxygen from capillary bed through tissues to upper layers of the skin. The microcirculation function is influenced by macrocirculation, thus, tcpO₂is a suitable parameter in diagnosis of peripheral arterial obliterative disease or other vascular pathologies. Combination of tcpO₂monitoring and skin perfusion pressure by laser Doppler technique gives us information not only about nutritive capillary flow, but also about vessels which precede capillary bed. The article discusses current guidelines for measurement of tcpO₂and evaluation of the results. Also reviews the results of recent studies which are interested in the use of tcpO₂in diabetic patients.

[Age, gender and individually-typological characteristics of reaction to acute hypoxic exposure]

Individual pequliarities of hypoxic resistance, assessed by the response of cardiorespiratory system to acute normobaric hypoxia (10% O2), were studied in healthy subjects. Age changes in dynamics of blood oxygen saturation after the acute hypoxia are shown at level of separate sites curve SpO2 (phases of a delay, decrease and lifting). It is established, that at children sensitivity to acute hypoxia above, than at teenagers, and at teenagers above, than at adults. Higher lability of mental processes, sympathetic activity, and personal anxiety are associated with choleric temperament. Cholerics are characterized by slower restoration of blood oxygen saturation after the acute hypoxia compared with sanguine persons that we consider an indication of less hypoxic tolerance of the first group. We have developed the complex algorithm, dynamics describing dependence oxygen saturation in various phases of the hypoxic test, which can be used as a universal method of an estimation hypoxic stability at different groups of the population.

Transcutaneous oxygen pressure (TcPO₂): a novel diagnostic tool for peripheral neuropathy in type 2 diabetes patients

AIMS

The assessment of transcutaneous oxygen pressure (TcPO2) may serve as a non-invasive and lower-cost alternative to nerve conduction studies (NCSs) for the diagnosis of diabetic peripheral neuropathy (DPN). The aim of this study was to determine whether the measurement of TcPO2 is useful for evaluating DPN.

METHODS

We performed a cross-sectional study of 381 consecutive hospitalized diabetic patients classified by clinical examination and NCS as having DPN. Anthropometric and metabolic parameters were assessed. The TcPO2 examination was performed in both supine and sitting positions.

RESULTS

Three hundred and one patients had DPN. The TcPO2 in both the supine and sitting positions was highest in the Non-DPN group and lower in the confirmed DPN group than the other three groups (p<0.001). The Non-DPN group had the lowest sitting-supine position difference in TcPO2 among the groups (p<0.001). The risk factors strongly associated with DPN included sitting-supine position difference in TcPO2 (OR=4.971, p<0.001), diabetic retinopathy (DR) (odds ratio [OR]=3.794, p=0.002), and HbA1c (OR=1.534, p=0.033). The area under the curve (AUC) of the sitting-supine position difference in TcPO2 was 0.722 and revealed an optimal cut-off point for the identification of DPN (19.5 mmHg) that had a sensitivity of 0.611 and a specificity of 0.738 based on AUC analysis.

CONCLUSIONS

This large study of diabetic patients confirms that the sitting-supine position difference in TcPO2 is higher in DPN patients than control subjects, indicating that TcPO2 examination is a promising valuable diagnostic tool for DPN.

Preprogrammed oscillations improve lower limb blood flow and walking distance in patients with peripheral arterial disease

BACKGROUND

Claudication is one of the sequelae of peripheral arterial disease (PAD). To date, no effective treatment has been found for this condition.

OBJECTIVES

To investigate a new device to treat PAD. The device administers pre-programmed protocols of oscillations to the foot.

METHODS

Fifteen patients aged 40-70 years who suffered from intermittent claudication secondary to PAD were recruited to an open prospective study. Each patient was treated once for 30 minutes. The following parameters were evaluated: pain-free and maximal walking distances, skin blood flux by laser-Doppler, skin temperature, ankle-brachial and toe-brachial indices, transcutaneous oxygen pressure (tcpO2) and transcutaneous carbon dioxide pressure (tcpCO2). Non-parametric signed-rank test was applied for testing differences between baseline assessment and post-treatment assessments for quantitative parameters.

RESULTS

Mean pain-free walking distance was 122 +/- 33 m and increased to 277 +/- 67 m, after the treatment session (P = 0.004). Mean maximal walking distance was 213 +/- 37 m and it increased to 603 +/- 77 m (P < 0.001). Foot skin perfusion also improved, as demonstrated by an increase in tcpO2 by 28.6 +/- 4.1 mmHg (P < 0.001), a decrease in tcpCO2 by 2.8 +/- 1.3 (P= 0.032), and up to twofold improvement in blood flux parameters, and an increase in skin temperature by 1.9 +/- 0.5 degrees C (P < 0.001). Ankle-brachial index increased by 0.06 +/- 0.01 (P = 0.003) and toe-brachial index by 0.17 +/- 0.02 (P < 0.001).

CONCLUSIONS

Preprogrammed oscillations applied to the foot had a positive effect on microcirculation, tissue oxygenation and CO2 clearance; they had a smaller though significant effect on arterial blood pressure indices, and the change in the arterial-brachial index correlated with the change in the pain-free walking distance.