Skin PO2 Research Articles

Dynamic oxygen assessment techniques enable determination of anesthesia's impact on tissue.

Tissue oxygenation is well understood to impact radiosensitivity, with reports demonstrating a significant effect of breathing condition and anesthesia type on tissue oxygenation levels and radiobiological response. However, the temporal kinetics of intracellular and extracellular oxygenation have never been quantified, on the timescale that may affect radiotherapy studies. C57BL/6 mice were anesthetized using isoflurane at various percentages or ketamine/xylazine (ket/xyl: 100/10 mg/kg) (N = 48). Skin pO2 was measured using Oxyphor PdG4 and tracked after anesthetization began. Oxyphor data was validated with relative measurements of intracellular oxygen via protoporphyrin IX (PpIX) delayed fluorescence (DF) imaging. Ex vivo localization of both PdG4 Oxyphor and PpIX were quantified. Under all isoflurane anesthesia conditions, leg skin pO2 levels significantly increased from 12-15 mmHg at the start of anesthesia induction (4-6 minutes) to 24-27 mmHg after 10 minutes (p < 0.05). Ketamine/xylazine anesthesia led to skin pO2 maintained at 15-16 mmHg throughout the 10-minute study period (p < 0.01). An increase of pO2 in mice breathing isoflurane was demonstrated with Oxyphor and PpIX DF, indicating similar intracellular and extracellular oxygenation. These findings demonstrate the importance of routine anesthesia administration, where consistency in the timing between induction and irradiation may be crucial to minimizing variability in radiation response.

Compact electron spin resonance skin oximeter: Properties and initial clinical results

Skin oxygen level is of significance for the diagnosis and treatment of many clinical problems, such as chronic wounds and diabetic foot ulcers. Furthermore, skin oxygen levels can be correlated to arterial oxygen partial pressure, thereby revealing potentially dangerous conditions such as hyperoxia (too much oxygen), which may occur in ventilated neonates. Traditionally, skin oxygen levels are measured using electrochemical methods and, more recently, also by fluorescence lifetime techniques. These approaches suffer from several drawbacks, rendering them suboptimal. The purpose of this work is to develop an electron spin resonance (ESR) -based method for monitoring oxygen partial pressure (pO2 ) in skin tissue. A compact sensor for pulsed ESR is designed and constructed. Our ESR-based method makes use of a unique exogenous paramagnetic spin probe that is placed on the skin in a special partially sealed sticker, and subsequently measuring its signal with the compact pulsed ESR sensor that includes a miniature magnet and a small S-band (~2.3 GHz) microwave resonator. The inverse of the spin-spin relaxation time (1/T2 ) measured by ESR is shown to be linearly correlated with pO2 levels. The sensor and its matching sticker were tested both in vitro and in vivo (with human subjects). Measured skin pO2 levels reached equilibrium after ~2-3 h and were found to be comparable to those measured by continuous-wave (CW) ESR using a large electromagnet. A compact pulsed ESR sensor with a matching paramagnetic sticker can be used for pO2 monitoring of the skin tissue, similar to large bulky CW ESR systems.

The absorption of oxygen from hyperbaric water

We tested the hypothesis that skin and muscle absorb O2 from hyperbaric water by soaking the feet of 10 subjects in tap water (CON; 1.8±0.3 mg·L−1 O2, PO2≈50mmHg, 31.5±0.4C°) or hyperbaric water (HYP; 49.6±1.8 mg·L−1 O2, PO2≈960mmHg 31.8±0.4C°) for 5 minutes. In order to show that oxygen was absorbed from the water, blood flow to the foot was arrested for 12 minutes prior to treatment. The occlusion was maintained during treatment and for 5 minutes following treatment. The rate of muscle O2 consumption (VO2mus) was significantly higher in HYP than in CON (0.009 ±0.001vs. 0.003±0.001ml·100g−1·min−1) at the end of treatment. Also, the concentration of oxidized cytochrome oxidase aa3 increased in HYP by 1.5±0.5μM and decreased 0.3±0.3μM in CON during treatment. Skin PO2 measured over plantar muscles in the arch of the foot after treatment was not different between CON and HYP. The PO2 declined from 162±2 to 53±7 in CON and from 158±9 to 57±9 mmHg in HYP over 5 minutes post-treatment. The skin PO2 in the big toe of HYP treated feet declined from 177±9 to 129±5 mmHg post-treatment. Taken together, these data show that a significant amount of oxygen can be absorbed from hyperbaric water by skin. In areas of the foot that lack metabolically active tissues (big toe) excess oxygen accumulates in the skin. In areas that have muscle, oxygen diffuses through the dermal thickness where it is used by the underlying metabolically active muscle..

Microcirculatory efficacy of topical treatment with aescin + essential phospholipids gel on transcutaneous PO2 in venous insufficiency.

A gel including aescin, essential phospholipids (EPL), and heparin (EG) has been used for many years for local treatment of venous, microcirculatory alterations (varicose veins, chronic venous insufficiency). Bruises, swelling, thrombophlebitis, and contusions are effectively treated with this compound. The aim of this study was the evaluation of the efficacy of the effects of an AEPL (aescin+EPL) gel on the microcirculation in subjects with chronic venous insufficiency, venous hypertension (CVH), and venous microangiopathy. Transcutaneous PO(2) was measured at the perimalleolar region. After 2 weeks of treatment, all individual values (100%) were significantly increased (p < 0.05). In all patients, PO(2) increased, indicating a decrease in level of venous microangiopathy. Considering transcutaneous skin PO(2), treatment with AEPL in areas of venous microangiopathy is beneficial in the prevention of ulceration and improves skin healing.

Microcirculation and O2 exchange through the skin surface: a theoretical analysis.

Oxygen is supplied to the upper layers of the human skin not only by blood, but also by surrounding air. Already in 1851 Gerlach measured this O2 uptake by glueing a horse bladder on the human skin (Gerlach (1851)). The bladder was made gas-tight by varnishing. He found that during a period of 24 hours the O2 concentration in the bladder decreased from 21.0% to 19.02%, whereas at the same time the CO2 concentration increased from 0% to 2.5%. He followed from his experiments that “the cutaneous respiration (i.e. the O2 uptake from the surrounding air) depends on the amount of blood which perfuses the uppermost capillaries and on its flow velocity. All that increases the amount of blood within the skin increases the cutaneous respiration.” To analyse the O2 supply of the different layers of the skin pO2 profiles perpendicularly to the skin surface have been measured (Baumgärtl et al. (1987). They reveal that there is a competition between the O2 supply by blood and that by surrounding air. Starting with the pO2 of the surrounding air tissue pO2 first decreases, reaches a minimum and then increases. This demonstrates that the upper part of the skin up to the pO2 minimum is supplied by the O2 of the air, i.e. by the O2 flux through the epidermis, whereas the other parts receive their O2 from the blood. The oxygen uptake from the air amounts to 80–100 ml O2/(m2·h), i.e. a human being with a skin surface of 1.5 m2 has an O2 uptake of 2.0–2.5 ml O2/min or of about 1% of its resting O2 uptake (Fitzgerald (1957). For the total organism it is a small amount, but it can be important for the oxygen supply of the skin.KeywordsSkin SurfaceIncrease Blood FlowDead LayerCapillary LoopArterial InflowThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

International Federation of Clinical Chemistry (IFCC): Scientific Division,Committee on pH, Blood Gases and Electrolytes: Guidelines for Transcutaneouspo2 and pco2 Measurement

This document provides guidelines for the terminology, methodology, and for the interpretation of data obtained from the use of skin (transcutaneous) po2 and pco2 electrodes. The transcutaneous technique has found special application in newborn infants. The causes of analytical bias with respect to arterial blood gas values, and imprecision obtained with transcutaneous pco2 electrodes, are reviewed. Electrode temperatures above 44°C should not be used routinely, and, at a measuring temperature of 44°C, the measuring site should be changed at least every 4 h to avoid skin burns.

The influence of the epidermal membrane on percutaneouspO2and metabolic rate

It is accepted that cutaneous pO2 measurements with polarographic oxygen electrodes measure a pO2 approximately 5 kPa below the theoretical arterial/capillary oxygen tension in patients with a mature skin surface. This difference is somewhat lower in neonates and prematures. The difference is caused by:the skin oxygen consumption,the oxygen diffusion resistance of the epidermal membrane, andthe oxygen consumption of the electrode.When stripping the epidermal membrane on 10 healthy volunteers, the skin pO2 measured by the E5250 oxygen electrode, increased on an average by 3.60 ± 0.93 kPa. The computed skin oxygen consumption rate was before stripping 0.327 ± 0.065 ml O2 · (100 g · min)-1 and 0.230 ± 0.088 ml O2 · (100 g · min)-1 after stripping. At an estimated capillary temperature of 43 °C mean arterial pO2 was estimated to be 18.1 kPa, which was reduced by local metabolism to a mean capillary pO2 of 14.4 kPa before and 15.2 kPa after stripping. Thus, stripping eliminated 82 % of the gradient between the...

Oxygen tension and consumption measured by a tc-PO2 electrode on heated skin before and after epidermal stripping.

Oxygen tensions, cutaneous blood flow rate, and skin oxygen consumption rate were determined by tc-PO2 measurements at an electrode temperature of 45 degrees C. The epidermal surface was stripped by 50 applications of adhesive plaster to the surface. Ten healthy, normotensive adults were examined. Cutaneous blood flow rate was 41.2 +/- 8.6 ml X (100 g)-1 X min-1 before and 42.8 +/- 5.9 ml X (100 g)-1 X min-1 after epidermal stripping. Oxygen consumption before stripping was 0.327 +/- 0.065 ml O2 X (100 g)-1 X min-1, and after stripping it was determined at two different saturation levels to be 0.208 +/- 0.072 ml O2 X (100 g)-1 X min-1 and 0.251 +/- 0.096 ml O2 X (100 g)-1 X min-1. Capillary temperature was estimated to be approximately 43 degrees C before and after stripping. At this temperature mean arterial PO2 was estimated to be 18.1 kPa (136 mmHg), which would be reduced by the computed local metabolism to a mean capillary PO2 of 14.4 kPa (108 mmHg) before stripping and 15.2 kPa (114 mmHg) after. Stripping increased mean skin PO2 from 10.9 +/- 0.6 kPa (82.3 +/- 4.7 mmHg) to 14.6 +/- 1.0 kPa (109.4 +/- 7.7 mmHg). Thus, stripping eliminated 82% of the gradient between the capillaries and electrode while reducing the computed oxygen consumption by 23-36%. It is concluded that the epidermal membrane is a significant barrier to oxygen diffusion and that the transcutaneous oxygen electrode has a significant effect on skin PO2 owing to its own even low oxygen consumption. This will reduce the observed skin PO2 significantly.

Short- and long-term effects of furosemide on lung function in infants with bronchopulmonary dysplasia

Although furosemide improves lung mechanics in some infants with broncho-pulmonary dysplasia (BPD), this may not be important unless gas exchange also improves. To determine the relationship between improvement in mechanics and improvement in gas exchange, the short- and long-term effects of furosemide therapy were studied in 16 spontaneously breathing infants with severe BPD who were both oxygen dependent and hypercarbic (mean PCO2 54 +/- 11 torr). Each infant was examined at least three times: before furosemide therapy, 1 hour after the first dose of furosemide, and after a 6- to 10-day course. Ten of the 16 infants were also examined three times during a 7-day control period. Transcutaneous PO2 and PCO2, esophageal pressure, air flow, and tidal volume were measured. Pulmonary resistance, lung compliance, and the alveolar to skin PO2 difference were calculated. After a single dose of furosemide, only compliance significantly improved. After prolonged therapy, compliance, resistance, and oxygenation significantly improved in the group as a whole, but better oxygenation was achieved in only six of 16 infants. tcPCO2 was unaffected by long-term furosemide therapy, but in all infants with decreased tcPCO2 1 hour after a single dose, there was sustained decrease in PCO2 after prolonged therapy. Changes in gas exchange were not explained by changes in lung mechanics. These data indicate that long-term diuretic therapy can improve the mechanical properties of the lungs of spontaneously breathing infants with BPD, but that gas exchange is usually unaffected.

1755 WHAT IS THE OBJECTIVE OF FUROSEMIDE THERAPY IN INFANTS WITH CHRONIC LUNG DISEASE?

Although furosemide (F) improves lung mechanics in infants with chronic lung disease (CLD), this effect may not be important unless gas exchange also improves. To determine the relationship between improvement in mechanics and improvement in gas exchange, we studied the acute and chronic effects of F therapy in 10 infants with CLD aged 4–24 weeks who were both oxygen dependent and hypercarbic. Each infant was studied 3 times: before F therapy, 1 h after the first dose of F (2 mg/Kg IV), and after a 6–10 day course (2 mg/Kg/day IV or 4 mg/Kg/day po). We measured skin surface (s) pO2 and pCO2, esophageal pressure, airflow and tidal volume; and we calculated pulmonary resistance (R), lung compliance (C) and the alveolar to skin (A–s) pO2 gradient. Criteria for improvement were a fall in PsCO2 > 2 torr, a fall in the A–s gradient > 10 torr, and a > 15% rise in C or fall in R. For the latter 4 variables we compared the acute effect of F with its chronic effect. We found that after both acute and chronic F, compliance, resistance and PsCO2 improved significantly from baseline values, but A–s pO2 gradient did not. Overall, mechanics improved in 9 patients, but gas excnange improved in only 6. In individual patients, improvement in R or C was unrelated to improvement in either gas exchange variable. However, the infants whose gas exchange chronically improved could be predicted by the acute change in PsCO2 or in pO2 gradient. We conclude that 1) F improves lung mechanics but may have little effect on gas exchange and 2) skin surface monitoring of the first dose of F can accurately identify those who will respond to chronic F therapy.

Effect of parenteral medications on tcPO 2/PaO 2 ratios

We studied the effect of parenteral infusions on transcutaneous arterial oxygen tension ratios in 31 newborn rabbits. Tolazoline and prostaglandin E1 produced a significant fall in skin PO2 values (P less than 0.01). Antibiotics, bicarbonate, diazepam, and dopamine infusions produced no change in PO2 ratios.

Model of Oxygen Transport through the Skin as Basis for Absolute Transcutaneous Measurement of PaO2

In the practical situation of tcPo2, measurements, oxygen is transferred from the dermis through the epidermis, a layer of connecting fluid, and the membrane and electrolyte of the measuring system to the cathode of the polarographic cell. By application of heat the mean capillary Po2, in the dermis (Pco2,) is supposed to be equal to Pao2. This hyperaemization effect is influenced by many factors, e.g., the peripheral blood flow, and has therefore been the subject of major interest in recent years. But even under ideal conditions transcutaneous measurement of Pao2, is still influenced by several other factors. Therefore we consider hyperaemization to be ideal and investigate the PO2, changes during oxygen transport from the arteries to the electrode with a partly well-known model. We can distinguish three effects, namely: 1 Increase of the Po2, when travelling from the arteries to the (warmer) capillaries due to a right shift of the oxygen dissociation curve of the blood. 2 Diffusional drop of the PO2, in the epidermis due to the oxygen flux introduced by the measuring system. 3 Diffusional drop of the PO2, in the inner layer of the epidermis due to the oxygen flux introduced by the oxygen consumption of the living cells. With a good electrode system consuming little oxygen, the second effect is very small and can therefore be disregarded, in other words, if the resistance to diffusion in the membrane of the measuring system is large as compared to that in the epidermis we may write: tcPo2,±PsO2, = Pao2, + ΔPao2, (T1) - PQo2 where: PsO2, = skin PO2, at the border of living and dead cells of the epidermis. Pao2, = arterial PO2, at a body temperature of 37d̀C. ΔPao2, (T1) = temperature correction term for T1±37d̀C ΔPQo2, = Po2, drop across the living layer of the epidermis due to cell metabolism TI = temperature of the mean capillary blood The ratio TR = tcPo2/Pao2 = 1 + (ΔPao2 (T1) - PQo2)/Pao2 will be unity if ΔPao2 (T1) = PQo2. It can be shown with the aid of the model and measurements at body temperature (where P-co2 is equal to PVO2 or higher) that the term PQo2 is not small as generally assumed, but greater than 30 mmHg. If for example, at normoxia (Pao2 = 100 mmHg) a TR of 0.7 is found, then a TR of approximately 0.5 and 0.85 may be expected for hypoxia (60 mmHg) and hyperoxia (200 mmHg) respectively. The model is also used to investigate the temperature distribution in layers parallel to the membrane of the polarographic cell as a function of the area covered by the measuring cell. Theoretically the temperature cf the mean capillary blood may be calculated from the formula for TR if TR and PQo2 are assessed experimentally, and a t the same time calibration for absolute measurement of Pao2 is possible if hyperaemization is such that venous admixture remains small.

1035 SKIN OXYGEN PERMEABILITY IN PREMATURE INFANTS

Human skin is permeable to O2 but the Po2 on the unheated intact skin is below 3.5 torr in adults and below 7 torr in term infants, both during air and O2 breathing. In small premature infants, however, we found skin Po2 to be much higher. We measured the Po2 on the nonheated skin surface with an unheated HUCH tcPO2 electrode in 24 newborn infants (gesta. 24-41 wks) at various FiO2 levels. The infants were studied in a thermoneutral environment at age 2-48 hrs. When the arterial O2 tension (PaO2) was 50-100 torr the mean surface Po2 of unheated skin was 27.2 (range 19-38) torr in infants <1500g, 14.3 (4-23) torr and those of 1500-2500g and 2.9 (2.5-5.0) torr in infants >2500g. Skin temperatures were not different between these groups. In contrast to adults and term infants, in infants <1500g the skin surface Po2 correlated with the PaO2 up to 100 torr (“unheated” skin Po2=0.33 PaO2+5.42; r=0.76). Crying, blood transfusion and phototherapy markedly increase the skin Po2 suggesting that a higher skin blood flow contributes more than differences in skin diffusion resistance or metabolism to the higher skin surface Po2 in resting premature babies. The concept of the unheated skin as a virtually oxygen tight system obviously has to be revised for premature infants. Practical implications however, must remain a matter of speculation since oxygen fluxes across the unheated skin have not been measured in small premature infants. Supported by Deutsche Forschungsgemeinschaft (SFB 147 and Ve 32/3).

Thin ring PO2 electrode using gold paste and its application to the study of the effects of venous occlusion on skin PO2.

Elevation of venous pressure produces a rapid increase of capillary pressure to a level above the pressure in the veins (Landis and Pappenheimer, 1963). When capillary pressure is raised capillaries which were previously closed may open, resulting in an increase of oxygen transport to peripheral tissue. To examine this possibility we constructed a rapidly responding PO2 electrode using gold paste.

Measurement of oxygen tension in human skin.

An oxygen microelectrode is described for the measurement of the skin pO2. Its characteristics of size, stability, sensitivity and reproducibility make it suitable for recording the skin pO2 in the clinical situation.