Transcutaneous PO2 Research Articles

The Effect of Elastic Compression on Tcpo2 in Limbs with Venous Stasis

A low oxygen tension might contribute to the dermatological changes produced by deep venous insufficiency and venous stasis. Since elastic support is often prescribed for stasis disorders, it would be of value to know whether compression alters the oxygen tension in affected skin. We performed studies in which the transcutaneous Po2 (TcPo2) was determined for the foot or lower leg in subjects with normal veins (n = 9) or with dermatitis caused by documented deep venous insufficiency (n = 14). Measurements were made using O2-sensing electrodes placed 1–2 cm apart; surface temperature was 45°C for one electrode (producing maximal vasodilation of the underlying skin) and 42°C for the other (producing submaximal vasodilation). The vasodilation index (VI = TcPo2 at 42 °C/TcPo2 at 45°C) was used as an index of vasomotor tone. In normal limbs, TcPo2 (mmHg) and VI were affected by the subject's posture (TcPo2 = 38.8 at 42°C and 61.4 at 45°C when supine; 40.8 at 42°C and 74.6 at 45°C when upright with legs dependent; VI = 0.63 supine and 0.53 upright). In limbs with venous stasis, TcPo2 and VI were considerably lower (TcPo2 = 23.6 at 42°C and 51.5 at 45°C when supine; 20.8 at 42°C and 60.5 at 45°C when upright; VI = 0.48 supine and 0.37 upright). Following the application of an elastic wrap to the limbs with stasis, upright values for TcPo2 and VI were substantially improved (TcPo2 with compression = 28.8 at 42°C and 62.4 at 45°C; VI = 0.46). We conclude that (1) TcPo2 is reduced in regions of skin affected by stasis dermatitis, and (2) elastic compression improves TcPo2 (during upright posture) in limbs with stasis dermatitis.

Transcutaneous PO2 and laser Doppler blood flow measurements in 40 patients with venous leg ulcers

The study included 40 patients with clinically venous leg ulcer(s) in one leg only and with a systolic toe blood pressure above 50 mmHg in both legs. Transcutaneous oxygen tension was measured on both lower legs at equivalent sites, on the affected leg immediately proximal to the ulcer(s). Similarly, skin blood flow was measured in both legs at a skin temperature of 32 degrees C and 44 degrees C by means of laser Doppler velocimetry, and for each leg the index of blood flow 44 degrees C/flow 32 degrees C was calculated to express the degree of blood flow increment following local hyperthermia. Transcutaneous oxygen tension measurements were significantly lower on affected legs (p less than 0.01) as was flow increment (p less than 0.01), mainly due to a high flow measurement at 32 degrees C on affected legs rather than to a low measurement at 44 degrees C. The results of our flow measurements suggest a state of (relative) hyperemia in the vicinity of venous leg ulcers, also confirmed by the clinical findings. This could be interpreted as an arteriolar response to lowered oxygen tension or (it could) be part of reactive reparative processes leading to increased O2 consumption in the tissues.

Quantification of patch test reactions by transcutaneous PO2 measurement

The usefulness of transcutaneous oxygen tension (tc-PO2) measurement for quantification of positive patch test reactions was studied. A significant correlation was found between the visual grading and the quantitative tc-PO2 values. Tc-PO2 discriminated between visual grade 0 to 1+, 1+ to 2+, and 2+ to 3+ reactions. The results obtained by this method were compared with those obtained by other quantitative methods. Tc-PO2 measurement can be regarded as complementary to the laser Doppler technique, since it lacks the sensitivity of the laser Doppler technique in the range in negative to 1+ patch reactions, but it does discriminate between 2+ and stronger reactions.

Transcutaneous Oxygen Monitors Are Reliable Indicators of Arterial Oxygen Tension (If Used Correctly)

The following recommendations should always be kept in mind: Each new transcutaneous equipment, or modification of equipment, must be adequately tested in vivo as well as in vitro. The users must have basic understanding of the principles and the major requirements for applying the tcPO2 technique. Calibration procedures must be carefully adhered to according to the manufacturer's instruction. The temperature of the electrode must be kept at 44 degrees C for premature infants and at 44 degrees or 45 degrees C for term infants if the clinical aim is to estimate arterial PO2 levels. Resetting of the electrode must then be done every two hours. For sick infants, this may be needed more frequently. Whenever there is cause to compare tcPO2 values with arterial ones, the latter must be obtained from an appropriate vessel. Great care must be taken when drawing and analyzing blood for PO2. The infant should not be crying. Significantly lower transcutaneous PO2 values than arterial PO2 values are due to either one or several of the errors indicated above or to an insufficient circulation under the electrode. In recent years, technical or clinical errors seem to have become more and more common. Thereby the technique has unjustly fallen into disrepute. Insufficient circulation under the electrode rarely occurs in the newborn infant and then only in those who are in overt shock.

Effects of metaproterenol on pulmonary mechanics, oxygenation, and ventilation in infants with chronic lung disease

Changes in pulmonary resistance, dynamic compliance, tidal volume, and transcutaneous PO2 and PCO2 after nebulized administration of metaproterenol were evaluated in eight newborn infants (birth weight 650 to 1060 g, gestational age 25 to 28 weeks) with chronic lung disease receiving mechanical ventilation. The infants were monitored continuously before and for 15 minutes after nebulization of metaproterenol during 3 consecutive days at mean age 34 days. There were significant increases in compliance, tidal volume, and tcPO2, and significant decreases in pulmonary resistance and tcPCO2. These data show that bronchospasm contributes significantly to the high pulmonary resistance in preterm infants with chronic lung disease and that metaproterenol is beneficial in the therapy of infants with chronic lung disease requiring mechanical ventilation.

Examinations on the blood flow dependence of tcPO2 using the model of the "circulatory hyperbola".

The relation of transcutaneous pO2 (tcpO2) and cutaneous blood flow (CBF) was measured on the forearm of 19 healthy volunteers by use of a tcpO2 electrode heated to 45 degrees C. CBF was estimated indirectly from the heating power of the electrode (HP) and with a 8 MHz bidirectional ultrasonic probe by Doppler shift in a fingertip warmed to 45 degrees C (DF). Arterial blood flow was regulated by a cuff on the upper arm. The arterial flow was reduced in 10-15% stages of effective perfusion pressure Peff. There was a decrease in pO2 when CBF was restricted in stages as suggested by the model of the "circulatory hyperbola" according to Lübbers. A linear dependence between Peff, HP and DF was observed. These results indicate, that there is no autoregulation in the hyperemizied capillary bed. During respiration of air mean tcpO2 was 86.0 Torr (+/- 6.2) in normal blood flow conditions and reflects well paO2. Transcutaneous pO2 may also be used as a measure of CBF. To distinguish between these two modes, the determination of paO2 in capillary blood probes is necessary for calculating the transcutaneous index tcpO2/paO2.

Monitoring with transcutaneous po2 and pulse oximetry devices

Monitoring with transcutaneous po2 and pulse oximetry devices

Effect of antepartum ritodrine on the cardiorespiratory status of the newborn after elective cesarean section.

Heart rate (HR), heart rate variability (HRV), respiratory rate (RR) and transcutaneous PO2 and CO2 of 12 infants born by elective cesarean section were monitored during the first postnatal hour in order to evaluate the effect of the beta-mimetic tocolytic drug ritodrine. Six of the mothers received ritodrine by infusion and the other 6 physiological saline during the 2 h prepartum. The Apgar scores of the treatment group were higher (p less than 0.05) but there was a significant increase in RR (p less than 0.05) during the first hour in these babies. Arterial blood pressure (BP) was lower in the group whose mothers had received ritodrine (p less than 0.05) but there was no difference in pulse pressure. Transcutaneous pressure of CO2 (PtcCO2) of the controls decreased during the first hour (p less than 0.05). Transcutaneous pressure of O2 (PtcO2) increased during the first postnatal hour (p less than 0.01) when both groups were examined together. HR of both groups was relatively high and HRV low.

Transcutaneous PO2 and PCO2 during surfactant therapy in newborn infants with idiopathic respiratory distress syndrome.

We conclude that surfactant treatment in newborn infants with IRDS results in decrease in TcPO2 and an increase in TcPO2 within minutes. The surfactant treatment procedure used in this study was not associated with hypoxemia. During surfactant treatment monitoring of TcPO2 and TcPCO2 is absolutely necessary.

Comparison of Laser-Doppler-Flux and tcPO2 in healthy probands and patients with arterial ischemia.

Transcutaneous PO2 (tcPO2) and Laser-Doppler-Flux (LDF) were compared on the dorsum of the foot in 20 healthy probands and 35 patients with peripheral arterial occlusive disease at clinical stage II b or IV. The probes were kept at a temperature of 37 degrees C. Using different procedures, we brought about dynamic changes and compared the reaction of the two signals. Venous occlusion resulted in a decrease of both signals to a similar extent in both groups. During leg dependency both signals decreased in the probands suggesting a normal vasoconstrictor response. In most of the patients an increase was observed, but some showed a decrease even at clinical stage IV. LDF had a stronger tendency towards a decrease. On leg elevation, LDF slightly increased in probands and decreased in patients. Here, the tendency towards a decrease was higher for tcPO2. After arterial occlusion reactive hyperemia was more pronounced in probands. Differences between tcPO2 and LDF seem to be mainly due to the different capillary systems contributing to the signal.

Study of the Pharmacokinetics and Pharmacodynamic Activity of Almitrine Bismesylate in Infants during the Recovery Phase following Bronchopulmonary Dysplasia

The efficacy and pharmacokinetics of almitrine bismesylate were studied in 6 infants (age 2.5-9.5/months) during the recovery phase following bronchopulmonary dysplasia. The infants did not require assisted ventilation, but needed oxygen therapy with an FiO2 of 25-30% in stable condition. One to three hours after a single oral dose of almitrine (1.5 mg/kg), there was a marked increase in transcutaneous PO2 (TcPO2) (mean 2kPa) followed by a regular decrease to the baseline level. Nine to fourteen days after repeated administration of almitrine (1.5 mg/kg/12 h) in 4 children, the mean gain in TcPO2 was only 0.85 kPa. There was a very early flagging in efficacy of almitrine, since none of the children could be weaned from oxygen therapy. The absorption peak occurred 1-3 h after the administration of the compound. The maximum almitrine concentration was 173 +/- 44 ng/ml; plasma clearance was 21.9 +/- 6.6 ml/min and the volume of distribution was 18.7 +/- 2.1 liters/kg. The drug was eliminated biphasically. In the 4 studies with repeated drug administration, the pharmacokinetic results suggested that a steady state was still not achieved after 9-14 days of treatment. These results and the absence of any sustained effect of repeated doses of the drug raise the problem of a particular type of almitrine metabolization in the infant.

Transcutaneous monitoring as trigger for therapy of hypoxemia during sleep.

Based on results on central chemosensitivity in cats, paired stimuli were applied for therapy to infants with central respiratory insufficiency of various degrees. An unspecific respiratory stimulus, e.g. light for 1 s, was followed by a jet of either O2 or 2% CO2 in O2 for 1.5 s. The unspecific and the chemical stimuli were interspaced by 0.5 s. The combined stimulation was repeated every 10 s. The program was triggered by using threshold values of transcutaneous pO2. In infants with intratrachial tubes or tracheostoma we used the end tidal pCO2 for triggering the stimulation. The method could prevent hypoxemia during sleep in non-ventilated subjects with sleep apnea syndromes or in infants with severe hypoxemia during sleep after being rescued from Sudden Infant Death Syndrome (SIDS). In patients with Ondine's Curse Syndrome (OCS) with its CO2 insensitivity, paired stimuli were used in order to condition the chemical function of the respiratory system. Polysomnograms from 310 clinically healthy infants including healthy siblings of SIDS victims revealed instability of arterial pO2 and low CO2 sensitivity during sleep within the second month and the fourth to ninth month of life, respectively. These data challenge the described method as a potential preventive or therapeutic measure to defeat SIDS and sleep apnea syndromes in conjunction with disturbed chemical regulation of respiration.

Measurement and processing of fetal transcutaneous Pco2 levels.

Because asphyxia is not the only factor influencing fetal heart rhythm, a non-optimal cardiotachogram is not necessarily a sign of fetal distress. It makes further evaluation of the fetal condition advisable, especially determination of the acid-base equilibrium. The method of fetal blood sampling, introduced by Saling, has a number of disadvantages for mother and fetus, because of the invasiveness for both. Further, the measured acid-base equilibrium is only representative for a very short period of time and often repeated micro-blood sampling is necessary. A major problem with regard to determination of the acid-base equilibrium in intermittently obtained fetal blood samples is the inclusion of air bubbles in the sample. When they are introduced into the electrode cuvettes, the measured values cannot be considered reliable. The problem was solved in the Department of Obstetrics and Gynecology of the Vrije Universiteit of Amsterdam with a "pipe" shaped special collecting vessel. Similar measuring results were obtained with the formerly used glass capillary method and the special collecting vessel method. Continuous, non-invasive methods have been pursued to avoid the above mentioned problems. Fetal transcutaneous Po2 measurement has been possible for years, but does not provide adequate information during the important second stage of labor because of methodological problems. Continuous fetal tissue pH surveillance is possible, but it also has an invasive character and is technically difficult to perform, leading to many methodological failures. Recently, continuous transcutaneous Pco2 measurement tcPco2 became available. A good correlation was found with simultaneously measured Pco2 levels in fetal blood samples and with those of umbilical artery blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Effectiveness of combined transcutaneous PO2/PCO2 monitoring of newborns.

Non-invasive monitoring of oxygen pressure by means of a transcutaneous PO2 electrode has become standard practice in newborn intensive care units (2). This also holds for transcutaneous measurements of Pco2 (1). It is of clinical importance that an infant’s skin surface is as available as possible, for example for X-ray and phototherapy. It is therefore appropriate to accommodate both the Po2 electrode and the Pco2 electrode into one sensor.KeywordsCombine ElectrodeIntensive Care DepartmentNewborn Intensive Care UnitTranscutaneous Carbon DioxideCombine SensorThese 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.

Microvascular dynamics during acute asphyxia in chronically prepared fetal sheep near term.

From previous studies in both human and sheep fetuses we concluded that reduced blood flow to the fetal skin after repeated episodes of asphyxia indicates circulatory centralization of the fetus, which can be detected by transcutaneous pO2 measurements (Jensen and Klinzel, 1980, 1982; Jensen, Kunzel, and Kastendieck, 1982, 1983, 1985; Jensen, Kunzel, and Hohmann, 1985a, 1985b; Jensen, Hohmann, and Kunzel, 1987). This conclusion was based on two experimental findings. First, increasing catecholamine concentrations in the fetal sheep’s plasma correlated with changes in blood flow to peripheral and central organs, measured by radionuclide labeled microspheres (Rudolph and Heymann, 1967). Secondly, blood flow to the skin correlated with blood flow to other peripheral and central organs. For example, the decrease in blood flow to the skin after repeated episodes of asphyxia was accompanied by a decrease in blood flow to the kidney, spleen, and small intestines, and by an increase in blood flow to the brainstem (Fig. 1).

Transcutaneous oxygen tension during exercise in patients with pulmonary emphysema.

Transcutaneous PO2 (tcPO2) and arterial PO2 (PaO2) were compared during exercise in six patients with pulmonary emphysema. For calibration purposes, the tcPO2 electrode was first attached to the skin and after stabilisation its reading was adjusted to correspond to the PO2 of an initial arterial blood sample. It was shown that tcPO2 measurement could follow accurately the rapid changes in PaO2 occurring during exercise. Sixty-eight paired comparisons of PaO2 and tcPO2 were available and the regression equation was given by: tcPO2 (mmHg) = 0.98 PaO2 + 0.7 (correlation coefficient, 0.985; 95% confidence limits, 5.7 mmHg).

Diagnostic assessment of diabetic microangiopathy by tcPO2 stimulation tests.

Transcutaneous PO2 measurements at 37 degrees C can recognize and quantify diabetic microangiopathy if suitable stimulation tests are used. The following parameters are of practical importance: resting PO2, postocclusive PO2, rubefacient-induced PO2 and 45 degrees C heating PO2. Patients with diabetic microangiopathy show diminished PO2 values in rubefacient-induced PO2 and 45 degrees C heating PO2. The former ist probably related to endothelial-cell function disturbances and the letter to organic vessel wall changes. Thus, a quantitative and differentiated picture of microangiopathy can be obtained in each individual patient.

Transcutaneous monitoring of PO2 and PCO2 during running--a noninvasive determination of gas transport.

Transcutaneous pO2 and pCO2 (tcpO2 and tcpCO2) were measured during running with stepwise increased velocities and with constant speed, under both aerobic and anaerobic conditions, for the determination of blood gas transport during exercise. Arterial and transcutaneous blood gas values correlated significantly (pO2 r = 0.87, p less than 0.001, pCO2 r = 0.91, p less than 0.001 respectively). Transcutaneous pCO2 is a noninvasive method of monitoring arterial pCO2 and lactate formation during exercise. When athletes run, arterial pO2 falls to a specific limit depending on the intensity of work. This seems to be characteristic for maximum oxygen transport capacity. The aerobic endurance measured by the aerobic-anaerobic threshold may be dependent on the possibility of sustaining low arterial pO2 during high working levels at high oxygen consumption.

Transcutaneous oxygen measurement: experimental studies and adult applications.

Transcutaneous PO2 sensors have been developed over the past ten years from the same basic electrodes used in conventional blood-gas machines. The skin is heated to enable the skin surface sensors to respond quickly to the gas tensions beneath them. PtcO2 is a variable that reflects the PO2 in the peripheral tissue. PtcO2 has its own range of normal values, and it responds to cardiopulmonary changes that affect tissue oxygenation. In most patients, those without decreased cardiac output, PtcO2 follows the trend of PaO2 and decreases relative to PaO2 with increasing patient age (see Table 2). In the presence of severely reduced cardiac output and peripheral perfusion, the PtcO2 values will deviate from their relationship with the arterial tensions and become blood flow dependent, thus providing quantitative information regarding blood flow. The technique of PtcO2 monitoring likely will gain wider acceptance because it is a noninvasive and continuous monitor that provides useful information regarding tissue oxygenation.

Pulse oximetry versus transcutaneouspO2in sick newborn infants

A pulse oximeter (Ohmeda Biox 3700) and two transcutaneous systems (Radiometer TCM3) were applied simultaneously to 18 newborn infants with respiratory insufficiency. All infants had either an umbilical catheter placed in the mid thoracic aorta or a radial artery catheter. The average monitoring time was 2 hours. Arterial blood pO2, pCO2 and pH (Radiometer ABL300), arterial sO2, HbCO and metHb (Radiometer OSM3), erythrocyte 2,3 DPG concentration, and fetal hemoglobin fraction (alkali denaturation kinetic method) were measured.Using arterial sO2 and pO2 as reference, the analytical bias of pulse oximetry (-0.5 ±1.0%, mean ± 1 SD) corresponded in magnitude, when coverted to pO2, to that of transcutaneous -pO2 (0.6 ±1.4 kPa for combined O2-CO2 electrode and -0.1 ±2.3 kPa for single O2 electrode). Transcutaneous pCO2 showed the smallest bias (0.3 ± 0.3 kPa). Both pulse oximetry and transcutaneous pO2 electrodes were good as trend monitors detecting rapid changes in the infants' oxygenation status. The pulse oximeter offers certain advantages in not requiring calibration or heating. The variations in the levels of fetal hemoglobin fraction (44 to 97 %), pH (7.27 to 7.49), pCO2 (3.3 to 6.8 kPa) and 2,3 diphosphoglycerate concentration (1.6 to 5.9 mmol/1) between the infants studied, resulted in a variable pO2-sO2 relation (p50 2.5 to 3.5 kPa). This presents difficulties in interpreting sO2 values in sick newborn infants, and we therefore recommend caution in using apulse oximeterto apply strict limits foravoiding hypoxia and hyperoxia in this population.