TcPO2 Levels Research Articles

Effect of Medial Arterial Calcification on O2 Supply to Exercising Diabetic Feet

We investigated whether medial arterial calcification (MAC) impairs O2 supply to the exercising foot in diabetic patients with foot lesions. Transcutaneous O2 tension (tcPO2) was monitored at the dorsum of the foot before and after bicycle exercise in 11 diabetic patients with peripheral ischemic vascular disease (PIVD) with or without concomitant existence of MAC, 10 patients with MAC but without PIVD, 10 diabetic control subjects, and 6 nondiabetic control subjects. The mean preexercise tcPO2 level was comparable in these four groups. However, tcPO2 decreased significantly with exercise in feet with PIVD (mean +/- SE -17.9 +/- 2.7%, P less than 0.01, n = 11), regardless of presence or absence of vascular calcification. On the other hand, the value increased significantly with exercise in feet with MAC but without PIVD (21.2 +/- 3.5%, P less than 0.01, n = 10) and in those of diabetic control subjects (14.9 +/- 3.6%, P less than 0.01), respectively. The tcPO2 remained unchanged in the feet of nondiabetic control subjects (1.7 +/- 1.1%). The results suggest that MAC is not associated with reduced O2 supply to the exercising foot in diabetic patients.

Oxygenation during chest physiotherapy of very-low-birth-weight infants: relations among fraction of inspired oxygen levels, number of hand ventilations, and transcutaneous oxygen pressure.

Chest physiotherapy (CPT) to clear the airway of infants requiring assisted ventilation is a routine procedure in neonatal intensive care units. This study was done to describe the relationships between fraction of inspired oxygen (FiO2) levels and the number of hand ventilations (independent variables) and variations of transcutaneous oxygen pressure (TcPO2) from baseline among intubated very-low-birth-weight (VLBW) infants receiving CPT. The study consisted of 30 observations of 13 intubated VLBW infants receiving CPT. Data were obtained by observations during routine CPT procedures performed by the nurses in charge of the infants. Stepwise multiple regression showed that hand ventilations and FiO2 levels significantly accounted for the variability in TcPO2 levels during CPT. Pearson correlation analysis showed that there was a negative correlation between FiO2 and TcPO2 and between the number of hand ventilations and TcPO2.

Multiple Physiological Indices in the Management of Chronic Leg Ulcers

Transcutaneous oximetry (Tc Po2), laser Doppler flowmetry (LDV) and arterial Doppler index (DI) have been used to predict healing in 20 patients with chronic leg ulcers. This study showed that patients with improving or healed ulcers had significantly higher Tc Po2 levels adjacent to the ulcer ( P < 0.02) and lower LDV ( P < 0.05) and a tendency to higher DI than worsening or static ones.

Cutaneous Hypoxia in Patients With Systemic Sclerosis (Scleroderma)

Measurement of transcutaneous oxygen pressure (TCPO2) is an established and noninvasive way of assessing cutaneous hypoxia. Since the degree of oxygenation modulates fibroblast growth and synthesis, we investigated the presence of cutaneous hypoxia in patients with systemic sclerosis (SS). We measured TCPO2 of the involved skin of the dorsal aspect of the forearm in 33 patients with SS and 16 control individuals (normal subjects and patients with Raynaud's disease). The degree of forearm skin thickness was assessed clinically as mild, moderate, or severe. The TCPO2 measurements were obtained at a sensor temperature of 44 degrees C, which causes maximal vasodilation and eliminates the variables associated with vascular tone. Measurements were recorded while patients were breathing room air or 31% oxygen delivered by a Ventimask system (Baxter Healthcare, Ocala, Fla). We also measured the TCPO2 of the medial aspect of the arm when this site was uninvolved. We found that sclerodermatous skin is hypoxic when compared with the uninvolved skin of patients with SS or control individuals. The TCPO2 values were indirectly related to skin thickness; thus, patients whose skin was severely thickened had the lowest TCPO2 values. There was no correlation of TCPO2 values with pulmonary function tests or arterial oxygen pressure. The TCPO2 levels of patients with Raynaud's disease did not differ from other control individuals. The administration of oxygen increased TCPO2 readings in patients with SS to normal values. We conclude that the thickened skin of patients with SS is hypoxic and suggest that TCPO2 measurements may be helpful in objectively assessing the degree of skin thickness. The hypoxia demonstrated in SS skin may play a role in the modulation of dermal fibroblast proliferation and synthetic activity.

Changes in transcutaneous oxygen tension as a result of prolonged pressures at the sacrum.

Prolonged pressures at the patient support interface can lead to the impairment of tissue viability resulting in tissue breakdown, particularly in debilitated individuals. However there are still few clinical guidelines to indicate safe levels of pressure and time for individual tissue areas. The effects of extended loading on transcutaneous oxygen tension (tcPO2) were examined at the sacrum of twenty debilitated subjects, prone to tissue breakdown. Each load was applied for a ten minute period through an indenter incorporating a commercial oxygen electrode. Loads were incremented until the tcPO2 levels were reduced below 2.7 kPa (20 mmHg), at which time the tissue was unloaded. The interface pressure for each applied load was measured. Results are presented in terms of relating applied pressure and time to relative changes in tcPO2. When all the results are combined it is clear that there is a range of applied pressures which significantly reduce the tcPO2 levels. The applied pressures to produce, for example, 50% reduction of the unloaded resting value, ranged from 3.0 kPa (22 mmHg) to 12.2 kPa (92 mmHg). This indicated the individual nature of the tissue response, which should be determined before clinical guidelines of safe pressure levels are established.

Human fetal oxygenation (tcPo2), heart rate variability and uterine activity following maternal administration of meperidine.

Fetal tcPo2 levels were measured in 10 patients following maternal administration of 50 mg of meperidine by intravenous route. About 3 minutes following injection of meperidine, tcPo2 values started to decline to reach the lowest value of 37 +/- 25% by 7 mins of injection. tcPo2 values recovered by about 15 mins following injection. These changes in fetal tcPo2 levels preceded transient minimal increase in FHR variability. The increase in FHR variability was followed immediately by a decrease in the indices of the FHR variability. The uterine activity began to decline below the predicted positive slope values shortly following injection of meperidine. This decline was maximum 15 mins post-injection, subsequently establishing a trajectory toward the positive values expected for unmedicated labor. Two patients receiving 25 mg intravenous meperidine demonstrated no decline in tcPo2 levels; however, in the patient receiving 75 mg of intravenous meperidine, the changes noted were similar to those observed following 50 mg of meperidine.

THE EFFECT OF THE MOTHER'S VOICE ON THE PHYSICAL ACTIVITY (A) AND tcPo2 OF VERY PREMATURE INFANTS

Nine infants of 26-29 w PMGA (BW 780-1270 g)were exposed to the mother's voice from a tape recorder via loudspeaker (at∼70 dB) 5×30′ a day between 29 and 38 w PMGA(for X 8.2 w) after conditions were stabilized. At 2 days each week the babies' behaviour (applying an A rating from 1 =quiet sleep to 6 = crying) and tcPo2 was recorded every 10″ for 1 hour, once without and once with m's voice (30′ after 30′“base line”).Results: A and tcPo2 varied significantly during tests In 43-57 percent of “blanc” observations and with m's voice (table), but in the latter case significantly more often A level fell (Δ X-.5 points; p<.001) and tcPo2 level rose (ΔX +.4 kPa; p<.005) during stimulation. Means of 15′ periods of A and tcPo2 correlated inversely (r=-.55).Conclusions: 1) Premature infants react to acoustic stimuli after 28 w PMGA, If hearing is unimpaired and/or stronger stimuli do not Interfere. 2) M's voice can tranquilize the baby increasingly reproducible causing a transient increase of tcPo2. 3) Recorded m's voice may serve as a substitute, if the mother cannot stay with her baby, to the benefit of both.

The predictability of the success of arterial reconstruction by means of transcutaneous oxygen tension measurements

The cases of 100 patients with severe peripheral vascular disease were reviewed to determine whether the success or feasibility of arterial reconstruction could be correlated with the increase in transcutaneous tissue oxygen tension (tcPo2) that occurs in all persons when assuming an erect posture from the supine position. Resting supine tcPo2 levels of 20 mm Hg or less at the foot were noted in all patients in this study (normal values 60.10 ± 6.82 mm Hg). Group I patients were defined by an increase of less than 15 mm Hg on standing, whereas group II patients showed an increase of 15 mm Hg or more. Group I patients had a supine tcPo2 value of 4.24 ± 5.31 mm Hg, with an increase of 3.91 ± 4.59 mm Hg on standing. The group II subjects also had a low supine tcPo2 level, 5.73 ± 4.98 mm Hg, but the increase on standing, 36.14 ± 11.41 mm Hg, was significantly higher (p < 0.001). When these levels increased by less than 15 mm Hg on standing in group I (31 patients), only 29% of limbs (10 of 34) were saved or had patent grafts at 3 months and 55% of attempted vascular reconstructions (11 of 20) failed. Amputations were performed in 50% of the limbs (17 of 34). This contrasted in group II (69 patients) with a significantly higher limb salvage and graft patency rate (81%, 57 of 70 limbs), success of reconstruction (79%, 37 of 47 procedures), and a significantly lower rate of amputation (11%, 8 of 70 limbs) (p < 0.001). We conclude that a failure to increase the tcPo2 reading at the foot by at least 15 mm Hg on standing indicates a poor prognosis for arterial reconstruction in patients suffering from gangrenous or pregangrenous lesions of that foot.

Inflammation and transcutaneous measurement of oxygen pressure in dermatology.

In this study the influence of local inflammation on tcPO2 values at different electrode temperatures has been investigated. The measurements were performed on UV-erythema, contact dermatitis and other inflammatory reactions of the skin. Different types of inflammation and different degrees of damage can lead to very different reactions in the microcirculation and this will have an effect on the tcPO2 levels.

Pression transcutanee d'oxygene et apnees au cours des stades de sommeil chez des nourrissons normaux et a risque de MSIN

The relationship between chronic hypoxemia and sudden infant death syndrome (SIDS) has been reported by several authors. In order to study the influence of the apnea-time during a sleep state on transcutaneous oxygen tension (tcPO2), we have studied polygraphically 30 full-term infants (10 controls, 10 SIDS siblings and 10 near-miss for SIDS), aged from 5 to 13 weeks. No significant difference was observed either for apnea-time or tcPO2 between infant-groups studied in different sleep states. We could not find any correlation between apnea-time and tcPO2 in all groups of infants studied during different states of sleep. It is therefore concluded that in normal and at risk for SIDS infants, tcPO2 levels during sleep states cannot be explained only by the apnea-time.

Physiologic Circadian Rhythmicity in Preterm Infants

This study investigated evidence of a circadian rhythm in the physiologic variables of transcutaneous oxygen (tcPO2) level, pulse rate, respiratory rate, frequency of respiratory pauses, and skin temperature in six 34- to 37-week-preterm infants. A value for each variable was noted every 30 minutes for 24 hours, providing 245 observations for each infant. An adaptation of cosinor analysis, a least squares procedure that determines the cosine curve for a 24-hour period that best fits the observed pattern of values, was applied to the data. Statistically significant circadian rhythmicity was found for five of the six subjects with regard to skin temperature. Significant circadian rhythm was also demonstrated in two or three patients for all other variables. No significant consistent synchrony for individual variables across subjects was found. Actual peak values of respiratory pause frequency and trough values of tcPO2, however, occurred between midnight and 4:30 A.M. for every infant. Preterm infants exhibited evidence of a circadian rhythm in skin temperature, and tcPO2 and respiratory pause frequency exhibited day/night pattern characteristics.

Transcutaneous oxygen tension of newborn infants in different behavioral states.

Transcutaneous oxygen tension (tcPO2) was continuously monitored, and behavioral state was evaluated in a group of 10 normal preterm infants and 10 normal term infants. In the preterm infant group, birth weight was 1505 +/- 154 g, gestational age was 32.3 +/- 2.3 wk, and postnatal age was 8.4 +/- 5.1 days (mean +/- S.D.). In the term infant group, birth weight was 3245 +/- 247 g, gestational age was 39.9 +/- 0.3 wk, and postnatal age was 6.3 +/- 3.4 days (mean +/- S.D.). A mean tcPO2 level for each behavioral state in each infant was calculated, and a paired comparison between all states was made. In the preterm and term infant groups, mean tcPO2 levels were higher in state 1 ("quiet sleep"), state 4 ("active awake state"), and state 5 ("crying") than during state 2 ("active sleep"). The difference (delta tcPO2) was significant (P < 0.05). In the preterm infant group, mean tcPO2 level in state 2 was 62.9 +/- 17.1 mm Hg (mean +/- S.D.). Mean delta tcPO2 in state 1 was +5.4 mm Hg (range, -0.9 to +9.2 mm Hg), mean delta tcPO2 in state 4 was +6.8 mm Hg (range, +0.6 to +20.2 mm Hg), and in state 5 was +9.9 mm Hg (range, +5.1 to +17.5 mm Hg). In the term infant group, mean tcPO2 level in state 2 was 64.5 +/- 9.6 mm Hg (mean +/- S.D.). Mean delta tcPO2 in state 1 was +5.8 mm Hg (range, -1.2 to +11.0 mm Hg), mean delta tcPO2 in state 4 was +8.1 mm Hg (range, +2.2 to +32.3 mm Hg), and mean delta tcPO2 in state 5 was +7.3 mm Hg (range, -1.6 to +26.5 mm Hg). There was insufficient data to evaluate tcPO2 levels during state 3 ("quiet awake state"). In the term infant group, the effect of bottle feeding on tcPO2 was also assessed. Gross alterations in tcPO2 during bottle feeding were not observed, and mean tcPO2 levels during bottle feeding (76.1 +/- 8.5 mm Hg; mean +/- S.D.) were not significantly different from mean tcPO2 levels found during states 1, 4, and 5.

Sleep induced PO2-changes in preterm infants

In seven healthy preterm infants the transcutaneous PO2 was measured during different sleep states. The tcPO2 is lower during active sleep than during quiet sleep and shows a higher variability in active sleep. The incidence of apneic spells, which occur predominantly during active sleep, was not found to be correlated to tcPO2 levels.

The effect of nonnutritive sucking on transcutaneous oxygen tension in noncrying, preterrn neonates

AbstractThe relationship between transcutaneous oxygen tension (tcpO2:) and sucking opportunities in noncrying, preterm neonates was investigated. Twenty‐six measurements of nonnutritive sucking and its relationship to tcpO2 were collected on 11 neonates who were monitored continuously for tcpO2. Of the 26, 10 sets of measurements were recorded on 6 neonates receiving assisted ventilation, and 16 were recorded on 4 neonates breathing room air. One neonate was measured one time on assisted ventilation and two times breathing room air. The design consisted of three 8‐minute time periods: pretreatment, treatment (sucking opportunities). and posttreatment. There was a significant relationship between the pretreatment‐treatment and treatment‐posttreatment tcpO2 levels (both at p &lt; .01). These results suggest that sucking facilitates more adequate oxygenation in noncrying, preterm neonates.