tcPO2 Monitoring Research Articles

A comparative research of effect on inserting a distal perfusion catheter and preventive insertion of a distal perfusion catheter based on the limb ischemia risk assessment table in patients with extracorporeal membrane oxygenation

To compare the treatment effect of venous-arterial extracorporeal membrane oxygenation (VA-ECMO) patients in the prophylactic distal perfusion catheter (DPC) and the non-prophylactic DPC. A prospective randomized controlled trial (RCT) was conducted. Patients who received VA-ECMO treatment were reviewed at Affiliated Jinhua Hospital, Zhejiang University School of Medicine from January 2019 to June 2020 were divided into two groups, the prophylactic DPC group (DPC placed immediately after the patient VA-ECMO) and the non-prophylactic DPC group (the DPC was placed after the early limb ischemic signs by using evaluation of the lower extremity perfusion assessment table). Comparing the differences of clinical data of two group patients. Pearson correlation analysis was used to analyze the correlation between peak velocity of dorsalis pedis artery and peak velocity of posterior tibial artery and transcutaneous oxygen partial pressure (TcPO2). A total of 62 patients were included in the analysis, with 31 cases in prophylactic DPC group and another 31 cases in non-prophylactic DPC group. There were no significant differences in sex, age, body mass index (BMI), smoking index, underlying disease, catheterization site, recovery time before on machine, extracorporeal membrane oxygenation (ECMO) operation time, mechanical ventilation time, length of stay in intensive care unit (ICU), mortality rate in hospital, and acute physiology and chronic health evaluation II (APACHE II) between the preventive DPC group and the non-preventive DPC group. There was no significant difference in ECMO indications, ECMO intubation location and pipeline type. The bleeding in the non-prophylactic DPC group was lower than that in the non-prophylactic DPC group [6.5% (2/31) vs. 29.0% (9/31), P < 0.05]. There were no significant differences in limb complications such as cyanosis, necrosis, amputation, compartment syndrome, arterial thrombosis, vascular reconstruction and repair, pseudoaneurysm, limb ischemic or limb infection. During the ECMO operation, except the blood stream infection in the non-prophylactic DPC group was lower than that in the non-prophylactic DPC group [3.2% (1/31) vs. 19.4% (6/31), P < 0.05], there was no other statistical difference in complications between the two groups. The peak velocity of dorsalis pedis artery in the preventive DPC group was significantly higher than that of the non-preventive DPC group (cm/s: 19.30±10.85 vs. 17.85±8.55, P < 0.05), and the peak velocity of posterior tibial artery was significantly lower than that of the non-preventive DPC group (cm/s: 19.90±10.94 vs. 21.58±9.77, P < 0.05). Pearson correlation analysis showed that the peak velocity of dorsalis pedis artery and peak velocity of posterior tibial artery of the preventive DPC group and the non-preventive DPC group were positively correlated with TcPO2 (r values were 0.747, 0.856, 0.850, 0.813, respectively, and P values were all 0.000). For patients with VA-ECMO treatment, the incidence of blood stream infection and bleeding during ECMO operation in non-prophylactic DPC implantation patients is lower than that of prophylactic DPC implantation patients. TcPO2 is positively correlated with peak velocity of posterior tibial artery and dorsal foot artery in the cannulated limb. In patients with VA-ECMO undergoing femoral artery and vein puncture,in addition to judging the blood supply of lower limbs according to symptoms and signs, ultrasound and TcPO2 monitoring can also be used as effective monitoring methods.

Transcutaneous blood gas monitoring among neonatal intensive care units in Japan.

This study aimed to investigate the utility of transcutaneous (tc) measurements of partial pressure of oxygen (tcPO2 ) and carbon dioxide (tcPCO2 ) monitoring in neonatal intensive care units (NICUs) in Japan. At the end of 2016,we sent a survey questionnaire on tc monitoring to all 106 NICUs registered with the Japanese Neonatologist Association. The questions included usage, subjects, methods, management, and the practical usefulness of tc monitoring. The questionnaire was returned by 69 NICUs (65.1% of response rate). Seventeen institutions (24.6%) measured both tcPCO2 and tcPO2 , and 42 (60.9%) measured tcPCO2 alone. Transcutaneous PCO2 or tcPO2 monitoring was applied for "pre-viable" infants born at 22-23weeks' gestational age (18.6% vs 23.5%), and infants of <500g birthweight (30.5% vs 17.6%). The tcPCO2 and tcPO2 monitoring was started at birth in 49.2% and 70.6% of the newborn infants, respectively. The temperature of the sensor was set at <38°C for tcPCO2 in 54.3% and >42°C for tcPO2 in 58.9% of NICUs. The accuracy for tcPO2 was rated as good in 35.3% or moderate in 64.7%, of institutions but or for tcPCO2 as 1.7% or 93.2%of institutions , respectively. Transcutaneous monitoring was widely, but limitedly, used for preterm infants. The lower temperature of the tcPCO2 sensor compared to that reported in other developed countries might compromise the accuracy but increase the feasibility of tc monitoring in Japan.

Novel transcutaneous sensor combining optical tcPO2 and electrochemical tcPCO2 monitoring with reflectance pulse oximetry.

This study investigated the accuracy, drift, and clinical usefulness of a new optical transcutaneous oxygen tension (tcPO2) measuring technique, combined with a conventional electrochemical transcutaneous carbon dioxide (tcPCO2) measurement and reflectance pulse oximetry in the novel transcutaneous OxiVenT™ Sensor. In vitro gas studies were performed to measure accuracy and drift of tcPO2 and tcPCO2. Clinical usefulness for tcPO2 and tcPCO2 monitoring was assessed in neonates. In healthy adult volunteers, measured oxygen saturation values (SpO2) were compared with arterially sampled oxygen saturation values (SaO2) during controlled hypoxemia. In vitro correlation and agreement with gas mixtures of tcPO2 (r = 0.999, bias 3.0 mm Hg, limits of agreement − 6.6 to 4.9 mm Hg) and tcPCO2 (r = 0.999, bias 0.8 mm Hg, limits of agreement − 0.7 to 2.2 mm Hg) were excellent. In vitro drift was negligible for tcPO2 (0.30 (0.63 SD) mm Hg/24 h) and highly acceptable for tcPCO2 (− 2.53 (1.04 SD) mm Hg/12 h). Clinical use in neonates showed good usability and feasibility. SpO2-SaO2 correlation (r = 0.979) and agreement (bias 0.13%, limits of agreement − 3.95 to 4.21%) in healthy adult volunteers were excellent. The investigated combined tcPO2, tcPCO2, and SpO2 sensor with a new oxygen fluorescence quenching technique is clinically usable and provides good overall accuracy and negligible tcPO2 drift. Accurate and low-drift tcPO2 monitoring offers improved measurement validity for long-term monitoring of blood and tissue oxygenation.Graphical abstract

Wearable, Luminescent Oxygen Sensor for Transcutaneous Oxygen Monitoring.

We present a new concept for a wearable oxygen (O2) sensor for transcutaneous O2 pressure (tcpO2) monitoring by combining the technologies of luminescent gas sensing and wearable devices. O2 monitoring has been exhaustively studied given its central role in diagnosing various diseases. The ability to quantify the physiological distribution and real-time dynamics of O2 from the subcellular to the macroscopic level is required to fully understand mechanisms associated with both normal physiological and pathological conditions. Despite its profound biological and clinical importance, few effective methods exist for noninvasively quantifying O2 in a physiological setting. The wearable sensor developed here consists of three components: a luminescent sensing film attached onto skin by a carbon tape, an organic light-emitting diode (OLED) as a light source, and an organic photodiode (OPD) as a light detector. All the components are solution-processable and integrated on a plane in a bandage-like configuration. To verify the performance, tcpO2 variations by pressure-induced occlusion were measured in the lower arm and a thumb by the wearable sensor, and the results were comparable to those measured by a commercial instrument. In addition to its flexibility, other features of this sensor render it a potential low-cost solution for the simultaneous monitoring of tcpO2 in any part of a body.

Assessment of cutaneous microcirculation in unaffected skin regions by transcutaneous oxygen saturation monitoring and Laser Doppler flowmetry in systemic sclerosis

We assessed the cutaneous microcirculatory reactivity of a clinically unaffected skin region in patients with systemic sclerosis (SSc) compared to healthy controls by measuring transcutaneous oxygen saturation (TcPO2) and Laser Doppler flowmetry (LDF).Twelve consecutive patients with SSc and twelve healthy controls were subjected to TcPO2 monitoring and LDF during cuff-induced ischemia and reactive hyperemia in order to measure the skin oxygen tension and the microcirculatory blood flow. Mean minimal and maximal values of oxygen tension and blood flow, time to peak (TTP), and declining slopes after peaking (slope) were compared between patients with SSc and controls.Compared to the controls, TcPO2 values in SSc were similar during ischemia and diminished during reactive hyperemia, with longer TTP, and a slower return to baseline (-60% vs. -58% , p = 1.000, +76% vs. +210% , p = 0.047, 137 s vs. 108 s, p = 0.028, -0.009% /s vs. -0.019% /s, p = 0.021, respectively). LDF values, however, did not differ significantly between patients with SSc and controls.Unaffected skin regions of SSc patients showed a significantly diminished postischemic vasodilatory reactivity when assessed by TcPO2 monitoring, but not by LDF, indicating that vasculopathy may represent an early mechanism in the onset of skin sclerosis. TcPO2 measurement may help to detect changes in the microcirculation in SSc with no skin affection.

Transcutaneous oxygen tension monitoring in critically ill patients receiving packed red blood cells

PurposeWhether transfusions of packed red blood cells (PRBCs) affect tissue oxygenation in stable critically ill patients is still matter of discussion. The microvascular capacity for tissue oxygenation can be determined noninvasively by measuring transcutaneous oxygen tension (tcpO2). The aim of this study was to assess tissue oxygenation by measuring tcpO2 in stable critically ill patients receiving PRBC transfusions. MethodsNineteen stable critically ill patients, who received 2 units of PRBC, were prospectively included into this pilot study. Transcutaneous oxygen tension was measured continuously during PRBC transfusions using Clark's electrodes. In addition, whole blood viscosity and global hemodynamics were determined. ResultsReliable measurement signals during continuous tcpO2 monitoring were observed in 17 of 19 included patients. Transcutaneous oxygen tension was related to the global oxygen consumption (r = −0.78; P = .003), the arterio-venous oxygen content difference (r = −0.65; P = .005), and the extraction rate (r = −0.71; P = .02). The transfusion-induced increase of the hemoglobin concentration was paralleled by an increase of the whole blood viscosity (P < .001). Microvascular tissue oxygenation by means of tcpO2 was not affected by PRBC transfusions (P = .46). Packed red blood cell transfusions resulted in an increase of global oxygen delivery (P = .02) and central venous oxygen saturation (P = .01), whereas oxygen consumption remained unchanged (P = .72). ConclusionsIn stable critically ill patients, microvascular tissue oxygenation can be continuously monitored by Clark's tcpO2 electrodes. According to continuous tcpO2 measurements, the microvascular tissue oxygenation is not affected by PRBC transfusions.

Transcutaneous oximetry monitoring in patients with type 2 diabetes mellitus and critical limb ischemia

Aims. To evaluate transcutaneous oximetry as a method for diagnostics and monitoring in patients with diabetes mellitus (DM) and critical limb ischemia (CLI) after percutaneous transluminal balloon angioplasty (PTBA). Materials and Methods. We enrolled 126 patients with DM and CLI for participation in this study (148 limbs in total). 22 patients underwent PTBA on both lower limbs, and 104 ? on single limb. Transcutaneous oximetry and duplex ultrasonography of lower limb arteries was performed prior to PTBA with subsequent examinations on 5-7th days, 1st, 3rd and 6th month after intervention. Transcu- taneous oxygen tension (TcpO2) was measured by Radiometer (Copenhagen) oximeter system. Duplex ultrasonography was performed on Voluson 730? Expert system (GE Medical Systems Kretztechnik GmbHCo OHG, Austria). Results. Multiple factor analysis suggests that results of TcpO2 monitoring prior to and after PTBA are influenced by presence of ischemic heart disease, severe lower limb infections, serum creatinine, arterial hypertension and lower limb reperfusion edema. We observed a strong correlation of TcpO2 with the degree of anterior tibial artery and dorsal pedis artery occlusion. Conclusion. Transcutaneous oximetry allows evaluation of CLI severity and efficiency of PTBA in the majority oа patients with DM and CLI. Certain comorbidities impose limitations on this technique. Efficiency of endovascular intervention should be evaluated based on complex non-invasive examination, clinical data and signs of CLI.

Quantitative analysis of hemodynamics of congested island flaps under leech therapy

A congested flap is a good indication for leech therapy. However, determining the appropriate number of leeches as well as the appropriate application time in clinical cases is difficult. We analyzed hemodynamics in rabbit island flaps under leech therapy to find a suitable clinical procedure for determining the appropriate number of leeches to be used and the duration of therapy. Island flaps were raised in 35 rabbit ears, and congestion was induced by venous clamping. Treatment involved use of 1 or 3 leeches and was begun 60 minutes after venous occlusion. Flaps were examined for area of surviving tissue, alterations in transcutaneous oxygen and carbon dioxide tension (TcPO2 and TcPCO2), and flow volume. Arteriole and venule diameters and flow velocities were examined microscopically. Flap survival area in the 3-leech therapy group was significantly larger than the 1-leech therapy group and the control group. With 3-leech therapy, TcPCO2 decreased significantly, as did arteriole and venule diameters. After clamp release, TcPCO2 and venule diameter continued to decrease in this group, and flow velocity increased significantly. Leech therapy may salvage compromised flaps by replacing congested blood with new arterial blood and thus maintaining flap viability. TcPO2 and TcPCO2 monitoring may help evaluate the therapeutic effect and determine the appropriate number of leeches to apply and the duration of therapy.

Providing stability in oxygenation for preterm infants: is transcutaneous oxygen monitoring really better than pulse oximetry?

Non-invasive monitoring of blood gases has become standard procedure in neonatal intensive care units (NICU).1 In particular, continuous monitoring of oxygenation is now considered indispensable to prevent retinopathy of prematurity...

Does the monitoring method influence stability of oxygenation in preterm infants? A randomised crossover study of saturation versus transcutaneous monitoring

Introduction:Hyperoxia and variable oxygenation are associated with morbidity in preterm infants. The optimal range of oxygen tensions is not known. This study aimed to determine whether care based on transcutaneous...

Evaluation of Bronchial Hyperresponsiveness by Monitoring of Transcutaneous Oxygen Tension and Arterial Oxygen Saturation during Methacholine Challenge in Asthmatic Children

Background. Bronchial hyperresponsiveness (BHR) is a key feature of asthma, but the measurement of BHR is hampered by the fact that most tests of airway caliber are difficult to conduct at a young age. Methacholine-induced bronchoconstriction is associated with significant hypoxemia, which can be assessed noninvasively by transcutaneous oxygen pressure (tcPO2) and pulse oximetry. Evaluating BHR by monitoring tcPO2 instead of respiratory resistance (Rrs) has been used over a wide age range in childhood.Objective. To investigate whether there is a consistent relationship between changes in arterial oxygen saturation (SaO2) and respiratory resistance (Rrs) similar to the relationship between tcPO2 and Rrs during methacholine challenge in young children and to assess the usefulness of SaO2 as a parameter for the indirect measurement of BHR.Method. We performed methacholine inhalation challenge by monitoring SaO2, tcPO2 and Rrs in 37 asthmatic children 5 to 7 years of age. Consecutive doses of methacholine were doubled until a 10% decrease in tcPO2 from the baseline was reached. We recorded the cumulative dose of methacholine (Dmin) at the inflection point of tcPO2 (Dmin-tcPO2), SaO2 (Dmin-SaO2), and Rrs(Dmin-Rrs).Results. The mean value of Dmin-Rrs was 4.27 ± 2.02 units, the mean value of Dmin-tcPO2 was 4.48 ± 2.01 units, and the mean value of Dmin-SaO2 was 4.57 ± 0.20 units. Inhalation of increasing doses of methacholine raised Rrs curvilinearly and depressed tcPO2 and SaO2. There were no significant differences between any of the parameters. There were significant relationships between Dmin-tcPO2 and Dmin-Rrs (r = 0.914, p < 0.001) and between Dmin-SaO2 and Dmin-Rrs (r = 0.905, p < 0.001) and a relationship between Dmin-tcPO2 and Dmin-SaO2 (r = 0.949, p < 0.001).Conclusion. We concluded that measurement of SaO2 and/or tcPO2 during methacholine inhalation challenge may be used to assess bronchial hyperresponsiveness. This study showed that both SaO2 and tcPO2 monitoring are safe, useful, and tolerable for use in children who are too young to cooperate with lung function tests.

Age-Related Changes in Microvascular Blood Flow and Transcutaneous Oxygen Tension Under Basal and Stimulated Conditions

Adequate cutaneous microvascular blood flow and tissue oxygen tension are important prerequisites for successful tissue repair. The efficacy of tissue repair decreases with age and is linked to the age-related functional decline of unmyelinated sensory neurons that are important for inflammation and tissue repair. However, available information on the effect of these neuronal changes on microvascular blood flow and tissue oxygen tension is limited, particularly under control and injury conditions. The authors had two aims in this study: (a) to assess age-related changes in the relationship between microvascular blood flow and tissue oxygen perfusion under basal and two different stimulated conditions (sensory dependent and sensory independent), and (b) to clarify the biological meaning of transcutaneous partial pressure of oxygen (tcPO2) measurements. The effects of a sensory-independent vasodilator (acetylcholine) and a sensory-dependent vasodilator (capsaicin) on microvascular blood flow and oxygen perfusion in persons of different ages were measured. Laser Doppler flowmetry and a commercially available transcutaneous oxygen monitor (with sensors set at 39 degrees C and 44 degrees C) were used. Healthy volunteers were recruited: 11 young, 14 middle aged, and 19 older. Under basal conditions (skin temperature, 37 degrees C to 39 degrees C), both basal blood flow and tcPO2 increased with increasing age. However, with the sensor set at 44 degrees C, tcPO2 showed a significant decrease with age. Acetylcholine increased blood flow approximately equally in the three age groups. Capsaicin increased blood flow and tcPO2 in all age groups, with the young showing a greater increase compared with the older participants. The age-associated changes in basal and stimulated microvascular blood flow and tcPO2 could be attributed in part to altered neuronal function. Measuring tcPO2 at 39 degrees C showed a trend toward an increase with age. In contrast, a decrease with age was observed when tcPO2 was measured at 44 degrees C, a temperature sufficient to activate sensory nerve endings. The results may reflect a decline in sensory nerve function with age rather than a decrease in oxygen delivery for vascular reasons. This is supported by the complementary data showing a significant age-related decrease in stimulated blood flow in response to capsaicin, with no change in the response to the sensory-independent vasodilator acetylcholine. Thus, for clinical purposes, data obtained using the tcPO2 monitor should be interpreted with full knowledge of the conditions under which the measurements were made. Furthermore, for scientific purposes, the tcPO2 monitor could be used to assess sensory nerve function when sensors are heated to 44 degrees C.

Historical Perspectives

This month’s Historical Perspective draws attention to the remarkable feat achieved by Renate and Albert Huch in the early 1970s, which seemed magical at the time. This was the development of an electrode that measured the partial pressure of oxygen at the skin surface (tcPo2), which reflected the oxygen tension in arterial blood. (1) Subsequently, continuous transcutaneous measurement demonstrated that intermittent arterial blood gas measurements provided only a glimpse of the dynamic variations that occur with different procedures in the neonatal intensive care unit (NICU). In addition, it was not long before the use of two electrodes demonstrated shunting through the ductus arteriosus. (2) Later in the same decade, this same team produced a complementary electrode to measure the partial pressure of carbon dioxide (tcPco2). (3) The measurement of both tcPo2 and tcPco2 allowed greatly improved management of assisted ventilation. There was one significant disadvantage of tcPo2 monitoring, which was the need to move the electrode every few hours to prevent skin injury from the heating device. As a result, when pulse oximetry became available, monitoring of oxygen saturation became more popular. However, as the Huchs point out, most pulse oximeters have a problem with movement artefact (although this may have been resolved with some devices), and they cannot detect hyperoxemia. Consequently, transcutaneous blood gas monitoring (particularly tcPco2) remains an important adjunct in the NICU, especially early in the course of respiratory disease. 1. ↵ Huch R, Huch A, Lubbers DW. Transcutaneous measurement of blood PO2 (tcPO2): method and applications in perinatal medicine. J Perinat Med. 1973;1:183–191 [OpenUrl][1][PubMed][2] 2. ↵ Yamanouchi I, Igarashi I. Ductal shunt in premature infants observed by tcPO2 measurements. In: Huch A, Huch R, Lucey JF, eds. Transcutaneous Blood Gas Monitoring. Birth Defects: Original Article Series. Vol. 15. New York, NY: AR Liss;1979 :323–340 3. ↵ Huch A, Huch R, Seiler D, Galster H, Meinzer K, Lubbers DW. Transcutaneous PCO2 measurement with a miniaturized electrode. Lancet. 1977;i:982–983 [OpenUrl][3] # Transcutaneous Po2 in Newborns: An Electrode in the Family {#article-title-2} When we met in the German university city of Gottingen in 1959, Albert was a medical student and Renate was still in high school. After qualifying, Albert studied respiratory physiology at the Max Planck Institute for Experimental Medicine in Gottingen while Renate completed her medical studies. We married in 1964 and moved some miles south to Marburg, another medieval university … [1]: {openurl}?query=rft.jtitle%253DJournal%2Bof%2Bperinatal%2Bmedicine%26rft.stitle%253DJ%2BPerinat%2BMed%26rft.aulast%253DHuch%26rft.auinit1%253DR.%26rft.volume%253D1%26rft.issue%253D3%26rft.spage%253D183%26rft.epage%253D191%26rft.atitle%253DTranscutaneous%2Bmeasurement%2Bof%2Bblood%2BPo2%2B%2528tcPo2%2529%2B--%2BMethod%2Band%2Bapplication%2Bin%2Bperinatal%2Bmedicine.%26rft_id%253Dinfo%253Apmid%252F4806572%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [2]: /lookup/external-ref?access_num=4806572&link_type=MED&atom=%2Fneoreviews%2F4%2F9%2Fe223.atom [3]: {openurl}?query=rft.jtitle%253DLancet.%26rft.volume%253D0%26rft.spage%253D982%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx

Childhood cough variant asthma and its relationship to classic asthma

In pediatrics, some patients with chronic cough who have no evidence of a causative disease are diagnosed as having cough variant asthma (CVA). The precise prognosis of infants and children with CVA, however, is still unclear. To evaluate the relationship between CVA and classic asthma in childhood. To diagnose CVA, we performed a methacholine inhalation challenge with use of a transcutaneous oxygen pressure (tcPO2) monitoring system in 100 children with chronic cough, and 75 children (45 boys and 30 girls; mean age, 5.7 years) were diagnosed as having CVA. These patients underwent follow-up monitoring for more than 3 years to ascertain whether classic asthma developed. For comparison, 53 age-matched children with classic asthma (30 boys and 23 girls; mean age, 5.6 years) and 30 age-matched control subjects (12 boys and 18 girls; mean age, 5.5 years) also participated in this study. Consecutive doses of methacholine were doubled until a 10% decrease in tcPO2 from the baseline was reached. The cumulative dose of methacholine at the inflection point of tcPO2 (Dmin-PO2) was considered to represent the sensitivity of tcPO2 to inhaled methacholine. After 3 years or more of follow-up assessments, 52 of the 75 patients answered our questionnaire. Of the responding patients, 28 had been diagnosed as having classic asthma. A significant difference was noted in the age at onset of CVA between the children in whom classic asthma developed (the asthma-developed group) and those in whom classic asthma did not develop (the asthma-free group). No statistically significant differences in Dmin-PO2 between the asthma-developed group and the asthma-free group or between the girls and the boys, however, were foun This study showed that 75% of children with chronic cough had CVA, that classic asthma developed in 54% of the children with CVA, and that it is not the severity of bronchial hyperresponsiveness in CVA but the age at onset of CVA that is a risk factor for the development of classic asthma in childhood CVA.

Effects of leg and body position on transcutaneous oxygen measurements in healthy subjects and subjects with peripheral artery disease after lower-extremity arterial revascularization: A pilot study

Transcutaneous oxygen (TcPO2) measurements provide a noninvasive, objective determination of the oxygen level at the skin surface. This offers a means of estimating the underlying circulation and tissue oxygenation. The purpose of the pilot study was to measure the TcPO2 value of the lower extremity of healthy men and women and of patients with peripheral arterial disease (PAD) in 4 different body and leg positions 24 hours after peripheral vascular surgery reconstruction. The specific aim was to determine if lower-extremity TcPO2 measurements were affected by changes in extremity position in these subject populations. A convenience sample of 4 healthy health care professionals and 4 patients who had peripheral vascular reconstruction surgery 24 hours before the measurements were studied. Subjects were studied in 4 different leg and body positions: supine with legs extended, sitting with legs dependent, a 5° head-up reverse Trendelenburg, and supine with legs elevated 10 in. The Radiometer TCM30 TcPO2 monitor was used to carry out these measures. Findings revealed a statistically significant difference in TcPO2 measurements between the 2 groups, with the healthy subjects having a significantly higher TcPO2 measurement in all extremity positions compared with the revascularized subjects with PAD (P =.02−.05). Significant changes were noted in both the foot temperature (P =.03) and TcPO2 measurements with extremity positions within the healthy subject group (P =.001). The foot and leg TcPO2 measurements affect from leg and body position did not reach significance (P =.09) in the subjects with PAD. No change in foot temperature with extremity positioning (P =.42) was noted in the subjects with PAD. This pilot study provides a base in which additional research will be performed with TcPO2 measurements in both the healthy and revascularized person. (J Vasc Nurs 2002;20:125-35)

Age-dependent relationship between bronchial hyperresponsiveness to methacholine and total serum IgE level in asthmatic children

A relationship between nonspecific bronchial hyperresponsiveness and allergic airway inflammation has been reported in children and in adults with asthma, but the relationship in infants with asthma is still unclear. To evaluate the relationship between bronchial hyperresponsiveness and total serum IgE level throughout childhood. Bronchial reactivity to methacholine from the age of 1 to 16 years was studied by methacholine inhalation challenge using transcutaneous oxygen pressure (tcPO2) monitoring. Two hundred one asthmatic children (boys:girls = 132:69; 7.3+/-4.0 years of age, mean +/- SD) were enrolled in this study. The tcPO2 was measured using a tcPO2 monitor. Serial doses of methacholine were doubled until a 10% decrease in tcPO2 from the baseline was reached. The cumulative dose of methacholine at the inflection point of tcPO2 was considered to represent the bronchial reactivity to methacholine. There was no relationship between the cumulative dose of methacholine at the inflection point of tcPO2 and total serum IgE level in the group of children aged 1 to 4 years (P = 0.212), but significant correlations were found in the groups aged 5 to 10 years and 11 to 16 years (P = 0.044 and P = 0.014, respectively). We conclude that there is an age-dependent relationship between bronchial reactivity to methacholine and the total serum IgE level and that inhaled allergens, which were more common allergens in older children, may have some effects on the degree of bronchial reactivity to methacholine in children with asthma.

Age-related changes in bronchial hyperreactivity to methacholine in asthmatic children.

To evaluate the influence of aging on bronchial hyperreactivity (BHR) during the childhood period, age-related changes in bronchial reactivity to methacholine (BRm) in children from 2 to 13 yr of age were studied using the same method, employing a methacholine inhalation challenge with transcutaneous oxygen pressure (tcPO2) monitoring. Three hundred and thirty-nine asthmatic subjects (male:female = 200:139, aged [mean +/- SEM] 7.2 +/- 0.2 yr) and 107 age-matched controls (male:female = 55:52, aged 5.3 +/- 0.3 yr) were enrolled in this study. TcPO2 was measured by a tcPO2 monitor, and subsequent doses of methacholine were then doubled until a 10% decrease in tcPO2 from its baseline value was reached. The cumulative dose of methacholine at the inflection point of tcPO2 (Dmin-PO2) was considered to represent the BRm. For the sake of comparison, respiratory resistance (Rr) in subjects more than 6 yr old was measured by the oscillation technique during methacholine inhalation challenge, and the threshold point of Rr (Dmin-Rr) was also considered to represent the BRm. In the asthmatic children aged 2 to 7 yr, Dmin-PO2 decreased significantly from 12.2 +/- 2.1 to 3.1 +/- 0.8 units, but after age 8 yr the values gradually increased from 3.1 +/- 0.7 to 6.4 +/- 1.6 units. In children aged 6 to 13 yr, Dmin-Rr showed the same increase as Dmin-PO2, from 2.0 +/- 0.5 to 5.8 +/- 1.4 units. These age-related changes in BRm reflected in both Dmin-PO2 and Dmin-Rr were also seen in the age-matched controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of Dose-Response Slopes Obtained by Simultaneous Assessment of Changes in FEV1and Transcutaneous Oxygen Partial Pressure During Methacholine Challenges in Asthmatic Patients

We aimed to ascertain whether monitoring changes in transcutaneous (tc) oxygen partial pressure (PO2) may be used to determine the slope of the dose-response curves to inhaled methacholine. In 10 adult asthmatic patients, FEV1 and tcPO2 were simultaneously measured during inhalation of doubling methacholine concentrations. In each patient, the slopes of the methacholine dose-response curves for FEV1 and tcPO2 were similar and strongly correlated (r = 0.72; p < 0.05). The results indicate that tcPO2 monitoring represents a useful, reliable tool for analysis of the slope of dose-response curves to inhaled methacholine in asthmatic patients. It can also be used to investigate the pathophysiological implications of bronchial hyperreactivity.

Changes in Transcutaneous Oxygen Partial Pressure as an Index of Response to Inhaled Methacholine in Asthmatic Patients

Bronchoconstriction and hypoxemia have been reported to occur during airway challenges, but the correlation between changes in forced expiratory volume in 1 s (FEV1) and transcutaneous oxygen partial pressure (tcPO2) during methacholine provocation tests has not yet been established (to our knowledge). In 15 symptom-free atopic asthmatic patients and 5 normal subjects, variations in tcPO2 and FEV1 were simultaneously measured during inhalation of doubling methacholine concentrations; the drug concentrations causing a 20 percent decrease in control FEV1 and tcPO2 (PC20FEV1 and PC20tcPO2, respectively) were subsequently calculated. In patients, geometric mean PC20FEV1 and PC20TcPO2 were 1.31 (range, 0.16 to 5.19) and 1.26 (range, 0.29 to 5.82) mg/ml, respectively. In addition, in six patients, methacholine-induced fall in tcPO2 was accompanied by similar changes in arterial PO2. Methacholine inhalation caused no change in tcPO2 or FEV1 in normal subjects. The independent effects of deep breath tests and bronchoconstriction on PC20tcPO2 were studied in five patients challenged on two separate occasions, with and without FEV1 assessment; in these patients, PC20tcPO2 were similar on both the study days. The results indicate that, in asthmatic patients, methacholine-induced bronchoconstriction causes parallel decreases in FEV1 and tcPO2. The tcPO2 monitoring may serve as a tool in the assessment of airway hyperreactivity when active patient's cooperation is scarce.

A cohort study of transcutaneous oxygen tension and the incidence and severity of retinopathy of prematurity.

Retinopathy of prematurity is a disease affecting the blood vessels of the retina in premature infants that may result in scarring, retinal detachment, and loss of vision. An association between this condition and the exposure of premature infants to supplemental oxygen has been postulated, but the relation between retinopathy of prematurity and blood oxygen levels has not been defined. The purpose of this study of a cohort of preterm infants was to correlate the incidence and severity of retinopathy of prematurity with the duration of exposure to different ranges of oxygen tension as measured by transcutaneous monitoring (tcPO2). One hundred one premature infants (birth weight, 500 to 1300 g) requiring supplemental oxygen had continuous monitoring of tcPO2. The number of hours during which the tcPO2 was 80 mm Hg or higher was tabulated for each infant during the first four weeks of life. There was a significant association between the amount of time that the tcPO2 was greater than or equal to 80 mm Hg and the incidence and severity of retinopathy of prematurity. The odds ratio for each 12-hour period in which the tcPO2 was greater than or equal to 80 mm Hg was 1.9 (95 percent confidence interval, 1.2 to 3.0) after adjustment for the following factors: birth weight less than or equal to 1300 g (odds ratio, 2.3 [95 percent confidence interval, 1.6 to 3.4]), five-minute Apgar score of 7 or less (odds ratio, 7.2 [95 percent confidence interval, 2.5 to 21]), and exposure to inspired oxygen at a concentration greater than or equal to 0.4 (odds ratio, 1.0 [95 percent confidence interval, 0.97 to 1.05]). The association was stronger for tcPO2 values of greater than or equal to 80 mm Hg occurring from the second through the fourth week of life; during this period, the adjusted odds ratio for a 12-hour period of such exposure was 3.1 (95 percent confidence interval, 1.6 to 6.1). This study supports an association between the incidence and severity of retinopathy of prematurity and the duration of exposure to arterial oxygen levels of 80 mm Hg or higher, measured transcutaneously.