PtcO2 Values Research Articles

Comparison between PtCO2 and PaCO2 and Derived Parameters in Heart Failure Patients during Exercise: A Preliminary Study.

Evaluation of arterial carbon dioxide pressure (PaCO2) and dead space to tidal volume ratio (VD/VT) during exercise is important for the identification of exercise limitation causes in heart failure (HF). However, repeated sampling of arterial or arterialized ear lobe capillary blood may be clumsy. The aim of our study was to estimate PaCO2 by means of a non-invasive technique, transcutaneous PCO2 (PtCO2), and to verify the correlation between PtCO2 and PaCO2 and between their derived parameters, such as VD/VT, during exercise in HF patients. 29 cardiopulmonary exercise tests (CPET) performed on a bike with a ramp protocol aimed at achieving maximal effort in ≈10 min were analyzed. PaCO2 and PtCO2 values were collected at rest and every 2 min during active pedaling. The uncertainty of PCO2 and VD/VT measurements were determined by analyzing the error between the two methods. The accuracy of PtCO2 measurements vs. PaCO2 decreases towards the end of exercise. Therefore, a correction to PtCO2 that keeps into account the time of the measurement was implemented with a multiple regression model. PtCO2 and VD/VT changes at 6, 8 and 10 min vs. 2 min data were evaluated before and after PtCO2 correction. PtCO2 overestimates PaCO2 for high timestamps (median error 2.45, IQR −0.635–5.405, at 10 min vs. 2 min, p-value = 0.011), while the error is negligible after correction (median error 0.50, IQR = −2.21–3.19, p-value > 0.05). The correction allows removing differences also in PCO2 and VD/VT changes. In HF patients PtCO2 is a reliable PaCO2 estimation at rest and at low exercise intensity. At high exercise intensity the overall response appears delayed but reproducible and the error can be overcome by mathematical modeling allowing an accurate estimation by PtCO2 of PaCO2 and VD/VT.

End‐tidal CO2 and transcutaneous CO2: Are we ready to replace arterial CO2 in awake children?

AbstractIntroductionArterial blood gas analysis (ABG) is the gold standard test for carbon dioxide measurement. End‐tidal PCO2 (PetCO2) and transcutaneous PCO2 (PtcCO2) are noninvasive alternative methods.ObjectiveTo examine the use of PetCO2 and PtcCO2 as PaCO2 surrogates in awake children.MethodsA prospective observational study. Consecutive awake children in a stable condition referred to the Sleep Unit of Hospital de Pediatría Dr. J. P. Garrahan with suspected or confirmed sleep‐related respiratory disorders requiring ABG were included. PetCO2 and PtcCO2 were recorded simultaneously during arterial puncture. PetCO2 and PtCO2 values were compared with PaCO2. Correlation coefficient and Bland–Altman analysis were applied. The sample size was calculated considering a mean difference ≤3 mmHg as clinically acceptable.ResultsSixty‐eight sample sets were obtained from 67 patients. The median age was 9.11 years (0.23–18.76). During 94.1% of the procedures patients breathed spontaneously, 30% needed multiple punctures and 92% resulted in pain. Median (IQR) PaCO2 (mmHg) was 36.3 (31.45; 40.90), PetCO2 33.0 (29; 39) and PtcCO2 38.8 (32.95; 43.32). Correlation and agreement for PaCO2/PetCO2 and PaCO2/PtcCO2 was r = .6 and .9, and media of bias = 2.83 (−9.97; 15.64) and −1.88 (−9.01; 5.24), respectively. Hypercapnia (PaCO2 > 45.0 mmHg) was present in 8/68 (11.8%) samples. Sensitivity, specificity, positive predictive value and negative predictive value to detect hypercapnia with PetCO2 was 38%, 98%, 75%, and 92%, respectively, and with PtcCO2, 100%, 90%, 57%, and 100%, respectively.ConclusionPtcCO2 showed better agreement with PaCO2 than PetCO2 but because of the wide dispersion of values, neither method can replace the gold standard. Transcutaneous CO2 might be a good screening tool to detect hypercapnia in awake children.

The effect of 50% oxygen on PtCO2 in patients with stable COPD, bronchiectasis, and neuromuscular disease or kyphoscoliosis: randomised cross-over trials

BackgroundHigh-concentration oxygen therapy causes increased arterial partial pressure of carbon dioxide (PaCO2) in patients with COPD, asthma, pneumonia, obesity and acute lung injury. The objective of these studies was to investigate whether this physiological response to oxygen therapy occurs in stable patients with neuromuscular disease or kyphoscoliosis, and bronchiectasis.MethodsThree randomised cross-over trials recruited stable patients with neuromuscular disease or kyphoscoliosis (n = 20), bronchiectasis (n = 24), and COPD (n = 24). Participants were randomised to receive 50% oxygen and 21% oxygen (air), each for 30 min, in randomly assigned order. The primary outcome was transcutaneous partial pressure of carbon dioxide (PtCO2) at 30 min. The primary analysis was a mixed linear model.ResultsSixty six of the 68 participants had baseline PtCO2 values < 45 mmHg. The intervention baseline adjusted PtCO2 difference (95% CI) between oxygen and room air after 30 min was 0.2 mmHg (− 0.4 to 0.9), P = 0.40; 0.5 mmHg (− 0.2 to 1.2), P = 0.18; and 1.3 mmHg (0.7 to 1.8), P < 0.001, in the neuromuscular/kyphoscoliosis, bronchiectasis and COPD participants respectively.ConclusionsThe small increase in PtCO2 in the stable COPD patients with high-concentration oxygen therapy contrasts with the marked increases in PaCO2 seen in the setting of acute exacerbations of COPD. This suggests that the model of studying the effects of high-concentration oxygen therapy in patients with stable respiratory disease is not generalisable to the use of oxygen therapy in the acute clinical setting. Appropriate studies of high-concentration compared to titrated oxygen in acute clinical settings are needed to determine if there is a risk of oxygen-induced hypercapnia in patients with neuromuscular disease, kyphoscoliosis or bronchiectasis.Trial registrationAustralian New Zealand Clinical Trials Registry ACTRN12615000970549 Registered 16/9/15, ACTRN12615000971538 Registered 16/9/15 and ACTRN12615001056583 Registered 7/10/15.

Comparison of tissue oxygenation achieved breathing oxygen from a demand valve with four different mask configurations.

High concentration normobaric oxygen (O₂) is a priority in treating divers with suspected decompression illness. The effect of different O₂ mask configurations on tissue oxygenation when breathing with a demand valve was evaluated. Sixteen divers had tissue oxygen partial pressure (PtcO₂) measured at six limb sites. Participants breathed O₂ from a demand valve using: an intraoral mask (IOM®) with and without a nose clip (NC), a pocket face mask and an oronasal mask. In-line inspired O₂ (FIO₂) and nasopharyngeal FIO₂ were measured. Participants provided subjective ratings of mask comfort, ease of breathing and holding in position. PtcO₂ values and nasopharyngeal FIO₂ (median and range) were greatest using the IOM with NC and similar with the IOM without NC. O₂ measurements were lowest with the oronasal mask which also was rated as the most difficult to breathe from and to hold in position. The pocket face mask was reported as the most comfortable to wear. The NC was widely described as uncomfortable. The IOM and pocket face mask were rated best for ease of breathing. The IOM was rated as the easiest to hold in position. Of the commonly available O₂ masks for use with a demand valve, the IOM with NC achieved the highest PtcO₂ values. PtcO₂ and nasopharyngeal FIO₂ values were similar between the IOM with and without NC. Given the reported discomfort of the NC, the IOM without NC may be the best option.

Effect of Transcutaneous Electrode Temperature on Accuracy and Precision of Carbon Dioxide and Oxygen Measurements in the Preterm Infants.

High electrode temperature during transcutaneous monitoring is associated with skin burns in extremely premature infants. We evaluated the accuracy and precision of CO2 and O2 measurements using lower transcutaneous electrode temperatures below 42°C. We enrolled 20 neonates. Two transcutaneous monitors were placed simultaneously on each neonate, with one electrode maintained at 42°C and the other randomized to temperatures of 38, 39, 40, 41, and 42°C. Arterial blood was collected twice at each temperature. At the time of arterial blood sampling, values for transcutaneously measured partial pressure of CO2 (PtcCO2 ) were not significantly different among test temperatures. There was no evidence of skin burning at any temperature. For PtcCO2 , Bland-Altman analyses of all test temperatures versus 42°C showed good precision and low bias. Transcutaneously measured partial pressure of O2 (PtcO2 ) values trended arterial values but had large negative bias. Transcutaneous electrode temperatures as low as 38°C allow an assessment of PtcCO2 as accurate as that with electrodes at 42°C.

Transcutaneous oximetry: variability in normal values for the upper and lower limb.

Published normal transcutaneous oxygen partial pressures (PtcO2) for the chest and lower limb have defined tissue hypoxia as a value of < 40 mmHg (< 30 mmHg in some patients, < 50 mmHg in others). To determine 'normal' PtcO2 for the upper and lower limb in healthy, non-smoking adults using the Radiometer® TCM400 with tc Sensor E5250. Thirty-two volunteers had transcutaneous oxygen measurements (TCOM) performed on the chest, upper and lower limbs breathing air, with leg then arm elevated and whilst breathing 100% oxygen. Room-air PtcO2 (mmHg, mean (95% confidence interval)) were: chest: 53.6 (48.7-58.5); upper arm: 60.0 (56.1-64.0); forearm: 52.3 (44.8-55.8); dorsum of hand: 50.2 (46.1-54.3); thenar eminence: 70.8 (67.7-73.8); hypothenar eminence: 77.9 (75.1-80.7); lateral leg: 50.2 (46.2-54.2); lateral malleolus: 50.5 (46.6-54.3); medial malleolus: 48.9 (45.6-52.1); dorsum, between first and second toe: 53.1 (49.2-57.0); dorsum, proximal to fifth toe: 58.5 (55.0 - -62.0); plantar, 1st MTP: 73.7 (70.3-77.1). Nineteen subjects had at least one room-air PtcO2 below 40 mmHg (nine upper limb, 13 lower limb, four chest). Approximately 10% lower limb PtcO2 were < 100 mmHg on normobaric oxygen. Only one subject at one site had an upper limb PtcO2 < 100 mmHg breathing oxygen. The broad dispersion in PtcO2 in our healthy cohort reflects the inherent biologic variability in dermal perfusion and oxygen delivery, making it difficult to define narrow, rigid 'normal' values. Thus, we cannot recommend a single PtcO2 value as 'normal' for the upper or lower limb. A thorough patient assessment is essential to establish appropriateness for hyperbaric oxygen therapy, with TCOM used as an aid to guide this decision and not as an absolute.

Erratum: Concordance and limits between transcutaneous and arterial carbon dioxide pressure in emergency department patients with acute respiratory failure: a single-center, prospective, and observational study.

After publication of this article (Scand J Trauma Resusc Emerg Med 23:40, 2015), it came to light that an earlier version had been published in error. This erratum contains the correct version of the article, which incorporates revisions made in response to reviewer comments. Additionally, one of the authors was inadvertently omitted from the author list. This author, Justin Yan, has been included in the corrected author list above.BackgroundTranscutaneous CO2 (PtCO2) is a continuous and non-invasive measure recommended by scientific societies in the management of respiratory distress. The objective of this study was to evaluate the correlation between PtCO2 and arterial partial pressure of CO2 (PaCO2) by arterial blood gas analysis in emergency patients with dyspnoea, and to determine the factors that interfere with this correlation.MethodsFrom January to June 2014, all adult patients admitted to the RR with dyspnoea during business hours were included in the study if arterial blood gas measurements were indicated. A sensor measuring the PtCO2 was attached to the ear lobe of the patient before the gas analysis. Anamnesis, clinical and laboratory parameters were identified.ResultsNinety patients with dyspnoea were included (104 pairs of measurements). The median (IQR) age was 79 years (69 – 85). The correlation between PtCO2 and PaCO2 was R2 =.83 (p<.001) but became lower for values of PaCO2 above 60 mm Hg. The mean bias (± SD) between the two methods of measurement (Bland-Altman analysis) was −1.4 mm Hg (± 7.7) with limits of agreement from −16.4 to 13.7 mm Hg. In univariate analysis, PaO2 interfered with this correlation. After multivariate analysis, temperature (OR = 3.01; 95 % CIs [1.16, 7.80]) and PaO2 (OR = 1.22; 95 % CIs [1.02, 1.47]) significantly interfered with this correlation.ConclusionsThere is a significant correlation between PaCO2 and PtCO2 values for patients admitted to the emergency department for acute respiratory failure. One limiting factor to routine use of PtCO2 measurements in the emergency department is the presence of hyperthermia.

Concordance and limits between transcutaneous and arterial carbon dioxide pressure in emergency department patients with acute respiratory failure: a single-center prospective observational study.

IntroductionTranscutaneous CO 2 (PtCO 2) is a continuous and non-invasive measure recommended by scientific societies in the management of respiratory distress. The objective of this study is to evaluate the correlation between PtCO 2 and blood pressure of CO 2 (PaCO 2) by blood gas analysis in emergency patients with dyspnoea and to determine the factors that interfere in this correlation.MethodsFrom January to June 2014, all patients admitted to resuscitation room of the emergency department targeted for arterial blood gases were included prospectively. A sensor measuring the PtCO 2 was attached to the ear lobe of the patient before the gas analysis. Anamnesis, clinical and laboratory parameters were identified.Results90 patients with dyspnoea were included (with 104 pairs of measurements), the median age was 79 years [69-85]. The correlation between PtCO 2 and PaCO 2 was R 2= 0.83 (p <0.001) but became lower for values of PaCO 2>60 mm Hg. The mean bias (±SD) between the two methods of measurement (Bland-Altman analysis) was -1.4 mm Hg (±7.7) with limits of agreement of -16.4 to 13.7 mm Hg. In univariate analysis, PaO 2 interfered in this correlation. After multivariate analysis, the temperature (OR = 3.01, 95% CI = 1.16-7.09) and the PaO 2 (OR = 1.22, 95% CI = 1.02-1.47) were found to be significant.ConclusionsIn patients admitted in emergency unit for acute respiratory failure, there is a significant correlation between PaCO 2 and PtCO 2, mainly for values below 60 mm Hg. The two limiting factors of use are hyperthermia and users training.

Agreement of Mixed Venous Carbon Dioxide Tension (PvCO2) and Transcutaneous Carbon Dioxide (PtCO2) Measurements in Ventilated Infants.

Background:Noninvasive transcutaneous carbon dioxide monitoring has been shown to be accurate in infants and children, limited data are available to show the usefulness and limitations of partial transcutaneous carbon dioxide tension (PtCO2) value.Objectives:The current study prospectively determines the effectiveness and accuracy of PtCO2 measurements in newborns.Materials and Methods:Venous blood gas sampling and monitoring of the PtCO2 level (TCM TOSCA, Radiometer) were done simultaneously. All measurements are performed on mechanically ventilated infants. Partial venous carbon dioxide tension (PvCO2) values divided into three groups according to hypocapnia (Group 1: < 4.68 kPa), normocapnia (Group 2: 4.68–7.33 kPa), hypercapnia (Group 3: > 7.33 kPa) and then PvCO2 and PtCO2 data within each group were compared separately.Results:A total of 168 measurements of each PvCO2 and PtCO2 data were compared in three separated groups simultaneously (13 in Group 1, 118 in Group 2, and 37 in Group 3). A bias of more than ± 0.7 kPa was considered unacceptable. PtCO2 was related to PvCO2 with acceptable results between the two measurements in hypocapnia (mean difference 0.20 ± 0.19 kPa) and normocapnia (0.002 ± 0.30 kPa) groups. On the other hand in hypercapnia group PtCO2 values were statistically significant (P < 0.001) and lower than PvCO2 data (mean difference 0.81 ± 1.19 kPa)Conclusions:PtCO2 measurements have generally good agreement with PvCO2 in hypocapnic and normocapnic intubated infants but there are some limitations especially with high level of CO2 tension. Monitoring of PtCO2 is generally a useful non-invasive indicator of PvCO2 in hypocapnic and normocapnic infants.

Evaluation of peripheral microcirculation improvement of foot after tarsal tunnel release in diabetic patients by transcutaneous oximetry.

According to recent studies, peripheral nerve decompression in diabetic patients seems to not only improve nerve function, but also to increase microcirculation; thus decreasing the incidence of diabetic foot wounds and amputations. However, while the postoperative improvement of nerve function is demonstrated, the changes in peripheral microcirculation have not been demonstrated yet. The aim of this study is to assess the degree of microcirculation improvement of foot after the tarsal tunnel release in the diabetic patients by using transcutaneous oximetry. Twenty diabetic male patients aged between 43 and 72 years old (mean age 61.2 years old) suffering from diabetic peripheral neuropathy with superimposed nerve compression underwent transcutaneous oximetry (PtcO2) before and after tarsal tunnel release by placing an electrode on the skin at the level of the dorsum of the foot. Eight lower extremities presented diabetic foot wound preoperatively. Thirty-six lower extremities underwent surgical release of the tibialis posterior nerve only, whereas four lower extremities underwent the combined release of common peroneal nerve, anterior tibialis nerve, and posterior tibialis nerve. Preoperative values of transcutaneous oximetry were below the critical threshold, that is, lower than 40 mmHg (29.1 ± 5.4 mmHg). PtcO2 values at one month after surgery (45.8 ± 6.4 mmHg) were significantly higher than the preoperative ones (P = 0.01). The results of postoperative increase in PtcO2 values demonstrate that the release of the tarsal tunnel determines a relevant increase in microcirculation in the feet of diabetic patients.

Determinants of Transcutaneous Ear Lobe CO2 Tension (PtCO2) at 37°C During On-Pump Cardiac Surgery.

There are no available criteria for determining the optimal flow rate and mean arterial pressure level in patients undergoing cardiopulmonary bypass (CPB). Transcutaneous carbon dioxide tension (PtCO2) has been proposed for microcirculation monitoring and it could be useful for guiding hemodynamic optimization under CPB. The goal of this exploratory study was to determine the factors that influence PtCO2 variations during CPB. Cutaneous ear lobe CO2 tension was monitored along with hemodynamic parameters every 10 minutes during CPB, until aortic unclamping. French university teaching hospital. Patients scheduled for cardiac surgery requiring CPB were prospectively included. None. A total of 41 patients were included (520 observations). There was a statistically significant association between PaCO2 and PtCO2 (beta = 0.493 [0.154-0.832], p = 0.043), mostly when PaCO2 was outside the normal range. When PaCO2 was normal, PtCO2 was inversely correlated with mean arterial pressure (after adjustment for PaCO2 and body temperature: Beta -0.245, SE = 0.037, p<0.001) but not with CPB flow rate (p = 0.11). The factors that influence PtCO2 during CPB cardiac surgery are PaCO2, body temperature, and mean arterial pressure. When PaCO2 is normal, a PtCO2 elevation might be explained by insufficient mean arterial pressure. Whether low PtCO2 values during CPB should trigger the administration of vasoconstrictors remains to be evaluated.

Evaluation of a transcutaneous blood gas monitoring system in critically ill dogs

To describe the use of a transcutaneous blood gas monitoring system in critically ill dogs, determine if transcutaneous and arterial blood gas values have good agreement, and verify if clinical or laboratory variables are correlated with differences between transcutaneous and arterial blood gas measurements. Prospective observational study. University teaching hospital ICU. Twenty-three client-owned dogs. In critically ill dogs undergoing arterial blood gas monitoring, a transcutaneous blood gas monitor was used to measure transcutaneous partial pressure of carbon dioxide (PtcCO2 ) and transcutaneous partial pressure of oxygen (PtcO2 ) values 30 minutes after sensor placement, which were compared to PaCO2 and PaO2 values measured simultaneously. Clinical and laboratory variables were concurrently recorded to determine if they were correlated with the difference between transcutaneous and arterial blood gas measurements. Bland-Altman analysis revealed a mean bias of 4.6 ± 26.3 mm Hg (limits of agreement [LOA]: -46.9/+56.1 mm Hg) between PtcO2 and PaO2 and a mean bias of 9.3 ± 8.5 mm Hg (LOA: -7.5/+26.0 mm Hg) between PtcCO2 and PaCO2 . The difference between PtcCO2 -PaCO2 was strongly negatively correlated with HCO3 (-) (r(2) = 0.52, P < 0.001) and PaCO2 (r(2) = 0.58, P < 0.001) and weakly positively correlated with diastolic blood pressure (r(2) = 0.21, P = 0.044), whereas the difference between PtcCO2 -PaCO2 was moderately negatively correlated with diastolic blood pressure (r(2) = 0.33, P = 0.008). Agreement between transcutaneous and arterial PO2 and PCO2 measurements in these critically ill dogs was inferior to that reported in similar adult and pediatric human studies. The transcutaneous monitor consistently over-estimated PaO2 and PaCO2 and should not be used to replace arterial blood gas measurements in critically ill dogs requiring blood gas interpretation.

Oxygen Challenge Test in Septic Shock Patients

Transcutaneous oxygen pressure (PtcO2) value in response to an increase of FiO2 or oxygen challenge test (OCT) in ventilated patients has been reported to be related to peripheral perfusion and outcome during septic shock. However, patients with sepsis-related acute respiratory distress syndrome could demonstrate compromised arterial oxygenation with OCT impairment decoupled to circulatory failure. The aims of this study were to confirm the prognostic value of OCT and to explore the influence of respiratory status on OCT results. This was a prospective study set in an intensive care unit of a tertiary teaching hospital. Fifty-six mechanically ventilated patients with septic shock criteria were studied. Transcutaneous oxygen pressure was measured at baseline and after OCT, at intensive care unit admittance (T0), and 24 h later (T24). Survival at day 28 and hemodynamic and respiratory parameters were analyzed and compared according to outcome and respiratory status. Central hemodynamic parameters or static transcutaneous data did not differ between survivors and nonsurvivors at enrollment. The OCT was statistically different at T24 according to outcome (P < 0.001), but sensitivity was low (53%). Moreover, patients with low OCT results at T24 exhibited more severe respiratory failure (P < 0.01). The OCT at T24 is related to outcome but is influenced by the severity of respiratory failure. Our results suggest considering with caution hemodynamic management based on OCT in septic shock patients with altered pulmonary function.

Plasma nitrite concentrations decrease after hyperoxia-induced oxidative stress in healthy humans

The aim of this study was to measure plasma nitrite, the biochemical marker of endothelial nitric oxide (  NO) synthesis, before and after hyperoxia, in order to test the hypothesis that hyperoxia-induced vasoconstriction is a consequence of reduced bioavailability of  NO caused by elevated oxidative stress. Ten healthy men breathed 100% normobaric O2 for 30 min between 15th and 45th min of the 1-h study protocol. Plasma nitrite and malondialdehyde (MDA), arterial stiffness (indicated by augmentation index, AIx) and arterial oxygen (PtcO2) pressure were measured at 1st, 15th, 45th and 60th minute of the study. Breathing of normobaric 100% oxygen during 30 min caused an increase in PtcO2 (from 75 ± 2 to 412 ± 25 mm Hg), AIx (from � 63 ± 4t o� 51 ± 3%) and MDA (from 152 ± 13 to 218 ± 15 nM) values and a decrease in plasma nitrite (from 918 ± 58 to 773 ± 55 nM). During the 15-min recovery phase, plasma nitrite, AIx and MDA values remained altered. This study suggests that the underlying mechanism of hyperoxia-induced vasoconstriction may involve reduced  NO

Evaluation of hyperbaric oxygen therapy for free flaps using planar optical oxygen sensors. Preliminary results

This study was designed to determine if a) hyperbaric oxygen increases the tissue oxygenation of free flaps and b) verification of this effect is possible by using a recently validated and innovative method for two-dimensional pO₂ measurement (Luminescence lifetime imaging = LLI). Six patients with a free parascapular flap transplanted to the lower limb received hyperbaric oxygen (HBOT) therapy. The HBOT regimen consisted of treatment over 90 minutes with 100% O₂ (FiO₂ 1.0) at 240 kPa (Marx-Schema). The transcutaneous oxygen partial pressure (ptcO₂) was measured over the entire flap with the use of luminescence lifetime imaging (LLI) before and 30, 60, 120 minutes after treatment. The LLI is based on the oxygen dependent quenching of phosphorescence of the indicator dye platinum (II)-octaethyl-porphyrin implemented in a polystyrene sensor foil. In all six free flaps we could find a significant increase of tissue oxygen over the entire flap in form of increased R-values as well as subsequently calculated absolute ptcO₂ values over a period of 120 min after hyperbaric therapy. The ptcO₂ values increased significantly from 42.59 ± 1.11 Torr before to 81.14 ± 5.95 Torr after hyperbaric treatment (p < 0.001). Even after 2 hours the ptcO₂ values were significantly higher (83.45 ± 13.80 Torr) compared with values prior to HBOT (p < 0.006). The findings of this study demonstrated an increase of oxygen supply over the entire flap after hyperbaric oxygen therapy.

Postoperative assessment of free skin flap viability by transcutaneous pO2 measurement using dynamic phosphorescence imaging

Free flap transplantation is used more and more frequently in order to cover extensive wound defects. The basic prerequisite for successful flap salvage after flap failure is a short time interval from failure until revision. For this reason many different flap monitoring systems have been tested over the last years. But none of them has made the way into clinical routine. The aim of this clinical study was to study whether luminescence lifetime imaging (LLI) is an adequate method to assess flap viability during the postoperative period. In previous experiments LLI was proven to be a precise and non-invasive monitoring system for transcutaneous oxygen measurement. ptcO2 of 9 patients was detected during a postoperative period of 72 hours. In all cases the transplantation was performed by the same experienced surgeon. During the first 4 hours almost constant ptcO2 values were detected (53±0.7 mmHg). During the following time intervals ptcO2 values decreased and reached a more or less constant level after approximately 12 hours. The mean ptcO2 decreased from 53±0.7 mmHg to 39±1.0 mmHg. In one case an immediate decrease of ptcO2 below 10 mmHg was observed and a subsequently intervention was necessary to improve flap perfusion. In this clinical trial, perfusion dynamics after free flap transplantation as well as the detection of vascular complications were demonstrated using LLI. Based on these data, LLI seems to be a sensitive and adequate monitoring system for the evaluation of free flap viability.

Using Transcutaneous Oxygen Pressure Measurements as Selection Criteria for Activated Protein C Use

Limited resources and the expense of Activated Protein C (APC) (drotrecogin alfa) may contribute to the reluctance to utilize this drug in sepsis. Employing the PROWESS criteria resulted in absolute reduction in 28-day mortality of 6.1%, representing a relative risk reduction of 19.4%. Additional patient categorization and selection may lead to less frequent drug use with the same survival advantage. We used transcutaneous partial pressure of oxygen (PtcO2) as an indicator of microcirculatory perfusion to identify which septic patients may benefit from APC. Nineteen patients consecutively admitted with severe sepsis or septic shock that fulfilled the PROWESS criteria for APC treatment. APC was administered to patients with the PROWESS selection criteria, only if the PtcO2 information demonstrated tissue ischemia. Nineteen patients met the PROWESS criteria. Ten patients demonstrated poor tissue perfusion using PtcO2 monitors and received APC. Nine patients had adequate tissue perfusion and did not receive APC. There were no differences in age, gender, APACHE II scores, lactate levels, or organ failure between the two groups. The 10 patients who received APC had a mortality of 3 of 10 (30%). The survivors of this group uniformly converted to PtcO2 values consistent with survival within 12 hours to 24 hours of drug administration. The nine patients who did not receive APC had a mortality of 2 of 9 (22%), not statistically significant from those who received the drug (p = 0.89). Withholding APC did not result in an increase in mortality from severe sepsis in those patients who demonstrated adequate PtcO2 values. The transcutaneous oxygen measurement may be a useful adjuvant in addition to the other selection criteria for better identification of patients who may benefit from APC.

TRANSCUTANEOUS PRESSURE OF OXYGEN

A noninvasive tool to recognize early shock would improve outcome by providing prompt recognition of tissue ischemia and precise resuscitation endpoint. The skin is the first tissue bed to vasoconstrict in shock states. Studies have demonstrated that transcutaneous partial pressure of oxygen (PtCO2) increases with higher FiO2 in nonshock states as arterial pressure of oxygen (PaO2) increases, but in shock situations, PtCO2 mirrors changes in cardiac output and oxygen delivery with minimum response to increasing FiO2 and PaO2. This study examined the relationship of hemodynamic variables and the degree of PtCO2 response to FiO2 of 1.0 (identified as the "oxygen challenge test") to mortality and organ failure. This prospective observational study examined 38 patients requiring at least 24 h of cardiac output monitoring for shock resuscitation in the Surgical Intensive Care Unit. Patients were resuscitated to the standard protocol of blood pressure, urine output, oxygen delivery (DO2), and mixed venous O2 (SvO2). Seventy-nine percent of the patients (30/38) with a mean age of 59 +/- 21 years had septic shock or severe sepsis with a 26% mortality (10/38). Measurements included hemodynamic variables, PtCO2, and outcome (mortality and organ failure). In this study, the ability of PtCO2 value to increase by 21 mmHg on a FiO2 of 1.0, at 24 h of resuscitation, divided survivors from nonsurvivors, P <.001. The PtCO2 response to FiO2 may provide an additional noninvasive method of detecting early shock as well as a specific endpoint of resuscitation.

Noninvasive hemodynamic monitoring for early warning of adult respiratory distress syndrome in trauma patients

Purpose: Traditionally hemodynamic patterns after adult respiratory distress syndrome (ARDS) are described after appropriate diagnostic criteria have been met, but studies begun after the diagnosis of ARDS miss the antecedent circulatory influences that may contribute to its development. This study tests the hypothesis that noninvasive monitoring before the appearance of ARDS may reveal early circulatory deficiencies that lead to this disorder. The aims of this study are as follows: (1) to describe the time course of hemodynamic and tissue perfusion patterns in severely traumatized postoperative patients from the period immediately after admission and during surgical repair to the time that ARDS developed or to hospital discharge in patients who did not develop ARDS, (2) to compare the time course of these patterns in survivors and nonsurvivors of ARDS, and (3) to suggest that reduced flow and perfusion may be early warning signs of ARDS. Prospective descriptive study of severely injured trauma patients noninvasively monitored in the emergency department, operating room, and intensive care unit (ICU). Early hemodynamic patterns were described in the surviving and nonsurviving patients who subsequently developed ARDS. The study was performed in a University-affiliated Level I trauma center and ICU. Patients and Methods: A consecutively monitored series of 60 severely injured patients were prospectively monitored by cardiac output, pulse oximetry (SapO2), and transcutaneous O2 and CO2 (PtcO2 and PtcCO2) sensors immediately after emergency admission. Twentynine patients developed ARDS in their ICU course, whereas 31 were discharged from the ICU and the hospital without developing ARDS. Results: Patients who developed ARDS had significantly lower cardiac index and PtcO2 and higher PtcCO2 values beginning with the early stage compared with those who did not develop ARDS. Nonsurvivors of ARDS had lower PtcO2 values than did the survivors. Conclusion: Early noninvasive monitoring in the emergency department, operating room, and ICU showed reduced cardiac and tissue perfusion functions in patients who subsequently developed ARDS. These patterns were more pronounced in the ARDS patients who died; these patterns may serve as early warning of ARDS. Copyright © 2000 by W.B. Saunders Company

Transcutaneous oxygen and CO2 as early warning of tissue hypoxia and hemodynamic shock in critically ill emergency patients.

Although cardiac and pulmonary function can be measured precisely, evaluation of tissue perfusion remains elusive because it usually is inferred from subjective symptoms and imprecise signs of shock. The latter are indirect criteria used to assess the overall circulatory status as well as tissue perfusion but are not direct quantitative measures of perfusion. However, noninvasive transcutaneous oxygen (PtcO2) and carbon dioxide (PtcCO2) tensions, which directly measure skin oxygenation and CO2 retention, may be used to objectively evaluate skin oxygenation and perfusion in emergency patients beginning with resuscitation immediately after hospital admission. This study was a preliminary evaluation of tissue oxygenation and perfusion by objective PtcO2 and PtcCO2 patterns in severely injured surviving and nonsurviving patients; specifically, the aim was to describe time patterns that may be used as early warning signs of circulatory dysfunction and death. Prospective descriptive study of a consecutive series of severely injured emergency patients. University-affiliated Level I trauma center and intensive care unit. Forty-eight consecutive severely injured patients were prospectively monitored by PtcO2 and PtcCO2 sensors immediately after emergency admission. Compared with survivors, patients who died had significantly lower PtcO2 and higher PtcCO2 values beginning with the early stage of resuscitation. All patients who maintained PtcO2 >150 torr (19.99 kPa) throughout monitoring survived. Periods of PtcO2 <50 torr (6.66 kPa) for >60 mins or PtcCO2 >60 torr (8.00 kPa) for >30 mins were associated with 90% mortality and 100% morbidity. PtcO2 and PtcCO2 monitoring continuously evaluate tissue perfusion and serve as early warning in critically injured patients during resuscitation immediately after hospital admission.