Evaluation of two combined oxygen and carbon dioxide transcutaneous sensors.

Two combined oxygen and carbon dioxide electrodes were assessed in neonates, infants, and children up to 16 years. They were convenient to use and the measurement error for PtcCO2 was acceptable. In both models, however, the PtcO2 electrode had a reduced performance compared with a single electrode.     

无创经皮监测氧气和二氧化碳在新生儿的应用

无创经皮监测(transcutaneous monitoring,TCM)氧气和二氧化碳是新生儿重症监护室(neo-natal intensive care unit,NICU)的常用技术,具有连续性、无创性的特点,能直观反映危重新生儿呼吸和循环功能的变化,对新生儿监护意义重大.该文阐述TCM的使用方法,比较TCM与其他监测手段的优缺点,并介绍其在新生儿转运及NICU的应用.     

Lateral positioning of the stable ventilated very-low-birth-weight infant. Effect on transcutaneous oxygen and carbon dioxide

Eighteen stable very-low-birth-weight (VLBW) mechanically ventilated infants with chronic lung disease were studied to examine the effects of right and left lateral positioning in contrast to supine positioning on transcutaneous (tc) oxygen (tcPO2) and carbon dioxide measurements (tcPCO2). The neonates were studied at a median postnatal age of 31 days (range, 17 to 57 days) and had median birth weights and gestational ages of 975 g (range, 570 to 1360 g) and 27.5 weeks (range, 24 to 30 weeks), respectively. Median fraction of inspiratory oxygen was 0.32 (range, 0.23 to 0.40). The sequence of study positions was randomly determined. Sleep state as well as tcPO2 and tcPCO2 were recorded every 30 s for five minutes. A significant difference in mean tcPO2 or tcPCO2 was not detected for any of the positions. Lateral positioning may facilitate the development of midline behavior in VLBW infants. Care givers are often reluctant to position infants in side lying, however, because of concerns that ventilation or oxygenation might be compromised. We conclude that placing the stable VLBW mechanically ventilated infant in a side-lying position has no deleterious effects on oxygenation and ventilation, as measured by tcPO2 and tcPCO2, and therefore should be encouraged.     

Monitoring of end tidal carbon dioxide and transcutaneous carbon dioxide during neonatal transport

OBJECTIVE: To assess the accuracy of measurements of end tidal carbon dioxide (CO2) during neonatal transport compared with arterial and transcutaneous measurements. DESIGN: Paired end tidal and transcutaneous CO2 recordings were taken frequently during road transport of 21 ventilated neonates. The first paired CO2 values were compared with an arterial blood gas. The differences between arterial CO2 (Paco2), transcutaneous CO2 (TcPco2), and end tidal CO2 (Petco2) were analysed. The Bland-Altman method was used to assess bias and repeatability. RESULTS: Petco2 correlated strongly with Paco2 and TcPco2. However, Petco2 underestimated Paco2 at a clinically unacceptable level (mean (SD) 1.1 (0.70) kPa) and did not trend reliably over time within individual subjects. The Petco2 bias was independent of Paco2 and severity of lung disease. CONCLUSIONS: Petco2 had an unacceptable under-recording bias. TcPco2 should currently be considered the preferred method of non-invasive CO2 monitoring for neonatal transport.     

Evaluation of a transcutaneous oxygen and carbon dioxide monitor in a neonatal intensive care department

Transcutaneous-PO2 (tc-PO2 (tc-PCO2) at 44 degrees C and transcutaneous-PCO2) at 38, 42, 43 and 44 degrees C were measured with a currently available monitoring system (TCM222, Radiometer, Copenhagen) in 64 newborn infants with severe respiratory insufficiency during the first five days of life. Tc-PCO2 at all four temperatures correlated better with arterial blood-PCO2 (aB-PCO2), than tc-PO2 with aB-PO2. However, the sensitivity and specificity of tc-PO2 and tc-PCO2 were similar with regard to maintaining aB-PO2 and aB-PCO2 within specified limits. Tc-PCO2 increased relatively with increasing electrode temperature by a factor which was similar to the anaerobic temperature coefficient of PCO2 in blood. The coefficient of variation of duplicate measurements was 10% for tc-PO2 and 5% for tc-PCO2. Electrode drift after an average of 3 hours patient monitoring was 2% +/- 6% (1 SD) for tc-PO2 and -3% +/- 6% for tc-PCO2. We conclude that tc-PO2 and tc-PCO2 are a valuable supplement to arterial blood gas measurements, but the variable correlation with arterial blood gas values and the electrode drifts which may occur, mean that they cannot fully replace arterial sampling.     

Increasing arterial carbon dioxide tension: influence on transcutaneous carbon dioxide tension measurements

Despite widespread use of transcutaneous PCO2 (TcPCO2) monitoring, the precise relationship between TcPCO2 and PaCO2 remains unclear. It has been widely assumed that theoretical correction of TcPCO2 (combining temperature correction with a constant metabolic factor of 4 mm Hg) accounts for the elevation of TcPCO2 over PaCO2. To test this assumption, TcPCO2 was measured with a 44 degrees C electrode and compared to PaCO2 in 60 normotensive infants with cardiorespiratory disease during the first four +/- six days of life (mean +/- SD) (range one to 36 days). During hypocapnea, from PaCO2. In contrast, during normocapnea, theoretically corrected TcPCO2 exceeded PaCO2 by 5 +/- 4 mm Hg (P less than .001), and similarly during hypercapnea, theoretically corrected TcPCO2 exceeded PaCO2 by 9 +/- 6 mm Hg (P less than .001). These data suggest that, as PaCO2 increases, there may be an imbalance between tissue CO2 production and removal, resulting in a progressively increasing gradient between TcPCO2 and PaCO2. Clarification of the relationship between TcPCO2 and PaCO2 should enhance the interpretation of TcPCO2 measurements in infants.     

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??PaO2 and PaCO2 monitoring is the most important indicators of ventilation and oxygenation in the NICU. The results of PaO2 and PaCO2 are from blood gas obtained by collecting arterial or peripheral blood samples. Repeated blood sampling is frequently needed in critically ill neonates??which may increase the risk of neonatal infection, iatrogenic anemia and pain stress. TcPCO2 and TcPO2??as the noninvasive monitors??have been emerging as non-invasive blood gas monitoring in the clinical care of critically ill neonates??especially the VLBWandELBWinfants??during neonatal oxygentherapy??mechanical ventilation and shock requiring perfusion monitoring.     

Influence of breathing pattern on transcutaneous oxygen and carbon dioxide tension during histamine provocation in children with bronchial asthma

The influence of the breathing pattern on transcutaneous blood gases was evaluated in 18 boys and 8 girls 7–18 years of age, with bronchial asthma, during bronchial provocation with histamine-HCI. Transcutaneous oxygen tension (tcPo₂), carbon dioxide tension (tcPco₂) and the breathing pattern assessed by the transthoracic impedance technique were continuously monitored during the provocation. At reaction, when the fall in the forced expiratory volume in 1 s (FEV₁) was 20% or more. the tcPo₂ fell by 15% or more below the baseline in 22/26 and by 20% or more in 14/26 children. In some children, a marked fall in the tcPo₂ was already noted after the saline inhalation and the first histamine dose steps without simultaneous changes in the FEV₁. This early fall in the tcPo₂ correlated to changes in the breathing pattern and was interpreted as a sign of compensatory hypoventilation secondary to the hyperventilation observed during the inhalations. We conclude that transcutaneous oxygen tension can be used as an indicator of a bronchial reaction during bronchial provocation tests in children only if one takes account of the fact that the breathing pattern during the inhalation of the challenge compound per se has an effect on the oxygen tension.     

Transcutaneous oxygen and carbon dioxide monitoring in intensive care.

Transcutaneous oxygen (TcPo2) and carbon dioxide (TcPco2) tensions were compared with arterial values in 23 children aged 4 months to 14 years, all requiring some form of respiratory support, but not in shock. Electrodes were placed on the upper chest and were heated to 45 degrees C. For TcPo2 and arterial oxygen (Pao2) a tight linear correlation over the range 6 to 14 kPa was found. Arterial carbon dioxide (Paco2) ranged between 2.63 and 6.8 kPa, and over this range a linear regression adequately described the relation of TcPco2 to Paco2. No effects of age were found for the relation between TcPo2 and Pao2. Over a four hour period, the mean ratio TcPo2/Pao2 rose significantly from 0.96 to 1.04, while the mean ratio of TcPco2/Paco2 fell from 1.65 to 1.62. Five children developed superficial burns which were still present at 48 hours. In children who require respiratory support but are not in shock, TcPo2 and TcPco2 bear a constant and predictable relation to Pao2 and Paco2, and can predict arterial values within clinically acceptable tolerances.     

电极温度对极低出生体重儿经皮二氧化碳分压和氧分压监测的影响

目的 评估在低于临床常用的电极温度下进行经皮二氧化碳分压(transcutaneous carbon dioxide partial pressure,TcPCO2)和经皮氧分压(transcutaneous oxygen partial pressure,TcPO2)监测在极低出生体重儿应用中的准确性和安全性.方法 ...     

Ventilatory interaction between oxygen and carbon dioxide in the preterm primate

The steady state ventilatory response to inhaled CO2 was measured in eleven unanesthetized premature Macaca nemestrina during the first 3 wk of life in different steady state background O2 mixtures hypoxia (FIO2 = 0.08 or 0.12), normoxia (FIO2 = 0.21) and hyperoxia (FIO2 = 0.96). Hyperoxic delta VI/delta PACO2 and delta P0.2/ delta PACO2 were significantly greater than hypoxic delta VI/ delta PACO2 and delta P0.2/delta PACO2, respectively, at both 2 and 21 days postnatal age by the Mann Whitney test of nonparametric ranking (2 days: 89.. and 80.2 degrees versus 88.7 and 56.4 degrees, respectively; 21 days: 89.3 and 76.6 degrees versus 50.2 and 57.1 degrees, respectively; p less than 0.05). Hypoxic delta VI/delta PACO2 was significantly depressed compared to normoxic delta VI/ delta PACO2 only at 21 days of age (50.2 versus 89.4 degrees, respectively; p less than 0.05); hyperoxic CO2 sensitivity and normoxic CO2 sensitivity did not differ at either age. The ventilatory interaction between O2-CO2 in the neonatal primate appears to be the inverse of the typical adult ventilatory interaction. It is hypothesized that differential changes in brain stem blood flow between neonates and adults might explain this difference in O2-CO2 ventilatory interaction.     

Long-term transcutaneous monitoring of oxygen tension and carbon dioxide at 42°C in critically ill neonates: improved performance of the tcpo2 monitor with topical metabolic inhibition

Whereas during the last few years handling of the transcutaneous PO₂ (tcPO₂) and PCO₂ (tcPCO₂) sensor has been simplified, the high electrode temperature and the short application time remain major drawbacks. In order to determine whether the application of a topical metabolic inhibitor allows reliable measurement at a sensor temperature of 42° C for a period of up to 12 h, we performed a prospective, open, nonrandomized study in a sequential sample of 20 critically ill neonates. A total of 120 comparisons (six repeated measurements per patient) between arterial and transcutaneous values were obtained. Transcutaneous values were measured with a control sensor at 44° C (conventional contact medium, average application time 3 h) and a test sensor at 42° C (Eugenol solution, average application time 8 h). Comparison of tcPO₂ and PaO₂ at 42° C (Eugenol solution) showed a mean difference of +0.16 kPa (range +1.60 to –2.00 kPa), limits of agreement +1.88 and –1.56 kPa. Comparison of tcPO₂ and PaO₂ at 44° C (control sensor) revealed a mean difference of +0.02 kPa (range +2.60 to –1.90 kPa), limits of agreement +2.12 and –2.08 kPa. Comparison of tcPCO₂ and PaCO₂ at 42° C (Eugenol solution) showed a mean difference of +0.91 (range +2.30 to +0.10 kPa), limits of agreement +2.24 and –0.42 kPa. Comparison of tcPCO₂ and PaCO₂ at 44° C (control sensor) revealed a mean difference of +0.63 kPa (range 1.50 to –0.30 kPa), limits of agreement +1.73 and –0.47 kPa. Conclusion Our results show that the use of an Eugenol solution allows reliable measurement of tcPO₂ at a heating temperature of 42° C; the application time can be prolongued up to a maximum of 12 h without aggravating the skin lesions. The performance of the tcPCO₂ monitor was slightly worse at 42° C than at 44° C suggesting that for the Eugenol solution the metabolic offset should be corrected. Received: 13 January 1995 Accepted: 17 February 1996     

Effects of 2% carbon dioxide, 0.5% carbon dioxide, and 100% oxygen on cranial blood flow of the human neonate

The effects of breathing 100% O2, 2% CO2, and 0.5% CO2 on the cranial blood flow of the normal human baby were investigated. A mercury in Silastic strain gauge was placed around the occipital head circumference (OFC) of a sleeping infant, and jugular flow was measured using venous occlusion plethysmography. Cranial flow was calculated using formulas derived from an electrical model. In matched sleep states cranial blood flow fell with 100% O2 (mean from eight babies = 32.8%), and rose with 2% CO2 (mean from seven babies = 40.6%). With 0.5% CO2 the flow rose in three babies and did not change in another four. These results indicate the extreme sensitivity of cerebral vasculature to the nature of the ambient gas.     

Transcutaneous oxygen and carbon dioxide during the first half year of life in premature and normal term infants.

Repetitive polysomnograms were recorded from a total of 33 infants, 19 healthy preterm infants, and 14 term controls between 40 wk postconceptional age and 6 mo of age. These nighttime recordings lasted 2-4 h, except at 52 wk in preterm infants and at 3 mo of age in term infants when an overnight 12-h recording was performed. Minute by minute values of transcutaneous PO2 (PtCO2) and transcutaneous PCO2 (PtcCO2) levels and variability during the awake state, active sleep, and quiet sleep were obtained through computer analyses of the polygraphic data. The results from preterm infants at corrected postconceptional age could not be differentiated from those of control infants. PtCO2 levels rose between 40 wk and 3 mo, and PtcCO2 levels declined. Sleep states modulated only the variability of PtcO2, not the level; in contrast, state modulation was seen in both variability and level of PtcCO2 throughout the age span studied. During sleep the number of transient declines in PtCO2 greater than 2.03 kPa (15 mm Hg) decreased with advancing age. Hypercapnic PtcCO2 values decreased with age as well, but their prevalence in healthy, young infants suggests the need for reevaluation of criteria for hypercapnia based on transcutaneous measurements. The data demonstrate that ventilatory regulation continues to undergo changes between 1 and 3 mo, the age of highest risk for sudden infant death syndrome.     

Blood oxygen, carbon dioxide and pH levels prior to diagnosis of retinopathy of prematurity

We examined the eyes of all infants in our Neonatal Intensive Care Unit from 1979 to 1981 who were premature and/or had exposure to increased ambient oxygen. From these 1,012 neonates, 19 were found to have Grade III or worse acute retinopathy of prematurity (ROP) in at least one eye. We studied the graphic relationship of the mean daily values for blood Pc02, Pa02, PC02, and pH and the production of retinopathy of prematurity in these infants and compared the results with a similar group of infants who had similar birthweight, gestational age and Vitamin E administration. The comparison group patients were in the hospital during this same period of time and did not have Grade III ROP. There was no characteristic level, peak or pattern of these values that could identify or predict which infants would develop ROP.