Transcutaneous carbon dioxide monitoring in infants and children

Accuracy and Interpretation of Transcutaneous Carbon Dioxide Monitoring in Critically Ill Children

OBJECTIVES

Transcutaneous carbon dioxide (Tcco2) monitoring can noninvasively assess ventilation by estimating carbon dioxide (CO2) levels in the blood. We aimed to evaluate the accuracy of Tcco2 monitoring in critically ill children by comparing it to the partial pressure of arterial carbon dioxide (Paco2). In addition, we sought to determine the variation between Tcco2 and Paco2 acceptable to clinicians to modify patient care and to determine which patient-level factors may affect the accuracy of Tcco2 measurements.

DESIGN

Retrospective observational cohort study.

SETTING

Single, quaternary care PICU from July 1, 2012, to August 1, 2020.

PATIENTS

Included participants were admitted to the PICU and received noninvasive ventilation support (i.e., continuous or bilevel positive airway pressure), conventional mechanical ventilation, or high-frequency oscillatory or percussive ventilation with Tcco2 measurements obtained within 15 minutes of Paco2 measurement.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Three thousand four hundred seven paired arterial blood gas and Tcco2 measurements were obtained from 264 patients. Bland-Altman analysis revealed a bias of -4.4 mm Hg (95% CI, -27 to 18.3 mm Hg) for Tcco2 levels against Paco2 levels on the first measurement pair for each patient, which fell within the acceptable range of ±5 mm Hg stated by surveyed clinicians, albeit with wide limits of agreement. The sensitivity and specificity of Tcco2 to diagnose hypercarbia were 93% and 71%, respectively. Vasoactive-Infusion Score (VIS), age, and self-identified Black/African American race confounded the relationship between Tcco2 with Paco2 but percent fluid overload, weight-for-age, probe location, and severity of illness were not significantly associated with Tcco2 accuracy.

CONCLUSIONS

Tcco2 monitoring may be a useful adjunct to monitor ventilation in children with respiratory failure, but providers must be aware of the limitations to its accuracy.

Continuous real-time monitoring of carbon dioxide emitted from human skin by quartz-enhanced photoacoustic spectroscopy

In this study, a skin gas detection system based on quartz enhanced photoacoustic spectroscopy (QEPAS) with a constant temperature collection chamber and an automatic frequency adjustment function was used to collect and monitor carbon dioxide (CO₂) emissions from human skin. The detection element of the system is an on-beam structure assembled by a 30.72 kHz quartz tuning fork (QTF). A laser with a wavelength of 4991.26 cm^-1 is emitted (with a wavelength adjustment range of 10 cm^-1) to excite the QTF. When the integration time is 365 s, the system can achieve a minimum detection limit (MDL) of 2.6 ppmv. The sensitivity of the system is 636.9 ppmv/V. The gas detection system is used to monitor the concentration of CO₂ emissions from different parts of the skin and the same part covered by different cosmetics. The CO₂ emission rate is defined as the ratio of the skin gas monitoring time of 25 min to the CO₂ concentration variable in the gas chamber (volume of 8 mL). The results were collected from three healthy volunteers. Among the six different parts, the cheeks emitted the fastest rate (the average rate was 365.5 ppmv/min) of CO₂, and the thighs emitted the slowest rate (the average rate was 56.4 ppmv/min) of CO₂. Comparing the experimental results of the six sites at different times, the order of the CO₂ emission rate is identical for all six sites. In the experiments with the three cosmetic products (experimental site: forearm), comparing the CO₂ emission rate from clean skin with the CO₂ emission rate from cosmetic-covered skin shows that sunscreen is the most breathable, followed by barrier cream, and foundation is the least breathable.

Noninvasive carbon dioxide monitoring in pediatric patients undergoing laparoscopic surgery: transcutaneous vs. end-tidal techniques

PURPOSE

The present study aimed to investigate the correlation between transcutaneous carbon dioxide partial pressure (PtcCO₂) and arterial carbon dioxide pressure (PaCO₂) and the accuracy of PtcCO₂ in predicting PaCO₂ during laparoscopic surgery in pediatric patients.

METHODS

Children aged 2-8 years with American Society of Anesthesiologists (ASA) class I or II who underwent laparoscopic surgery under general anesthesia were selected. After anesthesia induction and tracheal intubation, PtcCO₂ was monitored, and radial arterial catheterization was performed for continuous pressure measurement. PaCO₂, PtcCO₂, and end-tidal carbon dioxide partial pressure (PetCO₂) were measured before pneumoperitoneum, and 30, 60, and 90 min after pneumoperitoneum, respectively. The correlation and agreement between PtcCO₂ and PaCO₂, PetCO₂, and PaCO₂ were evaluated.

RESULTS

A total of 32 patients were eventually enrolled in this study, resulting in 128 datasets. The linear regression equations were: PtcCO₂ = 7.89 + 0.82 × PaCO₂ (r² = 0.70, P < 0.01); PetCO₂ = 9.87 + 0.64 × PaCO₂ (r² = 0.69, P < 0.01). The 95% limits of agreement (LOA) of PtcCO₂ - PaCO₂ average was 0.66 ± 4.92 mmHg, and the 95% LOA of PetCO₂ - PaCO₂ average was -4.4 ± 4.86 mmHg. A difference of ≤ 5 mmHg was noted between PtcCO₂ and PaCO₂ in 122/128 samples and between PetCO₂ and PaCO₂ in 81/128 samples (P < 0.01).

CONCLUSION

In pediatric laparoscopic surgery, a close correlation was established between PtcCO₂ and PaCO₂. Compared to PetCO₂, PtcCO₂ can estimate PaCO₂ accurately and could be used as an auxiliary monitoring indicator to optimize anesthesia management for laparoscopic surgery in children; however, it is not a substitute for PetCO₂.

REGISTRATION NUMBER OF CHINESE CLINICAL TRIAL REGISTRY

ChiCTR2100043636.

Monitoring of carbon dioxide in ventilated neonates: a prospective observational study

OBJECTIVE

To assess the reliability, accuracy and precision of distal end-tidal capnography (detCO₂) in neonates compared with transcutaneous (tcCO₂) carbon dioxide measurements.

DESIGN

Observational, prospective clinical study.

SETTING

Neonatal intensive care unit at Medical University of Vienna.

PARTICIPANTS

Conventionally ventilated neonates with a body weight between 1000 g and 3000 g.

INTERVENTION

End-tidal partial pressure of CO₂ was measured in distal position using the separate lumen of a double-lumen endotracheal tube connected to an external side-stream capnometer. Three consecutive detCO₂ and tcCO₂ values were recorded simultaneously and compared with simultaneous arterialised partial pressure of CO₂ (paCO₂) measurements in each patient.

MAIN OUTCOME MEASURES

Reliability, accuracy and precision of detCO₂ and tcCO₂ measurements compared with paCO₂ in neonates.

RESULTS

Twenty-five neonates were included with a median (range) weight at enrolment of 1410 (1010-2980) g, from which 81 simultaneous measurements of detCO₂, tcCO₂ and paCO₂ were obtained. The mean (SD) of paCO₂, detCO₂ and tcCO₂ was 45.0 (8.6) mmHg, 42.4 (8.4) mmHg and 50.4 (20.4) mmHg, respectively. The intraclass correlation between paCO₂ and detCO₂ and between paCO₂ and tcCO₂ reached 0.80 (95% CI 0.71 to 0.87, p<0.001) and 0.59 (95% CI 0.43 to 0.72, p<0.001), respectively. In the Bland-Altman analysis, bias and precision of detCO₂ with respect to paCO₂ amounted to -2.68 mmHg and 10.62 mmHg (95% CI 8.49 to 14.51), respectively. Bias and precision of tcCO₂ with respect to paCO₂ amounted to 5.39 mmHg and 17.22 mmHg (95% CI 13.21 to 23.34), respectively.

CONCLUSION

DetCO₂ had better reliability, accuracy and precision with paCO₂ than tcCO₂ in ventilated neonates without severe lung diseas.

TRIAL REGISTRATION NUMBER

NCT03758313.

Transient End-Tidal Carbon Dioxide Elevation During Pediatric Upper Endoscopy With Carbon Dioxide Insufflation: Is It True Hypercapnia?

BACKGROUND

Endoscopic insufflation, long performed using air, is being replaced by carbon dioxide (CO2) at many pediatric centers, despite limited published data on its use in children. We have previously demonstrated that CO2 use during esophagogastroduodenoscopy (EGD) in non-intubated children is associated with transient elevations of end-tidal CO2 (EtCO2). This observation raised concerns about possible CO2 inhalation and systemic absorption. Here, we investigate this concern by concurrently measuring both EtCO2 and transcutaneous CO2 (tCO2) during upper endoscopic procedures in children.

AIM

To determine if elevations in EtCO2 levels seen in non-intubated children undergoing CO2 insufflation during EGD are associated with elevated systemic CO2 levels.

METHODS

Double-blinded, prospective, randomized clinical trial. Children were randomized 1:1 to receive either CO2 or air for endoscopic insufflation. EtCO2 was sampled with a CO2-sampling nasal cannula and tCO2 was monitored using the Radiometer transcutaneous monitoring device.

RESULTS

Fifty nine patients were enrolled; 30 patients in the CO2 insufflation group and 29 in the air group. All patients underwent a procedure involving an EGD. Transient elevations in EtCO2 (defined as >60 mmHg) were observed only in the CO2 insufflation group. This contrasted with the similar elevations of tCO2 between the CO2 and air insufflation groups. None of these events were of clinically significant magnitude or duration.

CONCLUSION

This study demonstrates that the observed transient elevations in EtCO2 seen during EGD in non-intubated children receiving CO2 insufflation are most likely measurements of eructated CO2 without evidence of excessive systemic absorption of CO2.

Strategy to Reduce Hypercapnia in Robot-Assisted Radical Prostatectomy Using Transcutaneous Carbon Dioxide Monitoring: A Prospective Observational Study

Purpose

Monitoring end-tidal carbon dioxide partial pressure (P_ETCO₂) is a noninvasive, continuous method, but its accuracy is reduced by prolonged capnoperitoneum and the steep Trendelenburg position in robot-assisted radical prostatectomy (RARP). Transcutaneous carbon dioxide partial pressure (P_TCCO₂) monitoring, which is not affected by ventilator–perfusion mismatch, has been suggested as a suitable alternative. We compared the agreement of noninvasive measurements with the arterial carbon dioxide partial pressure (PaCO₂) over a long period of capnoperitoneum, and investigated its sensitivity and predictive power for detecting hypercapnia.

Patients and Methods

The patients who underwent RARP were enrolled in this study prospectively. Intraoperative measurements of P_ETCO₂, P_TCCO₂, and PaCO₂ were analyzed. The primary outcome was the agreement of noninvasive monitoring with PaCO₂ during prolonged capnoperitoneum. Bias and precision between noninvasive measurements and PaCO₂ were assessed using Bland–Altman analysis. The bias and mean absolute difference were compared using a two-tailed Wilcoxon signed-rank test for pairs. The secondary outcome was the sensitivity and predictive power for detecting hypercapnia. To assess this, the Yates corrected chi-square test and the area under the receiver operating characteristic curve were used.

Results

The study analyzed 219 datasets from 46 patients. Compared with P_ETCO₂, P_TCCO₂ had lower bias, greater precision, and better agreement with PaCO₂ throughout the RARP. The mean absolute difference in P_ETCO₂ and PaCO₂ was larger than that of P_TCCO₂ and PaCO_2, and continued to exceed the clinically acceptable range of 5 mmHg after 1 hour of capnoperitoneum. The sensitivity during capnoperitoneum and overall predictive power of P_TCCO₂ for detecting hypercapnia were significantly higher than those of P_ETCO₂, suggesting a greater contribution to ventilator adjustment, to treat hypercapnia.

Conclusion

P_TCCO₂ monitoring measured PaCO₂ more accurately than P_ETCO₂ monitoring during RARP requiring prolonged capnoperitoneum and a steep Trendelenburg position. P_TCCO₂ monitoring also provides more sensitive measurements for ventilator adjustment and detects hypercapnia more effectively than P_ETCO₂ monitoring.

Validation of a new combined transcutaneous tcPCO2 and tcPO2 sensor in children in the operating theater

BACKGROUND

Arterial blood gas analysis is the gold standard for monitoring of P_a CO₂ and PaO₂ during mechanical ventilation. However, continuous measurements would be preferred. Transcutaneous sensors continuously measure blood gases diffusing from the locally heated skin. These sensors have been validated in children mostly in intensive care settings. Accuracy in children during general anesthesia is largely unknown.

AIMS

We conducted a study in children undergoing general anesthesia to validate the use and to determine the accuracy of continuous transcutaneous measurements of the partial pressures of PCO₂ (tcPCO₂ ) and PO₂ (tcPO₂ ).

METHODS

A prospective observational study in a tertiary care pediatric hospital in The Netherlands, from April to October 2018, in children aged 0-18 years undergoing general anesthesia. Patients were included when endotracheally intubated and provided with an arterial catheter for regular blood sampling. Patients with a gestational age <31 weeks, burn victims, and patients with skin disease were excluded. TcPCO₂ and tcPO₂  measurements were performed with a SenTec OxiVenT^™ sensor (SenTec AG). Accuracy was determined with an agreement analysis between arterial and transcutaneous PCO₂ and PO₂  values, and between arterial and endtidal PCO₂ (etCO₂ ) values, according to Bland and Altman, accounting for multiple measurements per subject.

RESULTS

We included 53 patients (median age 4.1 years, IQR 0.7-14.4 years) and retrieved 175 samples. TcPCO₂ -P_a CO₂ agreement analysis provided a bias of 0.06 kPa (limits of agreement (LOA) -1.18 to 1.31), the etCO₂ -P_a CO₂ agreement showed a bias of -0.31 kPa (LOA -1.38 to 0.76). Results of the tcPO₂ -PaO₂ agreement showed a bias of 3.40 to 0.86* (mean tension) kPa.

CONCLUSIONS

This study showed good agreement between P_a CO₂ and tcPCO₂ in children of all ages during general anesthesia. Both transcutaneous and endtidal CO₂  measurements showed good accuracy. TcPO₂ is only accurate under 6 months of age.

Sleep-related hypoventilation and hypercapnia in multiple system atrophy detected by polysomnography with transcutaneous carbon dioxide monitoring

Purpose

We aimed to evaluate sleep-related hypoventilation in multiple system atrophy (MSA) using polysomnography (PSG) with transcutaneous partial pressure of carbon dioxide (PtcCO₂) monitoring.

Methods

This prospective study included 34 patients with MSA. Motor and autonomic function, neuropsychological tests, PSG with PtcCO₂ monitoring, and pulmonary function tests were performed. Sleep-related hypoventilation disorder (SRHD) was defined according to the International Classification of Sleep Disorders, third edition.

Results

Nine (27%) of the 34 patients met the diagnostic criteria of SRHD. Twenty-nine (85%) patients had sleep-related breathing disorders based on an Apnea–Hypopnea Index of ≥ 5/h. The patients with MSA and SRHD had a higher arousal index (p = 0.017) and obstructive apnea index (p = 0.041) than those without SRHD. There was no difference in the daytime partial pressure of carbon dioxide in arterial blood or respiratory function between MSA patients with and without SRHD.

Conclusion

Sleep-related hypoventilation may occur in patients with MSA even with a normal daytime partial pressure of carbon dioxide. This can be noninvasively detected by PSG with PtcCO₂ monitoring. SRBD and sleep-related hypoventilation are common among patients with MSA, and clinicians should take this into consideration while evaluating and treating this population.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11325-022-02568-4.

Carbon dioxide monitoring in the newborn infant

Carbon dioxide (CO₂ ) monitoring is vital during mechanical ventilation of newborn infants, as morbidity increases when CO₂ levels are inappropriate. Our aim was to review the uses and limitations of such noninvasive monitoring methods. Colorimetry is primarily utilized during resuscitation to determine whether successful intubation has occurred. False negative and positive results can however lead to delays in detecting tracheal versus esophageal intubation. Transcutaneous carbon dioxide sensors have limited use during resuscitation, but can be utilized to provide continuous trend data during on-going ventilation. End-tidal capnography can provide clinicians with quantitative end-tidal CO₂ (EtCO₂ ) values and a continuous real-time capnogram waveform trace. These devices are becoming more widely accepted for use in the neonatal population as the new devices are lightweight with minimal additional dead space. Nevertheless, they have been reported to have variable accuracy when compared to arterial CO₂ measurements, however, divergence of results may be related to disease severity rather than technological limitations. During resuscitation EtCO₂ can be detected by capnography more rapidly than by colorimetry. Furthermore, capnography can be currently utilized in neonatal research settings to determine the physiological dead space and ventilation inhomogeneity, and thus has potential to be beneficial to clinical care. In conclusion, novel modes of noninvasive carbon dioxide monitoring can be safely and reliably utilized in newborn infants during mechanical ventilation. Future randomized trials should aim to address which device provides the most optimal form of monitoring in different clinical contexts.

Wearable Transcutaneous CO2 Monitor Based on Miniaturized Nondispersive Infrared Sensor

Transcutaneous oxygen and carbon dioxide provide the status of pulmonary gas exchange and are of importance in diagnosis and management of respiratory diseases. Though significant progress has been made in oximetry, not much has been explored in developing wearable technologies for continuous monitoring of transcutaneous carbon dioxide. This research reports the development of a truly wearable sensor for continuous monitoring of transcutaneous carbon dioxide using miniaturized nondispersive infrared sensor augmented by hydrophobic membrane to address the humidity interference. The wearable transcutaneous CO₂ monitor shows well-behaved response curve to humid CO₂ with linear response to CO₂ concentration. The profile of transcutaneous CO₂ monitored by the wearable device correlates well with the end-tidal CO₂ trend in human test. The feasibility of the wearable device for passive and unobstructed tracking of transcutaneous CO₂ in free-living conditions has also been demonstrated in field test. The wearable transcutaneous CO₂ monitoring technology developed in this research can be widely used in remote assessment of pulmonary gas exchange efficiency for patients with respiratory diseases, such as COVID-19, sleep apnea, and chronic obstructive pulmonary disease (COPD).

Association of transcutaneous CO2 with respiratory support: a prospective double blind observational study in children with bronchiolitis and reactive airway disease

The use of clinical scoring to assess for severity of respiratory distress and respiratory failure is challenging due to subjectivity and interrater variability. Transcutaneous Capnography (TcpCO₂) can be used as an objective tool to assess a patient’s ventilatory status. This study was designed to assess for any correlation of continuous monitoring of TcpCO₂ with the respiratory clinical scores and deterioration in children admitted for acute respiratory distress. A prospective observational study over one year on children aged 2 weeks to 5 years admitted with acute respiratory distress or failure secondary to Bronchiolitis and Reactive airway disease was performed. Continuous TcpCO₂ monitoring for upto 48 h was recorded. Investigators, bedside physicians, respiratory therapists, and nurses were blinded from the transcutaneous trends at the time of data collection. Total of 813 TcpCO₂ measurements at standard intervals of 30 min were obtained on 38 subjects. Subjects with abnormal TcpCO₂ (> 45 mmHg) were younger (6.9 ± 5.2 vs. 23.05 ± 17.7 months,) and were more likely to be on higher oxygen flow rate (0.52 L/min/kg vs 0.46 lier/min/kg, p = 0.004) and higher FiO₂ (38.4 vs 33.6, p < 0.001 using heated high flow nasal cannula. No difference was found in bronchiolitis score or PEW score in subjects with normal and abnormal TcpCO₂. A small but statistically significant increase in TcpCO₂ was observed at the escalation of care. Even though odds of escalation of care are higher with abnormal TcpCO₂ (OR 1.92), this difference did not reach statistical significance. pCO₂ can provide additive information for non-invasive clinical monitoring of children requiring varying respiratory support; however, it does not provide predictive value for escalation or de-escalation of care.

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

INTRODUCTION

Arterial 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.

OBJECTIVE

To examine the use of PetCO₂ and PtcCO₂ as PaCO₂ surrogates in awake children.

METHODS

A 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.

RESULTS

Sixty-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.

CONCLUSION

PtcCO₂ 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.

Transcutaneous carbon dioxide pattern and trend over time in preterm infants

BACKGROUND

Chronic lung disease remains a burden for extremely preterm infants. The changes in ventilation over time and optimal ventilatory management remains unknown. Newer, non-invasive technologies provide insight into these patterns.

METHODS

This single-center prospective cohort study enrolled infants ≤32 0/7 weeks. We obtained epochs of transcutaneous carbon dioxide (TcCO₂) measurements twice each week to describe the pattern of hypercarbia throughout their hospitalization.

RESULTS

Patterns of hypercarbia varied based on birth gestational age and post-menstrual age (PMA) (p = 0.03), regardless of respiratory support. Infants receiving the most respiratory support had values 16-21 mmHg higher than those on room air (p < 0.001). Infants born at the youngest gestational ages had the greatest total change but the rate of change was slower (p = 0.049) compared to infants born at later gestational ages. All infants had TcCO₂ values stabilize by 31-33 weeks PMA, when values were not significantly different compared to discharge. No rebound was observed when infants weaned off invasive support.

CONCLUSIONS

Hypercarbia improves as infants approached 31-33 weeks PMA. Hypercarbia was the highest in the most immature infants and improved with age and growth despite weaning respiratory support.

IMPACT

This study describes the evolution of hypercarbia as very preterm infants grow and develop. The pattern of ventilation is significantly different depending on the gestational age at birth and post-menstrual age. Average transcutaneous carbon dioxide (TCO₂) decreased over time as infants became more mature despite weaning respiratory support. This improvement was most significant in infants born at the lowest gestational ages.

Comparing the novel microstream and the traditional mainstream method of end-tidal CO2 monitoring with respect to PaCO2 as gold standard in intubated critically ill children

The objective of this study was to evaluate a novel microstream method by comparison with PaCO₂ and the more standard mainstream capnometer in intubated pediatric patients. We hypothesized that the novel microstream method would superior compared to the traditional mainstream method in predicting PaCO₂. This was a prospective single-center comparative study. The study was carried out on 174 subjects with a total of 1338 values for each method. Data were collected prospectively from mainstream and microstream capnometer simultaneously and compared with PaCO₂ results. Although both mainstream PetCO₂ (mainPetCO₂) and microstream PetCO₂ (microPetCO₂) were moderately correlated (r = 0.63 and r = 0.68, respectively) with PaCO₂ values, mainPetCO₂ was in better agreement with PaCO₂ in all subjects (bias ± precision values of 3.8 ± 8.9 and 7.3 ± 8.2 mmHg, respectively). In those with severe pulmonary disease, the mainPetCO₂ and microPetCO₂ methods were highly correlated with PaCO₂ (r = 0.80 and r = 0.81, respectively); however, the biases of both methods increased (14.8 ± 9.1 mmHg and 16.2 ± 9.0 mmHg, respectively). In cases with increased physiologic dead space ventilation, the agreement levels of mainPetCO₂ and microPetCO₂ methods became distorted (bias ± precision values of 20.9 ± 11.2 and 25.0 ± 11.8 mm Hg, respectively) even though mainPetCO₂ and microPetCO₂ were highly correlated (r = 0.78 and r = 0.78, respectively). It was found that the novel microstream capnometer method for PetCO₂ measurements provided no superiority to the traditional mainstream method. Both capnometer methods may be useful in predicting the trend of PaCO₂ due to significant correlations with the gold standard measurement in cases with severe pulmonary disease or increased physiological dead space –despite reduced accuracy.

Respiratory Monitoring: Current State of the Art and Future Roads

In this article, we present current methodologies, available technologies, and demands for monitoring various respiratory parameters. We discuss the importance of noninvasive techniques for remote and continuous monitoring and challenges involved in the current "smart and connected health" era. We conducted an extensive literature review on the medical significance of monitoring respiratory vital parameters, along with the current methods and solutions with their respective advantages and disadvantages. We discuss the challenges of developing a noninvasive, wearable, wireless system that continuously monitors respiration parameters and opportunities in the field and then determines the requirements of a state-of-the-art system. Noninvasive techniques provide a significant amount of medical information for a continuous patient monitoring system. Contact methods offer more advantages than non-contact methods; however, reducing the size and power of contact methods is critical for enabling a wearable, wireless medical monitoring system. Continuous and accurate remote monitoring, along with other physiological data, can help caregivers improve the quality of care and allow patients greater freedom outside the hospital. Such monitoring systems could lead to highly tailored treatment plans, shorten patient stays at medical facilities, and reduce the cost of treatment.

Transcutaneous CO2 Monitoring in Children Undergoing Tonsillectomy for Sleep Disordered Breathing

OBJECTIVES/HYPOTHESIS

Children undergoing tonsillectomy for sleep-disordered breathing are at risk for respiratory compromise when narcotics are administered. Severe complications resulting from hypoxia can include neuro-devastation and death. The objective of this prospective study was to evaluate the feasibility, accuracy, and utility of transcutaneous carbon dioxide (tcPCO2) monitoring during and after adenotonsillectomy.

STUDY DESIGN

Prospective, Observational study.

METHODS

Twenty-nine children with sleep-disordered breathing scheduled for adenotonsillectomy were included in the study. Peri-operative measurements of tcPCO2 were compared against a single venous blood sample (PaCO2) and end-tidal (ET) CO2. The differences between ETCO2, tcPCO2 measures, and PaCO2 were examined using non-paired t-tests and linear regression. Parameters from PSG were recorded and associations with tcPCO2 values were performed using linear regression analysis. Group comparisons were made between pre-, intra-, and post-operative tcPCO2 measurements.

RESULTS

Similar to ETCO2, there was good correlation of tcPCO2 to PaCO2. Children with lower oxygen (O2) saturation nadirs had higher peak CO2 levels during surgery and spent a greater proportion of time with CO2 > 50 mmHg in the recovery room (P < .01 and P < .08). Other PSG measures (apnea-hypopnea index, O2 desaturation index, and peak CO2) did not have any significant correlation. Frequent episodes of hypercapnia were noted intra- and post-operatively and mean tcPCO2 values during both periods were significantly higher than baseline (P < .001).

CONCLUSIONS

tcPCO2 monitoring is viable in children undergoing adenotonsillectomy and can provide a good estimate of hypoventilation. tcPCO2 measurements may have particular benefit in the post-operative setting and may assist in identifying children at greater risk for respiratory complications.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:1410-1415, 2021.

Continuous transcutaneous carbon-dioxide monitoring to avoid hypercapnia in complex catheter ablations under conscious sedation

BACKGROUND

Ablation of complex cardiac arrhythmias requires an immobilized patient. For a successful and safe intervention and for patient comfort, this can be achieved by conscious sedation. Administered sedatives and analgesics have respiratory depressant side effects and require close monitoring. We investigated the feasibility and accuracy of additional, continuous transcutaneous carbon-dioxide partial pressure (tpCO₂) measurement during conscious sedation in complex electrophysiological catheter ablation procedures.

METHOD

We evaluated the accuracy and additional value of continuous tpCO₂ detection by application of a Severinghaus electrode in comparison to arterial and venous blood gas analyses.

RESULTS

We included 110 patients in this prospective observational study. Arterial pCO₂ (paCO₂) and tpCO₂ showed good correlation throughout the procedures (r = 0.60-0.87, p < 0.005). Venous pCO₂ (pvCO₂) were also well correlated to transcutaneous values (r = 0.65-0.85, p < 0.0001). Analyses of the difference of pvCO₂ and tpCO₂ measurements showed a tolerance within <10 mmHg in up to 96-98% of patients. Hypercapnia (pCO₂ < 70 mmHg) was detected more likely and earlier by continuous tpCO₂ monitoring compared to half-hourly pvCO₂ measurements.

CONCLUSION

Continuous tpCO₂ monitoring is feasible and precise with good correlation to arterial and venous blood gas carbon-dioxide analysis during complex catheter ablations under conscious sedation and may contribute to additional safety.

Comparison of arterial CO2 estimation by end-tidal and transcutaneous CO2 measurements in intubated children and variability with subject related factors

Transcutaneous PCO₂ (P_TCCO₂) and end-tidal PCO₂ (P_ETCO₂) measurement methods serve as alternatives to arterial PCO₂ (PaCO₂), providing continuous non-invasive monitoring. The objective of this study was to evaluate the P_TCCO₂ and P_ETCO₂ methods with actual PaCO₂ levels, and to assess the variability of measurements in relation to subject-related factors, such as skin and subcutaneous adipose tissue thickness and presence of pulmonary diseases. P_TCCO₂, P_ETCO₂ and PaCO₂ were measured at the same time in intubated pediatric subjects. Subjects' demographic characteristics, clinical features, laboratory parameters, skin and subcutaneous adipose tissue thickness were identified. The study was carried out on 102 subjects with a total of 1118 values for each method. In patients with non-pulmonary disease, the mean difference between P_TCCO₂ and PaCO₂ was - 0.29 mmHg (± 6.05), while it was 0.44 mmHg (± 6.83) bias between P_ETCO₂ and PaCO₂. In those with pulmonary diseases, the mean difference between P_TCCO₂ and PaCO₂ was - 1.27 mmHg (± 8.32), while it was - 4.65 mmHg (± 9.01) between P_ETCO₂ and PaCO₂. Multiple linear regression demonstrated that increased subcutaneous adipose tissue thickness, core body temperature and inotropic index were related with higher P_TCCO₂ values relative to the actual PCO₂ values. Other factors, such as skin tissue thickness, presence of pulmonary disease, measurement location and measurement times were non-significant. The P_TCCO₂ method has higher reliability than the P_ETCO₂ method, and P_TCCO₂ measurements are not influenced by most subject-related factors; however, core body temperature, inotropic index and subcutaneous adipose tissue thickness can lead to significant differences in PCO₂ measurement.

Non-invasive carbon dioxide monitoring in patients with cystic fibrosis during general anesthesia: end-tidal versus transcutaneous techniques

INTRODUCTION

The gold standard for measuring the partial pressure of carbon dioxide remains arterial blood gas (ABG) analysis. For patients with cystic fibrosis undergoing general anesthesia or polysomnography studies, continuous non-invasive carbon dioxide monitoring may be required. The current study compares end-tidal (ETCO₂), transcutaneous (TCCO₂), and capillary blood gas carbon dioxide (Cap-CO₂) monitoring with the partial pressure of carbon dioxide (PaCO₂) from an ABG in patients with cystic fibrosis.

METHODS

Intraoperatively, a single CO₂ value was simultaneously obtained using ABG (PaCO₂), capillary (Cap-CO₂), TCCO₂, and ETCO₂ techniques. Tests for correlation (Pearson's coefficient) and agreement (Bland-Altman analysis) were performed. Data were further stratified into two subgroups based on body mass index (BMI) and percent predicted forced expiratory volume in 1 s (FEV₁%). Additionally, the absolute difference in the TCCO₂, ETCO₂, and Cap-CO₂ values versus PaCO₂ was calculated. The mean ± SD differences were compared using a paired t test while the number of times the values were ≤ 3 mmHg and ≤ 5 mmHg from the PaCO₂ were compared using a Fishers' exact test.

RESULTS

The study cohort included 47 patients (22 males, 47%) with a mean age of 13.4 ± 7.8 years, median (IQR) BMI of 18.7 kg/m² (16.7, 21.4), and mean FEV₁% of 87.3 ± 18.3%. Bias (SD) was 4.8 (5.7) mmHg with Cap-CO₂ monitoring, 7.3 (9.7) mmHg with TCCO₂ monitoring, and 9.7 (7.7) mmHg with ETCO₂ monitoring. Although there was no difference between the degree of bias in the population as a whole, when divided based on FEV₁% and BMI, there was greater bias with ETCO₂ in patients with a lower FEV₁% and a higher BMI. The Cap-CO₂ vs. PaCO₂ difference was 5.2 ± 5.3 mmHg (SD), with 16 (48%) ≤ 3 mmHg and 20 (61%) ≤ 5 mmHg from the ABG value. The TCCO₂-PaCO₂ difference was 9.1 ± 7.2 mmHg (SD), with 11 (27%) ≤ 3 mmHg and 15 (37%) ≤ 5 mmHg from the ABG value. The ETCO₂-PaCO₂ mean difference was 11.2 ± 7.9 mmHg (SD), with 5 (12%) ≤ 3 mmHg and 11 (26%) ≤ 5 mmHg from the ABG value.

CONCLUSIONS

While Cap-CO₂ most accurately reflects PaCO₂ as measured on ABG, of the non-invasive continuous monitors, TCCO₂ was a more accurate and reliable measure of PaCO₂ than ETCO₂, especially in patients with worsening pulmonary function (FEV₁% ≤ 81%) and/or a higher BMI (≥ 18.7 kg/m²).

Randomized clinical trial of high concentration versus titrated oxygen use in pediatric asthma

OBJECTIVE

To compare the effects of high concentration to titrated oxygen therapy (HCOT) on transcutaneous carbon dioxide (PtCO₂ ) level in pediatric asthma exacerbation. Titrated oxygen therapy (TOT) in acute asthma will avoid a rise in PtCO ₂ in the pediatric population.

METHOD

The study design is a prospective, randomized, clinical trial comparing HCOT (maintain SpO2 92-95%) while being treated for asthma exacerbation in the emergency department (ED).

INCLUSION CRITERIA

2 to 18 years, previously diagnosed asthma with acute exacerbation (asthma score >5). PtCO₂ and asthma scores were measured at 0, 20, 40, 60 minutes and then every 30 minutes until disposition decision. The primary outcome was a change in PtCO ₂ . Secondary outcomes were admission rate and change in asthma score.

RESULTS

A total of 96 patients were enrolled in the study with a mean age of 8.27 years; 49 in HCOT and 47 in the TOT group. The 0 minute PtCO₂ was similar (35.33 + 3.88 HCOT vs 36.66 + 4.69 TOT, P = 0.13); whereas, the 60 minutes PtCO ₂ was higher in the HCOT (38.08 + 5.11 HCOT vs 35.51 + 4.57 TOT, P = 0.01). The asthma score was similar at 0 minute (7.55 + 1.34 HCOT vs 7.30 + 1.18 TOT, P = 0.33); whereas, the 60 minutes asthma score was lower in the TOT (4.71 + 1.38 HCOT vs 3.57 + 1.25 TOT, P = 0.0001). The rate of admission to the hospital was 40.5% in HCOT vs 25.5% in the TOT (P = 0.088).

CONCLUSIONS

HCOT in pediatric asthma exacerbation leads to significantly higher carbon dioxide levels, which increases asthma scores and trends towards the increasing rate of admission. Larger studies are needed to explore this association.

The Society for Pediatric Anesthesia recommendations for the use of opioids in children during the perioperative period

Opioids have long held a prominent role in the management of perioperative pain in adults and children. Published reports concerning the appropriate, and inappropriate, use of these medications in pediatric patients have appeared in various publications over the last 50 years. For this document, the Society for Pediatric Anesthesia appointed a taskforce to evaluate the available literature and formulate recommendations with respect to the most salient aspects of perioperative opioid administration in children. The recommendations are graded based on the strength of the available evidence, with consensus of the experts applied for those issues where evidence is not available. The goal of the recommendations was to address the most important issues concerning opioid administration to children after surgery, including appropriate assessment of pain, monitoring of patients on opioid therapy, opioid dosing considerations, side effects of opioid treatment, strategies for opioid delivery, and assessment of analgesic efficacy. Regular updates are planned with a re-release of guidelines every 2 years.

Transcutaneous CO2 versus end-tidal CO2 in neonates and infants undergoing surgery: a prospective study

Aim: End-tidal CO2 (EtCO2) is the standard in operative care along with pulse oximetry for ventilation assessment. It is known to be less accurate in the infant population than in adults. Many neonatal intensive care units (NICU) have converted to utilizing transcutaneous CO2 (tcPCO2) monitoring. This study aimed to compare perioperative EtCO2 to tcPCO2 in the pediatric perioperative population specifically below 10 kg, which encompasses neonates and some infants. Methods: After IRB approval and parental written informed consent, we enrolled neonates and infants weighing less than 10 kg, who were scheduled for elective surgery with endotracheal tube under general anesthesia. PCO2 was monitored with EtCO2 and with tcPCO2. Venous blood gas (PvCO2) samples were drawn at the end of the anesthetic. We calculated a mean difference of EtCO2 minus PvCO2 (Delta EtCO2), and tcPCO2 minus PvCO2 (Delta tcPCO2) from end-of-case measurements. The mean differences in the NICU and non-NICU patients were compared by t-tests and Bland-Altman analysis. Results: Median age was 10.9 weeks, and median weight was 4.4 kg. NICU (n=6) and non-NICU (n=14) patients did not differ in PvCO2. Relative to the PvCO2, the Delta EtCO2 was much greater in the NICU compared to the non-NICU patients (-28.1 versus -9.8, t=3.912, 18 df, P=0.001). Delta tcPCO2 was close to zero in both groups. Although both measures obtained simultaneously in the same patients agreed moderately with each other (r =0.444, 18 df, P=0.05), Bland-Altman plots indicated that the mean difference (bias) in EtCO2 measurements differed significantly from zero (P<0.05). Conclusions: EtCO2 underestimates PvCO2 values in neonates and infants under general anesthesia. TcPCO2 closely approximates venous blood gas values, in both the NICU and non-NICU samples. We, therefore, conclude that tcPCO2 is a more accurate measure of operative PvCO2 in infants, especially in NICU patients.

Response time of indirectly accessed gas exchange depends on measurement method

Noninvasive techniques are routinely used for assessment of tissue effects of lung ventilation. However, comprehensive studies of the response time of the methods are scarce. The aim of this study was to compare the response time of noninvasive methods for monitoring of gas exchange to sudden changes in the composition of the inspired gas. A prospective experimental study with 16 healthy volunteers was conducted. A ventilation circuit was designed that enabled a fast change in the composition of the inspiratory gas mixture while allowing spontaneous breathing. The volunteers inhaled a hypoxic mixture, then a hypercapnic mixture, a hyperoxic mixture and finally a 0.3% CO mixture. The parameters with the fastest response to the sudden change of O2 in inhaled gas were peripheral capillary oxygen saturation (SpO2) and regional tissue oxygenation (rSO2). Transcutaneous oxygen partial pressure (tcpO2) had almost the same time of reaction, but its time of relaxation was 2-3 times longer. End-tidal carbon dioxide (EtCO2) response time to change of CO2 concentration in inhaled gas was less than half in comparison with transcutaneous carbon dioxide partial pressure (tcpCO2). All the examined parameters and devices reacted adequately to changes in gas concentration in the inspiratory gas mixture.

Development and characterization of a point-of care rate-based transcutaneous respiratory status monitor

Blood gas measurements provide vital clinical information in critical care. The current "gold standard" for blood gas measurements involves obtaining blood samples, which can be painful and can lead to bleeding, thrombus formation, or infection. Mass transfer equilibrium-based transcutaneous blood gas monitors have been used since the 1970s, but they require heating the skin to ≥42 °C to speed up the transcutaneous gas diffusion. Thus, these devices have a potential risk for skin burns. Here we report a new generation of noninvasive device for respiratory status assessment. Instead of waiting for mass transfer equilibrium, the blood gas levels are monitored by measuring the transcutaneous diffusion rate, which is proportional to blood gas concentration. The startup time of this device is almost independent of skin temperature, so the measurement can be made at any body temperature. The test results show that this device can track the blood gas levels quickly even at normal body temperature.

Correlation and Interchangeability of Venous and Capillary Blood Gases in Non-Critically Ill Neonates

BACKGROUND

Venous blood gas (VBG) is frequently used in the neonatal unit as alternative for capillary blood gas (CBG). However, studies reporting correlation are conflicting and data on interchangeability in neonates are lacking.

OBJECTIVE

We investigated the correlation and interchangeability of the components between VBG and CBG in infants admitted to the neonatal intensive care unit.

METHODS

In a prospective study in the neonatal unit in Leiden University Medical Center (Netherlands), simultaneously VBG and CBG were withdrawn in neonates when both venous puncture and intravenous access as blood gas monitoring was indicated. From each blood gas analysis, a Pearson correlation, intraclass correlation, and Bland-Altman analysis was performed. Clinically acceptable difference for each blood gas value was defined up-front by means of an absolute difference: pH ± 0.05; partial pressure of carbon dioxide (pCO₂) (±0.67 kPa = 5 mmHg); partial pressure of oxygen (pO₂) (±0.67 kPa = 5 mmHg); base excess ± 3 mmol/l; and bicarbonate (HCO₃^-) ± 3 mmol/l.

RESULTS

In 93 patients [median gestational age 31 (IQR 29-34) weeks], 193 paired samples of VBG and CBG were collected. The Pearson correlation between VBG and CBG was very strong for pH (r = 0.79; P < 0.001), BE (r = 0.90; P < 0.001) and bicarbonate (r = 0.87; P < 0.001); strong for pCO₂ (r = 0.68; P < 0.001); and moderate for pO₂ (r = 0.31; P < 0.001). The percentage of the interchangeability within our acceptable absolute difference for pH was 88%, pCO₂ 72%, pO₂ 55%, BE 90%, and bicarbonate 94%.

CONCLUSION

VBG and CBG in neonates are well correlated and mostly interchangeable, except for pO₂.

Poor performance of main-stream capnography in newborn infants during general anesthesia

BACKGROUND

Endtidal (ET) measurement of carbon dioxide is well established for intraoperative respiratory monitoring of adults and children, but the method's accuracy for intraoperative use in small newborn infants has been less extensively investigated.

AIMS

The aim of this study was to compare carbon dioxide from ET measurements with arterialized capillary blood samples in newborn infants during general anesthesia and surgery.

METHODS

Endtidal carbon dioxide was continuously measured during anesthesia and surgery and compared with simultaneous blood gas analyses obtained from capillary blood samples. Fifty-nine sample sets of ET to blood gas carbon dioxide were obtained from 23 prospectively enrolled infants with a gestational age of 23-41 weeks and a birth weight of 670-4110 g.

RESULTS

Endtidal levels of carbon dioxide were considerably lower in all sample sets and only 4/23 individual ET-blood gas sample pairs differed <7.5 mm Hg (1 kPa). Bland-Altman analysis indicated a poor agreement with a bias of -13 ± 7 mm Hg and a precision of ±14 mm Hg. The performance of ET measurements was particularly poor in infants weighing below 2.5 kg, in infants in need of respiratory support prior to anesthesia, and when the true (blood gas) carbon dioxide level was high, above 45 mm Hg.

CONCLUSION

Main-stream capnography during anesthesia and surgery correlated poorly to blood gas values in small and/or respiratory compromised infants. We conclude that caution should be exercised when relying solely on ET measurements to guide mechanical ventilation in the OR.

Transcutaneous PCO2 Monitoring in Newborn Infants During General Anesthesia Is Technically Feasible

Published ahead of print July 26, 2016.

BACKGROUND:

Transcutaneous (TC) measurement of Pco₂ (TC Pco₂) is a well-established method to monitor assisted ventilation in neonatal intensive care, but its use in the operating room is limited, and the data regarding its performance during general anesthesia of the newborn are lacking. The aim of this study is to evaluate the performance of continuous TC Pco₂ monitoring during general anesthesia in newborn infants.

METHODS:

Infants (n = 25) with a gestational age of 23 to 41 weeks and a birth weight of 548 to 4114 g were prospectively enrolled. During general anesthesia and surgery, TC Pco₂ was measured continuously and recorded at 1-minute intervals. Five-minute mean values were compared with simultaneously obtained blood gas (BG) analyses of Pco₂. Only the first paired TC and BG samples were used in this analysis. We defined precision as 2.1 times the standard deviation of the difference of the 2 samples. P < .01 was considered statistically significant.

RESULTS:

We obtained samples from 25 infants. The difference between TC and BG was 0.3 ± 0.7 kPa (mean ± standard deviation) giving a precision of 1.47 kPa. Nineteen of twenty-five (76%) sample pairs displayed a difference of <1 kPa (99% confidence interval, 48%–92%, P = .016). The difference in paired samples was similar for different gestational and postnatal ages and did not appear to be affected by electrocautery.

CONCLUSIONS:

In this small study, we did not demonstrate that TC CO₂ monitoring was accurate at P < .01. This partly reflects the small size of the study, resulting in wide 99% confidence bounds.

The efficacy of dexmedetomidine-remifentanil versus dexmedetomidine-propofol in children undergoing flexible bronchoscopy: A retrospective trial

Flexible bronchoscopy has been more and more used for diagnosis and management diseases of respiratory system in pediatrics. Previous studies have reported that remifentanil (RF) and propofol are safe and effective for flexible bronchoscopy in adults, however, there have no trials evaluate the efficacy of DEX-RF versus dexmedetomidine-propofol in children undergoing flexible bronchoscopy.We divided 123 children undergoing flexible bronchoscopy with DEX-RF or dexmedetomidine-propofol into 2 groups: Group DR (n = 63, DEX infusion at 1.0 μg kg for 10 minutes, then adjusted to 0.5-0.7 μg kg h; RF infusion at 1.0 μg kg for 5 minutes, then adjusted to 0.05-0.2 μg kg min), Group DP (n = 60, DEX infusion at 1.0 μg kg for 10 minutes, then adjusted to 0.5-0.7 μg kg h; propofol infusion at 10 μg kg for 5 minutes, then adjusted to 0.05-0.1 μg kg min). Ramsay sedation scale of the 2 groups was maintained at 3. Anesthesia onset time; total number of intraoperative patient movements; hemodynamics; total cumulative dose of DEX; amount of and time to first-dose rescue midazolam and lidocaine; postoperative recovery time; adverse events; and bronchoscopist satisfaction score were recorded.Anesthesia onset time was significantly shorter in DP (8.22 ± 2.48 vs 12.25 ± 6.43 minutes, respectively, for DP, DR, P = 0.015). The perioperative hemodynamic profile was more stable in DR than DP group. More children moved during flexible bronchoscopy in DP group (P = 0.009). Total dose of rescue midazolam and lidocaine was significantly higher in DR than in DP (P < 0.001). Similarly, the time to first dose of rescue midazolam and lidocaine was significantly longer in DP than in DR (P < 0.001). Total cumulative dose of DEX was more in DR than DP group (P < 0.001). The time to recovery for discharge from the postanesthesia care unit (PACU) was significantly shorter in DP than in DR group (P < 0.001). The bronchoscopist-satisfaction scores were higher for DR than DP (P = 0.036). There were significant differences between the 2 groups in terms of the overall incidence of hypertension, tachycardia, and hypoxemia (P < 0.05).Although underwent longer recovery time and more incidence of rescue scheme, DEX-RF resulted in more stable hemodynamic profiles and bronchoscopist-satisfaction scores, lesser patient movements, and can hence be more effectively used in children undergoing flexible bronchoscopy than dexmedetomidine-propofol.

Noninvasive Estimation of Arterial CO2 From End-Tidal CO2 in Mechanically Ventilated Children: The GRAeDIENT Pilot Study

OBJECTIVES

The aim of our pilot study was to develop a model to better predict Paco2 in mechanically ventilated children using noninvasive parameters including volumetric capnography.

DESIGN

Prospective clinical pilot study.

SETTING

Level III PICU.

PATIENTS

Sixty-five mechanically ventilated children.

INTERVENTIONS

None.

MATERIALS AND METHODS

We conducted a prospective clinical pilot study that included all children admitted to the PICU (< 18 yr; weight, > 3 kg; mechanically ventilated, > 6 hr; with an arterial line). A predictive model for PaCO2 was developed using linear multivariable regression. Among the data collected in PICU patients, candidate predictors of PaCO2 were defined by a panel of experts and included end-tidal partial pressure of carbon dioxide, ventilation parameters, and data resulting from the analysis of volumetric capnogram recorded 5 minutes before an arterial blood gas. Children with tidal volume less than 30 mL were excluded because of technical limits.

RESULTS

A total of 65 children (43 boys, 65%) (65 [21-150] mo old) were analyzed. By linear multivariable regression, the best model included the mean airway pressure, end-tidal partial pressure of carbon dioxide, FIO2, and the capnographic index with an R equal to 0.90, p value less than 0.001. After correction, 95% (n = 62) of children had an estimated PaCO2 at ± 5 mm Hg.

CONCLUSION

Our model developed provides an accurate estimation of the PaCO2 using end-tidal CO2 and noninvasive variables. Studies are needed to validate the equation in PICUs.

Alveolar ventilation in children during flexible bronchoscopy

BACKGROUND

Hypoxia and hypercarbia complicate flexible bronchoscopy (FB). Unlike oxygenation by pulse-oximetry, alveolar ventilation is not routinely monitored during FB. The aim of this study was to investigate ventilation in children undergoing FB by measuring carbon-dioxide (CO₂ ) levels using the transcutaneous technique.

METHODS

Children admitted for FB were recruited. In addition to routine monitoring, transcutaneous CO₂ (TcCO₂ ) levels were recorded. All were sedated using the same protocol.

RESULTS

Ninety-five children were studied. There was no association between peak TcCO₂ or rise in TcCO₂ and age, weight percentile, bronchoscope size, or diagnosis. Median baseline TcCO₂ was 36 mmHg (IQR 32,40), median peak TcCO₂ was 51 mmHg (IQR 43,62) with median TcCO₂ rise of 17 mmHg (IQR 6.5,23.7). A rise of 15 mmHg or higher was recorded in 55% (n = 52) patients. Children requiring total propofol dose over 3.5 mg/kg had a significantly higher TcCO₂ peak of 57.6 mmHg (IQR 47.8,66.7) compared to 47.1 mmHg (IQR 40,57) (P = 0.004) and a higher rise in TcCO₂ 22.5 mmHg (IQR 17,33.9) compared to 13.6 mmHg (6,22) (P = 0.001). Results were not affected by intranasal midazolam and broncho-alveolar lavage. No complications were reported. Non clinically significant (i.e., not lower than 90%) brief drops in oxygen saturation were observed.

CONCLUSIONS

A large proportion of children undergoing FB have significant alveolar hypoventilation indicated by a rise in TcCO₂ . Monitoring ventilation with TcCO₂ is feasible and should be added during FB particularly in cases that are expected to require large amounts of sedation and patients susceptible to complications from respiratory acidosis. Pediatr Pulmonol. 2016;51:1177-1182. © 2016 Wiley Periodicals, Inc.

Accuracy of Transcutaneous Carbon Dioxide Measurement in Premature Infants

Background. In premature infants, maintaining blood partial pressure of carbon dioxide (pCO₂) value within a narrow range is important to avoid cerebral lesions. The aim of this study was to assess the accuracy of a noninvasive transcutaneous method (TcpCO₂), compared to blood partial pressure of carbon dioxide (pCO₂). Methods. Retrospective observational study in a tertiary neonatal intensive care unit. We analyzed the correlation between blood pCO₂ and transcutaneous values and the accuracy between the trends of blood pCO₂ and TcpCO₂ in all consecutive premature infants born at <33 weeks' gestational age. Results. 248 infants were included (median gestational age: 29 + 5 weeks and median birth weight: 1250 g), providing 1365 pairs of TcpCO₂ and blood pCO₂ values. Pearson's R correlation between these values was 0.58. The mean bias was −0.93 kPa with a 95% confidence limit of agreement of −4.05 to +2.16 kPa. Correlation between the trends of TcpCO₂ and blood pCO₂ values was good in only 39.6%. Conclusions. In premature infants, TcpCO₂ was poorly correlated to blood pCO₂, with a wide limit of agreement. Furthermore, concordance between trends was equally low. We warn about clinical decision-making on TcpCO₂ alone when used as continuous monitoring.

Diagnostic accuracy of capnography during high-frequency ventilation in neonatal intensive care units

BACKGROUND AND OBJECTIVE

High-frequency ventilation (HFV) is a powerful tool for CO2 elimination, and thus requires careful monitoring of CO2 . Our aim was to assess the diagnostic accuracy (correlation, agreement, and trending) of continuous distal capnography (dCap) with PaCO2 in infants ventilated with HFV.

DESIGN

This was a prospective, observational, multicenter study. dCap was compared with simultaneous PaCO2 ("gold standard") drawn from indwelling arterial line for patient care in term and preterm infants ventilated with HFV. dCap was obtained via the side-port of a double-lumen endotracheal-tube by a Microstream capnograph with specially designed software for HFV.

RESULTS

Twenty-four infants participated in the study (median [range] gestational age [GA]: 26.8 [23.6-38.6] weeks). Analysis included 332 measurements. dCap was in correlation (r = 0.70, P < 0.001) but with less than adequate agreement (mean difference ± SD of the differences: -11.7 ± 10.3 mmHg) with PaCO2 . Comparable findings were found in the subgroup of infants <1,000 g (n = 240 measurements). Correlations were maintained in severe lung disease. Changes in dCap and in PaCO2 for consecutive measurements within each patient were correlated (r = 0.63, P < 0.001). Area under the receiver operating curves (ROC) for dCap to detect high (>60 mmHg) or low (<30 mmHg) PaCO2 was 0.83 (CI: 0.76-0.90) and 0.88 (CI: 0.79-0.97), respectively; P < 0.001.

CONCLUSIONS

Our prospective study suggests that continuous dCap in infants ventilated with HFV may be helpful for trends and alarm for unsafe levels of PaCO2 . dCap is only a complimentary tool and cannot replace PaCO2 sampling because the agreement between these measurements was less than adequate.

[Respiratory monitoring of pediatric patients in the Intensive Care Unit]

Respiratory monitoring plays an important role in the care of children with acute respiratory failure. Therefore, its proper use and correct interpretation (recognizing which signals and variables should be prioritized) should help to a better understanding of the pathophysiology of the disease and the effects of therapeutic interventions. In addition, ventilated patient monitoring, among other determinations, allows to evaluate various parameters of respiratory mechanics, know the status of the different components of the respiratory system and guide the adjustments of ventilatory therapy. In this update, the usefulness of several techniques of respiratory monitoring including conventional respiratory monitoring and more recent methods are described. Moreover, basic concepts of mechanical ventilation, their interpretation and how the appropriate analysis of the information obtained can cause an impact on the clinical management of the patient are defined.

Impact of Continuous Capnography in Ventilated Neonates: A Randomized, Multicenter Study

OBJECTIVE

To compare the time spent within a predefined safe range of CO2 (30-60 mmHg) during conventional ventilation between infants who were monitored with distal end-tidal CO2 (dETCO2, or capnography) and those who were not.

STUDY DESIGN

For this randomized, controlled multicenter study, ventilated infants with a double-lumen endotracheal tube were randomized to 1 of 2 groups: the open (monitored) group, in which data from the capnograph were recorded, displayed to the medical team, and used for patient care, and the masked group, in which data from the capnograph were recorded. However, the measurements were masked and not available for patient care. dETCO2 was compared with PaCO2 measurements recorded for patient care.

RESULTS

Fifty-five infants (25 open, 30 masked) participated in the study (median gestational age, 28.6 weeks; range, 23.5-39.0 weeks). The 2 groups were comparable. dETCO2 was in good correlation (r = 0.73; P < .001) and adequate agreement (mean ± SD of the difference, 3.0 ± 8.5 mmHg) with PaCO2. Compared with infants in the masked group, those in the monitored group had significantly (P = .03) less time with an unsafe dETCO2 level (high: 3.8% vs 8.8% or low: 3.8% vs 8.9%). The prevalence of intraventricular hemorrhage or periventricular leukomalacia rate was lower in the monitored group (P = .02) and was significantly (P < .05) associated with the independent factors dETCO2 monitoring and gestational age.

CONCLUSION

Continuous dETCO2 monitoring improved control of CO2 levels within a safe range during conventional ventilation in a neonatal intensive care unit.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01572272.

Can transcutaneous carbon dioxide pressure be a surrogate of blood gas samples for spontaneously breathing emergency patients? The ERNESTO experience

BACKGROUND

It is known that the arterial carbon dioxide pressure (PaCO2) is useful for emergency physicians to assess the severity of dyspnoeic spontaneously breathing patients. Transcutaneous carbon dioxide pressure (PtcCO2) measurements could be a non-invasive alternative to PaCO2 measurements obtained by blood gas samples, as suggested in previous studies. This study evaluates the reliability of a new device in the emergency department (ED).

METHODS

We prospectively included patients presenting to the ED with respiratory distress who were breathing spontaneously or under non-invasive ventilation. We simultaneously performed arterial blood gas measurements and measurement of PtcCO2 using a sensor placed either on the forearm or the side of the chest and connected to the TCM4 CombiM device. The agreement between PaCO2 and PtcCO2 was assessed using the Bland-Altman method.

RESULTS

Sixty-seven spontaneously breathing patients were prospectively included (mean age 70 years, 52% men) and 64 first measurements of PtcCO2 (out of 67) were analysed out of the 97 performed. Nineteen patients (28%) had pneumonia, 19 (28%) had acute heart failure and 19 (28%) had an exacerbation of chronic obstructive pulmonary disease. Mean PaCO2 was 49 mm Hg (range 22-103). The mean difference between PaCO2 and PtcCO2 was 9 mm Hg (range -47 to +54) with 95% limits of agreement of -21.8 mm Hg and 39.7 mm Hg. Only 36.3% of the measurement differences were within 5 mm Hg.

CONCLUSIONS

Our results show that PtcCO2 measured by the TCM4 device could not replace PaCO2 obtained by arterial blood gas analysis.

Noninvasive Measurement of Carbon Dioxide during One-Lung Ventilation with Low Tidal Volume for Two Hours: End-Tidal versus Transcutaneous Techniques

BACKGROUND

There may be significant difference between measurement of end-tidal carbon dioxide partial pressure (PetCO2) and arterial carbon dioxide partial pressure (PaCO2) during one-lung ventilation with low tidal volume for thoracic surgeries. Transcutaneous carbon dioxide partial pressure (PtcCO2) monitoring can be used continuously to evaluate PaCO2 in a noninvasive fashion. In this study, we compared the accuracy between PetCO2 and PtcCO2 in predicting PaCO2 during prolonged one-lung ventilation with low tidal volume for thoracic surgeries.

METHODS

Eighteen adult patients who underwent thoracic surgeries with one-lung ventilation longer than two hours were included in this study. Their PetCO2, PtcCO2, and PaCO2 values were collected at five time points before and during one-lung ventilation. Agreement among measures was evaluated by Bland-Altman analysis.

RESULTS

Ninety sample sets were obtained. The bias and precision when PtcCO2 and PaCO2 were compared were 4.1 ± 6.5 mmHg during two-lung ventilation and 2.9 ± 6.1 mmHg during one-lung ventilation. Those when PetCO2 and PaCO2 were compared were -11.8 ± 6.4 mmHg during two-lung ventilation and -11.8 ± 4.9 mmHg during one-lung ventilation. The differences between PtcCO2 and PaCO2 were significantly lower than those between PetCO2 and PaCO2 at all five time-points (p < 0.05).

CONCLUSIONS

PtcCO2 monitoring was more accurate for predicting PaCO2 levels during prolonged one-lung ventilation with low tidal volume for patients undergoing thoracic surgeries.

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

Abstract

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.

Background

Transcutaneous 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.

Methods

From 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.

Results

Ninety 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.

Conclusions

There 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.

Is there still a role for high-frequency oscillatory ventilation in neonates, children and adults?

Critically ill patients with respiratory pathology often require mechanical ventilation and while low tidal volume ventilation has become the mainstay of treatment, achieving adequate gas exchange may not be attainable with conventional ventilator modalities. In attempt to achieve gas exchange goals and also mitigate lung injury, high frequency ventilation is often implemented which couples low tidal volumes with sustained mean airway pressure. This manuscript presents the physiology of high-frequency oscillatory ventilation, reviews the currently available data on its use and provides strategies and approaches for this mode of ventilation.

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 transcutaneous and end-tidal carbon dioxide levels during inhalation sedation in volunteers

Measurement of end-tidal carbon dioxide (PETCO2) is useful because of its noninvasiveness, continuity, and response time when sudden changes in ventilation occur during inhalation sedation. We compared the accuracy of PETCO2 using a nasal mask and nasal cannula with the accuracy of transcutaneous carbon dioxide (TC-CO2) and determined which method is more useful during inhalation sedation in volunteers. We used a modified nasal mask (MNM) and modified nasal cannula (MNC) for measurement of PETCO2. The capnometer measured PETCO2 in the gas expired from the nasal cavity by means of two devices. The volunteers received supplemental O2 by means of each device at a flow rate of 6 L/min. After the volunteers lay quietly for 5 min with a supply of 100 % O2, they received supplemental N2O by means of each device at concentrations of 10, 20, and 25 % for 5 min and 30 % for 25 min. The correlation coefficient was poorer in the MNM than in the MNC, and the mean difference between TC-CO2 and PETCO2 in the MNM was greater than that in the MNC. The difference between the TC-CO2 and PETCO2 ranged from 3 to 6 mmHg in the MNM and from 2 to 5 mmHg in the MNC. The difference between two variables against the TC-CO2 and the CO2 waveforms obtained by means of the two devices were within the clinically acceptable range. Our two devices can provide continuous monitoring of PETCO2 with a supply of N2O/O2 in patients undergoing inhalation sedation.

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

Introduction

Transcutaneous 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.

Methods

From 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.

Results

90 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.

Conclusions

In 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.

A pragmatic approach to infants with Robin sequence: a retrospective cohort study and presence of a treatment algorithm

Objectives

Initial approaches to and treatments of infants with Robin sequence (RS) is diverse and inconsistent. The care of these sometimes critically ill infants involves many different medical specialties, which can make the decision process complex and difficult. To optimize the care of infants with RS, we present our institution’s approach and a review of the current literature.

Material and methods

A retrospective cohort study was conducted among 75 infants diagnosed with RS and managed at our institution in the 1996–2012 period. Additionally, the conducted treatment regimen in this paper was discussed with recent literature describing the approach of infants with RS.

Results

Forty-four infants (59 %) were found to have been treated conservatively. A significant larger proportion of nonisolated RS infants than isolated RS infants needed surgical intervention (53 vs. 25 %, p = .014). A mandibular distraction was conducted in 24 % (n = 18) of cases, a tracheotomy in 9 % (n = 7), and a tongue–lip adhesion in 8 % (n = 6). Seventy-seven percent of all infants had received temporary nasogastric tube feeding. The literature review of 31 studies showed that initial examinations and the indications to perform a surgical intervention varied and were often not clearly described.

Conclusions

RS is a heterogenic group with a wide spectrum of associated anomalies. As a result, the decisional process is challenging, and a multidisciplinary approach to treatment is desirable. Current treatment options in literature vary, and a more uniform approach is recommended.

Clinical Relevance

We provide a comprehensive and pragmatic approach to the analysis and treatment of infants with RS, which could serve as useful guidance in other clinics.

Monitoring Oxygenation and Gas Exchange in Neonatal Intensive Care Units: Current Practice in the Netherlands

BACKGROUND

Although recommendations in oxygenation and gas exchange monitoring in the neonatal intensive care unit (NICU) are available, little is known of the current practice.

AIM

To evaluate the current practice in oxygenation and gas exchange monitoring of the NICUs in the Netherlands.

METHODS

An online survey-based questionnaire concerning preferences and current practice of monitoring oxygenation and gas exchange was sent out to all 107 neonatal staff members (neonatologists, neonatal fellows, and physician assistants) of the 10 NICUs in the Netherlands.

RESULTS

The response rate was 42%. Pulse oximetry (PO), partial pressure of oxygen in arterial blood gas (paO2), and oxygen saturation in arterial blood gas (saO2) was used by, respectively, 100, 80, and 27% of the staff members for monitoring oxygenation. Of all staff members, 76% considered PO as the best parameter for monitoring oxygenation, 22% paO2, and 2% saO2. Blood gas, transcutaneous gas monitoring, endotracheal gas monitoring, and near-infrared spectroscopy was used by, respectively, 100, 82, 40, and 18% of the staff members for monitoring gas exchange. During endotracheal ventilation, 67% of the caregivers would exclusively accept arterial blood gas for gas exchange monitoring. In contrast, during non-invasive ventilation, 68% of the caregivers did not prefer arterial or capillary blood gas (CBG). CBG is found reliable in infants with warm extremities by 76% of the caregivers. Venous blood gas would be accepted by 60% of the caregivers, independent of the mode of respiratory support, and only when venous blood sample was needed for other reasons.

CONCLUSION

This survey identified a wide variation in preference in monitoring oxygenation and gas exchange monitoring among Dutch neonatal staff members.

Overnight Transcutaneous Carbon Dioxide Monitoring in Eucapnic Patients with Obstructive Sleep Apnea Syndrome

OBJECTIVES

We monitored increases in CO2 levels during sleep by measuring transcutaneous pCO2 (PtcCO2) to determine its relationship with polysomnographic data in normocapnic patients with obstructive sleep apnea syndrome (OSAS).

MATERIAL AND METHODS

Between October 2011 and December 2012, 139 patients underwent PtcCO2 monitoring with polysomnography. All patients were evaluated with arterial blood gas (ABG) measurements and pulmonary function tests (PFTs). We excluded 13 patients with COPD and/or daytime hypercapnia and 29 patients whose PtcCO2 records could not be evaluated.

RESULTS

The patients' mean age was 46.8±10.3 years. Fifty-nine patients (60.8%) were male, and 38 (39.2%) patients were female. The mean overnight PtcCO2 was ≤45 mm Hg in 84 (86.6%) patients and >45 mm Hg in 13 (13.4%) patients. In the group with PtcCO2>45 mm Hg, 10 patients had an apnea-hypopnea index (AHI) >15, and 3 patients had an AHI<15, without a statistically significant difference (p=0.078). The mean apnea and apnea/interapnea periods were similar. The mean PtcCO2 values correlated with time spent when the SpO2 was <90% (r=0.220, p<0.031). When we grouped the patients by AHI, 60 (61.8%) patients had an AHI>15 (moderate to severe OSAS), and 37 (37.2%) had an AHI<15 (mild OSAS). Of the former group, 16.7% had a mean PtcCO2 >45 mm Hg, whereas this ratio was 8.1% in the latter group. The difference was not statistically significant (p=0.359). In the group with an AHI>15, the highest PtcCO2 levels were significantly higher (p<0.05).

CONCLUSION

We conclude that seemingly eucapnic OSAS patients may experience hypercapnia when sleeping, and PtcCO2 monitoring may be useful in the early diagnosis of hypercapnia.

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

OBJECTIVES

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.

DESIGN

Prospective observational study.

SETTING

University teaching hospital ICU.

ANIMALS

Twenty-three client-owned dogs.

INTERVENTIONS

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.

MEASUREMENTS AND MAIN RESULTS

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).

CONCLUSIONS

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.

Non invasive monitoring in mechanically ventilated pediatric patients

Cardiopulmonary monitoring is a key component in the evaluation and management of critically ill patients. Clinicians typically rely on a combination of invasive and non-invasive monitoring to assess cardiac output and adequacy of ventilation. Recent technological advances have led to the introduction: of continuous non-invasive monitors that allow for data to be obtained at the bedside of critically ill patients. These advances help to identify hemodynamic changes and allow for interventions before complications occur. In this manuscript, we highlight several important methods of non-invasive cardiopulmonary monitoring, including capnography, transcutaneous monitoring, pulse oximetry, and near infrared spectroscopy.

Performance of capnometry in non-intubated infants in the pediatric intensive care unit

Background

Assessing the ventilatory status of non-intubated infants in the Pediatric Intensive Care Unit (PICU) is a constant challenge. Methods to evaluate ventilation include arterial blood gas analysis (ABG), which is invasive and intermittent, and transcutaneous carbon dioxide monitoring (P_tcCO2), which, while non-invasive, is also intermittent. A method that is non-invasive and continuous would be of great benefit in this population. We hypothesized that non-invasive capnometry via sidestream monitoring of exhaled carbon dioxide (CO₂) would provide an acceptable measurement of ventilatory status when compared to ABG or P_tcCO2.

Methods

Preliminary prospective study of infants less than one year of age admitted to the PICU in a large urban teaching hospital. Infants not intubated and not requiring non-invasive ventilation were eligible. A sidestream CO₂ reading was obtained in a convenience sample of 39 patients. A simultaneous ABG was collected in those with an arterial catheter, and a P_tcCO2 was obtained in those without.

Results

Correlation of sidestream CO₂ with ABG was excellent (r² = 0.907). Sidestream correlated less well with P_tcCO2 (r² = 0.649). Results were not significantly altered when weight and respiratory rate were added as independent variables. Bland-Altman analysis revealed a bias of -2.7 with a precision of ±6.5 when comparing sidestream CO₂ to ABG, and a bias of -1.7 with a precision of ±9.9 when comparing sidestream CO₂ to P_tcCO2.

Conclusions

Performance of sidestream monitoring of exhaled CO₂ is acceptable clinical trending to assess the effectiveness of ventilation in non-intubated infants in the PICU.