Detection of carbon dioxide thresholds using low-flow sidestream capnography in ventilated preterm infants

Effect of additional dead space using end-tidal CO2 measurement on ventilating preterm infants: An experimental study

BACKGROUND

Dead space is the part of the airway where no gas exchange takes place. Any increase in dead space volume has a proportional effect on the required tidal volume and thus on the risk of ventilation-induced lung injury. Inserts that increase dead space are therefore not used in small preterm infants. This includes end-tidal CO2 measurement.

OBJECTIVE

The aim of this study was to investigate the effect of the end-tidal CO2 measurement adapter on ventilation.

METHODS

In an experimental setup, an end-tidal CO2 measurement adapter, three different pneumotachographs (PNT-A, PNT-B, PNT-Neo), and a closed suction adapter were combined in varying set-ups. The time required for CO2 elimination by a CO2-flooded preterm infant test lung was measured.

RESULTS

PNT-A prolonged CO2 elimination time by 0.9 s (+3.3%), Neo-PNT by 3.2 s (+11.6%) and PNT-B by 9.0 s (+32.7%). The end-tidal CO2 measurement adapter prolonged the elimination time by an additional second without the pneumotachograph (+3.6%) and in combination with PNT-A (+3.1%) and PNT-Neo (+3.1%). In conjunction with PNT-B, the end-tidal CO2 measurement adapter reduced the elimination time by 0.3 seconds (-1%). The use of a closed suction adaptor increased the CO2 elimination time by a further second with PNT-Neo (+3.1%) and by an additional two seconds with no flow sensor (+6.9%), with PNT-A (+6.4%) and with PNT-B (+5.5%).

CONCLUSION

The flow sensor had the greatest influence on ventilatory effort, while end-tidal CO2 measurement had only a moderate effect. The increased ventilatory effort levied by the CO2 measurement was dependent on the flow sensor selected. The use of closed suctioning more negatively impacted ventilatory effort than did end-tidal CO2 measurement.

Capnometry during neonatal transport-Mini review

AIM

The aim of this review was to give an overview of available data on end-tidal CO2 (etCO2 ) monitoring, also called capnometry, during neonatal transport.

METHODS

Pubmed/MEDLINE database was searched using research question (capno* OR etCO2 OR detCO2 OR (['end tidal' OR 'end-tidal'] AND [CO2 OR 'carbon dioxide']) AND (neonat* OR infant* OR newborn*) AND transport*). All articles relevant to the topic were reviewed and summarised.

RESULTS

The lack of studies relevant to neonatal transport prompted us to extend the search to capnometry in a neonatal intensive care setting. The published studies are showing conflicting results. The different study populations, technologies used to measure etCO2 , types of etCO2 sampling and the diverse sites of blood gas tests make the data unsuitable for systematic comparison.

CONCLUSION

Further research to obtain more data on capnometry during neonatal transport will be necessary to define precisely under what circumstances can end-tidal monitoring of CO2 be reliably used in neonates during transport and also how to interpret the measured values.

Capnography in newborns under mechanical ventilation and its relationship with the measurement of CO2 in blood samples

INTRODUCTION

Monitoring the partial pressure of CO₂ (PCO₂) in newborns who require ventilation would allow avoiding hypocapnia and hypercapnia. The measurement of end-tidal carbon dioxide (ETCO₂) is an alternative rarely implemented in this population.

OBJECTIVE

To evaluate the relationship between ETCO₂ and PCO₂ in newborns.

METHODS

Cross-sectional study comparing two PCO₂ measurement methods, the conventional one by analysis of blood samples and the one estimated by ETCO₂. The study included hospitalized newborns that required conventional mechanical ventilation. The ETCO₂ was measured with a Tecme GraphNet® neo, a neonatal ventilator with an integrated capnograph, and we obtained the ETCO₂-PCO₂ gradient. We conducted correlation and Bland-Altman plot analyses to estimate the agreement.

RESULTS

A total of 277 samples (ETCO₂ / PCO₂) from 83 newborns were analyzed. The mean values ​​of ETCO₂ and PCO₂ were 41.36mmHg and 42.04mmHg. There was a positive and significant correlation between ETCO₂ and PCO₂ in the overall analysis (r=0.5402; P<.001) and in the analysis of each unit (P<.001). The mean difference was 0.68 mmHg (95% CI, -0.68 to 1.95) and was not significant. We observed a positive systematic error (PCO₂ > ETCO₂) in 2 of the units, and a negative difference in the third (PCO₂ < ETCO₂).

DISCUSSION

The correlation between ETCO and PCO₂ was significant, although the obtained values ​​were not equivalent, with differences ranging from 0.1mmHg and 20mmHg. Likewise, we found systematic errors that differed in sign (positive or negative) between institutions.

Non-invasive carbon dioxide monitoring in neonates: methods, benefits, and pitfalls

Wide fluctuations in partial pressure of carbon dioxide (PaCO2) can potentially be associated with neurological and lung injury in neonates. Blood gas measurement is the gold standard for assessing gas exchange but is intermittent, invasive, and contributes to iatrogenic blood loss. Non-invasive carbon dioxide (CO2) monitoring has become ubiquitous in anesthesia and critical care and is being increasingly used in neonates. Two common methods of non-invasive CO2 monitoring are end-tidal and transcutaneous. A colorimetric CO2 detector (a modified end-tidal CO2 detector) is recommended by the International Liaison Committee on Resuscitation (ILCOR) and the American Academy of Pediatrics to confirm endotracheal tube placement. Continuous CO2 monitoring is helpful in trending PaCO2 in critically ill neonates on respiratory support and can potentially lead to early detection and minimization of fluctuations in PaCO2. This review includes a description of the various types of CO2 monitoring and their applications, benefits, and limitations in neonates.

Correlation of End-Tidal Carbon Dioxide with Arterial Carbon Dioxide in Mechanically Ventilated Neonates: A Scoping Review

Monitoring CO2 levels in intubated neonates is highly relevant in the face of complications associated with altered CO2 levels. Thus, this review aims to present the scientific evidence in the literature regarding the correlation between arterial carbon dioxide measured by non-invasive methods in newborns submitted to invasive mechanical ventilation. The search was carried out from January 2020 to January 2021, in the Scopus, Medline, The Cochrane Library, Web of Science, CINAHL and Embase databases. Also, a manual search of the references of included studies was performed. The main descriptors used were: "capnography," "premature infant," "blood gas analysis," and "mechanical ventilation." As a result, 221 articles were identified, and 18 were included in this review. A total of 789 newborns were evaluated, with gestational age between 22.8 and 42.2 weeks and birth weight between 332 and 4790 g. Capnometry was the most widely used non-invasive method. In general, the correlation and agreement between the methods evaluated in the studies were strong/high. The birth weight did not influence the results. The gestational age of fewer than 37 weeks implied, in its majority, a moderate correlation and agreement. Therefore, we can conclude that there was a predominance of a strong correlation between arterial blood gases and non-invasive methods, although there are variations found in the literature. Even so, the results were promising and may provide valuable data for future studies, which are necessary to consolidate non-invasive methods as a reliable and viable alternative to arterial blood gasometry.

Assessment of sidestream end-tidal capnography in ventilated infants on the neonatal unit

OBJECTIVES

Continuous monitoring of carbon dioxide (CO₂ ) levels can be achieved by capnography. Our aims were to compare the performance of a sidestream capnograph with a low dead space and sampling rate to a mainstream device and evaluate whether its results correlated with arterial/capillary CO₂ levels in infants with different respiratory disease severities.

WORKING HYPOTHESES

End-tidal carbon dioxide (EtCO₂ ) results by sidestream and mainstream capnography would correlate, but the divergence of EtCO₂ and CO₂ results would occur in more severe lung disease.

STUDY DESIGN

Prospective cohort study.

PATIENT-SUBJECT SELECTION

Fifty infants with a median (interquartile range) gestational age of 31.1 (27.1-37.4) weeks and birth weight of 1.37 (0.76-2.95) kg.

METHODOLOGY

Concurrent measurements of EtCO₂ in ventilated infants were made using a new Microstream sidestream device and a mainstream capnograph (gold standard). Results from both devices were compared with arterial or capillary CO₂ levels. The ratio of dead space to tidal volume (Vd/Vt) was calculated to assess respiratory disease severity.

RESULTS

The mean difference between the concurrent measurements of EtCO₂ was -0.54 ± 0.67 kPa (95% agreement levels - 1.86 to 0.77 kPa), the correlation between the two was r = .85 (P < .001). Sidestream capnography results correlated better with partial pressure of CO₂ (PCO₂ ) levels in infants with less (Vd/Vt < 0.35; r²  = .66, P < .001) rather than more severe (Vd/Vt > 0.35; r²  = .33, P = .01) lung disease.

CONCLUSIONS

The sidestream capnography performed similarly to the mainstream capnography. The poorer correlation of EtCO₂ to PCO₂ levels in infants with severe respiratory disease should highlight to clinicians increased ventilation-perfusion mismatch.

Continuous Noninvasive Carbon Dioxide Monitoring in Neonates: From Theory to Standard of Care

Ventilatory support may affect the short- and long-term neurologic and respiratory morbidities of preterm infants. Ongoing monitoring of oxygenation and ventilation and control of adequate levels of oxygen, pressures, and volumes can decrease the incidence of such adverse outcomes. Use of pulse oximetry became a standard of care for titrating oxygen delivery, but continuous noninvasive monitoring of carbon dioxide (CO₂) is not routinely used in NICUs. Continuous monitoring of CO₂ level may be crucial because hypocarbia and hypercarbia in extremely preterm infants are associated with lung and brain morbidities, specifically bronchopulmonary dysplasia, intraventricular hemorrhage, and cystic periventricular leukomalacia. It is shown that continuous monitoring of CO₂ levels helps in maintaining stable CO₂ values within an accepted target range. Continuous monitoring of CO₂ levels can be used in the delivery room, during transport, and in infants receiving invasive or noninvasive respiratory support in the NICU. It is logical to hypothesize that this will result in better outcome for extremely preterm infants. In this article, we review the different noninvasive CO₂ monitoring alternatives and devices, their advantages and disadvantages, and the available clinical data supporting or negating their use as a standard of care in NICUs.

Current methodological and technical limitations of time and volumetric capnography in newborns

Although capnography is a standard tool in mechanically ventilated adult and pediatric patients, it has physiological and technical limitations in neonates. Gas exchange differs between small and adult lungs due to the greater impact of small airways on gas exchange, the higher impact of the apparatus dead space on measurements due to lower tidal volume and the occurrence of air leaks in intubated patients. The high respiratory rate and low tidal volume in newborns, especially those with stiff lungs, require main-stream sensors with fast response times and minimal dead-space or low suction flow when using side-stream measurements. If these technical requirements are not fulfilled, the measured end-tidal CO2 (P et CO 2 ), which should reflect the alveolar CO2 and the calculated airway dead spaces, can be misleading. The aim of this survey is to highlight the current limitations of capnography in very young patients to avoid pitfalls associated with the interpretation of capnographic parameters, and to describe further developments.

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.

Validity of sidestream endtidal carbon dioxide measurement in critically ill, mechanically ventilated children

INTRODUCTION

Capnography is used to monitor the endtidal carbon dioxide tension (EtCO2) in exhaled gas. Sidestream capnography has great potential to monitor mechanically ventilated pediatric patients, given the continuous sampling from the endotracheal tube into a gas sensor. However, hemodynamic and respiratory impairments may reduce reliability and validity of sidestream capnography to monitor arterial carbon dioxide tension (PaCO2) in critically ill, mechanically ventilated children.

METHODS

In 47 mechanically ventilated pediatric patients (aged 0-14 years, median age 17.2 months), a total of 341 consecutive measurements of PaCO2, EtCO2, respiratory and hemodynamic parameters were performed, and capnogram shape was determined. Validity was assessed with the Bland-Altman limit of agreement (loa), mixed models were used to adjust for variation between patients, and potential confounders were considered with multivariable analyses.

RESULTS

EtCO2 (mean 4.50 ± 0.96 kPa) underestimated PaCO2 (mean 5.37 ± 0.87) considerably, resulting in a loa of 0.87 kPa [95% confidence interval (95% CI) -1.03;2.77] and 42.2% percentage error. The association improved significantly b = 0.54 [95 %CI = 0.45;0.64, P < 0.001] when corrected for individual differences. The association between EtCO2 and PaCO2 was not influenced by any of the potential confounders.

CONCLUSIONS

Sidestream capnography in mechanically ventilated infants and children seems moderately reliable and valid when corrected for individual differences. Therefore, it could only be used with caution for trend estimation in the individual patient.

Minimizing blood loss and the need for transfusions in very premature infants

Reducing blood loss and the need for blood transfusions in extremely preterm infants is part of effective care. Delayed cord clamping is well supported by the evidence and is recommended for infants who do not immediately require resuscitation. Cord milking may be an alternative to delayed cord clamping; however, more research is needed to support its use. In view of concerns regarding the increased risk for cognitive delay, clinicians should avoid using hemoglobin transfusion thresholds lower than those tested in clinical trials. Higher transfusion volumes (15 mL/kg to 20 mL/kg) may decrease exposure to multiple donors. Erythropoietin is not recommended for routine use due to concerns about retinopathy of prematurity. Elemental iron supplementation (2 mg/kg/day to 3 mg/kg/day once full oral feeds are achieved) is recommended to prevent later iron deficiency anemia. Noninvasive monitoring (eg, for carbon dioxide, bilirubin) and point-of-care testing reduce the need for blood sampling. Clinicians should strive to order the minimal amount of blood sampling required for safe patient care, and cluster samplings to avoid unnecessary skin breaks.

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.

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.

A review of carbon dioxide monitoring in preterm newborns in the delivery room

INTRODUCTION

The physiologic adaptation to extra uterine life during the immediate neonatal period is unique. Many newborns require assistance in this adaptive process. Recent evidence now supports titrating oxygen to guide resuscitation but no guidance is provided on utilizing exhaled CO2 measurements.

AIM

To review the current evidence relating to the use of CO2 monitoring in preterm newborns in the delivery room.

METHODS

Search was performed using the Cochrane Central Register of Controlled Trials, MEDLINE (1966-2014) and PREMEDLINE, EMBASE (1980-2014), CINAHL (1982-2014), Web of Science (1975-2014) and the Oxford Database of Perinatal Trials.

RESULTS

The search revealed 21 articles relating to CO2 detection, either quantitative or qualitative, in the newborn infant. The majority of these were observational studies, eight relating to CO2 detection as a means of confirming correct endotracheal tube placement in the newborn infant. The other indication is for mask ventilation, and there is one randomized control trial and four observational studies of CO2 detection during mask ventilation. The overall recommendation for CO2 detection for both clinical uses in the delivery suite is level B.

DISCUSSION

CO2 detection may be of particular benefit for preterm infants in the delivery suite. However there is a need for further research into CO2 detection, in particular capnography, as a means of confirming effective PPV in neonatal resuscitation.

Evaluation of a new side-stream, low dead space, end-tidal carbon dioxide monitoring system in rats

The aim of this study was to evaluate a newly developed infrared side-stream capnograph with minimal sample volume for the continuous measurement of end-tidal carbon dioxide (CO2) concentrations in small rodents. Thirty-four male Wistar rats (weight 345 ± 70 g) were treated in accordance with the National Institutes of Health (NIH) guidelines for animal care. All experiments were performed with approval of the local animal care and use committee. Sepsis was induced by implanting an 18 gauge stent into the colon 24 h prior to the experiments, allowing a constant fecal leakage into the peritoneal cavity (25 septic and nine control animals). Hemodynamic variables and end-tidal CO2 were recorded continuously and arterial blood (5 × 120 µL) was sampled periodically for arterial blood gas analysis. After baseline controlled mechanical ventilation was randomized and titrated to either normocapnia (35–45 mmHg) or hypercapnia (65–75 mmHg) with exogenous application of CO2. A total of 155 paired CO2 measurements comparing end-tidal and arterial partial pressure were conducted. Side-stream capnography underestimated the CO2 partial pressure with a bias of −6.1 mmHg and a 95% limit of agreement from 6.7 to –19.1 mmHg. Our results suggest that side-stream end-tidal CO2 monitoring with a low dead space could be utilized in rats as a surrogate for the arterial CO2 measurement over a wide range of partial pressures in normal and septic animals.

Sidestream microstream end tidal carbon dioxide measurements and blood gas correlations in neonatal intensive care unit

OBJECTIVE

The study was designed to assess the use of newer sidestream microstream end tidal carbon dioxide (ETCO(2) ) device in predicting blood carbon dioxide (PCO(2) ) measurements in very low birth weight (VLBW = birth weight <1,500 g) and non-VLBW NICU neonates.

STUDY DESIGN

Sidestream microstream ETCO(2) detectors were allowed time to calibrate and reach steady state prior to blood gas measurements. Blood CO(2) (PCO(2) ) and simultaneous ETCO(2) were recorded. Ratio of dead space to tidal volume (VD/VT) was calculated using modified Bohr's equation. Correlation coefficient, estimates of difference, standard deviation, and 95% limits of agreement between ETCO(2) and PCO(2) concentrations were calculated.

RESULTS

Two hundred eighty-six paired samples were collected from 48 ventilated NICU patients. Average PCO(2) and ETCO(2) were 58.4 and 50.6 with a correlation of 0.76. Subgroup analysis showed a correlation of 0.73 in 204 paired blood from 34 VLBW infants and 0.82 in 82 paired samples from non-VLBW infants. Estimates of difference ± standard deviation between PCO(2) and ETCO(2) concentrations in these three groups, respectively (ALL, VLBW, and non-VLBW) were 7.84 ± 9.96, 8.2 ± 10.16, and 6.95 ± 9.45. The correlation coefficient significantly improved in the VLBW group to 0.86 with dead space to tidal volume ratio (VD/VT) <30% (0.86 vs. 0.42; P < 0.001).

CONCLUSION

ETCO(2) measurements using sidestream microstream technology in VLBW demonstrated that the correlation of ETCO(2) and PCO(2) was moderate, but the agreement was less than adequate (bias > 5 mmHg in all groups). The results improved with lower VD/VT, suggesting that sidestream capnography is more reliable in conditions of less severe lung disease.

Continuous integrated distal capnography in infants ventilated with high frequency ventilation

OBJECTIVE

To assess within a feasibility study the correlation, agreement, and trending of continuous integrated distal capnography (dCap) with PaCO(2) in infants on HFV.

STUDY DESIGN

Sixteen premature infants [median (range) gestational age: 26.5 (24.7-34.7) weeks], ventilated with HFV (mean ± SD airway pressure: 8.1 ± 2.1 cmH(2) O, FiO(2) : 0.39 ± 0.21) for RDS, intubated with a double-lumen endotracheal-tube and whose data were recorded on a bedside computer participated in the study. Side-stream dCap was measured via the extra-port of a double-lumen endotracheal-tube by a Microstream capnograph, with a specially designed software for HFV and compared with simultaneous PaCO(2) . Integrated time-window analysis of the data was performed retrospectively on data collected prospectively.

RESULTS

Analysis included 195 measurements. The correlation of dCap with PaCO(2) (r = 0.68, P < 0.0001) and the agreement (bias ± precision: -2.0 ± 10.7 mmHg) were adequate. Area under the ROC curves for dCap to detect high (>60 mmHg) or low (<35 mmHg) PaCO(2) was 0.79 (CI: 0.70-0.89) and 0.87 (CI: 0.73-1.00), respectively; P < 0.0001. Changes in dCap and in PaCO(2) for consecutive measurements within each patient were adequately correlated (r = 0.65, P < 0.0001).

CONCLUSIONS

Continuous integrated dCap is feasible in premature infants ventilated with HFV and can be helpful for trends and alarm for unsafe levels of PaCO(2) .

End-tidal carbon dioxide monitoring in very low birth weight infants: correlation and agreement with arterial carbon dioxide

OBJECTIVE

We aimed to determine the correlation and the agreement between end-tidal carbon dioxide (ETCO(2)) and partial pressure of arterial carbon dioxide (PaCO(2) ) in very low birth weight infants (VLBWI); furthermore, we assessed factors that could affect the ETCO(2)-PaCO(2) relationship.

METHODS

Simultaneous end-tidal and arterial CO(2) pairs were obtained from ventilated VLBWI who were monitored by mainstream capnography and had umbilical arterial catheter. Correlation and agreement between ETCO(2) and PaCO(2) were evaluated by using Spearman test and Bland-Altman method, respectively.

RESULTS

A total of 143 simultaneous ETCO(2)-PaCO(2) pairs were analyzed from 45 ventilated VLBWI. There was a significant correlation (r = 0.69; P < 0.0001) between ETCO(2) and PaCO(2) values. The ETCO(2) value was lower than the corresponding PaCO(2) value in 94% pairs, with a mean bias of 13.5 ± 8.4 mmHg (95% agreement levels, -3.0 to 29.9 mmHg). Mean PaCO(2)-ETCO(2) bias was similar between ELBWI (13.1 ± 7.7 mmHg; 95% agreement levels, -1.9 and 28.2 mmHg) and infants with birth weight 1,001-1,500 g (14.8 ± 9.7 mmHg; 95% agreement levels -4.3 and 33.8 mmHg). The bias between ETCO(2) and PaCO(2) was significantly increased with increasing FiO(2), mean airway pressure and oxygenation index. Within each patient, there was a positive correlation (r = 0.78, P < 0.0001) between the changes in PaCO(2) and the simultaneous changes in ETCO(2).

CONCLUSIONS

In ventilated VLBWI, the correlation between mainstream ETCO(2) and PaCO(2) is good, but the agreement is poor and negatively influenced by the severity of pulmonary disease. Capnography is feasible in ELBWI. ETCO(2) should not replace PaCO(2) measurements in ventilated VLBWI, but may have a role to detect trends of PaCO(2).

Capnography in spontaneously breathing preterm infants with bronchopulmonary dysplasia

BACKGROUND

In adult patients with chronic obstructive pulmonary disease, there is a gradient between end-tidal carbon dioxide (EtCO(2)) and arterial carbon dioxide pressure (PaCO(2)), and the slope of the ascending phase of the capnogram is decreased due to obstruction. Corresponding data are lacking in infants with bronchopulmonary dysplasia (BPD).

OBJECTIVES

To compare PCO(2) -EtCO(2) gradient and capnogram shape in two groups of spontaneously breathing preterm subjects: infants with BPD and infants without respiratory disease (controls).

MATERIAL AND METHODS

Capnography was performed at 36 weeks postmenstrual age in 20 infants (12 BPD with oxygen dependency, 8 controls). Respiratory rate and the components of the respiratory cycle were measured. The PCO(2) -EtCO(2) gradient was calculated using EtCO(2) values and simultaneously sampled capillary values (PcCO(2)). Capnograms were compared between groups.

RESULTS

In BPD subjects, respiratory rate was increased (60 ± 16 bpm vs 43 ± 16 bpm, P = 0.009); a widened PcCO(2) -EtCO(2) gradient was observed (13 ± 4 mmHg vs 0 ± 7 mmHg, P = 0.0013); the ascending phase of the capnogram was not decreased, whereas the initial inspiratory phase was prolonged (0.32 ± 0.05 vs 0.24 ± 0.04, P = 0.001).

CONCLUSIONS

Compared with healthy infants, a higher PcCO(2) -EtCO(2) gradient was observed in infants with BPD, suggesting that ventilation-perfusion mismatch may be present in these infants. The capnogram did not exhibit the characteristic shape of airway obstruction.