Use of capnography to detect hypercapnic episodes during weaning from mechanical ventilation

Capnography and Pulse Oximetry Improve Fast Track Extubation in Patients Undergoing Coronary Artery Bypass Graft Surgery: A Randomized Clinical Trial

Background

Use of capnography as a non-invasive method during the weaning process for fast track extubation (FTE) is controversial. We conducted the present study to determine whether pulse oximetry and capnography could be utilized as alternatives to arterial blood gas (ABG) measurements in patients under mechanical ventilation (MV) following coronary artery bypass graft (CABG) surgery.

Methods

In this randomized clinical trial, 70 patients, who were candidates for CABG surgery, were randomly assigned into two equal groups (n = 35), intervention and control group. In the intervention group, the ventilator management and weaning from MV was done using Etco2 from capnography and SpO2 from pulse oximetry. Meanwhile, in the control group, weaning was done based on ABG analysis. The length of intensive care unit (ICU) stay, time to extubation, number of manual ventilators setting changes, and alarms were compared between the groups.

Results

The end-tidal carbon dioxide (ETCO2) levels in the intervention group were completely similar to the partial pressure of carbon dioxide (PaCo2) in the control group (39.5 ± 3.1 vs. 39.4 ± 4.32, p > 0.05). The mean extubation times were significantly shorter in the intervention group compared to those in the control patients (212.2 ± 80.6 vs. 342.7 ± 110.7, p < 0.001). Moreover, the number of changes in the manual ventilator setting and the number of alarms were significantly lower in the intervention group. However, the differences in the length of stay in ICU between the two groups were not significant (p = 0.219).

Conclusion

Our results suggests that capnography can be used as an alternative to ABG. Furthermore, it is a safe and valuable monitor that could be a good alternative for ABG in this population. Further studies with larger sample sizes and on different disease states and populations are required to assess the accuracy of our findings.

Clinical Trial Registration

Current Controlled Trials, IRCT, IRCT201701016778N6, Registered 3 March 2017, https://www.irct.ir/trial/7192.

The Weaning Index combining EtCO2 and respiratory rate early identifies Spontaneous Breathing Trial failure

BACKGROUND

We aimed to evaluate the predictive value of the end-tidal CO2 (EtCO2) alone or combined with ventilation related parameters on Spontaneous Breathing Trial (SBT) outcome on mechanically ventilated patients.

METHODS

Prospective observational study in a medical Intensive Care Unit. Mechanically ventilated adult patients who met predefined criteria for weaning were included. Patients underwent a T-piece SBT for 30 minutes and the hemodynamic and respiratory clinical parameters including EtCO2 were recorded every five minutes.

RESULTS

The study included 280 patients, who were studied (age: 64±17 years, SAPS II: 44 [34-56]) during a first SBT and 76 patients during a second SBT. The Weaning Index, defined as the product of the respiratory rate and EtCO2, was a strong early predictive factor of SBT outcome; at 10 minutes, the area under the curve (AUC) was 86% ([80-90], P<0.0001) during the first SBT and 88% ([80-96], P<0.0001) during the second SBT. After 10 minutes of SBT, a Weaning Index >1100 identified patients that will not successfully complete the SBT at 30 minutes with a specificity of 98%.

CONCLUSIONS

In unselected mechanically ventilated patients, the Weaning Index is helpful to early identify patients who will fail the SBT during a first and a second trial.

De l’entrée à la sortie du service de réanimation adulte : une mise au point sur l’utilisation courante du monitoring du CO2 expiré

L’objectif de cette mise au point est d’effectuer une revue des indications de l’utilisation du monitorage du CO2 expiré en réanimation adulte. De par sa physiologie, sa mesure est un reflet de l’état hémodynamique, respiratoire et métabolique du patient. La spectrométrie infrarouge est la méthode de mesure la plus courante. La capnographie commune (CO2 expiré en fonction du temps) est divisée en plusieurs phases dont l’analyse visuelle peut faire évoquer de nombreuses anomalies ventilatoires. La capnographie volumétrique fournit une mesure de l’espace mort. La capnométrie est recommandée en réanimation pour contrôler l’intubation trachéale ou bien au cours d’un arrêt cardiorespiratoire comme facteur pronostique. Tout patient traité par ventilation mécanique invasive, surtout lors d’un transport, doit être équipé d’un capnomètre afin d’anticiper toute complication respiratoire (extubation, bronchospasme, hypoventilation). La pression de fin d’expiration en CO2 (PetCO2) est une évaluation de la pression artérielle en CO2 (PaCO2) utile pour limiter le nombre de prélèvements biologiques, par exemple en neuroréanimation, mais de nombreux facteurs font varier le gradient entre ces deux valeurs. Les études n’apportent pas de preuve pour l’utilisation de la capnographie volumétrique dans le diagnostic d’embolie pulmonaire en réanimation. Chez les patients souffrant de syndrome de détresse respiratoire aiguë, la littérature médicale n’apporte pas de preuve suffisante pour un intérêt en pratique clinique courante de la capnométrie volumétrique qui semble limitée dans ce cas à la recherche.

Implementation of continuous capnography is associated with a decreased utilization of blood gases

Background

Capnography provides a continuous, non-invasive monitoring of the CO₂ to assess adequacy of ventilation and provide added safety features in mechanically ventilated patients by allowing for quick identification of unplanned extubation. These monitors may allow for decreased utilization of blood gases. The objective was to determine if implementation of continuous capnography monitoring decreases the utilization of blood gases resulting in decreased charges.

Methods

This is a retrospective review of a quality improvement project that compares the utilization of blood gases before and after the implementation of standard continuous capnography. The time period of April 2010 to September 2010 was compared to April 2011 to September 2011. Parameters collected included total number of blood gases analyzed, cost of blood gas analysis, ventilator and patient days.

Results

The total number of blood gases after the institution of end tidal CO₂ monitoring decreased from 12,937 in 2009 and 13,171 in 2010 to 8,070 in 2011. The average number of blood gases per encounter decreased from 20.8 in 2009 and 21.6 in 2010 to 13.8 post intervention. The blood gases per ventilator day decreased from 4.94 in 2009 and 4.76 in 2010 to 3.30 post intervention. The total charge savings over a 6-month period was $880,496.

Conclusions

Continuous capnography resulted in a significant savings over a 6-month period by decreasing the utilization of blood gas measurements.

Accuracy of transcutaneous carbon dioxide monitoring in hypotensive patients

Objectives

Continuous blood gas monitoring is frequently necessary in critically ill patients. Our aim was to assess the accuracy of transcutaneous CO2 tension (PtcCO2) monitoring in the emergency department (ED) assessment of hypotensive patients by comparing it with the gold standard of arterial blood gas analysis (ABGA).

Methods

All patients receiving PtcCO2 monitoring in the ED were included. We excluded paediatric patients, patients with no ABGA results during a hypotensive event, patients whose ABGA was not performed simultaneously with PtcCO2 monitoring, and patients who received sodium bicarbonate for resuscitation. The included patients were classified into hypotensive patients and normotensive patients. A hypotensive patient was defined as a patient showing a mean arterial pressure under 60 mm Hg. The agreement in measurement between PaCO2 tension (PaCO2) and PtcCO2 were investigated in both groups.

Results

The mean difference between PaCO2 and PtcCO2 was 2.1 mm Hg, and the Bland–Altman limits of agreement (bias±1.96 SD) ranged from −15.6 to 19.7 mm Hg in the 28 normotensive patients. The mean difference between PaCO2 and PtcCO2 was 1.1 mm Hg, and the Bland–Altman limits of agreement (bias±1.96 SD) ranged from −19.5 to 21.7 mm Hg in the 26 hypotensive patients. The weighted κ values were 0.64 in the normotensive patients and 0.60 in the hypotensive patients.

Conclusions

PtcCO2 monitoring showed wider limits of agreement with PaCO2 in urgent situations in the ED environment. However, acutely developed hypotension does not affect the accuracy of PtcCO2 monitoring.

Liberation from mechanical ventilation: what monitoring matters?

Over the past 2 decades, the art of "weaning" from mechanical ventilation has been informed by increasing published basic science and outcomes studies. Although monitoring technologies can provide vast amounts of information before, during, and after liberation from mechanical ventilation, little data exists on how to maximally harness even routinely monitored, basic physiologic parameters. Overdependence on technology and derived variables, without data to demonstrate benefit, may even inhibit the patient's progress if it is used inappropriately. We review the scientific evidence for best using routinely available physiologic data and a few more sophisticated and invasive monitoring technologies during weaning. We also suggest future study designs that would better inform the process of liberation from the ventilator and endotracheal extubation.

Transcutaneous arterial carbon dioxide pressure monitoring in critically ill adult patients

OBJECTIVE

To evaluate the accuracy of transcutaneous PCO(2) (PtcCO(2)) as a surrogate for arterial PCO(2) (PaCO(2)) in a cohort of adult critically ill patients in a medical intensive care unit (ICU).

DESIGN

Prospective observational study comparing paired measures of transcutaneous and arterial PCO(2).

SETTING

A 26-bed medical ICU.

PATIENTS

Fifty ICU patients monitored with a SenTec Digital Monitor placed at the ear lobe over prolonged periods.

RESULTS

A total of 189 paired PCO(2) measures were obtained. Twenty-one were excluded from analysis, because profound skin vasoconstriction was present (PCO(2) bias =-10.8+/-21.8 mmHg). Finally, 168 were analysed, including 137 obtained during mechanical ventilation and 82 under catecholamine treatment. Body temperature was below 36 degrees C for 27 measurements. Mean duration of monitoring was 17+/-17 h. The mean difference between PaCO(2) and PtcCO(2) was -0.2+/-4.6 mmHg with a tight correlation (R(2)=0.92, p>0.01). PCO(2) bias did not significantly change among three successive measurements. Changes in PaCO(2) and in PtcCO(2) between two blood samples were well correlated (R(2)=0.78, p>0.01). Variations of more than 8 mmHg in PtcCO(2) had 86% sensitivity and 80% specificity to correctly predict similar changes in PaCO(2) in the same direction. Catecholamine dose or respiratory support did not affect PtcCO(2) accuracy. Hypothermia has only a small effect on accuracy. No complication related to a prolonged use of the sensor was observed

CONCLUSION

Transcutaneous PCO(2) provides a safe and reliable trend-monitoring tool, provided there is no major vasoconstriction.

Capnography as a rapid assessment and triage tool for chemical terrorism

The assessment and triage of victims of chemical terrorism in the emergency department and the prehospital setting has become an important priority. This article proposes the use of capnography as a prehospital assessment and triage tool for monitoring victims of chemical terrorism and for critically ill patients. Capnography provides the ABCs in less than 15 seconds and identifies the common complications of chemical terrorism. Further, the reliability of capnography is not affected by motion artifact or low perfusion and it is accurate and reliable in actively seizing patients. Emergency departments and emergency medical services systems should consider adding capnography to their chemical terrorism education and training.

Extubation failure: diagnostic value of occlusion pressure (P0.1) and P0.1-derived parameters

OBJECTIVE

To evaluate the ability of the new, built-in occlusion pressure (P0.1) measurement to predict extubation failure.

DESIGN AND SETTING

Prospective observational multicentre study in the ICU of five general hospitals.

PATIENTS

Hundred thirty patients on mechanical ventilation longer than 48 h when considered ready for weaning.

MEASUREMENTS AND RESULTS

Patients underwent a 30-min spontaneous breathing trial with simultaneous monitoring of occlusion pressure (P0.1) and breathing pattern (f/Vt). Sixteen patients (12%) failed the weaning trial and full ventilatory support was resumed, while 114 tolerated the trial and were extubated. Twenty-one (18%) required reintubation within 48 h. The area under the ROC curve for diagnosing extubation failure was 0.53 for f/Vt, 0.59 for P0.1 and 0.61 for P0.1*f/Vt (p=NS). Accordingly, P0.1*f/Vt more than 100 detected extubation failure with a sensitivity of 0.89, specificity of 0.35, positive predictive value of 0.21 and negative predictive value of 0.94.

CONCLUSION

During a first trial of spontaneous breathing on pressure support ventilation (PSV), bedside P0.1 and P0.1*f/Vt are of little help, if any, for predicting extubation failure.

Survey of use of end-tidal carbon dioxide for confirming tracheal tube placement in intensive care units in the UK

The use of end-tidal carbon dioxide monitoring to confirm the correct placement of a tracheal tube immediately after intubation is mandatory in the operating theatre. Tracheal intubation in critically ill patients can be challenging. Quick and accurate confirmation of tracheal tube placement is essential to minimise complications. This survey explored the use of end-tidal carbon dioxide monitoring to confirm tracheal tube placement in intensive care units in the UK. Questionnaires were sent to either the lead clinician or clinical director of randomly selected general adult intensive care units. One hundred and twenty-seven replies were received from the 215 questionnaires sent (response rate 59%). Twenty per cent of the units did not have an end-tidal carbon dioxide monitor, 20% had one end-tidal carbon dioxide monitor per bed and 60% had one end-tidal carbon dioxide monitor between several beds. Only 50% of the units having an end-tidal carbon dioxide monitor use it to confirm correct tracheal tube placement. Of these 50%, only about a third use it for every intubation. Seventy-two per cent of respondents felt that end-tidal carbon dioxide is well suited to confirm correct placement of tracheal tube in critically ill patients, but 50% did not think that confirmation using end-tidal carbon dioxide should be mandatory for intubations outside the operating theatre. Half of the units not having end-tidal a carbon dioxide monitor cited lack of resources as a reason. In summary, although four in every five intensive care units surveyed have end-tidal carbon dioxide monitors, only a small proportion use them to confirm correct placement of tracheal tube after intubation.

Carbon dioxide kinetics and capnography during critical care

Greater understanding of the pathophysiology of carbon dioxide kinetics during steady and nonsteady state should improve, we believe, clinical care during intensive care treatment. Capnography and the measurement of end-tidal partial pressure of carbon dioxide (PETCO2) will gradually be augmented by relatively new measurement methodology, including the volume of carbon dioxide exhaled per breath (VCO2,br) and average alveolar expired PCO2. Future directions include the study of oxygen kinetics.