Relationship between arterial and end-tidal carbon dioxide pressures during anesthesia using a laryngeal tube

Prehospital Cardiac Arrest Airway Management: An NAEMSP Position Statement and Resource Document

Airway management is a critical component of out-of-hospital cardiac arrest (OHCA) resuscitation. Multiple cardiac arrest airway management techniques are available to EMS clinicians including bag-valve-mask (BVM) ventilation, supraglottic airways (SGAs), and endotracheal intubation (ETI). Important goals include achieving optimal oxygenation and ventilation while minimizing negative effects on physiology and interference with other resuscitation interventions. NAEMSP recommends:Based on the skill of the clinician and available resources, BVM, SGA, or ETI may be considered as airway management strategies in OHCA.Airway management should not interfere with other key resuscitation interventions such as high-quality chest compressions, rapid defibrillation, and treatment of reversible causes of the cardiac arrest.EMS clinicians should take measures to avoid hyperventilation during cardiac arrest resuscitation.Where available for clinician use, capnography should be used to guide ventilation and chest compressions, confirm and monitor advanced airway placement, identify return of spontaneous circulation (ROSC), and assist in the decision to terminate resuscitation.

Optimizing Physiology During Prehospital Airway Management: An NAEMSP Position Statement and Resource Document

Airway management is a critical component of resuscitation but also carries the potential to disrupt perfusion, oxygenation, and ventilation as a consequence of airway insertion efforts, the use of medications, and the conversion to positive-pressure ventilation. NAEMSP recommends:Airway management should be approached as an organized system of care, incorporating principles of teamwork and operational awareness.EMS clinicians should prevent or correct hypoxemia and hypotension prior to advanced airway insertion attempts.Continuous physiological monitoring must be used during airway management to guide the timing of, limit the duration of, and inform decision making during advanced airway insertion attempts.Initial and ongoing confirmation of advanced airway placement must be performed using waveform capnography. Airway devices must be secured using a reliable method.Perfusion, oxygenation, and ventilation should be optimized before, during, and after advanced airway insertion.To mitigate aspiration after advanced airway insertion, EMS clinicians should consider placing a patient in a semi-upright position.When appropriate, patients undergoing advanced airway placement should receive suitable pharmacologic anxiolysis, amnesia, and analgesia. In select cases, the use of neuromuscular blocking agents may be appropriate.

Intracranial-to-central venous pressure gap predicts the responsiveness of intracranial pressure to PEEP in patients with traumatic brain injury: a prospective cohort study

BACKGROUND

Mechanical ventilation (MV) with positive end-expiratory pressure (PEEP) is commonly applied in patients with severe traumatic brain injury (sTBI). However, the individual responsiveness of intracranial pressure (ICP) to PEEP varies. Thus, identifying an indicator detecting ICP responsiveness to PEEP is of great significance. As central venous pressure (CVP) could act as an intermediary to transduce pressure from PEEP to ICP, we developed a new indicator, P_ICGap, representing the gap between baseline ICP and baseline CVP. The aim of the current study was to explore the relationship between P_ICGap and ICP responsiveness to PEEP.

METHODS

A total of 112 patients with sTBI undergoing MV were enrolled in this prospective cohort study. ICP, CVP, cerebral perfusion pressure (CPP), static compliance of the respiratory system (Cst), and end-tidal carbon dioxide pressure (PetCO₂) were recorded at the initial (3 cmH₂O) and adjusted (15 cmH₂O) levels of PEEP. P_ICGap was assessed as baseline ICP - baseline CVP (when PEEP = 3 cmH₂O). The patients were classified into the ICP responder and non-responder groups based on whether ICP increment with PEEP adjusted from 3 cmH₂O to 15 cmH₂O was greater than 20% of baseline ICP. The above parameters were compared between the two groups, and prediction of ICP responsiveness to PEEP adjustment was evaluated by receiver operating characteristic (ROC) curve analysis.

RESULTS

Compared with the non-responder group, the responder group had lower P_ICGap (1.63 ± 1.33 versus 6.56 ± 2.46 mmHg; p <  0.001), lower baseline ICP, and higher baseline CVP. ROC curve analysis suggested that P_ICGap was a stronger predictive indicator of ICP responsiveness to PEEP (AUC = 0.957, 95%CI 0.918-0.996; p <  0.001) compared with baseline ICP and baseline CVP, with favorable sensitivity (95.24, 95%CI 86.91-98.70%) and specificity (87.6, 95%CI 75.76-94.27%), at a cut off value of 2.5 mmHg.

CONCLUSION

The impact of PEEP on ICP depends on the gap between baseline ICP and baseline CVP, i.e. P_ICGap. In addition, P_ICGap is a potential predictor of ICP responsiveness to PEEP adjustment in patients with sTBI.

Initial end-tidal carbon dioxide as a predictive factor for return of spontaneous circulation in nonshockable out-of-hospital cardiac arrest patients: A retrospective observational study

BACKGROUND

Early outcome prediction in out-of-hospital cardiac arrest is still a challenge. End-tidal carbon dioxide (ETCO2) has been shown to be a reliable parameter to reflect the quality of cardiopulmonary resuscitation and the chance of return of spontaneous circulation (ROSC).

OBJECTIVES

This study assessed the validity of early capnography as a predictive factor for ROSC and survival in out-of-hospital cardiac arrest victims with an underlying nonshockable rhythm.

DESIGN

Retrospective observational study.

SETTING/PATIENTS

During a 2-year observational period, data from 2223 out-of-hospital cardiac arrest victims within the city of Vienna were analysed. The focus was on the following patients: age more than 18 years, an underlying nonshockable rhythm, and advanced airway management within the first 15 min of advanced life support with subsequent capnography.

INTERVENTION

No specific intervention was set in this observational study.

MAIN OUTCOME MEASURES

The first measured ETCO2, assessed immediately after placement of an advanced airway, was used for further analysis. The primary outcome was defined as sustained ROSC, and the secondary outcome was 30-day survival.

RESULTS

A total of 526 patients met the inclusion criteria. These were stratified into three groups according to initial ETCO2 values (<20, 20 to 45, >45 mmHg). Baseline data and resuscitation factors were similar among all groups. The odds of sustained ROSC and survival were significantly higher for patients presenting with higher values of initial ETCO2 (>45 mmHg): 3.59 [95% CI, 2.19 to 5.85] P = 0.001 and 5.02 [95% CI, 2.25 to 11.23] P = 0.001, respectively. On the contrary ETCO2 levels less than 20 mmHg were associated with significantly poorer outcomes.

CONCLUSION

Patients with a nonshockable out-of-hospital cardiac arrest who presented with higher values of initial ETCO2 had an increased chance of sustained ROSC and survival. This finding could help decision making as regards continuation of resuscitation efforts.

[Monitoring airway gas in pediatric anesthesia: an experimental model for endotracheal gas measurement]

BACKGROUND

We designed an endotracheal probe for measuring inspired and expired gas fractions during pediatric general anesthesia.

OBJECTIVE

To compare the gas fractions measured by means of intratracheal and extratracheal monitoring.

MATERIAL AND METHODS

The study included ASA 1 patients between the ages of 7 and 12 years under inhaled anesthesia with mechanical ventilation. The following parameters were recorded inside and outside the trachea: inspired and expired oxygen, nitric oxide (N2O) and sevoflurane fractions; the expired and inspired fraction gradients; PaCO2; and end-tidal carbon dioxide (ETCO2). Measurements were taken by an airflow sensor (Pedi-Lite) in the circuit before the point of connection to the endotracheal tube and by an intratracheal probe placed between the tube and the carina. Both sensors were connected to the same monitor. Measurements were taken on intubation and 5, 10, 15, 20, 30, 40, 50, and 60 minutes thereafter. PaCO2 was recorded at the same time. The recorded values were analyzed using the t test and the Pearson product moment correlation coefficient (r), and regression models were constructed using analysis of variance.

RESULTS

Seventy-one patients were enrolled in the study. The mean difference (SD) ETCO2 was 5 (3) mm Hg higher according to endotracheal measurement (P < .005), and that measurement was almost identical (+/-13 mm Hg) to the PaCO2 (P < or = .5). The inspired/expired gradients of endotracheal measurement of oxygen and N2O were 3 (2) points higher (P < .05) than the gradients of extratracheal measurements. In the case of sevoflurane gradients, however, the extratracheal values were higher (mean difference, 0.6 [0.2] points, P < .05). The inspired/expired oxygen and N2O gradients became equal after 18 (3) minutes; the sevoflurane gradients became equal after 8 (2) minutes.

CONCLUSIONS

Intratracheal and extratracheal measurements of the inspired and expired fractions of mixed gases provide different results.

Alternative airway devices for use in children requiring prehospital airway management: update and case discussion

This manuscript reviews the latest literature on alternative airways for use in children requiring prehospital airway management. Case discussions serve as a springboard for discussion of alternatives to bag-mask ventilation and endotracheal intubation for management of ventilation in infants and children in the prehospital setting. Few airway procedures have been studied with any rigor in this setting, and most of the data that are available are extrapolated from adults. Laryngeal mask airway may be the best alternative airway with the most promise to add to the armamentarium of the prehospital provider, but no controlled trial to date has been conducted.