Clinical paperAirway strategy and ventilation rates in the pragmatic airway resuscitation trial
Introduction
Each year over 350,000 persons in the United States experience sudden out-of-hospital cardiac arrest (OHCA).1 Optimal delivery of oxygen and control of ventilation are important components of OHCA resuscitation and the main motivations for airway management interventions such as bag-valve-mask ventilation, intubation and supraglottic airway insertion.2 Inadequate ventilation can result in hypoxemia, hypercapnia, acidemia, alveolar atelectasis and pulmonary shunting.2., 3. However, excessive ventilation can also be harmful in OHCA, increasing intrathoracic pressure, and decreasing venous return, cardiac output and coronary perfusion.4., 5., 6..
Prior studies characterizing ventilation parameters such as ventilation rate and end-tidal carbon dioxide (ETCO2) levels have relied upon discrete measurements or manual assessment of resuscitation records.4 Modern portable cardiac monitors enable continuous real-time recordings of resuscitation parameters such as thoracic impedance, chest compression depth and ETCO2 levels.7., 8., 9., 10., 11., 12., 13. We previously demonstrated the utility of advanced automated signal processing techniques in characterizing chest compressions delivered to OHCA patients.14., 15., 16. There have been few prior studies using similar automated methods to characterize ventilations delivered during OHCA.
The Pragmatic Airway Resuscitation Trial (PART) found improved OHCA outcomes with an airway strategy of initial laryngeal tube (LT) insertion compared with endotracheal intubation (ETI).17 Different airway management techniques may potentially influence ventilation performance, including ventilation rate control. In this study, we sought to determine the association between airway strategy and ventilation rates in the PART trial. We also sought to determine the association between ventilation rates and OHCA outcomes.
Section snippets
Study design
We conducted a secondary analysis of data from the PART trial.17 The Institutional Review Boards of participating institutions approved the parent study under federal regulations for Exception from Informed Consent for Emergency Research (21 CFR 50.24). This post hoc analysis was approved by the Ohio State University Office of Responsible Research Practices.
Setting
The objective of the PART trial was to compare the effect of airway management strategies (initial LT vs. initial ETI) upon adult OHCA
Results
Of 3,004 patients enrolled in the parent trial, CPR process data were available for 2,020 patients, and capnography data of sufficient quality were available for n = 1,010, including 538 (53%) from Philips monitors, 436 (43.2%) from Zoll monitors, and 36 (3.6%) from PhysioControl monitors. (Fig. 2) Of the 13 randomization clusters, 1 cluster had only 3 cases with suitable capnography data, and 3 clusters had no cases with suitable capnography data. Compared with those excluded, cases included
Discussion
Ventilation control plays an important role in OHCA resuscitation, facilitating oxygen delivery and the prevention and treatment of hypoxemia, hypercapnia and acidosis.2 Our study offers important new perspectives of ventilation rates delivered during OHCA. In this subset from the PART trial, EMS personnel delivered ventilations at 6–12 breaths per minute (a range consistent with international care guidelines) in almost 90% of the post-advanced-airway time epochs.22 The limited durations of
Limitations
As discussed previously, this analysis focused on ventilation rate only and could not characterize other key ventilatory parameters such as tidal volume, minute volume and airway pressure. Capnography files of adequate length and quality were available for only one-third of cases enrolled in the PART trial. Few files were available from PhysioControl monitors; we do not know if this was due to practice variation at these EMS agencies or technical issues associated with capturing this
Conclusions
In this post-hoc analysis of the PART Trial, EMS personnel delivered the majority of post-airway ventilations at rates satisfying international treatment guidelines, with only limited episodes of hypo- and hyperventilation. Duration of hypo- and hyperventilation did not differ with airway management strategy. Duration of hypo- and hyperventilation exhibited uncertain associations with OCHA outcomes. Further research is needed to understand the impact of ventilation in OHCA resuscitation.
Sources of Funding
Research Supported by Grant UH2/UH3-HL125163 from National Heart Lung and Blood Institute. This work was partially supported by the Spanish Ministerio de Ciencia, Innovacion y Universidades through grant RTI2018-101475-BI00, jointly with the Fondo Europeo de Desarrollo Regional (FEDER) and by the Basque Government through grants IT1229-19 and PRE 2020 2 0182.
Conflicts of Interest
The authors declare no conflicts of interest.
CRediT authorship contribution statement
Henry E. Wang: Conceptualization, Data curation, Formal analysis, Investigation, Funding acquisition, Methodology, Project administration, Resources, Software, Supervision, Writing – original draft, Writing – review & editing. Xabier Jaureguibeitia: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Software, Writing – review & editing. Elisabete Aramendi: Conceptualization, Data curation, Methodology, Resources, Software, Writing – review & editing, Investigation.
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This manuscript is dedicated to the memory of our dear colleague Unai Irusta.