Hyperventilation blows the chances of survival
Hyperventilation of a patient in cardiac arrest has been shown to impact negatively on survival but maintenance of optimal ventilation is not as easy as it may sound. Previous research suggests that rescuers deliver ventilations outside of recommendations during out-of-hospital cardiac arrest (OHCA).
This study investigated whether compliance with ventilation recommendations by ambulance clinicians could be improved using the Zoll Accuvent real-time ventilation feedback device (VFD). In total, 106 participants (paramedic and non-paramedic) undertook simulated advanced life support (ALS) using a manikin on a stationary ambulance. A supraglottic device with catheter mount and ventilation bag were already in situ and defibrillation and cardiopulmonary resuscitation (CPR) feedback pads were applied. Each pair of participants completed ALS scenarios providing asynchronous chest compressions and ventilations over two 2-minute periods. In the first scenario, participants received compression quality feedback but no ventilation feedback; in the second scenario, real-time ventilation feedback was provided.
Primary outcome was % difference in ventilation compliance with and without feedback. Secondary outcomes were differences between paramedic and non-paramedic clinicians and compliance with chest compression guidelines. The median ventilation rate without feedback was 10 (IQR 8–14, range 4–30) compared with 9 (IQR 9–9, range 6–17) with feedback; median tidal volume without feedback was 630 ml (IQR 518–725, range 201–1114) compared with 546 ml (IQR 531–560, range 490–750) with feedback. The proportion of clinicians ~50% compliant with European Resuscitation Council ventilation recommendations were significantly greater with ventilation feedback compared to without (91% vs. 9%). Paramedics out performed non-paramedic clinicians with and without feedback.
The authors conclude that though ambulance clinician baseline ventilation quality was frequently outside of recommendations, it could be improved with the use of a VFD. There are several limitations within this study that need to be considered but it is an interesting piece of work that highlights the need for patient-based studies.
Talking about collars…
The routine use of c-collars as part of prehospital immobilisation has been the topic of ongoing debate and discussion, with some UK ambulance trusts reducing their routine use. It has been suggested that there is limited evidence to support their use, with reports of increased intracranial pressure and poorly fitted collars providing little reduction in a range of movement (Hawkridge et al, 2020; Hodgett and Ward, 2020). Despite this, current guidelines advise their use, and although self-extrication is acceptable, the use of a c-collar in this situation is unclear if an injury to the cervical spine cannot be cleared. Nutbeam et al (2021) recently looked to address this issue, using biomechanical data to measure a range of movement during self-extrication. A variety of situations were evaluated using 10 volunteers, with a reasonable range across age, height and weight, although all were healthy and represented a non-injured patient, able to self-extricate and understand instructions provided. A total of 392 extrications were recorded, with most movements identified in cervical and lumber spine data when no collar or instructions on how to self-extricate were provided. A key finding was that where a c-collar was worn, but no instructions provided, movement was less and considered statistically significant. In relation to practice, this appears to align with current JRCALC guidance; however, the recognised limitations may raise some questions. The use of healthy, uninjured volunteers does not represent all involved in road traffic collisions; an undamaged car may be easier to self-extricate from and if a patient can self-extricate, they may have already done so. Yet, if self-extrication is possible, and there is a suspicion of a cervical spine injury, this study suggests cervical and lumber spine movement is less if a correctly fitted c-collar is used and no instructions provided. It appears the subsequent removal of a c-collar after full immobilisation is an option, with this study adding to the discussion of who should self-extricate.