2024 Airway Changes

The preponderance of airway technique and equipment reviews are performed in civilian Emergency Medical Services (EMS), and the primary mechanism of airway injury is Out of Hospital Cardiac Arrest (OHCA).  There are several critical differences between the EMS setting and the tactical environment including medic training competency, equipment carrying capacity, tactical considerations, environmental considerations, combat injury patterns, and transport times to definitive care facilities.

Patient placement in various positions impacts airway patency, oxygen saturation, and potentially cardiac output, with historical and recent studies highlighting the complexities of managing unconscious or sedated individuals. The prone position was historically preferred for clearing airways, while modern studies show the lateral position may be equal or superior to supine for maintaining airway patency and reducing apnea events, as evidenced by a meta-analysis focused on sedated and obstructive sleep apnea patients. Despite these findings, considerations for potential spinal injury, pelvic fractures, and other significant injuries complicate the choice of patient positioning. Effective medical provider judgment is crucial, especially when balancing the benefits of the recovery position against the risks of exacerbating injuries. Moreover, head and chin placement play a critical role in airway management, with the head extended position showing the greatest improvement in airway patency. While the recovery position's effect on cardiac output remains inconclusive, it's emphasized that allowing patients to self-manage their airway can benefit ventilation and cardiac output, highlighting the nuanced decision-making required in patient positioning to optimize outcomes.

Battlefield medics should continue to place unconscious patients in the recovery position as first line treatment if the patient is unable to manage their own airway. The head should be tilted back (chin away from chest); presenting head extension to minimize airway occlusion. Additionally, protocols should continue to advocate for the conscious patient to self-manage by assuming the best tactically relevant position to maintain a patent airway.

Advanced airway management, including the use of I-gel® and LMA-Supreme®, face challenges in the prehospital battlefield setting, with significant debate over the best approach for airway management in trauma patients. The vast majority of extraglottic airway studies and data are from Out of Hospital Cardiac Arrest (OHCA) patients with very little data correlating to trauma casualties.  Studies suggest that the success of advanced airway placement does not necessarily correlate with improved survival rates, raising questions about the current practices of prehospital advanced airway management. This complexity underscores the need for careful consideration of the type of airway management device and technique used in the prehospital setting, balancing ease of use, environmental factors, and the potential impact on patient outcomes.

The extraglottic airway (EGA) offers several advantages, including effective securing of the tongue, soft palate, and epiglottis, cost-effectiveness, ease of training, high placement success rates, and better ventilation compared to bag-valve-mask (BVM) devices, along with protection against blood ingress from injuries above the cuff. However, its suitability for battlefield conditions is limited due to its inability to protect against burns below the epiglottis and ineffectiveness in severe airway injuries that disrupt airway anatomy. Concerns also arise from environmental vulnerabilities of gel-filled EGAs and aeromedical evacuation challenges with air-filled cuffs. Moreover, studies suggest that the survival rates for trauma patients receiving EGAs prehospital may be comparable or inferior to those managed with BVMs, and the use of advanced airways without anesthesia in trauma settings is linked to poor outcomes. Consequently, military airway management protocols need to account for the unique challenges of battlefield casualties, diverging from practices common in civilian EMS that primarily deals with cardiac arrest cases.

The recommendation to remove the EGA from the TCCC guidelines is due to lack of protection against battlefield airway injuries, environmental considerations, lack of evidence demonstrating increased survival versus BVM, and the precedent that prehospital trauma advanced airway insertion without significant sedation demonstrates very high patient mortality.

Cricothyrotomy, a critical procedure in airway management protocols, has a success rate of only 68% in military settings, military medics perform the procedure nearly double the rate performed by civilian counterparts due to differing injury profiles and the skill levels of providers. Despite the proliferation of cricothyrotomy techniques and devices, none have demonstrated clear superiority, leading to varied recommendations for best practices. The open surgical technique remains highly recommended for maximizing anatomic exposure and minimizing complications. However, literature and expert guidelines, including those from the Difficult Airway Society, offer conflicting views on the optimal approach, emphasizing the need for more definitive research to establish the most effective cricothyrotomy technique.

Due to the lack of battlefield-appropriate definitive airway solutions, it is imperative that medics increase knowledge of proper indications for performing surgical airways and training proficiency of the cricothyrotomy technique. Current documented military prehospital cricothyrotomy success rates are unacceptable.

Success rates for cricothyrotomy in pre-hospital settings, according to various studies, range from 68% to 94.2%, with a notable 33% failure rate reported among battlefield medics at the point of injury. End Tidal Carbon Dioxide (EtCO2) monitoring, particularly through digital capnography, has proven to be an effective method for confirming endotracheal tube placement, although cost constraints limit its availability across military units. Cost-efficient colorimetric devices offer alternatives but are subject to limitations such as delayed feedback, susceptibility to false positives from gastric content exposure, and sensitivity to high humidity, making ETCO2 monitoring a more reliable indicator for successful airway management compared to traditional observational methods.

Due to the criticality of the cricothyrotomy procedure and documented poor success rates, confirmation of a cric procedure is essential. Digital capnography is the preferred method, due to its superior monitoring capability.

The European Resuscitation Council Guidelines 2021 advocate for delivering regulated positive pressure ventilations of 5-8 ml/kg of ideal body weight, translating to approximately 410-650 ml for an ideal body weight 180 lb male, with the American Heart Association recommending a 600 ml tidal volume. However, standard adult Bag Valve Masks (BVMs) often exceed these recommendations, potentially causing lung injury and increased mortality in patients with acute lung injuries by delivering significantly higher tidal volumes. Studies have shown that pediatric BVMs, with lower resuscitator volumes, provide more consistent and appropriate ventilation for adult patients, reducing the risk of exceeding tidal volume thresholds compared to adult BVMs. Additionally, pediatric BVMs have been found to deliver closer to recommended tidal volumes with less risk of under-ventilation and develop less peak airway pressure, though they may result in slightly lower PaO2 levels on room air. These findings suggest that using pediatric or smaller-sized BVMs for adult patients can offer safer and more effective ventilation in prehospital settings, including battlefield environments, by aligning more closely with recommended ventilation parameters.

Previous studies have shown that mean expired tidal volumes are between 42-73% of the BVM’s resuscitator bag capacity, using a one-handed method. With that in mind, it is prudent to use a BVM with a resuscitator bag capacity of 1000ml. This capacity most likely meets the tidal volume recommendations set forth by the AHA and ERC using a one-handed squeeze method. This recommendation is also within the range supported by the National Association of EMS Physicians (NAEMSP).

Extrinsic Positive End Expiratory Pressure (PEEP) enhances lung compliance by preventing alveolar collapse and atelectasis, leading to improved gas exchange and reduced work of breathing, particularly beneficial in acute lung injuries (ALI), Acute Respiratory Distress Syndrome (ARDS), and Primary Blast Lung Injury (PBLI) anticipated in future conflicts. PEEP's utility, however, varies across patient conditions; while it doesn't significantly affect short-term anesthesia patients' oxygen saturation, it has shown benefits in reducing atelectasis and improving PaO2 in certain surgical patients, without markedly improving mortality or hospital stay lengths in non-ARDS patients. Despite these findings, PEEP's application requires caution, particularly regarding increased intrathoracic pressure's effects on cardiac output and the challenges in maintaining effective ventilation, especially in patients with dynamic airway collapse or obstructive lung conditions. Studies suggest that while PEEP can enhance lung recruitment, its effectiveness and safety require careful consideration of the patient's condition, with recommendations for its use in specific settings like PBLI incorporating a protective ventilation strategy that includes carefully managed PEEP levels to mitigate potential risks.

Due to the lack of ALI & ARDS patients in the battlefield setting, lack of sophisticated ventilatory tools, concern of intrathoracic pressure at higher PEEP settings, limited training time for the provider population, and overall insufficient evidence to support a decrease in mortality risk, current evidence DOES NOT support routine use of PEEP within the TCCC provider population at this time.

The Nasopharyngeal Airway (NPA) is recognized for its role in managing airway patency in unconscious or semi-conscious patients by keeping the soft palate and tongue from obstructing the posterior oropharynx. Despite its widespread use and ease of training, there's a notable gap in published data beyond its application for obstructive sleep apnea (OSA) patients. Studies indicate that the NPA's effectiveness is not solely dependent on preventing tongue occlusion but also does not address potential epiglottis obstruction. Some research emphasizes the importance of correct NPA length, correlating it with patient height to ensure efficacy and minimize complications like airway obstruction and gag reflex stimulation. However, other studies challenge these findings, suggesting that various body measurements could predict optimal NPA size, advocating for adjustable length NPAs. Despite its potential, the NPA has limitations, including difficulty in determining the correct size, risks of mis-sizing, and the inability to protect against certain types of airway injuries, making its effectiveness and utility in prehospital battlefield environments questionable. Additionally, absolute contraindications such as basilar skull fractures present significant risks in combat settings, highlighting the complexities of NPA use in emergency and military medicine despite its potential benefits in airway management.

Based off feedback from SMEs and small in-hospital BVM study, there is likely benefit for the NPA’s inclusion in the respiration phase while providing positive pressure ventilations via BVM.

Rapid Sequence Induction (RSI), though not recommended by the Committee on Tactical Combat Casualty Care (CoTCCC), has been scrutinized for its applicability and risks in prehospital trauma care, particularly concerning the use of ketamine-only anesthesia. A 2019 study reviewing a protocol for ketamine sedation followed by extraglottic airway (i-gel) placement reported an 87.5% compliance rate among paramedics, indicating a feasible approach to sedation without paralytics. However, a case series involving military trauma patients undergoing RSI showed a high risk of fatal outcomes, with most subjects experiencing pulseless arrest post-procedure, often after signs of hemodynamic instability, highlighting the procedure's potential lethality in patients with hemorrhagic shock. These findings led to cautionary stances against the routine use of RSI by combat medics in the field, reflecting concerns about the safety and efficacy of RSI in combat-related trauma care.