1. Standards
   Data are insufficient to support a treatment standard for airway, ventilation, and oxygenation management techniques in the out-of-hospital or tactical environment.
2. Guidelines
   Routine or prophylactic hyperventilation is not recommended and should be avoided.
3. Options
   1. Airway management is crucial for the TBI patient and oxygen tension should be monitored and maintained at a SaO₂ ≥ 90. When the assessment indicates an obstructed airway, the management depends on the skills of the health care provider.
   2. Adequacy of ventilation is measured by pCO2 or to a lesser degree of accuracy by end tidal carbon dioxide (EtCO₂) measurement. Endotracheal intubation (ETI) by an experienced provider using direct laryngoscopy (DL) is accepted as the optimal method of airway control. There is evidence that the Intubating Laryngeal Mask Airway (ILMA®), the Combitube®, and the Fiberoptic Intubation device (FI) may be useful for the less experienced care giver.
   3. While a chest radiograph is the traditional way to confirm endotracheal tube placement, there is evidence that the Self-Inflating Bulb (SIB) device and/or measurement of EtCO₂ (except in a cardiac arrest situation) are useful tools for confirming placement along with auscultation of the chest (when the environment would allow and when chest radiography is not an option).
   4. Hyperventilation should only be done if patients are exhibiting signs of cerebral herniation such as posturing with asymmetric or bilateral dilated pupils. If done, hyperventilation is defined as 20 breaths per minute for adults. Hyperventilation should be discontinued as soon as signs of herniation normalize.

While primary and secondary hypoxia and both hypo- and hypercapnea have been strongly associated through multiple studies with increased morbidity and mortality of patients suffering traumatic brain injury,1-11 it is less clear how to prevent hypoxia or hyper- and hypocarbia in the head injured patient.12 This is especially true in the out-of-hospital setting. Active monitoring of SaO₂ and EtCO₂ have been shown to help. The use of positive pressure ventilations with or without endotracheal intubation may be associated with adverse effects secondary to increased interthoracic pressures. Therefore, lower tidal volumes and longer expiratory times may be needed than is current standard practice.

High FIO2 will compensate to maintain PaO2 but PaCO₂ may suffer. Securing of the airway solely to prevent aspiration has lately been questioned, but there may be many other indications to isolate the airway in the battle injured patient. Patients with a Glasgow Coma Scale (GCS) score ≤ 9 should be intubated if possible.13 Endotracheal intubation in the prehospital setting has itself been associated with both improved outcome and harmful side effects. The sum of these studies seems to point to skill of the practitioner as the key difference in patient outcome. Therefore, endotracheal intubation, while still the gold standard of airway management, presents dangers in unpracticed hands. An increasing number of studies correlate education time and intubation experience to success and outcome. Higher success rates with medication-assisted intubation may be negated if tube migration cannot be monitored, prevented, or corrected.

For the purposes of discussing advanced airway management in the far forward environment, it is important to note that there exist many different levels of practitioner and many levels of care that are rendered on the battlefield. Equipment logistics, initial and sustainment training opportunities, and local medical treatment authorizations for non-credentialed providers are among the differences that may account for varying treatments provided to similar patients across the levels of care.

A literature search from 1970 to 2005 was conducted using the terms "airway" or "oxygenation" or "intubation" or "advanced airway," and "prehospital care" or "EMS" or "emergency medical services," and "traumatic head injury" or "traumatic brain injury" or "TBI." Reference to the Guidelines for Prehospital Management of Traumatic Brain Injury chapter "Treatment: Airway, Ventilation, and Oxygenation" was also made. That process of literature review produced 187 references, 26 of which were directly relevant to outcome analysis and clinical orientation.

The amount of scientific evidence available in the medical literature regarding airway, ventilation, and oxygenation management in the tactical or combat arena is meager. We therefore used the civilian hospital, prehospital, and aeromedical literature to help us with our recommendations.

Hsiao et al.13 demonstrated a correlation between GCS score and the need for intubation in the field or within 30 minutes of ED arrival, and correlated the need for intubation and GCS score with positive CT scan findings indicative of TBI. This retrospective evaluation included patients with a GCS ≤ 13 as measured in the ED, as well as patients who were intubated in the field and had a GCS scored by the field medical providers. Of note, the lowest reported field GCS was used for this study. GCS scores grouped patients as follows: 3-5, 6-7, 8-9, and 10-13. Patients with the lowest GCS scores had the highest need for emergent intubation (in the field or ED) and had the highest number of positive CT scans. Hsiao concluded that patients with a GCS ≤ 9 are candidates for aggressive airway management, including intubation and use of pharmacologic agents, if needed.

While endotracheal intubation is widely considered the definitive method of prehospital airway management, there are several studies that examined the use of other airway devices to successfully manage the airway. In a prospective simulation of emergency resuscitation, Dorges et al.14 showed success of placement with other airway devices. Forty-eight apneic patients were successfully intubated with various advanced airway devices including LMA's, Combitubes®, and cuffed orotracheal airways. All patients in this study were successfully ventilated using bag-valve mask technique subsequent to successful placement of the airway adjunct. This trial showed that paramedics could successfully use these alternatives for successful placement and management of the airway.

Another 1997 study examined the use of the Upsherscope® to help facilitate intubation versus the traditional method of direct laryngoscopy.15 Fridrich and his colleagues did not find the Upsherscope® to be of greater benefit than direct laryngoscopy. However, Langeron et al.16 found that use of the Intubating Laryngeal Mask Airway (ILMA®) did have some benefit to successful placement of an endotracheal airway. This prospective randomized study examined 100 patients with at least one difficult airway intubation criteria. Time to intubation, hypoxic events, and success of intubation were all compared with a fiberoptic intubation (FIB) group. Similarly high success rates were obtained in both the ILMA® and FIB groups: 94% versus 92%. There was no significant difference between time to intubation and the number of attempts for each group. The one important significant difference to note was a more frequent incidence of adverse events in the FIB group: 18% versus 0%, P < 0.05.

Biswas et al.17 also examined the use of the ILMA®, but in the lateral position. Under general anesthesia, 82 adult patients were intubated using the ILMA® while they were placed in either the left or right lateral position. 86% of patients were intubated on the first attempt, and the remaining were all intubated on the second attempt. He concluded that the ILMA® is a useful alternative to the FIB. It is also a good option for intubating non-supine patients that could be encountered in the far forward environment.

Deibel et al.18 analyzed the performance of airway management skills of EMS personnel and emergency department physicians using mannequins. These trials were performed under simulated confined space scenarios. Time to successful intubation was examined and determined in the three groups: endotracheal intubation, Combitube®, and LMA. Time to successful ventilation for each adjunct was 70 seconds, 51.3 seconds, and 43.2 seconds, respectively, showing that the Combitube® and LMA are viable alternatives to endotracheal intubation. Not only are the LMA and ILMA® good alternatives for experienced airway providers, but for less experienced technicians as well. Choyce et al.19 examined their uses and determined that both adjuncts are good options for use in less experienced medical personnel.

The performance of endotracheal intubation under emergency situations has a higher mortality and increased incidence of complications compared to non-emergency situations. Schwartz et al.20 prospectively examined in-hospital emergency intubations in 297 patients. Patients undergoing emergency endotracheal intubation had a higher incidence of aspiration, pneumothorax, and mortality.

An Israeli study by Ben Abraham et al.21 investigated the potential causes of failure by combat medical officers in securing the airway of a multiple injury patient. In examining 250 soldiers, it was found that most had uncomplicated airways and that difficult intubations were unlikely to be associated with anatomical causes. Complicated tactical scenarios and efficient skills of the providers were identified as the most important factors that contribute to in-field failures to secure airway control.

It has long been thought that skills performance declines without practice, use and/or re-training. In a 2000 prospective randomized controlled trial, Kovacs et al.22 trained a group of 84 students in endotracheal intubation. These participants had no prior training or experience in advanced airway management. Time to successful intubation was measured and used as the benchmark for successful performance. Skills performance did indeed decline over time as measured at 16, 25, and 40 weeks post initial training. Therefore, it is advisable that personnel performing endotracheal intubation have refresher training in these advanced skills.

Aside from proper skill performance and technique, personnel performing intubations should always confirm placement of the endotracheal tube. The auscultation of breath sounds in the lung fields and the absence of sounds over the epigastrum have long been clinical methods of confirming endotracheal tube placement. However, the use of other placement confirmation devices is important to the overall treatment of the intubated patient. Several groups have looked at confirmation devices.

The self-inflating bulb (SIB) device and the end-tidal carbon dioxide detector (EtCO₂) are both accepted secondary methods for insuring proper placement of the endotracheal tube. Grmec and Mally23 found that auscultation of endotracheal tube placement alone was not sensitive enough. He found a 10% error rate among placements where auscultation was the only method of confirmation while a 0% error rate among placements confirmed with EtCO₂.

In a prospective study of emergency physicians, Kasper and Deem24 found that the SIB successfully identified 100% of all misplaced esophageal intubations. Of 300 consecutive cases, the SIB detected the 19 misplaced endotracheal tubes. Tanigawa et al.25 also found similar results. SIB correctly identified 100% of patients with a misplaced esophageal intubation, but did not correctly identify 72% of the misplaced tracheal intubations. Therefore, use of the EtCO₂ detector in conjunction with the SIB is advisable.

Proper ventilation is also crucial to the management of the TBI patient. In a 2003 study, Helm et al.26 evaluated the incidence of hypo- and hyperventilation after instituting capnography during prehospital transport. Of 97 patients included in the study, 71 had head trauma. The incidence of adequate ventilation (PaCO₂ = 35-45 mm Hg) was 63.2% in the monitored group versus 20% in the monitor-blind group; the incidence of hypoventilation (PaCO₂ > 45 mm Hg) was 5.3% versus 37.5% respectively; and the incidence of hyperventilation (PaCO₂ < 35 mm Hg) was 18% versus 17% respectively. Proper ventilation could be guided by the use of the EtCO₂ monitors by prehospital personnel.

The assessment and treatment of airway, ventilation, and oxygenation problems must be interwoven step by step to successfully manage the TBI patient. Treatment of an obstructed airway must precede the assessment of ventilation. Similarly, the treatment of a patient who is not breathing must precede the assessment of circulation. This concept in the combat scenario is the same as in the civilian arena. Tactical and logistical considerations dominate the tools available to address these issues for the combat injured, with different provider skill levels and treatment capabilities existing at each level of care. Regardless of the level of care, every effort must be made to maintain the SaO₂ above 90% in suspected TBI patients. It is equally important to avoid hyper- and hypoventilation in these patients.

A patent airway should be assured and endotracheal intubation performed for patients with a GCS < 9 or for those who are unable to maintain or protect their airway. Evidence indicates that routine hyperventilation should not be performed. If ventilatory assistance after endotracheal intubation is provided, a respiratory rate of 10 breaths per minute should be maintained. After correction for hypoxemia or hypotension, if the patient shows obvious signs of cerebral herniation, such as extensor posturing and pupillary asymmetry or bilateral dilated pupils, the medical provider should hyperventilate the patient at a rate of 20 breaths per minute. This hyperventilation may be performed as a temporizing measure until the patient arrives at a medical facility when blood gas analysis will guide the ventilation rate. We believe that end tidal CO2 monitors or the use of the SIB tool will help avoid improper endotracheal tube placements. Further EtCO₂ monitors will help avoid hyper- or hypoventilation.

The airway/ventilation/oxygenation treatment training for military personnel (whether they be combat medics, paramedics, nurses, or physicians) should highlight TBI as a special consideration because of its long term impact on patient outcome. Evidence suggests that airway management skills decline early after initial training. Independent practice combined with periodic feedback should be encouraged. New and emerging simulation technologies show promise for practical skills training and education.

1. Difficult as they may be to execute, prospective trials of airway management, ventilation, and oxygenation technique and assessment tools in the tactical and combat environment are needed. Future development of field practical and reliable monitoring equipment will solve some of these problems.
2. Monitoring equipment that is of lighter weight, rugged, simple to use, and minimizing of power consumption will be helpful in the tactical (and standard EMS) environment.
3. Medications to facilitate intubation that have less untoward effects, are easier to reverse, and have no storage problems will improve airway and ventilatory management in the field.
4. Prospective randomized trials of teaching and learning for practitioners of airway management will also help to define what level of intervention can be mastered and maintained by medical personnel.
5. Studies are currently ongoing and standards are changing regarding the effects of positive pressure ventilation on venous return and cardiac output. The results of these studies may necessitate changes in current practices of airway and ventilatory management. Development of ventilators with the same attributes as the monitoring equipment may also prove useful in combat when continuous manual ventilation is impractical.