Prehospital emergency care: OXYGENATION

CarolinaFireJournal - By James Winslow
By James Winslow
04/24/2015 -

I wanted to review one of the most important areas of prehospital emergency care, oxygenation. If a prehospital provider cannot oxygenate his or her patient then the patient will die. Many providers automatically think they should go to an endotracheal tube or a blind insertion device when presented with a severely hypoxic patient. This is often not the case. A recent article by Weingart and Levitan in the “Annals of Emergency Medicine” changed how I practice both prehospital and emergency medicine. The article is titled “Preoxygenation and Prevention of Desaturation during Emergency Airway Management.” The article emphasizes two very important concepts. The first concept is that there are multiple noninvasive ways to drastically increase a patient’s oxygenation. The second concept is that if a provider does not address severe hypoxia before administering paralytics and or sedatives to facilitate an intubation then there is a high risk that the patient can go into a cardiac arrest.


There are three fairly easy ways that oxygenation can be increased. The first method is by simply sitting the person up. The second method involves 15 liters per minute via nasal cannula. The third method utilizes a very cheap PEEP valve attached to a bag valve mask. These three simple methods can greatly improve a patient’s oxygenation.

Sit the Patient Up

When a person is lying flat it is more difficult for them to fully expand their chest. This is especially true if the patient is obese or pregnant. Also when a person is supine the increased pressure from the abdomen causes many of the alveoli to collapse, which can further decrease oxygenation. One study showed that for sedated and paralyzed patients it took an additional 103 seconds to drop their oxygen level versus the supine group. Sitting a patient up during preoxygenation is important. Also if an intubation is performed the patient — when possible — should be kept sitting up until the last possible moment before the intubation.

Crank Up the Nasal Cannula

A nasal cannula cranked up to 15 liters per minute can greatly increase the amount of oxygen a patient is receiving. If a patient is spontaneously breathing the patient should first receive a non-rebreather (NRB) mask. The NRB will only provide the patient with about 60 percent oxygen. If the patient still has low statistics then 15-liter nasal cannula can also be added. An even more important use of 15 liter per minute nasal cannula is during rapid sequence intubation. Even if a patient is paralyzed and apneic a nasal cannula set at 15 liters per minute will give the patient close to 100 percent oxygen. Until I read the Weingart article I was not aware of this. The article states that under optimal conditions with 15 liters of nasal cannula it can take a patient 100 minutes, not seconds but minutes, to drop his or her oxygen saturations. I see very few downsides to using a nasal cannula to provide passive oxygenation. The cannula does not get in the way and it provides a significant safety margin.

PEEP Valve

A PEEP valve can serve two important functions. First, it can provide positive pressure in the lungs and open up collapsed alveoli as well as push fluid out of the lungs. This alone can greatly improve oxygenation. In general if a patient’s statistics do not come up after three or four minutes of a NRB then they have a shunt physiology possibly from fluid filled or collapsed alveoli. If there is a tight bag valve mask seal provided and a PEEP valve is attached then the providers are basically providing CPAP to the patient. This can be done while the patient is still spontaneously breathing. Second, a PEEP valve allows providers to administer much higher levels of oxygen to their patients. With most bag valve masks the patient only receives room air unless being actively bagged. A bag valve mask/PEEP valve combined with a nasal cannula set at 15 liters per minute gives 100 percent oxygen. The BVM/PEEP valve/nasal cannula combination will greatly improve a provider’s ability to oxygenate their patient.

Rolling the Dice

If a provider attempts to intubate a patient with paralytics and sedatives when a patient’s pulse oxygen saturations are below 92-93 percent there is a very good chance that the patient will go into cardiac arrest. This is because once the patient becomes apneic from the sedatives/paralytics the oxygen saturations will rapidly drop. On the oxygen disassociation curve the curve gets very steep at 90-92 percent. At this point the statistics can drop very quickly. Below about 93 percent there is little to no safe period of apnea for an intubation to take place. It is very important for providers to resuscitate their patients appropriately before attempting advanced and possibly dangerous procedures such as rapid sequence induction. One possible way to help providers better resuscitate their patients prior to intubation could possibly involve sedation with ketamine. Ketamine normally does not compromise airway protective reflexes or respiratory drive. Sedation with ketamine may better allow providers to provide lifesaving interventions with a bag valve mask. Either way providers are urged to exercise great caution if attempting an RSI when oxygen saturations are below 92 percent. Some ways to address low saturations are sitting the patient up, higher flow nasal cannula and PEEP valves. I strongly recommend the Weingart article which has other helpful strategies in addition to the ones described above.

Dr. Winslow graduated from Emergency Medicine residency from UNC-Chapel Hill in 2002 and completed his EMS Fellowship in 2003. He has worked at Baptist Hospital in Winston-Salem for the past 11 years. He was appointed as the Medical Director of the NC Office of EMS in 2011. Before serving as state medical director he was Assistant Medical Director for Forsyth and Orange County EMS in North Carolina and Medical Director of Person County EMS. This document contains all protocol, procedures, and policies for all EMS agencies in North Carolina.(Weingart SD, Levitan L. R. (2012). Preoxygenation and prevention of desaturation during emergency airway management. Annals of Emergency Medicine, 165-75.)
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