800px-Motorola_ApcorBy Philip Neuwirth, BS, MICP, CCEMTP, FP-C

In the early 90’s, the Apcor Radio was used to connect prehospital providers with medical control. We used half spine boards and the Thomas Half Ring for our trauma patients; The Self Inflating Bag Valve (BVM) was the device used to oxygenate and ventilate patients, and we used micro drip sets to manually titrate drugs like Lidocaine and Dopamine. So here we are in mid-2016; IV pumps are a standard of care, we use cell phones to communicate with base physicians, half spine boards were replaced by the KED (now all in our rearview mirror,) and we use devices like the Hare Traction Splint, instead of the Thomas Half Ring. However, many Air Medical Programs [and ALS units] continue to use one of the most dangerous pieces of equipment in the pre-hospital setting, the Self-Inflating Bag Valve [BVM]. I hope by now all Specialty Care Transport Units (SCTU’s) and Air Medical Programs use mechanical ventilators for intubated patients during interfacility transports, but many do not, for patients intubated on scene flights. The recent unscientific poll I conducted on Twitter, only 44% of Air Medical Programs, who responded use mechanical ventilators routinely on scene flights.

For those not familiar with using micro drip sets to manually titrate drugs, this is how we did it. Lidocaine, as an example, was prepared by mixing:

  • 1 Gram in 250 mL D5W
  • 1000 mg / 250 mL = 4 mg/mL
  • Using a 60 gtt set – 60 gtts/min = 1 mL
  • 1 mL = 4 mg

So, if our orders were to give our patient 2 mg/min, [using the “roller ball”] we would count 30 drops in the drip chamber over 60 seconds. As you can imagine, that took time, was very unscientific and quite dangerous. So in the late 90’s early 2000’s, someone realized that was not good patient care and was not equivalent to the care given in the hospital. After all, we were hospital based and an extension of the Emergency Department.

The BVM is just like using a roller ball to titrate drips – DANGEROUS!  Studies of prolonged manual ventilation with a bag-valve device is harmful and often increases patient mortality [1]. We are “resuscitating” our patients with a device that delivers an unknown volume of air, which varies with every squeeze of the bag. The rate of [whatever] volume delivered changes, especially during a critical incident and that job often given to the least qualified person, basic life support (BLS). So, the potential to deliver higher than necessary tidal volumes in conjunction with higher than necessary respiratory rates is the recipe to deliver very high airway pressures. To add insult to injury (no pun intended), many programs are not using PEEP valves (34% in my poll), and you can’t titrate FIO2, which we now know, can be harmful to patients.

Now, I know this will spark some controversy, especially for those not comfortable using a mechanical ventilator, but let’s look at reality. You intubate a patient in the back of an ambulance, confirm your tube placement and provide post sedation & analgesia. You remove the patient from the ambulance and transfer the patient to your aircraft stretcher. You move the patient to the aircraft and prepare to load. If you are flying in an EC-135, you have to stop ventilating your patient (disconnect the BVM) and slide the patient into the aircraft. Someone then has to walk around the aircraft, enter the side door, reconnect the BVM, and connect to onboard O2. You have just lost all the alveoli that you recruited after intubation. You then have to repeat that same process when you arrive at the hospital. By having the patient on a ventilator, you never lose that alveoli recruitment and have all the benefits listed below.

Now there are times in emergency medicine when a bag valve mask (BVM) is appropriate, like power failure, equipment failure, MCI, and short term ventilation <10 min. Other than those few reasons, “bagging” an intubated patient is a bad idea.

By using a mechanical ventilator in the prehospital [scene] setting, non-invasive ventilation (NIV) can be initiated for pre-oxygenation (for patients that can’t maintain an O2 sat >94%) and then immediately mechanically ventilate your patient post intubation. This provides simple monitoring and more control over airway pressure, ETCO2 and FIO2. Also, using a mechanical ventilator will free up a provider to perform other tasks.

For hospitalized patients, mechanical ventilators have been shown in studies to provide more reliable ventilation during intra-facility transports (i.e., trips to CAT scan, the cath lab, OR, etc.) when compared to manual ventilation [2]. Although not scientifically supported for patients intubated in the prehospital setting, it’s just a matter of time. The environment in which a patient becomes intubated is inconsequential.

There are several transport ventilators designed and built just for the prehospital environment. The ReVel ventilator, as an example, is a portable ventilator weighing only 9.5 lb yet features the same power and synchrony as a complex critical care ventilator. 

Take home point: Ventilating an intubated patient with a BVM is dangerous; it doesn’t allow you to monitor minute ventilation, airway pressures (unless you add a pressure manometer) or titrate FIO2. If you are a critical care provider that usually says, “Let’s just bag the patient, it’s easier,” you may want to reconsider that thought process and think what’s best for the patient. If you are uncomfortable using a mechanical ventilator, it’s time to seek additional education or ask a coworker for some help. It’s time that ALL pre-hospital intubated patients receive the same standard of “hospital” care and receive mechanical ventilation. 

References

  1. Maharjan, R. K., R. P Aacharya, and P. N. Prasad. “Impact Of Duration Of Prolong Manual Bag Ventilated Patients In The Emergency Service.” Journal Of Institute Of Medicine 36.2 (2014): 57-65.
  2. Gervais HW, Eberle B, Konietzke D, Hennes HJ, Dick W. Comparison of blood gasses of ventilated patients during transport. Crit Care Med. 1987; 15:761-763.
  3. Walls RM, Brown CA 3rd, Bair AE, et al. Emergency airway management: a multi-center report of 8937 emergency department intubations. J Emerg Med 2011; 41:347.
  4. Weiss SJ, Ernst AA, Jones R, Ong M, Filbrun T, Augustin C, et al. Automatic transport ventilator versus bag valve in the EMS setting: a prospective, randomized trial. South Med J. 2005; 98:970-976.
  5. Hyzy RC. Physiologic and pathophysiologic consequences of mechanical ventilation.  In: UpToDate, Parsons PE and Finlay G (eds).  UpToDate, Waltham, MA, 2013.
  6. Hyzy RC. Physiologic and pathophysiologic consequences of mechanical ventilation.  In: UpToDate, Parsons PE and Finlay G (eds).  UpToDate, Waltham, MA, 2013.

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