Critically hypoxic or bradypneic patients need aggressive and effective oxygenation – quickly. In most cases, a standard BVM ventilation or NRB at 15L/min is sufficient to improve oxygenation. However, in a small subset of patients, a standard, unmodified BVM or NRB isn’t enough.
Usually if a patient does not improve with supplemental oxygen alone, the most reasonable explanation is shunt. Physiologic shunt occurs when the lungs are perfused normally but oxygen delivery to the alveoli is inhibited. You should suspect shunt whenever the patients SpO2 remains low despite application of high flow O2. In these cases you need to fully understand the capabilities of your oxygen delivery devices.
Les BVMs Dangereux
- Multiple safety valves on standard BVMs result in room air entrainment within the delivery bag – causing decreased FiO2 delivery during ventilation.
- Almost no BVM or Non-Rebreather delivers 100% FiO2.
- 15LPM flow rate is not a hard upper limit. Use flush-rate oxygenation!
- Any open circuit BVM needs a PEEP valve, regardless of the provider’s choice to deliver PEEP. Failing to do so results in further dilution of FiO2.
- Sit the patient up.
- Utilize airway adjuncts.
- Place the head forward.
- Use a two hands to maintain a mask seal and lift the jaw up.
- Give slow controlled and deliberate breaths.
- Only use about ⅓ of the volume of the BVM.
- Overall goal is to diminish the risk of gastric insufflation while preoxygenating – usually for advanced airway delivery.
- Place a nasal cannula under the BVM at 15LPM.
- Place the BVM at 15LPM, and PEEP at 10.
- The nasal cannula will force the duck bill valve open, and you will deliver CPAP at around 6-8 cm of water.
“True” NRBs: Contains one way valves on each side of the mask, and can deliver near 90% FiO2 to the patient at 15LPM.
“Standard” NRBs: Contains a singular valve on the mask and can deliver only 60-70% FiO2 at 15LPM.
AIME Airway Videos:
Intro Music: Run the Jewels – “Talk to Me” (Instrumental)
Now for the Podcast…
1) Scott Weingart. How to generate constant CPAP with a BVM for Preoxygenation and Reoxygenation. EMCrit Blog. Published on November 4, 2011. Accessed on January 9th 2018. Available at [https://emcrit.org/racc/bvm-preoxygenation-and-reoxygenation/ ].
2) Driver, B. E., Prekker, M. E., Kornas, R. L., Cales, E. K., & Reardon, R. F. (2017). Flush Rate Oxygen for Emergency Airway Preoxygenation. Annals of Emergency Medicine, 69(1), 1–6. https://doi.org/10.1016/j.annemergmed.2016.06.018
3) Groombridge, C., Chin, C. W., Hanrahan, B., Holdgate, A., & Reardon, R. (2016). Assessment of Common Preoxygenation Strategies Outside of the Operating Room Environment. Academic Emergency Medicine, 23(3), 342–346. https://doi.org/10.1111/acem.12889
4) Weingart, S. D., & Levitan, R. M. (2012). Preoxygenation and prevention of desaturation during emergency airway management. Annals of Emergency Medicine. https://doi.org/10.1016/j.annemergmed.2011.10.002