The Matter of Bags

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Danelle Howard
Danelle Howard
Registered Respiratory Therapist, cross-trained in the Pulmonary Lab, caring for critically ill patients one breath at a time. Professional interests: mechanical ventilation, capnography, and waveforms.
Rahel Gizaw
Rahel Gizaw

Emergency Medicine Resident and MedED Enthusiast. Learning and teaching medicine one doodle at a time!

The Pre-brief

Protective lung ventilation is the current standard of care for mechanical ventilation targeting tidal volumes of 6mL/kg of predicted body weight and plateau pressures less than 30cmH2O.  But why is this the standard of care?  Evidence-based practice has shown that lung-protective ventilation using low tidal volume ventilation (LTVV) improves clinical outcomes due to fewer pulmonary complications and a reduction in mortality and morbidity. 

Why is LTVV such a big deal?

Volutrauma is a mechanism of ventilator-induced lung injury (VILI). Volutrauma causes structural lung damage.  Overdistention causes shear stress on the epithelial cell layer causing inflammation contributing to (VILI). It also can cause alveolar rupture leading to cell death.  Volutrauma doesn’t just affect the lungs. Cardiac preload can also be affected as Volutrauma can cause an increase in intrathoracic pressure, ultimately reducing blood pressure.

What about the BVM?

We use best practice and ventilate with LTVV while on mechanical ventilation, but when it comes to manually ventilating with a BVM, that practice goes out the window. But it shouldn’t.  If we mechanically ventilate with 6ml/kg, we should try to match that with the BVM. Lung injury can still occur due to Volutrauma by the BVM. We have learned that tidal volume is an essential determinant of the clinical outcomes of mechanically ventilating patients. So why do we still manually ventilate patients with an adult BVM which is about 1.9L?  Manually ventilating adults with a pediatric BVM, which is about 1L, still exceeds the upper limit we want to administer. However, it does provide safer and more consistent lung-protective ventilation volumes.

Studies 

One study was done out of Capital Health Hopewell Medical Center, NJ, by Dafilou et al. This study enrolled 130 healthcare practitioners, including but not limited to 4 respiratory therapists,13 medical doctors, and 11 critical care technicians, and used the QuickLung RespiTrainor Advance set in the adult setting using both the adult BVM and the pediatric BVM. Results showed the mean Vt provided using the adult BVM was 807.7mL, and the pediatric BVM provided a mean Vt of 630.7mL.  

Another study by Siegler et al., which I will mention, was done with 50 enrolled EMT paramedics.  The research was done by performing one-handed squeezing of the adult and pediatric BVMs with the goal of chest rise.  They manually ventilated at one breath every 5 seconds. The study concluded that the pediatric BVM had a lower median Vt.  

Next time we as clinicians bring out the BVM for manual ventilation, stop and think about it.  Think about matching manual ventilation with the 6mL/kg set and delivered with mechanical ventilation. Think about using the pediatric BVM for safe and more consistent ventilation. 

The Debrief

  • Lung protective ventilation reduces morbidity and mortality.
  • Pediatric BVM provides safer and more consistent lung-protective ventilation volumes. 
  • Studies show that manually ventilating an adult patient with a pediatric BVM is possible 
  • Read more HERE on the basics of manually ventilating a patient. 

References

  1. Dafilou B, Schweitzer D, Ruhl N, Marques-Baptist’s A. It’s In The Bag: Tidal Volumes in Adult and Pediatric  Bag Valve Masks. West J Emerg. 2020 Apr 27;22 (3):722-726. doi: 10.5811/westjem.2020.3.45788.PMID:32421525; PMCID: PMC7234703.
  2. Siegler J, Kroll M, Wojcik S, Moy HP. Can EMS Providers Provide Appropriate Tidal Volumes in a Simulated Adult-sized Patient with a Pediatric-sized Bag-Valve-Mask? Prehosp Emerg Care. 2017 Jan-Feb;21(1):74-78. doi: 10.1080/10903127.2016.1227003. EPub 2016 Oct 3. PMID: 27690714.

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