Ambu-Bags in Veterinary CPR
The humble manual resuscitator bag, often known as a Ambu-Bag or BVM. Cited often as a resource in CPR but often underutilised.
In this blog post we will consider how to use the manual resuscitator bag, when it might be used and the set up of the bag including size selection.
Bags will often arrive collapsed or semi collapsed and you will need to fully expand them prior to use. Remove the human facemask if they arrive this and keep that to one side for pre-oxygenating the flatter faced patients. Your bag should have oxygen tubing, an oxygen reservoir bag and the main bag itself.
Valved bags are preferred as they will have a pressure release valve which prevents the operator from over compressing the bag, making them perfect for IPPV during a crash when personal may be varied in experience and skill. The valve should be a maximum pressure of 40cm of H2O as this is the maximum pressure recommended for IPPV during CPR within the RECOVER Guidelines. There are bags on the market with no valve or valves that are above the maximum recommendation.
Selecting the manual resuscitator bag size
The manual resuscitator bag will come in a range of sizes and as a guide the body of the bag should be sized as 15mls per kg of the patient. For example, a small adult with a bag volume of a 1000ml will accommodate a patient up to 65kg approximately. Practices that see a range of patients may want to have a couple of bags ranging in size.
Manual resuscitator can be attached onto both an Endotracheal Tube (ET) and a mask. During CPR the preferred method of ventilation is with a safely cuffed ET Tube but there are recommendations for single rescuer CPR that suggest mask to snout ventilation over mouth to nose. If you are using a mask, then the black diaphragm should be used. Practices that may see small furries may want to keep a small mask aside with a small manual resuscitator, this article describes incidents where mask to snout has been used successfully in rabbit CPR.
Using Oxygen with a manual resuscitator bag
The tubing of the manual resuscitator should be attached onto a flowmeter to provide oxygen, but they will also ventilate on room air. Although the RECOVER advise is that we should be placing them oxygen where possible. Key point is not to delay compressions in the pursuit of oxygen, rather just start where you are and move during a pulse check with minimal interruption to the compressions.
Storage can be tricky as they are quite bulky, avoid placing them at the back of cupboard or up high. Rather hang them on the wall so they are obvious and within easy access.
Manual resuscitator bags are a great addition to your crash set up and will provide an easy mode of ventilation during CPR.
Further information and reading:
Fletcher, D.J. et al. (2012) ‘Recover evidence and knowledge gap analysis on veterinary CPR. part 7: Clinical guidelines’, Journal of Veterinary Emergency and Critical Care, 22(s1). doi:10.1111/j.1476-4431.2012.00757.x.
Hopper, K. et al. (2012) ‘Recover evidence and knowledge gap analysis on veterinary CPR. part 3: Basic life support’, Journal of Veterinary Emergency and Critical Care, 22(s1). doi:10.1111/j.1476-4431.2012.00753.x.
Hopper, K. et al. (2024) ‘2024 recover guidelines: Basic life support. evidence and knowledge gap analysis with treatment recommendations for small animal CPR’, Journal of Veterinary Emergency and Critical Care, 34(S1), pp. 16–43. doi:10.1111/vec.13387.
Hopper, K. et al. (2018a) ‘Efficacy of manual ventilation techniques during cardiopulmonary resuscitation in dogs’, Frontiers in Veterinary Science, 5. doi:10.3389/fvets.2018.00239