The Rule of 2’s

the rule of 2's by haney mallemat
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Non-invasive ventilation is a commonly used respiratory therapy in the Emergency Department and Intensive Care Unit. Despite its wide-spread use there is often some confusion about which therapy to start and how to titrate.

 This lecture will help clarify these issues and introduce a simple approach to patients with respiratory failure, called the “Rule of 2’s”  Watch the video and then look at the infographic and high-yield summary (here) by Dr. Shyam Murali.

Lecture Notes for Respiratory Failure Made Ridiculously Simple

Shyam Murali, @smuramed

Case: A 60y/o female comes into the emergency department in respiratory distress. She is placed on BPAP and diagnosed with a COPD exacerbation. The patient is then admitted to the intensive care unit for further treatment. On arrival to the ICU, she continues to have worsening respiratory distress and hypoxia. Her BPAP settings start at 10/5 and are subsequently increased to 15/10, 20/15, and 25/20. She subsequently becomes bradycardic, hypoxemic, and has a cardiac arrest.


We’re going to learn an algorithmic approach to respiratory failure of any source. Remember the “Rule of 2’s!”


2 types of respiratory failure

   >Type 1:  Failure to oxygenate – Hypoxemic

       *Increase FiO2

       *Increase mean airway pressure

   >Type 2: Failure to ventilate – Hypercarbic

       *Increase tidal volume

       *Increase respiratory rate

   >Some patients can have a mix of both types


2 types of Noninvasive Positive Pressure Ventilation

   >CPAP – Use for Type 1 Respiratory Failure

       *Ex. In acute decompensated heart failure, CPAP


          -Reduce preload

          -Recruit and splint lung tissue

          -Decrease work of breathing

          -Increase functional reserve capacity (FRC)


*2 ways to apply it

          -High Flow Nasal Cannula (HFNC)

              >Check out this video for a more in-depth

analysis of HFNC


              >Higher flow rates

              >Can provide some mild PEEP (1-8cmH2O)

              >Dead space washout


              >Various types of masks (mouth/nose, face,



          -Start: 5cmH2O

          -Titrate 3-5

          -Max 20cmH2O (lower esophageal sphincter has

intrinsic tone of 23-25 cmH2O)

   >BPAP – Use for Type 2 Respiratory Failure

       *AKA BiPAP, BiLevel

       *2 pressure levels

          -Inspiratory Positive Airway Pressure (IPAP) –

pressure provided by machine during inspiration

          -Expiratory Positive Airway Pressure (EPAP) –

pressure provided by machine during expiration

          -Difference between the two is the Pressure

Support, which contributes to the tidal volume

       *Starting Settings

          -IPAP: 5-20cmH2O

          -EPAP: 3-5cmH2O

       *Be aware of dynamic hyperinflation that can

cause decreased venous return and
obstructive shock leading to cardiac arrest. If this

happens, remove the patient from the ventilator

and press on the chest to release any trapped air.

This will improve venous return and subsequent

increase in cardiac output.

   >Tips for using CPAP/BPAP mask on patients

       *Allow patients to self-apply the mask. Have the

patient hold the mask to their face and 

       *Start low and titrate slow

   >Contraindications for NIPPV

       *Altered mental status



       *Upper airway obstruction

   >Skip NIPPV in patients who have significant

hemodynamic instability, significant illness, or ARDS

   >Place a limit on when to bail out from NIPPV to


   >Consider early intubation in a controlled setting

rather than crash airways


Case Conclusion: CPR was initiated while ACLS meds were obtained from the code cart. The patient was removed from the ventilator and connected to a BVM. As her chest was compressed, the dynamic hyperinflation was relieved, causing return of blood flow back to her heart. She started spontaneously breathing again and a pulse was confirmed!



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