BIPAP Principles:This one goes out to our rising Resus Residents: Bipap has settings that can ameliorate the two primary causes of respiratory failure: oxygenation (CHF, pneumonia) and ventilation (COPD, etc).
Improve hypoxemia two ways: 1. FiO2 2. PEEP (recruit more alveoli) Improve ventilation (hypercarbia) 1. Tidal Volume 2. Respiratory Rate
Settings on Bipap: IPAP – Inspiratory positive airway pressure (e.g. the high number) EPAP – Expiratory positive airway pressure (e.g. the low number) FiO2 – Fraction of inspired O2 (%) There are more, mentioned below, however lets touch on these first.
It is important to understand the cause of your respiratory failure to apply the proper settings. Physiology! Time to move on to practical application:
For HYPOXEMIA generally start with IPAP of 10cmH2O. EPAP can generally start at 5cmH2O
Example:
• CHF (hypoxemia): Start at IPAP of 10cmH2O with an EPAP of 5cmH20 (remember you want EPAP here to prevent atelectasis. o Pressure will improve oxygenation o May always increase FiO2 as well to improve oxygenation Conversely, for HYPERCARBIA (COPD) start with a similar IPAP of 5-10cmH20 however EPAP may not even be necessary. o Remember the difference in IPAP and EPAP is related to tidal volume, and this is one thing that effects hypercarbia!! Greater the difference = greater tidal volume. o You may also change the respiratory rate (described below)
Other settings/points: • Respiratory rate as well as I:E (inspiratory:expiratory) ratio can also be adjusted (however these settings may or may not be as helpful in a patient who is breathing on their own). I don’t want to get into this too much, but a couple points: • For HYPERCARBIA increased ventilation is desired with a HIGHER respiratory rate to blow off CO2. • For asthma keep EPAP lower (blow out more air in expiration) and setup a lower I:E ratio (e.g. 1:5) to prevent “breath stacking.” • Titrate by 2 – 3 cmH20 every 5 – 10 minutes. • Max IPAP is generally considered 20cmH2O (this is because lower esophageal sphincter tone is roughly 23 – 25cmH20, don’t over insufflate the stomach). • Remember to get a blood gas.
Sources: JB Life in the Fast Lane Rebel EM UpToDate