Q: What is one added advantage of High Flow Nasal Cannula Oxygen Therapy?


Answer:  It provides Positive Pressure Ventilation (PEEP effect)

Despite being an open system, high flow itself overcomes some of the resistance of expiratory flow and increases airway pressure. One added trick is to instruct patient to keep mouth closed which helps in increasing pharyngeal pressure, which in return not only increases lung volume but may also recruits collapsed alveoli. Interestingly, higher the BMI higher is the effect.



References: 

 1.  Parke R, McGunness S, Eccleston M. Nasal high-flow therapy delivers low level positive airway pressure. Br J Anaesth. 2009;103:886–90.

2. Groves N, Tobin A. High flow nasal oxygen generates positive airway pressure in adult volunteers. Aust Crit Care. 2007;20:126–31