Fig. 3
From: Physiological effects of high-flow oxygen in tracheostomized patients
Thirty-second recordings of tracheal pressure tracings during HFOTTRACHEAL and HFOTNASAL in 5 patients who underwent tracheostomy decannulation over the course of ICU stay. In both conditions gas flow was set at 50 L/min. Average respiratory rate for the 30-s recording is reported for all conditions. During HFOTNASAL lower airway pressure during expiration is higher and more inter-individually variable than HFOTTRACHEAL, despite a non-dissimilar respiratory rate, which was calculated on the same 30-s recording. This suggests that the HFOTNASAL-induced increase in expiratory pressure depends not only on gas flow, but also on patient’s expiratory pattern and, likely, on individual respiratory system mechanical properties. Please note that, under this condition, tracheal pressure was not constant over the course of the respiratory cycle and became negative during inspiration in 4 patients, which is different from what previously reported for pharyngeal pressure [14]