Results

 

Patients receiving supplemental oxygen breathe dry oxygen for extended periods of time. The dry oxygen creates patient discomfort. The discomfort becomes an added stressor to intensive care patients and may be associated with a decreased quality of life and unpleasant memories. The dry oxygen may also increase patient airway resistance resulting in difficulty breathing [1].  We hypothesized that shutting off oxygen during the expiratory phase would help improve patient comfort during supplemental oxygen delivery.

 

Ten healthy volunteers were asked to wear a nasal cannula (Softech Bi-Flo, Teleflex, Research Triangle Park, NC) and were given a laptop to take an online survey during the study.  The system was attached to the cannula and delivered oxygen to the volunteer at various flow rates using both constant and intermittent mode.  After breathing under each condition, each volunteer was asked to rate their comfort level using a 100 point visual analog scale where 0 meant no discomfort and 100 meant painful.  The scores for both modes were compared for all flows using a two-sided t-test.  Differences were significant for p < 0.05.

 

The plot shows the average results across all settings and modes for the 10 volunteers.  The average perceived comfort was similar at 2 and 4 liter per minute settings.  For flows of 6 liters per minute and above, the intermittent method was more comfortable with the differences being statistically significant.

 

At lower flow rates, there is no difference in perceived comfort.  When constant flow is used, the perceived discomfort increases as flow increases.  When oxygen is delivered intermittently, the average perceived discomfort is the same regardless of the flow rate.  Using intermittent delivery for delivery oxygen allows for using greater oxygen flow rates.  The capability to use higher oxygen flows may be beneficial for pre-oxygenating patients.  Further testing should be conducted to increase statistical strength and may lead to a statistical difference at lower flows.

 

References:

 

[1]  G Chanques, J Constantin, M Sauter, B Jung, M Sebbane, D Verzilli, J Lefrant, S Jaber, "Discomfort associated with underhumidified high-flow oxygen therapy in critically ill patients," Intensive Care Med, 35(6):996-1003, 2009.