Positioning and Flow Effects on Lung Volume in Asymmetric High-Flow Nasal Cannula.
Gabriel Appendino, María C Gomez, Gabriel A Musso et al.
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In 30 seconds
This prospective randomized crossover physiological study examined how body position, flow, and mouth condition affect end-expiratory lung impedance (EELI), a surrogate for end-expiratory lung volume, during asymmetric high-flow nasal cannula therapy in 16 healthy volunteers. EELI was assessed using electrical impedance tomography across four positions, two flow settings, and open- or closed-mouth breathing. The greatest global EELI increase occurred in reverse Trendelenburg at 60 L/min with the mouth closed (difference = 2.07, P < .001); mouth closure was an important contributor. This combination also enhanced dorsal-region EELI and promoted more homogeneous ventilation.
Key findings
- The largest global EELI increase was in reverse Trendelenburg at 60 L/min with the mouth closed (difference = 2.07, P < .001).
- Mouth closure was a critical factor in increasing EELI during asymmetric HFNC.
- Reverse Trendelenburg enhanced dorsal lung-region EELI at high flow with the mouth closed.
Why it matters
The findings show that posture and breathing route can influence the physiological response to asymmetric HFNC, not just the selected flow. Because EELI is a surrogate for lung volume and the study involved healthy volunteers, the results clarify physiological effects but do not establish improved clinical outcomes in patients.
What to keep in mind
The study included only 16 healthy volunteers and assessed EELI, a surrogate for lung volume, rather than clinical outcomes.