The effect of high-flow nasal cannula on diaphragm dysfunction including paradoxical diaphragmatic contraction in the intensive care unit.

Background : Diaphragm dysfunction is a serious problem. However, a few management techniques exist for diaphragm dysfunction. Methods : Adult patients treated with high-flow nasal cannula (HFNC) in the intensive care unit were included in this study. The diaphragm function was evaluated using ultrasound measurement of thickening fraction before and after HFNC liberation. Normal diaphragm contraction was defined as thickening fraction ≥ 15% without HFNC, whereas decreased or paradoxical diaphragm contractions were 0%-15% or < 0%, respectively. Results : Forty patients were enrolled, and 16 (40%) had normal diaphragm contraction, whereas 19 (48%) or 5 (13%) had decreased or paradoxical diaphragm contractions, respectively. Thickening fraction increased after HFNC liberation (27.0% ± 25.7% vs. 38.8% ± 34.5%,  p = 0.03 in HFNC vs. no HFNC) in patients without diaphragm dysfunction. In patients with decreased diaphragm contraction, thickening fraction did not change with or without HFNC (8.9% ± 11.7% vs. 6.7% ± 5.2%,  p = 0.35), whereas paradoxical contraction decreased with HFNC (1.0% ± 10.2% vs. -10.3% ± 2.7%,  p = 0.04) in patients with paradoxical diaphragm contraction. Conclusions : The work of breathing decreased with HFNC in patients without diaphragm dysfunction, but did not decrease in patients with decreased diaphragm contraction. Paradoxical diaphragm contraction decreased with HFNC. J. Med. Invest. 68 : 159-164, February, 2021.