Work of breathing indices in infants with respiratory insufficiency receiving high-flow nasal cannula and nasal continuous positive airway pressure

OBJECTIVE: To compare work of breathing (WOB) indices between two nCPAP settings and two levels of HFNC in a crossover study. STUDY DESIGN: Infants with a CGA 28-40 weeks, baseline of HFNC 3-5 lpm or nCPAP 5-6 cmH(2)O and fraction of inspired oxygen <= 40% were eligible. WOB was analyzed using respiratory inductive plethysmography (RIP) for each of the four modalities: HFNC 3 and 5 lpm, nCPAP 5 and 6 cmH(2)O. N = 20; Study weight 1516 g (+/- 40 g). RESULT: Approximately 12 000 breaths were analyzed indicating a high degree of asynchronous breathing and elevated WOB indices at all four levels of support. Phase angle values (means) (P<0.01): HFNC 3 lpm (114.7 degrees), HFNC 5 lpm (96.7 degrees), nCPAP 5 cmH(2)O (87.2 degrees), nCPAP 6 cmH(2)O (80.5 degrees). The mean phase relation of total breath (PhRTB) (means) (P<0.01): HFNC 3 lpm (63.2%), HFNC 5 lpm (55.3%), nCPAP 5 cmH(2)O (49.3%), nCPAP 6 cmH(2)O (48.0%). The relative labored breathing index (LBI) (means) (P <= 0.001): HFNC 3 lpm (1.39), HFNC 5 lpm (1.31), nCPAP 5 cmH(2)O (1.29), nCPAP 6 cmH(2)O (1.26). Eighty-two percent of the study subjects-respiratory mode combinations displayed clustering, in which a proportion of breaths either occurred predominantly out-of-phase (relative asynchrony) or in-phase (relative synchrony). CONCLUSION: In this study, WOB indices were statistically different, yet clinically similar in that they were elevated with respect to normal values. These infants with mild-to-moderate respiratory insufficiency demonstrate a meaningful elevation in WOB indices and continue to require non-invasive respiratory support. Patient variability exists with regard to biphasic clustered breathing patterns and the level of supplemental fraction of inspired oxygen <= 40% alone does not provide guidance to the optimal matching of WOB indices and non-invasive respiratory support.