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 cmh2o 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 cmh2o. 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°), hfnc 5 lpm (96.7°), ncpap 5 cmh2o (87.2°), ncpap 6 cmh2o (80.5°). the mean phase relation of total breath (phrtb) (means) (p<0.01): hfnc 3 lpm (63.2%), hfnc 5 lpm (55.3%), ncpap 5 cmh2o (49.3%), ncpap 6 cmh2o (48.0%). the relative labored breathing index (lbi) (means) (p⩽0.001): hfnc 3 lpm (1.39), hfnc 5 lpm (1.31), ncpap 5 cmh2o (1.29), ncpap 6 cmh2o (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.