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

Abstract

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.

Conflict of interest statement

CONFLICT OF INTEREST

The authors declare no conflict of interest.

Figures

Figure 1

Example patient no. 1: histogram and scatter representation of the phase angles for one of the patients studied on nasal CPAP 6 cmH2O.

Figure 2

Example patient no. 2: histogram and scatter representation of the phase angles for one of the patients studied on nasal CPAP 6 cmH2O.

Figure 3

Mean phase angle and 95% confidence interval results for all analyzed breaths in each group studied. Note: lower phase angle value indicates greater chest–abdomen synchrony.

Figure 4

Mean labored breathing index and 95% confidence interval results for all analyzed breaths in each group studied. Note: labored breathing index: closer to 1 relates to greater chest–abdomen synchrony.

Figure 5

Mean phase relation total breath and 95% confidence interval results for all analyzed breaths in each group studied. Note: phase relation of total breath: lower numbers relate to greater chest–abdomen synchrony.