Comparison of Effort of Breathing for Infants on Nasal Modes of Respiratory Support

Abstract

Objective: To directly compare effort of breathing between high flow nasal cannula (HFNC), nasal intermittent mechanical ventilation (NIMV), and nasal continuous positive airway pressure (NCPAP).

Study design: This was a single center prospective cross-over study for patients <6 months in the cardiothoracic or pediatric intensive care unit receiving nasal noninvasive respiratory support after extubation. We measured effort of breathing using esophageal manometry with pressure-rate product (PRP) on all 3 modes. NIMV synchrony was determined by comparing patient efforts (esophageal manometry) with mechanically delivered breaths (spirometry in ventilator circuit). On NIMV, PRP and synchrony was also measured after adding a nasal clip on 26 patients.

Results: Forty-two children were included. Median (IQR) age was 2 (0.5, 4) months. There was no difference in median PRP between HFNC 6 liters per minute, 355 (270,550), NIMV 12/5 cm H₂O, 341 (235, 472), and NCPAP 5 cm H₂O, 340 (245,506) (P?=?.33). Results were similar regardless of HFNC flow rate or NIMV inspiratory pressure. Median PRP on CPAP of 5 cm H₂O prior to extubation 255 (176, 375) was significantly lower than all postextubation values (P?<?.002). On NIMV, less than 50% of patient efforts resulted in a ventilator breath, which was not improved with a nasal clip (P?>?.07)). However, as NIMV synchrony improved (>60%), PRP on NIMV was lower than on HFNC.

Conclusions: For infants, effort of breathing is similar on HFNC, NIMV, and NCPAP after extubation, regardless of flow rate or inspiratory pressure. We speculate that bi-level NIMV may be superior if high levels of synchrony can be achieved.

Keywords: humidified high flow nasal cannula; nasal continuous positive airway pressure; nasal intermittent mechanical ventilation.

Figure 1

Sequence of interventions. Patients received the following order of flow titrations. HFNC flow and inspiratory positive airway pressure (IPAP) changes were made after steady state was achieved and at least 2 minutes of recordings were obtained.

Figure 2

CONSORT diagrammatic representation of screening, enrollment, and cross-over.

Figure 3

Effort of breathing by support. The primary analysis demonstrated effort of breathing before extubation on CPAP was lower than all other conditions (P = .002). However, there is no difference in effort of breathing between HFNC and NIMV, regardless of flow rate or inspiratory pressure (Kruskal-Wallis ANOVA P = .15). CPAP values highlighted with dotted box.

Figure 4

There is no statistically significant difference in change in esophageal pressure, regardless of the mode of noninvasive support (P = .11). Max, maximum; Min, minimum.

Figure 5

Respiratory rate as a function of NRS. Data presented as median (bar), IQR (box), and range (whiskers). There is a trend for difference in median respiratory rate for all conditions (Kruskal-Wallis ANOVA P = .14), although this was not statistically significant, with the lowest respiratory rate seen on NIMV 12.

Figure 6

Effect of Neoseal nasal clip on synchrony, stratified by level of NIMV support. Data presented as median (bar), IQR (box), and range (whiskers), with Neoseal indicated by the shaded box. The Neoseal nasal clip altered synchrony from a median of 50%-55% (NIMV 12, P 07; NIMV 8, P = .35; NIMV 16, P = .40).

Figure 7

Effect of Neoseal on effort of breathing. There was no difference in median effort of breathing regardless of level of NIMV support with the addition of the nasal clip (NIMV 12, P = .49; NIMV 8, P = .9; NIMV 16, P = .71). Shaded area corresponds with NIMV with Neoseal.

Figure 8

Scatterplot and linear regression line assessing the relationship between the percentage of synchronous breaths on NIMV (x-axis) and the ratio of PRP on NIMV/HFNC. Patients who achieved more synchrony had a larger reduction in effort of breathing on NIMV compared with HFNC (NIMV 12 vs HFNC 6 and NIMV 12 with NeoSeal vs HFNC 6). (R = −0.28, P = .022, r² = 0.0778). PRP ratios less than 1 demonstrate decreased effort of breathing on NIMV than HFNC. The regression line crosses 1 when the percentage synchrony exceeds 60%, suggesting NIMV results in lower effort of breathing than HFNC when synchrony exceeds 60% (vertical line).