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Arch Dis Child Fetal Neonatal Ed. 2019 May 23. pii: fetalneonatal-2018-316773. doi: 10.1136/archdischild-2018-316773. [Epub ahead of print]

Physiological effects of high-flow nasal cannula therapy in preterm infants.

Author information

1
Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK.
2
Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK.
3
Newcastle Neonatal Service, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK.
4
Newcastle University, Newcastle upon Tyne, UK.
#
Contributed equally

Abstract

OBJECTIVE:

High-flow nasal cannula (HFNC) therapy is increasingly used in preterm infants despite a paucity of physiological studies. We aimed to investigate the effects of HFNC on respiratory physiology.

STUDY DESIGN:

A prospective randomised crossover study was performed enrolling clinically stable preterm infants receiving either HFNC or nasal continuous positive airway pressure (nCPAP). Infants in three current weight groups were studied: <1000 g, 1000-1500 g and >1500 g. Infants were randomised to either first receive HFNC flows 8-2 L/min and then nCPAP 6 cm H2O or nCPAP first and then HFNC flows 8-2 L/min. Nasopharyngeal end-expiratory airway pressure (pEEP), tidal volume, dead space washout by nasopharyngeal end-expiratory CO2 (pEECO2), oxygen saturation and vital signs were measured.

RESULTS:

A total of 44 preterm infants, birth weights 500-1900 g, were studied. Increasing flows from 2 to 8 L/min significantly increased pEEP (mean 2.3-6.1 cm H2O) and reduced pEECO2 (mean 2.3%-0.9%). Tidal volume and transcutaneous CO2 were unchanged. Significant differences were seen between pEEP generated in open and closed mouth states across all HFNC flows (difference 0.6-2.3 cm H2O). Infants weighing <1000 g received higher pEEP at the same HFNC flow than infants weighing >1000 g. Variability of pEEP generated at HFNC flows of 6-8 L/min was greater than nCPAP (2.4-13.5 vs 3.5-9.9 cm H2O).

CONCLUSIONS:

HFNC therapy produces clinically significant pEEP with large variability at higher flow rates. Highest pressures were observed in infants weighing <1000 g. Flow, weight and mouth position are all important determinants of pressures generated. Reductions in pEECO2 support HFNC's role in dead space washout.

KEYWORDS:

high flow nasal cannula oxygen; neonatology; physiology; respiratory

Conflict of interest statement

Competing interests: ZL, ACF, SH, SG and CJO’B: none. MB: not related to this work: investigator-led research grants from Pfizer and Roche Diagnostics; speaker fees paid to Newcastle University from Novartis, Roche Diagnostics and TEVA. Travel expenses to educational meeting Boehringer Ingelheim and Vertex Pharmaceuticals.

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