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

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.

SUBMITTER: Liew Z

PROVIDER: S-EPMC6951230 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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

Liew Zheyi Z Fenton Alan C AC Harigopal Sundeep S Gopalakaje Saikiran S Brodlie Malcolm M O'Brien Christopher J CJ

Archives of disease in childhood. Fetal and neonatal edition 20190523 1

<h4>Objective</h4>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.<h4>Study design</h4>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. Infant ...[more]

PMID: 31123057

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Project description:BACKGROUND:Despite the extensive use of high-flow nasal cannula (HFNC) therapy in intensive care units (ICU) for acute respiratory failure (ARF), its daily clinical practice has not been assessed. We designed a regional survey in ICUs in North-west France to evaluate ICU physicians' clinical practice with HFNC. MATERIALS AND METHODS:We sent an observational survey to ICU physicians from 34 French ICUs over a 6-month period in 2016-2017. The survey included questions regarding the indications and expected efficiency of HFNC, practical aspects of use (initiation, weaning) and satisfaction. Comparisons between junior and senior ICU physicians were performed using a Fischer exact test. RESULTS:Among the 235 ICU physicians contacted, 137 responded (58.3%) all of whom regularly used HFNC. Hypoxemic ARF was considered a good indication for HFNC by all 137, but only 30% expected HFNC success (i.e., avoiding intubation in at least 60% of cases). Among hypoxemic indications, 30% of juniors considered acute pulmonary edema a good indication versus 74% of seniors (p?<?0.0001). Hypercapnic ARF was considered a good indication by 33% with only 2% expecting HFNC success. A need for conventional oxygen therapy???6 L/min justified HFNC therapy for 40% and???9 L/min for 39% of responders. 58% of ICU physicians started HFNC therapy with a FiO2???50% and 28% with a gas flow???50 L/min. Practices for HFNC weaning were heterogeneous: 48% considered a FiO2???30%; whereas, 30% considered a FiO2???30% with a high flow???20 L/min. Criteria for HFNC failure (i.e., need for intubation) were ventilatory pauses or arrest (97%), persistent hypoxemia (95%), respiratory acidosis (81%), worsening of breathing (95%, 100% of seniors and 86% of juniors, p?=?0.003), bronchial congestion (75%) and circulatory failure (61%, 72% of seniors and 44% of juniors, p?=?0.007). CONCLUSION:HFNC is used by ICU physicians in many situations of ARF, despite their relatively low expectations of success, especially in cases of hypercapnia. Clinical practices appear somewhat heterogeneous. Despite the physiological benefit of HFNC, further prospective observational studies are still required on HFNC outcomes and daily practices.

Project description:BackgroundNasal High Flow (NHF) therapy delivers flows of heated humidified gases up to 60 LPM (litres per minute) via a nasal cannula. Particles of oral/nasal fluid released by patients undergoing NHF therapy may pose a cross-infection risk, which is a potential concern for treating COVID-19 patients.MethodsLiquid particles within the exhaled breath of healthy participants were measured with two protocols: (1) high speed camera imaging and counting exhaled particles under high magnification (6 participants) and (2) measuring the deposition of a chemical marker (riboflavin-5-monophosphate) at a distance of 100 and 500 mm on filter papers through which air was drawn (10 participants). The filter papers were assayed with HPLC. Breathing conditions tested included quiet (resting) breathing and vigorous breathing (which here means nasal snorting, voluntary coughing and voluntary sneezing). Unsupported (natural) breathing and NHF at 30 and 60 LPM were compared.ResultsImaging: During quiet breathing, no particles were recorded with unsupported breathing or 30 LPM NHF (detection limit for single particles 33 μm). Particles were detected from 2 of 6 participants at 60 LPM quiet breathing at approximately 10% of the rate caused by unsupported vigorous breathing. Unsupported vigorous breathing released the greatest numbers of particles. Vigorous breathing with NHF at 60 LPM, released half the number of particles compared to vigorous breathing without NHF.Chemical marker tests: No oral/nasal fluid was detected in quiet breathing without NHF (detection limit 0.28 μL/m3). In quiet breathing with NHF at 60 LPM, small quantities were detected in 4 out of 29 quiet breathing tests, not exceeding 17 μL/m3. Vigorous breathing released 200-1000 times more fluid than the quiet breathing with NHF. The quantities detected in vigorous breathing were similar whether using NHF or not.ConclusionDuring quiet breathing, 60 LPM NHF therapy may cause oral/nasal fluid to be released as particles, at levels of tens of μL per cubic metre of air. Vigorous breathing (snort, cough or sneeze) releases 200 to 1000 times more oral/nasal fluid than quiet breathing (p < 0.001 with both imaging and chemical marker methods). During vigorous breathing, 60 LPM NHF therapy caused no statistically significant difference in the quantity of oral/nasal fluid released compared to unsupported breathing. NHF use does not increase the risk of dispersing infectious aerosols above the risk of unsupported vigorous breathing. Standard infection prevention and control measures should apply when dealing with a patient who has an acute respiratory infection, independent of which, if any, respiratory support is being used.Clinical trial registrationACTRN12614000924651.

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

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

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