Placing a mask on COVID-19 patients during high-flow nasal cannula therapy reduces aerosol particle dispersion.
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ABSTRACT:
SUBMITTER: Li J
PROVIDER: S-EPMC7607969 | biostudies-literature | 2021 Jan
REPOSITORIES: biostudies-literature
Publications
Placing a mask on COVID-19 patients during high-flow nasal cannula therapy reduces aerosol particle dispersion.
Li Jie J Fink James B JB Elshafei Ahmad A AA Stewart Laurel M LM Barbian Hannah J HJ Mirza Sara H SH Al-Harthi Lena L Vines David D Ehrmann Stephan S
ERJ open research 20210125 1
<b>Wearing a surgical/procedure mask over high-flow nasal cannula (HFNC) reduces aerosol particle concentrations in the patients' vicinity. Wearing a mask over HFNC should be encouraged to reduce risks of aerosol transmission. #COVID19</b> https://bit.ly/2HLg5cE. ...[more]
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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.
| S-EPMC7880466 | biostudies-literature
Project description:BackgroundMolecular hydrogen (H2) is a biologically active gas that is widely used in the healthcare sector. In recent years, on-site H2 gas generators, which produce high-purity H2 by water electrolysis, have begun to be introduced in hospitals, clinics, beauty salons, and fitness clubs because of their ease of use. In general, these generators produce H2 at a low-flow rate, so physicians are concerned that an effective blood concentration of H2 may not be ensured when the gas is delivered through a nasal cannula. Therefore, this study aimed to evaluate blood concentrations of H2 delivered from an H2 gas generator via a nasal cannula.MethodsWe administered 100% H2, produced by an H2 gas generator, at a low-flow rate of 250 mL/min via a nasal cannula to three spontaneously breathing micro miniature pigs. An oxygen mask was placed over the nasal cannula to administer oxygen while minimizing H2 leakage, and a catheter was inserted into the carotid artery to monitor the arterial blood H2 concentration.ResultsDuring the first hour of H2 inhalation, the mean (standard error (SE)) H2 concentrations and saturations in the arterial blood of the three pigs were 1,560 (413) nL/mL and 8.85% (2.34%); 1,190 (102) nL/mL and 6.74% (0.58%); and 1,740 (181) nL/mL and 9.88% (1.03%), respectively. These values are comparable to the concentration one would expect if 100% of the H2 released from the H2 gas generator is taken up by the body.ConclusionsInhalation of 100% H2 produced by an H2 gas generator, even at low-flow rates, can increase blood H2 concentrations to levels that previous non-clinical and clinical studies demonstrated to be therapeutically effective. The combination of a nasal cannula and an oxygen mask is a convenient way to reduce H2 leakage while maintaining oxygenation.
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Project description:High-flow nasal cannula (HFNC) oxygen therapy comprises an air/oxygen blender, an active humidifier, a single heated circuit, and a nasal cannula. It delivers adequately heated and humidified medical gas at up to 60 L/min of flow and is considered to have a number of physiological effects: reduction of anatomical dead space, PEEP effect, constant fraction of inspired oxygen, and good humidification. While there have been no big randomized clinical trials, it has been gaining attention as an innovative respiratory support for critically ill patients. Most of the available data has been published in the neonatal field. Evidence with critically ill adults are poor; however, physicians apply it to a variety of patients with diverse underlying diseases: hypoxemic respiratory failure, acute exacerbation of chronic obstructive pulmonary disease, post-extubation, pre-intubation oxygenation, sleep apnea, acute heart failure, patients with do-not-intubate order, and so on. Many published reports suggest that HFNC decreases breathing frequency and work of breathing and reduces needs of escalation of respiratory support in patients with diverse underlying diseases. Some important issues remain to be resolved, such as its indication, timing of starting and stopping HFNC, and escalating treatment. Despite these issues, HFNC oxygen therapy is an innovative and effective modality for the early treatment of adults with respiratory failure with diverse underlying diseases.
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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.
| S-EPMC6726730 | biostudies-literature
Project description:ObjectiveHigh-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 designA 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.ResultsA 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).ConclusionsHFNC 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.
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