Comparison of heated humidified high-flow nasal cannula flow rates (1-L·kg·min-1 vs 2-L·kg·min -1 ) in the management of acute bronchiolitis

Impact of initial high flow nasal cannula flow rates on clinical outcomes in children with bronchiolitis

PURPOSE

Our aim was to evaluate the impact of the initial high flow nasal cannula (HFNC) flow rate on clinical outcomes in children with bronchiolitis.

METHODS

This secondary analysis of retrospective data included children <2 years who required HFNC for bronchiolitis between 10/01/2018-04/20/2019, and following implementation of a revised institutional bronchiolitis pathway between 10/01/2021-04/30/2022. The new pathway recommended weight-based initiation of HFNC at 1.5-2 L/kg/min. We evaluated the effect of low (<1.0 L/kg/min), medium (1-1.5 L/kg/min) and high (>1.5 L/kg/min) HFNC flow rates on need for positive pressure ventilation (PPV), intensive care unit (ICU) transfer, HFNC treatment time, and hospital length of stay (LOS).

RESULTS

The majority of the 885 included children had low initial flow rates (low [n = 450, 50.8%], medium [n = 332, 37.5%] and high [n = 103, 11.7%]). There were no significant differences in PPV (high: 7.8% vs. medium: 9.3% vs. low: 8.2%, p = 0.8) or ICU transfers (high: 4.9% vs. medium: 6.0% vs. low: 3.8%, p = 0.3). The low flow group had a significantly longer median HFNC treatment time (High: 29 [18, 45] vs. medium: 29 [16, 50] vs. low: 39 [25, 63], p < .001) and hospital LOS (High: 41 [27, 59] vs. medium: 42 [29, 66] vs. low: 50 (39, 75), p < .001). Logistic and linear regression models did not demonstrate any associations between HFNC flow rates and PPV or hospital LOS.

CONCLUSIONS

Initial HFNC flow rates were not associated with significant changes in clinical outcomes in children in children with bronchiolitis.

Association of Fluid Overload with Escalation of Respiratory Support and Endotracheal Intubation in Acute Bronchiolitis Patients

Fluid overload has been associated with increased oxygen requirement, prolonged duration of mechanical ventilation, and longer length of hospital stay in children hospitalized with pulmonary diseases. Critically ill infants with bronchiolitis admitted to the pediatric intensive care unit (PICU) also tend to develop fluid overload and there is limited information of its role on noninvasive respiratory support. Thus, our primary objective was to study the association of fluid overload in patients with bronchiolitis admitted to the PICU with respiratory support escalation (RSE) and need for endotracheal intubation (ETI). Infants ≤24 months of age with bronchiolitis and admitted to the PICU between 9/2009 and 6/2015 were retrospectively studied. Demographic variables, clinical characteristics including type of respiratory support and need for ETI were evaluated. Fluid overload as assessed by net fluid intake and output (net fluid balance), cumulative fluid balance (CFB) (mL/kg), and percentage fluid overload (FO%), was compared between patients requiring and not requiring RSE and among patients requiring ETI and not requiring ETI at 0 (PICU admission), 12, 24, 36, 48, 72, 96, and 120 hours. One-hundred sixty four of 283 patients with bronchiolitis admitted to the PICU qualified for our study. Thirty-four of 164 (21%) patients required escalation of respiratory support within 5 days of PICU admission and of these 34 patients, 11 patients required ETI. Univariate analysis by Kruskal-Wallis test of fluid overload as assessed by net fluid balance, CFB, and FO% between 34 patients requiring and 130 patients not requiring RSE and among 11 patients requiring ETI and 153 patients not requiring ETI, at 0, 12, 24, 36, 48, 72, 96 and 120 hours did not reveal any significant difference ( p >0.05) at any time interval. Multivariable logistic regression analysis revealed higher PRISM score (odds ratio [OR]: 4.95, 95% confidence interval [95% CI]: 1.79-13.66; p  = 0.002), longer hours on high flow nasal cannula (OR: 4.86, 95% CI: 1.68-14.03; p  = 0.003) and longer hours on noninvasive ventilation (OR: 11.16, 95% CI: 3.36-36.98; p  < 0.001) were associated with RSE. Fluid overload as assessed by net fluid balance, CFB, and FO% was not associated with RSE or need for ETI in critically ill bronchiolitis patients admitted to the PICU. Further prospective studies involving larger number of patients with bronchiolitis are needed to corroborate our findings.

Association of enteral feeds in critically ill bronchiolitis patients supported by high-flow nasal cannula with adverse events and outcomes

To study association of enteral feeds in bronchiolitis patients supported by different levels of high flow nasal cannula (HFNC) with adverse events, nutritional goals, and clinical outcomes. Bronchiolitis patients ≤ 24 months of age treated with < 1 L/kg/min, 1-2 L/kg/min and > 2 L/kg/min of HFNC between January 2014 and December 2021 were studied retrospectively at a tertiary care children's hospital. Adverse events (aspiration pneumonia, emesis, and respiratory support escalation), nutritional goals (initiation of enteral feeds, achievement of nutritional goal volume and goal calories, percentage weight change during hospital stay) and clinical outcomes (HFNC duration, oxygen supplementation duration after HFNC, length of hospital stay following HFNC support, total length of hospital stay and follow-up for 1 month after hospital discharge) were compared between fed and non-fed patients on HFNC. Six hundred thirty-six (489 fed and 147 not-fed) bronchiolitis patients on HFNC studied. 260 patients, 317 patients and 59 patients were supported by < 1 L/kg/min, 1-2 L/kg/min and > 2 L/kg/min of HFNC, respectively. Enterally fed patients had significantly less adverse events (OR = 0.14, 95% CI 0.083 - 0.23, p < 0.001), significantly better nutritional goals: earlier initiation of enteral feeds by 65% in time (mean ratio = 0.35, 95% CI 0.28 - 0.43, p < 0.001), earlier achievement of goal volume and goal calorie needs by 14% in time (mean ratio = 0.86, 95% CI 0.78 to 0.96, p = 0.005) and significantly better clinical outcomes: shorter HFNC duration by 29.75 h (95% CI 20.19 -39.31, p < 0.001), shorter oxygen supplementation duration after HFNC by 12.14 h (95% CI 6.70 -17.59, p < 0.001), shorter length of hospital stay after HFNC support by 21.35 h (95% CI 14.71-27.98, p < 0.001) and shorter total length of hospital stay by 51.10 h (95% CI 38.65 -63.55, p < 0.001), as compared to non-fed patients, after adjusting for age, weight, prematurity, comorbidities, admission time, admission bronchiolitis score, admission respiratory rate, and HFNC levels. The number of revisits and readmissions at 7 and 30 days after hospital discharge were not significantly different (p > 0.05) between the fed and non-fed groups.    Conclusion: Enteral feeding of bronchiolitis patients supported by different levels of HFNC is associated with less adverse events and better nutrition goals and clinical outcomes. What is Known: •There is general apprehension to feed critically ill bronchiolitis patients supported by high flow nasal cannula. What is New: •Our study reveals that enteral feeding of critically ill bronchiolitis patients supported by different levels of high flow nasal cannula is associated with minimal adverse events, better nutritional goals and improved clinical outcomes as compared to non-fed patients.

High-Flow Oxygen and Other Noninvasive Respiratory Support Therapies in Bronchiolitis: Systematic Review and Network Meta-Analyses

OBJECTIVES

We present a systematic review on the effectiveness of noninvasive respiratory support techniques in bronchiolitis.

DATA SOURCES

Systematic review with pairwise meta-analyses of all studies and network meta-analyses of the clinical trials.

STUDY SELECTION

Patients below 24 months old with bronchiolitis who require noninvasive respiratory support were included in randomized controlled trials (RCTs), non-RCT, and cohort studies in which high-flow nasal cannula (HFNC) was compared with conventional low-flow oxygen therapy (LFOT) and/or noninvasive ventilation (NIV).

DATA EXTRACTION

Emergency wards and hospitalized patients with bronchiolitis.

DATA SYNTHESIS

A total of 3,367 patients were analyzed in 14 RCTs and 8,385 patients in 14 non-RCTs studies. Only in nonexperimental studies, HFNC is associated with a lower risk of invasive mechanical ventilation (MV) than NIV (odds ratio, 0.49; 95% CI, 0.42-0.58), with no differences in experimental studies. There were no differences between HFNC and NIV in other outcomes. HFNC is more effective than LFOT in reducing oxygen days and treatment failure. In the network meta-analyses of clinical trials, NIV was the most effective intervention to avoid invasive MV (surface under the cumulative ranking curve [SUCRA], 57.03%) and to reduce days under oxygen therapy (SUCRA, 79.42%), although crossover effect estimates between interventions showed no significant differences. The included studies show methodological heterogeneity, but it is only statistically significant for the reduction of days of oxygen therapy and length of hospital stay.

CONCLUSIONS

Experimental evidence does not suggest that high-flow oxygen therapy has advantages over LFOT as initial treatment nor over NIV as a rescue treatment.

Is implementation of a hospital pathway for high-flow nasal cannula initiation and weaning associated with reduced high-flow duration in bronchiolitis?

BACKGROUND

High-flow nasal cannula (HFNC) therapy is widely used for children with bronchiolitis, but its optimal role remains uncertain. Our institution created and later revised a clinical pathway guiding HFNC initiation and weaning.

METHODS

A retrospective review of 1690 bronchiolitis encounters was conducted. Trends in the duration of HFNC and hours spent weaning HFNC as proportions of the monthly hospital length of stay (LOS) for bronchiolitis, hospital LOS, and escalation of care were compared using interrupted time series (ITS) models across three study periods: Baseline (HFNC managed at provider discretion), Intervention 1 (pathway with initiation at 0.5 L/kg/min and escalation up to 2 L/kg/min), and Intervention 2 (revised pathway, initiation at the maximum rate of 2 L/kg/min). Both pathway iterations provided titration and weaning guidance. Maximum respiratory scores were used to adjust for case severity.

RESULTS

After adjustment for severity and time, both HFNC duration and HFNC weaning time (as a proportion of monthly LOS) decreased at the start of Intervention 1, but subsequently increased. During Intervention 2, both these measures trended downward, returning to baseline. Total LOS did not change in the baseline or intervention periods. Escalation of care did not differ from baseline to the end of Intervention 2.

CONCLUSION

Initiating HFNC at higher flow rates with weaning guidance for children hospitalized with bronchiolitis was associated with a reduction in HFNC duration without differences in LOS or escalation of care. These findings suggest that standardization through clinical pathways can limit HFNC duration in bronchiolitis.

The impact of an autonomous nurse-led high-flow nasal cannula oxygen protocol on clinical outcomes of infants with bronchiolitis

OBJECTIVE

To investigate the relationship of the implementation of a nurse-led high-flow nasal cannula oxygen protocol on the clinical outcomes of infants with bronchiolitis in a regional paediatric unit.

BACKGROUND

Bronchiolitis is a common lower respiratory illness and is the leading cause for hospitalisation of infants globally. Standard care involves the provision of supportive measures. Historically, supplemental oxygen was provided by low-flow nasal cannula. High-flow nasal cannula oxygen has been increasingly adopted despite limited evidence of its efficacy.

METHODS

This study employed non-equivalent, post-implementation only design to explore clinical outcomes of infants with bronchiolitis admitted for high-flow nasal cannula oxygen therapy. The study compared infants in the 24 months before and after the initiation of a high-flow nasal cannula protocol. The primary clinical outcome was length of stay, secondary outcomes included time on high flow, weaning time, escalation of care and time outside of physiological parameters. Implementation strategy evaluation was measured by compliance with applying the protocol, reported as episodes of variance, and duration of variance. The StaRI checklist was selected as the most appropriate reporting guideline.

RESULTS

A total of 80 patients were admitted with bronchiolitis and received high-flow nasal cannula oxygen therapy during a 48-month period; 37 patients were prior, and 43 after, the introduction of a nurse-led high-flow nasal cannula protocol. Length of stay was significantly reduced in the post-implementation group compared to the historical control group (83.8 vs. 61.3 h). Time on high flow and weaning time was decreased in the post-implementation group compared to the control group (33.5 vs. 26.7 h and 26 vs.12.25 h, respectively); however, these did not reach statistical significance. There was varied application of the HFNC protocol.

CONCLUSIONS

The implementation of a nurse-led high-flow nasal cannula protocol was associated with a reduced length of stay.

RELEVANCE TO CLINICAL PRACTICE

This study demonstrated that infants with bronchiolitis that were treated with a nurse-led high-flow nasal cannula (HFNC) therapy protocol had positive effects on clinical outcomes including a shorter length of stay than compared with those with physician-directed care in a regional paediatric unit. A weight-based (2 L/kg) HFNC therapy was safely administered to infants with bronchiolitis in a regional hospital paediatric ward with no paediatric intensive care unit (PICU).

Impact of initial flow rate of high-flow nasal cannula on clinical outcomes in infants with bronchiolitis

AIM

Bronchiolitis is a common condition in the paediatric population. Severe cases often receive respiratory support with high-flow nasal cannula (HFNC). Significant variation in the application of HFNC exists throughout Australia and internationally. This study aimed to determine if the flow rate used initially and when ceasing HFNC at the end of the illness alters clinical outcomes.

METHODS

A retrospective analysis was conducted of 251 children less than 12 months of age when admitted to the Women's and Children's Hospital Adelaide with bronchiolitis requiring HFNC therapy between the period of April 2016 to April 2019. The primary outcome was to determine if commencing HFNC therapy at different rates (1 L/kg/min, 1.5 L/kg/min and 2 L/kg/min) affected length of stay or treatment failure (escalation in physiological parameters or respiratory support).

RESULTS

Treatment failure occurred in 33%, 13% and 26% of those starting at 1 L/kg/min, 1.5 L/kg/min and 2 L/kg/min, respectively. Commencing HFNC therapy at 1 L/kg/min increased length of stay by an average of 30 h (P < 0.001) and the likelihood of treatment failure (P < 0.002) compared with starting at 1.5 L/kg/min. There was no statistical difference in outcomes between starting at 1.5 L/kg/min and 2 L/kg/min. There was no significant difference in the length of stay from the starting of weaning HFNC to time of discharge.

CONCLUSIONS

The commencing flow rates of initial HFNC therapy impact individual patient's outcomes, including length of stay and rates of treatment failure. Clinicians should consider commencing HFNC at 1.5 L/kg/min or 2 L/kg/min in infants that have failed low-flow oxygen therapy.

Analysis of risk factors for the failure of respiratory support with high-flow nasal cannula oxygen therapy in children with acute respiratory dysfunction: A case-control study

BACKGROUND

Evidence-based clinical practice guidelines regarding high-flow nasal cannula (HFNC) use for respiratory support in critically ill children are lacking. Therefore, we aimed to determine the risk factors for early HFNC failure to reduce the failure rate and prevent adverse consequences of HFNC failure in children with acute respiratory dysfunction.

METHODS

Demographic and laboratory data were compared among patients, admitted to the pediatric intensive care unit between January 2017 and December 2018, who were included in a retrospective cohort study. Univariate and multivariate analyses were performed to determine risk factors for eventual entry into the predictive model for early HFNC failure and to perform an external validation study in a prospective observational cohort study from January to February 2019. Further, the association of clinical indices and trends pre- and post-treatment with HFNC treatment success or failure in these patients was dynamically observed.

RESULTS

In total, 348 pediatric patients were included, of these 282 (81.0%) were included in the retrospective cohort study; HFNC success was observed in 182 patients (64.5%), HFNC 0-24 h failure in 74 patients (26.2%), and HFNC 24-48 h failure in 26 patients (9.2%). HFNC 24 h failure was significantly associated with the pediatric risk of mortality (PRISM) III score [odds ratio, 1.391; 95% confidence interval (CI): 1.249-1.550], arterial partial pressure of carbon dioxide-to-arterial partial pressure of oxygen (PaCO₂/PaO₂) ratio (odds ratio, 38.397; 95% CI: 6.410-230.013), and respiratory rate-oxygenation (ROX) index (odds ratio, 0.751; 95% CI: 0.616-0.915). The discriminating cutoff point for the new scoring system based on the three risk factors for HFNC 24 h failure was ≥ 2.0 points, with an area under the receiver operating characteristic curve of 0.794 (95% CI, 0.729-0.859, P < 0.001), sensitivity of 68%, and specificity of 79%; similar values were noted on applying the model to the prospective observational cohort comprising 66 patients (AUC = 0.717, 95% CI, 0.675-0.758, sensitivity 83%, specificity 44%, P = 0.009). In this prospective cohort, 11 patients with HFNC failure had an upward trend in PaCO₂/PaO₂ ratio and downward trends in respiratory failure index (P/F ratio) and ROX index; however, opposite directions of change were observed in 55 patients with HFNC success. Furthermore, the fractional changes (FCs) in PaCO₂/PaO₂ ratio, P/F ratio, percutaneous oxygen saturation-to-fraction of inspired oxygen (S/F) ratio, and ROX index at 2 h post-HFNC therapy onset were statistically significant between the two groups (all, P < 0.05).

CONCLUSION

In the pediatric patients with acute respiratory insufficiency, pre-treatment PRISM III score, PaCO₂/PaO₂ ratio, and ROX index were risk factors for HFNC 24 h failure, and the direction and magnitude of changes in the PaCO₂/PaO₂ ratio, P/F ratio, and ROX index before and 2 h after HFNC treatment were warning indicators for HFNC 24 h failure. Further close monitoring should be considered for patients with these conditions.

Velocity-based target flow rate for high-flow nasal cannula oxygen therapy

BACKGROUND

The aim of this study was to assess retrospectively whether the average inspiratory flow velocity-based initial flow rate in high-flow nasal cannula (HFNC) therapy could be well tolerated and safely used for infants and children hospitalized with moderate to severe respiratory failure.

METHODS

Thirty-three patients without underlying diseases (22 males; 67%), hospitalized to receive HFNC therapy for infection-related respiratory failure, were analyzed. The median age was 2 months (interquartile range, 1 month to 1 year). Patients with dyspnea and carbon dioxide partial pressure (pCO₂ ) >50 mmHg or venous blood pH <7.320, combined with pulse oximetry arterial oxygen saturation <92%, were included. We set target flow rates calculated from the average inspiratory flow velocity, starting at the actual initial flow rates, and these were subsequently adjusted if necessary.

RESULTS

One patient could not tolerate the cannula. Of the remaining 32 patients, 81% (n = 26) had an actual initial flow rate within 1 L of the target flow rate; these patients were evaluated for changes in the fraction of inspired oxygen (FITarget flow rate tableO₂ ), pH, and pCO₂ values after 24 h. Three patients required a higher fraction of inspired oxygen, one showed a persistent pH < 7.320, and seven exhibited pCO₂ >50 mmHg. No patient required non-invasive positive-pressure ventilation, and one required intubation. Pneumothorax was not reported in any patient.

CONCLUSIONS

The average inspiratory flow velocity-based initial flow rate was well-tolerated without sedation, and there were no severe complications. Starting at this flow rate would improve the use of HFNC therapy in the pediatric ward, possibly reducing the need for more invasive modes of ventilation.

Efficacy and safety of high flow nasal oxygen for children with bronchiolitis: systematic review and meta-analysis

BACKGROUND

To assess the published evidence to establish the efficacy and safety of high flow oxygen cannula (HFNC) as respiratory support for children up to 24 months of age with bronchiolitis within acute hospital settings.

METHODS

We searched eight databases up to March 2021. Studies including children up to 24 months of age with a diagnosis of bronchiolitis recruited to an randomised controlled trial were considered in the full meta-analysis. At least one arm of the study must include HFNC as respiratory support and report at least one of the outcomes of interest. Studies were identified and extracted by two reviewers. Data were analysed using Review Manager V.5.4.

RESULTS

From 2943 article titles, 308 full articles were screened for inclusion. 23 studies met the inclusion criteria, 15 were included in the metanalyses. Four studies reported on treatment failure rates when comparing HFNC to standard oxygen therapy (SOT). Data suggests HFNC is superior to SOT (OR 0.45, 95% CI 0.36 to 0.57). Four studies reported on treatment failure rates when comparing HFNC to continuous positive airways pressure (CPAP). No significant difference was found between CPAP and HFNC (OR 1.64, 95% CI 0.96 to 2.79; p=0.07). Four studies report on adverse outcomes when comparing HFNC to SOT. No significant difference was found between HFNC & SOT (OR 1.47, 95% CI 0.54 to 3.99).

CONCLUSION

HFNC is superior to SOT in terms of treatment failure and there is no significant difference between HFNC and CPAP in terms of treatment failure. The results suggest HFNC is safe to use in acute hospital settings.

[Paediatric Life Support]

The European Resuscitation Council (ERC) Paediatric Life Support (PLS) guidelines are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations of the International Liaison Committee on Resuscitation (ILCOR). This section provides guidelines on the management of critically ill or injured infants, children and adolescents before, during and after respiratory/cardiac arrest.

Capillary blood gas in infants with bronchiolitis: Can end-tidal capnography replace it?

OBJECTIVES

To explore the predictive ability of capillary blood gas (CBG) pCO₂ for respiratory decompensation in infants aged ≤6 months with bronchiolitis admitted from the emergency department; to determine whether end-tidal CO₂ (etCO₂) capnography can serve as a less invasive substitute for CBG pCO₂.

STUDY DESIGN

This was a prospective cohort study of previously healthy infants aged ≤6 months admitted for bronchiolitis from the emergency department (ED). Initial CBG pCO₂ and etCO₂ capnography were obtained in the ED prior to inpatient admission. Simple logistic regression modeling was used to examine the associations of CBG pCO₂ and etCO₂ capnography with respiratory decompensation. Pearson's correlation measured the relationship between CBG pCO₂ and etCO₂ capnography.

RESULTS

Of 134 patients, 61 had respiratory decompensation. There was a significant association between CBG pCO₂ and respiratory decompensation (OR = 1.07, p = 0.003), even after outlying values were excluded (OR = 1.06, p = 0.005). End tidal CO₂ capnography was not significantly associated with decompensation (OR = 1.02, p = 0.17), even after outlying values were excluded (OR = 1.02, p = 0.24). There was a moderate correlation between etCO₂ capnography and CBG pCO₂ (r = 0.39, p < 0.001).

CONCLUSION

In infants with bronchiolitis, CBG pCO₂ provides an objective measure for predicting respiratory decompensation, and a single etCO₂ measurement should not replace its use.

Assessment of Peak Inspiratory Flow in Young Infants with Acute Viral Bronchiolitis: Physiological Basis for Initial Flow Setting in Patients Supported with High-Flow Nasal Cannula

OBJECTIVE

To assess the inspiratory demand in young infants with acute viral bronchiolitis to provide a physiological basis for initial flow setting for patients supported with high flow nasal cannula.

STUDY DESIGN

Prospective study in 44 infants up to 6 months old with acute viral bronchiolitis, admitted to a pediatric intensive care unit from November 2017 to March 2019. Airflow measurements were performed using spirometry. The primary endpoint was the inspiratory demand as measured by peak tidal inspiratory flow (PTIF). The secondary endpoints were the relationships determined between PTIF, patient weight, and disease severity.

RESULTS

Median (Q₂₅-Q₇₅) age and weight of the patients were 37 (20-67) days and 4.3 (3.5-5.0) kg, respectively. Mean PTIF was 7.45 (95% CI 6.51-8.39, min-max: 2.40-16.00) L/minute. PTIF indexed to weight was 1.68 (95% CI 1.51-1.85, min-max: 0.67-3.00) L/kg/minute. PTIF was <2.5 L/kg/minute in 89% (95% CI 75-96) of infants. PTIF was correlated with weight (ρ= 0 .55, P < .001) but not with markers of disease severity, including modified Woods clinical asthma score, Silverman-Andersen score, respiratory rate, fraction of inspired oxygen, and PCO₂.

CONCLUSIONS

High flow nasal cannula therapy is used commonly to support infants with acute viral bronchiolitis. The efficiency of the device is optimal if the flow setting matches the patient's inspiratory demand. According to our results, a flow rate of <2.5 L/kg/minute would be appropriate in most situations.

European Resuscitation Council Guidelines 2021: Paediatric Life Support

These European Resuscitation Council Paediatric Life Support (PLS) guidelines, are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the management of critically ill infants and children, before, during and after cardiac arrest.

Impact of flow and temperature on non-dyspnoeic dogs' tolerance undergoing high-flow oxygen therapy

OBJECTIVES

To prospectively describe the impact of gas flow rate and temperature on dog's tolerance of high-flow nasal oxygen therapy during recovery from anaesthesia, hypothesizing that higher flow rates and temperatures will decrease tolerance.

MATERIALS AND METHODS

Twelve non-dyspnoeic client-owned dogs recovering from general anaesthesia were included in this study. After extubation, a nasal cannula was positioned and high-flow nasal oxygen therapy was initiated. Two flow rates (two or four time the theoretical minute ventilation: HF2 and HF4), each of them combined with two temperatures (31 and 37°C: T31 and T37), were randomly applied (four conditions per dog). For each condition, cardiovascular and respiratory parameters (heart rate, respiratory rate, systolic arterial blood pressure and pulse oximeter oxygen saturation), sedation score and tolerance score were recorded at initiation (T₀ ) and after 10 minutes of accommodation (T₁₀ ).

RESULTS

Sedation scores were not significantly different between the four conditions. Cardiovascular and respiratory parameters were not significantly different between any condition at both T₀ and T₁₀ . Tolerance scores were good and not significantly different between any flow rate or temperature (HF2-T31: 4 (2-4), HF4-T31: 4 (2-4), HF2-T37: 4 (2-4), HF4-T37: 4 (1-4)).

CLINICAL SIGNIFICANCE

The gas flow rates and temperatures studied have no impact on tolerance during the recovery period of non-dyspnoeic dogs, and high-flow nasal cannula is well tolerated. Further studies are required to confirm these results in dyspnoeic dogs.

Comparison of heated humidified high-flow nasal cannula flow rates (1-L·kg·min-1 vs 2-L·kg·min -1 ) in the management of acute bronchiolitis

OBJECTIVE

We aimed to compare the heated humidified high-flow nasal cannula (HHHFNC) flow rate of 1-L·kg·min^-1 (1 L) with 2-L·kg·min ^-1 (2 L) in patients with severe bronchiolitis presenting to the pediatric emergency department.

STUDY DESIGN

We performed a study in which all patients were allocated to receive these two flow rates. The primary outcome was admitted as treatment failure, which was defined as a clinical escalation in respiratory status. Secondary outcomes covered a decrease of respiratory rate (RR), heart rate (HR), the clinical respiratory score (CRS), rise of peripheral capillary oxygen saturation (SpO₂ ), and rates of weaning, intubation, and intensive care unit (ICU) admission.

RESULTS

One hundred and sixty-eight cases (88 received the 1-L flow rate and 80, the 2-L flow rate) were included in the analyses. Treatment failure was 11.4% (10 of 88) in the 1-L group, and 10% (8 of 80) in the 2-L group (P = .775). Significant variation in the intubation rate or the ICU admission rate was not determined. At the 2nd hour, the rate of weaning (53.4% vs 35%; P = .017), the falling down of the CRS (-2.1 vs -1.5; P < .001), RR (-15.2 vs -11.8; P < .001), and HR (- 24.8 vs - 21.2; P < .001), and the increase of SpO ₂ (4.8 vs 3.6; P < .001) were significantly more evident in the 1-L group.

CONCLUSION

HHHFNC with the 1-L·kg·min^-1 flow rate, which provides a more frequent earlier effect, reached therapy success as high as the 2-L·kg·min ^-1 flow rate in patients with severe acute bronchiolitis.