High-flow nasal cannula therapy in paediatric intensive care: Indications, efficacy and predictors of failure

INTRODUCTION

Respiratory distress is a common reason for admission to paediatric intensive care unit (PICU).^[1] It is characterised by increased respiratory effort, hypoxia and impaired ventilation, and may arise from a variety of infectious and non-infectious aetiologies, including bronchopneumonia, bronchiolitis, asthma and acute respiratory distress syndrome (ARDS).^[1] While mechanical ventilation remains the cornerstone for managing severe respiratory distress, it is associated with significant risks, including ventilator-associated pneumonia, barotrauma, prolonged sedation and increased healthcare costs.^[2] In this situation, high-flow nasal cannula (HFNC) therapy has emerged as a viable option that can fill the gap between traditional oxygen therapy and non-invasive ventilation (NIV).^[3] HFNC delivers warmed and humidified air-oxygen mixtures at high flow rates that are higher than what they need to breathe in. This has a number of physiological benefits, such as better mucociliary clearance, less airway resistance, dead space washout and a certain amount of positive end-expiratory pressure.^[4]

These benefits translate to reduced work of breathing and better oxygenation in children with respiratory compromise. Although widely studied in bronchiolitis, the role of HFNC in diverse paediatric respiratory conditions and across different age groups remains under-explored, especially in low- and middle-income settings.^[5] This study was designed to evaluate the indications, safety and efficacy of HFNC therapy in children admitted to the PICU with respiratory distress, to inform and improve the use of non-invasive respiratory support in such contexts.

MATERIAL AND METHODS

This hospital-based prospective observational study was conducted from January to December 2022 in a tertiary PICU. All children (aged 1 month–16 years) admitted to the PICU with respiratory distress of any aetiology and initiated on HFNC therapy were included in the study.

Children with cyanotic congenital heart disease, children requiring immediate non- invasive or invasive ventilation at presentation, and those receiving HFNC solely as post-extubation support were excluded from the study. Ethical clearance was obtained from the Institutional Ethics Committee, and the study was conducted in accordance with the Declaration of Helsinki (2013). Informed consent secured from guardians/parents.

HFNC therapy using OptiflowTM was administered according to protocol, with flow rates set at 1–2 L/kg/min and FiO₂ titrated between 30% and 100% to maintain SpO₂ ≥94%. Patients were monitored hourly for clinical parameters, including respiratory rate, heart rate and SpO₂, as well as respiratory clinical score (RCS), SpO₂/FiO₂ (SF) ratio and any adverse events such as nasal injury or air leaks. Data collection included demographic details, presenting symptoms, physical examination findings, radiological and laboratory results, RCS, SF ratio, Comfort Score, and HFNC settings (FiO₂, flow rate, and duration of therapy). We looked at how the patients reacted to HFNC at 1, 6, 12 and 24 h after it started. The primary outcome was the success of HFNC, characterised by the avoidance of NIV or mechanical ventilation, whereas failure was indicated by the necessity for escalation due to ongoing or exacerbating respiratory distress, at any time during the hospital stay. Demographics, comorbidities, arterial blood gas (ABG) parameters and the presence of multi-organ dysfunction syndrome (MODS) were some of the things that could help predict outcomes.

Statistical analysis was performed using the Statistical Package for the Social Sciences v25. Continuous variables reported as mean ± standard deviation; categorical variables as frequencies. Chi-square/Fisher’s exact test compared failure/success groups. Receiver operating characteristic curve analysis was used, where applicable, to identify predictors of HFNC failure.

RESULTS

A total of 29 children were included. Majority were infants (13 children), followed by children aged 1–5 years (9 children) and those >5 years (up to 13 years) (7 children), with a mean age of 3 years. Male predominance was noted (19 cases). The most common indication [Table 1] was bronchopneumonia, followed by aspiration pneumonia. Overall, the HFNC success rate was 82.8% (24 out of 29). Complications were mild, with nasal erythema in 5 children and epistaxis in 1 child. No air leak syndrome was noted in this study.

Before HFNC initiation, nasal prongs were the most frequently used oxygen delivery method (13 children), followed by oxygen mask (8 children). Smaller proportions of participants were on no oxygen support (4 children), nonrebreathing mask (2 children) and oxygen hood (2 children).

Table 2 shows that pneumonia (including aspiration) was the most common indication for HFNC. Higher FiO₂ requirements and need for escalation were more frequent in pneumonia and bronchopneumonia with complications, whereas bronchiolitis and wheezing disorders showed shorter HFNC duration and minimal escalation.

The mean duration of HFNC therapy in this study was 3.5 days. Prolonged HFNC support (11–14 days) was predominantly required in patients associated with neurological comorbidities, such as progressive myoclonic encephalopathy and mitochondrial cytopathy.

HFNC initiation resulted in significant improvement in respiratory distress, as reflected by a reduction in RCS and an improvement in SF ratio at 12–24 h. Patient comfort scores improved within the 1^st h of therapy, while paediatric risk of mortality scores indicated low baseline illness severity [Table 3].

Analyses of variables with HFNC failure are summarised in Table 4. Age, gender, nutritional status, immunisation status, and time of initiation of HFNC were not significantly associated with HFNC failure. Factors predicting failure included ARDS, presence of comorbidities, MODS, deranged renal function and acidosis.

DISCUSSION

HFNC has emerged as a preferred non-invasive respiratory support modality in paediatrics due to its ease of use, better tolerance, and physiological benefits such as washout of nasopharyngeal dead space, improved mucociliary clearance and generation of low-level positive airway pressure.^[3,6] Before HFNC became available, conventional nasal cannula flows were limited by discomfort and mucosal drying, restricting effective oxygen delivery.^[6]

HFNC now offers a safe method to deliver heated, humidified, blended oxygen at higher flows across all paediatric age groups.

In our cohort, the majority of children presented with classical features of acute respiratory distress, including tachypnoea, retractions, hypoxemia and associated systemic symptoms such as fever, cough and poor feeding. These findings are comparable to existing literature, including reports by Angurana et al.^[7] and others, who describe similar clinical profiles among children requiring intensive respiratory support.

In our study, laboratory changes such as leucocytosis, anaemia and thrombocytosis probably show the underlying infectious or inflammatory cause. The range of radiographic and ABG findings, such as patchy opacities and mixed respiratory acidosis/alkalosis, is similar to what has been seen before in lower respiratory tract infections in children. The variations in radiological profiles, in contrast to studies solely concentrating on bronchiolitis (e.g., Angurana et al.^[7]), can be attributed to our more extensive spectrum of diagnoses.

In our study, pneumonia, aspiration pneumonia, wheezing-associated disorders and bronchiolitis were the primary indications for the initiation of HFNC. These diagnoses are quite similar to what was found in earlier studies, like those by Mustafa et al. and Kelly et al.,^[8,9] which showed that lower respiratory tract infections were the main reason for HFNC use and that the success rates were similar. The mean duration of time we used HFNC therapy was similar to what has been reported around the world and most children responded well within the first 12–24 h.

A notable finding in our study was that the respiratory rate, heart rate and SpO₂ all steadily improved after starting HFNC [Figure 1]. Respiratory rate and heart rate showed a declining trend, while SpO₂ improved within the first 12–24 h, suggesting a reduction in work of breathing and better oxygenation. Similar early responses have been reported by Asseri et al.,^[10] Chang et al.,^[11] and Kallappa et al.^[12] confirming HFNC’s effectiveness in reducing the work of breathing and improving oxygenation during the early stages of therapy. The simultaneous improvement in RCSs and the maintenance of optimal SF ratios further support the effectiveness of HFNC.

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Figure 1: Vitals comparison before and after high-flow nasal cannula (HFNC). (RR: Respiratory rate, HR: Heart rate).

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HFNC was well tolerated in our cohort. Adverse effects observed were minimal, limited to mild nasal erythema or epistaxis, with no serious complications observed. Even though there have been reports of pneumothorax, abdominal distension and mucosal injuries in earlier studies,^[13] these appear to be uncommon with appropriate monitoring and use.

Certain clinical factors were associated with HFNC failure in our study. The presence of MODS, having deranged renal function, type 2 respiratory failure and metabolic acidosis, frequently required escalation of support. These findings are consistent with research conducted by Nguyen et al.^[14] and others, indicating elevated failure rates in children exhibiting systemic organ dysfunction or metabolic disturbances.

Children with ARDS and those with serious comorbidities (such as cardiac, neurological or genetic disorders) were also more likely to need escalation of respiratory support in our study. Similar observations have been reported by Kleiman et al.^[15] and Paediatric Acute Lung Injury Consensus Conference,^[16] recommendations. These findings highlight the need for early recognition of high-risk subgroups and enhanced monitoring to facilitate prompt escalation to NIV or intubation, if required.

Overall, HFNC was found to be an effective and well-tolerated method of respiratory support for children with acute respiratory distress. However, this study was conducted at a single centre with a limited sample size, potentially restricting its generalisability. Long-term outcomes following discharge were also not assessed. Early improvement in clinical parameters appeared to correlate with successful outcomes. Children with comorbidities or systemic illness require closer monitoring during HFNC therapy due to a higher risk of deterioration and treatment failure. These findings may guide monitoring strategies and timely escalation of care, particularly in resource-limited PICU settings.

CONCLUSION

HFNC appears to be a useful and well-tolerated respiratory support modality for the management of paediatric respiratory distress. It is associated with early improvement in vital signs and oxygenation with minimal adverse effects. Most children can be successfully managed without escalation, although comorbidities, multi-organ dysfunction and metabolic derangements increase the risk of failure. Early recognition of high-risk patients and close monitoring are essential to guide timely escalation and improve outcomes.