Introduction
An HFNC (high-flow nasal cannula) is a method of respiratory support that is commonly used prior to endotracheal intubation or invasive ventilation. A decrease in nasopharyngeal resistance, washout of dead space, a decrease in the ambient air intake, and an increase in airway pressure are the components of the mechanical action of HFNCs. The first noninvasive respiratory support after birth and the avoidance of reintubation are both possible with HFNC in preterm infants. Adjustments to the flow level are essential for children because of their complication risk and maximum efficacy. Followed by subsequent low-flow oxygen failure, randomized controlled studies suggest that HFNC may be used in patients with moderate to severe bronchiolitis.
In addition, HFNC can decrease the need for mechanical ventilation and intubation in kids with respiratory failure. HFNC has been shown to be helpful in acute asthma and other respiratory distress in several observational studies. It is necessary, especially for children, to develop clinical guidelines for HFNC that cover flow settings, indications, contraindications, device management, efficacy identification, and safety concerns.
What Is the Action Mechanism of High-Flow Nasal Cannula Oxygen Therapy?
Heated humidified HFNC oxygen therapy is the full name of HFNC. Cold, dry air can cause mucosal injury and patient discomfort. Adjustable (FiO2 21 to 100 percent) heated (34° C to 37° C) oxygen with nearly 100 percent relative humidity can help counteract these issues. Heated humidification can help with secretion clearance and reduce bronchoconstriction. According to the clinical situation, the basic principle of HFNC is to set a higher oxygen flow than the inspiratory demand flow. This can result in upper airway washout, decreased nasal resistance, and reduced dead space. HFNC induces positive airway pressure, which leads to alveolar recruitment of collapsed lesions and an increase in functional residual capacity. Furthermore, HFNC decreases the ambient air inflow, reduces the dilution of desired gas composition, and enhances oxygenation. Its mechanism of action does not distinguish between adults and children based on age.
What Are the Flow Setting and Cannula Size?
Patients of all ages can benefit from a higher flow setting than in inspiratory demand. In an experimental study, it was found that the airway pressure generated by a high-flow system varies and is affected by flow amount, cannula and nares size, and degree of mouth opening. Positive lung-distending pressure increased with the flow from 0 to 12 L/min in the experimental setting. Recent research found that children and adults with HFNC had limited pressure delivery of two to four centimeters H2O in the pharynx and esophagus.
The flow of 1 to 2 L/kg/min (up to 20 L/min) and 3 L/kg/min was tolerated by patients younger than 24 months. Despite the same efficacy, patients found 3 L/kg/min uncomfortable. The reasonable flow rate is thought to be 1 to 2 L/kg/min up to 10 kg in patients, with an increase of 0.5 L/kg/min, taking into account the flow limitation in adults (50 to 60 L/min). There were no differences between 2 L/kg/min of HFNC and 7 cm H2O of CPAP (continuous positive airway pressure) in terms of the length of stay in the intensive care unit (ICU) or the requirement for mechanical ventilation, according to one study comparing the effectiveness of the two treatments. Interestingly, among 67 hospitals, there was a significant variation in the maximum flow rates (L/min) for the various age groups.
What Are the Indications of High-Flow Nasal Cannula Oxygen Therapy?
Indications from the evidence in adults include acute hypoxemic respiratory failure, post-extubation support, preoxygenation before intubation or during bronchoscopy, postoperative respiratory failure, and acute pulmonary edema. Several more pediatric studies encompass patients with acute bronchiolitis. Other indications include asthma, sleep apnea, pneumonia, transport of a critical patient, and post-extubation respiratory support.
Pneumothorax, hemodynamic instability, facial bone or skull base trauma, life-threatening hypoxia, and abnormalities of the upper airways may render HFNC ineffective or potentially dangerous, which are some of the contraindications. A careful approach should be taken when administering HFNC to patients with congenital heart disease, acute asthma, chronic respiratory failure, and those with a decreased level of consciousness.
What Are the Safety Concerns in Children?
In the ED (emergency department), PICU (pediatric Intensive care unit), and pediatric general ward, HFNC is typically safe. Pneumothorax, pneumomediastinum, and other forms of barotrauma are well-known complications of HFNC. There have been few reports of serious pneumothorax in children. This was reported even in a low-flow situation (6 L/min in a 22-month-old child), suggesting that careful observation is necessary. Barotrauma is a condition that can result from using a cannula that is too large. Injuries to the nasal mucosa, as well as abdominal distention, can happen. It has occasionally been noted that children fail to follow the HFNC.
Three pneumothorax and pneumomediastinum episodes have recently been linked to the use of HFNC. An improper gauge size obstructing the nostril lumen may be linked to the risk of air leak syndrome. The significant intra and inter-patient variation in the pressures generated in the airways present another challenge with this device as a CPAP replacement. The safety of this practice is unknown because subsequent changes in generated pressure are not measured. Flow rates may be adjusted to the changing status of respiratory distress.
What Are the Side Effects and Monitoring of HFNC?
HFNC differs from traditional oxygen therapy in that it offers a heated and humidified air flow to help with the uncomfortable feeling of a dry mouth. ICU patients frequently list this annoyance as a source of pain. Skin lesions are reported less frequently, with better cutaneous tolerance than other CPAP delivery systems. This device does have disadvantages, just like any other respiratory support system. The noise level, for instance, reaches about 80 dB. The decibel level varies depending on the flow and may be higher than that produced by other CPAP systems.
When to Initiate HFNC?
HFNC can be used to manage moderate respiratory distress in emergency departments and during pre or inter-hospital transport, even though the majority of studies of HFNC therapy have focused on ICUs. One of its benefits is that HFNC requires little technical expertise to set up and use. However, starting this kind of respiratory support requires advanced expertise in treating acute pediatric respiratory illnesses, sufficient technical oversight, and a high staff-to-patient ratio. In a setting prepared for quick implementation of invasive ventilatory support, the risk of decompensation necessitates very close monitoring.
Discharge from the ICU and transfer to a pediatric ward should be considered only after these children have made significant progress. However, the ward where the child is admitted should be kept under close watch over the child and have a central alarm system to quickly recognize respiratory failure or decompensation symptoms.
Conclusion
Despite the lack of definite advantages in the medical literature, HFNC use is rising in pediatric wards. Although infants with moderately severe bronchiolitis are the indication most frequently cited in publications, recent reports indicate that HFNC may also be used effectively and safely for a wider range of patient ages and diagnoses. The system is appealing due to its simplicity and high tolerance. On a practical level, this treatment should be started in the emergency room or the pediatric intensive care unit in order to assess its efficacy and detect failure indicators as early as possible, necessitating a more suitable respiratory support system.
