Using HFNC in Bronchiolitis

Using a High-flow Nasal Cannula Provided Superior Results to Diffuser Delivery in Severe Bronchiolitis: a Prospective, Randomized Controlled Study

The investigators compared oxygen therapy using the HFNC and diffuser mask (an effective low-flow oxygen delivery system) to treat patients with moderate-to-severe acute bronchiolitis admitted to an intensive care unit (ICU).

Acute bronchiolitis results from inflammation of the bronchioles and is usually caused by a viral infection. It is most common in children younger than 2 years old and is one of the most frequent reasons why a child is admitted to hospital. There is no established, specific therapy for acute bronchiolitis and it is commonly treated using supplemental oxygen and by ensuring that the patient remains hydrated. Oxygen therapy can be applied using a low- or high-flow oxygen delivery system. For example, a diffuser mask (OxyMask) is a low-flow delivery system, which is capable of delivering up to 90% of the fraction of inspired oxygen (FiO2) with low carbon dioxide (CO2) retention. In this system, the FiO2 can be adjusted by modifying the flow velocity to deliver the quantity of oxygen that the patient requires. Oxygen is supplied to the patient in a jet that flows from a device mounted on the oxygen mask. This ensures that a high concentration of oxygen is provided at a low flow rate. Additionally, CO2 retention is minimal because the mask has a fenestrated structure. Therefore, a diffuser mask is a more effective oxygen delivery method than many other low-flow delivery systems including the nasal cannula and simple oxygen mask. Oxygen therapy using a high-flow nasal cannula (HFNC) is a high-flow oxygen delivery system that enhances the efficiency of respiration by using high flow rates to clear dead space and provide fresh oxygen. This system supplies oxygen at a high flow rate through a loose nasal cannula. HFNC therapy provides heated and humidified oxygen to fill the dead space in the nasopharynx and produces minimal positive airway pressure. It enhances the passage of air through the airway by reducing inspiratory pressure. Previous studies have demonstrated that using a HFNC can decrease respiratory effort and improve gas exchange. In recent years, many studies have suggested that high-flow nasal oxygen therapy is more effective than low-flow systems. This is substantiated by significant decreases in the use of mechanical ventilation since HFNC therapy was introduced. Previous reports on the effectiveness of HFNC therapy in treating acute bronchiolitis have come primarily from observational work and there are few relevant, randomized controlled studies. Additionally, previous studies have compared HFNC therapy with less effective, low-flow systems (e.g., the simple mask or nasal cannula). To the best of our knowledge, no randomized controlled trial has compared the effectiveness of the HFNC and diffuser mask in treating bronchiolitis. In this study, the investigators compared oxygen therapy using the HFNC and diffuser mask (an effective low-flow oxygen delivery system) to treat patients with moderate-to-severe acute bronchiolitis admitted to an intensive care unit (ICU).

The patients received oxygen therapy (8-15 L/min) from an OxyMask (Southmedic, Inc., Barrie, ON, Canada) to maintain oxygen saturation (SpO2) > 92%. Oxygen therapy was halted if SpO2 was maintained at a level greater than 92% for more than 4 h. The oxygen flow rate was then decreased to 2 L/min and the patient was monitored while breathing room air.

The patients received oxygen therapy at a high flow rate from a Precision Flow nasal cannula (Vapotherm, Inc., Stevensville, MD, USA). We selected a 1.9 mm pediatric cannula, which can dispense 1-20 L/min of oxygen. The initial oxygen flow rate was 1 L/kg/min and the FiO2 was 100%. The initial flow rate was increased by 1 L/kg/min until the SpO2 reached 92%. The initial FiO2 was decreased once the SpO2 was greater than 92% and the oxygen flow rate was maintained. HFNC therapy was halted if SpO2 was maintained at a level greater than 92% for more than 4 h at a FiO2 value of 21%, and the patient was transferred to a ward.

Oxygen therapy using a high-flow nasal cannula (HFNC) is a high-flow oxygen delivery system that enhances the efficiency of respiration by using high flow rates to clear dead space and provide fresh oxygen. This system supplies oxygen at a high flow rate through a loose nasal cannula.

diffuser mask is a low-flow delivery system, which is capable of delivering up to 90% of the fraction of inspired oxygen (FiO2) with low CO2 retention. In this system, the FiO2 can be adjusted by modifying the flow velocity to deliver the quantity of oxygen that the patient requires. Oxygen is supplied to the patient in a jet that flows from a device mounted on the oxygen mask. This ensures that a high concentration of oxygen is provided at a low flow rate.

Treatment failure was defined as meeting two of the following criteria [16]: No change or an increase in respiration rate compared with baseline. No change or an increase in heart rate compared with baseline. Persistence of low SpO2 (<%92) measurements despite an adequate oxygen flow rate and FiO2 in the HFNC group/oxygen flow rate of 15 L/min in the mask group.

Inclusion Criteria: Included patients were aged between 1 and 24 months and had been diagnosed with moderate or severe acute bronchiolitis. They were admitted to the ICU, requiring supplemental oxygen, because their SpO2 measurements were less than 94% while breathing room air. Exclusion Criteria: Any patients requiring immediate respiratory support (non-invasive or invasive mechanical ventilation, altered mental status, or apnea at presentation), those already admitted to the ICU due to respiratory failure, those with underlying chronic lung disease or cardiovascular disorders, those with obstructions of the upper respiratory tract, and those with cranial malformations were excluded.

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