From the Guidelines
Consider initiating High Flow Nasal Cannula (HFNC) for a 13-year-old with asthma exacerbation when they show signs of moderate to severe respiratory distress despite initial treatments with bronchodilators and steroids, as it may reduce the need for intubation and improve patient comfort, as suggested by recent guidelines 1. Specifically, look for persistent tachypnea (respiratory rate >30), significant work of breathing, oxygen saturation <90% despite supplemental oxygen, or rising CO2 levels (if available).
- HFNC is often tried first at flow rates of 1-2 L/kg/min (typically 20-40 L/min) with FiO2 titrated to maintain oxygen saturation >92% 1.
- If the patient continues to deteriorate or shows minimal improvement after 1-2 hours on HFNC, consider escalating to BiPAP with initial settings of IPAP 10-12 cmH2O and EPAP 5 cmH2O, which can be titrated up as needed 1.
- BiPAP is particularly beneficial for patients with significant CO2 retention as it reduces work of breathing and helps prevent intubation. Throughout either intervention, continue standard asthma treatments including:
- Albuterol (2.5-5 mg) every 20 minutes to hourly
- Ipratropium bromide (0.5 mg) every 4-6 hours
- Systemic steroids (prednisolone/prednisone 1-2 mg/kg/day) 1. These non-invasive respiratory supports help reduce the work of breathing, improve ventilation, and may prevent progression to intubation while medications take effect. The most recent and highest quality study on this topic is from 2021, which suggests that HFNC is a suitable alternative to noninvasive ventilation for initial or postextubation management of acute respiratory failure 1.
From the Research
Asthma Exacerbation Treatment
When considering treatment for a 13-year-old with asthma exacerbation, the decision to order BiPAP or high flow NC depends on several factors.
- The patient's respiratory status and oxygen requirements should be assessed to determine the most appropriate treatment option.
- High-flow nasal cannula (HFNC) oxygen therapy has been shown to be effective in reducing dyspnea and improving oxygenation in patients with respiratory failure from various etiologies, including asthma exacerbation 2, 3.
- A study on patients with severe bronchial asthma complicated with respiratory failure found that HFNC was more efficient than conventional oxygen therapy (COT) in elevating PO2, and it significantly reduced heart rate and respiratory rate 3.
Predictors of Successful HFNC Treatment
- The pulse oximetric saturation to fraction of inspired oxygen (SpO2/FIO2) ratio 24 hours after initiating HFNC has been identified as a good predictor of successful HFNC treatment in patients with acute exacerbation of interstitial lung disease 4.
- In patients with asthma exacerbation, the flow ratio, which is the HFNC flow divided by inspiratory flow, can be used to determine the actual FiO2 and predict the effectiveness of HFNC treatment 5, 6.
Considerations for HFNC Flow Rate
- The actual FiO2 delivered by HFNC can vary depending on the respiratory rate, tidal volume, and HFNC flow rate, and may not always match the set FiO2 on the device 5, 6.
- A flow ratio greater than 1.435 can produce an FiO2 greater than 0.9, but a flow ratio greater than 1 does not ensure a constant high FiO2 5.
- The addition of a dead space in the breathing circuit can significantly decrease the variability in FiO2 delivery and improve the effectiveness of HFNC treatment 6.