15. Respiratory Support for Asthma Exacerbation

Oxygen Support

Oxygen can be provided through several modalities; an overview is provided below.

Nasal Cannula (NC)

Nasal cannula is a low flow set up. Flow range: 1/32 LPM to 4 LPM using oxygen from the wall sources are available for use throughout the hospital. Setups can be found in the respiratory therapy box in each room. Fraction of inhaled oxygen (FiO2) is variable depending on size of child, respiratory rate, and amount of room air entrained. 

• General rules: FiO2 increases at 3-4% per liter flow (ex: 1 LPM NC = FiO2 24%) 

Simple Face Mask (SFM)

Simple face mask is also a low flow set up. Flow range must be at 6-10 LPM to prevent carbon dioxide retention. Setups can be found in respiratory therapy box in each room. Similar to nasal cannula, the true FiO2 is variable depending on size of child, respiratory rate, and amount of room air entrained. 

Partial nonrebreather face mask (NRB)

Non-rebreather face masks can be done on the floor and can deliver FiO2 up to ~70%. These are generally considered a low flow oxygen delivery system with a high FiO2. Flow is usually set between 10-15 LPM and reservoir bag must remain inflated.

• Caveat: Respiratory therapists must let attending MD know if FiO2 demands meet or exceed 50%.
  
  
• Could consider using if mouth breathing.
  
  
• Venturi Face Mask: Can be done on the floor. Low- High flow device. Flow can range between 2 LPM to 14 LPM with FIO2 of 24 – 55%. It is more precise for maintaining FiO2 and should be. Considered in patients with mouth breathing.
   
• CMH Caveat: Respiratory therapists must let attending MD know if FiO2 demands meet or exceed 50% as this may be an indication of worsening respiratory failure. 

High Flow Nasal Cannula (HFNC)

For high flow nasal cannula (HFNC) to be considered high flow set up, flow needs to be above 10 LPM. Flow rates can go up to 60 LPM and FiO2 can be titrated from 21% to 100%.

At Children's Mercy HFNC is available on the floor for patients admitted for bronchiolitis with a max of 2 LPM per kg up to 15 LPM. This is NOT for patients in an acute asthma exacerbation. If a patient with asthma exacerbation is suspected to benefit from HFNC, communication needs to occur between attending physician, bedside respiratory therapist and nursing to discuss safety and patient placement.

Noninvasive ventilation (NIV)

Positive pressure ventilation that is provided through a facemask/nasal mask set up. This is also referred to by the type of pressure delivered: continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP). Oxygen may be “bled” into the system for delivery.

Intubation and mechanical ventilation

A.k.a. invasive ventilation. Mechanical ventilation for asthma is covered in the PICU section.

Albuterol therapy

• Albuterol therapy can be provided via metered dose inhaler (MDI) or nebulizer.
  
  
• At present, albuterol therapy is titrated on the floors using the Respiratory care score.
  
  
• For continuous nebulized albuterol, a weight-based dosing is suggested based on concerns for side-effects of albuterol at higher doses and consistency of dosing:
  
  
  • <20 KG: 10 mg/hr
    
    
  • >20 KG: 15 mg/hr 
    
    
• A patient may continue on the inpatient unit at the Adele Hall Campus on continuous albuterol for greater than four hours if assessed to be improving. Improvement is defined as at least two of the following:
  
  
  • Decreased respiratory rate (RR)
    
    
  • Decreased oxygen requirement
    
    
  • Decreased Respiratory Care Score
    
    
  • Decreased Pediatric Early Warning Score (PEWS)
    
    
• Total delivery time of continuous albuterol outside the PICU should be considered cumulative, e.g. from ED to inpatient floor. 
  
  
• Providing the patient a “therapeutic break” from continuous albuterol does not restart the 4 hour limit.
  
  
• If a patient is on continuous albuterol, provider should be aware of the possibility of impending failure and need for monitoring. Respiratory therapists evaluate patients every 30 minutes for the first hour on continuous albuterol and every 1 hour subsequently. Communication must be open between physician and RT throughout. 
  
  

Consideration for need to increase to higher level of care should be considered if there is concern for impending or actual respiratory arrest. The progression from respiratory distress to respiratory failure to respiratory arrest can vary by patient. Respiratory failure can progress rapidly and be difficult to reverse. Therefore, it is important to emphasize the signs of impending respiratory arrest (e.g. altered level of consciousness, hypercapnia, silent chest or absence of wheezing, worsening hypoxemia). 

• Reference: https://www.nhlbi.nih.gov/sites/default/files/media/docs/EPR-3_Asthma_Full_Report_2007.pdf