The Nebulizer - More Than Smoke and Mirrors?

The Gist:  Metered dose inhalers (MDIs), utilized with a spacer, are at least as effective, if not more effective than nebulized bronchodilators during most asthma exacerbations [1].  The key with this modality exists in properly dosing the MDI (on the order of 8-10 puffs), the use of a spacer, and education of both patients and staff regarding why this modality is chosen over a nebulized treatment. (updated 10/25/13)

Medical Myth:  An individual with an asthma exacerbation should receive bronchodilators via nebulizer.
Actual Answer: This is false in most cases, where patient has decent inspiratory effort and is not in extremis.  This makes sense if you've ever seen someone receiving a nebuilzed treatment - the fog is everywhere.  Studies have radiolabeled particles to determine the amount that actually reaches the lung and this amount is much less when nebulized than with a properly delivered MDI+spacer.  This is why we give a higher dose for the nebulized route of administration - the particles are seeping out of the mask into the curtains, etc) [5].

Why do people still use nebulizers in this patient population?

• Many patients expect that when they present to the ED with an asthma exacerbation, they will receive a nebulizer.  This is somewhat understandable, particularly if they failed their normal "rescue" inhaler at home.  
• There's the lure of the mysterious fog that pours out of delivery device. 
• Nurses and respiratory therapists (RT) can walk away during the deliver of a nebulized beta-agonist treatment whereas MDI + spacer therapy requires the nurse/RT at the bedside. 
• An article by Osmond et al details some of the barriers to use of MDI+spacer in most mild to moderate asthma exacerbations in the ED.

But MDI + spacer in the ED is a good idea..  

• Use in the ED or in the hospital/office setting offers the ability to reinforce this modality as an excellent means of treating asthma exacerbations.  This may re-inforce
• Supervised use of MDI + spacer proffers the opportunity to educate patients and families on the proper inhaler technique.  
• Even young kids can actually be quite good with the spacer face mask and this also reinforces to the parents that the child is, indeed capable of using an inhaler.
• Cost-effective [6].
• Takes less time - this is a point of contention.  Hospital staffing and protocols regarding who delivers medication (respiratory therapy vs. nursing) may alter the perceived time or effort.
• Nebulizer machines are often filthy.  While on a pediatric rotation in the rural deep south, I found that nearly every family seemed to have a "breathin' machine" at home or had used one of a friend/family member on their own.  How many do you think had ever been cleaned?

Evidence?  Cochrane reviews since 1997 have supported the use of MDI+spacer in acute asthma exacerbations.  In 2013, the Cochrane review concluded that, when treatments are titrated to patient response, MDI + spacer is at least comparable to nebuliser delivery in adults and children with regard to hospital rates.

• Adults -Risk ratio (RR) of MDI+spacer vs nebuliser was 0.94 (95% CI 0.61-1.43). 
• Children - RR 0.71 (95% CI 0.47-1.08).

The review also showed a 33 minute (95%CI -43 to -24 min) shorter ED length of stay in children with MDI+spacer compared with nebulizer (70 min vs 103 min), with similar LOS for adults [1].

A Look at The Goh Study

• Methods: Comparison of  hospitalization and re-admission rates between 10,258 cases treated in 2000–2002 and 9,693 cases treated in 2004–2006 for asthma exacerbation in the ED. In 2003, the ED switched from using nebulizers to MDIs. The number of salbutamol puffs in the ER was standardized to 10 puffs for children >10 kg and 5 puffs for children <10 kg, and ipratropium bromide was given routinely to all children. 
• Results:  
• No increase in the admission rate to inpatient care (30.3% vs. 31.2%) nor in the admission rate to intensive care (0.21% vs. 0.20%) units. 
• Average length of hospital stay was 2.67 days versus 2.27 days before and after the change, respectively.  
• A significant reduction was seen in the re-admission rate within 72 h after departure to home from the ED following the change (5.2% vs. 3.8%)

Limitations:

• Some patients may benefit more from a nebulizer than an MDI; however, these might be the patients who actually need positive pressure ventilation through non-invasive ventilation or high flow nasal cannula.  These patients are often the ones who will end up needing to be admitted and are receiving everything in the arsenal for management of asthma exacerbations.
• Age limitations may exist, as coordination of inspiratory effort for delivery of the medication to the lungs may not be achievable in the youngest populations.

References:

1. Cj C, Ej W, Bh R. Holding chambers ( spacers ) versus nebulisers for beta-agonist treatment of acute asthma. Cochrane Database Syst Rev. 2013 Sep 13;9:CD000052.
2. Osmond MH, Gazarian M, Henry RL, Clifford TJ, Tetzlaff J. Barriers to metered-dose inhaler/spacer use in Canadian pediatric emergency departments: a national survey. Acad. Emerg. Med. 2007;14(11):1106–13. 

3. Goh AE, Tang JP, Ling H, et al., Efficacy of metered-dose inhalers for children with acute asthma exacerbations. Pediatr Pulmonol2011; 46: 421–427. DOI: 10.1002/ppul.21384.

4.  Castro-Rodriguez JA, Rodrigo GJ. Beta-agonists through metered-dose inhaler with valved holding chamber versus nebulizer for acute exacerbation of wheezing or asthma in children under 5 years of age: a systematic review with meta-analysis. J Pediatr 2004;145:172–7.

5.  Dolovich MB, Ahrens RC, Hess DR, et al. Device selection and outcomes of aerosol therapy: evidence-based guidelines: American College of Chest Physicians/American College of Asthma, Allergy, and Immunology. Chest 2005 Jan;127(1):335-71.
6. Doan Q, Shefrin A, Johnson D. Cost-effectiveness of meter-dose inhalers for asthma exacerbations in the pediatric emergency department. Pediatrics 2011; 127(5): 1105-1111