Bacterial Contamination risk
of compressed air atomizers – Are we unintentionally infecting our
patients?
By Tim Wolfe, MD
Introduction:
Improperly sterilized devices used to administer topical medications to the upper and lower airway may lead to serious nosocomial infections.1-4 With the emergence of incurable viral infections and antibiotic resistant bacteria the problem of cross infection from contaminated devices is even more concerning.5, 6 Many otolaryngologists use Venturi principle atomization devices (the compressed air driven atomizer on most SMR carts) that may be cross-contaminating patients with pathologic microorganisms when reused.3, 7, 8 This newsletter will briefly review the mechanism of action of Venturi principle atomizers and why this may be leading to inadvertent cross-contamination of patients.
Venturi Principle atomizer -
Mechanism of action (Figure 1):
Venturi atomizers have a fine inner tube contained within a slightly larger outer tube. The outer tube is connected to an air source, either a bellows or compressed wall air. Both the inner and outer tubes open at the nozzle tip where the outer tube is slightly tapered. The other end of the inner tube is connected to the fluid reservoir. When air is forced under pressure through the outer tube it creates negative pressure at the tip, which sucks fluid up the inner tube out of the medication reservoir, and a spray is formed. At the moment the air flow ceases, the fluid column collapses and contaminants on the tip are aspirated from the tip of the nozzle into both tubes. If the tip is still in the patient’s nostril or mouth or if bacteria have splashed back onto the tip, contaminant from the patient may be aspirated into the atomizer and potentially passed from one patient to another. This will occur even if a protective nasal cap is in place over the end of the device since these caps do not cover the hole through which fluid exists (and enters).
Figure 1: Venturi Principle Atomizer
Literature
discussion:
In 1993 Coakley et al noted that most British otolaryngologists used Venturi atomizers, did not cleanse the inside of their atomizers between patients, used the devices on multiple patients per day and had variable policies for medication replacement ranging from daily to weekly to whenever the bottle was empty.7 These authors, using a dye preparation, demonstrated that even a single use of a Venturi type atomizer resulted in dye contamination of both the internal nozzle lumens and the medication reservoir. Spraggs et al showed that this Venturi effect resulted in direct internal bacterial contamination of these devices after a single nasal application of topical anesthesia to healthy human volunteers.8 He also noted that the preservatives in topical anesthetics did not prevent bacterial growth. Finally, due to the intricate design of the nozzle tubing he found that sterilization required the use of a vacuum autoclave – something not available in most otolaryngology offices. Southwick, et al, describe the cross-infection of two patients with mycobacterium tuberculosis presumably transmitted by a Venturi atomizer that had been contaminated several hours earlier from a patient with active tuberculosis.3 All three authors recommend a disposable atomizer be used on each patient due to the significant risk of cross-contamination and the expense required to sterilize a Venturi atomizer in a vacuum autoclave.
This information should provide some food for thought. Because otolaryngologists see a selected population of patients with complicated and often-resistant sinonasal infections, the use of a device that may pass pathologic organisms from one patient to the next needs careful re-examination.
References:
1. Cobben NA, Drent M, Jonkers M, Wouters EF, Vaneechoutte M, Stobberingh EE. Outbreak of severe Pseudomonas aeruginosa respiratory infections due to contaminated nebulizers. J Hosp Infect 1996; 33:63-70.
2. Woo AH, Goetz A, Yu VL. Transmission of Legionella by respiratory equipment and aerosol generating devices. Chest 1992; 102:1586-90.
3. Southwick KL, Hoffmann K, Ferree K, Matthews J, Salfinger M. Cluster of tuberculosis cases in North Carolina: possible association with atomizer reuse. Am J Infect Control 2001; 29:1-6.
4. Michele TM, Cronin WA, Graham NM, et al. Transmission of Mycobacterium tuberculosis by a fiberoptic bronchoscope. Identification by DNA fingerprinting. Jama 1997; 278:1093-5.
5. Brown P, Will RG, Bradley R, Asher DM, Detwiler L. Bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease: background, evolution, and current concerns. Emerg Infect Dis 2001; 7:6-16.
6. Bagot d'Arc M. The otolaryngologist and Creutzfeldt-Jakob disease. Rev Laryngol Otol Rhinol 1998; 119:7-12.
7. Coakley JF, Arthurs GJ, Wilsher TK. The need for and development of a single use disposable nasal spray. J Laryngol Otol 1993; 107:20-3.
8. Spraggs PD, Hanekom WH, Mochloulis G, Joseph T, Kelsey MC. The assessment of the risk of cross-infection with a multi-use nasal atomizer. J Hosp Infect 1994; 28:315-21.