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Communications to the Editor |

Using Barrier Filters To Protect Spirometer Sensors From Droplet Deposition FREE TO VIEW

Yuguang Zhang, MB
Author and Funding Information

Gosford Hospital, New South Wales, Australia

Correspondence to: Yuguang Zhang, MB, Respiratory Investigation Unit, Respiratory Medicine, Gosford Hospital, Holden St, Gosford, New South Wales, Australia; e-mail: zhangyg@tpg.com.au



Chest. 2005;127(6):2294. doi:10.1378/chest.127.6.2294-a
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Published online

To the Editor:

I read with great interest the recent article by Townsend et al1 (May 2004), who detail the problems of zero errors and sensor obstruction with flow-type spirometers during lung function tests. It is very astonishing that in those screening programs, a dozen of “grossly overestimated” FVC results (160 to 316% of predicted) had been accepted by some professionals. The authors alert the relevant spirometer users to the potential errors of flow-type spirometers and highlight the importance of quality control in lung function tests.

I agree with most of the authors’ recommendations, and would like to comment on recommendation 6. I think their recommendation, that if “one sensor is used for all subjects, it should be cleaned frequently, following manufacturer instructions” is somewhat ambiguous, because neither the authors nor most spirometer manufacturers have actually specified the cleaning frequency of spirometer sensors (eg, being cleaned between subjects, daily, or weekly). With my experience, it is relatively easy to identify zero errors, but it is very difficult (if not impossible) to identify the problems of subtle partial blockage by droplets or water vapor condensation in pneumotachometers, just as pointed out by the authors as “elevating a subject’s 90% of predicted to 110% or inflating 70% of predicted to 90% is unlikely to cause suspicions of equipment errors.” I believe we should do everything possible to protect spirometer sensors from droplet deposition in lung function testing. The most practical and effective way would be the application of a single-use barrier filter (with high filtration efficiency rate, low resistance, and small dead space) in every spirometer for each subject. If so, we could easily solve the partial blockage problems in a spirometer with a heated flow-sensor, because a subject’s droplets of saliva and mucus could be completely captured by the barrier filter and the condensation of water vapor would not be formed. For a spirometer with an unheated flow sensor, flushing air through the sensor by a calibration syringe or an unheated hairdryer after each subject’s use could remove condensation. More importantly, cross-infection risks can be minimized during lung function tests by using the single-use barrier filter for each subject.

Townsend, MC, Hankinson, JL, Lindesmith, LA, et al (2004) Is my lung function really that good? Flow-type spirometer problems that elevate test results.Chest125,1902-1909
 

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References

Townsend, MC, Hankinson, JL, Lindesmith, LA, et al (2004) Is my lung function really that good? Flow-type spirometer problems that elevate test results.Chest125,1902-1909
 
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