Hygiene Considerations for Spirometry

This article was first published in PrimaryCare Today on February 2011


Everyone performing spirometry testing knows that a new mouthpiece should be used for each new test subject, but that is not the end of spirometer hygiene procedures.

This article details the hygiene reason for a defined interval between spirometry testing, guidelines for routine cleaning and disinfection, suggests procedures in the event of contamination, the Primary Care Practice risk assessment and special considerations for mass screening. The table of annual, monthly, daily, user and individual test subject procedures is a useful guide.

Guidelines are provided on how to establish clear codes of practice to ensure safe use of equipment, safe procedures and the responsibility of the user.

The Manufacturer's Responsibility

Any responsible spirometer manufacturer owes a duty to their customers to ensure as far as is reasonably practical that their products are safe and effective using the all the knowledge available at the time they placed on the market.

The risks of infection in spirometry arise from contact with exterior surfaces and inhalation of airborne agents contained within the equipment, but mainly the risk is from contact with body fluids - namely saliva from subjects previously tested on the device.

The manufacturer is responsible to set guidelines for the design of their products and for their subsequent use and maintenance.

Healthcare Professional's Responsibility

pnuemotrac_user It is the responsibility of the user to ensure that all clinical equipment used is functional and free from harmful biological or chemical contamination at all times.

Procedures must be in place to protect both the operator and the test subject, without creating a new hazard.

The user is expected to observe the instructions for use and routine maintenance guidelines provided by manufacturers of proprietary equipment and to ensure the functional integrity of the device using tests consistent with current practice.

The designated responsible authority should establish clear codes of practice to ensure safe use of equipment, safe procedures where contamination is reasonably suspected and facilities for the safe disposal of contaminated materials.

Classification of infection risk associated with the decontamination of medical devices

RISK HIGH Items in close contact with a break in the skin or mucous membrane or introduced into a sterile body area. Recommendation: Sterilization

RISK INTERMEDIATE Items in contact with intact skin, mucous membranes or body fluids, particularly after use on infected patients or prior to use on immuno-compromised patients. Recommendation: Sterilization or disinfection required. Cleaning may be acceptable in some agreed situations.

RISK LOW Items in contact with healthy skin or mucous membranes or not in contact with patient. Recommendation: Cleaning

The Risk of Spirometer Contamination

Cases of cross-infection from Spirometers and Peak Flow Meters to test subjects have been reported. Without exception the cause has been that the user failed to use or replace the disposable mouthpiece.

Cross-infection via direct contact through the transfer of saliva and other body fluids are by far the highest risk facing the health professional.

Body fluids and other biological matter can be excreted through the lungs, particularly during a forced expiration (and also sneezing). These particles are carried by droplets which then may be deposited in the device into which the subject is conducting the forced expiration.

Responsibility of the User

In2uitive User The risk of cross infection may be reduced by the use of a SafeTway mouthpiece or a BVF (bacterial/viral filters). A BVF has the advantage of protecting sensors and the internal surfaces of the spirometer from damage and reduce the corroding effects of cleaning agents and disinfectants. The cost of filters may be offset by reduced cleaning and disinfection costs.

Both types of types of mouthpiece must be used only by one test subject and must be disposed of between test subjects because the greatest danger of cross-infection is via direct contact with bodily fluids.

For similar reasons, the measuring elements of flow sensing type spirometers need more frequent cleaning than volume displacement spirometers because of the long breathing tube which increases the distance from the test subject to the sensor.

Kendrick1 and others have shown that the deposition of such matter is directly proportional to the distance from the mouth, i.e., most deposition occurs within a few centimetres of the mouth with corresponding decrease of deposition further away from the mouth. Thus a high proportion of deposition occurs within the mouthpiece as well as the major risk of the saliva on the outside of the mouthpiece.

Facility Risk Assessment

A Risk Assessment should be carried out to assess the risks presented to both operator and subject, and an action plan devised by the facility to minimise the chance of cross infection occurring, particularly where known-infectious or immuno-deficient subjects are being tested.2

An assessment should be made of methods of decontamination available to the operator and their effectiveness against potential risks - a table of materials used in the spirometer device is essential to enable this.

In cases of high risk where no effective disinfection method is available the contaminated parts should be removed and disposed of safely.

Safe Use of Equipment

It is vital for the user to set guidelines for protective hygiene measures whilst performing spirometry testing.3 There are three main potential sources of cross contamination, skin contact; aerosolised particles and saliva/body fluids. By far the most important is the last item – a minimum requirement is to use a new disposable mouthpiece for each subject tested.

Aerosolised Particles and Mass Screening

It is recommended that a delay of at least five minutes be allowed between test subjects because it has been shown by Herbert, et. al4 that this is the safety margin required. This allows aerosolised organisms to be removed by gravitational sedimentation between tests, more sophisticated equipment may be equipped with fans and filters to speed this process. This then allows safe mass screening.

The Difference between Cleaning and Disinfection

The term "cleaning" particularly relates to the removal of proteinaceous accumulations during the removal of visible particulate contamination. This may be as simple as wiping over surfaces, but may involve washing and mechanical removal of surface particulates.

Once the item has been cleaned, some or all parts of medical devices may require disinfection. "Disinfection" is the process of applying a process to reduce the survival rate of micro-organisms, such as by immersing the item in a disinfecting solution.

For spirometers, all surfaces need to be cleaned. Parts of the device that might carry contamination, such as flowheads, should also be disinfected. Refer to the user instructions provided by the manufacturer.

In the event of a contamination that cannot be eliminated with the procedures and facilities available, the contaminated components should be removed and replaced. This should be a consideration in the facility's risk assessment, and is a special consideration for mass screening.

In no circumstances should contaminated devices be posted to a service facility. If the user is uncertain what to do, isolate the device by bagging and clearly labelling while advice is being sought.

Timetable of Hygiene Procedures

This is the timetable for annual, monthly, daily, user test hygiene:

EVERY TEST: A new mouthpiece should be used for each subject. A delay of at least 5minutes should be allowed between subjects to allow settling of previously aerosolised particles in the measuring device.

DAILY: Perform a visual inspection at the end of testing. If there is visible contamination to the flowhead or the elsewhere on the device, clean and disinfect.

WEEKLY: Clean and disinfect all parts of the equipment which have come into contact with patients.

MONTHLY: The flowhead screens or breathing tubes should be replaced regularly. The frequency of this is dependent on the Facilities' Risk Assessment, usage, and test environment, but should be at least monthly or every 100 subjects (500 blows). They should also be replaced in the event of damage, or if visibly contaminated.

ANNUALLY: Annual inspection, maintenance and calibration certification should be obtained from the manufacturer or a qualified service supplier. All these procedures are a part of the manufacturer's recommended PPM (Planned Preventive Maintenance) service procedure.5


1) K Houston, P Parry, AP Smith. Have you looked into your spirometer recently? Llandough Hospital Penarth, Breath Journal, Feb 1981.

2) Joint Statement of the American Thoracic Society and European Respiratory Society: Pulmonary Function and Exercise Testing: ATS/ERS Task Force Standardisation of Lung Function Testing: General considerations for lung function testing (2005); ATS/ERS Task Force Standardisation of Lung Function Testing: Interpretative strategies for lung function tests (2005); ATS/ERS Task Force Standardisation of Lung Function Testing: Standardisation of the measurement of lung volumes (2005). http://www.thoracic.org/statements/

3) Gold P M & Schwesinger D W. Pulmonary laboratory infection control and safety in pulmonary function testing. Guidelines & controversies, J. Clausen, Ed. Academic Press NY 1980, p.15. http://erj.ersjournals.com/content/10/8/1928.full.pdf

4) Herbert T, Miles J & Okeson G C; Contaminated aerosol recovery from pulmonary function testing equipment. Am J Respir Crit Care Med Vol 159. pp 610-612, 1999.

5) MHRA: Managing Medical Devices. http://www.mhra.gov.uk/Publications/Safetyguidance/DeviceBulletins/CON2025142