Although negative consequences are rare when performing spirometry, they can occur. Poorly- or under-trained staff can also broaden the spectrum of risk for patients.

By Matthew J. O’Brien, MS, RRT, RPFT

Spirometry is overall a very safe diagnostic tool performed in pulmonary labs, clinics, emergency rooms and physician offices. Although negative consequences are rare when performing spirometry, they can occur. Additionally, spirometry performed poorly- or under-trained staff can broaden the spectrum of risk for patients. This article will discuss some of the risks associated with improper pulmonary function testing using spirometers.

Syncope / Temporary Loss of Consciousness

Experienced staff have all witnessed the patient who demonstrates a temporary fog or glazes over toward the end of a forced expiratory maneuver; some even slump over a bit as they try their best to blow all the way out. Staff often develop a cadence or auctioneer quality when coaching a patient. “Keep pushing, push, push…don’t stop…all the way out now.” For most patients with moderate to severe chronic obstructive lung disease, they can exhale for six seconds with ease and 15 seconds is often no problem. Remember that blowing longer will increase the FVC, decrease the FEV1/FVC ratio and make the FEF25-75 smaller and smaller.

At my facility, we recently had two patients lose consciousness for just a moment, while performing spirometry, sitting in the plethysmograph, and both tumbled forward requiring a visit to the ER for stiches. The bottom line is, don’t over-coach your patients. Pay close attention to them during forced maneuvers and stop the maneuver if it looks like the lights are going dim. Consider using FEV6 and FEV1/FEV6 parameters or reference equations recommended by the National Lung Health Education Program (NLHEP).1-2 Expirations longer than 15 seconds seldom change clinical decisions.3

Infection Control and Prevention

Protecting patients from cross contamination should be a priority in all healthcare environments. Regardless of how busy you are, you need to adhere to a standardized workflow when initiating patients for spirometry testing.

  1. What is your patient’s status: Respiratory Isolation, protective isolation, contact precautions, MRSA, MDR, CRE, c-diff or cystic fibrosis?  Review the patient’s electronic medical record (EMR) for status, allergies and medication list prior to testing.
  2. Proper hand sanitization. Gel-in or washing your hands in the presence of the patient are a good demonstration that you care about this important step. Not every spirometry testing area may have a sink, so hand gel or foam sanitizers are a great choice.   Offering patients to gel-in is also acceptable.
  3. Place the filter on spirometer adaptor or flow-sensor, being careful to not touch the patient side of the filter/mouthpiece. If you do this carefully you can use the plastic wrap the filter comes in to act as a barrier, otherwise wearing gloves is an alternative.  If a filter drops the floor it should be replaced (no five-second rule).
  4. Watch your patient. What are they touching during testing?  Did ‘Johnny’ enter the body box and place his mouth directly on the filter adaptor? If the patient touched it, it should be wiped down with a disinfecting wipe. If the item (adaptor, reusable mouthpiece) comes in mucus membrane contact, it should be sent for high-level disinfection (pasteurization, glutaraldehyde or ethylene oxide) ideally by your hospital’s centralized services department.
  5. Gel-out or hand washing. At the end of testing, thank your patient for the effort they gave then wash your hands, wiping down any items in the room. The wipe should have sufficient dampness to saturate the surface. Be certain to wear gloves when handling disinfecting wipes.

Patients with Active or Suspected Respiratory Infections 

Here the patient is likely infectious and you are more concerned about protecting yourself and subsequent patients. As an extra precaution, at my facility we try to place a barrier between the patient and the equipment when the risk of droplet contamination is high. The barrier can be an absorbent pad or plastic with a hole cut in it to accommodate the flow sensor or adaptor.  Additionally, testing in a room with negative airflow ventilation or HEPA filtration is best; sadly this is luxury few clinics or physician offices enjoy. Remember the door should be closed to ensure effective exhaust of airborne particulate when rooms are engineered for respiratory isolation or designated AIIR.

Sick Staff

Allowing staff with obvious upper respiratory infections to test patients is not advised. Your patients certainly don’t want to catch a cold from the technologist by having them touch or cough on something. A respiratory infection on top of an already immunocompromised patient or one with a chronic lung disease can be deadly. Additionally, you do not want one staff member to infect another, in which case your lab will be short two technologists.

Understandably there may be times when you have the beginning symptoms of a cold, but remain undiagnosed. In this circumstance you should wear a N95 mask and gloves during testing. Influenza, however, is more serious. All staff suffering the flu should not be at work until they are free of fever for 24 hours and off fever-reducing medications.

Preanalytical Errors 

The wrong height, date of birth, gender can all lead to significant errors in percent predicted. Granted the spirometry data is still may be valid and reliable, but the clinician is most likely looking at percent predicted or hopefully lower limit of normal.

Regardless, entering incorrect patient demographics is a problem and can result in misinterpretation of spirometric data. It is important for technologists to check their work prior to sending the data to the interpretation step. If an observant physician does not catch the error, the patient can end up with x-rays, CT scans, or another unneeded diagnostic test.

Gender and Physical Attributes

Remember, if a woman is tested but the gender entry is mistakenly input as male, her spirometry percent predicted values will likely be low. On the other hand, if a man is tested but input as female, his spirometry values might look fantastic. Manufacturers would be wise to develop software to alert the technician to a possible gender entry error when gender-common first names are mislaeled. Alternatively if it is an option, the HL7 interface might also import the gender along with the date of birth.

Patients commonly overestimate height and although a half an inch one way or the other may not alter the outcome too much, it is always best to obtain a current height, without shoes using a stadiometer. Certainly if it is an adult patient coming for spirometry testing every three months, his height likely will not change and rechecking the measure might be deferred. Children, on the other hand, should be routinely measured for height between visits.

Calibration (No Calibration or Bad Calibration)

Entering the correct ambient conditions (temperature of testing environment and barometric pressure) prior to calibration is important. Calibration of pneumotachs is standard operating procedure for quality pulmonary labs, however in the clinic setting, occasional users might forget to calibrate or just blow by the alert to calibrate.

Additionally, if training is minimal, the person performing the syringe injections might not inject or withdraw fully, which will introduce error. Staff that slam the syringe in and out are often rushed or frustrated—this can also introduce error if the syringe is damaged or the volume stop moves from the setpoint. Syringes should operate smoothly, be assessed regularly, or sent to the manufacturer for recertification, as needed.

Signal Drift or Zero Issues

Occasionally drift can be introduced prior to the spirometry maneuver from air currents or simply the position of the flow sensor. Depending on the direction of the drift, this can result in a significant increase in the FVC and resultant decrease in the FEV1/FVC ratio, compared to maneuvers without drift. Staff performing spirometry should be trained to pick up the subtleties of identifying signal drift like a drifting baseline. See Figure 1 (arrow indicates drift in signal).

Bronchospasm During Forced Spirometry Testing

Although not common, patients can develop bronchospasm during sequential forced expiratory maneuvers. These individuals might start out with normal or mild airflow limitation and each forceful maneuver results in a slight decrease in the peak expiratory flow and FEV1.

At first you might suspect poor effort, but remain open to this possible presentation and be ready to administer a rescue inhaler if indicated.

Misinterpretation of Spirometry Data

Depending on a clinicians’ prior training or experience interpreting spirometry data, the assessments can be incorrect leading to additional testing. Occasionally, staff simply don’t know how the spirometry maneuver is being coached. For example, medical personnel are minimally-trained on coaching spirometry. They may not emphasize a fast and full inspiratory maneuver at the end of expiration, and only a partial inspiratory maneuver is displayed. The clinician reviewing the data and inspiratory curve might label the slow or incomplete inspiration as possible vocal cord dysfunction, leading to a referral to an ear, nose and throat specialist, when in fact it was how the maneuver was coached, not necessarily pathology. Offer in-services to clinicians or ask your medical director for assistance when you suspect problems.

Training New Staff on Spirometry

We often take the skill at performing spirometry for granted. Although basic training on how to perform spirometry is often instructed over a few hours, most participants focus on “How many maneuvers do I have to perform and which buttons do I push again?” When we mention acceptability, repeatability, usable maneuvers, back extrapolation volume, and time to peak flow, their eyes start to glaze over. Although medical assistants and others can be trained to perform spirometry, frequent review of results is warranted to ensure quality and aid in error recognition. It is not unreasonable to expect limited reimbursement by insurers, if documented competency performing this diagnostic is not available.


Matthew J. O’Brien, MS, RRT, RPFT, is the manager of the Pulmonary Diagnostic Lab at the University of Wisconsin Hospital and Clinics in Madison. For further information, contact [email protected].


  1. Hankinson JL, et al. Spirometric reference values from a sample of the general U.S. population. Am J Respir Crit Care Med. 1999;159: 179-87.
  2. Ferguson GT, et al. Office spirometry for lung health assessment in adults: a consensus statement from the National Lung Health Education Program. Chest 2000; 117(4): 1146-61.
  3. Miller MR, et al. Standardization of spirometry. Eur Respir J 2005; 26: 319-338.