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Office Spirometry

David L. Nelson, MD, LAc and Dennis R. Wissing, PhD, RRT, CPFT, AE-C

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Subject: Office Spirometry

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Respiratory disorders such as chronic obstructive pulmonary disease (COPD), emphysema, chronic bronchitis, and asthma are major concerns for the primary care practitioner. Patients often present with a nonspecific cough and shortness of breath, requiring an assessment to determine cause. One simple tool for the practitioner to use to assess the patient’s pulmonary status is spirometry. Office or bedside spirometry is a test to determine how much air an individual can blow out and how fast. Spirometry measurements allow the primary care practitioner to determine if the patient has obstructive or restrictive disease or a combination of both during an office visit. 
Spirometry measures four numeric values that are useful in assessing the patient: 
  • Forced vital capacity (FVC) is the total amount of air that can be exhaled following a maximal inspiration. The FVC is reported in liters.

  • Forced expired volume in 1 second (FEV 1.0) measures the expired volume during the first second of an FVC maneuver. FEV 1.0 is reported in liters.

  • The ratio (FEV 1.0/FVC) is the percentage of the FEV 1.0 compared to the FVC.

  • Peak expiratory flow (PEF) is a measurement of how fast a patient can blow out during expiration following a maximal inspiration. The PEF is reported in liters per minute.


  • Handheld or desktop portable spirometer

  • Disposable pneumotach (mouthpiece)

  • Calibration syringe (3 L)

  • Printer for hard copy of spirometry results

  • Nose clips

Indications for Spirometry

  • Assess severity of COPD.

  • Determine existence of lung disease with patients who smoke.

  • Diagnose and classify asthma.

  • Assess exercise tolerance.

  • Diagnose restrictive pulmonary disorders.

  • Assess response to bronchodilator.

  • Evaluate exposure to inhaled toxins/irritants in the workplace.

  • Evaluate for disability benefits.

  • Determine preoperative risk for pulmonary complications.

  • Monitor disease progression.


  • Inability to cooperate

  • Acute respiratory failure

  • Moderate to severe persistent asthma

The Procedure

Step 1

The operator should be familiar with the operation of the spirometer. Calibrate the spirometer with a 3-L syringe following the manufacturer’s recommendation. Measure and record the patient’s height while standing without shoes, and measure and record the patient’s weight. Enter the patient’s height, weight, age, race, and other data (e.g., smoking history, level of dyspnea) into the spirometer’s software program as prompted. Instruct the patient to sit straight in a chair with feet on floor, remove dentures, and loosen any restrictive clothing. Explain why the test is being administered and how the test is to be performed. Demonstrate the procedure using a pneumotach or mouthpiece. 
  • PITFALL: Spirometry should not be performed if the patient has smoked within 4 hours. Smoking can result in acute small airway constriction.

Step 2

Apply nose clips. Have the patient place the pneumotach in his or her mouth while maintaining a tight seal with the lips, and assess for leaks. Instruct the patient to breathe normally to acclimate the patient to the procedure and equipment. After several tidal breaths, and at an end-exhalation as noted on the spirometer screen, have the patient take in the deepest breath possible. Immediately following the full deep breath, have the patient blast out air as fast and hard as possible. Continue to have the patient exhale for a minimum of 6 seconds—the volume-time graph should level off. 

Step 3

Encourage longer exhalation if the volume-time graph continues to ascend after 6 seconds. After full expiration, instruct the patient to take in a rapid inspiration to complete the flow-volume loop. Remove the pneumotach and nose clip, and have the patient breathe normally. The procedure is typically repeated two additional times for a total of three acceptable maneuvers. 
  • PITFALL: The accuracy of spirometry depends upon the coaching and correct instructions provided by the practitioner.

  • PITFALL: The procedure is repeated if the patient performs any of the three maneuvers poorly, so that three tracings with minimal variance in measurements are obtained. Eight attempts is the limit for any given spirometry session.

Step 4

Review the results and discuss the findings with the patient. If the patient performs <70% of predicted FEV 1.0, the clinician should consider having the patient perform a post-bronchodilator spirogram. Obtain a metered dose inhaler with a beta agonist (e.g., albuterol), and shake the canister to mix the drug and propellant. Attach a holding chamber or spacer to the metered-dose inhaler (MDI), and instruct the patient on proper use of the MDI. Administer four puffs of the beta agonist, wait 15 minutes, and then have the patient perform three spirogram measurements. The patient successfully responds to the inhaled bronchodilator if the FEV 1.0 increases by 12% or more (Table 19-1). 
Table 19-1.
Example of Pre- and Post-bronchodilator Spirometry Measurements from a 56-Year-Old White Female Who is 62 inches Tall and Weighs 133 pounds
  • Pearl: It is important that the practitioner records the patient’s height, age, gender, and race accurately. These factors affect lung function and are used to determine the patient’s predicted spirometry values. The spirometer’s software programs will compare the predicted measurements to the patient’s actual measured values. From this comparison, a diagnosis can be made.

  • PITFALL: Even when patient’s predicted spirometry values are computed, the normal range of actual spirometer measurements for healthy individuals can vary from 80 to 120%.

Normal volume-time graph

Normal volume-time graph

Normal flow-volume loop

Normal flow-volume loop

Step 5

Determine reliability of spirometry tracings and the repeatability of results. The variance between the largest and second largest force vital capacity should be <150 mL. The variance between the largest and second largest forced expiratory volume in 1 second (FEV 1.0) should be <150 mL. The practitioner should choose the better of the two most similar measurements or allow the spirometer’s software program to choose. Table 19-2 shows common reasons for inaccurate spirometry measurements. 
Table 19-2.
Reasons for Inaccurate Spirometry Measurements
  • Pearl: The patient should have exhaled at least 6 seconds, and longer if the volume-time graph continues to ascend after 6 seconds.

Flow-volume loop pattern with airway obstruction

Flow-volume loop pattern with airway obstruction

Step 6

Interpretation of the spirometry results. The following figures can assist with the interpretation of spirometry results. 

Flow-volume loop pattern with restrictive lung disease

Flow-volume loop pattern with restrictive lung disease

Step 7

Healthy individuals are able to perform a maximal inspiration followed with a maximal expiration. The FVC will be approximately 80% of their predicted values, and their FEV 1.0/FVC ratio will be at least 70%. Obstructive disease is typically diagnosed when these values drop to <80% and 70% of predicted results, respectively. With obstructive disease, there is a decrease in maximal flow rates, and the expiratory curve is scooped out or concave to the x-axis. With restrictive disease, flow rates may be increased while volumes are diminished. Table 19-3 summarizes the changes occurring with spirometry with obstructive and restrictive diseases or when the patient has a combination of both diseases. 
Table 19-3.
Classification of Pulmonary Abnormalities Based on Spirometry
  • Pearl: There is a good correlation between PEF and FEV 1.0 in asthma, which allows the practitioner to use PEFs to assess the patient with asthma. This correlation decreases with patients with COPD. Airway collapsibility as seen with COPD results in a varying relationship between PEF and FEV 1.0. PEF testing in COPD can be misleading. In addition, PEF does not detect small airway disease, which is common in COPD.

Flow-volume loop pattern with mixed disease pattern

Flow-volume loop pattern with mixed disease pattern


  • Small airway collapse from dynamic airway compression during forced vital capacity can occur in patients with COPD, asthma, emphysema, or chronic bronchitis. This may result in wheezing noted on auscultation.

  • Hyperventilation can occur if the patient is not instructed correctly.

  • Cross contamination results if the Pneumotach is used by multiple patients.

Pediatric Considerations

Children present a challenge to technicians performing spirometry. Careful instruction on correct posture and breathing are essential to performing reproducible test results. Encourage the child to relax as much as possible to prevent undue anxiety. 

Postprocedure Instructions

  • The patient may resume regular activities immediately.

  • Although some musculoskeletal pain is common, it should resolve with conservative treatment.

  • The patient should follow up with the referring provider.

Coding Information and Supply Sources

Equipment and supplies can be purchased through several vendors. Pricing varies widely. A brief Internet search for spirometry will yield a host of vendors. Here is a partial list. 


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