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Introduction ⬇

Forced vital capacity (FVC) is the maximum amount of air that can be exhaled forcibly and completely after a maximal inspiration. The forced expiratory volumes exhaled within 1, 2, or 3 seconds are referred to as timed vital capacities (FEV1, FEV2, and FEV3, respectively), whereas the FEF25–75 is the flow of air during the middle 50% (0.50) of the forced volume. These measurements are useful for evaluating a patient’s response to bronchodilators. Generally, if the FEV1 is <80% (<0.80) of predicted (reference value) or the FEF25–75 is <60% (<0.60) of predicted, bronchodilators (e.g., albuterol) are administered with a handheld nebulizer, and the spirometry is repeated. Studies have shown a better bronchodilator response with combined drugs (e.g., albuterol plus ipratropium) than either alone. An increase in these values of 20% or more (>0.20) above the prebronchodilator level suggests a significant response to the bronchodilator and is consistent with a diagnosis of reversible obstructive airway disease (e.g., asthma). Persons with emphysema typically do not demonstrate this type of response to bronchodilator. Measured (actual) spirometry values are compared with predicted values by means of regression equations using age, height, weight, ethnicity, and gender and are expressed as a percentage of the predicted value. Typically, a value >80% (>0.80) of predicted is considered within normal limits.

Procedure ⬆ ⬇

  1. Have the patient either sit or stand. Place nose clips on the nose and instruct the patient to breathe normally through a mouthpiece/filter (bacterial/viral) combination into the spirometer.

  2. Ask the patient to take a maximal inspiration and then forcibly and completely exhale into the spirometer.

  3. Have the patient repeat this maneuver a minimum of three times. The two best tracings should compare within ±200 mL of one another, or additional forced expiratory efforts will be needed.

  4. Administer bronchodilators with a handheld nebulizer and repeat spirometry if indicated.

  5. See Chapter 1 guidelines for intratest care.

Procedural Alert

  1. Before testing, assess the patient’s ability to comply with breathing requirements.

  2. The patient may experience lightheadedness, shortness of breath, or other slight discomforts. These symptoms are generally transitory. An appropriate rest period is usually all that is needed.

  3. If symptoms persist, testing is terminated.

  4. Rarely, momentary loss of consciousness (caused by anoxia during forced expiration) may occur.

  5. Follow established protocols for testing under these circumstances.

  6. Assess for contraindications such as pain or altered mental status.

Clinical Implications ⬆ ⬇

  1. With obstructive ventilatory impairments such as asthma, airway collapse occurs during the forced expiratory effort. This leads to decreases in airway flow rates and also, in the more severe forms, to apparent loss of volumes. Obstructive ventilatory impairments include the following:

    1. Emphysema

    2. Bronchitis

    3. Asthma

    4. Cystic fibrosis (CF)

    5. Byssinosis (rare lung disease caused by exposure to cotton dust)

  2. With restrictive ventilatory impairments, the FVC is reduced; however, flow rates can be normal or elevated. Restrictive ventilatory impairments include the following:

    1. Pulmonary fibrosis

    2. Lung resection

    3. Thoracic cage deformities (e.g., pectus excavatum, kyphoscoliosis)

    4. Asbestosis (exposure to the asbestos fiber)

    5. Silicosis (exposure to crystalline silica dust)

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain the purpose and procedure of the spirometry test. Explain that the patient will be asked to perform a maximal forced inspiration in addition to the forced expirations.

  2. Remind the patient that a light meal may be eaten before the test. However, no caffeine should be taken before testing. Specific instructions will be given regarding the use of bronchodilators or inhaler medications before the test.

  3. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Evaluate for dizziness, shortness of breath, or chest discomfort. Usually, these symptoms are transitory and subside after a short rest. If symptoms persist, use established follow-up protocols.

  2. Review test results; report and record findings. Modify the nursing care plan as needed.

  3. Counsel regarding possible further testing and treatment.

  4. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆ ⬇

  1. Bronchodilators (e.g., albuterol) should be withheld for at least 4 hours if tolerated.

  2. Respiratory infections may decrease airflow during the maneuver.

  3. Patient noncompliance can adversely affect the results because this test is effort-dependent.

Reference Values ⬆

Normal