ATS Pulmonary Function Laboratory Manual

chapter  6

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MVV

Step Action 3.

After three resting tidal breaths, instruct the patient to breathe as rapidly and deeply as possible. Tongue and teeth must be positioned so as to not obstruct airflow. 4. Enthusiastically coach the patient throughout the maneuver, and direct the patient to breathe faster or deeper to achieve an ideal rate of between 90 and 110 breaths per minute, though patients with dis- ease may not always be able to achieve this rate. Tidal volume during the maneuver is probably not as important as breathing frequency. 5. The test interval (e.g., 12 sec) should be noted and reported. 6. Perform a minimum of two acceptable maneuvers, and check for test repeatability.

Review of Test Results 1.

Individual spirometry maneuvers are “acceptable” if: 1.1. They are free from artifacts including:

• Cough or glottis closure during the first second of exhalation • Early termination or cutoff • Variable effort • Leak at the mouth

• Obstructed mouthpiece • Flow signal zeroing error

1.2. Have good starts with extrapolated volume less than 5% of FVC or 0.15 L, whichever is greater. For preschool children, the back extrapolation volume should be ≤ 80 ml or < 12.5% of the FVC (19). 1.3. Have a satisfactory exhalation with reasonable duration or a plateau in the volume–time curve. Rea- sonable duration is defined as follows: the patient has tried to exhale for at least 3 seconds in children < 10 years of age, and for at least 6 seconds for those over 10 years of age; however, many teenagers will reach a plateau before 6 seconds, so an earlier termination is acceptable if a plateau is demon- strated. A plateau is defined as no change in volume (< 0.025 L) for at least one second. Although patients should be encouraged to achieve maximal effort, they should be allowed to terminate the maneuver on their own at any time especially if they are experiencing discomfort. Note 1: For most adult patients exhalation times longer than 6 seconds are frequently needed. However, exhalation times greater than 15 sec will rarely change clinical decisions. Note 2: In children and young adults the end exhalation is normally determined by chest wall mechanics rather than by airway closure, so there may be a rapid drop in flow at the end exhalation simulating a cutoff. This pattern should not be misinterpreted as early termination. 1.4. A maneuver may be considered “usable” if it there is no cough or glottis closure in the first second and have a good start. 2. Between-maneuver repeatability criteria for spirometry (6): 2.1. After a minimum of three acceptable FVC maneuvers have been obtained: • The two largest FVC values are within 0.150 L of each other; if the FVC ≤ 1.00 L, repeatability is to be within 0.100 L. • The two largest FEV 1 values are within 0.150 L of each other; if the FVC ≤ 1.00 L, repeatability is to be within 0.100 L.

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