Total lung capacity (TLC) measures the volume of gas contained in the lungs at the end of a maximal inspiration. It is used mainly to evaluate obstructive defects and to differentiate restrictive from obstructive pulmonary disease. Mathematically, it is the sum of the VC and the RV, or the sum of the primary lung volumes (see Figure 14.1). This value is calculated indirectly from other tests.
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.
Ask the patient to inspire maximally and exhale maximally. The total amount of air exhaled is the VC.
Use the following formula to derive the TLC mathematically:
Increased values are associated with:
Emphysema
CF
Hyperinflation
Decreased values are associated with:
Pulmonary edema
Atelectasis
Neoplasms
Pulmonary congestion
Pneumothorax
Thoracic restriction
Pretest Patient Care
Explain the purpose and procedure of the test. Even though it is noninvasive, it does require patient effort and cooperation.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.