Reach Full Capacity of Pulmonary Function Test Coding
When coding tests for lung disease, it helps to understand the underlying disease process.
Pulmonary function tests are performed during the non-acute phase of pulmonary disease. They measure a patient’s lung volumes, capacities, flow rates, airway resistance, and compliance. To help you apply pulmonary testing codes appropriately, let’s review pulmonary diseases, types of pulmonary functions tests and when they are used, which codes report the services, and tips for code selection.
Pulmonary Disease Is Obstructive, Restrictive, or Combined
There are two types of pulmonary diseases: obstructive and restrictive. Obstructive diseases are considered ventilatory diseases that affect the airways. Restrictive diseases impair oxygenation: these include thoracic deformities and diseases that affect alveolar lung tissue (parenchyma). Each type of pulmonary disease follows a specific pathophysiologic pattern. Patients with characteristics of both obstructive and restrictive diseases are diagnosed with a combined disorder.
Obstructive disease pattern:
- Increased airway resistance
- Decreased airway flow
- Increased lung volumes and capacities
- Increased lung compliance
- Increased dead space (pan lobular emphysema)
Restrictive disease pattern:
- Decreased pulmonary compliance
- Decreased lung volumes and capacities
- Impaired oxygenation (aka shunting) – Patients will diffuse less than 79 percent of alveolar oxygen due to a diffusion block, such as fluid or a decrease in alveolar oxygen volume.
Pulmonary function testing is a diagnostic tool used to confirm the presence of disease. The test measures the patient’s pulmonary parameters, allowing the physician to establish the patient’s pulmonary disease pattern and degree of impairment.
Types of Pulmonary Function Tests
There are two primary types of pulmonary function tests:
- Pulmonary Screening: Sometimes referred to as screening spirometry (CPT® 94010 or 94060), this procedure measures pulmonary flows. It is performed in a physician’s office to determine the presence of disease, and is also used for in-hospital, pre-general anesthesia evaluation of pulmonary status. A pulmonary screening includes a forced vital capacity (FVC) spirogram (see Graph A), or a similar procedure known as a flow volume loop (see Graph B). Both tests provide the same information; however, the flow volume loop provides inspiratory data that the FVC spirogram does not.
- Complete Pulmonary Function Test: Complete pulmonary function tests are used to measure lung volumes, capacities, airway resistance, and diffusion, as shown in Graph C. A screening spirometry is part of every complete pulmonary function test (CPT® 94726 or 94727).
See the sidebar Pulmonary Lung Volumes Defined, below, for an explanation of the terminology used in PFTs.
Common Pulmonary Testing Codes
The following CPT® codes are those associated with the most common adult pulmonary function tests:
94010 Spirometry, including graphic record, total and timed vital capacity, expiratory flow rate measurement(s), with or without maximal voluntary ventilation. This code reports screening spirometry without post bronchodilator study: Do not report it with codes 94150, 94200, 94375, or 94728.
94060 Bronchodilation responsiveness, spirometry as in 94010, pre- and post-bronchodilator administration. This code reports screening spirometry with post bronchodilator study: Do not report it with codes 94150, 94200, 94375, 94640, or 94728.
94200 Maximum breathing capacity, maximal voluntary ventilation. This test is included in both 94010 and 94060 but is rarely performed.
94375 Respiratory flow volume loop is included in codes 94010, 94060, or 94728.
94726 Plethysmography for determination of lung volumes and, when performed, airway resistance. This pulmonary function test uses a body plethysmograph to check airway resistance, while measuring all volumes and capacities, including total lung capacity. Do not report with 94727 or 94728.
94727 Gas dilution or washout for determination of lung volumes and, when performed, distribution of ventilation and closing volumes. This is for measuring lung volumes, functional residual capacity, and calculated total lung capacity through nitrogen washout or helium dilution (excludes airway resistance). It includes distribution of ventilation and closing volumes, when performed. Do not report this code with 94726.
94728 Airway resistance by impulse oscillometry. Use this code to report impulse oscillometry to assess airway resistance. This code is rarely used. Do not report it with 94010, 94060, 94070, 94375, or 94726.
+94729 Diffusing capacity (eg, carbon monoxide, membrane) (List separately in addition to code for primary procedure) is commonly performed in conjunction with lung volume and spirometry. It’s an add-on code used with 94726, 94728, 94010, 94060, 94070, and 94375.
94750 Pulmonary compliance study (eg, plethysmography, volume and pressure measurements requires a separate physician order.
Codes 94010 and 94060 are reported separately, but in addition to either 94726 or 94727 when a complete pulmonary function test is performed.
Tips for Code Selection
Be aware of the type of pulmonary function test performed on the patient. Airway resistance and compliance measurements may vary by testing site. This is what differentiates code 94726 from 94727. Testing facilities that incorporate the use of a body plethysmograph to perform complete pulmonary function tests are able to provide precise measurements of airway resistance and compliance (see 94726 and 94750). Facilities that do not employ the use of a body plethysmograph will perform complete pulmonary function tests; however, airway resistance and compliance will not be measured or reported (see 94727).
Pulmonary function tests that reveal the presence of obstructive disease require the administration of a bronchodilator, followed by a repeat of the same test (94010 vs. 94060). The post-bronchodilator study allows the physician to evaluate the patient’s response to a bronchodilator. If the values show an improvement in expiratory flow rates, the patient is placed on an obstructive disease treatment regimen. When spirometry values show an improvement of 12 percent or more in expiratory flows and volume, this is considered a “reversible” airway obstruction. Reversibility is not a cure: it is a favorable response to the administration of a bronchodilator (an improvement) seen in patients who have asthma. Chronic obstructive pulmonary disease (COPD) is not reversible.
A patient who undergoes screening spirometer with normal or restrictive results is not a candidate for a post-bronchodilator test. If the patient results reveal an obstructive disorder or combined disorder, then a post-bronchodilator study is indicated.
Diffusion capacity for carbon monoxide (DLCO), code +94729, is used to establish diffusion impairment that commonly occurs with the majority of restrictive diseases, as well as the presence of panlobular emphysema — the only obstructive disease that impairs diffusion. DCLO is most commonly performed with lung volumes or spirometry and is an add-on code used with 94010, 94060, 94070, 94375, 94726-94728).
Spirometry (94010) is the basis for pulmonary function testing. When it is performed before and after the administration of a bronchodilator, report 94060. A flow volume loop (94375) is included in codes 94010 and 94060. Code 94010 is not included in codes 94726 and 94727; they are reported separately.
Evaluating Pulmonary Function Test Results
Normal pulmonary function values are based on the patient’s age, weight, height, sex, and race. In pulmonary medicine, normal pulmonary values are termed “predicted values.” Actual values refer to the measurements obtained from the patient.
Pulmonary function test results are evaluated based on what percent of the predicted (normal) value is measured on the patient:
- Measured Value / Predicted Value = % Predicted
- Predicted values of 80-100 percent are considered normal.
- Predicted values of 60-79 percent are considered a mild impairment.
- Predicted values of 40-59 percent are considered a moderate impairment.
- Predicted values of 39 percent or less are considered a severe impairment.
Establishing Presence of Disease
By using the percent predicted values obtained from pulmonary function testing and applying those to the disease patterns, an initial diagnosis of the disease type is established. Consider the following clinical scenarios for coding:
- Lung volumes and capacities between 80-100 percent of predicted value. Flows (94010) and DLCO (+94729) are also within normal values. These results reveal a patient with normal lungs. Airway resistance and compliance were not reported. Report 94727 for the volume and capacity measurements.
- Lung volumes and capacities above 100 percent of predicted values with flows and DLCO (+94729) below normal. These results reveal obstructive disease. Airway resistance and compliance were not reported. CPT® 94727 reports the volume and capacity measurements. A post bronchodilator study (94060) is indicated and reported for this patient.
- Lung volumes and capacities below 79 percent of predicted values, DLCO (+94729) below normal, and flows (94010) are within 80-100 percent of predicted value. These results reveal restrictive disease. Airway resistance and compliance were not reported. Report 94727 for the volume and capacity measurements.
- Lung volumes and capacities below 79 percent of predicted values. Flows and DLCO (+94729) are also below normal. These test results reveal a combined disorder. Airway resistance and compliance were not reported. Report 94727 for the volume and capacity measurements. A post bronchodilator study (94060) is indicated and reported for this patient due to the obstructive component of the combined disorder.
- Lung volumes and capacities above 100 percent of predicted values. Flow rates and DLCO (+94729) below normal. Lung compliance and airway resistance are above normal. This test was performed using a body plethysmograph and reveals an obstructive disease. Report 94726 for the volume, capacity, airway resistance. If indicated with a separate physician order, you may separately report compliance measurements (94750). As previously indicated, if compliance is reported without a specific order for a compliance study, it is included in 94726. A post bronchodilator study (94060) is indicated and reported for this patient.
- Lung volumes and capacities below 79 percent of predicted values. Flow rates (94010) at 80-100 percent of predicted. DLCO (+94729) below normal. Lung compliance below normal. Normal airway resistance. This test reveals a restrictive disease. The test was performed using a body plethysmograph. Report 94726 for the volume, capacity, airway resistance, and compliance measurements (you may report 94750 separately for a compliance study only if there is a separate physician order for the test).
- Lung volumes and capacities below 79 percent of predicted values. Flows and DLCO (+94729) are below normal. Lung compliance is below normal and airway resistance is above normal. This test reveals a patient with a combined disorder. This test was performed using a body plethysmograph. Report 94726 for the volume, capacity, airway resistance, and compliance measurements (you may report 94750 separately for a compliance study only if there is a separate physician order for the test). A post bronchodilator study (94060) is indicated and reported for this patient.
Pulmonary Lung Volumes Defined
Tidal volume (VT): The volume of air for every normal breath.
Inspiratory reserve volume (IRV): The maximal amount of additional air that can be drawn into the lungs after a normal inspiration.
Expiratory reserve volume (ERV): The additional amount of air that can be expired from the lungs after a normal expiration.
Residual volume (RV): The volume of air that remains in the lungs after a maximal exhalation. RV is present to prevent alveolar collapse.
Pulmonary lung capacities include:
Total lung capacity (TLC) = IRV + TV + ERV + RV (the sum of all the lung volumes). TLC reveals the total air capacity of the patient’s lungs. Above normal TLCs are indicative of air trapping. It’s important to understand that TLC has a limit, governed by the rib cage.
Vital capacity (VC) = TV + IRV + ERV. VC is achieved by instructing a patient to take in the deepest breath possible followed by a maximal expiration. There are two types of VCs: slow vital capacity (SVC) and forced vital capacity (FVC). FVC is achieved by instructing the patient to exhale as much air out of their lungs as fast as they can. The FVC will reveal the fastest expiratory flow rate the patient can achieve.
Functional residual capacity (FRC) = ERV + RV. FRC is the volume of air left in the lungs after a normal expiration.
Inspiratory capacity (IC) = TV + IRV. IC is the maximum volume of air that can be inhaled after a normal expiration.
For information on COPD, read the article “Recognize Clinical Indicators to Improve Pulmonary Disease Coding” in AAPC’s Knowledge Center and on pages 28-30 of the November 2018 Healthcare Business Monthly magazine.
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