Chronic obstructive pulmonary disease (COPD) is one of the most frequent reasons for inpatient admission. The nuances of the diagnosis, documentation, and coding of COPD and related conditions are numerous and important. Getting it right is crucial for correct documentation and coding that accurately reflect the severity of illness impacting quality and reimbursement.
COPD is characterized primarily by airflow limitation caused by variable combinations of obstructive bronchiolitis and/or emphysema. Emphysema represents permanent enlargement of alveoli and destruction of alveolar walls. Obstructive bronchiolitis is chronic inflammation of the bronchioles with damage to and narrowing of the bronchiolar walls.
COPD is diagnosed by pulmonary function testing (primarily spirometry). The key measure indicating COPD is a ratio of one-second forced expiratory volume (FEV1) to forced vital capacity (FVC) less than 0.7, or below the fifth percentile of the reference range. In addition, the diffusing capacity of carbon dioxide (DLCO) is an indicator of the severity of emphysema.
Other diagnostic findings may include variable degrees of hypoxemia and/or hypercapnia. Hypoxemia is defined as a partial pressure of oxygen (PaO2) less than 80 mm Hg on room air, which is equivalent to an oxygen saturation (SaO2) less than 95%. A partial pressure of carbon dioxide (PaCO2) greater than 45 mm Hg represents hypercapnia.
Chest X-ray has low sensitivity for diagnosing COPD (only about 50% of patients with moderate COPD can be identified by this method), and it is used primarily to exclude alternative diagnoses or to identify complications of COPD. CT scanning is not necessary for routine diagnosis of COPD but is used to evaluate complications and alternative diagnoses.
Three other conditions are frequently associated with COPD: chronic obstructive asthma, chronic bronchitis, and chronic respiratory failure. Chronic inflammation of bronchioles in COPD produces airway hyperresponsiveness, causing obstructive asthma with wheezing, shortness of breath, and cough, which is only partially reversible with treatment. Chronic bronchitis represents chronic inflammation of bronchi and is defined by chronic productive cough for three months or more in each of two successive years when other causes of chronic cough have been ruled out.
Chronic respiratory failure may be hypoxemic, hypercapnic, or a combination of both. Chronic hypoxemic respiratory failure is characterized by a PaO2 less than 60 mm Hg (equivalent to an SaO2 less than 91%) on room air, for which chronic home oxygen therapy is indicated. A chronic elevation of PaCO2 greater than 50 mm Hg represents chronic hypercapnic respiratory failure; the pH will be normal when chronic but a pH less than 7.35 indicates an acute decompensation.
COPD may also result in pulmonary hypertension due to chronic hypoxic pulmonary vasoconstriction together with destruction of the pulmonary capillary bed. Pulmonary hypertension is defined by a mean pulmonary artery pressure greater than 25 mm Hg. Many patients with pulmonary hypertension due to COPD have chronic cor pulmonale, which commonly becomes acute with an exacerbation of their COPD.
Many patients with COPD also have coexisting heart failure, which shares many of the same symptoms such as shortness of breath, dyspnea on exertion, hypoxemia, even wheezing—especially when there is an acute decompensation. A common clinical conundrum in these patients is distinguishing decompensated heart failure from an acute exacerbation of COPD, and both may be present as worsening of one often aggravates the other.
Patients with COPD are highly susceptible to acute bronchitis and pneumonia, both community-acquired and health care-associated. Pneumonia typically produces an acute exacerbation of COPD, but sometimes it may be difficult to distinguish between pneumonia and an acute exacerbation when the chest X-ray is inconclusive.
In summary, the diagnostic nuances of COPD are complex and crucial for correct documentation, management, and coding of COPD and related conditions. COPD is characterized by variable degrees of emphysema and obstructive bronchiolitis and is defined by the FEV1/FVC ratio measured by spirometry.
Most patients with COPD who experience sudden or progressive worsening of respiratory symptoms have an acute exacerbation or decompensation of COPD but commonly have other comorbid conditions as well, such as decompensated heart failure, chronic respiratory failure, pneumonia, and acute and/or chronic bronchitis—most of which also tend to aggravate COPD.
Next month's column will explore the documentation and coding challenges that determine severity of illness with COPD and affect quality metrics and revenue.