Chronic obstructive pulmonary disease (COPD) is one of the most frequent reasons for inpatient admission, and the nuances of the diagnosis, documentation, and coding of the disorder and related conditions are numerous. Last month's column dealt with recognition and diagnosis. This month's focuses on how to accurately reflect the severity of illness of patients with COPD, which can have a substantial impact on quality metrics and revenue.
First, the acuity of COPD must be specified: Always document whether or not there is an acute exacerbation or decompensation. It doesn't matter that there may be only a mild exacerbation; any acute change of mild degree is still significant. An acute exacerbation is recognized by worsening of symptoms, like shortness of breath and cough, associated with findings such as tachypnea and wheezing. It is commonly precipitated by another condition like acute bronchitis, pneumonia, or heart failure. A point to remember is that Medicare's diagnosis-related group (DRG) system assigns the same degree of severity to a diagnosis of COPD with documentation of “acute bronchitis” as to an acute exacerbation of COPD.
Assessing severity also includes consideration of the possibility of coexisting chronic respiratory failure, which is characterized by variable degrees of hypoxemia and/or an elevated partial pressure of carbon dioxide (PaCO2). Keep in mind that any patient requiring continuous supplemental home oxygen has significant chronic hypoxemic respiratory failure, which should be documented. Many other patients have chronic hypercapnic respiratory failure with hypoxemia not severe enough to warrant home oxygen; these patients also need to be specifically identified as having chronic respiratory failure. Some patients will have a combination of chronic hypoxemic and hypercapnic respiratory failure.
Acute respiratory failure (with or without preexisting chronic respiratory failure) is very commonly associated with acute exacerbations of COPD and related conditions or complications. Some clinicians prefer to describe patients with preexisting chronic respiratory failure as having “decompensated” or “exacerbated” rather than “acute” respiratory failure, especially when mild, and this is perfectly acceptable for coding purposes. Acute respiratory failure is also classified as hypoxemic, hypercapnic, or both.
Acute hypoxemic respiratory failure is defined as a partial pressure of oxygen (PaO2) less than 60 mm Hg, which is equivalent to oxygen saturation (SaO2) of 91% on room air, or a PaO2/FiO2 ratio less than 300 (where FiO2 is the fraction of inspired oxygen expressed as a decimal). For patients who require home oxygen, these criteria cannot be used, but a PaO2 less than 60 mm Hg (SaO2 <91%), measured not on room air but on the patient's usual home oxygen flow rate or higher, is a valid indicator of an acute decompensation of chronic respiratory failure.
Acute hypercapnic respiratory failure is identified by a PaCO2 greater than 50 mm Hg and a pH less than 7.35. This is sometimes described as respiratory acidosis, but this term does not properly describe the severity of illness associated with acute respiratory failure. The low pH indicates there has been an acute retention of carbon dioxide (converted to carbonic acid in solution). A normal pH with elevated PaCO2 indicates that respiratory failure is chronic (not acute) due to neutralization of carbonic acid by the renal compensatory increase in bicarbonate that occurs with baseline stable chronic respiratory failure.
Right now there is no ICD-10-CM code for acute cor pulmonale due to COPD or any other condition except pulmonary embolism. It is hoped that this situation will soon be remedied, and if it is, recognizing and documenting an acute decompensation of chronic cor pulmonale due to COPD or another condition will become very important. An astute clinician can often recognize acute cor pulmonale based on physical examination and clinical circumstances without having to order a Doppler echocardiogram.
Commonly, patients with COPD and chronic heart failure present with symptoms that may be due to either or often both. Heart failure should always be clarified in the record as systolic or diastolic based on ejection fraction (EF): Systolic heart failure is denoted by an EF below 55%, while diastolic is denoted by an EF equal to or greater than 55%. If there is any evidence of decompensated heart failure, even if only mild, it should also be clearly described as an acute exacerbation or decompensation to accurately represent its severity. Some indicators of decompensation include: a B-type natriuretic peptide (BNP) level greater than 500 pg/ml, an NT-pro-BNP level greater than 3,500 ng/ml, new or increasing pleural effusion, new or increasing pretibial edema, or bilateral fine wet rales.
The code assignment currently required by ICD-10-CM in cases of pneumonia with COPD (whether acutely exacerbated or not) makes little clinical sense. ICD-10-CM contains a code titled “COPD with acute lower respiratory infection” (code J44.0), and coding guidelines indicate that pneumonia is a lower respiratory tract infection. However, the coding instructions require code J44.0 be sequenced before the pneumonia code, making COPD the principal diagnosis even when the patient is admitted primarily for pneumonia even with no acute exacerbation of COPD. This rule assumes that pneumonia is always a manifestation of COPD. Even if the patient has culture-positive bacterial pneumonia caused by, for example, Pseudomonas or Staphylococcus species, the principal diagnosis will be COPD and it will be assigned to a COPD DRG instead of one for pneumonia.
Oddly, aspiration pneumonia is not classified by ICD-10-CM as an infection, unless specifically documented as bacterial or viral, but rather as pneumonitis due to inhalation of food and vomitus. Therefore, the code J44.0 instruction would not apply. It's crucial to identify and document suspected aspiration in circumstances that suggest it.
In summary, many important documentation and coding considerations for COPD and its related conditions have a substantial impact on severity classification, quality metrics, and revenue: acute exacerbation or decompensation of COPD; chronic respiratory failure; acute (or acute-on-chronic) respiratory failure; coexisting systolic or diastolic heart failure, including both chronic and acute exacerbations or decompensation (even if mild); and coexisting pneumonia, especially if aspiration is likely the cause.