With average cost, length of stay and mortality rate comparisons so much a part of today's health care delivery system, it is important that a patient's diagnosis be recorded to the highest level of specificity. Hospitalists should always document the most severe form of the disease process that accurately explains the circumstance of an admission.
Exacerbation of chronic obstructive pulmonary disease (COPD) is among the top 10 reasons Medicare patients are hospitalized. In some of these cases, it may be appropriate to assign a principal or secondary diagnosis of acute respiratory failure.
The principal diagnosis is defined as “that condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care.” Acute respiratory failure is supported as a principal diagnosis when at least two of the following are met
- Respiratory failure, as defined by respiration >30 breaths/minute, central cyanosis and use of accessory muscles of respiration
- Po2 <60 mm Hg
- Pco2 >50 mm Hg
- pH <7.35
In a patient with COPD or other chronic lung disease, acute respiratory failure may be diagnosed by the degree of change from the patient's baseline. A 10- to 15-mm drop in Po2 and/or a significant increase in Pco2 coupled with a decrease in the pH supports the diagnosis, for example.
The following case study shows how a principal diagnosis of acute respiratory failure can affect documentation and payment.
A patient presents to the emergency department with an acute exacerbation of COPD. Arterial blood gas (ABG) test results are consistent with acute respiratory failure. The patient is admitted to the ICU and treated with steroids and O2 but does not require intubation and mechanical ventilation.
The hospitalist documents the diagnoses as acute exacerbation of COPD with severe hypoxemia.
This documentation is coded to MS-DRG 192: COPD without Complication or Comorbidity. The payment is $3,946, at a hospital-specific rate of $5,500. Geometric mean length of stay is 3.3 days.
If the circumstances and ABG measurements support it, however, the hospitalist can document acute respiratory failure, which yields a longer expected length of stay and a higher payment. The diagnoses can then be documented as
- 1. Acute respiratory failure due to
- 2. Acute exacerbation of COPD.
This documentation is coded to MS-DRG 189: Respiratory Failure. The payment is $7,400, and the geometric mean length of stay is 4.7 days.
In some cases, acute respiratory failure may be listed as a secondary diagnosis if it occurs after admission, or if it is present on admission but does not meet the definition of principal diagnosis.
Complications and comorbidities
Of the total number of 2009 Medicare claims assigned to the MS-DRGs for COPD and acute respiratory failure, 27% were in DRG 189—that is, acute respiratory failure as the principal diagnosis. The remaining 73% of claims listed COPD as the principal diagnosis, and were divided into three categories based on the presence or absence of complications or comorbidities, as follows
MS-DRG 192: COPD without Complication or Comorbidity. Payment of $3,946, at a hospital-specific rate of $5,500. Geometric mean length of stay is 4.7 days.
MS-DRG 191: COPD with Complication or Comorbidity
Payment of $5,292, at a hospital-specific rate of $5,500. Geometric mean length of stay is 4.0 days.
MS-DRG 190: COPD with Major Complication or Comorbidity. Payment of $6,642, at a hospital-specific rate of $5,500. Geometric mean length of stay is 3.2 days.
COPD has significant extrapulmonary (systemic) effects that lead to comorbid conditions. Data from the Netherlands from the 2008 Global Initiative for Chronic Obstructive Lung Disease (GOLD) show that up to 25% of the country's COPD population 65 years and older suffer from two comorbid conditions; up to 17% suffer from three.
According to US MEDPAR data for federal fiscal year 2009, complications and comorbidities most frequently coded on inpatient U.S. Medicare claims for patients whose principal diagnosis was COPD were: hyponatremia, cardiomyopathy, urinary tract infection, carcinoma of the lung, atelectasis, acidosis, chronic respiratory failure, and atrial fibrillation with flutter. While four stages of COPD severity have been defined in the medical literature, the ICD-9-CM classification system does not have codes that differentiate among these stages.
Chronic respiratory failure
For coding purposes, respiratory failure is classified in ICD-9-CM as acute (518.81), chronic (518.83) or acute and chronic combined (518.84).
COPD patients whose lung function is severely compromised and whose baseline arterial blood gases meet the definition of respiratory failure may also develop cor pulmonale (right heart failure). The long-term administration of oxygen (>15 hours per day) has been shown to increase survival for these patients, for whom hospitalists may include chronic respiratory failure as a secondary diagnosis. Doing so will establish the severity of illness, and affect the risk of mortality calculation that is used to evaluate clinical and financial outcomes.