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Know the 'Ins and Outs' Of Respiratory Failure Coding

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Coding for respiratory failure remains one of the most challenging issues facing coders today. Part of the confusion lies with the fact that the underlying cause, if known, must be taken into consideration before assigning final codes for the case. A thorough understanding of the clinical terms and related conditions are also a must in mastering the classification of these patients, many of whom have multiple acute care visits and many inter-related clinical symptoms. In some cases, respiratory failure may be caused by a nonrespiratory related condition, making the classification of the disease even more confusing. Before taking one of the CCS exams, ensure that you understand all of the nuances of respiratory failure coding.

Respiratory failure is defined as the body's inability to perform the lung's basic function-gas exchange. Gas exchange-the transfer of oxygen of inhaled air into the blood and of waste carbon dioxide of blood into the lungs-is vital to survival. Respiratory failure can be a failure of oxygenation-the tissues of the lungs not functioning properly; or a failure of ventilation-an impairment of airflow in and out of the lungs. Or it may be a combination of the two.

When the process of gas exchange is faulty and there is not enough oxygen in the blood, this is called hypoxemia, which may be documented in the medical record. Sometimes there is also an abundance of carbon dioxide, which is called hypercapnia. Hypercapnia makes the blood more acidic, which is called acidemia. Whenever any of these terms-hypoxemia, hypercapnia or acidemia-are documented in the medical record, the coder should look for further documentation of respiratory failure.

Almost all lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis, AIDS-related pneumonia and other pneumonias and lung infections, may eventually progress or lead to respiratory failure if the diseases are inadequately controlled. Adult respiratory distress syndrome (ARDS), which is also known as acute respiratory distress syndrome, is a form of respiratory failure caused by extensive lung injury following various catastrophic events such as severe infection, shock and burns. This is the first type of respiratory failure for which we will discuss coding strategies later in this article.

Hypercapnic respiratory failure is due to a disease of the muscles used for breathing, which may also be referred to as "pump or ventilatory apparatus failure." Although the lungs of these patients are normal, there is a loss or decrease in neuromuscular function, inefficient breathing and limitation of the flow of air into the lungs. This is the second type of respiratory failure and occurs in patients with diseases such as myasthenia gravis, stroke, cerebral palsy, amyotrophic lateral sclerosis, muscular dystrophy, poliomyelitis, postoperative situations that limit the ability to take deep breaths, and in depressant drug overdoses.

Because the symptoms and clinical features of respiratory failure vary so widely in different patients, the most accurate diagnostic method is to measure the oxygen (PaO2) and carbon dioxide (PaCO2) in the arterial blood, using arterial blood gas (ABG) levels. The cut-off levels are somewhat arbitrary and vary with age, but PaO2 (oxygen) levels less than 60 mm Hg, PaCO2 (carbon dioxide) levels greater than 50 mm Hg or pH less than 7.30 generally mean that the patient is in respiratory failure. Keep in mind that "normal" levels vary by patient and that some COPD patients will have chronically abnormal ABG values, and the diagnosis of respiratory failure must be made on further decompensation from the patient's baseline levels. For coding purposes, a diagnosis of respiratory failure should never be made based upon lab findings only. The physician must substantiate the findings and make a diagnosis of respiratory failure, although the coder may reference the lab values while querying a physician for more information.

So once the diagnosis of respiratory failure has been made, how does the coder ensure that the sequence of codes is correct? The most straight-forward case involves respiratory failure in a patient for which the underlying cause is respiratory in nature. In that instance, the respiratory failure is sequenced as the principal diagnosis.

Unfortunately, when the underlying cause is non-respiratory in nature, the coding guidelines are not quite so clear. There are three fundamental coding guidelines related to respiratory failure sequencing when the diagnosis is related to a non-respiratory condition:

1. When a patient is admitted in respiratory failure due to or associated with an acute non-respiratory condition, the acute condition is sequenced as the principal diagnosis.

For example: A patient experienced a cerebrovascular thrombosis with infarction, and upon arrival at the ER was found to be in respiratory failure. The patient was placed on mechanical ventilation and admitted to the ICU for further care for the respiratory failure and management of the cerebrovascular thrombosis/infarction.

Principal diagnosis: 434.01 Cerebral thrombosis with infarction

Secondary diagnosis: 518.81 Respiratory failure

In this example, the acute cerebrovascular thrombosis required admission and is the principal diagnosis; the respiratory failure required immediate treatment but was a complication of the cerebral thrombosis.

2. When a patient is admitted with acute respiratory failure due to or associated with an acute exacerbation of a chronic non-respiratory condition, the acute condition is sequenced as the principal diagnosis.

For example: Following dietary indiscretion, a patient with compensated congestive heart failure (CHF) developed paroxysmal nocturnal dyspnea, orthopnea and pedal edema leading to increased respiratory distress. In the ER, the patient was found to be in cardiogenic pulmonary edema and respiratory failure and was subsequently intubated in the ER. The patient was admitted and treated for congestive failure.

Principal diagnosis: 428.0 Congestive heart failure

Secondary diagnosis: 518.81 Respiratory failure

The CHF had become acute and required immediate hospital care. The associated development of respiratory failure in this case is an additional complicating factor, but is not the condition that occasioned the admission and should not be sequenced as the principal diagnosis.

3. When a patient is admitted in respiratory failure due to or associated with a chronic non-respiratory condition, the respiratory failure is sequenced as the principal diagnosis.

For example: A patient with a diagnosis of myasthenia gravis, who was followed on an outpatient basis, was admitted in respiratory failure. Treatment was directed toward both the respiratory failure and the myasthenia gravis.

Principal diagnosis: 518.81 Respiratory failure

Secondary diagnosis: 358.0 Myasthenia gravis

This example illustrates a patient who has been treated on an outpatient basis for a chronic non-respiratory disease, myasthenia gravis. The condition that led to the admission was respiratory failure.

As the examples above illustrate, the coder must be diligent in reviewing documentation carefully to determine the exact circumstances of the respiratory failure. Physician queries may be required to determine the underlying cause and if documentation does not specify, whether it is a chronic or acute newly diagnosed condition. Although the presence of mechanical ventilation may indicate the presence of respiratory failure, coders should also be aware that not all respiratory cases require ventilation and the absence of ventilation documentation in the medical record does not preclude a diagnosis of respiratory failure.

Before the CCS exams, the coder may also want to review the following references:

1. Coding Clinic for ICD-9-CM:

Second Quarter 1991, "Sequencing of Respiratory Failure in Association with Nonrespiratory Conditions"

Third Quarter 1988, "Respiratory Failure"

2.ICD-9-CM Coding Handbook, by Faye Brown: Chapter 15: Diseases of the Respiratory System

3.Respiratory Failure (Educational Pamphlet), National Institutes of Health, Division of Lung Diseases

After reviewing all coding guidelines related to respiratory failure, test yourself with the exercises below:

1. The physician's diagnosis is "Acute respiratory failure due to acute bilateral interstitial pneumonia due to Mycoplasma organism." The discharge summary states, "Since we could not culture anything and since Legionella pneumonia was due to Eaton's agent, he was given erythromycin as part of his antibiotic program with final improvement in the pneumonia and hypoxia." The appropriate diagnosis code assignment is:

a. 483.0, 518.81

b. 136.3, 483.0, 518.81

c. 518.81, 483.0

d. 483.0, 136.3, 518.81

2. A patient is brought to the ER after an overdose of crack cocaine, is found to be in respiratory failure, is intubated, placed on mechanical ventilation and admitted. The appropriate diagnosis code assignment is:

a. 968.5, 305.60, 518.81

b. 518.81, 968.5, 305.60

c. 305.60, 968.5, 518.81

d. 304.20, 968.5, 518.81

3. A patient is seen and treated for acute respiratory failure secondary to metabisulfite allergy (Metabisulfite is a food preservative.) The appropriate diagnosis code assignment is:

a. 796.0, 866.8, 518.81

b. 995.2, E866.8, 518.81

c. 518.81, E866.8

d. 989.89, E866.8, 518.81

4. A patient is seen in the ER with chest pain and shortness of breath and was intubated. She was admitted and subsequently diagnosed as having an acute subendocardial myocardial infarction complicated by respiratory failure. The appropriate diagnosis code assignment is:

a. 518.81, 410.71

b. 410.71, 518.81

c. 410.91, 518.81

d. 786.50, 518.81, 410.71

5. A patient was admitted with a one-week history of progressive muscle weakness and respiratory difficulties. The patient was diagnosed as having acute respiratory failure and acute idiopathic polyneuritis (Guillain-Barre syndrome). The appropriate diagnosis code assignment is:

a. 357.0, 518.81

b. 518.81, 357.0

c. 728.9, 357.0, 518.81

d. 357.9, 518.81

6. A patient was admitted in respiratory failure after taking an unknown quantity of alcohol along with Elavil and Xanax. She was admitted and placed on mechanical ventilation. The appropriate diagnosis code assignment is:

a. 518.81, 969.0, E854.0

b. 969.8, E854.8, 518.81

c. 518.81, 969.0, 969.4, 980.0, E854.0, E853.2, E860.0

d. 969.0, 969.4, 980.0, 518.81, E854.0, E853.2, E860.0 n

This month's column has been prepared by Cheryl D'Amato, RHIT, CCS, director of HIM, and Melinda Stegman, MBA, CCS, manager of clinical HIM services, HSS Inc. (, which specializes in the development and use of software and e-commerce solutions for managing coding, reimbursement, compliance and denial management in the health care marketplace.

Coding Clinic is published quarterly by the American Hospital Association.

CPT is a registered trademark of the American Medical Association.


1. c: The record indicated that the reason for the admission was the acute respiratory failure, and the underlying contributing condition was respiratory in nature. Respiratory failure should be sequenced as the principal diagnosis (Coding Clinic, Nov/Dec 1987).

2. a: Refer to Coding Clinic, 2nd Quarter 1990, p. 11: "When coding a poisoning or reaction to the improper use of a medication (e.g., wrong dose, wrong substance, wrong route of administration), the poisoning code is sequenced first, followed by a code for the manifestation. If there is also a diagnosis of drug abuse or dependence to the substance, the abuse or dependence is coded as an additional code." In this case, the respiratory failure is the manifestation of the crack cocaine overdose and should not be sequenced as the principal diagnosis, regardless of whether or not the patient was placed on ventilation.

3. c: Refer to Coding Clinic Adverse Effect guidelines, "Codes from the E930-E949 series must be used to identify the causative substance for an adverse effect of drug, medicinal or biological substance. The effect, such as tachycardia, delirium, gastrointestinal hemorrhaging, vomiting, hypokalemia, hepatitis, renal failure or respiratory failure, is coded and followed by the appropriate code from the E930 E949 series." (Coding Clinic, Guidelines effective 10/1/02 and 4th Quarter, 1990, p. 25.)

4. b: The acute myocardial infarction (AMI) required admission and is the principal diagnosis, even though the respiratory failure developed prior to the admission and required immediate attention (Coding Clinic, 2nd Quarter 1991).

5. a: Acute idiopathic polyneuritis may begin with some viral illness or immunization and is followed by rapidly spreading weakness, usually beginning in the legs and spreading to involve the muscles of the arms and trunk. Intercostal muscle paralysis may lead to respiratory failure and require assisted ventilation. The condition after study that led to the admission was acute polyneuritis (Guillain-Barre syndrome) and therefore, is sequenced as the principal diagnosis (Coding Clinic, 2nd Quarter 1991).

6. d: The interaction of prescription drugs with alcohol is classified as a poisoning in ICD-9-CM, with the poisoning code taking precedence over the code for the resulting condition (respiratory failure). Sequence the poisoning codes first and an additional code for the respiratory failure as a secondary condition. (Coding Clinic, 3rd Quarter 1991).

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