Q&A: Should acute respiratory failure be the principal diagnosis?

Q: I just had a case at work where the patient arrived in respiratory distress, was intubated, and was placed on a vent, treated with IV Solumedrol, HHN, IV antibiotics. The patient came upstairs on the vent. The physician documented acute hypoxic respiratory failure due to COPD exacerbation. I coded acute respiratory failure first, but the coding professional reviewing the record said that was incorrect. Do you have a reference for this or a coding guideline to help support this diagnosis?

A: We get asked variations of this same question all the time and, unfortunately, there are many different opinions as to what the principle diagnosis should be in these situations. Each medical record needs to be able to stand on its own and support the choice of the principle diagnosis. Let’s start by looking at the definition of a principal diagnosis. Per the Official Guideline for Coding and Reporting, Section II, it is the “condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care.”

So, acute respiratory failure can be coded if the condition meets the definition for the principal diagnosis and is clinically supported in the medical record by a hands-on treating provider without any conflict existing in the documentation between any consulting and attending provider.

Now, we always need to go a step further and consider the circumstances of an admission, any diagnostic workup and/or therapy provided, and whether there are any coding conventions, guidelines, or Coding Clinic recommendations that would affect our choice, such as the direction given in etiology/manifestation pairs. The respiratory failure, however, is not one of these pairs, so there is no direction for the underlying cause being sequenced first. So, with no guidelines saying otherwise, the respiratory failure could be sequenced as the principal diagnosis.

Respiratory failure is defined as abnormal arterial oxygenation and/or carbon dioxide accumulation. Diagnostic criteria for hypoxemic respiratory failure include partial pressure of oxygen (pO2) less than 60 millimeters of mercury (mmHg) on room air or pO2/fraction of inspired oxygen (FiO2) ratio less than 300, or 10mmHg decrease in baseline pO2 (if known). For hypercapnic respiratory failure, we look for pCO2 greater than 50mmHg with pH of less than 7.35, or 10mmHg increase in baseline pCO2 (if known). The greater the specificity regarding the acuity and type of respiratory failure, the more accurate the coding staff can be with code assignment. We always want to encourage our providers to be as specific as possible based on the information available to them.

Now, it’s hard for me to tell you why there’s a disagreement regarding the principle diagnosis in your scenario because I’m not looking at the complete medical record. I can tell you, however, that many believe that the cause of the respiratory failure should be coded as the principle diagnosis. I can tell you confidently, though, that there is no rule that states this. What I tell people is that you are only allowed to choose one principle diagnosis and if you have more than one condition that potentially meets the definition, then you need to evaluate each condition to determine which one most appropriately should be the principle diagnosis.

One good way of determining what caused the admission (what “bought the bed”) is to ask yourself whether any of the conditions could be treated safely in observation. If the answer is yes, then that diagnosis would likely not be the principal diagnosis.

Also ask whether all the conditions meet medical necessity? Out of the ones you mentioned, acute respiratory failure is the only diagnosis that requires inpatient treatment.  Consider asking, too, whether the conditions are acute conditions or chronic conditions? Most chronic conditions do not support an inpatient admission. That being said, we need to look the patient’s history to see if they have multiple conditions going on at the same time as that would certainly influence whether the provider decides to admit them. 

Another question I would ask is whether, based on the other conditions present, the physician would have admitted the patient if the respiratory failure was not present. If the answer is no, then those other conditions would likely not be the principal diagnosis.

My best advice here is to query the provider (if the record’s not clear) as to which diagnosis led to the admission. I would also ask the coding staff about the advice they’re following and where you can find it—they may be referencing something you’re not aware of. 

Editor’s Note: Sharme Brodie, RN, CCDS, CDI education specialist and CDI Boot Camp instructor for HCPro in Middleton, Massachusetts, answered this question. For information, contact her at sbrodie@hcpro.com. For information regarding CDI Boot Camps, click here.