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Mechanical Ventilation – Are You Counting Hours or Days?

By Mary Ann Polantz, RHIT, CCS, CCDS | Senior Manager, Coding & Documentation Improvement Services

In my 30+ years of coding, mechanical ventilation has been at the top of my list to focus on when performing audits.  And with the critical importance that ventilators are playing in the COVID-19 pandemic, the ability to code these cases correctly has become essential.  Yet I am still finding errors in this area.  The problem usually occurs with documentation within the medical record.  Some coders work off of progress notes rather than respiratory therapy documentation.  Physicians may write a time and date in the progress notes, but this may not actually happen until much later since documentation occurs after the physical care of the patient.  I find that the best source document for calculating hours are respiratory therapy notes.  Back in the day, the hand written mechanical ventilation flow sheets were the ideal source for calculating the ventilation hours needed to assign the proper code.  With the move to EHR (electronic health record), this documentation can sometimes be challenging to find and validate.

There are a few guidelines that are particularly important when considering ICD-10-PCS codes:

  • When a patient is intubated prior to arrival to the ER, begin counting hours at the time of admission.
  • When it is necessary to replace the endotracheal tube due to leakage, the replacement would be counted as part of the initial duration.
  • When a patient begins the weaning process, the entire duration is counted. However, if the patient is weaned and extubated, but fails, and is put back on the ventilator, this would not be considered continuous.
  • When a patient self-extubates and the physician did not intend to discontinue ventilation, the clock continues to run.  As long as the patient is placed back on the ventilator, you should continue to count the entire duration.
  • Tracheostomy patients receiving BiPAP through a T-tube are coded as mechanical ventilation.
  • If a patient is transferred while intubated, the duration would end at the time of transfer.
  • Mechanical ventilation terminates when the patient is extubated and the ventilator is turned off.

Do not count the number of days that the patient is on the ventilator; what’s compliant is the number of hours of ventilation that the patient receives.  If a patient is admitted on April 2 and placed on a ventilator at 5:00 a.m. and is extubated on April 6 at 4:45 a.m., intubation time would be 95.75 hours and would be assigned ICD-10-PCS code 5A1945Z, not 5A1955Z.  The code 5A1955Z should only be assigned on encounters with a length of stay greater than 96 hours. An edit is now in place in the Medicare Code Editor to alert the coder of “Procedure inconsistent with length of stay.”

Coding mechanical ventilation can have a major impact on MS-DRG assignment.  The COVID-19 virus typically affects the respiratory system and a lot of affected patients end up on a ventilator.  In reference to COVID-19 patients that require ventilation, cases will group to MS-DRG 207 when the patient is on the ventilator for >96 hours.  Cases will group to MS-DRG 208 when the patient is on the ventilator for <=96 hours. 

MS-DRG 207 and 208 Table

As you can see, there is a significant difference in the relative weights for MS-DRG 207 and 208. We need to be more careful and make sure that we are calculating these hours appropriately and assigning the correct ICD-10-PCS codes.

In another scenario, patients who are admitted with sepsis from COVID-19 and end up on a ventilator >96 hours will group to MS-DRG 870.

MS-DRG 870 Table

As you can see, MS-DRG 870 is only assigned when a patient remains on a ventilator for >96 hours, which makes it even more vital that the ventilator is assigned and the calculation of duration is correct.

So in closing, hopefully we won’t have to be coding too many more of the COVID-19 ventilator cases.  But in the meantime, be vigilant and careful in counting the hours.

For more information in determining the accuracy of your ventilator coding and the CBIZ Ventilator Coding Assessment Services, please contact our office at 609-918-0990 or


The following  Coding Clinics provide guidance for coding mechanical ventilation. Coding Clinics, 1st Qtr. 2013, p. 12 and Coding Clinic 4th Qtr. 2014, p. 3.

ICD-10-CM Official Guidelines for Coding and Reporting provides guidance for coding Coronavirus Infections, effective April 1, 2020 – September 30, 2020:Section 1.C.1.g – Coronavirus Infections, Section 1.C.15.s – Pregnancy, Childbirth and the Puerperium and Section 1.C.1.d – Sepsis, Severe Sepsis and Septic Shock.

AHIMA and AHA FAQ: ICD-10-CM Coding for COVID-19 [Updated April 17, 2020] provides answers to your pressing COVID-19 questions.

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