Pulmonology Coding Alert

Flight simulation in a pulmonology practice? Absolutely.

You could safely say that most of your patients have travel plans that include flying on planes—and some of the more adventurous ones may be thinking of mountain trekking or even paragliding as part of their summer vacations. But how certain are you that they’re not going to need to carry oxygen with them on these trips? It’s a question worth considering, especially for those with chronic conditions that could turn a holiday into a medical emergency.

Performing a high altitude simulation test (HAST) to determine whether supplemental oxygen is necessary makes a lot of sense as a precautionary measure for your at-risk patients who have flight or high-altitude plans in the works. Here’s instruction on what’s involved in performing and reporting HASTs.

The Skinny on Airborne Oxygen

Air on a plane is a tightly controlled substance—and your body has to adjust. The Federal Aviation Administration requires that cabin pressure be kept at 8,000 ft. which is the equivalent of 15.1 % oxygen, and the body has a “normal, physiologic response to this,” according to the Jan. 2019 American Thoracic Society presentation, “High Altitude Simulation Testing.”

The body reacts by “increasing its minute ventilation” and does this by “increasing its title volume and it improves its V/Q [ventilation/perfusion] mismatch via hypoxic-induced vasoconstriction and by increasing its cardiac output, mainly by increasing the heart rate,” Stephen Doyle, DO, MBA, explains in the presentation. “Patients with pulmonary disease have a difficult time maintaining these normal physiologic responses,” he says. “The inability to do this can lead to severe neurological, cardiac, and pulmonary complications.”

Do a Prelim Test for Oxygen Desaturation

To find out if a patient will experience oxygen issues during a high altitude experience, follow these testing guidelines to help you answer that question, says Doyle. The BTS recommends in-office pulse oximetry testing to measure SpO2:

• If the level is greater than 95%, your patient doesn’t need further testing.
• If the SpO2 is between 92-95%, your patient needs further testing and a HAST is recommended.
• If the level is less than 92%, the patient needs to travel with supplemental oxygen, regardless.

What’s Involved in a HAST

During a high altitude simulation test, your patient walks on a treadmill or pedals a bike with minimal resistance, while breathing a gas mixture of 15% oxygen through a non-rebreather (NRB) placed over the patient’s mouth. The reason for the exercise is to simulate walking at high altitudes, such as around the airplane cabin, says Doyle, or up hills. You’ll provide continuous pulse-ox so you can monitor the heart rate and SpO2 throughout the testing, and, the patient will need a nasal cannula, so you can supply supplemental oxygen if necessary, he adds.

What you’re looking for: With the 15 % oxygen flowing, you’ll monitor the patient’s heart rate and SpO2 continuously, says Doyle, with the goal to keep the SpO2 greater than 88%.

Final step: After the patient has been breathing the 15% oxygen mixture for 20 minutes, you should perform an arterial blood gas (ABG) test to assess the patient’s PaO2 [partial pressure of oxygen].

Code it: For the blood draw, you’ll use CPT^® code 36600 (Arterial puncture, withdrawal of blood for diagnosis), and code 82805 (Gases, blood, any combination of pH, pCO2, pO2, CO2, HCO3 (including calculated O2 saturation); with O2 saturation, by direct measurement, except pulse oximetry) for the gas analysis.

1st Scenario: Patient Needs Supplemental Oxygen

If it’s necessary during the test, you’ll add supplemental oxygen at l liter per minute to keep the patient’s SpO2 greater than 88%, Doyle says. Key: The amount of supplemental oxygen you add during the test to keep the level greater than 88% is the amount of oxygen the patient will require for travel, so you’ll prescribe that amount of oxygen for travel.

Code it: You’ll report code 94453 (High altitude simulation test (HAST), with interpretation and report by a physician or other qualified health care professional; with supplemental oxygen titration) for a HAST with supplemental oxygen.

Coding tip: Be sure to document the amount of extra oxygen the patient needed during the test to support the supplemental oxygen diagnosis and the resulting prescription.

“If it is determined that supplemental oxygen is required during flight, the physician has to titrate the oxygen to allow for acceptable O2 saturation levels,” confirms Carol Pohlig, BSN, RN, CPC, ACS, senior coding and education specialist at the Hospital of the University of Pennsylvania.

Crisis control: It may seem obvious, but if at any point during testing, the patient develops neurologic, cardiac, or respiratory symptoms, or if they require more than 6 liters of supplemental oxygen to maintain a SpO2 greater than 88%, stop the test, advises Doyle. In this case, you’d report 94453-53, with modifier 53 indicating you discontinued the service.

2nd Scenario: You Didn’t Add Supplemental Oxygen

If the patient didn’t need extra oxygen to keep the SpO2 above 88% during the HAST, you’ll report code 99452 (High altitude simulation test (HAST), with interpretation and report by a physician or other qualified health care professional).

Caveat: You still may need to prescribe supplemental oxygen for travel, based on the PaO2 results from the ABG test, according to these parameters from the American Thoracic Society presentation:

• If the PaO2 is greater than 55 millimeters of mercury, the test is negative and there is no need for supplemental oxygen.
• PaO2 is between 50-55 millimeters of mercury, the test is borderline and further HAST with minimal exertion is warranted.
• PaO2 is less than 50 millimeters of mercury, the test is positive and your patient needs supplemental oxygen prescribed prior to travel.

Code it: You would report 99452 for the HAST testing and, depending PaO2 level, prescribe the required amount of oxygen for travel.

Do this: Advise your patients to verify that their portable oxygen concentrators are approved with airlines and are in compliance with other airline rules about bringing portable oxygen on a plane.

“Airlines have their own policies for FAA-allowed devices,” says Pohlig. “Some airlines may require the patient to rent the portable concentrators from them directly or through an approved vendor to guarantee device compliance with FAA regulations.”

Best practice: Patients should alert the airline in advance of travel (typically a few days prior), says Pohlig, and be prepared to present a physician letter stating that the oxygen is necessary, she adds.

Resources:

To view the American Thoracic Society’s “High Altitude Simulation Testing” presentation, go to https://www.thoracic.org/professionals/clinical-resources/video-lecture-series/pulmonary-function-tests /high-altitude-simulation-testing.php.

To read the Federal Aviation Administration’s advisory on portable oxygen, see https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_120-95A.pdf.