Pulmonology Coding Alert

High Altitude Simulation Training:

Correctly Code HAST for Post-COVID Patients Before They Travel

Know when to choose between 99452 and 99453.

With summer vacations around the corner, you can guess that some patients may be making plans that require air travel. If a pulmonology patient is diagnosed with a condition that could cause unforeseen consequences at higher altitudes, such as chronic obstructive pulmonary disease (COPD), cystic fibrosis, or post COVID-19, your pulmonologist may order high-altitude simulation testing (HAST) for the patient.

Find out what’s included in HAST procedures and how to properly code the service.

Borderline SpO2 May Need Further Testing

Pulmonologists perform HAST services to check a patient’s oxyhemoglobin saturation. In a typical scenario, the patient wears an airtight mask on their face and breathes a low oxygen mixture containing approximately 15 percent oxygen. This low oxygen mixture helps simulate the breathing conditions at a high altitude, such as in an airplane cabin or at a high-altitude location. The provider monitors the patient’s oxyhemoglobin saturation while the patient breathes the mixture for 15 to 20 minutes.

Definition: Oxyhemoglobin saturation is the amount of oxygen in the body’s hemoglobin, which is the red blood cell protein that carries oxygen from the lungs to the body tissues.

During HAST, the provider will attach a pulse oximeter to the patient, so the physician can monitor the patient’s heart rate and SpO2 level. SpO2 is also known as the saturation of peripheral oxygen, and it measures the amount of oxygen carried in your blood.

As the patient breathes in the low oxygen mixture, the physician watches the heart rate and SpO2 with the goal of keeping the SpO2 level above 88 percent.

The patient will also wear a nasal cannula that can supply supplemental oxygen if needed. If the patient’s SpO2 level drops below 88 percent, supplemental oxygen will be added at a rate of one liter per minute to raise the SpO2 above the necessary threshold. However, if the patient begins to experience respiratory, cardiac, or neurological symptoms, or the patient needs more than six liters of oxygen to maintain an SpO2 above 88 percent, the provider should stop the testing.

After the procedure, the provider examines the results and compiles their report. The provider will use the results to decide whether the patient needs further testing or should travel with supplemental oxygen.

Know the Difference Between HAST Codes

The CPT® code set contains two codes for HAST — 94452 (High altitude simulation test (HAST), with interpretation and report by a physician or other qualified health care professional) and 94453 (… with supplemental oxygen titration) — with the difference between the codes being the administration of supplemental oxygen titration.

During HAST, “the provider determines the amount of oxygen a patient needs in a high-altitude setting based on the symptoms elicited during testing,” says Carol Pohlig, BSN, RN, CPC, manager of coding and education in the department of medicine at the Hospital of the University of Pennsylvania in Philadelphia. Based on the oxygen amount determined during 94452, “the patient undergoes same-day repeat testing to see if the oxygen prescription treats the patient’s high-altitude symptoms,” Pohlig adds. The second component is supplemental oxygen titration.

Note: Codes 94452 and 94453 are mutually exclusive, and only one code can be reported on a given date. For example, suppose your pulmonologist performs HAST, and the results indicate the patient needs further testing with supplemental oxygen titration. In this scenario, you’ll assign only 94453 since the code includes the testing and the supplemental oxygen titration.

Understand What Procedures Are Included With HAST

HAST procedures involve several components, including some that are represented by separate individual CPT® codes.

Pulse oximetry (oxygen saturation in the blood), coded to 94760 (Noninvasive ear or pulse oximetry for oxygen saturation; single determination) and 94761 (… multiple determinations (eg, during exercise)), is included in HAST and “cannot be reported separately under any circumstances,” Pohlig says. To help you remember this rule, 94452 and 94453 feature parenthetical notes that state you should not report the codes in conjunction with 94760 and 94761.

HAST procedures also include evaluation and management (E/M) codes, such as 99202-99215 (Office or other outpatient visit for the evaluation and management …). While the E/M codes are included in HAST, they can be reported separately when appended with modifier 25 (Significant, separately identifiable evaluation and management service by the same physician or other qualified health care professional on the same day of the procedure or other service) if there is separate identifiable patient management, such as COVID-19 symptom management.

Return to Travel for COVID-19 Long-Haul Patients

Physicians may order HAST before traveling for patients who have been diagnosed with post-COVID-19 symptoms, coded to U09.9 (Post COVID-19 condition, unspecified). “There may be a need for testing involving COVID long-haulers who have not regained baseline lung function or post-COVID patients who continue to require supplemental oxygen,” Pohlig says.

The COVID-19 public health emergency (PHE) has allowed healthcare providers to collect an immense amount of data to study. As providers learn more about the long-term effects of the disease, they’ll use studies like HAST to ensure their patients receive proper care. “Since we are still learning about the long-term effects of COVID-19, it would seem reasonable that these patients could undergo HAST (when travel circumstances are applicable) to prevent any unforeseen consequences,” Pohlig adds.

The symptoms and severity of a COVID-19 infection varies between patients, so providers should need to evaluate only patients that face a higher risk of complications from travel. “Not every individual who has had COVID-19 infection warrants evaluation before high-altitude travel. Instead, the approach should be based on features of the patient’s duration and severity of illness and the time course of their recovery,” wrote Andrew M. Luks, of the division of pulmonary, critical care, and sleep medicine at Harborview Medical Center, University of Washington in Seattle, and Colin K. Grissom, of the division of pulmonary and critical care medicine at Intermountain Medical Center and the University of Utah in Salt Lake City, in a June 2021 High Altitude Medicine & Biology article (www.liebertpub.com/doi/10.1089/ham.2021.0049).