This disclosure concerns improved capabilities for evaluating whether additional medical tests need to be conducted for a diagnosis of a pulmonary arterial hypertension (PAH) condition in a patient. The method includes determining that the patient is at rest and measuring a partial pressure of carbon dioxide in a composite gas, comprising: transferring an expiration from the patient's mouth to a carbon dioxide analyzer； measuring end tidal carbon dioxide (EtCO2) from each of a plurality of oral expirations from the patient； and calculating a composite EtCO2 value. The method further includes comparing the composite EtCO2 value to a range of stored carbon dioxide partial pressure values； generating a signal indicating whether additional medical tests need to be conducted in response to the comparing； and providing the generated signal to an indicator, the indicator adapted to respond to the generated signal to provide an output in a human cognizable format.
