Pulmonary hypertension (HTP) is classified according to severity. This helps healthcare professionals understand how much PH affects a person so they can identify the right treatment.

The system that is used to classify HTP was developed byWorld Health Organization (WHO/WHO). This takes into account the level of exertion that PH patients can perform before they start to notice symptoms such as shortness of breath.

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WHO functional class 1: No symptoms; physical activity does not cause fatigue, palpitations, shortness of breath or chest pain;

WHO functional class 2: Comfortable at rest, but symptoms occur with regular physical activity;

WHO functional class 3:Comfortable at rest, but have symptoms with less effort than usual physical activities, for example raising the arms;

WHO functional class 4: Symptoms present at rest.