The aim of this study is to examine inhalation behavior in patients enrolled in the German Ventavis patient support program Ventaplus when these patients are switched from Ventavis (Iloprost) 10 μg/mL to Ventavis (Iloprost) 20 μg/mL formulation.

The VENTASWITCH study will be a local, prospective and retrospective, observational, case-crossover study. Data are collected and downloaded from the I-Neb AAD (Adaptive Aerosol Delivery) System. Two data collection periods are planned: period one; data collection from the last 3 months using Ventavis (Iloprost) 10 μg/mL (V10) before the index date of switching to Ventavis (Iloprost) 20 μg/mL (V20) (retrospective part) and period two; data collection for 3 months using V20 from index date (prospective part).

Inclusion Criteria:

• Patients aged ≥18 years at time of signing informed consent.
• Patients, diagnosed with group 1 PAH.
• Patients must be enrolled in the German Ventavis patient support program Ventaplus.
• Patients who either already switched from V10 to V20 therapy or who agreed to do so according to their physician's decision.
• Patients must have been on V10 therapy for at least 2 weeks.
• Written informed consent must be obtained.

Exclusion Criteria:

- participation in other clinical or interventional study.

The study will be conducted in patients who are enrolled in the German Ventavis patient support program Ventaplus which is executed for Bayer by the company Contra Care GmbH, Nürnberg. Patients who are enrolled in the program and repeatedly experienced extended inhalation times with Ventavis (Iloprost) 10 μg/mL which could possibly result in incomplete inhalations, are currently being switched to Ventavis (Iloprost) 20 μg/mL by their physician.