• 6-minute walk distance (measured at Week 3)
  

• Oxygen saturation (SpO2) at rest
  
• Lowest SpO2 with exertion (measured during 6-minute walk test)
  
• Total duration of SpO2 below 89% with exertion (measured during 6-minute walk test)
  
• Recovery time (measured during 6-minute walk test)
  
• Mean SpO2 and area under the curve (measured during 6-minute walk test)
  
• Desaturation index (measured by the 6-minute walk distance multiplied by the SpO2 mean value)
  
• Level of breathlessness (measured by Borg dyspnea index questionnaire) (all measured at Week 3)
  

IPF is a disease that damages the air sacs in the lungs and leads to widespread and permanent scarring of lung tissue. Individuals with IPF may experience breathing difficulties, cough, chest pain, and a decreased exercise capacity. There is no cure for this disease, and individuals usually die within 3 to 5 years. It is recommended that individuals with IPF engage in moderate exercise, as this can help maintain strength and improve lung function. Many individuals with IPF also suffer from pulmonary hypertension, which is high blood pressure in the arteries leading to the lungs.

Sildenafil, a medication currently used to treat pulmonary hypertension, increases blood flow to the lungs and enhances gas exchange within the lungs.

The purpose of this study is to evaluate the effectiveness of sildenafil at improving exercise tolerance and breathing difficulties in individuals with IPF and pulmonary hypertension.

This 3-week study will enroll individuals with IPF and pulmonary hypertension. Study visits will occur at baseline, and Weeks 1 and 2. At the baseline visit, participants will perform a 6-minute walk test, which will measure the distance walked in a 6-minute period. Oxygen levels will be measured prior to and during the test, and standardized questionnaires will be completed to assess breathing difficulties. A second 6-minute walk test will be performed

1 hour following the first test. At the Week 1 visit, participants will be randomly assigned to receive a single dose of either 50 mg of sildenafil or placebo. One hour after receiving the medication, they will complete another 6-minute walk test. The Week 2 visit will be identical to the Week 1 visit, except participants who received sildenafil at Week 1 will receive placebo at Week 2, and vice versa.