['pulmonary hypertension']
['albuterol first then placebo', 'placebo first then albuterol']

        Inclusion Criteria:

          -  A Mean Pulmonary Artery Pressure >25mmHg, Pulmonary Vascular Resistance >3 wood/units
             and pulmonary arterial wedge pressure <15mmHg, as documented by right heart
             catheterization within the last 3 years

          -  Regular use of oral pulmonary vasodilators

        Exclusion Criteria:

          -  Presence of chronic respiratory disease (as documented by prior lung imaging and
             pulmonary function tests), cardiovascular disease (as documented by prior
             echocardiography and/or left heart catheterization), thromboembolic PAH (as documented
             by pulmonary angiography)

          -  women of childbearing potential who do not use accepted birth- control measures

          -  pregnant and breast-feeding women

          -  respiratory infection within 4 weeks of testing

          -  A systemic systolic arterial BP> 150 and/or diastolic arterial BP>100 on the
             experiment day

          -  A resting O2 saturation of < 90%

          -  Current smoking

          -  BMI >35 kg/m2 and/or a diagnosis of obstructive sleep apnea

          -  Use of inhaled or intravenous pulmonary vasodilators
      