Oral Sildenafil has No Acute Effect on Diffusion Capacity Measurements in Patients with Diffuse Parenchymal Lung Disease and Pulmonary Hypertension Isabel Mira-Avendano 1* , Umur Hatipoglu 1 , Catherine Sant 1 , Daniel Laskowski 1 , Ruchi Yadav 2 and Raed Dweik 1 1 Respiratory Institute, Cleveland Clinic, Cleveland, Ohio, USA 2 Imaging Institute, Cleveland Clinic, Cleveland, Ohio, USA * Corresponding author: Isabel Mira-Avendano, Respiratory Institute, Cleveland Clinic, Cleveland, Ohio, USA, Tel: 904-953-6728; E-mail: mira.isabel@mayo.edu Rec date: Apr 08, 2015; Acc date: Apr 25, 2015; Pub date: Apr 27, 2015 Copyright: © 2015 Mira-Avendano I, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract Diffuse parenchymal lung diseases have diverse etiology and treatment often requires individualization taking into consideration comorbidities. Pulmonary hypertension represents one such comorbidity which, when present, worsens prognosis and confounds approach to treatment. Sildenafil is a pulmonary vasodilator, which has recently generated considerable interest for use in patients with diffuse parenchymal lung disease and concomitant pulmonary hypertension. We wondered whether acute administration of oral sildenafil affects the diffusion capacity measurement, which is a tool for serially monitoring patients with diffuse parenchymal lung diseases. Methods: 15 patients with diffuse parenchymal lung disease and pulmonary hypertension (WHO Class III) had diffusion capacity measurements and 6 minute walk test performed before and after receiving sildenafil 20 mg orally. CT scans of the chest were scored to determine burden of interstitial lung disease. Results: The mean change in DLCO after administration of oral sildenafil was -0.26 ± 0.94 ml/min/mmHg (p=0.30) and -0.41 ± 2.84 % predicted (p=0.58). The average 6 minute walk distance at baseline was 363.28 ± 141 meters. After oral administration of sildenafil, 6 minute walk distance was 369 ± 116 meters (p=0.63). No correlation was observed between composite radiology scores and DLCO measurements or change in DLCO and radiology scores (p=0.43 and p=0.17 respectively). Conclusion: We found no acute change in diffusion capacity after a single dose of oral sildenafil in patients with diffuse parenchymal lung disease and pulmonary hypertension. Keywords: Pulmonary hypertension; Parenchymal lung disease; Diffusion capacity Introduction Diffuse parenchymal lung diseases have diverse etiology and treatment often requires individualization taking into consideration comorbidities. Pulmonary hypertension represents one such comorbidity which, when present, worsens prognosis [1,2] and confounds approach to treatment. Furthermore, with the exception of pulmonary hypertension in the setting of connective tissue disease- related parenchymal lung disease, there is controversy in the utility of treatment of pulmonary hypertension in this group of patients (WHO Group III). Sildenafil is a cyclic GMP selective phosphodiesterase type 5 inhibitor approved for use in patients with pulmonary arterial hypertension. The drug has recently generated considerable interest for use in patients with diffuse parenchymal lung disease and concomitant pulmonary hypertension. A theoretical concern has been the possible worsening in oxygenation when pulmonary vasodilators are introduced to patients with abnormal ventilation perfusion matching at baseline. In a small, but meticulously conducted physiological studies, sildenafil has shown salutary effects with improvement in pulmonary pressures with negligible impact on oxygenation and ventilation perfusion mismatch [3]. In a post hoc subgroup analysis of 84 patients with pulmonary arterial hypertension and connective tissue disease who had been included in the SUPER-1 trial, Badesch and colleagues demonstrated improvements in exercise capacity, hemodynamic changes and functional class, following 12 weeks of treatment with varying doses of sildenafil [4]. Later, 259 patients from the SUPER-1 trial were enrolled in an open label extension study (SUPER-2) of 3 years duration which demonstrated continued improvement or maintenance of functional status while on sildenafil [5]. Recently, sildenafil was associated with small but statistically significant improvements in diffusion capacity and oxygenation while having no effect on 6 minute walk distance in 180 patients with advanced idiopathic pulmonary fibrosis and pulmonary hypertension [6]. Diffusion capacity of the lung for carbon monoxide (DLCO) measurement is ubiquitously available and is used as a tool for serially monitoring patients with diffuse parenchymal lung diseases. The American Thoracic Society has endorsed its use in the assessment of patients with idiopathic interstitial pneumonias [7]. Diffusion capacity measurements are affected by blood volume and transit time in the capillary bed. Therefore, pulmonary vasodilators can potentially affect measurements by altering pulmonary vascular hemodynamics. Mira-Avendano, et al., Fam Med Med Sci Res 2015, 4:3 DOI: 10.4172/2327-4972.1000173 Research Article Open Access Fam Med Med Sci Res ISSN:2327-4972 FMMSR, an open access journal Volume 4 • Issue 3 • 1000173 F a m i l y M e d i c i n e & M e d i c a l S c i e n c e R e s e a r c h ISSN: 2327-4972 Family Medicine & Medical Science Research