PURPOSE: Retrospective review of the effects of short term inhaled nitric oxide [iNO] and 100% oxygen on patients with idiopathic pulmonary fibrosis [IPF] and pulmonary arterial hypertension (PAH).
METHODS: All patients met accepted diagnostic criteria of IPF. Patients were selected for catheterization if non-invasive evaluation raised suspicion of PAH. Patients were given supplemental oxygen to maintain SpO2 ≥ 90%. After baseline hemodynamic data, 16 patients underwent vasodilator testing for up to 10 minutes with 20-40 parts per million of iNO. Fourteen patients also received 100% oxygen for up to 10 minutes. A response was defined as a 20% reduction in mean pulmonary artery pressure [mPAP] or pulmonary vascular resistance [PVR].
RESULTS: Eleven of the 16 patients [69%] responded to iNO (average change in mPAP = 8.90 ± 5.3 mmHg; average change in PVR = 160.4 ± 107.3 dynes*sec/cm5). Five of the 14 patients [35.7%] responded to 100% oxygen (average change in mPAP = 6.7 ± 5.5 mmHg; average change in PVR = 40 ± 107 dynes*sec/cm5). Responders had a mean duration of symptoms (DOS) of 4.3 years, FVC of 2.41 L and DLCO of 6.80 ml/min/mmHg. Non-responders had a mean DOS of 6.75 years, FVC of 1.96 L, and DLCO of 5.29 ml/min/mmHg. Four non-responders were treated with sildenafil. In three [75%], there was ≥ 20% increase in six-minute walk distance at three months when compared to baseline.
CONCLUSION: Vasoreactivity is common in IPF-related PAH. The differential response to iNO and 100% oxygen suggests that hypoxemia is not the sole etiology of PAH in IPF; arteriopathy also plays a role. Non-responders had more advanced IPF than responders. Lack of vasoreactivity does not preclude response to chronic sildenafil therapy.
CLINICAL IMPLICATIONS: Treatment of pulmonary hypertension in IPF may result in improvement in functional status. Similar to idiopathic PAH, vasoreactivity does not predict response to chronic PDE-5 inhibitor therapy.
DISCLOSURE: Wayneinder Anand, No Financial Disclosure Information; No Product/Research Disclosure Information