Abstract
(1) Background: inhaled epoprostenol (iEPO) delivered via high-flow nasal cannula (HFNC) has been reported to be effective for pulmonary hypertension and right ventricular dysfunction. In vitro studies have identified HFNC gas flow as a key factor in trans-nasal aerosol delivery efficiency; however, little evidence is available on the clinical impact of flow titration on trans-nasal aerosol delivery. At our institution, iEPO via HFNC was initiated in 2015 and the concept of flow titration during iEPO via HFNC has been gradually accepted and carried out by clinicians in the recent years. (2) Methods: a retrospective review of the electronic medical records for all adult patients who received iEPO via HFNC in a tertiary teaching hospital. Pre- and post- iEPO responses were reported for patients whose HFNC flow was titrated or maintained constant during iEPO delivery. Positive response to iEPO was defined as the reduction of mean pulmonary arterial pressure (mPAP) > 10% for pulmonary hypertension patients or the improvement of oxygenation [pulse oximetry (SpO2)/fraction of inhaled oxygen (FIO2)] > 20%. The number of responders to iEPO was compared between groups with titrated vs constant flow. (3) Results: 51 patients who used iEPO to treat pulmonary hypertension and/or right ventricular dysfunction were reviewed. Following iEPO administration via HFNC, mPAP decreased (43.6 ± 11.7 vs. 36.3 ± 9.7 mmHg, p < 0.001). Among the 51 patients, 24 had concomitant refractory hypoxemia, their oxygenation (SpO2/FIO2) improved after iEPO delivery (127.8 ± 45.7 vs. 157.6 ± 62.2, p < 0.001). During iEPO initiation, gas flow was titrated in 25 patients and the remaining 26 patients used constant flow. The percentage of patients in the flow titration group who met the criteria for a positive response was higher compared to the group with constant flow (85.7% vs. 50%, p = 0.035). Pre- vs post-iEPO responses were significant in the flow titration group included improvement in cardiac output (p = 0.050), cardiac index (p = 0.021) and FIO2 reduction (p = 0.016). These improvements in hemodynamics and FIO2 were not observed in the constant flow group. (4) Conclusion: in patients with pulmonary hypertension and/or right ventricular dysfunction, trans-nasal iEPO decreased pulmonary arterial pressure. It also improved oxygenation in patients with combined refractory hypoxemia. These improvements were more evident in patients whose gas flow was titrated during iEPO initiation than those patients using constant flow.
Highlights
Inhaled epoprostenol is a pulmonary vasodilator which has been used off-label to treat pulmonary hypertension in the United States for over 15 years [1]
Our hypothesis was that flow titration would deliver a higher inhaled dose of Inhaled epoprostenol (iEPO), which would increase the number of patients with a positive response to iEPO compared to those receiving constant flow
We found that iEPO delivery via high-flow nasal cannula (HFNC) reduced mean pulmonary arterial pressure (mPAP) and improved cardiac output (CO) and cardiac index (CI) in patients with pulmonary hypertension or right ventricular dysfunction
Summary
Inhaled epoprostenol (iEPO) is a pulmonary vasodilator which has been used off-label to treat pulmonary hypertension in the United States for over 15 years [1]. Transnasal pulmonary delivery of iEPO via high-flow nasal cannula (HFNC) provides a feasible route, which has been shown to deliver sufficient dose to elicit a clinical response [8,9]. The concept of flow titration during trans-nasal aerosol delivery based on clinical response may provide a surrogate to measuring a patient’s inspiratory flow [8]. When iEPO was delivered via HFNC, gas flow was titrated based on patient’s response when clinicians were available. Due to staff’s workload or availability, there were some patients still receiving constant flow during iEPO delivery via HFNC. Our hypothesis was that flow titration would deliver a higher inhaled dose of iEPO, which would increase the number of patients with a positive response to iEPO compared to those receiving constant flow
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