CHANGE OF LUNG MECHANICS AND DEAD SPACE FRACTION IN PATIENTS WITH DIFFUSE ALVEOLAR HEMORRHAGE REQUIRING PRONE POSITIONING: A CASE SERIES

Abstract

SESSION TITLE: Fellows Diffuse Lung Disease Posters SESSION TYPE: Fellow Case Report Posters PRESENTED ON: October 18-21, 2020 INTRODUCTION: Diffuse alveolar hemorrhage (DAH) is a catastrophic syndrome causing respiratory failure (1). Prone positioning improves oxygenation and decreases mortality in patients with acute respiratory distress syndrome (2). In patients with refractory hypoxemia from DAH, prone positioning may be used as rescue therapy. However, we know little about the impact of prone positioning in lung mechanics and gas exchange of patients with DAH. CASE PRESENTATION: Four patients were admitted to the intensive care unit for refractory hypoxemia requiring prone positioning, and ultimately diagnosed with DAH — three through bronchoscopy and one through autopsy. Table 1 shows the demographics, laboratory data, and interventions. Two patients were male and two patients were female. Ages ranged from 19 to 71 years. The etiologies of DAH included: acute lymphoblastic leukemia, pulmonary angiosarcoma, and giant cell vasculitis; one patient had no identified etiology. One patient had pancytopenia from leukemia and the remaining three had leukocytosis and anemia with hemoglobin count from 8.5 to 10.4 g/dL on admission. No significant coagulopathy was noted but a high fibrinogen level was observed in all cases. Three patients had positive bacterial growth in sputum cultures. All patients required vasopressors and neuromuscular blockade prior to prone positioning. Three received pulse-dose steroids (at least 1g of methylprednisone daily for three days) after the diagnosis was made. Table 2 shows the ventilatory settings, gas exchange, and lung mechanics at baseline. Prior to prone positioning, PaO2/FiO2 ratios were less than 150 and dead space fraction ranged from 27% to 60%. Figure 1 shows gas exchange and lung mechanics at different time points. Following prone positioning, all patients had decreased dead space fraction after 8 hours of prone positioning. No specific pattern was identified in the change of lung mechanics and gas exchange while minimal change was observed in mechanical power. DISCUSSION: The histopathologic changes in DAH reveal a distinctive mechanism of lung injury affecting lung mechanics and gas exchange. In an autopsy study comparing ARDS patients with and without DAH, those with DAH had significantly lower static compliance and PaO2/FiO2 (3). Prone positioning could theoretically ameliorate V/Q mismatch and reduce inflammation in DAH. The finding of dead space fraction improvement following prone positioning suggests a possible benefit of applying prone positioning to DAH patients with refractory hypoxemia. Future studies are needed to examine the role of prone positioning in this population. CONCLUSIONS: We present the first case series of change in lung mechanics and dead space fraction in patients with DAH who received prone positioning. While there exists a paucity of evidence to support this modality, prone positioning can potentially be used as a rescue therapy for refractory hypoxemia in DAH. Reference #1: Lara AR, Schwarz MI. Diffuse alveolar hemorrhage. Chest. 2010;137(5):1164-71 Reference #2: Guérin C, Reignier J, Richard JC, Beuret P, Gacouin A, Boulain T, et al. Prone positioning in severe acute respiratory distress syndrome. N Engl J Med. 2013;368(23):2159-68 Reference #3: Thille AW, Peñuelas O, Lorente JA, Fernández-Segoviano P, Rodriguez JM, Aramburu JA, et al. Predictors of diffuse alveolar damage in patients with acute respiratory distress syndrome: a retrospective analysis of clinical autopsies. Crit Care. 2017;21(1):254 DISCLOSURES: No relevant relationships by James Kornfield, source=Web Response No relevant relationships by Chi Chan Lee, source=Web Response No relevant relationships by Stephanie Nonas, source=Web Response