SESSION TITLE: Respiratory Support Posters
SESSION TYPE: Original Investigation Poster
PRESENTED ON: Wednesday, October 30, 2013 at 01:30 PM - 02:30 PM
PURPOSE: Intermittent positive airway pressure ventilation (IPPV) reduces right ventricular (RV) stroke volume in COPD. We aim to determine whether this reduction in RV stroke volume occurs via changes to RV preload and/or afterload.
METHODS: Subjects with severe COPD receiving IPPV immediately prior to lung transplantation were prospectively assessed with pulmonary arterial catheterization. Changes to RV stroke volume (measured as the pulmonary pulse pressure change) were assessed at end-expiration, early-inspiration and end-inspiration. Changes to preload and afterload were assessed by inspiratory changes to right atrial pressure and diastolic pulmonary arterial pressure respectively. Data acquisition software enabled beat-by-beat, intra-breath hemodynamic assessment.
RESULTS: Sixteen patients were recruited with median [IQR] age of 58 [51-61] yrs and post bronchodilator FEV1 of 0.57 [0.50-0.73] L. Patients were ventilated using IPPV with an inspiratory positive airway pressure of 20 [18.5-25] cm H2O, zero extrinsic positive end-expiratory pressure, respiratory rate of 6 breaths/min and fraction of inspired O2 of 60%. IPPV was associated with a reduced pulmonary pulse pressure from end-expiration to end-inspiration (3.6 [1.4-5.4] mm Hg, P=0.007). This reduction in pulmonary pulse pressure was associated with both an increase in RV afterload (spearman r (rs)=0.62, P=0.010) and a reduced RV preload (rs=0.57, P=0.022). Closer analysis reveals the reduction in pulmonary pulse pressure from end-expiration to early-inspiration was associated with an increase in RV afterload (rs=0.76, P=0.001) but not with reduced RV preload (rs=0.46, P=0.073). In contrast, the reduction in pulmonary pulse pressure from early-inspiration to end-inspiration was associated with a reduced RV preload (rs=0.56, P=0.024) but not with increased RV afterload (rs=0.26, P=0.327).
CONCLUSIONS: Positive pressure ventilation reduces RV stroke volume which occurs predominantly in association with increased RV afterload during the early phase of inspiration and predominantly in association with reduced RV preload during the later phase of inspiration.
CLINICAL IMPLICATIONS: Better understanding of heart-lung interactions will facilitate the development of improved ventilation strategies for COPD patients, especially for patients at risk of RV failure.
DISCLOSURE: The following authors have nothing to disclose: Jeremy Wrobel, Bruce Thompson, Christopher Stuart-Andrews, Kirk Kee, Gregory Snell, Mark Buckland, Trevor Williams
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