Non-invasive monitoring of pulmonary blood flow, functional residual capacity, and shunt index in a porcine model
Translational Medicine Communications(2023)
Abstract
Background Management of mechanically ventilated patients can be improved with monitoring of key pulmonary function parameters that facilitate individualization and optimization. The VQm Pulmonary Health Monitor™ (PHM) (Rostrum Medical Innovations Inc., Vancouver, Canada) is a new monitor that continuously measures pulmonary blood flow (PBF), functional residual capacity (FRC) and a novel parameter: shunt index (Q si ). The goal of this study was to provide an initial assessment of the performance of the VQm PHM™ when compared with reference measures of PBF, FRC and intra-pulmonary shunt. Methods This was a prospective, experimental, large animal (porcine) study. After baseline measurements, three interventions were performed: increased cardiac output (CO) using dobutamine infusion, increased PEEP (from 4 to 12 cmH 2 O), and experimental shunt induced by an extracorporeal circuit. PBF, FRC and shunt were measured by the VQm Pulmonary Health Monitor™ (PHM) before and after each intervention. The PHM™ uses sequential gas delivery to deliver targeted alveolar concentrations of CO 2 or N 2 O. PBF and FRC were calculated using CO 2 bolus delivery and the modified differential Fick equation. Shunt was estimated from the number of breaths required to eliminate N 2 O after a 25-breath N 2 O bolus and expressed as Q si . PHM™-derived PBF and Q si were compared to thermodilution CO and calculated Berggren shunt, respectively. Results Studies were completed in 19 animals. Measurements of PBF, FRC and Q si obtained from the PHM™ trended as expected following each intervention. The mean difference between paired values of PBF was − 0.2 ± 0.9 L/min and the 95
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Key words
Pulmonary physiology, Pulmonary blood flow, Functional residual capacity, Intrapulmonary shunt, sequential gas delivery
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