ABSTRACT
BACKGROUND: Echocardiographic parameters of diastolic function depend on cardiac loading conditions, which are altered by positive pressure ventilation. The direct effects of positive end-expiratory pressure (PEEP) on cardiac diastolic function are unknown. METHODS: Twenty-five patients without apparent diastolic dysfunction undergoing coronary angiography were ventilated noninvasively at PEEPs of 0, 5, and 10 cmH2O (in randomized order). Echocardiographic diastolic assessment and pressure-volume-loop analysis from conductance catheters were compared. The time constant for pressure decay (τ) was modeled with exponential decay. End-diastolic and end-systolic pressure volume relationships (EDPVRs and ESPVRs, respectively) from temporary caval occlusion were analyzed with generalized linear mixed-effects and linear mixed models. Transmural pressures were calculated using esophageal balloons. RESULTS: τ values for intracavitary cardiac pressure increased with the PEEP (n = 25; no PEEP, 44 ± 5 ms; 5 cmH2O PEEP, 46 ± 6 ms; 10 cmH2O PEEP, 45 ± 6 ms; p < 0.001). This increase disappeared when corrected for transmural pressure and diastole length. The transmural EDPVR was unaffected by PEEP. The ESPVR increased slightly with PEEP. Echocardiographic mitral inflow parameters and tissue Doppler values decreased with PEEP [peak E wave (n = 25): no PEEP, 0.76 ± 0.13 m/s; 5 cmH2O PEEP, 0.74 ± 0.14 m/s; 10 cmH2O PEEP, 0.68 ± 0.13 m/s; p = 0.016; peak A wave (n = 24): no PEEP, 0.74 ± 0.12 m/s; 5 cmH2O PEEP, 0.7 ± 0.11 m/s; 10 cmH2O PEEP, 0.67 ± 0.15 m/s; p = 0.014; E' septal (n = 24): no PEEP, 0.085 ± 0.016 m/s; 5 cmH2O PEEP, 0.08 ± 0.013 m/s; 10 cmH2O PEEP, 0.075 ± 0.012 m/s; p = 0.002]. CONCLUSIONS: PEEP does not affect active diastolic relaxation or passive ventricular filling properties. Dynamic echocardiographic filling parameters may reflect changing loading conditions rather than intrinsic diastolic function. PEEP may have slight positive inotropic effects. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT02267291 , registered 17. October 2014.
Subject(s)
Heart Ventricles , Positive-Pressure Respiration , Catheters , Diastole , Echocardiography , HumansABSTRACT
Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) therapy is a rescue strategy for severe cardiopulmonary failure. The estimation of cardiac output during VA-ECMO is challenging. A lung circuit ([Formula: see text]Lung) and an ECMO circuit ([Formula: see text]ECMO) with oxygenators for CO2 removal ([Formula: see text]CO2) and O2 uptake ([Formula: see text]O2) simulated the setting of VA-ECMO with varying ventilation/perfusion ([Formula: see text]/[Formula: see text]) ratios and shunt. A metabolic chamber with a CO2/N2 blend simulated [Formula: see text]CO2 and [Formula: see text]O2. [Formula: see text] Lung was estimated with a modified Fick principle: [Formula: see text]Lung = [Formula: see text]ECMO × ([Formula: see text] CO2 or [Formula: see text]O2Lung)/([Formula: see text]CO2 or [Formula: see text]O2ECMO). A normalization procedure corrected [Formula: see text]CO2 values for a [Formula: see text]/[Formula: see text] of 1. Method agreement was evaluated by Bland-Altman analysis. Calculated [Formula: see text]Lung using gaseous [Formula: see text]CO2 and [Formula: see text]O2 correlated well with measured [Formula: see text]Lung with a bias of 103 ml/min [- 268 to 185] ml/min; Limits of Agreement: - 306 ml/min [- 241 to - 877 ml/min] to 512 ml/min [447 to 610 ml/min], r2 0.85 [0.79-0.88]). Blood measurements of [Formula: see text]CO2 showed an increased bias (- 260 ml/min [- 1503 to 982] ml/min), clinically not applicable. Shunt and [Formula: see text]/[Formula: see text] mismatch decreased the agreement of methods significantly. This in-vitro simulation shows that [Formula: see text]CO2 and [Formula: see text]O2 in steady-state conditions allow for clinically applicable calculations of [Formula: see text]Lung during VA-ECMO therapy.
