Conventional continuous mandatory mechanical ventilation relies on the passive recoil of the chest wall for expiration. This results in an exponentially decreasing expiratory flow. Flow controlled ventilation (FCV), a new ventilation mode with constant, continuous, controlled expiratory flow, has recently become clinically available and is increasingly being adopted for complex mechanical ventilation during surgery. In both clinical and pre-clinical settings, an improvement in ventilation (CO2 clearance) has been observed during FCV compared to conventional ventilation. Recently, Schranc et al. compared flow-controlled ventilation with pressure-regulated volume control in both double lung ventilation and one-lung ventilation in pigs. They report differences in dead space ventilation that may explain the improved CO2 clearance, although their study was not designed to compare dead space ventilation within the group of double lung ventilation. Dead space ventilation, or "wasted ventilation", is the ventilation of hypoperfused lung zones, and is clinically relevant, as it is a strong predictor of mortality in patients with the acute respiratory distress syndrome (ARDS) and is correlated with higher airway driving pressures which are thought to be injurious to the lung (lung stress). This trial aims to study the difference in dead space ventilation between conventional mechanical ventilation in volume-controlled mode and flow controlled-ventilation.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
DOUBLE
Enrollment
13
20 minutes of FCV, delivered with the CE-marked Evone ventilator (Ventinova medical, the Netherlands)
20 minutes of conventional VCV, delivered with the CE-marked Aisys CS3 (GE Healthcare, USA) or Flow-i (Getinge, Sweden) ventilators.
Antwerp University Hospital (UZA)
Edegem, Antwerp, Belgium
RECRUITINGChange in Bohr dead space ventilation (VDBr/VT)
Quantified by the Bohr approach with volumetric capnography
Time frame: During FCV and VCV measurements (20 minutes)
Change in Enghoff dead space ventilation (VDEng/VT)
Quantified by the Enghoff approach with volumetric capnography
Time frame: During FCV and VCV measurements (20 minutes)
Change in physiological dead space volume (Vdfys)
Measured with volumetric capnography and Enghoff's approach
Time frame: During FCV and VCV measurements (20 minutes)
Change in airway dead space volume (Vdaw)
Measured with volumetric capnography and Fletcher's approach
Time frame: During FCV and VCV measurements (20 minutes)
Change in alveolar dead space volume (Vdalv)
As measured with volumetric capnography and Fletcher's approach
Time frame: During FCV and VCV measurements (20 minutes)
Ventilatory efficiency (VE/VCO2)
Ratio of minute ventilation to carbon dioxide output
Time frame: During FCV and VCV measurements (20 minutes)
Change in airway driving pressure (∆Paw)
Calculated as the difference between the plateau pressure (Pplat) during an inspiratory pause and the dynamic positive end-expiratory pressure (PEEP), as no expiratory hold is possible on the Evone.
Time frame: During FCV and VCV measurements (20 minutes)
Change in transpulmonary shunt fraction (Qs/Qt)
calculated with the modified Berggren equation
Time frame: During FCV and VCV measurements (20 minutes)
Change in global lung hyperdistention (hyperdistentionEIT)
Calculated from electric impedance tomography
Time frame: During FCV and VCV measurements (20 minutes)
Change in anterio-posterior distribution of ventilation on EIT (AP)
% anterior / % posterior
Time frame: During FCV and VCV measurements (20 minutes)
Change in right-left distribution of ventilation on EIT (RL)
% right / % left
Time frame: During FCV and VCV measurements (20 minutes)
Change in 4-layered distribution of ventilation on EIT
Time frame: During FCV and VCV measurements (20 minutes)
Change in centre of ventilation on EIT
Time frame: During FCV and VCV measurements (20 minutes)
Change in cardiac index (CI)
Calculated from the arterial waveform (pulse contour analysis) by the HemoSphere monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in mean arterial pressure (MAP)
Measured on a radial artery line
Time frame: During FCV and VCV measurements (20 minutes)
Change in partial pressure of arterial CO2 (PaCO2)
Measured on an arterial blood gas
Time frame: During FCV and VCV measurements (20 minutes)
Change in peak expiratory flow (PEF)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in peak inspiratory flow (PIF)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in mean airway pressure (MPaw)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in tidal volume (TV)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in respiratory rate (RR)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in minute ventilation (MV)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in inspiratory time (Ti)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in expiratory time (Te)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in ratio of inspiratory time to total breath time (Ti / Tt)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in positive end-expiratory pressure (PEEP)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in peak inspiratory pressure (PIP)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in plateau pressure (Pplat)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in static airway compliance (Caw)
Calculated as tidal volume / airway driving pressure
Time frame: During FCV and VCV measurements (20 minutes)
Change in end-tidal CO2 (ETCO2)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in global airway resistance (Raw)
As measured by the citrex respiratory monitor
Time frame: During FCV and VCV measurements (20 minutes)
Change in global airway time constant (TAUaw)
Calculated as global airway resistance x global airway compliance
Time frame: During FCV and VCV measurements (20 minutes)
Change in total energy
As calculated from monitoring data
Time frame: During FCV and VCV measurements (20 minutes)
Change in dissipated energy
As calculated from monitoring data
Time frame: During FCV and VCV measurements (20 minutes)
Change in P/F ratio
Calculated as partial pressure of arterial oxygen divided by inspiratory fraction of oxygen
Time frame: During FCV and VCV measurements (20 minutes)
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