Patients with ARDS often suffer a gravity-dependent alveolar collapse, resulting in a reduction of tidal volume, residual alveolar excessive distension, and ventilator-related lung injury(VILI) induced by unreasonable ventilator setting.Prone ventilation (PPV) improves the gravity-dependent alveolar ventilation and promotes lung recruitment in the gravity-dependent area and improves lung compliance. Previous studies showed that prolonged PPV combined with low tidal volume(LTV) lung protected ventilation can significantly reduce the mortality of patients with moderate to severe ARDS.Although more than 60% of patients with moderate to severe ARDS due to COVID-19 has been widely implemented PPV,studies showed an improvement in oxygenation in patients with ARDS(the P/F radio improved by more than 20% before and after PPV) was 9-77%, that is, That is, some patients are unresponsive to PPV. In addition, some patients showed CO2 responsiveness after PPV(ventilation rate (VR) decreased significantly after PPV).The tools for monitoring the effects of PPV on ventilation and blood flow at bedside are still lacking, Electrical impedance tomography (EIT) is a non-invasive, non-radiative, real-time bedside lung imaging technique that can monitor local lung ventilation distribution. This study intends to use EIT to evaluate pulmonary ventilation, blood flow distribution and local V/Q ratio before and after PPV, as well as to monitor the changes in pulmonary physiology before and after PPV, explore the mechanism of PPV improving oxygenation by combined with the changes in oxygenation, and explore the factors that predict and affect PPV responsiveness.
Acute respiratory distress syndrome (ARDS) is presented as acute hypoxemia and pulmonary edema due to the increased permeability of alveolar capillaries. Endothelial damage injury and swelling, microthrombosis, and hypoxic pulmonary vasoconstriction can lead to low pulmonary blood vessels perfusion and even occlusion, while patients with ARDS often suffer a gravity-dependent alveolar collapse, resulting in a reduction of tidal volume, residual alveolar excessive distension, and ventilator-related lung injury(VILI) induced by unreasonable ventilator setting.Prone ventilation (PPV) improves the gravity-dependent alveolar ventilation and promotes lung recruitment in the gravity-dependent area and improves lung compliance. Besides, pulmonary blood perfusion is less affected by gravity distribution, thus the improvement of gravity-dependent alveolar ventilation can significantly reduce shunt, and lung heterogeneity and improve V/Q radio. Previous studies showed that prolonged PPV combined with low tidal volume lung protected ventilation can significantly reduce the mortality of patients with moderate to severe ARDS.Although more than 60% of patients with moderate to severe ARDS due to COVID-19 has been widely implemented PPV,studies showed an improvement in oxygenation in patients with ARDS(the P/F radio improved by more than 20% before and after PPV) was 9-77%, that is, That is, some patients are unresponsive to PPV. In addition, some patients showed CO2 responsiveness after PPV (ventilation rate (VR) decreased significantly after PPV).The tools for monitoring the effects of PPV on ventilation and blood flow at bedside are still lacking, Electrical impedance tomography (EIT) is a non-invasive, non-radiative, real-time bedside lung imaging technique that can monitor local lung ventilation distribution. By injecting hypertonic saline through a central vein catheter, we can obtain lung perfusion images to indicate local lung blood flow distribution. In addition, combined with lung ventilation images, we can evaluate the pulmonary shunt, dead space, V/Q ratio, to better clarify the physiological and pathological status of lung.This study intends to use EIT to evaluate pulmonary ventilation, blood flow distribution and local V/Q ratio before and after PPV, as well as to monitor the changes in pulmonary physiology before and after PPV, explore the mechanism of PPV improving oxygenation by combined with the changes in oxygenation, and explore the factors that predict and affect PPV responsiveness.
Study Type
OBSERVATIONAL
Enrollment
94
Union Hospital, Tongji Medical College, Huazhong University of Science and Technology
Wuhan, Hubei, China
Pulmonary ventilation perfusion(V/Q) ratio after 16 hours of PPV monitored by EIT
the V/Q radio were monitored by EIT after patients were implemented prone position ventilation(PPV) for 16h. The images of ventilation distribution were collected by EIT, and the images of perfusion distribution were collected by injected 10ml of 10% hypertonic saline through a central vein catheter during inspiratory hold or expiratory hold. The ventilation and perfusion images were analysed by specialized software to obtain the data of V/Q radio.
Time frame: 16 hours after prone position ventilation
Pulmonary ventilation perfusion(V/Q) ratio before PPV monitored by EIT before PPV
The V/Q radio were monitored by EIT before patients were implemented prone position ventilation(PPV). The images of ventilation distribution were collected by EIT, and the data of perfusion distribution were collected by injected 10ml of 10% hypertonic saline through a central vein catheter during inspiratory hold or expiratory hold. The ventilation and perfusion images were analysed by specialized software to obtain the data of V/Q radio.
Time frame: within 1 hour before preparing PPV
Pulmonary ventilation perfusion(V/Q) ratio after PPV ending 8h monitored by EIT
the V/Q radio were monitored by EIT 8 hours after prone position ventilation ending.The images of ventilation distribution were collected by EIT, and the data of perfusion distribution were collected by injected 10ml of 10% hypertonic saline through a central vein catheter during inspiratory hold or expiratory hold. The ventilation and perfusion images were analysed by specialized software to obtain the data of V/Q radio.
Time frame: 8 hours hours after prone position ventilation ending
Pulmonary ventilation distribution before PPV, PPV for 16h and 8h after PPV ending
Pulmonary ventilation distribution were monitored by EIT before PPV, PPV for 16h and 8h after PPV ending. The images of ventilation distribution were collected by EIT and analysed by specialized software to obtain the data.
Time frame: within 1hour before preparing PPV, 16 hours after and 8 hours after PPV ending
Pulmonary perfusion distribution before PPV, PPV for 16h and 8h after PPV ending
The pulmonary perfusion distribution were monitored by EIT before PPV, PPV for 16h and 8h after PPV ending. The images of perfusion distribution were collected by injected 10ml of 10% hypertonic saline through a central vein catheter during inspiratory hold or expiratory hold. The perfusion images were analysed by specialized software to obtain the data of pulmonary perfusion distribution.
Time frame: within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending
Pulmonary shunt percentage before PPV, PPV for 16h and 8h after PPV ending
The ventilation and perfusion images were analysed by specialized software to obtain the data of pulmonary shunt percentage.
Time frame: within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending
Pulmonary dead space percentage before PPV, PPV for 16h and 8h after PPV ending
The ventilation and perfusion images were analysed by specialized software to obtain the data of pulmonary dead space percentage.
Time frame: within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending
Peak pressure before PPV, PPV for 16h and 8h after PPV ending
Peak pressure data were obtained from ventilators
Time frame: Within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending
Plat pressure before PPV, PPV for 16h and 8h after PPV ending
Plat pressure data were obtained from ventilators
Time frame: Within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending
Tidal volume before PPV, PPV for 16h and 8h after PPV ending
Tidal volume data were obtained from ventilators
Time frame: within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending
Driving pressure before PPV, PPV for 16h and 8h after PPV ending
Driving pressure(DP) data were obtained from ventilators
Time frame: within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending
Static compliance(Cs) before PPV, PPV for 16h and 8h after PPV ending
Cs is equal to tidal volume divided by DP
Time frame: within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending
P/F ratio before PPV, PPV for 16h and 8h after PPV ending
P/F ratio data were obtain from arterial blood gas analysis
Time frame: within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending
Carbon dioxide partial pressure(PaCO2) before PPV, PPV for 16h and 8h after PPV ending
PaCO2 data were obtain from arterial blood gas analysis
Time frame: within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending
Ventilatory ratio(VR) before PPV, PPV for 16h and 8h after PPV ending
VR=\[minute ventilation (ml/min)×arterial partial tension of carbon dioxide (mmHg)\] / \[predicted body weight×100×37.5
Time frame: within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending
28 days mortality
Mortality of from the day of enrollment to day 28
Time frame: From the day of enrollment to day 28
Ventilator free days(VFD) within 28 days
The number of ventilator free days for patients from enrollment day to day 28, if patients died within 28 days,VFD was equal to zero.
Time frame: From the day of enrollment to day 28
Mortality in the ICU
Mortality in the ICU of all participants
Time frame: From the day of enrollment to the day of transfer from the ICU or death，up to 90 days
Length of stay(LOS)
LOS(length of stay) of hospital
Time frame: From the day of to the day of admitting to hospital to depart from the hospital or death，up to 90 days
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