Mechanical Ventilation Complication, Ventilator-Induced Lung Injury
Conditions
Keywords
electrical impedance tomography, expiratory time constant, mechanical energy, lung protective ventilation, ventilator-induced lung injury, expiratory flow, inspiratory hold maneuver
Brief summary
The aim of this study is to collect synchronized data from multiple monitoring techniques of mechanical ventilation (pressure/flow waves from the ventilator, electrical impedance tomography - EIT, esophageal pressure, capnography) in patients ventilated either on intensive care units or during anesthesia and evaluate the data by detailed mathematical analysis, to test three hypotheses: 1. Various published methods of calculation of the expiratory time constant provide different results in most cases. 2. Inhomogeneous ventilation (as described by EIT) affects the form of the expiratory flow curve and thus the calculated expiratory time constants. 3. The calculation of mechanical energy transferred to the lungs is affected by the chosen technique and length of the inspiratory pause maneuver. This study does not test any new or non-standard methods and does not in any way interfere with the course of treatment indicated by the clinician, apart from extending the monitoring techniques.
Detailed description
Mechanical ventilation is known to cause various complications, generally known as ventilator induced lung injury. Thus, detailed monitoring is essential. However, data interpretation is complicated in clinical practice. The investigators aim to collect synchronized data from multiple monitoring techniques of mechanical ventilation (pressure/flow waves from the ventilator, electrical impedance tomography - EIT, esophageal pressure, capnography) in patients ventilated either on intensive care units or during anesthesia and evaluate the data by detailed mathematical analysis. The results will be used to explore the complexity of seemingly simple and often used calculations describing the course of mechanical ventilation - mostly the expiratory time constant and amount of mechanical energy transferred to the lungs. The investigators primarily aim to test three hypotheses: 1. Various published methods of calculation of the expiratory time constant provide different results in most cases. 2. Inhomogeneous ventilation (as described by EIT) affects the form of the expiratory flow curve and thus the calculated expiratory time constants. 3. The calculation of mechanical energy transferred to the lungs is affected by the chosen technique and length of the inspiratory pause maneuver. For this, the investigators plan to recruit 50 patients undergoing general anesthesia with controlled mechanical ventilation and 50 patients hospitalized on intensive care units. Monitoring of those patients will be protocolized and will in all cases include pressure/flow monitoring of the mechanical ventilator, capnography, and electrical impedance tomography. Esophageal pressure monitoring will be introduced where indicated by the clinician or where nasogastric tube insertion will be indicated (as the pressure can be measured by a combined catheter). This study thus does not test any new or non-standard methods and does not in any way interfere with the course of treatment indicated by the clinician, apart from extending the monitoring techniques. Patient data will be anonymized and all the enrolled patients or their families will sign an informed consent as agreed by the ethical committee of our hospital.
Interventions
EIT is rarely used during general anesthesia for standard procedures. In the anesthesia arm, all patients will be monitored by EIT.
Sponsors
Study design
Intervention model description
The study will be conducted on patients provided with mechanical ventilation either on intensive care units or during anesthesia. Extended monitoring of ventilation, including electric impedance tomography and esophageal pressure readings will be applied.
Eligibility
Inclusion criteria
* mechanical ventilation for anesthesia or in intensive care unit
Exclusion criteria
* disagreement with enrollment or incapacity to understand the patient information leaflet * contraindications to electric impedance tomography (skin lesions in the place of electrode placement etc.) * necessity to use a defined ventilator setting outside the study protocol
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Expiratory time constant | 2 minutes after an intervention or a change in the ventilator settings | Time \[in seconds\], in which the lungs exhale 63% of the total volume. |
| Mechanical energy transferred to the lungs | 2 minutes after an intervention or a change in the ventilator settings | Mechanical energy (alternatively referred to as mechanical work) \[in Joules\] is the energy delivered to the respiratory system during a single inspiration cycle. |
Other
| Measure | Time frame | Description |
|---|---|---|
| Regional signals of electrical impedance tomography | 2 minutes after an intervention or a change in the ventilator settings | Changes of regional signals of electrical impedance tomography throughout the respiratory cycle correspond to changes in lung aeration. |
Countries
Czechia