Optimizing the Assessment of Mechanical Ventilation by Integrating Advanced Monitoring Techniques [AVIM]

Optimizing the Assessment of Mechanical Ventilation by Integrating Advanced Monitoring Techniques

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.

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.

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