An interventional study of Pressure Support Variation and Calculation of Respiratory Mechanics in Asynchrony, Patient-Ventilator, ARDS and Respiratory Insufficiency, sponsored by University of Sao Paulo General Hospital. Recruiting at 1 site in Brazil. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2024-07-10.
Sponsored by University of Sao Paulo General Hospital · Not applicable, Interventional, and Diagnostic
The Pendelluft phenomenon is an important cause of lung damage in spontaneously breathing mechanically ventilated patients since it considerably increases the stress on the lung parenchyma in the dependent areas. It can result in a local driving pressure up to three times higher than the global driving pressure. The measurement of Pendelluft is still uncertain in the literature, and although various methods have been proposed, not all have the same meaning in terms of pulmonary overstress and overstrain. This study proposes a comparative analysis of different ways to calculate and estimate the stress imposed on the lung parenchyma by Pendelluft in terms of regional volume and local driving pressure through electrical impedance tomography.
Respiratory mechanics and regional ventilation will be monitored by electrical impedance tomography (Enlight 1800 and 2100, Timpel). Esophageal and gastric pressures will be obtained by placing an esophageal/gastric balloon cathether (Nutrivent ®), validation concerning position will be done through modified Baydur maneuver (delta esophageal/delta airway pressure = 0.8-1.2). The hardware Pneumodrive will be used to inflate the balloon and store the airway, gastric and esophageal pressures.
Initially the patients will be monitored with EIT for aproximately 30 minutes after pletismography stabilization. Then, an arterial blood-gas sample shall be collected for analysis. Next, three expiratory and three inspiratory pauses of at least two seconds will be realized with intervals of eight respiratory cycles between them, allowing plateau pressure to be recorded and global and regional driving pressure to be estimated. All this data will be stored for later analysis. The same procedures and measurements shall be made sequentially with a 50% higher pressure support and with a 50% lower pressure support.
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Exclusion Criteria:
Patients shall be submitted to pressure support variation in a randomly assigned manner. First 30 minutes after plethysmogram stabilization shall be recorded at clinical pressure support. Next, a blood gas sample shall be collected by a nurse or a physician, and three inspiratory pauses of at least 2 seconds shall be performed in between eight respiratory cycles. Next three expiratory pauses shall be performed in between eight respiratory cycles. All data shall be recorded and analysed offline. Subsequently the same sequence of events shall be performed at a 50% higher pressure support and at a 50% lower pressure support. The sequence in which this will happen shall be randomly assigned (first lower PS vs higher PS or first higher PS vs lower PS).
Other: Pressure Support Variation and Calculation of Respiratory Mechanics
Patients will be submitted to different levels of pressure support (PS) in a randomly assigned order. First 30 minutes shall be recorded at the clinical PS. Next, blood gas samples shall be collected. Subsequently, three inspiratory pauses of at least 2 seconds shall be performed with an interval of at least 8 respiratory cycles between them. The same shall be performed with three expiratory pauses. Next, the PS shall be varied to 50% less or 50% more than clinical PS (based on randomization) and the same procedures shall be performed after 30 minutes of data recording (blood gas sample collection, inspiratory and expiratory pauses). All data shall be analyzed offline using a software that will be able to compare three different methods to calculate Pendelluft magnitude based on the literature. After completion of the protocol, ventilatory parameters shall be returned to the original settings. If the patient becomes tachypneic during lower PS, the protocol shall be interrupted.
1. Magnitude of Pendelluft
Three differents methods of estimating magnitude of Pendelluft shall be compared using a software based on electrical impedance tomography monitoring (Enlight 2100, Timpel Medical®, Brazil)
Time frame: During 30 minutes after plethysmogram stabilization at clinical PS, during 30 minutes at 50% lower PS, and during 30 minutes at 50% higher PS
2. Magnitude of Pendelluft during inspiratory pause
One of the methods of Pendelluft measurement shall be performed during an inspiratory pause for comparison with a normal cycle (without pause).
Time frame: During 30 minutes after plethysmogram stabilization at clinical PS, during 30 minutes at 50% lower PS, and during 30 minutes at 50% higher PS
3. Magnitude of respiratory effort
Respiratory effort shall be estimated through expiratory pauses and though recording of esophageal pressure at different pressure support levels. These data shall be compared to Pendelluft magnitude according to the different methods of calculation
Time frame: During 30 minutes after plethysmogram stabilization at clinical PS, during 30 minutes at 50% lower PS, and during 30 minutes at 50% higher PS
Plan to share: No
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University of Sao Paulo General Hospital