Respiratory Mechanics Measurement of Ventilated Patients Through Low-frequency Oscillometry Technique

Respiratory Mechanics Measurement of Ventilated Patients Through Low-frequency Oscillometry Technique, an Explorative Study

Respiratory failure has historically been one of the most important causes for admittance of patients to the critical care unit. This problem was the most important reason during the COVID-19 pandemic. Following the evolution of the physiology of the lung has therefore been the number one concern during these challenging times in the intensive care unit (ICU). Respiratory oscillometry (RO) identifies the lung impedance by applying small pressure oscillations onto the breathing or ventilation. Information about the respiratory mechanics can be extracted out of this impedance, including the resistance (R) and compliance (C) of the lung. The VUB developed a robust, patient safe RO measurement protocol that delivers high quality measurements with the least possible interference with the patient's breathing/ventilation. The technique challenges current state-of-the-art techniques also aiming at identifying R and C of the respiratory system (not exclusively RO). The RO measurement protocol is in line with the technical standards of the ERS (European Respiratory Society) and has been successfully and safely tested on emulators and some parts on test subjects. The clinical investigation aims at a powered equivalence investigation between the RO measurement protocol and a standard of care dynamic compliance estimate on invasive ventilated patients. As secondary objectives, the feasibility of the RO techniques will be investigated during pressure support ventilation and the RO estimates will also be compared with other accepted respiratory mechanics estimation tools. To enable the investigation, a RO algorithm is developed, and a RO measurement extension is implemented in the DemcAir® ventilation system of Demcon. This was a fully tested ventilator that received a CE mark under the previous MDD regulation. However, Demcon, which produces ventilator parts for other commercial partners, removed the label to avoid competition with their partners. The ventilator will only execute the protocol on demand and save the data on an USB stick available in the ventilator. At any time, the RO measurement procedure can be stopped, and the ventilator will return to its initial ventilation. The USB stick is used to transport the data to a separate (VUB) laptop where the data processing is done.

Inclusion Criteria:

• intubation

• Controlled ventilation with an intention to continue controlled ventilation for the following 4 hours.

• Richmond agitation sedation scale of -4 or less

• Hemodynamically stable patient with either

  • unchanged vasopressor dose administration for at least 60 minutes before the start of the measurements
  • no vasopressor need and no vasopressor initiated within 60 minutes of measurements

• No planned intervention in the coming 2 hours

• Survival for at least 48 hours

• Protective ventilation (inspired oxygen concentration≤60%, plateau pressure ≤30 cmH2O , driving pressure≤ 15cmH2O)

• PEEP (Positive End Expiratory Pressure) ≤10

Exclusion Criteria:

• assist ventilation
• Ventilator asynchronies
• Intermittent spontaneous breathing
• nitric oxide therapy
• presence of an extra corporeal membrane oxygenation device
• Ventilation is not possible within the lower and upper inflection point of the low flow pressure volume curve.
• Unstable right heart failure
• Unstable lung embolism
• Standard of care without Sedline® or invasive arterial catheter
• Do not reanimate code of 2, 3 or 4
• Subjects who are healthy, minors, pregnant women, patients in emergency situation
• Outside the age range 18 to 84 years