Low-frequency respiratory oscillometric measurements during mechanical ventilation

Respiratory oscillometry (RO), applied during ventilation of patients, allows the identification of relevant mechanical properties of the respiratory system. RO during ventilation is not a standard-of-care measurement technique since the identified parameters are currently not equivalent to the parameters identified via standard-of-care techniques such as the low-flow PN loop. This paper presents a novel RO setup that identifies the same respiratory mechanical parameters as the standard-of-care techniques. The setup is a blower-based ventilation device where the requested ventilation is combined with a specifically designed low-frequency multisine excitation signal. The excitation design protocol takes the ventilation limitations into account to ensure the measurement quality. Validation measurements on an emulator are provided to evaluate the performance of the proposed techniques. The emulator is measured via the novel RO setup as well as via three standard-of-care measurement techniques. The measurements showed that the same parameters could be identified with a better accuracy than the common oscillometric standard of 10%. The estimated values and their coefficient of variation were compared against each other and showed that the RO setup is a qualitative alternative to the standard-of-care techniques with the clinical advantages of being patient friendlier, easier to use and less disturbed by patient activity.