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Master Thesis HES-SO en Engineering
Pressure Activated Synchronizer of Nebulizing Therapy in BPAP
Artificial Ventilation
Rares Rusu
Supervised by: Prof. Dr. Med. Enrico Maria Staderini
HEIG-VD
In collaboration with: HESAV
DESCRIPTION
RESULTS
Administrating pharmaceuticals using the aerosol therapy generated by nebulizer is
gaining new ground in treating respiratory diseases. The nebulized treatment is developing and
new drugs intended for this method of care are demanding new ways of aerial administration.
The mechanical ventilation is often used for the patients with respiratory problems and the
combination with a nebulizer is quite common. Non-invasive bi-level ventilators are used as the
launching ramp for the pharmaceutical compound right to the place where the patient needs.
These kind of medical devices are generally equipped with a single limb circuit with integrated
exhalation port device which allows CO2 evacuation. It forms a continuous leak port and hence
the loss of nebulized drug in the ambient air can potentially decrease the exact dose of the drug
that the patient receives. Unfortunately the exact quantity of the medicine reaching the patient is
quite unpredictable because of the losses in the pipe and in the environment. The situation is
even worst in combined ventilation/nebulization systems. The nebulizing devices used in noninvasive positive pressure ventilation (NIPPV) have the disadvantage of continuously nebulizing
the drug which implies that the pharmaceutical compound will not be transferred to the patient in
a reliable way. A breath-synchronized nebulization option can be implemented to greatly improve
the therapeutic delivery.
A series of tests and researches have been done regarding the drug administration in
NIPPV and until now the efficiency of using a certain type of nebulizer in different kind of
diseases is still doubtful. Furthermore, the optimal position of the nebulizer in the system and its
type is still unknown.
The intermittent synchronized inspiration nebulization is in principle a great improvement
for this type of therapy. By using an advanced nebulizer based on vibration mesh, a pressure
actuated synchronization system to inject nebulized drug only during the inspiration phase of
breath was developed.
The achievement of the synchronization inside the experimental setup was based on
receiving, following and transforming the electrical signal acquired from the pressure sensor,
using the electrical characteristics of the parts composing the new invented electronic device.
The purpose of the electronic device is to achieve through its function the mode of operation
in which the nebulizer is functioning in the moment of inspiration produced by the test lung.
The triggering of the inspiration phase produced by the artificial lung will automatically bring
a variation of the pressure inside the tubes. This modification will be sensed by the pressure
sensor which will send a signal to the main board of electronics. At this point the signal is
evaluated and in function of the position of the switches will automatically activate the function of
the nebulizer. Thereby, the pharmaceutical compound will be released only in the moment of
inspiration, realizing in this way the synchronization between the nebulizer and the respiration
process.
Titre de la figure
OBJECTIVES
The purpose of the project is to synchronize the medical device nebulization unit with the
patient respiration, in a way that the drug is only administrated at the inspiration phase (IPAP).
An experimental setup and an electronic system have been developed for testing the
benefits of administrating nebulization therapy with positive airway bi-level ventilator in a
synchronous way with the patient breathing.
The system can nebulize all the approved drugs for treating respiratory diseases and can
be used in different environments like ICU, hospitals or for home treatment, from infant to adult
patients.
Experimental setup
Evolution of the electrical signal in the customized main board of electronics
To realize the measurements the nebulizing device was inserted in the same system in
which the ventilator and the artificial lung were coupled. The custom electronics was already
embedded in the control unit of the nebulizer.
To test the synchronization of the nebulizer with the respiration imposed by the artificial
lung, means to compare the electrical signals emitted by the pressure sensor positioned at the
entrance in the experimental device and the electrical signal received by the nebulizer unit.
The comparison of the two signals was made by the instrumentality of an oscilloscope. The
image on the device shows that the two signals are evenly matching and the time delay between
the signals from the pressure sensor and the signal received by the nebulizer unit is almost
viewless, around 0.2 seconds.
Comparison between the signal emitted by the pressure sensor and the signal
received by the nebulizer unit
CONCLUSION
The purposed goal of the project was achieved. Obtaining a new way of administrating the nebulizing therapy can transform the process in a more efficient operation that will bring a big
advantage for the patients suffering of respiratory diseases. Along with the achievement of the synchronization other important functions for the new appliance were developed. Starting from the
base function through which the device was nebulizing continuously the medicament, other two operational modes were added: the nebulization in the moment of expiration (at EPAP) and the
possibility to stop the nebulizer without unplugged it from the power source. These four operational modes can be used in both BPAP and atmospheric environments. The insertion of the custom
main board of electronics in the control unit of the nebulizer and the use of the switches intended to ease the modality of accessing all the modes of running the nebulizer, changed the design of
the device and also its operational way. Furthermore, the custom electronics inside the control unit of the nebulizer means an ergonomic appliance that will keep the maneuverability and sizes of
the original device. The nearest future of the new nebulizer means subjecting the device to the measurements into the medical environment, using pharmaceutical compounds and in vivo testing.