Introduction:
Grave diaphragm dysfunction often leads to respiratory failure resulting in a permanent need for mechanical ventilation. Mechanical ventilation is used to assist breathing in patients for whom involuntary breathing is impossible or is minimal. However, using a mechanical ventilator is associated with several discomforts and problems. Even though mechanical ventilation aids breathing, tethering to the machine through mouth or tracheostomy (opening in the trachea to insert a tube) affects the patient's swallowing ability, speech, and mobility.
Research on animal models with respiratory insufficiency shows that a soft robotic, contractile actuator, when implanted in the diaphragm, helps in its motion facilitating breathing. The robotic ventilator on the diaphragm is pre-synchronized to a normal range with native respiratory efforts, tidal volumes, and ventilation flow rates. The device acts at the diaphragm level and not at the upper airway and augments the physiological breathing process without compromising the quality of life.
What Is an Implantable Ventilator?
An implantable ventilator is a new conceptual design developed by engineers at the Massachusetts institute of technology (MIT) to boost the life-sustaining function of the diaphragm and improve the lung capacity in patients with diaphragm dysfunction.
What Are the Mechanics and Workings of an Implantable Ventilator?
Two long, soft, inflatable balloon-like tubes are located in the device's heart, implanted over the diaphragm from back to back, and are attached to the ribcage on either side of the diaphragm. The inflatable tubes are pneumatic devices called McKibben actuators (artificial air muscles that are lightweight, easy to fabricate, and self-limiting). When these tubes are inflated with an external pump, they perform the function of artificial muscles that pushes the diaphragm downwards. The downward movement of the diaphragm will expand the lungs and create a vacuum that will draw air into the lungs, thus helping to breathe. One end of each tube is connected to an external airline connected to a device with a small pump and a control system. The pump will inflate the tubes in the frequency of the diaphragm's contractions. The inflation of the tubes is synchronized in such a way that they match the natural rhythm of the diaphragm.
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The research for implantable ventilators was performed on animal models by the engineers of the Massachusetts institute of technology, and the results depicted that in animals with significant diaphragm defects, the device could restore breathing back to the normal range.
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However, the current studies and evidence are insufficient to use implantable ventilators to treat human diaphragm dysfunction.
How Was the Implantable Ventilator Developed?
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Ellen Rosche, associate professor and a member of the institute for medical engineering and technology and a team of engineers at Massachusetts Institute of Technology, devised the conceptual design of the implantable ventilator based on her previous work of a cardiac sleeve around the heart to decrease the pressure and provide support as the heart pumps blood. Experimental studies on implantable ventilator design began much before the COVID-19 pandemic when there was a spike in the use of conventional mechanical ventilators. The mechanical ventilator creates positive pressure in the patient's airways, facilitating airflow from the external environment into the patient's lungs.
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However, the diaphragm works by creating negative pressure. When the muscle contracts, it moves downward, giving space for the lungs to expand; this will create a negative pressure inside the chest cavity that will suck in the air from the external environment into the lungs.
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Using the principle of negative pressure, Roche and the team of engineers designed a negative-pressure ventilator that will augment the natural functioning of the diaphragm, particularly for patients with chronic breathing difficulties due to diaphragm dysfunction.
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They aimed to help chronically ill people with degenerative nerve and muscle diseases with breathing problems.
What Were the Animal Studies Conducted for Implantable Ventilators?
Engineers at the Massachusetts institute of technology conducted tests on porcine models to evaluate the efficacy and outcomes of the conceptual design of implantable ventilators. The tests were performed on anesthetized pigs. Some tests are performed on the animals initially to obtain physiological data, such as the respiratory flow volumes and the pressure within the respiratory system. The physiological data were input into the device's high-resolution data acquisition control system. The tubes are then inflated with the pump attached to the high-resolution data acquisition control system.
The implantable ventilator was attached to the pig's diaphragm, and the end of the tubes was connected to the ribcage on either side of the diaphragm. The animal's oxygen level and the functioning of the diaphragm were monitored throughout the test using ultrasound imaging.
What Were the Results of the Animal Study?
From the research, it was observed that, in general, the implanted device increased the animal's tidal volume (the amount of air the lungs can take in every breath). Significant results were observed when the diaphragm's contraction and the tubes' inflation occurred concomitantly. In such cases, the lungs could draw in three times the air they would draw without the assistance of an implantable ventilator.
Some animals in the experiment presented marked changes in tidal volume, peak inspiratory pressure, and minute ventilation. The large augmentation in the variables was specifically due to the soft robotic implanted ventilators augmenting the inspiratory function of the diaphragm. However, the response was not uniform throughout the sample of animals studied, showing variation to some extent.
What Are the Future Goals and Challenges for the Implantable Ventilator?
The team has developed a device with a conceptual design, and its use has yet to come to human patients. The goal is to optimize various aspects of the device to implement it in human patients with chronic diaphragm dysfunction and improve the quality of their life. The vision involves the miniaturization of various parts of the system. The pumps and control system could be modified to be worn as backpacks, belts, or even fully implantable.
Conclusion
The implantable ventilator is a breakthrough in the field of assisted ventilation when compared to the use of invasive mechanical ventilation. The device assists breathing and can be compatible with the voluntary use of the diaphragm instead of the complete takeover of breathing function. The quality of life is preserved with an implantable ventilation strategy. In addition, it can avoid the potential complications of mechanical ventilation like barotrauma or hemodynamic changes in concomitant cardiac patients. The future goal is to optimize various aspects of the device to implement its use in human patients.
