This new therapeutic hypothermia device / targeted temperature management system developed by Sergei Shushunov, MD works on the principle of delivering hyper-cold air through a mechanical or manual ventilator, taking advantage of the lung’s physiology and anatomy:
- Huge surface area of about 100 to 120 m2 in adults for rapid heat transfer.
- Lungs high blood flow equal to entire cardiac output, which is exposed to hyper cold air.
- Alveolar-capillary membrane, which acts as an interface, is only 0.5 micron thin
- Non-reactivity of pulmonary vasculature during exposure to cold media.
- The ability to administer inhaled air chilled to, or below, -30° C.
The feasibility for the induction of therapeutic hypothermia using hyper-cold air mechanical ventilation is supported by the following observations:
1. Patients undergoing anesthesia for surgical procedures are prone to develop hypothermia due to changes in thermoregulation, even when ventilated by air at the room temperature. Several factors are responsible for this effect: a) Decreased metabolic rate and heat production due to immobilization and decreased brain activity. b) Skin vasodilatation, leading to enhanced heat loss due to radiation. c) Inability to develop shivering, which is a normal response to lowering body temperature. d) Lack of protective clothing or cover.
Thermoregulation in critically ill patients receiving sedatives, narcotics and neuromuscular blocking agents is not dissimilar to thermoregulation in patients undergoing general anesthesia, making critically ill patients susceptible to developing hypothermia. Accidental hypothermia is not commonly seen in operating rooms or Intensive care units, because of the widespread use of active heating devices placed in-line with mechanical ventilators or anesthesia machines. In critically ill, comatose or sedated, and mechanically-ventilated patients, replacement of the heat exchanger with an air cooling device that administers hyper-cold air may rapidly induce therapeutic hypothermia.
2. Ventilating hypothermic patients with warm air is a simple and effective method of re-warming. Since heat transfer is a bi-directional process, using hyper-cold air for ventilating will produce hypothermia.
3. Clinical observations indicate that in patients with neuroleptic malignant syndrome and malignant hyperthermia disconnection of air heating device and immersion of ventilator tubing into water tub filled with ice aids in reducing body temperature.
New physiological approach to induction of therapeutic hypothermia and new temperature management system will address all shortcomings of existing systems and methods of induction of hypothermia.
- The new Targeted Temperature Management System will be non-invasive. Practically all patients who may benefit from therapeutic hypothermia receive mechanical ventilation due to the nature of their condition. Therefore, mechanical ventilation would not become an additional invasive procedure.
- It will allow unobstructed access to the patient’s body for performing CPR or any other therapeutic or diagnostic procedures.
- New system will be compact and portable for easy transportation or mounting on a mechanical ventilator pedestal.
- New system will allow initiation of hypothermia in prehospital settings.
- New system will allow to use “compensated hyperventilation” with cold air – a process of hyperventilation with admixture of carbon dioxide in order to achieve faster cooling while maintaining normal acid-base balance.
- Early initiation of cooling will reduce time to achieving target body temperature.
- New system will be easy to operate by a minimally trained staff simply by placing it in line with the inspiratory limb of the mechanical ventilator tubing.
- New system will be used as a part of the circuit with any commercially available mechanical ventilator air heating device . This will allow microprocessor controlled redirection of air from the ventilator through a heater or a cooler, depending on set patient’s temperature parameters, making it a precise temperature management system.
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