Apparatus and method for monitoring an airway device such as an endotracheal tube
An airway device ( 14 ), that is used to maintain a clear airway in a patient, e.g. for artificial ventilation during surgery, comprises an inflatable cuff ( 26 ), which is inflated when in position in a patient's airway ( 24 ). The inflated cuff ( 26 ) provides a seal to maintain the device ( 14 ) in position in a patient's airway ( 24 ), and to prevent leakage of infected oropharangeal secretions into the patient's lungs. A method and apparatus ( 10 ) for monitoring and controlling the pressure in the inflatable cuff ( 26 ) is described, which, in one embodiment, controls the pressure about a setpoint pressure, while preventing loss of sealing pressure during a patient's respiratory cycle. In other embodiments, the method and apparatus monitors for: leaks in the pressure system of the device ( 14 ) that includes the cuff ( 26 ); blockage in the pressure system, and/or malpositioning of the airway device ( 14 ) during use.
1. A method for adjusting a pressure of an inflatable seal of an airway device when a difference between a received pressure value and a preselected, desired pressure value is greater than a predefined tolerance defined by oscillations in pressure about the preselected, desired pressure value corresponding to a typical respiratory cycle of a patient, the method comprising:
changing the pressure of the inflatable seal using a motor controller and motor driver to reduce the difference over a time period that is equal to or is greater than the typical respiratory cycle of the patient, such that a rate of change is proportional to:
(
(
P
1
-
S
)
2
*
S
)
(
R
)
Where:
P 1 the pressure value indicative of the pressure of the inflatable seal
S is the preselected, desire pressure value
* is a multiplier operation
R is a regulation constant.
2. The method of claim 1 , wherein the step of changing the pressure is carried out at a rate that is further limited to a predetermined threshold rate.
3. The method of claim 1 , wherein the step of changing the pressure comprises driving a piston through a cylindrical bore of a syringe in communication with the inflatable seal.
4. The method of claim 1 , wherein the received pressure value is received periodically at predefined time intervals.
5. The method of claim 4 , wherein the predefined time intervals are in the range of 0.1 to 2.0 seconds.