A method for non-invasive detection of vascular endothelial dysfunction using ultrasonic imaging is provided. The pistons in each cylinder operate to open its exhaust port or ports before its intake port or ports and to close its exhaust port or ports before its intake port or ports. The heater unit is switched on when the sensor temperature is equal to or lower than a first threshold, and is switched off when the sensor temperature is equal to or higher than a second threshold. A retardation region is defined by each first electrode stripe and one second electrode stripe. More particularly devices and methods are directed maintaining patency of channels that alter gaseous flow within a lung to improve the expiration cycle of, for instance, an individual having chronic obstructive pulmonary disease.