Medical Ventilators

Medical ventilators enable patients who cannot breathe on their own by alternately forcing air—either ambient air or a mixture of air and oxygen--into their lungs mechanically.
Ventilators are also used for patients whose breathing is insufficient or inconsistent. As systems that are often life-critical, ventilators are designed with redundant power supply options, safety valves and other features that safeguard patients in the event of mechanical or power failure.

Ventilators range from hand-operated bag valve masks to sophisticated computer-controlled respirators. A variety of models are available for settings that include emergency rooms, intensive care units, extended care units, nurseries and home healthcare. Ventilators are also integrated in anesthesia machines for use in operating rooms.

Most ventilators work on the positive pressure principle. An air reservoir is alternately compressed and expanded several times each minute, delivering air to the patient. In some ventilators, a turbine and flow-valve assembly is used instead of a compressible reservoir. The flow valve enables the air pressure to be adjusted for each patient, as needed. Because lungs are naturally elastic, once the positive pressure is reduced, patients exhale without mechanical assistance. Exhaled air is channeled through a separate circuit called a patient manifold. An oxygen source, and various valves and tubes complete the basic ventilator assembly.

Today, many ventilators include monitors that measure pressure, volume and flow as well as alarms that alert the patient or caretakers to changes in these parameters or to ventilator malfunctions or failure. In most modern ventilators, computer operated turbo-pumps have replaced pneumatic systems that were historically used to compress the air reservoir.

Many patients with respiratory conditions, head injuries and cardiac failure cannot breathe effectively on their own and require ventilation on a sporadic or ongoing basis. Ventilators are also used to prevent anoxia in patients who are anesthetized during surgery. Depending on the severity of the patient’s condition, the expected duration during which ventilation will be needed, and other factors, a breathing tube may be inserted into the patient’s airway or a tracheotomy may be performed so that the ventilator can be connected to a tracheotomy tube.

Companies that produce ventilators include Siemens Maquet, GE Healthcare, Viasys Healthcare, Intersurgical, Datex-Ohmeda, Drager-Narkomed, Newport Medical, Pulmonetic, Penlon Intermed and Puritan Bennett.