Medical Ventilator Machines
A medical ventilator can be defined as any machine designed to mechanically move
breatheable air into and out of the lungs, to provide the mechanism of breathing
for a patient who is physically unable to breathe, or breathing insufficiently.
While modern ventilators are generally thought of as computerized machines,
patients can be ventilated indefinitely with a bag valve mask, a simple
hand-operated machine. After Hurricane Katrina, dedicated staff "bagged"
patients in New Orleans hospitals for days with simple bag valve masks.
Ventilators are chiefly used in intensive care medicine, home care, and
emergency medicine (as standalone units) and in anesthesia (as a component of an
In its simplest form, a modern positive pressure ventilator consists of a
compressible air reservoir or turbine, air and oxygen supplies, a set of valves
and tubes, and a disposable or reusable "patient circuit". The air reservoir is
pneumatically compressed several times a minute to deliver room-air, or in most
cases, an air/oxygen mixture to the patient. If a turbine is used, the turbine
pushes air through the ventilator, with a flow valve adjusting pressure to meet
patient-specific parameters. When overpressure is released, the patient will
exhale passively due to the lungs' elasticity, the exhaled air being released
usually through a one-way valve within the patient circuit called the patient
manifold. The oxygen content of the inspired gas can be set from 21 percent
(ambient air) to 100 percent (pure oxygen). Pressure and flow characteristics
can be set mechanically or electronically.
Ventilators may also be equipped with monitoring and alarm systems for
patient-related parameters (e.g. pressure, volume, and flow) and ventilator
function (e.g. air leakage, power failure, mechanical failure), backup
batteries, oxygen tanks, and remote control. The pneumatic system is nowadays
often replaced by a computer-controlled turbopump.
For any Medical Ventilators not listed here, please do not
hesitate to call