A standard setup for a<unk>  in a hospital room. The<unk>  pushes warm, moist air (or air with increased oxygen) to the patient. Exhaled air flows away from the patient. In its simplest form, a modern positive pressure<unk>  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<unk> , with a flow valve adjusting pressure to meet patient-specific parameters. When over pressure 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.<unk> s may also be equipped with monitoring and alarm systems for patient-related parameters (e.g., pressure, volume, and flow) and<unk>  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. Modern<unk> s are electronically controlled by a small embedded system to allow exact adaptation of pressure and flow characteristics to an individual patient's needs. Fine-tuned<unk>  settings also serve to make<unk> ilation more tolerable and comfortable for the patient. In Canada and the United States, respiratory therapists are responsible for tuning these settings, while biomedical technologists are responsible for the maintenance. In the United Kingdom and Europe the management of the patient's interaction with the<unk>  is done by critical care nurses. The patient circuit usually consists of a set of three durable, yet lightweight plastic tubes, separated by function (e.g. inhaled air, patient pressure, exhaled air). Determined by the type of<unk> ilation needed, the patient-end of the circuit may be either noninvasive or invasive. Noninvasive methods, such as continuous positive airway pressure (CPAP) and non-invasive<unk> ilation, which are adequate for patients who require a<unk>  only while sleeping and resting, mainly employ a nasal mask. Invasive methods require intubation, which for long-term<unk>  dependence will normally be a tracheotomy cannula, as this is much more comfortable and practical for long-term care than is larynx or nasal intubation. Life-critical system Because failure may result in death, mechanical<unk> ilation systems are classified as life-critical systems, and precautions must be taken to ensure that they are highly reliable, including their power supply.<unk> y failure is the inability to sustain a sufficient rate of CO2 elimination to maintain a stable pH without mechanical assistance, muscle fatigue, or intolerable dyspnea. Mechanical<unk> s are therefore carefully designed so that no single point of failure can endanger the patient. They may have manual backup mechanisms to enable hand-driven respiration in the absence of power (such as the mechanical<unk>  integrated into an anaesthetic machine). They may also have safety valves, which open to atmosphere in the absence of power to act as an anti-suffocation valve for spontaneous breathing of the patient. Some systems are also equipped with compressed-gas tanks, air compressors or backup batteries to provide<unk> ilation in case of power failure or defective gas supplies, and methods to operate or call for help if their mechanisms or software fail. Power failures, such as during a natural disaster, can create a life-threatening emergency for people using<unk> s in a home care setting. Battery power may be sufficient for a brief loss of electricity, but longer power outages may require going to a hospital.
Ventilator
Respirator
Liquid ventilator
Resuscitator
Air purifier
Hypoxicator
Aspirator 
Pneumonic device