The Glossary contains terms commonly associated with ventilators, the community, and respiratory physiology. Click on a hyperlinked letter to view the entries that begin with that letter, then scroll down in the window to find the word you are looking for.

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Assist/Control Mode of Ventilation – Ventilator operation in which a machine breath is delivered when an inspiratory effort by the patient is sensed by the ventilator (Assist), or at set time intervals if the rate of occurrence of inspiratory efforts falls below a set rate (Control).
Alternating Current having standard frequencies of 60 Hz in North America and possibly other frequencies in other locations internationally.
Airway Pressure (Paw)
Pressure at a specified point in the patient’s airway.
Airway Pressure Release Ventilation
Airway Pressure Release Ventilation (APRV) is a mode of ventilation that provides two levels of CPAP and allows spontaneous ventilation at both levels. APRV is different from other modes of ventilation in that it based on an intermittent decrease in airway pressure, rather than an increase, to provide ventilation. Source: RT Corner, click here for full description.
A means of alerting the operator that a specified abnormal condition exists; examples: high pressure alarm, apnea alarm.
Alveolar Pressure (PA)
Representative pressure in the alveoli.
Alveolus (p. alveoli)
Termination of the airways in the lungs; primary site of gas exchange with the blood.
pertaining to data in the form of continuously variable physical qualities in contrast to digital data represented in discrete form.
Anatomical Dead Space
the volume of the airways filled with inspired gas that does not take part in gas exchange with the blood during normal breathing.
A device that measures flow by its cooling of a heated element.
Cessation of breathing
Assist Mode
Ventilator operation in which an machine breath is delivered only when an inspiratory effort by the patient is sensed by the ventilator.
Assist/Control Mode
(See A/C.)
American Society for Testing and Materials: A scientific and technical organization formed for the development of standards on characteristics and performance of materials, products, systems, and services. The following published ASTM standards pertain to ventilators and mechanical ventilation:
ASTM F 1246-91
Electrically Powered Home Care Ventilators, Part 1 – Positive-Pressure Ventilators and Ventilator Circuits
ASTM F 896-90 (1995)
Flexible Fiberoptic Bronchoscopes
ASTM F 920-93
Minimum Performance and Safety Requirements for Resuscitators Intended for Use with Humans
ASTM F 927-86 (1994)
Pediatric Tracheostomy Tubes
ASTM F 965-85 (1993)
Rigid Laryngoscopes for Tracheal Intubation – Hook-on Fittings for Laryngoscope Handles and Blades with Lamps
ASTM F1100-90 (1997)
Ventilators Intended for Use in Critical Care
ASTM F1195-88 (1993)
Rigid Laryngoscopes for Tracheal Intubation – Hook-on Fittings for Fiberilluminated Blades and Handles
ASTM F1242-96
Tracheal Tubes, Cuffed and Uncuffed
ASTM F1243-89 (1995)
Tracheal Tube Connectors
ASTM F1415-92
Pulse Oximeters
ASTM F1456-89
ASTM F1462-93
Oxygen Analyzers
ASTM F1493-93
Alarm Signals In Medical Equipment Used in Anesthesia and Respiratory Equipment
ASTM F1590-92
Tracheostomy Tube Connectors
ASTM F1627-95
Tracheostomy Tubes – Pediatric Tracheostomy Tubes
ASTM F1666-95
Adult Tracheostomy Tubes
Automatic Tube Compensation (See Automatic Tube Compensation)
Auto Positive End-Expiratory Pressure (also Inadvertent PEEP) – Residual alveolar pressure above the preset baseline pressure at the end of expiration caused by the occlusion of airways and the consequent trapping of gas behind the occlusions.
Unintended, repeated delivery of machine breaths caused by the dropping of pressure in the patient circuit below the pressure trigger point. This typically occurs if the trigger point (sensitivity) is set too high, or if the circuit cannot hold pressure at the end of exhalation.

AutoFlow is a ventilator feature pioneered by Draeger Medical that changes the control strategy for a volume-controlled breath to a pressure controlled breath under the constraint that the breath reaches the operator-set volume. It is defined as delivering a volume-targetted, pressure-controlled breath. In AutoFlow, the ventilator uses algorithms to try to determine the right peak pressure that will allow the set volume to be delivered with the minimum pressure. AutoFlow is a registered trademark of Draeger Medical.

Automatic Tube Compensation
A means by which that portion of the work of breathing associated with the movement of gas through an endotracheal or tracheostomy tube (connecting the breathing circuit to the patient’s airway) is reduced or eliminated by the ventilator with no, or minimal, intervention by the operator (care giver).