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mechanical vent

definitions

QuestionAnswer
Abdominal pressure pressure within the abdominal space. This is often used as a reference to intrathoracic pressures in order to calculate transdiaphragmatic pressures. This pressure is commonly measured in either the gastric space or the urinary bladder.
Absolute humidity the amount of water vapor present in a gas mixture. Typically expressed in mgH2O/L.
Active heat and moisture exchanger a device that combines a passive humidifier and a heated heated humidifier to reduce water usage and increase moisture output.
Acute respiratory distress syndrome (ARDS) a severe pulmonary inflammatory response to a variety of insults, resulting in capillary leak, interstitial edema, intrappulmonary compliance, decreased ventilation-perfusion matching, and progressive hypoxemic respiratory failure.
Active expiration expiration assisted by ventilatory muscles.
Adaptive support ventilation a mode of ventialry support in which the ventilator can choose ventilator settings following the input of patient weight and % minute volume. The ventilator operates in the pressure control and pressure support modes and can change I:E during mandatory br
Air trapping see intrinsic PEEP. This is sometimes also called "occult" PEEP. End-expiratory pressure in the lung as a consequence of excessive minute ventilation, and inadequately set expiratory time or airway obstruction preventing lung emptying. Intrinsic PEEP is s
Airway anatomy the anatomic structures in the head, neck, and thorax through which ventilation occurs.
Airway pressure pressure in the airways of the lung, often assumed to be identical to ventilator circuit problems.
Airway pressure release ventilation (APRV) a respiratory support pattern that provides a moderately high level of continuous airway pressure that is interspersed with brief deflation (release) periods. Spontaneous breaths can occur throughout the ventilatory cycle.
Alarm a visual and /or auditory signal that occurs when a monitored parameter has exceeded a set limit.
Alarm event any condition or occurrence that triggers an alarm and requires clinician awaresness or action.
Alternate care sites sites of care for mechanically ventilated patients that are outside the acute care hospital. Exampes include long-term facilities, skilled nursing facilities, and the home.
American Heart Association device classification system the system by which devices used during cardiopulmonary resuscitation are classified based on usefulness and possibility of doing harm. This system includes the following: Class I-A therapeutic option that is usually indicated, is always acceptable, and
Antibiotics chemical angents that kill micro-organisms or inhibit heir growth.
APACHE an acronym for the Acute Physiologic and Chronic Health Evaluation Score. It represent a simple scoring system used to predict outcome.
ARDS an acronym for the acute respiratory distress syndrome. This syndrome is characterized by an acute lung injury produing a noncardiogenic edema, bilateral chest X-ray infilitrates and severe hypoxemia.
Aspiration describes the introduction of oral, nasal, pharyngeal, or gastric contents into the lung.
Assessments for ventilator withdrawal a series of clinical observations and physiologic measurements designed to determine the potential for patients to be withdrawn from mechanical ventilation.
Assisted expiration expiratory flow generated by a negative change in transrespiratory pressure due to an external agent (such as a drop in airway pressure below baseline).
Assisted inspiration inspiratory flow generated by a positive change in transrespiratory pressure due to an external agent (such as a rise in airway pressure above baseline).
Assisted ventialtion the process of providing a positive pressure breath in response to a patients inspiratory effort.
AutoPEEP see intrinsic PEEP. This is sometimes also called "occult" PEEP. End-expiratory pressure in the lung as a consequence of excessive minute ventilation, and inadequately set expiratory time or airway obstruction preventing lung emptying. Intrinsic PEEP is
Bag valve resuscitator consists of a self-inflating bag, oxygen reservoir, and non-rebreathing valve. The operator ventilates the patient by squeezing the self-inflating bag, which forces air into the non-rebreathing valve and to the patient. The self-inflating bag is typicall
Barotrauma/volutrauma injury to the lung due to excessive pressure andor volume in the lung.
Barrier device a flexible sheet that typically contains a vlave and/or filter separating the rescuer from the patient.
Basic airway management procedures to maintain a patent airway without the use of an endotracheal tube.
Bernoulli's principle the physical principle of a lowered pressure around a moving fluid or gas.
Broncho-alveolar lavage the prcedure whereby distal regions of hte lung are washed with fluid for the purpose of obtaining samples for diagnosis.
Bronchodilator a drug that expands the lumina of the air passages of the lungs.
Bubble humidifier a humidifier that imparts heat and moisture to gas as it is released under the surface of the water and "bubbles" to the surface.
Calcium chloride a hygroscopic chemical substanc that enhances the heat- and moisture- exchanging capabilities of the passive humidifier.
Cardiopulmonary interactions the interactions of changes in intrathoracic pressures and volumeson cardiovascular function.
Cascade humidifier a typer of bubble humidifier that uses an underwater grid to increase the gas/liquid interface and increase humidity.
Chronic obstruction pulmonary disease (COPD) a disease process involving chronic inflammation of the airways. Variants include chronic bronchitis (disease predominance in the large airways) and emphysema (disease predominance ing the smaller airways and alveolar regions).
Closed ciruit suction catheter a suction catheter designed to be used in-line with the ventilator circuit so that the ventilator does not need to be disconnected. Closed circuit suctioning has been associated with fewer complications than traditional suctioning techniques.
Closed-loop control a control scheme in which the actual output of a system is measured and compared with the desired output. If there is a difference caused by external disturbances, the actual output is modified to bring it closer to the desired output.
Coloimetric CO2 detector a device which detects the presence of carbon diaoxide in expired gas and indicates the presence of CO2 by changing color (usually yellow to purple).
Compliance the relative ease at which a body or tissue stretches or deforms.
Compressible volume the volume of gas that distends the ventilator circuit during delivery of a positive pressure breath. This volume is considered "lost," as it is not deliered to the paitent.
Compressor a device that is designed to copress a gas (usually air).
Condensation water that collects in the ventilator circuit as gas cools when the amount of water vapor present exceeds the carrying capacity of the gas.
Constant positive airway pressure (CPAP) a therapeutic modality that maintains a constant transrespiratory pressure. CPAP is not a ventilatory mode because it does not genterate a tidal volume.
Control circuit the ventilator subsystem responsible for controlling the drive mechanism and/or the output control valves.
Control variable the variable (either pressure, volume, flow, or time)that the ventilator manipulates to cause inspiration. This variable is identified by the fact that its behavior remains consistent despite changes in ventilatory load.
Convective gas transport gas transport that moves O2 and CO2 in discrete volumes (bulk flow").
Cricoid pressure pushing sown on the cricoid membrane, thereby collapsing the esophagus against the cervical vertebrae. Cricoid pressure has been shown to prevent gastric insufflation during mask ventilation.
Cricothyroidotomy the procedure whereby an airway is obtained through the crycothyroid membrane into the trachea.
Cuff pressure the pressure exerted by the tracheal tube cuff on the airway mucosa.
Cycle to end a mechanically supported inspiration.
Cycle time the duration of the delivery of gas under positive pressure during inspiration until a cycle criterion is met.
Cycle synchrony dead space. The process of matching the ventilator breath termination to the terminatinoof the patient;s effort during interactive breaths.
Dead volume volume of medication in a nebulizer that cannot be aerosolized due to device construction.
Demand valve a valving system in a mechanical ventilator that responds to a patient effort.
Density the quality of being compact or dense.
Dual control modes of ventilation whereby two or more variables may contro breath delivery depending upon certain circumstances.
End-expiratory pressure (EEP) the baseline transrespiratory pressure that exists at the end of the expiratory time. This pressure is often positive (PEEP).
End-expiratory valve a mechanical valve that regulatespressure during the expiratory phase.
Endotracheal tube an artificial airway passed through the nose or mouth past the vocal cords and into the trachea.
End points measurements used to determine safety and efficiency.
Engineering assessment techniques to assess the mechanical performance of a device.
Esophageal obturator airway artificial airway inserted in the esophagus. The device occludes the esophagus so that delivered ventilation enters the lung.
Esophageal pressure pressure measured in the midesophagus and taken to represent pleural pressure.
Expiratory flow time the time during which expiratory flow occurs.
Expiratory phase (expiration) the part of the ventilatory cycle from the beginning of expiratory flow to the beginning of inspiratory flow.
Expiratory pause time the time during the expiratory phase when no flow is occurring.
Expiratory time the duration of the expiratory phase.
Expired air resuscitation rescue breathing during cardiopulmonary resucitaiton in which the rescuer's exhaled gas provides ventilation for the victim. Types of expired air resuscitation include mouth-mouth and mouth-to-mask ventiation.
External compressor a device external to the ventilator used to supply pneumatic source power.
Extracorporeal membrane oxygenation (ECMO) a technique whereby blood is taken from a vein, passed through a device that adds oxygen, and then returned to the patient either into one of the great veins or the arterial circuit.
Flow rate of gas delivery in and out of the lung.
Flow synchrony matching of ventilator flow deliver to patient efforts during interactive breaths.
Food and Drug Administration US government agency charged with ensuring safety and efficacy of medical devices.
Gas consumption gas consumed by a ventilator that does not participate in ventilation on the patient. The gas is used to control ventilator function and is wasted.
Gastric insufflation forcing air into the stomach during positive pressure ventilation in an uninstrumented airway.
Gauge pressure pressure measured relative to atmospheric pressure.
Gravitational sedimentation deposition of aerosol due to weight of the particle in a stagnant air stream.
Graham's law the rapidity of diffusion of two gases varies inversely with the square root of their densities.
Heat and moisture exchanger a passive humidifier that uses only physical means of heat and moisture exchange.
Heat and moisture exchanging filter a passive humidifier that uses physical means of heat and moisture exchange and includes a breathing circuit filter.
Heated wire circuit a ventilator circuit that contains electric wires that heat the gas as it travels down the circuit. These devices help eliminate or minimize condensate.
Helium (He) a gas that is much less dense than air and/or oxygen and thus requires less pressure to effect flow through given resistance.
High flow humidifier a humidification device used to add moisture to inspired gases and flows used during mechanical ventilation.
High frequency ventilation (HFV) ventilatory support characterized by frequencies greater than physiologic breaths per minute.
HME booster a device that adds moisture to inspired gas between the passive humidifier and the patient.
Hygroscopic heat and moisture exchanger a passive humidifier in which both physical and chemical means of heat and moisture exchange are used.
Hygroscopic heat and moisture exchanger filter a passive humidifier in which both physical and chemical means of heat and moisture exchange are used; it incorporates a breathing circuit filter.
Hyperbaric oxygen therapy (HBO) the administration of oxygen at high levels of pressure (greater than atmospheric; 760 mmHg). During hyperbaric exposure, plasmadissolved oxygen increases approximately 2vol % for every atmospher increase in inspired oxygen. Typical applications of HBO
Independent lung ventilation (ILV) a method by which the gas flow to each lung is effectively separated mechanically by either two small endotracheal tubes (ETT) or one specifically designed double-lumen ETT for the purpose of differential ventilation of each lung, with different ventilat
Indirect calorimetry a technique that measures oxygen consumption and CO2 production to predict nutritional needs and quantify metabolic activity.
Inertial impaction the process of removing large aerosol particles from a carrier gas due to greater inertia. Larger particles travel in a straight trajectory and impact against objects in their path.
Inspiratory/expiratory timing the ratio of inspiratory time to expiratory time (I:E ratio).
Inspiratory phase (inspiration) the part of the ventilatory cycle from the beginning of inspiratory flow to the beginning of expiratory flow. Any inspiratory pause is included in the inspiratory phase.
Inspiratory flow time the time during the inspiratory phase when flow is being delivered.
Inspiratory pause time inspiratory pause is a brief pause (0.5 to 2 sec) at end-inspiration during which pressure is held constant and flow is zero. Under those conditions, airway pressure is equal to end inspiratory alveolar pressure. The pause may also improve gas mixing.
Inspiratory time inspiratory time (expressed in sec) is the duration of inspiration during mechanical ventilation. As inspiratory time increases, mean airway pressure increases and the I:E ratio becomes higher.
Inspired gas concentrations the partial pressures of oxygen, nitrogen, and other therapeutic gases such as helium or nitric oxide that may be in the inspired gas mixture.
Internal compressor a device inside the ventilator used to convert either pneumatic or electric source power into inspiratory pressure.
Intravascular oxygenation a technique whereby blood oxygenation devices are inserted into the vasculature.
Intrinsic PEEP end-expiratory pressure in the lung as a consequence of excessive minute ventilation, an inadequately set expiratory time or airway obstruction preventing lung emptying. Intrinsic PEEP is sometimes referred to as air trapping, auto-PEEP, and occult PEEP.
Jets ventialtory devices used in a technique to deliver HFV.
Laminar flow flow through a tube that flows parallel to the tube walls in concentric layers with linear velocities that increase toward the center of the tube.
Laryngeal mask airway a device used to direct gas delivery into the larynx without an endotraceal tube.
Laryngoscope device designed to permit visualization of the larynx and airways through the mouth.
Lithium chloride a hygroscopic chemical substance that enhances the heat-and moisture-exchanging capabilities of the passive humidifier.
Limit to set a maximum value for pressure, volume, or flow during mechanically supported inspiration (or expiration); the preset maximum value for pressure, volume, or flow during an assisted inspiration (or expiration). Insiration (or expiration) does not term
Lung protective strategies mechanical ventilation strategies designed to limit/reduce overdistension and under-recruitment of the lung so as to minimize iatrogenic lung injury.
Mandatory breath a mechanical breath that is initiated and terminated b the ventilator rather than by the patient's ventilatory drive.
Mass median aerodynamic diameter (MMAD) the particle diameter around which the mass of particle diameters is equally distributed.
Mean airway pressure the average pressure that exists at the airway opening over the ventilatory period. It is usually measured as gauge pressure. Mean airway pressure is mathematically equivalent to the area under the time-pressure curve (from the beginning of one breath tot
Mechanical ventilation the technique of providing by means of a machine either some or all of hte work of breathing for a patient.
Mechanical ventilation outcome descriptions of the important results from using mechanical ventilation. Generally recognized important outcomes are mortality, length of stay on the ventilator, and iatrogenic complications.
Metered dose inhaler a device in which a pressurized canister is used to deliver a precise dose of aerosolized medication.
Minimal occlusive technique the technique for maintaining the endotracheal tube cuff in which a volume of gas is used in the cuff sufficient to allow a small air leak at end-inspiration.
Minimal seal technique the technique for maintaining the endotracheal tube cuff in which uses a volume of gas is used in the cuff sufficient to prevent a leak at end-inspiration.
Minute ventilation(MV) the total amount of gas moving inor out of the lungs during 1 minute.
Monitor a routine repetitive or continuous measurement of a parameter.
Moisture output the amount of moisture delivered to the patient from a passive humidifier expressed in mg H2O/L.
Mucociliary excalator the cilia and mucus layer that propel mucus and foreign bodies up the respiratorytree to be swallowed or expectorated.
Muscle fatigue a condition of muscle dysfunction that is recoverable by rest.
Muscle overload a condition in which the load on the muscles is excessive and may cause fatigue.
Myopathy any disease of muscle.
Non-convective gas transport movement of O2 and CO2 by mechanisms other than bulk flow movement of discrete tidal volumes.
Obstructive lung disease disease characterized by airway narrowing.
Open-loop control a control scheme in which the output of a system is determined by the initial setting of the controller with no corrections made to accommodate disturbances in the output caused by external factors.
Oro-and nasoppharyngeal airways devices inserted into the mouth or the nose to help maintain aiway patency.
Oscillators a technique to deliver HFV utilizing oscillating piston or membrane.
Overdistinsion the process of providing excessive volume to lung regions, thereby causing a "stretch" injury.
Oxidant injury an injury that can occur to living tissue when excessive oxygen concentrations are used. The mediators of oxygen injury are a variety of free radicals generated in the presence of high oxygen concentrations.
Oxygen (O) a chemical element. It constitutes about 20% of atmospheric air and is the essential agent in the respiration of plants and animals. Although noninflammable, it is necessary to support combustion.
Oxygen delivery system a device used to deliver oxygen concentrations above ambient air to the lungs through the upper airway.
Oxygen powered breathing device a device that consists of a demand valve that can be manually or patient triggered. The OPD is connected to a 50-psig source of gas and connects to the patient via a standard 15/22 mm connector. During manual activation of the demand valve, the operator d
Oxygen toxicity the pathologic response of the body and its tissues resulting from long-term exposure to high partial pressure of oxygen; pulmonary manifestations include cellular changes causing congestion, inflammation, and edema.
Paralysis loss or impairment of motor function in part due to a lesion of the neural or muscular mechanism; also, by analogy, impairment of sensory function.
Parenchymal lung injury lung injury resulting from processes affecting the alveolar capillary interface, the interstitium, or the vasculature.
Partial liquid ventilation the achievement of gas exchange through the use of oxygen soluble (often perfluorocarbon) liquid in the functional residual capacity of the lung.
Partial ventilatory support mechanical ventilatory support in which the patient and the ventilator share the ventilatory load.
Passive expiration expiration not assisted by the ventilatory muscles.
Passover humidifier a humidifier that imparts heat and moisture to gas flowing over the surface of the water. Also, a humidifier that collects the patient's expired heat and moisture and returns it on inspiration.
PEEP acronym for positive end-expiratory pressure.
Perfluorocarbons perfluorocarbons are colorless, odorless, and inert liquids produced by the fluorination of common organic hydrocarbons. These liquids have gained papularity as an alternative respiratory medium because of their high solubilities for the respiratory gases
Permissive hypercapnia ventilatory support strategy that accepts hypercapnia as a trade-off to excessive lung distension.
Peroxynitritic a substance produced by nitric oxide that is potentially toxic.
Phase one of four significant events that occure during a ventilatory cycle: (1) the change from expiratory time to inspiratory time, (2) inspiratory time, (3) the change from inspiratory time to expiratory time, and (4) expiratory time.
Phase variable a variable (such as pressure, volume, flwo, or time) that is measured and used to initiate some phase of the ventilatory cycle.
Phase variable value the magnitude of a phase variable.
Pleural pressure pressure inside the pleural space (between the lungs and chest wall) often reflected as esophageal pressure.
Pneumonia infection in lung parenchyma.
Positive pressure ventilation use of positive airway pressure to support ventilation.
Postextubation stridor the sound that occurs in an extubated paient from flow through an upper airway narrowed by inflammation from an endotracheal tube.
Pressure gradients the difference in pressure across a resistance or a compliance structure.
Pressure-time product a quantification of ventilation load that is obtained by integrating pressure over time.
Pressure-volume plots graphical display of applied pressure over volume. The area of the plot is work.
Proportional assist ventilation (PAV) an interactive ventilatory support mode that provides patient-triggered breaths in which flow and volume delivery are controlled by clinician-set "gains" placed on sensed patient effort. With PAV, increases in patient effort result in increased flow, volu
Protected specimen brush this is a small brush at the end of a long catheter designed to sample distal airways for microorganisms. It has an outer sheath to "protect" it from contamination from upper airway microorganisms.
Pulmonary artery hypertension high pressures within the pulmonary vasculature. This is usually caused by an increase in pulmonary vascular resistance secondary to lung disease, and/or hypoxia.
Relative humidity the amount of water vapor in a gas compared with the maximum amount of water that gas can carry. Relative humidity is expressed as a percent.
Resistance impedance to flow in a tube or conduit; quantified as ratio of the difference in pressure between the two points along a tube lenght divided by the volumetric flow of the fluid per unit time.
Respiratory distress syndrome(RDS) a result of surfactant deficiency and//or a pulmonary insult in the neonatal period, this condition is marked by tachypnea, hypoxemia, decreased pulmonary compliance, and alveolar collapse.
Respiatory insufficiency the inability of the body to provide adequate arterial oxygenation.
Respiratory quotient ratio of CO2 production to O2 consumption.
Responsiveness a description of demand valve performance that refers to how fast the valve can respond to a patient demand.
Resting energy expenditure the caloric consumption of a patient.
Reynolds number a dimensionless number that predicts whether flow will be laminar or trubulent based on gas velocity, viscosity, density, and tube diameter. A Reynolds number <2000 indicates laminar flow and >2000 indicates turbulent flow.
Right ventricular dysfunction dysfunction of the right ventricle induced by high pulmonary vascular resistance (right ventricularor intrinsic heart disease).
Saturated the state of gas that is carrying the maximum possible amount of water vapor. Saturated gas is at 100% relative humidity.
Sedation the allaying of irritability or excitement, especially by administration of a sedative.
Sedation level score score used to determine the adequacy of sedation based on patient response to stimuli.
Sellick maneuver technique of providing cricoid pressure named for its inventor.
Sensitivity a measure of the amount of effort that must be generated by a patient to trigger a mechanical ventilator into the inspiratory phase; alternatively, the mechanism used to set or control this level.
Shunting pulmonary capillary blood completely bypassing ventilated alveoli.
Small-volume nebulizer an aerosol generator that requires a gas source to nebulize liquid medications.
Spacer a device used to improve aerosol delivery by stabilizing particle size and reducing the need for breath/actuation coordination. Can be used in ambulatory and mechanically ventilated patients.
Spontaneous breath breath that is both patient initiated and patient terminated.
Spontaneous ventilatory drive inherent ventilatory drive set by the patient's ventilatory control center in the brain.
Suction catheter thin, hollow plastic tube containing several distal holes used for removal of airway secretions by application of negative pressure.
Surfactant lung lining fluid that reduces surface tensions.
Sympathomimetics adrenergic; producing effects resembling those of impulses transmitted by the adrenergeic postganglionic fibers of the sympathic nervous system.
Total liquid ventilation the achievement of gas exchange through the delivery of tidal volumes of perfluorocarbon liquid to the lungs, using a specialized mechanical liquid ventilator.
Total ventilatory support mechanical ventilatory support supplying total unloading of a patient's ventilatory muscles.
Tracheal gas insufflation (TGI) a technique whereby a low flow of fresh gas is delivered to the distal end of the endotracheal tube through a small diameter catheter. This flow can be either continuous (i.e., throughout the ventialtory cycle) or delivered only during exhalation. The pri
Tracheal intubation the technique by which a tube is inserted into the trachea in order to supply a patent airway.
Train-of-four a method of monitoring neuromuscular blockade in patients. A sequence of four electrical stimuli are delivered to electrodes placed over a nerve (usually the temporal or radial nerve) and the twitch of the involved muscle group is measured to gauge neurom
Transducer a device capable of converting one form of energy into another and commonly used for measurement of physical events; for example, a pressure transducer may convert the physical phenomenon of force per unit area into an analog electrical signal.
Tansrespiratory pressure the pressure difference between airway and body surface.
Trigger to initiate the inspiratory phase of an assisted breath.
Turbulent flow flow characherized by formation of currents and eddies resulting in chaotic movement of gas molecules and a Reynolds number >2000.
Under-recruitment the phenomenon of alveolar collapse that persists because of inadequate expiratory pressure. Linked to lung injury.
Venoarterial bypass technique for cardiopulmonary bypass (see extracorporeal oxygenation).
Venovenous bypass technique for cardiopulmonary bypass (see extracorporeal oxygenation).
Ventilator circuit the plastic nondisposable or disposable tubing (22 mm OD for adults) that connects the mechanical ventilator to the artificial airway or mask.
Ventilation distribution the description of how the tidal volume is distributed to the millions of alveolar units.
Ventilation/perfusion (V/Q) relationships quantification of the relationship of ventilation to perfusion in alveolar capillary units. This is normally 1. Very high V/Q units are effectively dead space. V/Q units of 0 are shunts.
Ventilator dependence need for mechanical ventilation.
Ventilator discontinuation discontinuation of mechanical ventilation support from a patient.
Volume space occupied by matter measured in milliliters or liters.
Volume-assured pressure support a mode of ventilator operation that allows automated adjustment of inspiratory pressure (pressure support) based upon tidal volume.
Weaning gradual reduction in partial ventilatory support.
Weaning techniques ventilator strategies that accomplish weaning.
Work a quantification of ventilation load that is obtained by integrating pressure over volume. (See Pressure time product above for an alternative load expression).
Created by: jcantamessa