Ventilator

CONTENT… What is a ventilator? Types of ventilators Modes of ventilators Types of support Methods of ventilatory support Indications of ventilators

What is a ventilator??? A ventilator is a machine that supports breathing These machines mainly are used in hospitals Ventilators Get oxygen into the lungs Remove carbon dioxide from the body Help people breathe easier Breathe for people who have lost all ability to breathe on their own

Types of ventilators… Negative pressure Positive pressure

Negative Pressure Ventilators Applies negative pressure around the chest wall. This causes intra airway pressure to become negative. Thus drawing air into the lungs through the patients nose and mouth No artificial airway is necessary – patient must be able to control and protect own airway Indication Selected patient with neuromuscular problems Adjunct to weaning from PEEP(Positive end expiratory pressure) Negative pressure ventilators are simply to use and do not require intubation of the airway

Positive Pressure Ventilators Positive pressure ventilators inflate the lungs by exerting positive pressure on the airway, forcing the alveoli to expand during inspiration Expiration occurs passively, endotracheal intubation or trachestomy is necessary in most cases These ventilators are widely used in the hospital setting There are Three types of positive pressure ventilators Pressure cycled Time cycled Volume cycled

Modes of ventilators… Time cycled ventilators Volume cycled ventilators Pressure cycled ventilators High Frequency Ventilators

Time delivery of gas flow; tidal volume = flow rate x inspiration time Time cycled ventilator Time delivery of gas flow; tidal volume = flow rate x inspiration time Delivers relatively constant Tidal Volume Allows precise control of gas delivery Types: IMV-Bird, Foregger 210, Emerson 

Volume Cycled Ventilator Inspiratory gas flow terminated after preselected volume delivery Pressure in circuit determined by tidal volume and Compliance Delivered Tidal volume changes with changes in Compliance Types: Bennett, Ohio 560, Bourns Bear 1, Monaghan, Siemons Servo 

Pressure cycled ventilators  Gas flow continues until preset pressure develops Tidal volume = flow rate x time until pressure is reached Variable volume if circuit pressure varies (change in compliance) Types: bird mark, bennett PR 

High Frequency Ventilators 5 types High frequency positive pressure ventilation  Jet ventilation Flow interruption Oscillation Percussive ventilation 

Types of support… Control mode Support mode

Control mode In control mode, the ventilator delivers the preset tidal volume once it is triggered regardless of patient effort If the patient is apneic or possesses limited respiratory drive, control mode can ensure delivery of appropriate minute ventilation

Support mode In support mode, the ventilator provides inspiratory assistance through the use of an assist pressure The ventilator detects inspiration by the patient and supplies an assist pressure during inspiration It terminates the assist pressure upon detecting onset of the expiratory phase Support mode requires an adequate respiratory drive The amount of assist pressure can be dialed in

Methods of Ventilatory Support… Continuous mandatory ventilation Assist-control ventilation Intermittent mandatory ventilation Synchronous intermittent mandatory ventilation Pressure support ventilation Noninvasive ventilation Continuous positive airway pressure - CPAP

Continuous mandatory ventilation Breaths are delivered at preset intervals, regardless of patient effort This mode is used most often in the paralyzed or apneic patient Assist-control ventilation The ventilator delivers preset breaths in coordination with the respiratory effort of the patient

Intermittent mandatory ventilation With intermittent mandatory ventilation (IMV), breaths are delivered at a preset interval, and spontaneous breathing is allowed between ventilator-administered breaths Synchronous intermittent mandatory ventilation The ventilator delivers preset breaths in coordination with the respiratory effort of the patient

Pressure support ventilation For the spontaneously breathing patient, pressure support ventilation (PSV) has been advocated to limit barotrauma and to decrease the work of breathing Noninvasive ventilation The application of mechanical ventilatory support through a mask in place of endotracheal intubation is becoming increasingly accepted and used in the emergency department

Continuous positive airway pressure - CPAP Improves pao2 by stabilizing the airway and allowing alveolar recruitment. CO2 retention may result from excessive CPAP Most commonly, nasal CPAP prongs (also mask, nasopharyngeal, endotracheal) used to respiratory assistance in mild rds(respiratory distress syndrome), or weaning from mechanical ventilation Maintains upper airway patency, so useful in apnea of infancy Gastric distension may occur; place OG tube for decompression 2-6 cm H20 commonly used.

Indications of ventilators … Hypercapnic respiratory failure Hypoxemic respiratory failure Correction of life-threatening acidemia in the setting of salicylate intoxication Intentional hyperventilation in the setting of major head injury with elevated intracranial pressure Suspicion of clinical brain herniation from any cause Patient in critical condition with cyclic antidepressant toxicity

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