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Mechanical ventilator is apositive- or negative-pressurebreathing device that canmaintain ventilation andoxygen delivery for a prolongedperiod.

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PaO2 50 mm Hg with FiO2 0.60 PaO2 50 mm Hg with pH 7.25

Vital capacity 2 times tidal volume

Negative inspiratory force 25 cm H2O Respiratory rate 35/min

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Negative-Pressure Ventilators Iron Lung (Drinker Respirator Tank)

Body Wrap (Pneumo-Wrap)

Chest Cuirass (Tortoise Shell)

Positive-Pressure Ventilators Pressure-Cycled Ventilators Time-Cycled Ventilators Volume-Cycled Ventilators Noninvasive Positive-Pressure Ventilation

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Negative-pressure ventilators exert anegative pressure on the externalchest. Decreasing the intrathoracic pressureduring inspiration allows air to flowinto the lung, filling its volume.

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It was used extensively during polioepidemics in the past and currently isused by a few polio survivors andpatients with other neuromusculardisorders

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Portable devices that require a rigid cage orshell to create a negative-pressure chamberaround the thorax and abdomen. Because of problems with proper fit andsystem leaks, these types of ventilators areused only with carefully selected patients.

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inflate the lungs by exerting positivepressure on the airway, pushing air in,similar to a bellows mechanism,forcing the alveoli to expand duringinspiration.

These ventilators are widely used inthe hospital setting and areincreasingly used in the home forpatients with primary lung disease.

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delivers a flow of air (inspiration) until itreaches a preset pressure, and then cyclesoff, and expiration occurs passively.

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terminate or control inspiration after apreset time. The volume of air thepatient receives is regulated by thelength of inspiration and the flow rateof the air.

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Most commonly used The volume of air delivered with eachinspiration is preset. Once this presetvolume is delivered to the patient, theventilator cycles off and exhalationoccurs passively.

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A method of positive-pressureventilation that can be given via facemasks that cover the nose and mouth,nasal masks, or other oral or nasaldevices

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refers to how breaths aredelivered to the patient.

The most commonly used modesare: Assistcontrol Intermittent Mandatory Ventilation Synchronized Intermittent MandatoryVentilation

Pressure Support Ventilation Airway Pressure Release Ventilation

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provides full ventilatory supportby delivering a preset tidal volumeand respiratory rate.

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provides a combination ofmechanically assisted breaths andspontaneous breaths.

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delivers a preset tidal volume andnumber of breaths per minute. Between ventilator-delivered breaths,the patient can breathe spontaneouslywith no assistance from the ventilatoron those extra breaths.

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applies a pressure plateau to theairway throughout the patient-triggered inspiration to decreaseresistance within the tracheal tube andventilator tubing.

Pressure support is reduced graduallyas the patients strength increases.

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a time triggered, pressure-limited, time-cycled mode of mechanical ventilation thatallows unrestricted, spontaneous breathingthroughout the ventilatory cycle.

The inflation period is long, and breaths maybe initiated spontaneously as well as by the

ventilator.

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Type of ventilator (eg, volume-cycled,pressurecycled, negative-pressure) Controlling mode (eg, controlledventilation, assistcontrol ventilation,

synchronized intermittent mandatoryventilation) Tidal volume and rate settings (tidal volume

is usually set at 6 to 12 mL/kg [ideal bodyweight]; rate is usually set at 12 to 16breaths/min)

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FiO2 setting Inspiratory pressure reachedand pressure limit (normal is 15 to 20 cmH2O; this increases if there is increasedairway resistance or decreased compliance) Sensitivity (a 2-cm H2O inspiratory forceshould trigger the ventilator) Inspiratory-to-expiratory ratio (usually 1:3

[1 second of inspiration to 3 seconds ofexpiration] or 1:2)

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Minute volume (tidal volumerespiratory rate, usually 6 to 8 L/min)

Sigh settings (usually set at 1.5 timesthe tidal volume and ranging from 1to 3 per hour), if applicable

Water in the tubing, disconnection orkinking of the tubing

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Humidification (humidifier filledwith water) and temperature

Alarms (turned on and functioningproperly)

PEEP and pressure support level, ifapplicable (PEEP is usually set at 5to 15 cm H2O)

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If the ventilator system malfunctions andthe problem cannot be identified andcorrected immediately, the nurse mustventilate the patient with a manualresuscitation bag until the problem isresolved.

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Coughing or plugged airway tube Suction airway for secretions, emptycondensation fluid from circuit

Patient bucking ventilator Adjust sensitivity

Decreasing lung compliance Manually ventilate patient

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Increase in compliance None

Leak in ventilator or tubing; cuff on tube/humidifier not tight Check entire ventilator circuit for patency

Correct leak