Mechanical Ventilation

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Ventilator Cycle: (4 events)

trigger that initiates inspiration

the limit is variable and maintains inspiration

cycle mechanism causes the breath to end

baseline is the passive exhalation

Handoff Info includes

Mode of ventilation, rate and freq

tidal volume (Vt)

FiO2

Additional applicable settings like PEEP or Pressure support (PS)

Volume Ventilation

CMV: set Vt and rate regardless of pt inspiratory effort

If set to deliver 500 mL 10 x per min, and pt attempts to breath- ventilator dyssynchrony occurs causing high intrathoracic pressures and barotrauma

AC: senses pt's inspiratory effort and completes it based on Vt that has been set

Vent is set to deliver 500 mL 10 x per min. If pt breathes 14 x per min, every breath- whether vent or pt triggered - delivers 500 mL. Hyperventilation occurs if spontaneous breaths exceed set rate- look at different mode or sedation.

IMV or SIMV: delivers set number of breaths at a set Vt and synchronizes with pt's inspiratory effort. Spontaneous pt breaths betwn vent breaths are not assisted with set Vt.

Vent is set to deliver 400 mL 10x per min. Pt breaths 14 x per min. Only 10 of those breaths will be delivered 400 mL.

Pressure Ventilation

PCV: delivers preset number of breaths, augmented by preset inspiratory pressure. This mode is time cycled to end inspiration and begin expiration

used to provide suport in pts with noncomplaint lungs and poor oxygenation like ARDS, with rising PIP and plateau pressures. Can be used in conjunction iwth a reversed inspiratory to expiratory (I:E) ratio and is called PC/IRV (pressure controlled/Inverse ratio vent)

PSV: delivers set amount of inpiratory pressure when pt initiates spontaneous breath. May be used alone or added to SIMV to support spontaneous, non Vt supported breaths

indicated for pts who are ready to wean from vent, as an adjunct to SIMV, or for those that experience discomfort related to inc airway resistence from ETT

PEEP/CPAP: Maintains preset pressure at the end of expiration. Functional residual capacity oxygenation is improved because the small airways and avleoli are maintained supported during expiration. Referred to as PEEP when used in conjunction with other vent modes. CPAP when it is stand alone.

indications: (1) prevent or reverse atelactasis, (2) improve oxygenation, (3) improve lung volume, (4) provides internal stabilization such as for flail chest

Commonly set at 5-15 cm H2O (greater than 10 may result in barotrauma)