Ventilation Settings

Tidal Volume (Vt)

-set if volume-cycled modes

-based on IBW

-the volume of of gas inspired or expired in one breath

-6-8 mL/kg of IBW

• 400-600 mL/breath

Minute Ventilation (VE)

-the volume of air that moves in and out of the lungs in 1 min

-this = Vt x RR

-normal: 4-8 L/min

-normal 100 mL/kg/min

-is the same as cardiac output

Dead Space

-product of the loss of gas within the upper airways, chest, bronchioles, and lung units

-calculate = 1mL/1 pd of IBW

on average? 150 mL

Mechanical Dead Space

-loss of volume in the ventilator circuit, ETT, viral filters, ETCO2, or suctions devices

Respiratory Rate

-amount of breaths per minute

-8-12 breaths per min average

-high rates = less time for exhalation; increased mean airway pressure; and can cause airway trapping

-initial rate can be as low as 5-6 b/min in asthmatics

Fraction of Inspired Oxygen (FiO2)

-percentage of oxygen being inhaled by the patient

-tailored to the patient

-lowest that produces an arterial oxygen sat greater than 93% and a PaO2 > 60

Inspiration/Expiration ratio (I:E)

-ratio comparing the time given to inhale vs the time given to exhale

-normal is 1:2

-reduced to 1:4 or greater in the presences of an obstructive disease (such as COPD, asthma, etc) to avoid air-trapping and auto-PEEP

-use of inverse ratio may be necessary with those who have ARDS

I-time

-over over which the tidal volume is delivered (volume delivery) or the pressure is maintained (pressure delivery) depending on the mode of delivery

Trigger (Sensitivity) (“flow trigger”)

-a set number (either volume or pressure) at which the ventilator is triggered to deliver a breath

-the lower the number the easier the trigger

-generally recommend a trigger of 3L/min bias flow or as high as 5L/min bias flow

Peak End Expiratory Pressure (PEEP)

-tool used to maintain alveolar recruitment

-keeps alveoli open at the end of expiration

-used in association with FiO2 to maintain adequate oxygenation

-starting point: 5 cmH2O

-can go as high as 20 cmH2O

Pressure Support (PS)

-pressure-targeted mode of ventilation support

-each inspiration is augmented by an elevation in airway pressure at the onset of inspiratory effort

-decreases WOB

-start at 10 cmH2O

-only increase or decrease by 1 at a time

-this is PS + PEEP