What happens during normal inspiration
· Respiratory muscles contract
· Creates negative pressure in lungs
· Air flows into lungs (high to low pressure)
· Pressure gradient = interpulmonary pressure
What happens during normal exhalation
- Chest wall and lungs recoil
- Positive pressure in lungs created
- Air flows out the lungs down pressure gradient
What pressure does mechanical ventilation use
Uses Positive pressure
What does the ventilator push into the lungs
A mix of air and oxygen
What does the ventilator do for expiration
gas flow is turned down but some air is still blown in which acts as PEEP
How does a ventilator change the normal physiological breathing process
It reverses it
What are the 4 ventilator modes
- Spontaneous Breathing
- Controlled Ventilation (CMV)
- Mixed ventilation (SIMV)
- Supported Spontaneous breathing (PSV)
What does the spontaneous breathing setting do?
- provides some support
- patient triggers breathing
- pt controls rate and volume
what is the patient effort for controlled ventilation mode
- no pt effort
- vent breaths fully for patient
what is set for controlled ventilation
number of breathes per minute (RR)
What can be controlled for controlled ventilation
- pressure
- volume
What conscious state should the patient be in for controllled ventilation
- heaily sedated
- unconscious
what is the risk of pressure controlled ventilation
The lung pressure can change but the volume of air being pushed in stays the same causing damage
What’s the risk of volume controlled ventilation
If lung compliance decreases, not enough volume will be delivered causing hypoventilation
What are the two breathe types for Mixed ventilation
- mandatory - triggered by vent
- spontaneous - triggered by pt
What’s supported Spontaneous breathing mode
- pt breaths themselve with help
- pt triggers vent
- RR determined by pt
What is pre-set on the vent for supported spontaneous breathing
- oxygen
- PEEP
- Pressure Support
How does a ventilator maintain PEEP
Vent blows some air during exhalation to prevent lung collapse
