Ventilators

All you need to know is…

Types

• Two types in general, volume control and pressure control.

• Pressure control primarily used in children

• Volume control is much more common for transport.

Use of Ventilator

• Supports two primary functions: Oxygenation- delivering oxygen to the

lungs Ventilation- exchanging gases: oxygen

in, carbon dioxide out.

Oxygenation

• Providing the patient with adequate oxygen

• If there is an injury to the lungs we may need to increase the amount of oxygen delivered.

Oxygenation

• To increase oxygenation, we can increase the fraction of inspired oxygen (FiO2) which will put more oxygen into the alveoli.

• Increase the Positive End Expiratory Pressure (PEEP) which will open up more alveoli (recruitment) allowing for better gas exchange.

Ventilation

• Ventilation requires an exchange of gas at a particular minute ventilation (the volume of air exchanged in 1 minute or rate x tidal volume).

• Ventilation can be adjusted by changing the rate of breathing or the amount of each breath (tidal volume)

Monitoring: How do I know this is right?

• Pulse Oxymetry (SpO2): Measures the amount of oxygen bound to hemoglobin (given in a percentage). May be falsely elevated in poisonings

(CO, CN) If less than 92% increase Oxygen or

amount of lung used to breath (PEEP) Does not measure ventilation, CO2 can

build up to dangerous levels even when O2 is 100%

Monitoring: How do I know this is right?

• End Tidal Carbon Dioxide (ETCO2): Measures how much CO2 is coming out of the lungs A measure of ventilation, tells you how much of

the bad is getting out and whether or not your tune is good

Also important measure of resuscitation.

Can effect the amount of blood flowing to the brain. DO NOT ALLOW ETCO2 TO FALL BELOW 30 IN A HEAD INJURED PATIENT UNLESS INSTRUCTED TO DO SO.

What do all these knobs do?

• Mode: Assist Control (AC): delivers as many full

volume breaths as are selected, patient will get full volume breath with every initiated breath; best for the unconscious / unresponsive patient

Intermittent Mandatory Ventilation (IMV) or Simultaneous IMV (SIMV): delivers breaths synchronized with the patients spontaneous rate of breathing. Requires pressure support to compensate for tube resistance

What is Non Invasive Ventilation?

• CPAP- continuous positive airway pressure.

• BiPAP IPAP (Inspiratory Positive Airway Pressure)-

Provides pressure support at the initiation of a breath to decrease the work of breathing. (10cm H2O)

EPAP (Expiatory Positive Airway Pressure)- Essentially PEEP to improve gas exchange (5cm H2O)

NIPPV

• Advantages: Decreases work of breathing Rests respiratory musculature Improves gas exchange

• Disadvantages Requires a conscious, cooperative

patient No Apnea alarm or override

Rate

• The normal adult respiratory rate is 12-16 per minute.

• An unconscious patient requires even less and may only need to be ventilated 12 per minute.

• Patients with an acidosis (high acid levels in the blood) may require more frequent breaths.

Tidal Volume

• Tidal Volume (Vt) is the amount of air delivered with each breath.

• On average a person requires 6-8ml of air per kg. So a 70kg male should have a Vt of 420-560ml.

• Using volumes that are too high leads to overventilation, too low and the patient is underventilated

PEEP

• Positive End Expiratory Pressure (PEEP): The pressure left in the lungs at the end of the breathing cycle. Normal or Physiologic PEEP is 5-7 cm of H2O. PEEP prevents lung sacs (alveoli) from

collapsing shut. This allows more lung are for breathing (increasing the PEEP will increase the SpO2).

High levels of PEEP and Tidal Volume will increase pressure in the chest and decrease blood flow to the heart and blood pressure.

Pressure Support

• Decreases the resistance of the breathing tube.

• Usually set at 10• Does not apply to Assist Control

mode

Oxygen Concentration

• FiO2: The percentage of oxygen delivered. Should be as little as is necessary.

• Often patients will only require 50% FiO2

• Patients with unknown injuries or illness should be oxygenated at 100%

I:E Ratio: Inspiratory-to-expiratory duration

• Normal is 1:2• Can be adjusted by changing the flow rate

↑ inspiratory flow rate ↓ time for lung inflation ↑ I:E ratio (i.e. 1:2 1:4)

• If I:E falls below 1:2, lungs may not empty completely Hyperinflation Increasing peak pressures (Volutrauma)

• If > 2:1 cardiac output may be diminished by increased intra-thoracic pressure.

Vent Orders

• AC/12/700/5/70%• What does this mean? (Assist control

at a rate of 12, VT 700, PEEP of 5, and 70% oxygen)

• How much does this patient weigh? (70-100kg)

• Is this the right setting for a patient who is awake and taking some spontaneous breaths? (SIMV is better)

Trouble Shooting

• High CO2

• May need to increase respiratory rate or tidal volume

• Low CO2

• Leaks• Hyperventilation• Cardiac Arrest

• Low Saturation• Monitor is not correlating• Increase O2

• Increase PEEP as long as Peak Pressures are <40

Trouble Shooting

• High Pressure alarm• Look for occlusions• Check for Pneumothorax• Decrease tidal volume

• Low Pressure alarm• Check the tube (balloon)• Check the connections

Questions?

• What do you do if you can not oxygenate a patient with 100% oxygen and a high PEEP?

• What do you do if the vent fails?• What do you do if your vent alarms

despite the trouble shooting procedures?

• (THE ANSWER TO ALL #3 IS BAG!)