Invasive Ventilation

Question 1

why dual heated limb?

Answer 1

prevents rain out, circuit highly sensitive/reactive to resistance changes

Question 2

adult/infant/neo circuit diameter

Answer 2

adult: 22mm ID
infant: 15mm ID
neonatal: 10mm ID

Question 3

5 factors to consider when assessing impact of equipment on Vt

Answer 3

1. compressible volume loss reduced by stiff circuit, filled humidifier pod, vent setting precision
2. managing ETT leak as cuff less, size, vent setting precision
3. minimizing mechanical deadspace (rebreathing) with small wye, flow sensor/EtCO2 housing
4. resistance
5. optimal humidification/heated circuit

Question 4

factors impacting leak size

Answer 4

• uncuffed ETT diameter
• applied airway pressure
• duration of inspiration (longer = more leaked)

Question 5

improving Vt with decreased lung compliance

Answer 5

optimize PEEP to keep alveoli open

Question 6

how does vent manage leak or breath delivery?

Answer 6

• leak compensation
• breath type/mode
• settings (flow, pressure, I-time, volume)

Question 7

indications for mechanical ventilation

Answer 7

1. impaired drive to breathe
2. manipulate alveolar ventilation
3. improve oxygenation
4. optimize lung volumes
5. reduce WOB
6. minimize VILI

Question 8

neonatal ventilation

Answer 8

who: up to 1 year

mode: pressure controlled or limited (dual)

trigger: time, patient (IMV vs SIMV)

cycle: time, flow

Vt: 4-6 mls/kg

Question 9

pediatric ventilation

Answer 9

who: children >1 year, usually >10kg

mode: volume or pressure controlled, dual control

cycle: volume or time

Vt: 4-6 mls/kg if lung disease; 6-8 mls/kg for teens

Question 10

pressure control risks

Answer 10

• pneumothorax
• inadvertent hyperventilation (as low as <25 mmHg)
• large swings in PaCO2 (IVH)