18. High Frequency Jet Ventilation (HFJV)

Question 1

Life port ETT adapter:

What is measured at the pressure monitoring port? What function does the jet port serve?

Answer 1

PIP

used to inject inspired gas down the ETT in high velocity spurts

Question 2

How is diffusion facilitated during inspiration?

Answer 2

train of tiny tidal volumes move high pO2 gas close to alveoli

Question 3

How is evacuation of secretions facilitated on expiration?

Answer 3

expired gas swirls out around the inspired gas along the airway walls

Question 4

List some considerations for HFV.

Answer 4

conventional ventilation upper limits reached (PIP > 20-30cmH2O, VT > 6mL/kg, rates > 55), air leak syndromes, pulmonary hypoplasia, non-homogenous lung disease (excessive secretions, MAS), abdominal distention/surgery, extreme prematurity, difficult to wean BDP, hemodynamic compromise

Question 5

Jet PIP:

What is the primary control of ventilation? What produces the tidal volume?

Answer 5

delta P/tidal volume

delta P

Question 6

What is jet rate usually started at? What should the rate be reduced to during air leak or evidence of air trapping?

Answer 6

420

240

Question 7

What is inspiratory time set to? At a rate of 240, the I;E ratio is what and is advantageous for what?

Answer 7

0. 02 sec

1: 12, advantageous for allowing healing of air leak

Question 8

What is the role of the conventional ventilator?

Answer 8

provide fresh gas flow, provide PEEP, provide recruitment breaths

Question 9

How is oxygenation controlled? What is the safest way to increase PEEP? At which FiO2 should MAP be weaned? When else should MAP be weaned?

Answer 9

MAP and FiO2
PEEP
< 30
any signs of over-distension or improving x-ray

Question 10

What will you see with PEEP that is too low vs. too high?

Answer 10

too low: a/w collapse/atelectasis
too high: alveolar over distension, impedance of pulmonary perfusion, CV depression, poor right heart filling, impedance of venous return

Question 11

HFJV PIP:

Where to start? When to raise? When to lower?

Answer 11

20-25cmH2O
when trying to decrease CO2, raise PIP as high as necessary
when trying to increase CO2, may need to raise PEEP to keep MAP constant

Question 12

HFJV Rate:

Where to start? When to raise? When to lower?

Answer 12

420 bpm
to lower CO2
to increase CO2, lengthen exhalation time and reduce auto-PEEP or when weaning

Question 13

HFJV Ti:

Where to start?

Answer 13

0.02 seconds and leave it

Question 14

Why is HFJV successful in treating BPF?

Answer 14

high velocity gas shoots right past upper a/w leaks

Question 15

What if you can’t oxygenate when you are attempting to facilitate healing by lowering all airway pressure?

Answer 15

increase PEEP

Question 16

When does gas trapping occur? How is it confirmed? How can you lengthen exhalation time?

Answer 16

when tidal volumes have insufficient time to exit the lungs
CXR (hyperinflation), monitored PEEP exceeds CMV set PEEP
decrease jet rate

Question 17

What does servo pressure = and when does it change? What can changes in servo pressure serve as?

Answer 17

automatically controlled driving pressure, changes as lung volume changes
give early warning of patients’ changing clinical conditions

Question 18

What can the low alarm for Servo pressure go off?

Answer 18

degradation of lung mechanics, atelectasis, accumulation of secretions, tension pneumothorax, right mainstem intubation

Question 19

When would the high alarm for Servo pressure go off?

Answer 19

improved lung mechanics (compliance or resistance), tubing leaks

Question 20

If Servo pressure slowly falls over time, suction when:

What should you consider lung recruitment?

Answer 20

PaCO2 rises, SaO2 falls, chest wall movement diminishes

post suctioning or disconnects

Question 21

What are the 2 options for weaning from the jet?

Answer 21

extubate to CPAP/NIV or switch to conventional (low rate, low pressures and then wean to extubate)