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PVRS > HFO > Flashcards

HFO Flashcards

1
Q

what are the 4 gas exchanges theories?

A
  1. bulk convection
  2. pendelluft
  3. streaming or asymmetrical velocity
    - ->velocity of gas is higher at centre of airway. Gas along side of airways is pushed backward (exhalation)
  4. taylor type dispersion
    - ->enhanced diffusion due to turbulence of gas flow reaching small airways
  5. moelcuelar diffusion
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2
Q

What is bulk convection?

A
  • Direct alveolarventilation
  • Primary mode of gas exchange in conventional ventilation
  • Some component of this in high frequency
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3
Q

What is pendelluft?

A
  • Exchange of gas between lung units with different time constants
  • when the unit with shorter TC exhales, the gas will go into the lung unit with normal TC due to path of least resistance
  • the gas can also go into collapsed lung unit, helping with atelectasis
  • this is used as a rescue method for babies
  • also used for ARDS
  • With time, lung units with longer time constants may get recruited
  • good for lung unit with different time constants
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4
Q

What is asymmetrical velocity profiles?

A
  • aka “Spike” and “Helical” diffusion
  • Velocity of fresh gas is higher in centre
  • Expiratory gases move in opposite direction at sides at slower velocity
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5
Q

What is taylor type dispersion?

A

Principle method of gas transport in HFO

  • Turbulence in small airways enhances molecular diffusion
  • Increase time for gas exchange (molecular diffusion)
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6
Q

What is Po2 influenced by in HFO?

A

Fio2 and MAP (or the peep)

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7
Q

What is PaCo2 influecned by in HFO?

A

driving pressure and RR

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8
Q

What is the relationship between RR and Co2 in HFO?

A

decrease RR, decrease Co2

**increasing the frequency of todal breaths will not provide enough time for complete inhalation and exhlation–> decrease the MV –> decreasing Co2 exhale

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9
Q

what is HFPPV?

A
  • Conventional ventilator
  • Used before high frequency devices available
  • Low Compliance circuit
  • Vt smaller than with CMV but Vt > Vd
  • Frequency up to 150 bpm, very short I times
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10
Q

What is the inspiration for HFPPV?

A

active

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11
Q

What is the expiration for HFPPV?

A

passive

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12
Q

What is the issue with HFPPV?

A

gas trapping

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13
Q

When is HFJV used?

A
  1. Used particularly in infants with air leak syndrome and ARDS
  2. large air leaks such as bronchopleural fistula with ventilation in the ICU and in the OR with upper airway surgery

–>helps to keep pressure low at the side of the airway so that air doesnt leak out

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14
Q

How does HFJV work?

A
  • short pulsation of jet flow
  • delivered through special ETT, adaptor or catheter
  • peep, FIO2, controlled breahts, entrained gas provided by conventional ventilator
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15
Q

What does the Jet controls?

A

PIP, rate, I time

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16
Q

What is the I time of HFJV?

A

0.02 sec

17
Q

What determines Co2 removal in HFJV?

A

PIP + RR

18
Q

What is the tidal volume depends on for HFJV?

A
  • duration of pulsation
    • amplitude or driving pressure of jet
    • jet orifice size
    • patient lung characteristics
19
Q

What is the frequencies of HFJV?

A

300 - 480 cycles /min

20
Q

What is the frequency of HFFI?

A

up to 15 hertz

21
Q

What are the 2 machines of HFOV?

A

sensormedics 3100A , 3100B

22
Q

when is sensormedics 3100A , used?

A

RDS, air leak syndrome in INFANTS

23
Q

When is 3100B used?

A

Extreme ARDS, rescue therapy for adult

24
Q

What is the frequency, inspiration, expiration and Vt of HFOV?

A

frequency: 5 - 15 hz
inspiration: active
expiration: active
Vt < Vd

25
Q

how is the gas flow generated,

A

piston generate forward and backward movement of bulk flow of gas

26
Q

How is Minute volume determine in HFOV?

A

f x Vt square

27
Q

What do we use high lung volume with HFOV?

A
  • patient with atelectasis

- helps with oxygenation

28
Q

how to obtain higher lung volumes?

A
  1. increase MAP for period of times
    - ->monitor oxygenation
    - ->increase pressure in increments of 1 - 2 cmh2o
    - ->use conventional ventilation to obtain the pressure first then use that as the MAP
  2. sustained inflation maneuvers
    - -> 5-30 seconds sustained inflation higher than alveolar opening pressures
29
Q

What is the indication of low lung volume?

A

Hyperinflation
Air Leaks

–> use lower MAP

30
Q

What is the Contraindications of HFO?

A
  • *No Absolute contraindications
  • *need to use with caution, depending on the lug disease

Obstructive:
- need adequate exhalation time to avoid hyperinflation

Non-homogeneous disease

  • carefully adjust the MAP
  • lung unit with high compliance and low surface tension may allow for overinflation of alveoli

PVRS (17 decks)

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