Highlights of Mechanical ventilation Unit 4

1
Highlights of Mechanical ventilation Unit 4

• Modes and initiation of ventilation
• By
• Elizabeth Kelley Buzbee AAS, RRT-NPS

2
The modes of ventilation

• A spontaneous breath is one that the patient
  triggers and cycles the breath, and he controls
  the VT . This breath could be assisted by the
  application of positive pressure.
• A mandatory breath is defined as one that is
  triggered and cycled by the machine. All
  mandatory breaths are assisted breaths.

3
The modes of ventilation full support modes

• CMV continuous mandatory ventilation in which
  all breaths are mandatory.
• VC-CMV volume control also called Assist/Control
  mode
• Set VT, f to get VE guaranteed VT
• Default ventilatory mode for full support with
  adults
• PC-CMV pressure control mode. Patient can trigger
  breaths just like with A/C
• Set PIP, f and TI no guaranteed VT
• Default ventilator mode for full support for
  infants

4
Indications for PC the RCP selects pressure
ventilation when

• The adult patient who cannot be managed with VC
  In this case, we keep the PIP less than 30 cmH20.
• PC results in better distribution of ventilation
  in persons with unequal RAW, but consistent
  compliances.
• There is such an airway leak so that the VT are
  unstable most common with infants and small
  children with uncuffed ET or tracheostomy tubes

5
Compare PC to VC

• In PC, the airway pressures mPAW and PIP will
  stay the same, but the VE and VT can vary based
  on patients time constants
• In VC the VE and VT are basically stable patient
  can increase f so VE could vary the PIP and the
  mPAW can be altered by patient time constants

6
Compare control mode to Assist/control

• We control patients by giving them sedation and
  paralytic agents so that the VE we set on VC-CMV
  is exactly the same
• We can control their PaC02 thus their acid base
  balance
• In A/C, the patient can trigger breaths that will
  increase the VE, so that the VE based on set VT
  and f could be lower than the actual measured VE

7
Controlling the chronic hypercapnic patient

• If your patient has a hypoxic drive, administrate
  enough Fi02 to get his Pa02 between 80-100 mmHg.
• This will result in apnea and works as a form of
  sedation in the first 24 hours.
• Must wean the Fi02 to get Pa02 between 55-65 mmHg
  before weaning

8
Problems with A/C

• Excessively high PAW can cause problems with
  hemodynamics once patient starts to breath.
• Another problem with A/C mode is the risk of
  auto-PEEP and air trapping.

9
Inverse Ratio Ventilation with PC or with VC

• This is a form of full support that uses
  increased Ti to raise the mPAW when patients
  compliance is so bad that PIP and Pplateau are
  excessive
• In IRV, the expiratory time is so short that the
  patient never completely exhales. This works like
  PEEP to recruit alveoli

10
Raising mPAW with IRV

• mPAW PIP I PEEP E
• I E
• Because we raise the inspiratory time so much we
  can decrease the PIP
• Because we create auto-PEEP with the short TE, we
  can decrease the PEEP

11
Negative pressure ventilation

• The negative pressure ventilator is a box in
  which the patients body or chest wall is
  placed. A suction device is attached to the box.
• The NPV merely replaces the ventilatory muscles.

12
Problems with Negative pressure Ventilation
patient must be able to

• protect airway
• Handle being supine all the time
• hemodynamically stable
• be comfortable in one position all the time
• handle being disconnected from vacuum for short
  time spans

13
More problems with NPV

• Patient can get skin lesions from movement of
  body inside the device
• Patient can get cold from wind
• Best 02 device is nasal cannula because 02 can be
  sucked into the neck opening

14
NPV

• Classified as controllers, but newer models can
  be A/C if there is a flow sensor placed on the
  patients nose
• Old metal iron lungs have a constant IE of II
  newer fiberglass devices can have altered IE
  ratios

15
Setting parameters on NPV

• Change level of the vacuum to increase the VT he
  could use a Wrights spirometer attached to an
  IPPB mask to measure exhaled VT
• Change the respiratory rate.

16
CSV

• continuous spontaneous ventilation in which all
  breaths are spontaneous.
• patient who can completely control his VE
• and only needs a little help such as with
  increased baseline pressures CPAP
• or some application of assisted breaths such as
  pressure support PS
• or who might require monitoring of VE

17
Pressure support ventilation

• PSV is the most common form of pressure cycled
  CSV.
• Although this does raise the airway pressure so
  that we have a higher and lower pressure, we call
  this PS rather than PIP because of the specific
  characteristics of PS
• Flow triggered and flow cycled
• Patient controls his VT, f and inspiratory time

18
Indications for PS

• When used with SIMV to reduce the WOB by
  increasing the spontaneous VT. We generally
  select the PS that will deliver a reasonable VT
  watch the spontaneous RR
•  Can be used alone during weaning. Once a patient
  is on a PS of 5-10 cmH20, he is considered at a
  level that only compensates for RAW of the
  tubing, so is considered consistent with
  spontaneous breathing.

19
PSV flow patterns

• The flow pattern is descending till it reaches 5
  LPM or 25 of the peak flow in which the flow
  stops abruptly.
• The flow slows down as the device attempts to
  keep the PS at the preset pressure.

20
VT on PS

• There is no guaranteed VT, nor VE, but we can
  increase the VT by increasing the PS pressure
• We need to set VE high f alarms closely to
  warn us of problems
• The patient sends more air to Zone III because he
  is using his diaphragm more with PS

21
To choose the correct level of PSV there are
three methods

• get an appropriate VT 10-15 ml/kg and titrate
  the PS level to achieve this VT
•  
• increase the PS level till the respiratory rate
  is normalized 25 bpm or less
•  
• increase the PSV until you decrease the work of
  breathing through the ET tube
•  
• To select the appropriate level of PSV to
  overcome the RAW use this formula
•  
• PSV (PIP - Pplateau) x spont insp. Flow
  rate l/sec
• Ventilator flow rate l/sec

22
PSmax

• or straight pressure support or stand alone
  PS PS without SIMV. In this case, the PS is
  not used as a weaning modality but for initial of
  mechanical ventilation.
• We generally select a PS level that will deliver
  10-12 ml kg IBW.
• The RCP must remember that this mode is an assist
  only and the patients VT and VE will vary base
  on lung dynamics. There is no guaranteed VT.
• Patient must have an intact ventilatory drive
  for this to work

23
CPAP modespontaneous mode

• application of PEEP without any positive pressure
  breathes.
• CPAP is merely a raised baseline with a flow
  rate with adjustable Fi02
• recruits alveoli which will improve diffusion of
  02
• CPAP can help return a low compliant lung back to
  normal once atelectasis has been resolved. The
  FRC should rise.
• should decrease WOB.
• proper application of CPAP should decrease WOB-
  watch respiratory rates on this

24
CPAP interfaces

• CPAP via the ET tube or a trach tube is called
  CPAP
• CPAP via a nose mask, face mask or full face mask
  is called nasal-CPAP n-CPAP
• Obviously we select the interface based on the
  patients ability to protect his airway

25
n-CPAP indications

• The successful candidate for n-CPAP would be the
  patient who is oriented,
• has good ventilatory drive without excessive WOB
• and who has the ability to protect his airway.

26
n-CPAP contraindications

• Persons at risk for vomiting and aspiration
• persons with skin necrosis,
• claustrophobia.

27
CPAP indications

• Management of the person who is in hypoxemia
  respiratory failure. This patient will have
  refractory hypoxemia without respiratory
  acidosis..
• Treatment of Congestive Heart Failure CHF in
  the patient who has an intact ventilatory drive
  and can keep his PaC02 down. CPAP of 8-12 with
  Fi02 100 is suggested. Egans pp, 1095
•  
• A weaning modality This invasive CPAP may be the
  last step before extubation. Generally a patient
  can be extubated from a CPAP of 5-7 cmH20 or can
  be extubated at a stand-alone PSV of 5-7 cmH20.
•  
• Non-invasive management of persons with
  obstructive sleep apnea OSA

28
APRVa spontaneous mode

• airway pressure release ventilation
• Patient is breathing on two different levels of
  CPAP

29
Initial settings for APRV for ARDS

• The higher CPAP is set with the Phigh, while the
  P low sets the lower pressure.
• The RCP should also set the time interval Thigh
  for Phigh and the time interval Tlowfor Plow
• To initial APRV, the RCP looks to the patients
  Pplateau on PPV and uses that figure for the
  Phigh.
• The Thigh is started at 4 seconds for adults and
  can be progressively increased to 10-15 seconds
• Set the Plow at zero and use the release time
  Tlow to keep the pressure from dropping to zero
• Set the Tlow at about .5 to .8 one time
  constant so that the breath ends with the
  expiratory flow at 50-75 of peak flow

30
What happens if the patient goes apnic?

• During APRV ventilation if the patient was stop
  breathing, the time-cycling between high and low
  pressures would appear similar to PC-IRV.
• So this is a spontaneous mode that happens to
  have a back up of sorts

31
Contraindications to APRV

• persons with COPD or other problems associated
  with air trapping.
• persons with excessively high intracranial
  pressures high ICP

32
Bilevel ventilation

• An alternative to APRV is bilevel ventilation.
  The only difference between bilevel ventilation
  and APRV is that the patient spends more time at
  the Plow lower airway pressure than at the high
  airway pressure Phigh.

33
BiPap- NIPPV

• Non-invasive positive pressure ventilation
• These BiPap breathes tend to be flow or time
  triggered, flow cycled off
• with the operator selecting PIP called IPAP and
  PEEP called EPAP and bleeding in supplementary
  02.
• The newer Vision can get a Fi02.
• http//emedicine.medscape.com/article/1417959-trea
  tment

34
contraindications/hazards of NIPPV

• do not put this device on an apnic patient
  because it is NOT a ventilatorit is a breath
  augmenter.
• Persons who cannot protect their airways
• Hemodynamically unstable patients
• Facial burns or trauma
• Uncooperative patients
• Persons at risk for aspiration vomiting, nose
  bleeds, unconscious, poor gag reflex
• Copious secretions
• Anatomical problems with gas exchange

35
Indications for NIPPV acute care of

• congestive heart disease n-CPAP or BiPap
• COPD patient who doesnt want to be intubated
• recently extubated patient who is at risk of
  failing.
• immune-suppression for whom we may not want to
  risk VAP

36
Indications for long-term NIPPV

• Long-term management of both obstructive sleep
  apnea and central sleep apnea
• Long-term management of patients with skeletal or
  neuromuscular disorders
• Long-term management of the COPD patient who has
  s/s of chronic hypoventilation especially at
  night and who is optimally treated with drugs
  and other care.

37
Initial settings for BiPap

• IPAP at 8 cmH20 and EPAP at 4 cmH20.
• . Increase IPAP in increments of 2 cmH20 to
  deliver more VT.
• To hypoxemia, increase the EPAP in increments of
  2 cm H20.
• Oddly enough, if the EPAP is raised without
  raising the IPAP, the VT might decrease because
  the VT is a function of the change in pressure or
  the delta P ? P

38
The BiPap ST/D

• EPAP/CPAP in this mode, all you get is CPAP
• IPAP in this mode, again, all you get is CPAP.
• Spontaneous mode this is a form of PSV in which
  you select the PS with the IPAP and the PEEP with
  the EPAP. All breaths are patient triggered
• Spontaneous/timed is their version of A/C PC
  with each breath patient or time triggered. In
  this mode you select the bpm
• Timed mode their version of control ventilation
  in which you now select the rate and the
  inspiratory time

39
What is so strange about the BiPAP ST/D circuit?

• only a single, large-bore tubing going from the
  compressor to the patients mask.
• constant leak at the Whisper swivel this will
  leak a minimal amount of gas out of the circuit
  and between the very high flow rates and the
  leak, the patient doesnt rebreathe his C02.
  Never plug up this hole!

40
Adding extra 02 to the BiPap STD without starting
a fire

• add 02 at the mask,
• start machine first before adding 02 so gas will
  not leak back into machine
• never exceed 15 LPM

41
Compare the BiPap STD to the Vision BiPap machine

• The BiPAP ST/D has no 02 inlet
• The Respironics Vision plugs into 50 psig 02
  can get 21 to 100 Fi02
• The BiPAP ST/D has no internal alarm, you must
  buy a separate alarm
• The Respironics Vision can be used for invasive
  ventilation with A/C, SIMV PSV and CPAP as well
  as NIPPV CPAP and S/T
•  

42
Use of critical care ventilators such as BiPap
machines in the ICU.

• As a rule, we would operate these machines in the
  PSV mode with PEEP to mimic the BiPap.
• It is important to understand that the alarms on
  these machines may have to be adjusted out of
  range

43
Dual modes

• combine mandatory ventilation with spontaneous
  ventilation
• IMV intermittent mandatory ventilation in which
  some breaths are mandatory and others are
  spontaneous.
• In this type of breath, the ventilator will give
  a PPV usually based on VC at timed intervals.
  The patient can breathe off a constant flow rate
  or from a demand valve at a VT and flow rate
  determined by his muscle strength, ventilatory
  drive and lung mechanics.

44
Advantages of IMV/ SIMV

• patient comfort
• maintains muscle coordination muscle strength
• reduces V/Q mismatchZone III is being utilized,
• 4 lower PAW and is an excellent weaning
  modality
• less likely to cause air-trapping
•  

45
Disadvantage of IMV/ SIMV

• If the patients PPV support is removed too
  quickly the patient can suffer increased WOB
• We need to monitor the spontaneous VE , RR and
  VT, we may need to increase support by
• increasing the SIMV rate
• adding PS

46
Indications for IMV/SIMV

• IMV is a partial mode of ventilation that usually
  includes dual modes.
• weaning from CMV when the patients ventilator
  muscles are weakened
• an initial ventilator setting when the patient is
  at risk for air trapping and is breathing on his
  own,
• or if the patient who is able to breathe
  partially for himself is at risk for decreased
  CO.
•  

47
The difference between SIMV and IMV

• SIMV stands for synchronized intermittent
  mandatory ventilation.
• The mandatory breath can come in sooner if
  patient triggers within the synchronization
  window of fractions of seconds.

48
Special modes PRVC PRVC

• In a pressure regulated volume control mode, we
  are attempting to deliver the VT because we are
  in VC mode but we want to keep the airway
  pressures low.
• ventilator will attempt to deliver the VT at 5
  cmH20 below a preset pressure setting.

49
Special modes VAPS

• volume assured, pressure support, the ventilator
  will be attempting to deliver a stable VT with PS
  breaths so that the patient has the advantage of
  stable VE as well as the advantages of
• If a PS breath fails to reach the pre-set VT,
  the breath will continue at a constant flow until
  the volume is reached. If the patient got the
  pre-set VT with the PS breath, it stays PS.
• Unlike normal PS, these breaths arent just flow
  triggered, but can be time triggered.

50
Special modes MMV

• Mandatory minute ventilation
• gives the patient extra breaths or extra PS
  pressure to keep a predetermined minimal VE.
• This differs from apnea parameters in that the
  patient doesnt have to actually go apneic for 20
  seconds or more for this to activate. He merely
  needs to have hypoventilation.
•  

51
One problem with MMV

• when the patient starts the rapid, shallow
  breathing associated with respiratory distress.
• If a patient keeps the VE up with rate only, he
  can be in a lot of distress
• It is suggested to keep the maximal high
  respiratory rate 10 BPM above the average

52
Special modes ASV

• adaptive support ventilation the RCP inputs the
  patients IBW and a percentage of the VE.
• The ventilator will deliver a VE based on the
  patients IBW.
•  
• As the patient takes over more of the breathing
  the VE is maintained with PS breaths.
• The level of PS changes to give the VT calculated
  by the machine, The VT will be determined by the
  patients IBW and VD ventilation.

53
Special modes PAV

• In proportional assist ventilation mode similar
  to ASV in that the ventilator will collect data
  about patients elasticity and resistance and
  flow or volume demands in order to arrive at PS
  levels that varies.

54
High frequency ventilation

• controlled ventilation- the patient is sedated
  and paralyzed
• VT of less or equal to the VD anatomical
• respiratory frequencies of 60 BPM-3600 bpm
• All HFV counts on the gas stream going down the
  ET tube (inside) AT THE SAME TIME and the gas
  flow existing (outside stream).

55
How does HFV work

• Penduluft action due to various time constants of
  different portions of the lungs, the gas moves
  from one lobe to another ,
• there is some bulk transfer

56
What are the types of HFV

• high frequency jet ventilation
• high frequency positive pressure ventilation
• high frequency oscillation
• combination of HFJ with CMV

57
Special modes PRVC

• In pressure regulated volume control, an effort
  is made to maintain both a safe level of airway
  pressure and delivered VT.
• In PRVC, the RCP selects a PIP that will not be
  exceeded.
• To keep the VT, at this safe PIP, the
  inspiratory time and the flow rate must vary.

58
Special modes Auto-mode

• in some ventilators selection of the auto-mode
  will allow the ventilator to decrease support as
  a patient starts to take over the WOB.
• The ventilator reverts between a CMV mode and a
  spontaneous mode based on breath by breath
  assessment of the patient

59
Special modes ATC

• Automatic tubing compensation, in this mode the
  ventilator will compensate for the RAW of the ET
  tube.

60
Initial ventilator settings
61
VT, set f and VE

• Full support A/C or SIMV rate 12-16 BPM
• Partial support SIMV below 10 BPM
• 8-10 ml/Kg IBW normal lungs
• 6-8 ml/kg IBW asthma
• 5-8 ml/ kg IBW for ARDS COPD
• VE needs to be 80-100 ml/KgIBW

62
TI and Flow rates

• Inspiratory flow rates of 60-80 LPM for most
• If air hungry raise above 80
• COPD- 60-100 LPM
• Inspiratory times .80-1.2 seconds

63
Flow wave pattern

• Constant flows will decrease inspiratory time and
  help with IE ratios, but can raise the PIP.
• Descending flow curve has the advantage of better
  distribution of gas into the lung, but will
  increase the TI and increase the mPAW
• Sine wave while considered more physiological, a
  classic sine wave may not have enough initial
  flow to satisfy a patient. Like the descending
  flow pattern it will raise the TI and change the
  IE ratio
•  

64
Rise time or Ramp

• in an effort to fine-tune flow patterns, the
  constant flow can be damped by a rise time
  adjustments. When set high, this almost mimics
  an ascending flow pattern.

65
Inspiratory pause

• The temporary use of the inspiratory pause at
  about .5 to 1 second is generally reserved for
  gathering Pplateau

66
Fi02

• 100 is a good place to
• Weaning rapidly to 40-50 after ABG
• Fi02 needs to be weaned about 20 at a step.

67
PEEP

• may be started at zero, PEEP at 5 or less cmH20
  is considered physiological and should not result
  in CV problems-but-- remember any PEEP that
  causes hemodynamic problems is excessive.
• Increase or decrease by units of 2

68
Humidification by HME

• is limited to persons with good fluid balances,
  normal secretions and VE less than 10 LPM and
  normal body temperatures.
• If the patient has a gross leak so that 30 of
  the delivered VT is lost, the HME will not work.
•  

69
Humidification by heated humidifier

• can be used with everyone but are necessary for
  patients with secretions. Keep the temperatures
  close to 330 C /- 2

70
Sighs

• multiple sighs every hour or so. These sigh
  volumes were about 1.5 x the VT.
• important if VT is less than 7 ml/kg

71
s/p lung resection or lung transplants

• need lower VT and faster rates to protect the
  torn lung from rupture.
• Keep the Pplateau at or below 30 cmH20 old
  Egans 1011

72
lobar pneumonia

• place patient on the good lung side so gas goes
  to the bad lung
• avoid PEEP in lobar pneumonia if possible
• Try to prolong the Ti
• Consider double lumen ET tube so we can set two
  ventilators on the patient

73
long-term neuromuscular patients

• more comfortable at higher than usual VT
  decrease the RR of 10-12 ml/kg. These patients
  also tend to want higher flow rates.
• They can be managed with low Fi02-even .21 as
  long as Sp02 is above 90-92
• low PEEP of 3-5 to prevent atelectasis are ok

74
Persons with Congestive Heart failure

• We can start with normal settings, but if the PIP
  and Pplateau are excessive, we need to decrease
  the VT
• PEEP at 10 cmH20 and wean the
• Once the patients compliance gets better, we
  must wean the PEEP
• If the patient has an intact ventilatory drive,
  good VE, he could be maintained on CPAP

75
Initial parameters when High RAW is an issue?

• start with SIMV because this mode is less likely
  to cause air trapping.
• minimize air trapping and auto-PEEP

76
COPD

• SIMV rate between 10-12 BPM decrease this to
  6-8 to allow time to exhale
• start at 60 and raise to100 LPM.
• A COPD patient can be started at 40-50 Fi02
• Use of PEEP with COPD is dangerous, but if the
  set PEEP and the auto-PEEP are kept about the
  same, the gas is more likely to leave the lung
• , keep Sp02 at 90-92 and keep the PaC02 and pH
  close to baseline so the patient will not suffer
  post-hypercapnic alkalosis

77
Asthmatic AHI 2005 CPR CPG pp IV 141

• Alert? may do well on BiPap machine
• SIMV rate 6-10 BPM
• VT of 6-8 ml/ kg IBW
• 80-100 LPM with a descending flow pattern to get
  14 or 15
• Start Fi02 at 100.
• Use of PEEP with asthmatics is dangerous, but if
  the set PEEP and the auto-PEEP are kept the same,
  the gas is more likely to leave the lung.
• permissive hypercapnia,
•