Subject Characteristics

1
Bi-level Positive Airway Pressure BYAHMAD
YOUNES PROFESSOR OF THORACIC MEDICINE Mansoura
faculty of medicine
2
Non-invasive ventilation

• Non-invasive ventilation refers to the
  application of ventilatory assistance without the
  use of an invasive airway.
• In the vast majority of cases therapy will be
  delivered with positive pressure devices ,
  although a few individuals still use negative
  pressure devices.
• Negative pressure devices present a number of
  difficulties with regard to home ventilation
  including bulkiness, fit ,comfort, they can
  induce significant upper airway obstruction ,
  rendering therapy ineffective.

3
Non-invasive ventilation

• Positive pressure therapy may be delivered with
  either volume or pressure preset ventilators .
• 1-Volume preset ventilation delivers a stable
  tidal volume irrespective of the patients
  pulmonary system mechanics (compliance,
  resistance and active inspiration) .
• 2- Pressure preset ventilation delivers a set
  pressure during inspiration and expiration, and
  changes in the patients pulmonary mechanics
  directly influence the flow and the delivered
  tidal volume .

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What is a mode

• A mode of mechanical ventilation has three
  essential components
• 1- The control variable (the mechanical breath
  goal e.g. a set pressure or a set volume )
• 2- The breath sequence
• 3- The target scheme
• Inspiration is an active process ,driven either
  by the patients effort ,the ventilator or both .
• The machine can control only the volume (and
  flow) or the pressure given.
• The breath can be described on the basis of what
  triggers the breath what limits it (the maximum
  value of a control variable)and what ends (cycles
  ) it.

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Modes of ventilation

• Volume controlled breath is triggered by the
  patients or by the machine , limited by flow and
  cycled by volume.
• Pressure controlled breath is triggered by the
  patients or by the machine , limited by pressure
  and cycled by flow or time.
• The breath sequence
• 1- Control mode (timed) all breaths are
  controlled by the machine (but can be triggered
  by the patient)
• 2- Assisted mode (spontaneous) all breaths are
  spontaneous .
• 3- Assisted /control (spontaneous/ timed)
  patient can take spontaneous breaths between
  mandatory breaths .

6
The target scheme

• The ventilator settings and programming that
  dictate its response to the patients lung
  compliance ,lung resistance ,and respiratory
  effort.
• The regulation can be
• 1-simple as controlling pressure in pressure
  controlled mode or
• 2- can be based on a complicated algorithm as in
  dual mode of ventilation ( AVAPS).

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Non-invasive ventilation

• Most studies evaluating these two modes in
  patients with chronic respiratory failure have
  shown equivalent effects with respect to
  maintaining nocturnal gas exchange and improving
  daytime blood gases.
• Due to lower cost and greater patient comfort ,
  most patients in the majority of centres are now
  prescribed pressure preset devices, mostly
  commonly , bi-level machines.
• Volume ventilators are recommended for patients
  with the most severe respiratory failure
  including those with tracheostomy and when
  continuous or near continuous ventilatory support
  is needed.
• A switch from pressure to volume preset
  ventilation may also be required in patients who
  are adherent to pressure preset ventilation but
  who fail to respond to treatment .

8
Non-invasive ventilation

• Volume preset ventilators are usually set in an
  assist/control or control mode of support.
• No difference in blood gas improvement, lung
  function or compliance with therapy was seen
  between the two modes.
• Pressure preset ventilators may be set in an
  assist (spontaneous) mode where each breath is
  patient triggered an assist/control
  (spontaneous / timed) mode where breaths may
  be patient or machine triggered and a control
  (timed) mode where all breaths are machine
  triggered only .

9
Non-invasive ventilation

• The spontaneous mode has been used in patients
  able to trigger the ventilator consistently,
  whereas the spontaneous/timed mode is used when
  the ability of the patient to trigger the device
  reliably is reduced due to poor or absent
  inspiratory flows being generated (e.g.
  respiratory muscle weakness, drive to breathe is
  reduced or absent, or specific characteristics of
  the patients pulmonary mechanics), where the
  goal of therapy is to control the respiratory
  pattern .
• The pressure settings used in bilevel devices
  include the inspiratory positive airway pressure
  (IPAP) and expiratory positive airway pressure
  (EPAP), with the difference between the two
  determining the level of pressure support

10
Bi-level Positive Airway Pressure

• Bi-level PAP (BiPAP) was developed in mid 1990's
  by Respironics Corporation, trademarked 'BiPAP'.
• Since BiPAP is a trademark, other companies use
  different terms, such as 'bilevel', VPAP
  (variable positive airway pressure), and "duo."
• One internet ad shows 4 different bilevel
  machines from 4 different manufacturers only
  Respironics' machine is "BiPAP."
• Whereas CPAP sets a single pressure above the
  ambient pressure, BiPAP sets two pressures above
  the ambient, a higher (IPAP) and a lower (EPAP),
  e.g., 10/5 cm H2O . Note that both pressures are
  always above ambient.

11
Pressure curve when BiPAP 10/5 cm H2O now the
pressure is higher on inspiration than on
expiration, but both pressures are above ambient.
NOTE BiPAP is equivalent to PSV (pressure
support ventilation) PEEP (positive
end-expiratory pressure) in the intubated
patient in that situation PEEP is the same as
EPAP.
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Bi-level Positive Airway Pressure

• Bi-level Positive Airway Pressure therapy with a
  variable pressure setting would conceivably
  decrease the amount of pressure against which the
  patient exhales, thereby decreasing abdominal
  muscle recruitment and consequent respiratory
  discomfort during the expiratory cycle
• During the inspiratory cycle, the greater level
  of pressure assist would combat the inspiratory
  flow limitation suffered by the upper airway . An
  additional benefit with bi-level PAP is the
  greater tidal volume ( VT) and unloading of the
  respiratory muscles, when compared to CPAP.
• The difference between the IPAP and EPAP could be
  considered as pressure support level that could
  augment the inspired VT. This feature can be
  exploited to combat non-obstructive
  hypoventilation that may occur due to a host of
  conditions.

13
Bi-level Positive Airway Pressure

• In adults, the maximum IPAP setting for bi-level
  PAP is not to exceed 30 cm H2O, and the minimum
  difference between IPAP and EPAP level should not
  be lt 4 cm H2O.
• A transition from CPAP to bilevel PAP is
  encouraged when the CPAP level approaches 15 cm
  H2O. This is because exhalation against CPAP
  levels approaching 15 cm H2O can be uncomfortable
  for most patients.
• Bi-level PAP therapy was not superior to
  conventional CPAP therapy from an adherence
  standpoint.
• The cycling of the device from IPAP to the EPAP
  and vice-versa may be triggered by the
  spontaneously breathing patient (spontaneous
  mode) or by a set respiratory rate programmed
  into the device (timed mode).
• The sensitivities or the triggering threshold for
  causing the device to cycle in the spontaneous
  mode may be based on pressure, flow-contour,
  hardwired timing, or a proprietary combination of
  such measures.

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Rise time , trigerring and cycling
15
Bi-Flex comfort feature
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Ramp comfort feature
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Bi-level Positive Airway Pressure

• Dys-synchronous cycling between the patient and
  the device can be uncomfortable and could lead to
  hyperinflation and further dys-synchrony.
• In some older devices the triggering
  sensitivities could be adjusted by the physician,
  but in most modern bi-level PAP devices for home
  use the technology has veered in favor of
  automation and higher levels of sensitivity.
• The rate of pressurization from EPAP to IPAP
  level (the rise time) can be adjusted to climb
  more briskly or more slowly. Such a feature may
  need to be adjusted for individual patient
  comfort .
• Some reports suggest that a brisk response (or
  shorter rise time) may have some inherent
  oscillatory behavior that may set the stage for
  emergent central ,However, the effect of rise
  time on emergent central apneas has not been
  demonstrated in clinical studies outside of
  mathematical or bench models.

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Autotitrating bilevel devices

• A recent innovation is that of autotitrating
  bilevel devices. The algorithms of these machines
  are designed to automatically titrate pressure
  support levels, and in some devices EPAP, based
  on minute ventilation or flow targets.
• There is mounting evidence for the use of these
  devices in managing sleep disordered breathing in
  patients with central sleep apnea / CheyneStokes
  respiration .
• There is currently a paucity of data and clinical
  experience with the algorithms and technology to
  automatically titrate ventilatory support in
  patients with chronic respiratory failure .
  Consequently, it is not possible to make
  recommendations about the role and effectiveness
  of autotitrating bilevel devices for chronic
  respiratory failure at the present time

19
The administration of a backup rate (timed mode)
during bi-level PAP therapy may be considered
under 2 circumstances.

• 1- The backup rate could be considered in
  patients with alveolar hypoventilation, with or
  without chronic respiratory insufficiency
  (elevated arterial PCO2 ) of various etiologies,
  which is primarily aimed at increasing minute
  ventilation (VE) and resolving the
  hypoventilation.
• 2- Another circumstance would be to treat central
  sleep apnea or prevent the appearance of emergent
  central apneas in patients undergoing PAP therapy
  for OSA.
• In both cases, the choice of the backup rate
  seems arbitrary and is probably best guided by
  polysomnography resolution of central apneas or
  persistent hypoxemia due to alveolar
  hypoventilation (SpO2 lt 88 in the absence of
  obstructive hypopneas or apneas as an indirect
  measure of hypoventilation).
• In general, a backup rate set at 2 breaths below
  the patients spontaneous rate during calm
  wakefulness breathing with titration upwards at
  2-breath increments can be considered.
•  

20
Auto-bilevel positive airway pressure with a
minimum (EPAP) of 6 cm H2O and a maximum (IPAP)
of 25 cm H2O.
21
Principal Indications

• Non-acute setting 1) When CPAP doesn't work for
  sleep apnea. 2) For patients with chronic CO2
  retention who also have sleep apnea ( OHS). 3)
  For patients with neuromuscular disease who need
  some assistance with nocturnal ventilation.
• Acute setting Pulmonary edema or COPD
  exacerbation, when there is CO2 retention and a
  desire to avoid endotracheal intubation.

22
How is the pressure applied non-invasively?

• Same as with CPAP, but machine used is designed
  to deliver BiPAP.
• S9 VPAP S Bilevel VPAP 111
  SOMNOvent auto-S/ST BiPAP S/T
• What kind of mask is used?
• Same as for CPAP

23
The nasal mask (left) and nasal pillows (middle)
and full face mask (left)
24
Medicare Coverage Guidelines

• Same criteria for CPAP
• Face-to-face clinical evaluation by treating
  physician prior to sleep study
• Medicare-covered sleep test that shows AHI 15
  event/hr. or higher, or AHI 5-14 events/hr. with
  documentation of excessive daytime sleepiness,
  impaired cognition, mood disorders or insomnia or
  hypertension, ischemic heart disease, or history
  of stroke and CPAP has been tried and proven
  ineffective .
• Note that there are additional criteria for
  continued coverage, including a face-to-face
  evaluation between the 31st and 90th day of
  treatment.

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VOLUME-TARGETED BiPAP

• Volume-targeted bilevel positive airway pressure
  (VT-BPAP) has been developed in which the
  IPAP-EPAP difference is automatically adjusted to
  deliver a target tidal volume.
• VT-BPAP has the potential advantage of
  automatically varying the PS to deliver a
  targeted tidal volume if the condition of the
  patient changes. For example, if respiratory
  muscle strength declined and the tidal volume
  decreased, the device would deliver higher PS to
  return the delivered tidal volume to the targeted
  level.
• VT-BPAP can be used in the S, ST, or T mode.
• VT-BPAP device is available (Average Volume
  Assured Pressure Support AVAPS,
  Philips-Respironics).

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BiPAP AVAPS "Average Volume Assured Pressure
Support," is a variant of BPAP that automatically
adjusts pressure support to meet changing patient
needs while maintaining a target tidal volume.
28
Ideal body weight

• Estimated ideal body weight in (kg)Males IBW
  50 kg 2.3 kg for each inch over 5
  feet.Females IBW 45.5 kg 2.3 kg for each
  inch over 5 feet.
• Estimated adjusted body weight (kg)If the actual
  body weight is greater than 30 of the
  calculated IBW, calculate the adjusted body
  weight (ABW) ABW IBW 0.4(actual weight -
  IBW)
• The IBW and ABW are used to calculate medication
  dosages when the patient is obese.
• This formula only applies to persons 60 inches
  (152 cm) or taller.

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VOLUME-TARGETED BPAP

• Comparing BPAP and AVAPS (both in the ST mode) in
  patients with OHS. AVAPS resulted in a slightly
  higher ventilation and lower PaCO2 without any
  better sleep quality or quality of life measures
  compared with BPAP-ST. On AVAPS, the minute
  ventilation was greater than on BPAP but sleep
  quality was comparable between the two NPPV
  modes.
• When VT-BPAP is used, the purpose of a
  polysomnography PAP titration is to select a
  level of EPAP that eliminates obstructive events
  (obstructive apnea and hypopnea) and document
  that the device does deliver adequate tidal
  volumes.

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Intelligent Volume Assured Pressure Support (
iVAPS )

• Intelligent. Automatic. Personalized.
• Maintain a preset target alveolar minute
  ventilation
• Monitors delivered ventilation
• Adjusts pressure support
• Provides an intelligent backup breath
• Two mechanisms independent of one another
• 1-Variable Pressure Support to guarantee Alveolar
  Ventilation
• 2- iBR intelligent Back-up rate

31
VPAP ST with iVAPS
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Why Alveolar Ventilation?

• Gas exchange only occurs at alveolar level
• We have a continuous demand for a supply of O2
  and removal of CO2
• Conducting airways do NOT participate in gas
  exchange

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Anatomical Dead space

• Inspired/expired air remaining in conducting
  airways
• Not involved in gas exchange
• Correlation between patients height and dead
  space (Vd)
• Height is used to calculate anatomical dead space
  (Vd) for each breath of air (Tidal Volume)
• Example dead space volume (Vd) 120 ml for
  height 175 cm or 70 inches

34
Anatomical dead space in relation to height of
the patient
35
Alveolar Ventilation

• Vt (500ml) Vd (120ml) alveolar ventilation
  for one breath
• 500 - 120 380 ml participates in gas exchange
  for each breath
• Vta x RR (respiratory rate) Va (minute alveolar
  ventilation) 0.380 x 15 5.7L/min
• Benefits Of Alveolar Ventilation
• Supply of O2 (PaO2) .Normal 80 100 mm Hg
• Removal of CO2 (PaCO2) . Normal 35 45 mm Hg
• Alveolar ventilation provides necessary gas
  exchange to satisfy metabolic demand

36
As alveolar ventilation drops , iVAPS rapidly
increase pressure support until target Va is
reached, and as alveolar ventilation increase ,
iVAPS rapidly decrease pressure support .
37
Intelligent back up rate (iBR) stays out of the
way at 2/3 spontaneous rate whenever the patient
spontaneously triggers above 2/3 of the target
. once the patient rate reach minimum back up
rate (2/3 of the target ) iBR increase towards
patient spontaneous rate to maintain alveolar
ventilation .Once spontaneous trigering returns,
iBR drops back to 2/3 of the target / spontaneous
rate.
38
Auto-TriLevel

• The auto-TriLevel principle by Weinmann combines
  two proven types of therapy auto-CPAP and
  BiLevel into a synthesis that offers the most
  therapy effectiveness.
• Your benefits with these products
• Therapeutically effective maximum and mean
  pressures that are lower than BiLevel with the
  same tidal volume for fewer side effects such as
  leakage.
• Its like a new titration every day adjusts to
  patients high variability .
• Effortless titration and monitoring .

39
Auto-TriLevel

• IPAP inspiratory pneumatic splinting of the
  airways (ventilation)
• EPAP easier exhalation at a low expiratory
  pressure level for a pleasant breathing sensation
• Additional end-expiratory pressure (EEPAP)
  required minimum pressure for adequate splinting
  of airways during phase when risk of collapse is
  highest
• PDIFF (? IPAP-EPAP) need-oriented ventilation
  support by means of changes between inspiratory
  (IPAP) and expiratory (EPAP) pressure levels

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Auto-TriLevel

• Reduced mean and maximum therapy pressure under
  TriLevel Results of a bench test comparison with
  BiLevel therapy.
• SOMNOvent auto-ST is the worlds first automatic
  BiLevel device that permits goal-oriented therapy
  settings(SCOPES).
• With the combination of the autoTriLevel
  principle and the automatic trigger WMtrak, this
  device delivers the greatest effectiveness,
  reliability and breathing comfort simply the
  fastest therapy results.
• Particularly for cases of complicated SDB,
  SOMNOvent auto-S, convinces with its intelligent
  combination of automatic BiLevel S therapy and
  auto-CPAP.

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Auto-TriLevel

• Auto-bilevel spontaneous (SOMNOvent auto-S ).
• Auto-bilevel spontaneous/timed (SOMNOvent auto-ST
  ).
• Anti-cyclic modulated ventilation (SOMNOvent
  auto-CR ).

43
ASV is a variant of BPAP that was developed to
treat Cheyne-Stokes central apnea. Both ASV and
BPAP devices with a backup rate are approved for
use with patients with central apnea and complex
sleep apnea
44
ASV is BiPAP with a twist. The IPAP and EPAP can
vary, depending on the patient's needs. In some
ASV-type machines , the EPAP is fixed and only
the IPAP changes in others both can
change.Basically, in ASV one or both pressures
is continously adjusted, so that the ventilation
delivered to the patient 'adapts' to the
situation.
45
SomnoVent CR
Respironics autoSV ResMed VPAP Adapt SV
46
The top graph is pressure and bottom is flow.
Note that EPAP is set at 5 cm H2O. The IPAP is
variable. When central apnea ensues , the machine
senses less air flow and ratchets up the IPAP,
eventually reaching the pre-set limit of 15 cm
H2O. The prescription for this patient would
read "IPAP 5, PS 3-10."
47
A peak flow target is established around the
4-minute average and the machine changes the air
delivery as needed, to deliver 95 of the target,
as shown below.
48
Dynamic pressure support inversely proportionate
to peak flow
49
Periodic breathing treated with BiPAP auto SV
50
Trilevel ASV uses three different pressure levels
over the course of the breathing cycle. The IPAP
pressure provides the inspiratory splint and
ventilation. Expiratory pressure is varied
between a lower level at the start of expiration
(EPAP) and a higher level at the end of
expiration (EEPAP).
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Confusing Points Clarified

• BiPAP is used for non-invasive ventilation. It is
  designed to augment alveolar ventilation because
  it delivers two pressures, one higher IPAP and
  one lower EPAP however, both IPAP and EPAP are
  above ambient presure.
• BiPAP is the same as PSV PEEP in the intubated
  patient.
• BiPAP is actually a trademark of Philips
  Respironics, and so cannot be used in advertising
  by other manufacturers. ResMed Corporation, for
  example, uses the term "Bilevel" instead of
  BiPAP.
• Many machines are on the market that can deliver
  BiPAP as somnovent ST .

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Confusing Points Clarified

• Also confusing is that BiPAP comes in several
  'modes' -- all variations on the simple two
  pressure model
• S (Spontaneous) Mode. The device triggers IPAP
  when flow sensors detect spontaneous inspiratory
  effort and then cycles back to EPAP.
• T (Timed) Mode. Here the IPAP/EPAP cycling is
  purely machine-triggered, at a set rate,
  typically expressed in breaths per minute.
• S/T (Spontaneous/Timed) Mode. Here the machine
  triggers to IPAP on patient's inspiratory effort,
  but there is also a 'backup" rate. This rate is
  set to ensure that patients still receive a
  minimum number of breaths per minute if they fail
  to breathe spontaneously. However, this is not a
  ventilator mode and will not provide life support
  for the continously apneic patient.

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Confusing Points Clarified

• While BiPAP is generally better than CPAP for
  patients with CO2 retention, or who need
  augmentation in alveolar ventilation, there is no
  rule of thumb about which BiPAP mode is 'best'.
  That can only be determined with a careful
  titration of pressures in the hospital or sleep
  lab.
• BiPAP AVAPS machine designed specifically for
  patients with hypoventilation disorders (e.g.,
  restrictive thoracic disorders, obesity
  hypoventilation syndrome, some cases of central
  apnea and COPD). Not to be confused with ASV,
  AVAPS is not for complex sleep apnea or sleep
  apnea unresponsive to CPAP and BiPAP (which are
  the indications for ASV).

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