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Bi-level Positive Airway Pressure BY AHMAD YOUNES PROFESSOR OF THORACIC MEDICINE Mansoura faculty of medicine – PowerPoint PPT presentation

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Title: 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 .

4
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.

5
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).

7
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.
12
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.

14
Rise time , trigerring and cycling
15
Bi-Flex comfort feature
16
Ramp comfort feature
17
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.

18
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.

25
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).

26
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27
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.

29
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.

30
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
32
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

33
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

40
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.

41
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42
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).
51
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 .

52
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.

53
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).

54
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