Title: Subject Characteristics
1Bi-level Positive Airway Pressure BYAHMAD
YOUNES PROFESSOR OF THORACIC MEDICINE Mansoura
faculty of medicine
2Non-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.
3Non-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 .
4What 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.
5Modes 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 .
6The 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).
7Non-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 .
8Non-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 .
9Non-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
10Bi-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.
11Pressure 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.
12Bi-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.
13Bi-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.
14Rise time , trigerring and cycling
15Bi-Flex comfort feature
16Ramp comfort feature
17Bi-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.
18Autotitrating 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
19The 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. -
20Auto-bilevel positive airway pressure with a
minimum (EPAP) of 6 cm H2O and a maximum (IPAP)
of 25 cm H2O.
21Principal 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.
22How 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
23The nasal mask (left) and nasal pillows (middle)
and full face mask (left)
24Medicare 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.
25VOLUME-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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27BiPAP 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.
28Ideal 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.
29VOLUME-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.
30Intelligent 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
32Why 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
33Anatomical 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
34Anatomical dead space in relation to height of
the patient
35Alveolar 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
36As alveolar ventilation drops , iVAPS rapidly
increase pressure support until target Va is
reached, and as alveolar ventilation increase ,
iVAPS rapidly decrease pressure support .
37Intelligent 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.
38Auto-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 .
39Auto-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
40Auto-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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42Auto-TriLevel
- Auto-bilevel spontaneous (SOMNOvent auto-S ).
- Auto-bilevel spontaneous/timed (SOMNOvent auto-ST
). - Anti-cyclic modulated ventilation (SOMNOvent
auto-CR ).
43ASV 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
44ASV 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.
45SomnoVent CR
Respironics autoSV ResMed VPAP Adapt SV
46The 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."
47A 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.
48Dynamic pressure support inversely proportionate
to peak flow
49Periodic breathing treated with BiPAP auto SV
50Trilevel 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).
51Confusing 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 .
52Confusing 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.
53Confusing 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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