Mechanical ventilation different modes .pdf

Anaesthesia machine , different types of ventilation and different modes

1. MECHANICAL VENTILATION
Guided By-Dr Pankaj Verma
Asst. Proff.
Dept. of Anaesthesiology
VIMSAR Burla.
Presented By-Dr Arpita Rath
PGT 2
Dept. of Anaesthesiology
VIMSAR Burla.
MECHANICAL VENTILATION

2. •Mechanical ventilation is a life support therapy that assists or takes
over breathing in patients with compromised lung function or under
general anaesthesia.
•It is one of the miracles of modern science that acts as a temporary
bridge while a pathologic lung becomes healthy one.
MECHANICAL VENTILATION
INTRODUCTION
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3. CONTENTS
MECHANICAL VENTILATION
HISTORY
BASICS OF MECHANICAL VENTILATION
MODES OF VENTILATION.
NEWER MODES
VENTILATOR ASSOCIATED DISEASES
INTUBATION CRITERIA
WEANING AND EXTUBATION.
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4. HISTORY
•Andreas Vesalius in 1555 was the first
person to talk about positive pressure
ventilation in his book titled “De Humani
Corporis Fabrica”.
•The first description of a ventilator was
of a full-body type negative pressure
ventilator or “tank ventilator” by
Scottish physician John Dalziel in 1838.
•Following the polio epidemic of 1955
(era of iron lungs) , emersoncompany in
bostongave a prototype of positive
pressure lung inflation device which is
the primary mechanism used in today’s
ventilator.

5. Ventilator controls inspiration while expiration is only a passive
process.
The giant looking ventilator is fundamentally made of 3 things :-
MECHANICAL VENTILATION
BASICS
COMPRESSOR INSPIRATORY VALVE EXPIRATORY VALVE
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6. MECHANICAL VENTILATION
Compressor
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7. •There are 3 possible types of breaths a patient can receive on a ventilator.
MECHANICAL VENTILATION
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TYPES OF BREATH:-

8. •Volume breaths-where the
inflation volume is
constant.The ventilator will
deliver a preset tidal
volume.
•Pressure breaths-where
the inflation pressure is
constant.
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BREATH DELIVERY:-

9. P peak or Peak inspiratory pressure (PIP) –
pressure required to deliver the required
tidal volume by overcoming all resistance.
P plateau or Palveoli (Palv) –pressure
needed to maintain lung inflation in
absence of airflow.
Presistance(Pres) –pressure attributed
to airway resistance
Pelastance(Pel) –pressure attributed to
elastic recoil of lung and chest wall.
MECHANICAL VENTILATION
P peak = P res+ P el
Pres
Pel
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10. •End-expiratory pressure(EEP)is the minimum pressure in the alveoli (not airways)
during a ventilatory cycle.
•ZEEP-In the normal lung, there is no airflow at the end of expiration, and the
pressure in the alveoli is equivalent to atmospheric pressure. Since atmospheric
pressure is a zero reference point for breathing, this condition is called zero end-
expiratory pressure, or ZEEP.
•PEEP is an airway pressure strategy in ventilation that increases the end-expiratory or
baseline airway pressure to a value greater than atmospheric pressure. Indications of
PEEP include –refractory hypoxemia or intrapulmonary shunting , decreased FRC or
Auto –PEEP.
•Complications of PEEP-decreased venous return and cardiac output
barotrauma
increased intracranial pressure
alterations of renal functions and water metabolism.
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11. MECHANICAL VENTILATION
How much will
the person
inspire ?
What opens the
INSPIRATORY valve or
what starts inspiration?

12. Trigger :-
•Time :-ventilator initiates according to set frequency , independent of
patient effort.
•Pressure –patients breath produces a decrease in baseline circuit
pressure which starts inspiration.
•Flow –ventilator senses inspiratory flow by the patient and initiates
inspiration.
•Neural –ventilator initiates breath on sensing electrical activity in
diaphragm.
MECHANICAL VENTILATION
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13. Limit :-
If one or more inspiratory variable rises no higher than some preset
values it is called a limit variable.
Limit variable is the one which limits the way gas keeps flowing in the
lungs during inspiration.
It does not terminate inspiration rather it is the maximum limit of a
particular variable throughout inspiration.
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14. Cycle:-
•Changeover from inspiration to expiration where inspiration ends
when some variable has reached a preset value –cycle.
•Time cycle-most common , fixed inspiratory time.
•Flow cycle-when expiratory flow reaches a preset value.
•Pressure cycle –when a preset pressure value is reached. Not used
now.
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15. •It is a graphical descriptions of how a breath is delivered to a patient.
•These include 3 scalars and 2 loops :-
•Convention flow values above the horizontal axis are inspiratory, whereas flow
below the horizontal axis is expiratory.
MECHANICAL VENTILATION
WAVEFORMS
flow versus time
volume versus time
pressure versus time
pressure-volume
flow-volume
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16. MECHANICAL VENTILATION
Scalarswaveform representations of pressure, flow or volume on the y axis vs time on the
x axis. Each scalar represents the entire breath from the beginning of inspiration to the end
of expiration.
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SCALARS:-

17. These graphics are one of the two variables, either pressure or flow, plotted against the
volume during a breath. Each loop consists of an inspiratory and expiratory curve and
allows for evaluation of respiratory mechanics.
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LOOPS:-

18. •There are almost around 23 modes of ventilation available.
•Regardless of which operating mode is selected, it should
achieve four main goals:-
1.provide adequate ventilation and oxygenation
2. avoid ventilator-induced lung injury
3. patient-ventilator synchrony
4.allow successful weaning
Ventilation can be non invasive or invasive .
MECHANICAL VENTILATION
MODES OF VENTILATION
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19. SPONTANEOUS MODE:-
•spontaneoussetting on the ventilator is
not an actual mode
•the frequency and tidal volume during
spontaneous breathing are determined by
the patient.
•Its purpose is:-
(1)To provide adequate inspiratory flow to
the patient in a timely manner,
(2) flow adequate to fulfill a patient’s
inspiratory demand
MECHANICAL VENTILATION
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20. NON-INVASIVE VENTILATION:-
•There are three modes of ventilation available for NIV:
(a)Continuous positive airway pressure (CPAP)
(b) Bilevel positive airway pressure(BiPAP)
(c) Pressure support ventilation (PSV).
The latter two modes of ventilation (i.e., BiPAP and PSV) are also referred to as
noninvasivepositive pressure ventilation (NPPV).
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21. MECHANICAL VENTILATION
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22. Pressure support ventilation (PSV) :-
•PSV is used to lower the work of spontaneous breathing and augment a patient’s
spontaneous tidal volume.
•It applies a preset pressure plateau to the patient’s airway for the duration of a
spontaneous breath
•Typically, the flow pattern associated with pressure support is a steeply
descending tapered flow pattern
•The demand valve flow terminates when it decreases to a preset lower flow limit.
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23. MECHANICAL VENTILATION
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INDICATIONS FOR NIV CONTRAINDICATIONS
End stage COPD patients. Uncooperative ,Unconciousor Unstable
cardiorespiratory status
supporting patients with chronic
ventilatory failure
Trauma or burnsinvolving the face
patients with restrictive chest wall
disease
Air leak syndrome (pneumothorax with
bronchopleural fistula)
neuromuscular disease Copious respiratory secretions
nocturnal hypoventilation Severe nausea with vomiting
Severe gastrointestinal hemorrage.

24. CMV MODE
Controlled mandatory ventilation (CMV), or control
mode.
•All mandatory breaths with preset frequency,
inspiratory time and pressure/volume.
•The patient is properly medicated with a combination of
sedatives, respiratory depressants, and neuromuscular
blockers.
•When to use :-
1.If the patient “fights” the ventilator in the initial stages
of mechanical ventilatory support.
2.Tetanus or other seizure activities .
3.patients with a crushed chest injury in which
spontaneous inspiratory efforts are detrimental.
MECHANICAL VENTILATION
Trigger-Time
Limit-Volume/Flow/Pressure
Cycle –Time
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25. Complication:-
1.potential for apnea and hypoxia if the patient should become accidentally
disconnected.
2.rapid disuse atrophy of diaphragm fibers(18 to 69 hours of complete
diaphragmatic inactivity during mechanical ventilation results in marked
atrophy of human diaphragm myofibers (Levine et al., 2008))
3.diaphragmatic oxidative injury
4.elevated proteolysis
5.Reduced function of the diaphragm
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26. MECHANICAL VENTILATION
VOLUME CONTROL PRESSURE CONTROL
TIDAL VOLUME CONSTANT VARIABLE
PIP VARIABLE CONSTANT
INSPIRATORY TIMESET SET
INSPIRATORY FLOWSET (PATIENT VENTILATIOR
ASYNCHRONY )
VARIABLE (AS PATIENT
DEMANDS)
INSPIRATORY
WAVEFORM
CONSTANT DECELERATING
WHAT TO MONITOR PEAK AIRWAY PRESSURE
PLATEAU AIRWAY PRESSURE
LOW PRESSURE ALARMS
EXPIRED TIDAL VOLUME
EXPIRED MINUTE VOLUME

27. PCV(Pressure Controlled Ventilation)
•In pressure-controlled ventilation (PCV), the breaths
are time-triggered.
•Once inspiration begins ,the pressure plateau is
maintained for a preset inspiratory time in contrast
to that of PS mode where pressure plateau is
maintained as long as the patient maintains a
spontaneous inspiratory flow.
•It is indicated in patients with severe ARDS who
require extremely high peak inspiratory pressures
during mechanical ventilation
MECHANICAL VENTILATION
Trigger-Time
Limit-pressure
Cycle –Time
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28. ASSIST CONTROL
MECHANICAL VENTILATION
Thepatient initatesthe breath and the machine
takes over to complete the breath.
Advantage :-
1.Decreased WOB
2.Patient can control the frequency of breath there
by control the minute volume required to
normalize PaCO2.
Complications:-
alveolar hyperventilation (respiratory alkalosis)
if the pt has inappropriately high respiratory
drive it may to lead an excessive assist
frequency despite a low PaCO
Trigger-Patient (assisted breath)
Time(control breath)
Limit-Volume/Flow/Pressure
Cycle –Volume
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29. IMV(intermittent mandatory ventilation)
Trigger-Time
Limit-Volume/Flow/Pressure
Cycle –Time
•Ventilator delivers control (mandatory) breaths
and allows the patient to breathe spontaneously
at any tidal volume the patient is capable of in
between the mandatory breaths.
•The primary complication associated with IMV
is chance for breath stacking.
•This occurs when the patient is taking a
spontaneous breath and the ventilator delivers
a time-triggered mandatory breath at the same
time.
•If this occurs, the patient’s lung volume and
airway pressure could increase significantly.
•Setting appropriate high pressure limits will
reduce the risk of barotrauma.
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30. SIMV (Synchronized intermittent mandatory ventilation )
•The ventilator delivers either assisted breaths to the
patient at the beginning of a spontaneous breath or
time-triggered mandatory breaths.
•The mandatory breaths are synchronized with the
patient’s spontaneous breathing efforts so as to avoid
breath stacking.
•In between the mandatory breaths, SIMV permits the
patient to breathe spontneouslyto any tidal volume the
patient desires.
•Synchronization Window-The time interval just prior to
time triggering in which the ventilator is responsive to
the patient’s spontaneous inspiratory effort is
commonly referred to as the synchronization window
MECHANICAL VENTILATION
Trigger-Time/Patient
Limit-Volume/Flow/Pressure
Cycle –Time
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31. •Advantages:-
(1) maintains respiratory muscle strength/avoids muscle atrophy,
(2) reduces ventilation to perfusion mismatch
(3) decreases mean airway pressure, and
(4) Facilitates weaning.
Disadvantage :-
•The primary disadvantage associated with SIMV is the desire to wean the
patient too rapidly, leading first to a high work of spontaneous breathing
and ultimately to muscle fatigue and weaning failure.
MECHANICAL VENTILATION
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32. PRVC (Pressure-regulated volume control )
•Provides volume-controlled breaths with the lowest pressure possible by altering
the flow and inspiratory time.
•PRVC was first available in the Siemens 300. Similar modes to PRVC in subsequent
ventilators are known as: adaptive pressure control (Servo-I, Maquet), AutoFlow
(Evita XL, Drager), adaptive pressure ventilation (Galileo, Hamilton).
•PRVC is used primarily to achieve volume support while keeping the peak
inspiratory pressure (PIP) at a lowest level possible.
•By altering the peak flow and inspiratory time in response
to changing airway or compliance characteristics
by the machine itself.
MECHANICAL VENTILATION
Trigger-Time/patient
Limit-pressure
Cycle –volume
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33. ASV(adaptive support ventilation)-
•It is a dual control mode that provides a mandatory minute ventilation.
•Basically, ASV uses the Otis Equation to calculate the optimal frequency that corresponds
with the lowest work of breathing.
•Once the target minute ventilation is set, the ventilator uses test breaths to measure the
system compliance, airway resistance, and any intrinsic PEEP, and the ventilator selects to
provides the frequency, inspiratory time, I:E ratio, and high pressure limit for mandatory
and spontaneous breaths.
•If there is no spontaneous triggering effort, the ventilator delivers the preselected tidal
volume, inspiratory time, and I:E ratio.
•As the patient begins to trigger ,the number of mandatory breaths decreases and the
pressure support level increases until a calculated tidal volume is able to provide
adequate alveolar volume (i.e., tidal volume 5 alveolar volume 1 2.2 mL/kg of deadspace
volume).
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NEWER MODES

34. PAV(Proportional Assist Ventilation)-
•Uses variable pressure to provide pressure support in proportion to the patient’s
pulmonary characteristics (elastance and airflow resistance) and demand (volume or
flow)
•PAV is set to overcome 80% of the elastance and airflow resistance.
•PAV is achieved by a positive feedback control that amplifies airway pressure in
proportion to instantaneous inspiratory flow and volume.
•Advantages
1.ability to track changes in breathing effort over time.
2.Less asynchrony due to more uniform breathing pattern.
3.Decreases WOB in vet dependant COPD pts.
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35. VAPS(Volume Assured Pressure Support) –
•A mode of ventilation that assures a stable tidal volume by incorporating
inspiratory pressure support ventilation (PSV) with conventional volume-assisted
cycles (VAV).
•This combination provides an optimal inspiratory flow during assisted/controlled
cycles, reducing the patient’s work of breathing and assures stable tidal volume in
patients with irregular breathing patterns.
•Since VAPS may prolong the inspiratory time automatically, patients with airflow
obstruction should be monitored closely in order to prevent air trapping and
other undesirable cardiovascular effects associated with prolonged inspiratory
time.
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36. •It uses high-frequency, low volume oscillations.
•These oscillations create a high mean airway pressure, which improves gas exchange in
the lungs by opening collapsed alveoli (alveolar recruitment) and preventing further
alveolar collapse.
•The small tidal volumes (typically 1 –2 mL) limit the risk of alveolar overdistension and
volutrauma.
•For optimal results, an alveolar recruitment maneuver, is recommended just prior to
switching from conventional mechanical ventilation (CMV) to HFOV
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HFOV-High frequency oscillatory ventilation (HFOV)

37. •The frequency range for the oscillations is 4 –7 Hz (1 Hz is one oscillation per second
or 60 oscillations/min, so a range of 4 –7 Hz is 240 –420 oscillations/min), and the
specific frequency selected is determined by the arterial pH
•The initial pulse amplitude is set at 70 –90 cm H2O.
•Clinical trials comparing HFOV with CMV, primarily conducted in patients with ARDS,
have shown a 16 –24% increase in the PaO2/FIO2 ratio associated with HFOV
However, HFOV has not been compared with lung protective ventilation (which also
shows a survival benefit) so it is not known if HFOV representsan advance over lung
protective ventilation in patients with ARDS.
•Disadvantages:-
•1. A special ventilator is needed, along with trained personnel to operate the device.
•2. Cardiac output is often decreased during HFOV because of the high mean airway
pressures. This effect requires augmentation of the intravascular volume during
HFOV.
•3. Aerosolized bronchodilators are ineffective during HFOV.
MECHANICAL VENTILATION
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38. •APRV employs prolonged periods of spontaneous breathing at
high end-expiratory pressures, which are interrupted by brief
periods of pressure release to atmospheric pressurethereby
achieving near complete recruitment of collapsed alveoli.
•APRV is a variant of continuous positive airway pressure
(CPAP) but PIPpressures are lower during APRV than during
CMV (at equivalent tidal volumes)
•The improvement in arterial oxygenation with APRV occurs
gradually over 24 hour
•The benefits of APRV are lost if the patient has no
spontaneous breathing efforts.
•Disadvantages:-Decreases CO.
•Relative C/I-COPD , Severe asthma.
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Airway Pressure Release Ventilation(APRV)

39. NeurallyAdjusted Ventilatory Assist
(NAVA)
•It uses a patient's diaphragm's electrical activity to control the timing
and degree of breathing support.
•NAVA can be used in both invasive and non-invasive modes.
•An array of nine miniaturized electrodes are embedded within a
catheter (Edi catheter )which is positioned in the lower esophagusat
the level of the diaphragm.
•Advantges:-
1.Patient-ventilator synchrony
2.Air leaks-It has shown that NAVA continues to trigger effectively
even in the presence of 75% air leaks
3.Used in neonates to prevent intubation, allow early extubation,
and deliver nasal continuous positive airway pressure
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40. MECHANICAL VENTILATION

41. MECHANICAL VENTILATION
WHEN TO INITIATE
MECHANICAL VENTILATION ?

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43. MECHANICAL VENTILATION
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44. MECHANICAL VENTILATION

45. VILI (ventilator induced
lung injury)
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VENTILATOR ASSOCIATED DISEASES
1.VOLUTRAUMA-High inflation volumes could
produce diffuse pulmonary infiltration that
resembles pulmonary edema.
2. ATELECTRAUMA-Repetitive opening
and closing of small airways during
positive pressure ventilation can damage
the airway epithelium, possibly by
generating excessive shear forces. This
type of lung injury is called atelectrauma.

46. 3. BIOTRAUMA-PPV promote
proinflammatory cytokine release from the
lungs at inflation volumes that can trigger
the systemic inflammatory response
syndrome, and can lead to inflammatory
injury in the lung as well as other organs.
This means that mechanical ventilation can
be a source of inflammatory-mediated
multiorgan failure.
4.BAROTRAUMA-Positive pressure
ventilation can also produce air leaks from
a rupture in the airways and distal
airspaceswhich may result in
pneumothorax, or
pneumomediastinumandor subcutaneous
emphysema or pneumoperitoneum.
MECHANICAL VENTILATION
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47. Ventilator-
associated
pneumonia (VAP)
•VAP is a severe form of hospital-acquired infection.
Approximately 25% of all infections acquired in intensive
care units are due to VAP.
•The risk of VAP is highest immediately after intubation and
initiation of mechanical ventilation.
•For the first 5 days, the incidence of VAP is 3%.
•The rate decreases to 2% per day for the next 5 days, and
1% per day thereafter.
MECHANICAL VENTILATION

48. MECHANICAL VENTILATION
WHEN TO EXTUBATE ?

49. •It is the process of withdrawing mechanical ventilatory
support and transferring the work of breathing from the
ventilator to the patient.
•Weaning success refers to the abscess of ventilatory
support for atleast48 hours after extubation.
•Weaning failure refers to either :
-failure of spontaneous breathing trial
-Need to reintubate within 48 hours of extubation.
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To wean
or not to
wean
WEANING

50. CRETERIA FOR WEANING READINESS:-
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(SBT)

51. SBT AND PARTIAL VENTILATORY SUPPORT PROCEDURES
•SBT –A major diagnostic test.
•SIMV should be avoided as a stand-alone weaning modality.
•Weaning with PSV-adjust the pressure until a desired
spontaneous VT (10 to 15 mL/kg) or spontaneous frequency
(<25/min) is obtained and gradually decreased by 3 to 6 cm
H2O increments until a level close to 5 cm H2O is reached.
•SIMV+ PSV , low level PS, CPAP or ATC can be used along
with SBT.
•Newer modes like VS , VAPS APRV are useful.
MECHANICAL VENTILATION
•Once a decision is made to proceed with weaning, the patient may be discontinued from
full ventilatory support and placed on a spontaneous breathing mode via the ventilator or
T-tube (Brigg’s adaptor) for up to 30 minutes.
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52. MECHANICAL VENTILATION
WEANING PROTOCOL
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53. •Extubationmay be considered when the
patient’s blood gases and vital signs
remain satisfactory.
•The criteria for passing includes normal
respiratory pattern (i.e., absence of rapid
shallow breathing), adequate gas
exchange, and hemodynamic stability.
•Failure of weaning may be related to the
development of spontaneous breathing
pattern that is rapid (high frequency) and
shallow (low tidal volume).
•
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54. MECHANICAL VENTILATION
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55. REFERENCES:-
•Clinical application of mechanical ventilation 4
th
edition
•Marino the ICU book 4
th
edition
MECHANICAL VENTILATION

56. •THANK YOU
MECHANICAL VENTILATION
THANK YOU