1. VENTILATOR SETTINGS &
THEIR CLINICAL APPLICATION
Guided By-
Dr. R L Suman
(Assoc. prof.)
Presented by-
Jaskaran singh
(Resident doctor)
Chairperson & Head-
Dr.Suresh Goyal
2. Objectives
1. Pulmonary physiology
2. Assisted ventilation
3. Operating mode of ventilation
4. Case scenarios in neonate
5. Case scenarios in children
4. The Airways
• From trachea, the air passes through 10- 23 generations.
• First 16 generations = CONDUCTING ZONE, Contain no alveoli, No
gas exchange Anatomic dead space.
• 17th - 19th generation = TRANSITIONAL ZONE, Alveoli start to
appear, in the respiratory bronchioles.
• 20th - 22nd generations = RESPIRATORY ZONE, Lined with alveoli,
alveolar ducts and alveolar sacs, which terminate the tracheobronchial
tree
5.
6. • Gas Exchange– Oxygenation & Ventilation (CO2 removal)
• Acid-Base Balance -- Participate in acid-base balance by removing
CO2 from the body
• Phonation
• Pulmonary Defense Mechanisms
• Pulmonary Metabolism and the Handling of Bioactive Materials
Lung Functions
7. • Change in volume (Lung expansion) produced by per unit change in pressure
(Work of Breathing)
• Denotes the Ease of Distensibility of the lung and chest wall
• Compliance is inverse of elasticity or elastic recoil
• Low CL= Difficult lung expansion (Stiff Lung) High WOB
1. Usually related to condition that reduces FRC
2. Have a restrictive lung defect,low lung volume,low minute ventilation
3. May be compensated by increased rate.
Eg.HMD
• High CL= Incomplete exhalation (lack of elastic recoil of lung) & CO2 elimination.
1. Conditions that increases FRC.
2. Steep slope on P-V curve.
3. Have an obstructive lung defect,airflow obstruction,incomplete exhalation,poor gas
exchange.
• E.g. Emphysema
Lung Compliance (CL = ΔV ÷ ΔP)
8.
9.
10. Lung Compliance Changes and the P-V Loop
Volume (mL)Volume (mL)
Preset PIP
VTlevels
PPawaw (cm H(cm H22O)O)
COMPLIANCE
Increased
Normal
Decreased
COMPLIANCE
Increased
Normal
Decreased
PressureTargetedVentilation
13. • Change in pressure per unit change in flow of gases.
• Due to friction b/w gas and air conducting system (Airways & ET tube)
• Airway resistance = inversely proportional to its radius raised to the 4th power.
• If airway lumen decreased half the resistance/work of breathing 16 times
• Newborns and young infants have inherently smaller airways, are especially prone
to increase in airway resistance from inflamed tissues and secretions.
• High Resistance in dis. with airway obstruction like MAS and BPD
• During IMV: Airway resistance varies directly with length of ET & inversely with
internal diameter of ET
• Cut ET short*, Use largest appropriate ET size, Suction regularly
Airway Resistance = (PIP-PEEP) ÷ Flow
14. • Resistance = Pressure change/ Flow
• ∆P(PIP - PEEP) can be treated as WOB
• In clinical settings, airway obstruction is one of most frequent
causes of increased WOB Decreased Airflow Decreased Minute
Ventilation Hypoventilation CO2 retention
• Prolonged high resistance High WOB Respiratory muscle
fatigue Ventilatory Failure & Oxygenation Failure
Airway Resistance & Work of Breathing
15. • Time const.= Compliance × Resistance = TV / Flow
• A pressure gradient between atmosphere and alveoli must be established to move
air into or out of the alveoli.
• Tc is the time taken for the transthoracic pressure change to be transmitted as the
volume change in the lungs, i.e. the time it takes for airway pressure and volume
changes to equilibrate b/w the proximal airway and the alveoli.
• For practical purposes, all pressure and volume delivery (inflation/ deflation) is
complete (99%) after 5 Tc.
• Inspiratory Tc << Expiratory Tc
• Patients with Decreased Compliance (Shorter Tc) ventilate with Smaller TV and
Faster Rates to minimize PIP
• In pts with increased resistance (Long Tc), a fast rate results in short Ti & Te
Inadequate Ti results in lower TV, whereas insufficient Te results in inadvertent
PEEP/ auto-PEEP/ intrinsic PEEP best ventilated with Slower rates and Larger
TV.
Time constant Tc = Cl × R = ∆V/∆P × ∆P/V
18. Condition Compliance
(L/cm H2O)
Resistance
(cmH2O/L/sec)
Time const.
(sec)
Healthy
neonate
0.005 20 0.1
HMD 0.001 20 Normal 0.02
MAS 0.003 100 0.3
Implication of CL, R, Tc
• During Mechanical Ventilation, inspiratory phase is active and high flow of air
Low Tc So short Ti is sufficient in most situations
• Ventilator expiratory phase is passive, so Tc values are essentially applicable to
expiratory time.
19. • Diseases of the lung parenchyma e.g. ARDS, HMD, Atelectasis, Pneumonia,
Pulmonary edema, Pulmonary hemorrhage FRC is reduced as terminal airways
become fluid-filled or collapsed
• The Approach to decreased FRC is to increase MAP to recruit atelectatic areas;
(usually achieved by a higher PEEP).
• Decreased compliance requires a higher pressure gradient to achieve a given TV.
• Volume-Controlled MV PIP will be higher to achieve a given TV.
• Pressure-Controlled MV Given PIP may result in a lower TV.
• May respond to higher ventilator Rates (lungs empty and fill more quickly).
• If neither PIP nor Rate is increased sufficiently Hypercarbia
DISEASES OF DECREASED COMPLIANCE
(Restrictive Diseases)
20. • Diseases that decrease the caliber of the airway lumen by edema, spasm, or
obstruction. Eg.Asthma, Bronchiolitis, Cystic fibrosis etc.
• Increased resistance Impedes gas flow, Gas Trapping Intrapulmonary shunt
and Dead space Hypoxia & Hypercarbia
• Increased resistance requires higher pressure for the gas flow to reach alveoli.
• Volume-Controlled MV Higher PIP is required to deliver given TV.
• Pressure-controlled MV TV is lower at the same PIP.
• Increased resistance Increases in Tc Necessitates Long Ti & Te
• If the ventilator Rate is too high and Ti & Te are too short Gas trapping Lung
hyperinflation, pneumothorax, barotrauma, and reduction in compliance.
DISEASES OF INCREASED RESISTANCE
(Obstructive Disease)
21. A. Oxygenation Failure: Hypoxemic respiratory failure
A.Severe hypoxemia (PaO2<40) that does not respond to supplemental O2,
SpO2 < 90% despite FiO2 > 0.6
B.Pneumonia, Pulmonary edema, Pulmonary hemorrhage, and RDS, HMD.
• Ventilation Failure: Hypercarbic respiratory failure
• Decreased minute ventilation or increased physiologic dead space alveolar
ventilation is inadequate Inability to maintain proper removal of CO2
Hyper capnia, Respiratory Acidosis
• Neuromuscular diseases
• Diseases that cause respiratory muscle fatigue due to increased workload
(Asthma, COPD and Restrictive lung disease)
Respiratory failure can be of Mixed(both oxygenation & ventilation failure)
Respiratory Failure
24. • FRC= Volume of gas in the lungs after a normal tidal expiration
• No muscles of respiration are contracting at the FRC
• Here, Tendency of lung to contract = Tendency of the chest wall to
expand (Balance point between the inward elastic recoil of the lungs
and the outward elastic recoil of the chest wall)
• During inhalation above FRC Inspiratory muscles active
• During active exhalation below FRC Expiratory muscles active
Concept of FRC: Basis of PEEP Therapy
25. • Normally alveolar end expiratory pressure equilibrates with atmospheric
pressure(i.e. zero pressure) and average pleural pressure is -5 cmH2O
• So alveolar distending pressure is 5 cmH2O (Alveolar-Pleural)
• This distending pressure is sufficient to maintain a normal end expiratory
alveolar volume to overcome the elastic recoil of alveolar wall.
• If decreased compliance Inward elastic recoil of alveoli is increased
alveolar collapse Intrapulmonary shunting.
• PEEP increases the alveolar end expiratory pressure Increases alveolar
distending pressure Re-expansion/ Recruitment of collapsed alveoli
Improves ventilation
• Thus, PEEP leads to increased V/Q ratio, improves oxygenation, decreased
work of breathing
Concept of FRC: Basis of PEEP Therapy
26. Physiologic Dead Space= Anatomic + Alveolar
1.Anatomic dead space:
• Volume of conducting airways, approx. 30% of TV
• 1 ml/lb ideal body wt
• Decrease in TV leads to relatively higher percentage of TV lost in anatomic
dead space
• E.g. Neuromuscular dis., Drug Overdose
1.Alveolar dead space:
• When ventilated alveoli are not adequately perfused
• E.g. Decreased cardiac output, Pulmonary vasoconstriction etc.
•In health, Physiologic DS= Anatomic DS
Dead space ventilation
28. • Normal respiratory cycle of a spontaneous breath:
• Subatmosheric (Negative) intrapleural pressure
• Forces by inspiratory muscles intrapleural pressure more negative(-6 to
-8cm H2O ) Sucking of air into lungs
• During Expiration, respiratory muscles relax, elastic recoil of chest
exhalation
• This is called Negative Pressure ventilation
• Negative pressure ventilators Iron lung machines
Negative Pressure ventilation
30. • PPV causes pressure changes opposite to that of
spontaneous breathing.
• During inspiration, Ventilator generates positive pressure
in the airways to drive air into lungs
• The positive pressure to set on ventilator is based on
disease status (severe HMD- more stiff lung, driving
pressure needed for circuit etc.)
Positive Pressure ventilation
33. • Increased FiO2 Increases PaO2 & thus oxygenation
• Very high FiO2 directly toxic to Retina, Lungs, Brain, Gut (free radical injury)
a) For pts with severe hypoxemia/ abnormal cardiopulmonary status: initial FiO2 is
80-100%, can be decreased to 50%
• Both FiO2 & MAP determine oxygenation
• Parameter more likely to be effective and less damaging should be used to
increase PaO2
• E.g.– if FiO2 is > 0.6-0.7, increase MAP
if FiO2 is < 0.3-0.4, decrease MAP
b) For pts with mild hypoxemia/Normal Cardiopulmonary status: Initial FiO2 may
be set 40-50%, change as per ABG
FiO2
34. • No positive pressure is safe
• PIP in part determines TV & Minute Ventilation
• Initial PIP: based on Chest movement & Breath sounds
• Normal neonatal lungs 12-14 cm H2O
• Mild to moderate lung disease 16-20
• Severe lung disease 20-25
• Increase in PIP Increases TV, Increases CO2 elimination, Decreases PaCO2,
Increases PaO2
• Inappropriately high PIP Increased risk of Air leaks & Chronic lung dis.(BPD)
• Inappropriately low PIP Lung collapse & insufficient ventilation Increased
PaCO2, Decreased PaO2, Atelectasis
PIP
35. • PEEP in part determines Lung volume during expiratory phase,
improves ventilation perfusion mismatch & prevents alveolar collapse
• A minimum physiological PEEP of 3 cmH2O should be used in most
newborns/Infants
• In HMD Initial PEEP= 4-5 cmH2O (increase upto 8)
• Increased PEEP improves MAP & oxygenation but also reduces TV
& CO2 elimination Increases PaCO2
• Inappropriately High PEEP over distended lungs, airleaks,
decreased compliance, decreased cardiac output
PEEP
37. • Ti : Te Ratio should be kept as physiological as possible = Close to 1:2
• Insufficient Ti Inadequate TV delivery, CO2 retention
• Insufficient Te Air trapping
• Inverse Ti : Te (3:1 or 2:1) used only when conventional strategy fails
• Prolonged Expiratory (1:2 or 1:3) in MAS, Asthma
• Ti : Te ratio can be changed by manipulating one or more: Flow rate/ Ti/
Ti percentage/ Respi. Rate/ Minute Volume (TV x RR)
Ti & Te
38. • A minimum gas flow as required by the machine should be used (5-
7 Lt/min.)
• Generally this parameter is not altered during the ventilation
• Very high gas flow increases Resistance, causes turbulence, air
trapping & air leaks
• Low Flow Rate (0.5-3 l/min): produces sine waveform, But may
cause hypercapnia, may not be enough to produce required PIP at
high rates (Short Ti)
• High Flow Rate (4-10 l/min): produces more square waveform,
necessary to attain high PIP at high rates, But may cause
Barotrauma & Airleaks
Gas Flow Rate
39. Sine wave:
• Smoother increase of pressure
• More physiologic
• But lower MAP is achieved for equivalent PIP
Square wave:
• Constant peak flow during entire inspiratory phase
• Higher MAP is achieved for equivalent PIP
• Longer time at peak pressure
• May open up atelectasis and improve distribution of ventilation
• High pressure if applied to normal alveoli may result in barotrauma
• Can impede venous return if reverse Ti:Te ratio is used
Wave Form
40.
41. • TV in health= 8-10 ml/kg body wt
• During Ventilation, Initial TV = 10-12 ml/kg
• Lower TV (5-7 ml/kg) can be used (permissive hypercapnia) in
ARDS/ HMD to minimize the airway pressures and risk of
barotrauma.
• But Lower TV may lead to Acute hypercapnia, increased work of
breathing, severe acidosis & collapse.
Tidal Volume
42. Goals of Assisted Ventilation
• OXYGENATION(PAO2 )
• Depends on FiO2 & MAP(Area under curve P-T graph)
• MAP=K(PIP×Ti)+(PEEP×Te)
(Ti+Te)
Oxygenation(Pao2) α Fio2
PIP
Ti
K(Gas Flow,Wave form)
43. Advantage Disadvantage
↑ Fio2 Minimizes barotrauma
Easily administered
Fails to affect V/Q matching
Direct toxicity, especially >0.6
↑ PI Critical opening pressure,
Improves V/Q matching
Barotrauma: Air leak, BPD
↑ PEEP Maintains FRC, prevents collapse
Splints obstructed airways
Regularizes respiration
Shifts to stiffer compliance Curve
Obstructs venous return
Increases expiratory work and CO2
Increases dead space
↑ TI Increases MAP without increases PI
Critical opening time
Necessitates slower rates,
Lower minute ventilation for given PI —
PEEP combination
↑ Flow Square wave — maximizes MAP Greater shear force, more barotrauma
Greater resistance at greater flows
Manipulations to Increase Oxygenation
44. 2) CO2 Elimination (PaCO2 & pH)
α MV α RR
α TV α Driving pressure (PIP-PEEP)
α Compliance of lung
Goals of Assisted Ventilation
45. Advantage Disadvantage
↑ Rate Easy to titrate
Minimizes barotrauma
Maintains same dead space/TV
May lead to inadvertent PEEP
↑ PI
Better bulk flow (improved dead space/TV)More barotrauma
Shifts to stiffer compliance curve
↓ PEEP Widens compression Pressure
Decreases dead space
Decreases expiratory load
Shifts to steeper compliance curve
Decreases MAP
Decreases oxygenation (alveolar
collapse)
Stops splinting obstructed /closed
airways
↑ Flow Permits shorter TI, longer TE More barotrauma
↑ TE
Allows longer time for passive expiration
in face of prolonged time Constant
Shortens TI
Decreases MAP
Decreases oxygenation
Manipulations to Increase Ventilation
46. Adequacy Of Alveolar Ventilation
• Oxygenation Index OI= MAP×Fio2×100
PaO2
>15 means severe repiratory distress
>40 min in patient on conventionl ventilation, 2 samples
30 min apart indication for ECMO.
• Ventilation Index VI=RR×PIP×PCO2
1000
>90 for 4hr means poor prognosis.
48. The mechanical ventilator can control 4 primary variables during
inspiration—
Pressure, Volume, Flow and Time
1.Pressure controlled ventilator ventilator controls trans
respiratory system pressure i.e. airway pressure-body surface
pressure.
•Means that pressure level that is delivered to the pt will not vary in
spite of changes in compliance or resistance.
•Further classified as PPV & NPV
•Trans respiratory pressure gradient is generated in both Causes
lung expansion
Control Variables
49. 2. Volume controlled ventilator:
• Volume delivery remains constant with changes in compliance
& resistance, while the pressure varies.
• Volume measurement and feedback signal is must
3. Flow controlled ventilator:
• Allows the pressure to vary with changes in compliance &
resistance while directly measuring and controlling flow
4. Time controlled ventilator:
• Measure and control inspiratory & expiratory time
• Allows pressure and volume to vary with changes in compliance &
resistance
50. PRESSURE VENTILATION VOLUME VENTILATION
Parameters set by
the operator
• PIP, PEEP, Rate, FIO2, Ti • TV, PEEP, Rate, FIO2, Ti
Parameters
determined by the
ventilator
• TV, Te • PIP, Te
Advantages • Higher MAP with the same PIP
• Lung protective for noncompliant lungs
• Guaranteed minute ventilation
Disadvantages • Does not accommodate for rapid changes
in pulmonary compliance
• Not optimal for patients with an
endotracheal tube with large leaks
• Minute ventilation not guaranteed • PIP May reach dangerous level if
compliance is worsening
PRESSURE V/S VOLUME VENTILATION
51.
52. • It combines two control variables (pressure & volume),
that are regulated by independent feedback loops so that
delivered breath switches b/w pressure control and
volume control.
• Patient receives mandatory breaths that are Volume
Targeted, Pressure Limited, and Time cycled.
• PRVC (pressure regulated volume control),
• VAPS(volume assured pressure support),
• VG(volume guarantied) is also work on dual mode.
Dual-Control Mode
53. • A ventilator supported breath is divided into 4 distinct phases: 1)
Change from expiration to inspiration 2) Inspiration 3) Change
from inspiration to expiration 4) Expiration.
• When 1 of the 4 variables (Pressure, Volume Flow & Time) is
examined during a particular phase, it is termed as “Phase
variable”
• Trigger Variable
• Limit Variable
• Cycle Variable
Phase variables
54. • What determines the start of inspiration?
1. Time triggered: Breath is initiated and delivered when a preset time
interval has elapsed.
• The rate control on ventilator is a time triggering mechanism. At given time
trigger interval, the ventilator automatically delivers one mechanical
breath without regard to patient’s effort or requirement
1. Pressure triggered: Beginning of spontaneous inspiratory effort by pt
Drop in airway pressure Sensed by ventilator as a signal to initiate
and deliver a breath.
• The amount of negative pressure, a pt must generate to trigger the
ventilator is Sensitivity Level (-1 to -5 cm H2O)
1. Flow triggered: More sensitive & responsive to pt’s effort
1. Continuous flow is given(delivered=returned)pt effort part of flow
goes to pt returned flow< delivered flow sensed by ventilator to
initiate breath
Trigger Variable
55. • What is set to its upper limit during inspiration?
• If one variable (volume/pressure/flow) is not allowed to rise above a
preset value during the inspiratory time, is termed as Limit Variable
• Inspiration does not end when this variable reaches its preset value,
breath delivery continues, but the variable is held at the fixed preset
value(max.)
• Pressure limited/ Volume limited/ Flow limited
Limit Variable
56. • What ends inspiration?
• This variable is measured and used as feedback signal by
ventilator to end inspiratory flow delivery, which then
allows exhalation to begin
• Most newer ventilators are Flow controlled, Time cycled
Cycle Variable
59. Operating Modes
11) Adaptive Support Ventilation (ASV)
12) Proportional Assist Ventilation (PAV)
13) Volume Assured Pressure Support (VAPS)
14) Pressure Regulated Volume Control (PRVC)
15) Volume Ventilation Plus (VV+)
16) Pressure Control Ventilation (PCV)
17) Airway Pressure Release Ventilation (APRV)
18) Inverse Ratio Ventilation (IRV)
19) Automatic Tube Compensation (ATC)
11) Adaptive Support Ventilation (ASV)
12) Proportional Assist Ventilation (PAV)
13) Volume Assured Pressure Support (VAPS)
14) Pressure Regulated Volume Control (PRVC)
15) Volume Ventilation Plus (VV+)
16) Pressure Control Ventilation (PCV)
17) Airway Pressure Release Ventilation (APRV)
18) Inverse Ratio Ventilation (IRV)
19) Automatic Tube Compensation (ATC)
60. Modes of Ventilation
• Basically there are three breath delivery techniques used with
invasive positive pressure ventilation
• CMV – controlled mode ventilation
• SIMV – synchronized
• Spontaneous modes
61. • Three basic means of providing support for continuous
spontaneous breathing during mechanical ventilation
• Spontaneous breathing
• CPAP
• Bi-PAP
• PSV – Pressure Support Ventilation
Spontaneous Modes
62. • Patients can breathe spontaneously through a ventilator circuit;
sometimes called T-Piece Method because it mimics having the
patient ET tube connected to a Briggs adapter (T-piece)
• Role of ventilator in this mode is to provide:
1. Inspiratory flow in a timely manner
2. Adequate flow to meet pt’s inspiratory demand (TV & inspiratory
flow)
3. Provide adjunctive mode as PEEP to complement pt’s spontaneous
breath
• Disadvantage-May increase patient’s WOB with older ventilators
Spontaneous Modes
63. • PEEP increases end-expiratory/ baseline airway pressure to more
than atmospheric pressure.
• Not a “Stand-alone” Mode, rather it is applied in conjugation with
other modes.
• E.g. with CPAP, AC, SIMV
• Indications for PEEP:
1. Decreased FRC & Lung compliance
2. Refractory Hypoxemia, Intrapulmonary Shunting
PEEP (Positive End Expiratory Pressure)
64. Modes of Ventilation-CPAP
• Ventilators can provide CPAP for spontaneously
breathing patients
o Positive intrapulmonary pressure (PEEP) is applied
artificially to the airways of a spontaneously breathing baby,
throughout the respiratory cycle, so that distending
pressure is created in the alveoli
o Distinct from IPPV or IMV in which breathing is taken over
by ventilator completely and increase in pressure occurs
during both inspiratory as well as expiratory phases
separately
o CPAP ≈ Half Filled Air Balloon
o Advantages-Ventilator can monitor the patient’s breathing
and activate an alarm if something undesirable occurs
65. • Independent positive airway pressures to both inspiration and expiration (IPAP
& EPAP)
• IPAP provides positive pressure breaths and improves ventilation & hypoxemia
d/t hypoventilation.
• EPAP is in essence CPAP which increases FRC, improves alveolar recruitment
Improves PaO2
• Used in cases of Advanced COPD, Chronic ventilatory failure, Neuromuscular
dis., Restrictive chest wall dis.
• Bi-PAP device can be used as CPAP
• Initiate with IPAP=8, EPAP=4, then gradual increments of 2cmH2O in both
Bi-PAP: Bi-level Positive Airway Pressure
66. • PSV applies a preset pressure plateau to the airways for the duration of
a spontaneous breath.
• A Pressure supported breath is:
Patient Triggered: All ventilator breaths are triggered by patient
Pressure Limited: Maximum pressure level can not exceed preset pressure
support level, TV varies with inspiratory flow demand.
Flow Cycled: When pt’s inspiratory flow demand decreases to a preset minimal
value, inspiration stops and expiration starts.
• PSV can be used with spontaneous breathing in any ventilator mode
(usually SIMV) as a PRESSURE BOOST
• Patient has control over Rate & Ti both.
• Adv.: Increases spontaneous TV, Decreases spontaneous RR, Decreases
Work of breathing.
Pressure Support Ventilation-
68. PSV during SIMV
• Spontaneous breaths during SIMV can be supported with PSV (reduces
the WOB)
PCV – SIMV with PSV
10 cm H2O
35 cm H2O
69. • Ventilator delivers preset TV/Pressure at a Time triggered rate
• Ventilator controls both the pt’s TV & RR, So ventilator controls the pt’s Minute Volume
• Pt can not change RR or breath spontaneously, so only used when pt is on sedation/
respiratory depressants/ NM blockers.
• Indications of CMV:
1. Severely distressed pt, vigorously struggling Rapid inspiratory efforts Asynchrony/
Fighting in the initial stages CMV
2. Tetanus/ status epilepticus Interrupts ventilation delivery
3. Crushed chest injuries d/t Paradoxical chest movements
Controlled Mandatory Ventilation (CMV)
70. • Every breath delivers a preset mechanical TV (Volume Cycled) either assisted or controlled
• If Pressure/Flow triggered by Pt’s spontaneous effort = ASSIST
• If Time triggered by ventilator = CONTROL (Safety Net)
• Adv.: 1) Work of breathing is handled by ventilator,
• 2) Pt himself can control RR & therefore minute ventilation to normalize PaCO2
• Disadv.:Pt with inappropriately high respiratory drive* High assist rate despite low PaCO2
Hypocapnia & Respiratory alkalosis
• Indi.= Mostly used for a pt. with stable respiratory drive to provide full ventilatory support when
pt. first placed on ventilator.
Assist Control (ACMV)
71. • Ventilator delivers control/mandatory breaths at a set time interval independent of pt’s
spontaneous respiratory rate.
• Allows the pt. to breath spontaneously at any TV in b/w control breaths
• Was the first widely used mode that allowed partial ventilatory support.
• Disadv.: Ventilator Asynchrony, Breath Staking.
• Not used nowadays
• Gave birth to SIMV
Intermittent Mandatory Ventilation (IMV)
72. • Mandatory breaths are synchronized with pt’s spontaneous breathing efforts to avoid asynchrony.
• Ventilator delivers a mandatory breath at or near the time of a spontaneous breath.
• The time interval (just prior to time triggered ventilator breath) in which ventilator is responsive to
pt’s spontaneous breath is= “Synchronization Window”, usual window is 0.5 sec*
• SIMV permits the pt. to breath spontaneously to any tidal volume the pt’ desires.
• The gas source for spont. breathing is supplied by “demand valve” always pt. triggered
• Spontaneous breaths taken by the pt. are TRULY SPONTANEOUS Rate & TV are dependent on pt,
humidified gas at selected FiO2 is given by ventilator.
Synchronized IMV (SIMV)
73.
74. • SIMV allows patients with an intact respiratory drive to exercise inspiratory muscles between
assisted breaths, making it useful for both supporting and weaning intubated patients
• Indication: To provide partial ventilatory support.
• When a pt placed on ventilator Full ventilatory support is appropriate for initial 24 hrs Then
Trial of partial ventilatory support on SIMV (pt is actively involved in providing part of minute
volume) Gradually decrease the mandatory rate as tolerated by the pt.
• Adv:
1. Maintains respiratory muscle strength/ avoids muscle atrophy
2. Reduces V/Q mismatch
3. Decreases MAP
4. FACILITATES WEANING ( Using small decrements* in mandatory rate)
Synchronized IMV (SIMV)
75. • neonatal ventilation has been accomplished using traditional time-cycled
pressure-limited ventilation (TCPL).
• In this mode of ventilation, a peak inspiratory pressure is set by the operator,
and during inspiration gas flow is delivere to achieve that set pressure, hence
the term pressure-limited (PL) ventilation.
• The volume of gas delivered to the patient in this mode however varies
depending on pulmonary mechanics such as compliance or stiffness of the
lungs.
• At low compliance (‘stiff lungs’) such as occurs early in the course of
respiratory distress syndrome (RDS), a given pressure generates lower tidal
volume as compared to later in the course of the disease when the lungs are
more compliant (‘less stiff’) when the same set pressure will lead to delivery
of larger tidal volumes.
• This is important clinically as with improvement in compliance such as after
exogenous surfactant therapy, the ventilator pressure has to be weaned by
the operator to prevent alveolar over distension resulting from excessive tidal
volume delivery.
TCPL( Time cycled pressure limit) ventilation
76.
77. • An additional safety function of SIMV mode, that provides a
predetermined minute ventilation when pt’s spontaneous
breathing effort becomes inadequate.
• E.g. Apnea mandatory rate increased automatically to
compensate for decrease in minute ventilation caused by apnea.
• Prevents hypercapnea by automatically ensuring a minimum preset
minute ventilation.
Mandatory Minute Ventilation (MMV)
78. • PRVC provides volume support with the lowest possible PIP by
changing the Peak Flow & Ti
• PRVC is a Dual control mode: Both TV & PIP can be controlled at same
time
• Airflow resistance = (PIP-PEEP) ÷ Flow
• At a constant flow & PEEP, increased airflow resistance requires higher
PIP. PRVC lowers the flow to reduce PIP.
• At a constant PIP, increased airflow resistance lowers flow. PRVC
prolongs Ti to deliver the target TV.
• Works with CMV or SIMV (in viasys ventilator) mode
• Volume cycled, Time / Pt triggered
Pressure Regulated Volume Control (PRVC)
79. • VV+ is an option that combines two different dual mode volume
targeted breath types: VC+ and VS
a) VOLUME CONTROL PLUS (VC+):
• VC+ is used to deliver mandatory breaths during AC and SIMV modes
• Intended to provide a higher level of synchrony than standard volume
control ventilation.
• Target TV & Ti is set Ventilator delivers a single test breath using
standard volume & flow to determine compliance Then Target
pressures for subsequent breaths are adjusted accordingly to
compensate for any TV differences
Volume Ventilation Plus (VV+)
80. b) VOLUME SUPPORT (VS):
• Target TV is set and ventilator uses variable pressure support levels to
provide the target TV.
• Only target TV is set (not the Ti or Mandatory Rate) ventilator delivers
a single spontaneous pressure support breath and then uses variable
pressure support levels to provide target TV.
• Mandatory Rate and minute ventilation is determined by triggering
effort of the patient.
• Used during “Awakening from anesthesia”
Volume Ventilation Plus (VV+)
81. • Like half Filled air balloon
• Pt. is allowed to breath spontaneously at an elevated baseline (i.e. CPAP). This elevated baseline
is released periodically to facilitate expiration.
• Newer mode, indicated in patients with lower compliance e.g. ARDS in which conventional
volume controlled ventilation requires very high PIP
• APRV can provide effective partial ventilatory support with a lower PIP in these pts.
Airway Pressure Release Ventilation (APRV)
82. • Delivers small Tidal volumes at very high rates, reduces the risk of
barotrauma.
• Limited to the situations in which conventional ventilation has failed
• Categorized by rate and the method used to deliver the TV
High Frequency Ventilation (HFV)
Type of HFV Rate per min.
HFPPV (HF Positive Pressure Ventilation) 60 - 150
HFJV (HF Jet Ventilation) 240 - 660
HFOV (HF Oscillatory Ventilation) 480 - 1800
83.
84. Use pressure control rather than volume control
SIMV mode can be used for any condition
Apneic – SIMV mode with normal respiratory rate
Spontaneous breathing (not adequate) -
Set a minimum RR of 10- 20 /min
Tachypneic child fighting with ventilator -
Set higher rate & adequately sedate the child
In addition to SIMV, every spontaneous breath can be pressure
supported provided RR is not too high
Which mode for which condition ?
86. Retraction moderate or severe
RR > 70/min
Cyanosis even after oxygenation
Intractable apneic spell
Impending or existing shock
PaO2 < 50, PCaO2 > 60, PH < 7.25
Indication for mechanical ventilation-
Neonate
87. Setting Infant with
NORMAL LUNG
FiO2 0.5 or to target SPO2 85 – 95 %
Respiratory rate 30-40 / minute to maintain normal PaCO2
(higher rate is requried if cerebral odema & Raised ICT)
PIP 10 - 12 cm H2O , just enough to produce minimal chest
rise ( VT 3-5ml/kg )
PEEP 4 - 5 cm H2O ( to achieve normal FRC : 7-9 post rib)
Ti 0.3-0.4 sec
Flow rate 4-6 l/min
Suggested initial ventilator setting in
Birth asphyxia & apnea (Normal lung)
Target blood gas Ph 7.3 to 7.4, PaCO2 35 to 45 , PaO2 60 - 90
88. Setting Infant with RDS
FiO2 0.5 or to target SPO2 85 – 95 %
Respiratory rate 40-60 / minute(higher)
PIP 12-20 cm H2O(dependa upon severity) , just enough
to produce minimal chest rise ( VT 3-5ml/kg )
PEEP 4 - 7 cm H2O ( to achieve normal FRC : 7-9 post rib)
Ti 0.2 - 0.3 sec
Flow rate 6-8 l/min
Suggested initial ventilator setting in
Hyaline membrane disease / RDS
Target blood gas Ph 7.25 to 7.35, PaCO2 45 to 55 , PaO2 50 - 70
89. Setting Infant with MAS
FiO2 FiO2 to target SPO2 90 – 95 %
Respiratory rate 40-60 / minute
PIP 12-16 cm of H2O, just enough to produce minimal
chest rise ( VT 3-5ml/kg )
PEEP Low to moderate PEEP (0 - 3 cm H2O)
Ti 0.4- 0.5 sec (Te 0.5 -0.7 sec, I:E = 1:3 – 1:4)
Flow rate 6-8 l/min
Suggested initial ventilator setting in
MAS
Target blood gas Ph 7.25 to 7.35, PaCO2 45 to 55 , PaO2 50 - 70
90. Setting Infant with PPHN
FiO2 High FiO2 to target SPO2 90 – 95 %
Respiratory rate High rate 50-70 / minute
PIP Optimal PiP , just enough to produce minimal chest
rise ( VT 3-5ml/kg )
PEEP 4 - 6 cm H2O
Ti 0.3- 0.4 sec
Flow rate 6-8 l/min
Suggested initial ventilator setting in
PPHN
Target blood gas Ph 7.3 to 7.4, PaCO2 40 to 45 , PaO2 80 - 100
91. Observe infant for cyanosis , absence of retraction, chest wall
movement.
If ventilation is inadequate increase PIP by 1 cm H2O every few
breath until air entry & chest rise adequate.
If oxygenation is inadequate increase FiO2 by 0.05 every minute
Until cyanosis abolish or SPO2 = 90-95 %.
Initial pressure that result in adequate chest expansion & result in
tidal volume 3-5 ml/kg should be taken as initial PIP setting.
PEEP should not exceed 8 cm H2O in most situation.
Initiation
92. CLINICAL PARAMETER
Pink colour
Adequate chest expansion
Absence of retraction
Adequate air entry
Prompt capillary filling within 2 second
Normal blood pressure
PULSE OXYMETERY
Oxygen saturation 90-95 %
BLOOD GASES
PaO2 50-80 mm Hg
PaCO2 40-50 mm Hg (in chronic cases up to 60 mm Hg)
PH 7.35-7.45
Adequacy of ventilation
93. Blood gas
abnormamal
ity
Corrective measure
FiO2 Rate PIP PEEP Ti
Hypercapnea
PaCO2 > 50
mm Hg
Hypocapnea
PaCO2 < 35
mm Hg
Hyperoxia
PaO2 > 100
mm Hg
Hypoxemia
PaO2 < 50
Change in ventilatory parameters
94. •Change should be made in short steps
•PIP &PEEP should be altered only 1 cm H2O at time
•Rate by 2 breath/min, FiO2 – 5%
•Blood gas estimation should be performed 20-30 min after every change
•To minimize adverse effect of one parameter simultaneously step up or step
down various setting
FiO2 - 0.95, PIP-18 cm, PEEP- 4 cm H2O
Peep requirement go in consonance with FiO2
Changing ventilator setting
FiO2 PEEP
0.3 3
0.4 4
0.5 5
>o.8 8
95. •HMD weaning attempted on 3rd
or 4th
day especially at time
when maximum diuresis occurs.
•HMD it is important to reduce setting when compliance
improves if not changed barotrauma will result.
•Uncomplicated MAS or pneumonia can be weaned much
earliar.
•Iv aminophylline is started 24 hours prior to expected time of
extubation .
•Dexamethasone 0.15 mk/kg IV for post extubation stridor.
•Infant is attached to CPAP mode before extubation.
Weaning from ventilator
96. Reduce PIP to 25 cm H2O
Alternately reduce PIP& FiO2
Reach PIP 20 cm, FiO2 0.6
Pulse oxymetry and
PaO2
Clinical and PCaO2
PaCO2
FiO2 and PEEP
PIP
Rate and Ti
Weaning
99. In shock use higher FiO2 up to 1.o initially
In encephalopathy higher RR to cause hypocarbia (30-35 mm Hg)
Setting - Normal lung
PiP 15-20 cm H2O
Vt 6-8 ml/kg
PEEP 3-4 cm H2O
Rate 40/min (infant)
20-30 /min (older children)
I:E ratio 1:2
100. Respiratory rate higher than normal
Higher PIP
Higher PEEP
Pneumonia
Pneumonia Normal lung
PiP 20-25 cm H2O 15-20 cm H2O
Vt 6-8 ml/kg 6-8 ml/kg
PEEP 4-5 cm H2O 3-4 cm H2O
Rate 40-50/min (infant)
30-40 /min (older
children)
40/min (infant)
20-30 /min (older
children)
I:E ratio 1:2 1:2
101. PEEP is kept low to prevent air trapping
Lower RR and prolonged Te to ensure air expulsion
Maintain oxygenation and accept hypercarbia up to 60 cm H2O
Asthma / Bronchiolitis
asthma Pneumonia
PiP <20-25 cm H2O 20-25 cm H2O
Vt 6-8 ml/kg 6-8 ml/kg
PEEP 3-4 cm H2O 4-5 cm H2O
Rate 30-40min (infant)
20-30 /min (older
children)
40-50/min (infant)
30-40 /min (older children)
I:E ratio 1:3 to 1:4 1:2
102. High degree of collapsibility & very low compliance .
Don’t exceed PIP >35 cm H2O.
FiO2 preferably kept below < o.6 .
Hypercapnea to degree is acceptable.
ARDS
PiP < 35 cm H2O
Vt 4-6 ml/kg
PEEP 5-10 cm H2O
Rate 40/min (infant)
20-30 /min (older children)
I:E ratio < 1:2 to inverse ratio
103. Measure to reduce barotrauma -
•Permissive hypercapnea
Higher PaCO2 is acceptable as long as PH > 7.25.
•Permissive hypoxemia
PaO2 55to 60 mm Hg SaO2 of 88 – 90 % is acceptable for limiting PEEP & FiO2
Inverse ratio ventilation-
•Ratio of 2:1 and 4:1
•Increase in mPaw during IRV help to reduce alveolar
•collapse , shunting, V/Q mismatch
•To achieve same ventilation you need lesser PIP & PEEP
•Auto PEEP – also reduce shunting & improve oxygenation
Continue..
104. Don’t just increase FIO2 , increase PIP & PEEP
Saturation worsening with PEEP, suspect low cardiac output
or air leak
Don’t forget other measure to improve oxygenation
Manage shock
Normal hemoglobin
Deepen sedation
Normothermia
Hypoxia
105. In asthma increase expiration (Te)
Decrease PEEP
Decrease Co2 production – sedation, cooling body
Et tube blockade / malpositioned
High PaCO2
109. DOPE
D = Displacement O = Obstruction
P = Pneumothorax E = Equipment failure
Check tube placement – is chest rising ? breath sound equal ?
When in doubt take ET tube out & start manual ventilation
Check ABG & Chest x ray for pneumothorax & worsoning lung
pathology
Examine ventilator & circuit
Examine for shock & sepsis
If no other reason for hypoxemia :
Increase sedation /muscle relaxation
Patient fighting & desaturating
110. 1. VENTILATOR-ASSOCIATED PNEUMONIA (VAP)
2. HYPOTENSION (d/t elevated intrathoracic pressures with decreased VR)
3. GI Effects: Stress ulceration, Mild to moderate cholestasis
4. VOLUTRAUMA = Damage caused by over distention; sometimes called high-
volume or high end-inspiratory volume injury
5. ATELECTOTRAUMA = Lung injury associated with repeated recruitment and
collapse, theoretically prevented by using adequate PEEP, sometimes called
low-volume or low end-expiratory volume injury
6. BIOTRAUMA = Pulmonary and systemic inflammation caused by the release
of mediators from lungs subjected to injurious mechanical ventilation
7. OXYGEN TOXIC EFFECTS = Damage caused by a high concentration of inspired
oxygen
8. BAROTRAUMA = High-pressure–induced lung damage, clinically manifest by
interstitial emphysema, pneumo mediastinum, subcutaneous emphysema, or
pneumothorax.
Complications of Mechanical Ventilation
111. No clinical need for increased support – 24 hrs
Spontaneous respiration
FiO2 requirement < 0.5
Improving breath sound, decreased secretion
Improving chest x ray
Hemodynamically stable
LGB – muscle power & cough, Gag reflex
Encephalitis – improvement in GCS scale
Airway edema – air leak at below 20 cm H2O PiP
Weaning a child begins with improvement in
clinical condition
112. How to wean-
•Decrease FiO2 by 5% to keep SPO2 > 94 % (o.6).
•Decrease PEEP by 1-2 cm to 4-5 cm H20.
•Alternate FiO2 & PEEP after that.
•Decrease SiMV rate by 3-4 breath/min to reach SiMV rate 5 .
•Decrease PiP & pressure support ( 2 cm each time by titrating with Vt – 5 ml/kg ).
•Ventilator rate & PiP can be changed alternatively.
•ABG is true guide what you have done.
When to stop further weaning-
•SPO2 falls < 94% & require to increase FiO2.
•Spontaneous respiration is fast & distress.
•Agitation or lethargic.
•Hypercarbia in blood gases.
•e.g. simv rate reduced from 20 to 15/min but patient spontaneous rate increased
from 25 to 50/min.
Continue..
113. Extubation procedure
•Keep NBM & adequate suctioning
•Keep O2 source ready
•Nebulization with beta stimulant or adrenaline
•Dexamethasone 0.15 mk/kg IV for post
extubation stridor
•CPAP may be helpful in preventing reintubation
•ABG after 20 min of extubation
•Post extubation chest x ray - if clinical
deterioration
When to extubate-
•SIMV respiratory rate of 5/min.
•pressure support of 5-10 cm above PEEP.
•PEEP - 5 cm H2O
•FiO2 < 0.3 with SPO2 > 94 %
•Good breath sound, minimal secretion
•Good airway reflexes
•Air leak around tube
•Awake patient
•Adequate muscle tone
•Normal electrolyte
