2. Introduction
• Mechanical ventilation is an invasive life support procedure
with many effects on the cardiopulmonary system.
• The goal is to optimize both gas exchange and clinical status at
minimum fractional concentration of inspired oxygen(Fi02)
and ventilator pressure/tidal volume.
3. GOALS
• To maintain sufficient oxygenation and ventilation to ensure
tissue viability until the disease process has resolved .
• Pao2, Paco2, and pH levels are maintained in ranges that
provide a safe environment for the patient while protecting
the lungs from damage due to oxygen toxicity, pressure
(barotrauma), tidal volume overdistention (volutrauma),
atelectotrauma,
4. Indications of mechanical ventilation
• Preterm on CPAP
– If retractions , grunting, recurrent apnea on CPAP persists.
– SpO2<85% or
– PaO2<50mmHg with FiO2<60% and PaCO2>60mmHg
– PEEP>7cmH2O
– To administer prophylactic or early rescue surfactant in
preterm infants
Reversal of hypoxemia:
• Hypoxemic respiratory failure is characterized by failure of
lungs to maintain oxygenation.
• Reversal of acute respiratory acidosis(Paco2>50-55mmHg with
Ph<7.25).
• Central apnea(absence of respiratory efforts).
5. • Failure to establish adequate spontaneous respiration despite
positive pressure ventilation by bag and mask at birth.
• Neonates with congenital diaphragmatic hernia.
Others(short term indications)
• To relieve respiratory distress.
• General Anaesthesia: during surgeries.
• To secure an airway: in patients with depressed sensorium,
head injury.
• To decrease systemic or myocardial oxygen consumption. eg.
septic and cardiogenic shock.
• To stabilize the chest wall in children with flail chest.
6. Basics of mechanical ventilation
• A pressure gradient is required for air to move from one place
to another.
• During natural spontaneous ventilation, inspiration results
from generation of negative intra-pleural pressure from
contraction of the diaphragm and inter-costal muscles,
drawing air from the atmosphere across the airways into the
alveoli.
• During mechanical ventilation, inspiration results from
positive pressure created by compressed gases through the
ventilator, which pushes air across the airways into alveoli.
• In both spontaneous and mechanical ventilation, exhalation
results from alveolar pressure generated by the elastic recoil
of the lung and the chest wall.
7. • Pressure necessary to move a given amount of air into the
lung is determined by two factors:
• Lung and chest wall compliance and airway resistance.
• Resistance:
The air flowing into the lungs has to overcome the airway
resistance and the elastic and frictional resistance of the lungs
and the chest wall.
• Compliance represents a volume change per unit change in
pressure.
• Static compliance- is measured when there is no air flow.
• Reflects the elastic properties of the lung and the chest wall
• Dynamic compliance is measured when air flow is present
• Reflects the airway resistance (non elastic resistance) .
8. • Time constant
The rate of filling of an individual lung unit is referred to as its
time constant , it is a product of the resistance and
compliance of a particular lung unit.
• Mechanical ventilators are designed to assist , the work of the
respiratory muscles and thorax to maintain the gas exchange
function of the lungs.
• We shall briefly discuss the set up of a positive pressure
ventilator.
9. • Power input:
There can be two different ways of running a ventilator
electrical powered(uses 120 Volts AC/12Volts DC) or
pneumatic.
• The pneumatic circuit:
compressed air or oxygen is delivered to the ventilator at 50
psi pressure , in the mixing chamber , the pressure is reduced
and the gases are blended to get desired Fi02.
• Microprocessor controls the inspiratory and the expiratory
valves, monitors the pressure, flow and volume of delivered
gases and displays the alarm.
10. Classification of Ventilators
A Ventilator can be classified by describing the following
variables
• Control variable
a. Time – inspiratory and expiratory times.
b. Pressure- controls the airway pressure.
c. Volume-delivers a constant tidal volume.
d. Flow-have a constant volume waveform
• Phase variables-
Each ventilator-controlled respiratory cycle can be divided
into four phases.
a. Trigger variable
It is used to initiate inspiration.
when the trigger is initiated by the patient ,the ventilator tries
to synchronize the breath with the patients inspiratory effort.
b. Limit variable-
The limiting variable can be pressure, flow or volume.
11. c. Cycle variable:
This variable is used to terminate the inspiration.
d. Baseline variable:
This variable is controlled during the expiratory phase and is
the PEEP setting.
• Conditional variables:
• Conditional variables are those that are examined by the
ventilators control logic and invoke an action if a threshold is
met .
Examples include the synchronization of mandatory and
spontaneous breaths and delivery of sigh breaths.
• Spontaneous breaths:
• One for which inspiration Is both started(triggered)and
stopped(cycled)by the patient.
• Mandatory breaths:
• If inspiration is triggered or cycled by the machine,the breath
is classified as mandatory.
13. Modes of mechanical ventilation
• Four
( Two modes usually used in neonatology)
• Mandatory or controlled ventilation
It is also called as continuous mandatory ventilation(CMV).
• Mandatory breaths are controlled entirely by the machine i.e
all breaths are triggered ,limited and cycled by the ventilator.
• The clinician sets a minimum rate per minute, the patient can
trigger the ventilator but all the delivered breaths are
controlled by the ventilator.
• Modern microprocessor ventilators have the ability to sense
the patients effort and to synchronize the ventilators breath
with the patients initiated breath.
14. • SIMV(synchronized intermittent mandatory ventilation):
A set number of mandatory breaths per minute
are synchronized with the patient initiated breaths. SIMV can
be volume or pressure controlled.
• Assist /control ventilation:
In this mode all spontaneous breaths that exceed
the trigger sensitivity result in delivery of a mechanical breath
synchronous to the patients inspiratory effort.
If a patient fails to breath or cannot trigger the ventilator, a
control breath will be provided at the desired interval.
• Continuous spontaneous ventilation:
Every breath is generated by the patient, the patient
determines the rate , inspiratory and expiratory times, the
breaths are triggered and cycled by the patient but limited by
the ventilator.
15. • Pressure support ventilation
It is a spontaneous ventillatory mode in which an inspiratory
pressure boost is provided to overcome the imposed work of
breathing or to provide additional support to a mechanically
ventillated patient.
• It is a time limited mode that supports each spontaneous
breath.
• The patient has control over the rate and the inspitatory
time and the clinician has control over the inspiratory
pressure and the time limit.
16. Ventilatory parameters
• Peak inspiratory pressure(PIP):
This is the highest pressure that occurs during the inspiratory
phase of the cycle , usually seen at or near the end of
inspiration.
• Higher PIP indicates increased airway resistance as in
bronchospasm or decreased lung compliance.
• PIP affects VT and minute ventilation and hence Co2 removal
• Higher PIP also increases MAP and improves oxygenation.
• S/E: excessive PIP may cause barotrauma.
17. • PEEP( Positive End Expiratory Pressure).
• Positive airway pressure at the end of expiration
• PEEP prevents the closure of the alveoli during expiration.
• PEEP increases the FRC , improves V/Q matching and
oxygenation.
• It also increases the MAP.
• S/E
• Excessive PEEP can lead to over distension of lungs , gas
trapping and barotrauma.
• It impedes venous return , decreases cardiac output,
decreases cerebral perfusion.
18. • Tidal volume
• In volume controlled ventilator tidal volume is set instead of
PIP.
• Regulates minute ventilation and therefore the co2 removal.
• S/E :May lead to volutrauma.
• Frequency (rate)
• No. of set breaths per minute
• Increasing the rate helps in co2 elimination
• S/E: use of high rates can compromise inspiratory and
expiratory times.
• Inspiratory time & expiratory time(I:E ratio): Normally it is
1:2,increase the I increases the MAP
• expiratory time constant is slightly longer because airway
resistance is higher during expiration.
19. • Fi02:
• It influences alveolar oxygen tension and increase Pa02.
• High Fi02 can cause oxygen toxicity.
• Flow
• A minimum flow rate needed is 2.5-3 times the minimum
volume.
• The operating range in neonatal ventilation is 4-10 l/min
• Flow pattern is square wave in volume controlled ventilation
and descending ramp in pressure controlled ventilation.
• S/E:
• Inadequate flow may contribute to air hunger , asynchrony
and increased work of breathing , whereas excessive
breathing can contribute to turbulence , inefficient gas
exchange and inadvertent PEEP.
20.
21. Modalities of ventilators
Parameter Pressure controlled Volume controlled
Tidal volume Variable(lung mechanics) constant
PIP constant variable
Peak alveolar pr constant variable
Flow pattern decelerating preset
Peak flow variable constant
common
Ti preset preset
Minimum rate preset preset
modes IMV,SIMV,A/C IMV,SIMV,A/C
Advantages Less risk of barotrauma
,effective in treating atelactatic
lungs
Less risk of volutrauma,
autoweaning of Pressure as
compliance
Disadvantages Risk of volutrauma if PIP is not
decreased when compliance
improves
Risk of barotrauma, fixed
insp. Flow lead to increased
work of breathing.
22. Ventilator variables
Pressure controlled
ventilation
Volume controlled
ventilation
Variables set 1.PIP
2.Rate
3.inspiratory time or I:E
4.PEEP
5.Trigger sensitivity.
1.Tidal volume
2.Rate
3.Inspiratory time(controls
flow rate)
4.PEEP
5.Trigger sensitivity.
23. How to adjust ventilatory settings?
• During the acute stage of disease , ventilatory settings are
always in a dynamic state and require frequent alterations.
• Judicious clinical monitoring along with pulse oximetry and
periodic blood gas analyses are crucial for the success of
ventilatory therapy.
• Clinical parameters
• Adequate chest expansion
• Adequate air entry.
• Absence of retractions
• Pink color
• Prompt CFT(within 2-3secs)
• Normal BP.
24. • Pulse oximetry: oxygen saturation 90-95% in term babies and
children
• Blood gases
• pa02 50-80 mmHg
• paCo2 40-50 mmHg
• pH 7.35-7.45
• The changes in the ventilator settings must be made in short
steps
• PIP and PEEP should be altered only by 1.0 cm H2O at a time ,
rate 2breaths/min
• FiO2 in steps of 0.05(5%) and Ti in installments of 0.05
seconds
• ABG should be done after 20-30 minutes of each change.
25. Blood gas abnormality and changes in the
ventilator settings to correct them
Blood gas abnormality Corrective measures
Fio2 /rate/PIP/PEEP/TI
Comments
Hypercapnia
(paCo2>50mmHg)
Can also increase Te
Hypocapnia
(paCo2<35mmHg)
Hyperoxia
(paO2>100mmHg)
Hypoxia
(paCo2<50mmHg)
If chest excursions are
adequate , increase FiO2.
Total ventilatory failure.
(PaCo2 too high and PaO2
too low)
depends upon the cause
Check any endotracheal
blockage , air leak and
ventilator malfunction.
26. • To change PaCO2 ONLY, change rate
– To increase PaCO2 only, decrease rate
– To decrease PaCO2 only, increase rate
• To Change PaO2 ONLY, change FIO2, PEEP, or IT
– FIO2 is changed in 1- 5 % increments
– PEEP is changed in 1 – 2 cmH2O increments
• To change both PaCO2 and PaO2 at the same time, but in
opposite directions, change PIP
– Increase PIP, PaO2 increases, PaCO2 decreases
– Decrease PIP, PaO2 decreases, PaCO2 increases
27. Monitoring the ventilated patient
• Babies requiring mechanical ventilation require close
monitoring to optimize the respiratory support and limit the
potential complications of ventilator induced lung injury,
oxygen toxicity , air leaks and nosocomial infections.
• Physical examination
• Respiratory rate
• Evidence of respiratory distress
• Auscultation for equal air entry.
• Ventilator patient synchrony should be observed.
• Rapid shallow breathing and the presence of subcostal or
intercostal retractions in ventillated babies may suggest air
hunger or increased work of breathing
• CVS parameters include skin color ,HR , perfusion,BP & urine
output.
28. • Monitoring oxygenation
• ABG analysis is the gold standard for monitoring the adequacy
of gas exchange
• SaO2 targets of 85-93% is the most appropriate.
• In term and near term infants and older children who are
mechanically ventilated it is acceptable to target SaO2
between 92-95 % and in children with cyanotic CHD SaO2
between 70-75% are acceptable if tissue oxygenation is good.
• Ventilation
• PaCo2 determined from an ABG is a reliable measure of
ventilation
• A free flowing capillary sample is an acceptable alternative
• Capnography and trans -cutaneous CO2 detectors provide non
invasive alternatives to monitor ventilation.
29. • Chest radiograph:
• The findings to look for:
• Position of the ET, central lines and umbilical catheters.
• Optimal positioning for ETT is approximately 1-1.5 cm above
the carina.
• Displacement of the tube into the oesophagus is indicated by
a low ETT position.
• Poor aeration of the lungs and gaseous distension of the GI
tract
• Look for the atelectasis, flattening of the diaphragm and lung
expansion reaching the tenth rib suggests over expansion and
increased risk of pulmonary air leaks and lung injury.
30. Monitoring pulmonary graphics
• To assess patient ventilator interaction, the basic parameters
that are measured include the
• Pressure(P)necessary to cause a flow(V)of gas to enter the
airway and increase the volume(V)of the lungs
• There are two types of waveforms
• Scalars : The control variable(pressure ,volume and flow) are
plotted on the Y axis and time(seconds) in the X axis.
• Loops : One control variable is plotted against
another(volume plotted against pressure or flow against
volume)
• The ventilator graphic display provides the following
parameters:
• Scalar waveforms: a. Pressure waveform
b. Flow waveform
c. Volume waveform
31. • Loop waveform : a. Pressure volume loop
b. Flow volume loop
PRESSURE WAVEFORM
a. The shape of the curve represents the breath type eg.
pressure limited (square) and volume limited(triangular).
b. The component of the pressure waveform curve: PIP is the
maximum pressure point on the curve.
PEEP is the baseline pressure and MAP is the area under the
curve.
Plateau pressure is measured during inspiratory hold or
prolonged Ti.
• Triggering is indicated by the presence of a negative
deflection
• Airway obstruction is indicated by disproportionate rise in
peak airway pressure
• Air trapping indicated by the PEEP that fails to touch baseline.
32.
33. Volume waveforms
• In a constant flow, volume limited ventilation, the upstroke is
inspiration and the down stroke is expiration and the
corresponding peak volume on the Y axis is the tidal volume.
• Other information obtained include , ET tube leak , broncho
pleural fistula and auto PEEP which is evident by the failure of
the expiratory limb to return to baseline.
• During active exhalation the expiratory limb extends well
below the base line.
• Flow waveforms
• The shape of the flow waveform is square in volume
ventilation and descending ramp in pressure ventilation.
34.
35.
36.
37. • Graphic loops
• Pressure –volume (P-V) loops
• The pressure is plotted on the X-axis and volume on the Y axis.
• On the P-V loop, notable measurements on the X-axis are PIP
and PEEP, and on the Y-axis is the inspired tidal volume.
• Since volume change in relation to pressure change defines
compliance.
• A line drawn between each end points of the curve is the
compliance line and the slope of the line indicates the
compliance of the system.
• Normally the compliance line is 45 degree, if its more towards
the vertical line, compliance is improving and conversely
compliance is decreasing.
40. High frequency ventilation
• HF is general term that refers to a family of ventilator
techniques that utilize ventilator rates greater than 60
breaths/min and tidal volumes that are usually less or equal
to the anatomical dead space of the airways
• Four types
• High frequency positive pressure ventilator(HFPPV)
• High frequency flow interrupter(HFFI)
• High frequency jet ventilator(HFJV)
• High frequency oscillatory ventilator(HFOV)
HFOV & HFJV are most commonly used in neonatal and pediatric
patients.
41. • HFJV delivers short pulses of pressurized gas directly into the
upper airway through a narrow-bore cannula or jet injector.
HFJVs are capable of maintaining ventilation over wide ranges
of patient sizes and lung compliances.
• These systems have negligible compressible volumes and
operate effectively at rates from 150 to 600 breaths/min (2.5-
10 Hz), with the most common rates, 240 to 420 breaths/min,
HFJV is used in combination with a CMV
• Tidal volumes are difficult to measure but appear to be equal
to or slightly greater than anatomic dead space.
42. • High-frequency oscillators (HFOs) are a type of HFV that
use piston pumps or vibrating diaphragms, operating at
frequencies ranging from 180 to 2400 breaths/min
(3-40 Hz), to vibrate air in and out of the lungs.
• During HFOV, inspiration and expiration are both active
(proximal
• Oscillators produce little bulk gas delivery.
• The amplitude of the pressure oscillations within the airway
determine the tiny tidal volumes that are delivered to the
lungs around a constant mean airway pressure.
• This allows avoidance of high peak airway pressures for
ventilation as well as maintenance of lung recruitment by
avoidance of low end-expiratory pressures.
• During HFOV, airway pressures usually are measured
either at the proximal end of the endotracheal tube
or within the ventilator itself.
43. • The basic difference between HFV and conventional
ventilation(CV) is that in CV the movement of gas from the
airways to the alveoli is by bulk flow, where in HF multiple
modes of gas transport occur including bulk convection, high
frequency ‘pendelluft’, convective dispersion, taylor type
dispersion and molecular diffusion.
• During HFV, minute ventilation and the CO2 washout are
proportional to the product of ventilator frequency and the
square of the tidal volume.
• Airway pressure monitored in a HFV is measured distally,
inside the trachea, whereas the pressure displayed on the CV
is a proximal value.
• HFV is beneficial in severe pulmonary failure because it uses
tidal volume smaller than dead space , it enables the safe
application of higher PEEP and MAP to open collapsed alveoli
and keep them open and improves V/Q matching.
46. Disease specific initial ventilator settings in
newborn babies
• Respiratory distress syndrome
• It is characterised by surfactant deficiency
• High surface tension in the alveoli leads to alveolar collapse,
atelectasis,V/Q mismatch.
• In preterm infants with RDS, early use of CPAP, may decrease
the need for mechanical ventilation
• Mechanical ventilation and surfactant administration should
be considered in babies with significant work of breathing,
apnea, hypoxemia(PaO2<50mmHg),FiO2 requirement >40-
50% and hypercarbia(PaO2>60 mmHg).
• Ventilator setting
• Early therapeutic CPAP
• Early surfactant
• Rapid rates 40-60/min
47. • Moderate PEEP 4-5 cm H2O
• Low PIP 10-20 cm H2O
• Short Ti 0.25-0.4 s
• Low tidal volume 3-6ml/kg
• Early extubation to nasal CPAP.
• In ventilated infants the following strategies can be employed
to provide gentle ventilation.
• Permissive hypercapnia: Accepting PaCo2 upto 60mmHg
• Permissive hypoxemia : Maintain SaO2 between 87%-92% and
the arterial oxygen saturation between 40-60mmHg.
• If BPD is established, to avoid the development of cor
pulmonale, it may be resonable to maintain PaO2 of 50 mmHg
• Minimal peak pressure, low VT and rapid rates: Studies have
shown that a faster ventilator rate with a lower tidal volume
produces less volutrauma compared to a slower ventilator
rate with a larger VT.
48. • Ventilator adjustments:Co2 elimination is better achieved by
increasing rate rather than by increasing the PIP, as an
increase in PIP will increase VT and may induce volutrauma.
• If there is hypocarbia, the PIP rather than ventilator rate
should be first reduced if the chest rise is adequate.
• Extubation can be attempted when there is adequate
spontaneous respiratory effort and the infant is on low
ventilator settings(Rate10-25/min,FiO2<0.4,PIP low with good
lung compliance)
• Extubation to NCPAP and loading with methyl xanthenes
should be considered in preterm infants less than 28 weeks
gestation to decrease the incidence of extubation failure and
apneic episodes.
• Early therapeutic CPAP and early surfactant treatment
followed by rapid extubation to CPAP may help reduce
mechanical ventilation-induced lung injury and reduce BPD.
49. • Chronic lung disease or BPD
• A 2001 NICHD consensus statement defines BPD as
requirement for supplemental oxygen for 21 of the 28 days of
life and identifies 3 grades of severity of BPD( mild ,moderate
& severe)depending on the duration and level of
supplemental oxygen and mechanical ventilatory support at
36 weeks postmenstrual age in preterm infants.
• The lung pathology in BPD is heterogenous with areas of
atelectasis alternating with air trapping.
• The compliance is reduced and the airway resistance is high,
this produces higher time constant
• The goals are to employ minimal ventilatory settings to
achieve gas exchange
50. • Settings
• Slower rates 20-40 / min
• Moderate PEEP 4-8 cm H20
• Lowest PIP required 20-30cm H2O
• Longer Ti 0.4-0.7 seconds
• VT 5-8 ml/kg or more
• Pulmonary interstitial emphysema(PIE) and air leaks
• The main principles for ventilation of PIE are to further reduce
barotrauma by decreasing the peak airway pressure, MAP and
PEEP and by increasing the expiratory time to minimize
further gas trapping.
• PIP 12-15cm H20
• PEEP 4-6 cm H2O
• RATE: approprite rate without compromising the Te
• I:E ratio 1:2 to 1:3
51. • Meconium aspiration syndrome
• Respiratory distress in meconium aspiration syndrome is
characterized by areas of atelectasis due to complete airway
obstruction by particulate meconium and areas of air
trapping(obstructive emphysema) due to ball valve effect and
incomplete obstruction by meconium.
• Lung mechanics in MAS include increased airway resistence,
prolonged time constant, increased FRC as well as decreased
compliance.
• CPAP and mechanical ventilation is initially avoided in these
infants for fear of air leaks and supplemental oxygen alone is
tried first.
• PaO2 60-80 mmHg and SaO2 between 92-97% should be
maintained to avoid PPHN.
• Mechanical ventilation should be considered in MAS if PaO2
<50mmHg,PaCo2>60 mmHg or Ph <7.25 with FiO2>0.8
52. • Ventilatory settings
• PIP, use lower PIP (not exceeding 25cm H2O)
• PEEP 4-6 CM H2O
• Rate 40-60/min
• I:E ratio 1:2 to 1:3
• Congenital diaphragmatic hernia(CDH)
• Herniation of abdominal contents in the thorax coincides with
the period of pulmonary parenchymal and vascular
development.
• Pulmonary hypoplasia results in decreased surface area for
gas exchange(leading to hypoxemia, hypercarbia and
acidosis)and increased pulmonary vascular resistance (PPHN).
53. • Initial ventilator settings should aim to produce gentle
ventilation and acceptable SaO2 levels (preductal
SaO2>85%),pH 7.25-7.35 and PaCO2 45-65 mmHg.
• PIP 20-22cm H20
• PEEP 3-5cm H2O
• MAP <12cm H2O
• RATE 20-40/min
• Ti 0.35sec
• FiO2 50-100%
• High frequency ventilation should be considered if high peak
pressures>25mmHg are required or if there is persistent
hypercarbia (>60mmHg )or hypoxia, unresponsive to
conventional ventilation.
54. • Mechanical ventilation for non pulmonary conditions
• Birth asphyxia, apnea of prematurity and immediate post
operative care are some of the situations where mechanical
ventilation is instituted until spontaneous efforts are
established by the patient.
• Ventilatory goals are pH 7.35-7.45,PaCo2 35-45 mmHg and
SaO2 between 92-95%.
• PIP 12-14cmH2O
• PEEP 3-4 cmH2O
• RATE 30-40/min
• Ti 0.3-0.4 sec
• I:E ratio 1:2
55. Weaning from the ventilator
• Weaning is a process of gradual transition from mechanical to
spontaneous breathing by decreasing the support provided by
the ventilator.
• Following parameters to be considered:
• Resolution of underlying condition causing respiratory failure.
• Adequate gas exchange with minimal settings: PaO2>60mmHg
with FiO2<30-40% and PEEP <5cm H2O
• Adequate spontaneous breathing.
• Hemodynamic stability (normal cardiac function with minimal
or no inotropic support).
• Absence of major organ dysfunction.
• Normal electrolytes, adequate nutrition and normal body
temperature also facilitate successful weaning.
56. • Stepwise weaning protocols
• Oxygenation Ventilation
Determinants
PIP Tidal volume
PEEP PIP-PEEP(delta P)
Ti RATE: I:E ratio
Minute ventilation(VT*RR)
• Decrease FiO2 to 30-40% - decrease VT
• Decrease PIP,PEEP - decrease delta P(PIP)
• Decrease Ti - decrease rate
• IF CO2 retention,increase -if hypoxemia is an issue
rate,PIP,PEEP. Increase PEEP
57. • PRINCIPLES
• Ensure normal minute ventilation (in neonates 4ml/kg * 60
=360ml)
• Ensure adequate tidal volume(min 4ml/kg)to overcome the
imposed work of breathing.
• Avoid fatigue by supporting the spontaneous breaths.
• Ensure adequate rest and sleep(slow weaning procedure).
• Correct reversible factors that impede weaning i.e anemia,
poor nutrition, excessive sedation, airway secretions.
• Weaning can either be accompalished by trials of
spontaneous breathing on the endotracheal tube for
progressively longer periods of time, or by gradually
decreasing the level of support on IMV,SIMV or pressure
support ventilation(PSV).
58. • During a T piece trial, the patient is disconnected from the
ventilator, a T piece is attached to the endotracheal tube and
an appropriate concentration of oxygen is administered
through one limb of the T piece.
• The patient is encouraged to breath on his own through the
endotracheal tube, initially for brief intervals of time.
• These periods of spontaneous breathing are progressively
increased until the patient is capable of breathing on his own
for a reasonable period of time without manifesting any signs
of distress.
• In assist or control mode, each spontaneous effort would
result in the delivery of mandatory breath.
• So decreasing the rate has no effect as long as patient’s RR is
more than the set rate.
• Wean PIP but maintain a delta P to deliver adequate VT
59. • Weaning method in SIMV are similar to IMV, i.e weaning is
achieved by decreasing the SIMV rate and PIP, and maintain a
tidal volume delivery of atleast 4ml/kg.
• Common causes of failure to wean
• Neurological : sedation, apnea of prematurity and decreased
respiratory drive.
• Respiratory :superimposed ventilator associated pneumonia,
laryngeal edema and secretions.
• Cardiovascular : poor myocardial function due to various
reasons, septic shock and anemia.
• Electrolyte imbalance: low potassium, magnesium and
phosphorous aggravate muscle weakness.
• Metabolic alkalosis due to diuretics.
• Poor parenteral nutrition.
60. • Post extubation care
• After extubation close monitoring and care should be
provided
• CPAP appears to stabilize the upper airway, improve lung
function and reduce apnea(infants extubated to nasal CPAP,
experience a reduction in the frequency of apnea,
bradycardia, respiratory acidosis and increasing oxygen
saturation)
• Nasal cannula or oxygen hood can be used if there is oxygen
requirement.
• Preterm babies at risk of apnea of prematurity may benefit
from caffeine loading at least 2hrs prior to extubation caffeine
base is administered in a dose of 10mg/kg loading dose
followed by maintenance at 3-5 mg/kg/day 24 hrs after the
loading.
61. • Clinically relevant post extubation laryngeal edema occurs in
up to 30% of extubated patients and 4% of patients need to
be reintubated
• If stridor is severe with increased work of breathing consider
re –intubation
• To reduce edema ,medications used are epinephrine and
corticosteroids.
• Supportive care during ventilation :
• Proper assessment of vital signs supplemented by electronic
monitoring of :
• Heart rate
• Oxygen saturation
• Blood pressure
• End tidal or transcutaneous co2 measurements are essential
62. • Hydration status
• Urine output
• Intake charting
• Physical examination include monitoring for
• Respiratory distress
• Chest symmetry
• Chest vibrations in high frequency ventilator
• Air entry
• Presence of added sounds
• Cardiac murmur
• Others:
• Thermal homeostasis:use servocontrolled warmers or
incubators,IVF should be pre warmed and avoid direct contact
with cold x- ray plate.
63. • Endotracheal tube positioning
• The position of ET tube should be documented in the nursing
flow sheet and checked during each assessment.
• A properly placed tube should lie below the levels of clavicles
at T2 level above carina.
• Endotracheal tube suctioning : suction is performed only as
needed based on patient assessment.
• Indications are:
• Visible secretions in ETT
• Audible secretions or presence of rhonchi, coarse and/or
decreased breath sounds.
• Change in respiratory rate and /or rhythm
• Oxygen desaturation or bradycardia
• Changes in blood gas values.
• Restlessness and agitation
• Increased proximal airway pressure on the ventilator.
64. • Complications of ET suctioning Bradycardia, hypoxia,
hypercarbia and tracheal mucosal damage, after the
procedure , lung decruitment and atelectasis can occur.
• Prevention of ventilator associated pneumonia(VAP)
• Orotracheal route of intubation.
• Use of new ventilator circuits for each patient.
• Change of humidifiers every 5 to 7 days.
• Use of close endotracheal suctioning system.
• Elevation of the head of the bed to 45 degree and use of oral
antiseptic chlorhexidine may decrease the incidence of VAP.
• Chest physiotherapy
studies suggest chest physiotherapy should not be routinely
performed.
65. • Prone positioning during mechanical ventilation has been
used to improve oxygenation in severe hypoxemic respiratory
failure.
• Physiological effect of mechanical ventilation
• Effect on airway: laryngeal edema, injury to trachea.
• Higher MAP interferes with venous return and right heart
filling, the increased PVR can interfere with left ventricular
filling ,decreases cardiac output and lead to hypotension.
• Urine output may decrease secondary to decreased cardiac
output or reduced atrial natriuretic hormone release.
• Gastric distension and stress ulcers can occur.
• In children with head injury, MAP can raise ICP.
66. ERRORS RELATED TO MECHANICAL VENTILATION
Endotracheal Intubation
• Use of wrong size of endotracheal tube
• Right main-stem bronchus intubation
• Unplanned extubation
• Obstruction of endotracheal tube due to inadequate suction
• Airway injury leading to subglottic stenosis
• Tracheal perforation from endotracheal tube suction catheter
• Kinking of endotracheal tube
Initiation of Mechanical Ventilation
• Improper setup of ventilator and accessories
• Failure to add water to humidifier
• Misconnection of ventilator tubings
• Omission of safety limits on ventilator settings
• Omission of alarm settings
67. Use of Mechanical Ventilation
•Delay in changing ventilator settings in response to blood gas
results
• Inadvertent delivery of high or low ventilator pressures
(e.g.,auto PEEP)
• Failure to wean inhaled oxygen when oxygen saturation is high
• Ventilator associated pneumonia
• Inadequate drainage of condensate in ventilator tubing leading
to inadvertent pulmonary lavage
• Ventilator failure due to poor maintenance by biomedical
engineering
• Overriding ventilator alarms
• Ignoring ventilator alarms
68. • Ventilator emergencies
• Common causes of sudden deterioration in the condition of
a ventilated child:
• Displacement of the tube
• Obstruction of the tube
• Pneumothorax
• Equipment failure.
To conclude:
Ventilator care requires a team effort,Everyone involved has
to get along and trust one another.
