Mechanical ventilation in neonates by dr naved akhter

Mechanical Ventilation in Neonates

By: Dr. Naved Akhter20/03/14

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.

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,

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).

• 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.

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.

• 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) .

• 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.

• 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.

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.

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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.

Breath type Trigger (phase variable)

Cycle Limit

Mandatory Machine Machine Machine

Assisted Patient Machine Machine

Supported Patient Patient Machine

Spontaneous Patient Patient Ptient

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.

• 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.

• 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.

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.

• 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.

• 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.

• 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.

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.

Ventilator variables

Pressure controlled ventilation

Volume controlled ventilation

Variables set 1.PIP2.Rate 3.inspiratory time or I:E4.PEEP5.Trigger sensitivity.

1.Tidal volume2.Rate3.Inspiratory time(controls flow rate)4.PEEP5.Trigger sensitivity.

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.

• 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.

Blood gas abnormality and changes in the ventilator settings to correct them

Blood gas abnormality Corrective measuresFio2 /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.

• 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

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.

• 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.

• 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.

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

• Loop waveform : a. Pressure volume loop b. Flow volume loopPRESSURE WAVEFORMa. 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.

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.

• 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.

Flow volume loops

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.

• 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.

• 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.

• 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.

High frequency ventilator

TRIPLE LUMEN ET TUBE TO BE USED WITH HFJV

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

• 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.

• 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.

• 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

• 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

• 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

• 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).

• 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.

• 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

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.

• Stepwise weaning protocols• Oxygenation VentilationDeterminants PIP Tidal volumePEEP 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

• 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).

• 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

• 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.

• 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.

• 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

• 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.

• 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.

• 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.

• 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.

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

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

• 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.

WITH SPECIAL THANKS TO DR PANKAJ MITTAL FOR HIS GUIDANCE

THANK YOU

Silverman scoring for Retractions

Guidelines for high frequency ventilation