Neonatal Ventilation

Invasive Neonatal Ventilation
Dr Badr Chaban 28/01/09

Invasive Neonatal Ventilation
     

Conventional Mechanical Ventilation CMV Intermittent Mandatory Ventilation IMV Synchronized Intermittent Mandatory Ventilation SIMV Assist/Control Ventilation IPPV A/C Pressure-Support Ventilation PSV Patient-Triggered Ventilation S

Ventilatory Techniques
 Pressure-Limited Ventilation  Pressure-Controlled Ventilation  Volume Ventilation  Volume Guarantee  Pressure-Regulated Volume Control  Volume-Assured Pressure Support  Proportional Assist Ventilation

Ventilatory Styles
 Conservative or “Gentle” Ventilation  Nasopharyngeal Synchronized  Intermittent Mandatory Ventilation

Goals of Mechanical Ventilation
 (1)

adequate pulmonary gas ex-change,  (2) ↓ risk of lung injury,  (3) ↓ (WOB),  (4) optimize patient comfort.

Ideal Mode of Ventilation
        

Delivers a breath that: Synchronizes with the patient’s spontaneous respiratory effort Maintains adequate and consistent tidal volume and minute ventilation at low airway pressures Responds to rapid changes in pulmonary mechanics or patient demand Provides the lowest possible WOB

Ideal Ventilator Design
        

Achieves all the important goals of mechanical ventilation Provides a variety of modes that can ventilate even the most challenging pulmonary diseases Has monitoring capabilities to adequately assess ventilator and patient performance Has safety features and alarms that offer lung protective strategies

Carbon Dioxide (CO2) Elimination
alveolar minute ventilation = (tidal volume - dead space) x frequency

Relationships among various ventilator-controlled (shaded circles) and

Carlo, W. A. et al. Pediatrics in Review 1999;20:117-126e
Copyright ©1999 American Academy of Pediatrics

Determinants of oxygenation during pressure-limited,

Carlo, W. A. et al. Pediatrics in Review 1999;20:117-126e
Copyright ©1999 American Academy of Pediatrics

 MAP = K (PIP - PEEP) (TI/TI + TE) +

PEEP  K is a constant determined by the flow rate and the rate of rise of the airway pressure curve

COMPLIANCE
 Compliance describes the elasticity or

distensibility (eg, lungs, chest wall, respiratory system)
 compliance =

volume/ pressure

 in neonates who have normal lungs

ranges from 0.003 to 0.006 L/cm H2O compared with compliance in neonates who have RDS, which may be as low as 0.0005 to 0.001 L/cm H2O.

 RESISTANCE

Resistance describes the inherent capacity of the air conducting system (eg, airways, endotracheal tube) and tissues to oppose airflow and is expressed as the change in pressure per unit change in flow:  resistance = pressure/ flow

Airway resistance depends on
1) 2) 3) 4)

radii of the airways (total cross-sectional area), length of airways, flow rate, density and viscosity of gas breathed.

Resistance Δ Pressure (cm H2O) Δ Flow (L/sec) Normal lungs: 20-40 cm H2O/L/sec RDS: 20-40 cm H2O/L/sec Intubated infant: 50-150 cm H2O/L/sec

The time constant of the respiratory system is a measure of the time necessary for the alveolar pressure to reach 63% of the change in airway pressure

 time constant = resistance x compliance  For example, the lungs of a healthy

neonate with a compliance of 0.004 L/cm H2O and a resistance of 30 cm H2O/L/s have a time constant of 0.12 seconds.

Carlo, W. A. et al. Pediatrics in Review 1999;20:117-126e

CMV

IMV

SIMV

SIMV+VG

IPPV

SIPPV A/C

SIPPV+VG

PSV
 Pressure

support ventilation (PSV) is a mode where flow cycling is used to assist every spontaneous inspiratory effort and terminate the mechanical breath as the spontaneous inspiration ends or inflation is completed



  

Synchronous breath termination gives the infant greater control over the frequency and duration of inspiration, while the support pressure compensates for instrumental and disease induced loads. In the event of apnea, back-up IMV ensures ventilation. In some ventilators PSV can be combined with a low SIMV rate

PROPORTIONAL ASSIST VENTILATION PAV  proportional assist ventilation matches the onset and

duration of both inspiratory and expiratory support. Furthermore, ventilatory support is in proportion to the volume and flow of the spontaneous breath. Thus, the ventilator can decrease the elastic or resistive work of breathing selectively. The magnitude of the support can be adjusted according to the patient’s needs. When compared with conventional and patient-triggered ventilation, proportional assist ventilation reduces ventilatory pressures while maintaining or improving gas exchange.

Ideal Monitoring Features
 Proximal airway

monitoring,  real-time pulmonary graphics:  Waveforms  Loops  Mechanics  Trending

 Volume Guarantee  Dräger Babylog

Pressure Regulated Volume  Control and Volume Support  Siemens 300  Volume Assured Pressure Support  VIP BIRD Gold


Neonatal Ventilation
Dr Badr Chaban 11/02/09

High-Frequency Ventilation
HFV is a radical departure from standard, conventional mechanical ventilation. There are several types of HFV devices, including (HFJV), HFOV, and hybrids. The rationale for HFV is that the provision of tiny gas volumes at rapid rates results in much lower alveolar pressure

 MAP provides a constant distending

pressure equivalent to CPAP.
 This inflates the lung to a

constant and optimal lung volume maximising the area for gas exchange and preventing alveolar collapse in the expiratory phase. 

Indications for high frequency ventilation include
1. Rescue

following failure of conventional ventilation (PPHN, MAS). 2. Air leak syndromes (pneumothorax, pulmonary interstitial emphysema) 3. To reduce barotrauma when conventional ventilator settings are high.

Terminology
Frequency  High frequency ventilation rate (Hz, cycles per second) MAP  Mean airway pressure (cmH2O) Amplitude  delta P or power is the variation around the MAP Oxygenation is dependent on MAP and FiO2

 Ventilation is dependent on amplitude and

to lesser degree frequency.
 Thus when using HFV CO2 elimination

and oxygenation are independent.

Making adjustments once established on HFV Poor Over Oxygenatio Oxygenatio n n Increase Decrease FiO2 FiO2 Increase Decrease MAP MAP (1-2cmH2O) (1-2cmH2O) Under Ventilation Increase Amplitude Decrease Frequency  (1-2Hz) if Amplitude Maximal Over Ventilation Decrease Amplitude Increase Frequency  (1-2Hz) if Amplitude Minimal

Continuous Positive Airway Pressure
  

 

Gregory et al in 1971. applied CPAP in RDS. Although the first application of CPAP was through the endotracheal tube. It soon became apparent that it could also be applied nasally, since most newborns are obligate nasal breathers. At the same time, the mouth acts as a pressure relief valve if the applied pressure is too high. Use of nasal CPAP also obviated face masks, face chambers, and head boxes.

Advantages of CPAP
 regular

infants.  This may be attributed to reducing thoracic distortion  and stabilizing the chest wall, splinting the airway and  the diaphragm, decreasing obstructive apnea, and enhancing  surfactant release.

pattern of breathing in preterm

CPAP delivery systems contain 3 major components. The first is a circuit to provide a continuous flow of inspired gas, which must be warmed and humidified. The second is an interface to connect the circuit to the airway. Binasal tubes or prongs are the most commonly used. Newer devices use fluidics to reduce expiratory resistance and decrease the WOB. The third component is a device to generate positive pressure.

COIN trial
Recent trials using nCPAP from birth in 25 to 28 week infants describe more customised strategies: in the COIN trial, 27-28 week infants breathing at birth benefit the most from nCPAP.

Fewer infants received oxygen on day 28; they had fewer days of ventilation and no increase in morbidities despite having more pneumothoraces.

REVE trial
The suggests that intubation with early surfactant administration followed by nCPAP mostly benefits to 25-26 week infants. Thus, nCPAP is feasible from birth. The overall strategy should take into account infants' gestational age, maturation and behaviour in the delivery room.
Hascoet et la Dec 2008

Complication
Nasal Septal Erosion or Necrosis Pneumothorax

• This is preventable when using appropriate sized prongs that are correctly positioned. • Usually occurs in acute phase. • It is uncommon (<5%). • It usually results from the underlying disease process rather than positive pressure alone. • It is not a contraindication to the use of CPAP.

Abdominal Distension from • This is benign Swallowing • Easily reduced with gastric drainage or aspiration Air Nasal obstruction

• From improper prong placement or inadequate airway care

NIPPV
Neonatal nasal intermittent positive pressure ventilation (NIPPV) provides non-invasive respiratory support to premature infants who may otherwise require endotracheal intubation and ventilation.

NIPPV is the augmentation of continuous positive airway pressure (CPAP) with superimposed inflations, to a set peak pressure

HOW DOES NIPPV WORK
      

the mechanism of action of NIPPV remains uncertain. Hypotheses include: increasing pharyngeal dilation improving the respiratory drive inducing Head’s paradoxical reflex increasing mean airway pressure allowing recruitment of alveoli increasing functional residual capacity; increasing tidal and minute volume.

Arch. Dis. Child. Fetal Neonatal Ed., Sep 2007; 92: F414 - F418.

SNIPPV
Synchronisation, defined as mechanical inflation commencing within 100 ms of the onset of inspiration, uses a capsule to detect abdominal movement at the start of inspiration.

WHAT VENTILATOR SETTINGS SHOULD WE USE DURING NIPPV?

PEEP 3-6 cm H2O PIP 8-21 cm H2o R 10-30 /m iT 0.4-0.6 s Flow 8-10 l/m up to 15 l/m

NON-INVASIVE SYNCHRONISED MECHANICAL VENTILATION

 Synchronisation techniques enabled

delivery of  (N-A/C)  (N-SIMV)  N A/C  N PSV  N PAS

 In comparison to nasal continuous positive

airway pressure (NCPAP), N-SIMV reduced chest wall distortion in preterm infants following extubation, while N-A/C reduced breathing effort and improved ventilation.

Three randomised trials have shown the consistent efficacy of N-SIMV in the post-extubation period as indicated by better respiratory evolution and lower extubation failure. These reports suggest that reduced apnea is responsible in part for these effects and that infants with worse lung mechanics are likely to benefit more from N-SIMV. These data also showed a tendency towards reduced oxygen dependency among infants extubated to N-SIMV .
Eduardo Bancalari miami

In summary,
Data from physiological and clinical trials indicate that non-invasive synchronised ventilation has important benefits. Despite this evidence, the use of non-invasive synchronised ventilation is uncommon, perhaps because few such ventilators are available. More importantly, there are few data on the use of non-invasive synchronised ventilation to avoid earlier use of invasive ventilation.

S.NCPAP setting
PEEP 5 PIP up to 20 10-40 iT 0.25-1s Flow depend on the leak

Thank you