Outline of talk

1
Golden Hour Lung Protective Strategy from Birth

• Proper pressures in the DR
• Proper FiO2 in the DR (blended)
• Surfactant in the DR
• CPAP in the DR
• Consistent CPAP in the NICU
• Reduced SIMV in the NICU

2
(No Transcript)
3
good judgement
informed jugement
4
Neo-Puff in the DR

• manual ventilation of
• babies lt30 weeks gest.
• Used for all transport
• ventilation for all babies

5
Neo-Puff Infant Resuscitator

• easy to use,
• manually operated
• gas-powered.

6
Controlled and Precise Peak Inspiratory Pressure
(PIP) The Neopuff Infant Resuscitator will
inflate the babys lungs provide optimum
oxygenation by delivering consistent PIP with
each breath, limiting the risks associated with
under or over inflation at uncontrolled
pressures. Consistent and Precise Positive End
Expiratory Pressure (PEEP) The Neopuff Infant
Resuscitator maintains Functional Residual
Capacity (FRC) by providing a consistent PEEP
throughout the resuscitation process.
7
The desired PIP is set by turning the
inspiratory pressure control. The desired
PEEP is set by adjusting the T-piece aperture.
8
(No Transcript)
9
(No Transcript)
10
Pressure/Volume
11
Over Weaning damages too
12
Ventilator-Associated Lung Injury

• Barotrauma (air leak)
• Oxygen toxicity
• Ventilator associated pneumonia
• Over-distention
• De-recruitment

13
Biochemical Injury Biophysical
Injury

• Shear
• Overdistention
• Cyclic stretch
• Inc. intrathoracic pressure

Cytokines, prostanoids, Leukotrienes, reactive
oxygen species, protease

• Inc alveolar cap permeability
• Dec cardiac output
• Dec organ perfusion
• Tissue injury secondary to
• Inflamatory mediators/cells
• Impaired O2 delivery
• bacteremia

Distal Organs
neutrophil
Slutsky and Tremblay Am J Respir Crit Care Med
1998 157 1721-1725
Death
MOSF
14
normal lungs
20 min of 45 cm H2O
5 min of 45 cm H2O
Dreyfuss, Am J Respir Crit Care Med
1998157294-323
15
14/0 45/10
45/0
Webb and Tierney, Am Rev Respir Dis 1974
110556-565
16
(No Transcript)
17
esophagealintubation
18

• Pulmonary
• Interstitial
• Emphesema
• to Pneumo-

19
(No Transcript)
20
Assessment

• Chest x-ray AP
• 8 rib conventional
• 9-10 rib Hi-Fi
• Rise fall of chest (slight per NRP)
• Listen to breath sounds
• Vt 5-7 ml/kg (3-5 spont.)
• follow ABGs

21
Pressure Wave

• To Increase Mean Airway Pressure
• 1. Increase flow
• 2. Increase peak pressure
• 3. Lengthen inspiratory time
• 4. Increase PEEP
• 5. Increase Rate

22
(No Transcript)
23
TYPES OF MECHANICAL VENTILATION

• negative pressure ventilation
• positive pressure ventilation
• high-frequency ventilation
• non-invasive positive pressure ventilation

24
Body Box
25
Outline

• Respiratory mechanics and gas exchange
• Factors affecting oxygenation and carbon dioxide
  elimination during mechanical ventilation
• Blood gas analysis
• Ventilatory management basics and specifics
• High frequency ventilation the basics

26
Overview

• Mechanical ventilation is an integral part of
  neonatal intensive care, and has led to increased
  survival of neonates over the last 3 decades
• Advances in knowledge of neonatal respiratory
  physiology have led to optimization of techniques
  and strategies
• Conventional mechanical ventilation (CMV) is most
  often used, despite the advent of HFV and SIMV

27
Overview

• Respiratory failure in neonates has significant
  morbidity and mortality (although less than in
  the past)
• Optimal ventilatory management will reduce the
  risk of chronic lung disease
• Optimal ventilatory management should be
  individualized and be based upon the
  pathophysiology and certain basic concepts of
  mechanical ventilation

28
Concepts

• Goal of mechanical ventilation to improve gas
  exchange and to sustain life without inducing
  lung injury
• Factors that should influence ventilator
  adjustment decisions
• Pulmonary mechanics
• Gas exchange
• Control of breathing
• Lung injury

29
Pulmonary mechanics

• Compliance
• Property of distensibility of the lungs and chest
  wall
• Change in volume per unit change in pressure
• C D Volume
• D Pressure
• Neonatal lung
• Normal 0.003-0.006 L/cm H2O
• with RDS 0.0005-0.001 L/cm H2O

30
Pulmonary mechanics

• Resistance
• inherent capacity of the air conducting system
  (airways and ETT) and tissues to resist airflow
• Change in pressure per unit change in flow
• R D Pressure
• D Flow
• Total cross-sectional area of airways
• Resistance Length of the airways
• Flow rate
• Density and viscosity of gas

31
Pulmonary mechanics

• Location of airway resistance
• 0 5 10 15 20
• Distal airways contribute less to resistance due
  to increased total cross-sectional area
• Small ETT and high flow rates can increase
  resistance markedly

Resistance
Distal --gt
Airway Generation
32
Pulmonary mechanics

• Laminar flow (Distal airways)
• Driving pressure proportional to flow
• R 8 n l (n viscosity l length r
  radius)
• p r4
• Turbulent flow (Proximal airways)
• Driving pressure proportional to square of flow
• Reynolds number (Re) 2 r V d (d density)
• n

33
Pulmonary mechanics

• A pressure gradient between the upper airway and
  alveoli is necessary for gas flow during
  inspiration and expiration
• The pressure gradient is required to overcome the
  elasticity, resistance, and inertance of the
  respiratory system
• Equation of motion P 1 V R V I V
• C

ElasticityResistanceInertance
34
Pulmonary mechanics

• Time constant
• The time taken for the airway pressure (and
  volume) changes to equilibrate throughout the
  lung is proportional to the compliance and
  resistance of the respiratory system
• Time constant Compliance x Resistance

35
Pulmonary mechanics

• change in pressure in relation to time
• Almost full equilibration 3-5 time constants

99
98
95
100
86
80
63
Change in pressure ()
60
40
20
0
1 2 3 4 5 Time constants
36
Pulmonary mechanics

• Healthy term neonate
• C 0.004 L/cm H2O R 30 cm H2O/L/sec
• T 0.004 x 30 0.12 sec
• Time constants Time (sec) equilibration
• 1 0.12 63
• 2 0.24 86
• 3 0.36 95
• 5 0.60 99
• RDS Shorter time constant

37
Pulmonary mechanics

• Application of the concept of time constant
• Short TI decreased tidal volume delivery
• Inadequate TE Gas trapping ( FRC,
  inadvertent PEEP)
• Heterogeneous lung disease (BPD) different
  regions of the lung have different time
  constants tendency for atelectasis and
  hyperexpansion to co-exist

38
Gas exchange

• Total minute ventilation tidal vol x freq
• VE VT x f
• Alveolar ventilation (VA) Useful (fresh gas)
  portion of minute ventilation that reaches gas
  exchange units excludes dead space (VD)
• VA (VT-VD) x f
• Alveolar ventilation equation
• VA (L/min) VCO2 (ml/min) x 0.863 (BTPS
  PACO2 (mm Hg)
  corr.)

39
Gas exchange

• Alveolar gas equation
• If R1, each molecule of O2 removed from alveoli
  is replaced by one molecule of CO2
• PAO2 PIO2 - PACO2
• Average normal value for R 0.8
• PAO2 FIO2 x (PB-PH2O) - PACO2x FIO2 1- FIO2
• R
• PaCO2 effective PACO2
• True PACO2 PETCO2

40
Gas exchange

• Ventilation-Perfusion matching
• matching of gas flow and blood flow required for
  successful gas exchange
• VA Alveolar ventilation
• Q Pulmonary blood flow (Fick method O2)
• 0.863 x R x (CaO2 - CVO2)
• PACO2
• V/Q mismatching usually relevant to effect on
  alveolar-arterial PO2 difference (A-a)DPO2

41
Gas exchange

• O2-CO2 diagram

0.2
v
0.5
1.0
V/Q 0
1.5
PCO2
Ideal V/Q 0.84
0 20 40 60
I
8
V/Q
40 60 80 100 120 140 160
P O2 (mm Hg)
42
Gas exchange

• Causes of hypoxemia
• V/Q mismatch
• Right to left shunt (venous admixture)
• Hypoventilation (e.g. in apnea)
• Diffusion abnormalities
• Causes of hypercapnia
• Hypoventilation
• Severe V/Q mismatch

43
Gas exchange

• Factors involved in gas exchange during
  mechanical ventilation
• Oxygenation
• Carbon dioxide elimination
• Gas transport mechanisms
• Patient - ventilator interactions

44
Gas exchange

• Factors affecting oxygenation
• Mean airway pressure (MAP) affects V/Q
  matching. MAP is the average airway pressure
  during respiratory cycle
• MAP K (PIP-PEEP) TI / (TITE) PEEP
• Oxygen concentration of inspired gas (FIO2)

45
Gas exchange

• MAP increases with increasing PIP, PEEP, TI to TE
  ratio, rate, and flow

PIP
Pressure
Flow
Rate
TI
PIP
PEEP
PEEP
Time
TI
TE
46
Gas exchange

• Relation of MAP to PaO2 not linear is like an
  inverted U
• Low MAP
• Atelectasis--gt very low PaO2
• High MAP
• hyperinflation--gt V/Q mismatch intrapulmonary
  shunt, hypoventilation due to distended alveoli
• decreased cardiac output --gt decreased oxygen
  transport despite adequate PaO2

47
Gas exchange

• For the same change in MAP, changes in PIP and
  PEEP improve oxygenation more than changes in IE
  ratio
• Reversed IE ratios increase risk of air-trapping
  
• PEEP levels higher than 6 cm H2O may not improve
  oxygenation in neonates
• Attainment of optimal MAP may allow weaning of
  FIO2
• Atelectasis may lead to sudden increase in
  required FIO2

48
Gas exchange

• Carbon dioxide elimination
• Proportional to alveolar ventilation (VA) which
  depends on tidal volume (VT) and frequency (rate)
  
• VT changes more effective (but more barotrauma)
  dead space constant, so proportion of VT that is
  alveolar ventilation increases to a greater
  degree with increases in VT
• VT 4 --gt 6cc/kg (50 ) with dead space of 2
  cc/kg increases VA from 2 (4-2) to 4 (6-2)
  cc/kg/breath (100 )

49
Gas exchange

• Clinical estimation of optimal TI and TE

Short TI Optimal TI Long TI
Inadeq VT Short insp. plateau Long plateau
Chest Wall Motion
Time
Short TE Optimal TE
Long TE
Air trapping Short exp. plateau Long exp.
plateau
Chest Wall Motion
50
Gas exchange

• Synchrony vs. Asynchrony fighting
• Synchrony augments ventilation, improves CO2
  elimination, decreases hypoxic episodes
• Asynchrony leads to poor tidal volume delivery,
  and impairs gas exchange
• Active exhalation (exhalation during ventilator
  breath) increases risk of hypoxic episodes

51
Blood gas analysis

• Arterial blood gas analysis the gold standard
• Interpretation
• pH Is it normal, acidotic, or alkalotic?
• PCO2 Is it normal, (respiratory acidosis), or
  (respiratory alkalosis)?
• HCO3 Is it normal, (metabolic acidosis), or
  (metabolic alkalosis)?
• Simple disorder or mixed? Compensated or not?
• PO2 Normal, hypoxia, or hyperoxia?

52
Blood gas analysis

• Normal values (1 hr age, not ventilated)
• Preterm pH 7.28-7.32, PCO2 35-45, PO2 50-80
• Term pH 7.30-7.35, PCO2 35-45, PO2 80-95
• Target values
• RDS pH gt 7.25, PCO2 45-55, PO2 50-70
• BPD pH gt 7.25, PCO2 45-70, PO2 60-80
• PPHN pH 7.50-7.60, PCO2 25-40, PO2 80-120
• Remember! O2 content determined mostly by SpO2
  and Hb.

53
Blood gas analysis

• Common errors
• Infrequent ventilator adjustments made only when
  ABG (q4/q6) is obtained. In acute phase of RDS or
  PPHN, adjustments should be made with chest rise,
  SpO2, TcPO2/PCO2 trends
• Room air contamination PCO2, PO2(if lt150
  torr ). Amount in butterfly set sufficient !
• Liquid heparin /saline contamination pH same,
  but lower PCO2 (mimics compensated metabolic
  acidosis)

54
Ventilatory management

• Indications
• Clinical Absolute Apnea (intractable), gasping,
  cyanosis not responsive to O2 by hood
• Relative Severe tachypnea / retractions
• Laboratory (while on CPAP or FiO2 gt 0.7)
• pH lt 7.25 with PCO2 gt 60
• (or) PO2 lt 45- 50 and / or SpO2 lt 85
• Other Surgical procedures, compromised airway

55
Ventilator settings

• PIP
• affects MAP (PO2) and VT (PCO2)
• PIP required depends largely on compliance of
  respiratory system
• Clinical gentle rise of chest with breath,
  similar to spontaneous breath
• Minimum effective PIP to be used. No relation to
  weight or airway resistance
• Neonate with RDS 15-30 cm H2O. Start low and
  increase.

56
Ventilator settings

• PEEP
• affects MAP (PO2), affects VT (PCO2) depending on
  position on P-V curve
• older infants (e.g. BPD) tolerate higher levels
  of PEEP (6-8 cm H2O) better
• RDS minimum 2-3, maximum 6 cm H2O.

Volume
PEEP PIP
Pressure
57
Ventilator settings

• Rate
• affects minute ventilation (PCO2)
• In general, rate ---gt PCO2
• Rate changes alone do not alter MAP (with
  constant IE ratio) or change PO2 , unless PVR
  changes with changes in pH
• However, if rate --gt TE lt 3TC --gt gas
  trapping--gt decreased VT--gt PCO2
• Minute ventilation plateaus, then falls with
  rate

58
Ventilator settings

• TI and TE
• Need to be 3-5 TC for complete inspiration and
  expiration (Note TC exp TC insp)
• Usual ranges TI sec TE sec
• RDS 0.2-0.45 0.4-0.6
• BPD 0.4-0.8 0.5-1.5
• PPHN 0.3-0.8 0.5-1.0
• Chest wall motion / VT may be useful in
  determining optimal TI and TE

59
Ventilator settings

• I E Ratio
• When corrected for the same MAP, changes in IE
  ratio do not affect gas exchange as much as
  changes in PIP or PEEP
• Changes in TI or TE do not change VT or PCO2
  unless they are too short (lt 3 TC)
• Reversed IE ratio No change in mortality or
  morbidity noted in studies. Not often used. May
  improve V/Q matching and PO2 at risk of
  venous return and gas trapping

60
Ventilator settings

• FiO2
• affects oxygenation directly
• with FiO2 lt0.6-0.7, risk of oxygen toxicity less
  than risk of barotrauma
• to improve oxygenation, increase FiO2 to 0.7
  before increasing MAP
• during weaning, once PIP is low enough, reduce
  FiO2 from 0.7 to 0.4. Maintenance of adequate MAP
  and V/Q matching may permit a reduction in FiO2

61
Ventilator settings

• Flow
• affects pressure waveform
• minimal effect on gas exchange as long as
  sufficient flow used
• increased flow--gt turbulence
• higher flow required if TI short, to maintain TV
• flow of 8-10 lpm usually sufficient
• change of flow may affect delivery of NO or
  anesthesia gases

62
Ventilatory management

• RDS
• Pathology decreased compliance, FRC
• Once diagnosis established, and if PO2lt50 on 40
  oxygen CPAP (or) early intubation and
  surfactant. (Prophylactic CPAP for ELBW not
  useful)
• Ventilation if FiO2 gt 0.7 required on CPAP
• Surfactant q 6 hrs if intubated and FiO2 gt
  0.3-0.4 (Survanta / Infasurf / Curosurf better
  than Exosurf). Usually 1-2, rarely 4 doses
  required.

63
Ventilatory management

• RDS (continued)
• Use lowest PIP required
• moderate PEEP (4-5 cm H2O)
• permissive hypercarbia (PaCO2 45-55 mmHg instead
  of 35-45 is safe, and need for ventilation in
  first 4 days)
• limited use of paralysis, aggressive weaning
• chest PT not useful, maybe dangerous in acute
  phase (increases IVH)

64
Ventilatory management

• Chronic lung disease / BPD
• usually heterogeneous lung disease - different
  areas of lung with different time constants
• increased resistance, frequent exacerbations
• higher PEEP often helpful (4-7 cm H2O)
• longer TI and TE, with low rates
• hypercarbia and compensated respiratory acidosis
  often tolerated to avoid increased lung injury

65
Ventilatory management

• PPHN
• ventilator management controversial
• FiO2 adjusted to maintain PaO2 80-100 to minimize
  hypoxia-mediated pulmonary vasoconstriction
• ventilatory rates and pressures adjusted to
  maintain mild alkalosis (pH 7.5-7.6), usually
  combined with bicarbonate infusion
• avoid low PaCO2 (lt20 mm Hg) to prevent cerebral
  vasoconstriction

66
Volume Guarantee
67
Pressure Support VentilationWorking Principle of
Breath Termination
Erin Browne
68
Flow SensorMeasurement Principle
T 400C no gas flow with gas flow

• Two tiny platinum wires are heated to 400C
• Gas flow cools the wire down
• From the amount of cooling the amount of gas
  flowing can be calculated

69
Endotracheal Tube Leak
70
Lung Function MonitoringClinical Applications

• Identification of Lung Overdistention
• Prediction of successful extubation
• Prediction of risk of BPD development
• Response to Surfactant or Brochodilators
• Teaching tool
• Titration of optimal PEEP
• Trend in development of disease
• Check of compliance during HFV
• recognition of recovery from suctioning

71
(No Transcript)
72
(No Transcript)
73
O S C I L L A T O R
74
(No Transcript)
75
High frequency ventilation

• Techniques
• HFPPV HFJV HFFI HFOV
• VT gtdead sp gt or lt ds gt or ltds
  ltds
• Exp passive passive passive
  active
• Wave- variable triangular triangular
  sine wave
• form
• Entrai- none possible none none
• ment
• Freq. 60-150 60-600 300-900
  300-3000

(/min)
76
High frequency ventilation

• HFPPV
• conventional ventilators with low-compliance
  tubing
• ventilatory rates of 60-150/min
• not very effective minute ventilation decreases
  with high frequencies
• ventilator and circuit design are not optimal for
  use at frequencies

77
High frequency ventilation

• HFJV (e.g. Bunnell Life Pulse HFJV)
• adequate gas exchange with lower MAP
• Servo pressure reflects volume ventilated
• increases with improving compliance or
  resistance or by peri-ET leaks
• decreased by worsening compliance, resistance,
  obstruction, or pneumothorax
• Larger babies 300 bpm smaller ones 500 bpm

78
High frequency ventilation

• HFJV (contd.)
• MAP controls PaO2, DP (and frequency) control
  PaCO2. (MAP controls lung volume. PaO2 will not
  respond to increased MAP if FRC normal)
• smaller TV (DP) with higher PEEP better than
  larger TV with lower PEEP (--gt hypoxia with
  hypocarbia)
• Optimal PEEP no drop in SpO2 when CMV off
• Parallel conventional ventilation recruits
  alveoli (use low rate 1-3 bpm 0-1 bpm if air
  leak)

79
High frequency ventilation

• HFOV (e.g. Sensormedics 3100A)
• Generally used at more MAP than CMV optimal MAP
  difficult to determine as CXR rib space
  counting not very accurate
• Frequency 5-10 Hz better for CO2 elimination
  10-15 Hz better for improving oxygenation
• maybe useful in airleak syndromes
• maybe useful in PPHN may decrease need for ECMO
  esp. if combined with NO

80
High frequency ventilation

• HFFI (e.g. Infant Star with HFFI module)
• active expiration in Infant Star model makes
  operation more like HFOV
• clinical studies have not shown it to be superior
  to conventional ventilation
• more convenient single ventilator for CMV and
  HFV makes initiation and weaning easier

81
High frequency ventilation

• Uses of HFOV/ HFJV/ HFFI
• rescue for severe RDS
• air leak syndromes (pneumothorax, PIE)
• PPHN
• Primary use controversial risk of hypocarbia
  (--gtPVL) higher, and reduction of BPD or airleaks
  seen in some, but not all, studies.

82
Summary

• The practice of the art of mechanical
  ventilation lies in the application of the
  underlying science and physiologic concepts to
  the specific clinical situation
• An individualized flexible approach aimed at
  maintaining adequate gas exchange with the
  minimum of ventilatory support, both in magnitude
  and duration, should optimize the possible outcome

83
Combining IMV and HFV
84
(No Transcript)
85
(No Transcript)
86
(No Transcript)
87
(No Transcript)
88
(No Transcript)