3. VENTILATORY

SETTING

DR/ MAHMOUD EL NAGGAR

EGYPTIAN BOARD OF NEONATOLOGY

May 1, 2023 3

Ventilator parameters1. Selection of the mode

2. FiO2

3. Inspiratory flow rate or Slope4. Ti (Some ventilators may also have Te, or I : E ratio.) 5. Frequency ( Rate)

6. PEEP

7. PIP

Ventilator parameters

8. Trigger sensitivity

9. Termination sensitivity of

PSV

10. Variable inspiratory

and variable expiratory flow

11. TV & MV in volume targeted

ventilation

12. Ventilator alarm settings

13. Graphics monitoring settings

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1. Which mode?

IMV

A/C SIPPV SIM

V

CPAPPS

SIMV& PS

CMVVG

BIPAP ASV

PCV

VCV

Different ventilatory modes and their characteristics

Weaning by PIP Inspiratory time

Ventilator respiration

rate

Assistance of each breath

Inspiratory trigger

Ventilatory mode

RR& PIP

Fixed

Fixed

Fixed No No IM

V

RR& PIP

Fixed

Fixed

Fixed No Yes SIM

V

PIP Fixed

Fixed

Variable Yes Yes AC/

SIPPV

PIP Fixed

Variable

Variable Yes Yes PS

V

2. Fraction of Inspired OxygenThe simplest and most direct mean to improve oxygenationAdjust FiO2 to maintain adequate oxygenation

Can be adjusted as low as 21% and as high as 100%

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FIO2Oxygen is a drug used to: Relieving hypoxemia pulmonary vasodilator in cases of PPHTN

Inadequate O2 administration will resultant to: Hypoxemia and hypoxia May result in severe neurologic injury

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FIO2 Excessive O2 administration has

been implicated as: ROP BPDTry to maintain: PaO2 (60-80 mmHg) Saturation (PT 90-

95% & FT > 95%)

Hera NICU 2016

Anatomy of Pressure waveform

TiTe

Pres

sure

Begin inspiration

Cycle to expiration

Time

Flow determines rate of rise and reaching peak pressure

Pressure limited =“PIP”

PEEP

∆p

MAP Inflating pressure

Distending pressure

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3 .Flow RateVolume of gas passed / time unit (liter/minute)

Minimum flow of at least 3 times the baby’s minute ventilation is usually required but in practice the operating range can be much higher

Flow rate of 6-10 liter/minute are usually sufficient

Flow rate is an important determinant of the ability of the ventilator to deliver desired levels of PIP, waveform, I : E ratios, and in some cases, respiratory rate.

May 1, 2023 Hera NICU 12

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Slope (80 to 150 ms is recommended)

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Wave forms SINE WAVE SQUARE WAVE

PIPPIPPIP PIP

20

30

10

1 second 1 second 1 second 1 second

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Wave formsSQAURE WAVE SINE WAVE

Adverse effects Advantages Adverse effects Advantages

1. With high flow, the ventilation may be applying higher pressure to normal airways and alveoli

2. Impede venous return if longer Ti is used or I : E ratio is reversed

1. Higher MAP for equivalent PIP

2. Longer time at PIP may open atelectatic areas of lung and improve distribution of ventilation

1. Lower mean airway pressure

1. Smoother increase of pressure

2. More like normal respiratory pattern

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4 .Inspiratory timeUsually adjusted between 0.30- 0.50

secondsDepends on the pulmonary

mechanics: Compliance Resistance Time constant

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Total Cycle Time

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Inspiratory time

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Inspiratory / Expiratory Time RatioI:E ratio should not be less than 1:1.2It should not be reversed

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If inspiratory time is too short Incomplete inspiration

Tidal volume Mean airway pressure

Hypercapnia Hypoxia

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If expiratory time is too short Incomplete expiration

Gas trapping

Complianc Tidal volume Mean airway pressure

Tidal volume Cardiac output

Hypercapnia Hyperoxemia

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Ti & Te

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I / E RatioPROLONGED EXPIRATORY (> 1:3)

NORMAL (1:2-1:3) INVERSE (>1 : 1)

Adverse Effects

Advantages

Adverse Effects

Advantages

Adverse Effects

Advantages

1. Low Ti may decrease tidal volume 2. May have to use higher flow rates, which may not be optimal for distribution of ventilation 3. May ventilate more dead space

1. Useful during weaning, when oxygenation is less of a problem

2. May be more useful in diseases such as MAS, when air trapping is a part of the disease process

1. Insufficient emptying at highest rates

1. Mimics natural breathing pattern

2. May give best ratio at higher rates

1.May have insufficient emptying time and air trapping may result 2. May impede venous return to the heart 3.↑Pulmonary vascular resistance and worsens diseases such as PPHN and CHD 4. Worsens PAL

1. ↑ MAP2. ↑ Pao2

in RDS 3. May enhance alveolar recruitment when atelectasis is present

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Determine minute ventilation ( RR x VT), thus CO2 elimination

Depend on: The infant gestational age The underling disease and resulting pulmonary mechanics

5. Respiratory Rate

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Respiratory Rate

Rate PaCO2

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Ventilatory RateRAPID (≤ 60 breaths /min)

MEDIUM (40-60 breaths/mi

SLOW (≤40 breaths/min)

Adverse Effects

Advantages

Adverse Effects

Advantages

Adverse Effects

Advantages

1. May exceed time constant and produce air trapping 2. May cause inadvertent PEEP 3. May result in change in compliance (frequency dependence of compliance) 4.Inadequate Vt and minute ventilation if only dead space is ventilated

1. Higher PO2 (may be the result of air trapping2.May allow ↑ PIP and Vt 3.Hyperventilation may be useful in PPHN 4. May reduce atelectasis (air trapping)

1. May not provide adequate ventilation in some cases2. ↑ PIP may still be needed to maintain minute ventilation

1. Mimic normal ventilatory rate2. Will effectively treat most neonatal lung diseases 3. Usually does not exceed time constant of lung, so air trapping is unlikely

1. Must increase PIP to

maintain minute ventilation 2. ↑ PIP may cause barotrauma 3. Patient may require paralysis

1.↑ Pao2 with increased MAP 2. Useful in weaning 3. Used with square wave ventilation 4. Needed when I : E ratio is inverted

6. Positive End Expiratory PressureThe positive pressure applied at the end of expiration to prevent lung collapse and maintain stability of the alveoli (FRC)Optimum PEEP is the level below which the lung volume is not maintained and above which the lung volume become over-distended

Can be as low as low as 4 cm H2o& as high as 8 cm H2o, PEEP less than 5 cm in diseased lung is exception.

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Optimum PEEP

PEEPThe benefits of PEEP are: a. Stabilization and recruitment of lung volume. b. Improvement in lung compliance. c. Improvement in ventilation-perfusion matching in the lungs.

Inadvertent PEEP: increase chosen PEEP if expiration time is too short or airway resistance is increased

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Auto-PEEP

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Auto-PEEP

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PEEPHIGH (>8 cm H2O) MEDIUM (4-7 cm H2O) LOW (<4cm H2O)

Adverse Effects

Advantages

Adverse Effects

Advantages

Adverse Effects

Advantages

1. PAL 2. Decreases compliance if lung overdistends 3. May impede venous return to the heart 4. May increase PVR 5. CO2 retention

1. Prevent alveolar collapse in surfactant deficiency states with severely decreased CL 2. Improves distribution of ventilation

1. May overdistend lungs with normal compliance

1.Recruit lung volume with surfactant deficiency states (e.g., RDS2.Stabilizes lung volume once recruited3.Improve V/Q matching

1. May be too low to maintain adequate lung volume 2. CO2 retention from V/ Q mismatch, as alveolar volume is inadequate

1. Used during late phases of weaning 2. Maintenance of lung volume in very premature infants with low FRC 3. Useful in some extremely LBW infants on A/C ventilation

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Gas exchange effects of PEEP

1. An increase in PEEP increases FRC capacity thus improves ventilation-perfusion matching and oxygenation.

2. An increase in PEEP will increase mean airway pressure and thus improve oxygenation.

3. An increase in PEEP will also reduce the pressure gradient during inspiration and thus reduce tidal volume, reduce CO2 elimination, and increase PaCO2.

May 1, 2023 35

PEEP affect PaO2 & PaCO2 in the same

direction.

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7 .Peak Inspiratory PressureThe maximum pressure reached during inspiration

Primary factor to deliver VT in pressure ventilators

Adjust PIP to achieve adequate VT as reflected by chest expansion and adequate breath sounds

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PIP

Gas exchan

ge effects of PIP

1. An increase in PIP will increase tidal volume, increase CO2 elimination, and decrease PaCO2.

2. An increase in PIP will

increase mean airway

pressure and thus improve

oxygenation.

May 1, 2023 38

PIPIf PIP is too low Low VT

HypoxiaIf PIP is too high High VT -Barotraumas and BPD -Hyperinflation and air leak -Impedance of venous returnIf you PIP PaO2 & PaCO2 If you PIP PaO2 & PaCO2

May 1, 2023 39

PIP affects PaCO2 &PaO2 in different directions.

May 1, 2023 40

PIP HIGH (≥20 cm H2O) LOW (≤20 cm H2O)

Adverse effects Advantages Adverse effects Advantages

1. Associated with ↑ PAL, BPD

2. May impede venous return

3. May decrease cardiac output

1. May help re-expand atelectasis

2. ↓ Paco2 3. ↑ Pao24. Decrease

pulmonary vascular resistance

1. Insufficient ventilation; may not control Paco2

2. ↓ Pao2, if too low

3. Generalized atelectasis may occur (may be desirable in some cases of air leaks)

1. Fewer side effects, especially BPD, PAL

2. Normal lung development may proceed more rapidly

Mean Airway Pressure(MAP)It is a measure of the average pressure to which lung are exposed during the respiratory cycle

It is the factor (other than Fio2) that determine oxygenation

MAP( calculated by ventilator)

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Mean airway pressure

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(1) PIP

(2) PEEP

(3) Ti

(4) I : E ratio

(5) wavefor

m

(6) Rate

MAP

May 1, 2023 44

8. Trigger sensitivity

High sensitivity my result in false or auto-triggering.

Increase the sensitivity improve patient ventilator synchronization.

It determine how easy to the patient to trigger the ventilator to deliver a

breath.

Hera NICU 2016

Paw

V•

insp

expPatient or vent ilator initiated

inspiration PSV cycledexpiration

Peak flow

Drop to 15% of peak flow

9. Termination sensitivity of PSV

Set Pinsp

46

10 .Variable inspiratory and variable expiratory flow Continuous expiratory flow can be adjusted independently of the continuous inspiratory flow.

The inspiratory flow is effective during ventilation stroke

While the expiratory flow is effective during the expiratory phase of mandatory ventilation, during spontaneous breathing

May 1, 2023

May 1, 2023 47

11 .Tidal volume & Minute volumeVt Preterm = 4-6 ml/kg

Vt Fullterm = 5-7 ml/kg

Vd = 2-2.5 ml/kg

MV = 200- 480 ml/kg/min

Va = 60- 320 ml/kg/min

Vt = Vd + Va

Minute Ventilation = RR x Vt

Minute alveolar ventilation= RR x Va (Vt- Vd)

May 1, 2023 48

12. Ventilator alarm settings

Some alarm limits are set automatically e.g. airway

pressure, oxygen concentration

Some alarm limits are set manually e.g.

minute ventilation, apnea time, frequency

May 1, 2023 49

13. Graphics monitoring settings

Displaying the mode

Displaying curves : pressure , flow and volume against time.

Displaying measured pressure values: peak, mean and PEEP

Displaying lung values: R, C and TC

Displaying measured volume values: VT, MV, leak and spont.

Displaying trends

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Goals of mechanical ventilationMaintain acceptable gas exchange

with a minimum of: Lung injury Hemodynamic impairment Other adverse events (neurologic injury)Minimize work of breathing.

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During assisted ventilation oxygenation is determined by:

Mean Airway

PressureFiO2

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During assisted ventilation oxygenation is determined by:

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Oxygenation

increases linearly

with increase in MAP

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SoFiO2

PEEP

PIP

Ti

Flow

PaO2

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During assisted ventilation CO2 elimination is determined by:

Minute alveolar

ventilation:

2. Effective Tidal

Volume1.Respirator

y Rate

May 1, 2023 56

During assisted ventilation CO2 elimination is determined by:

1.Respiratory

Rate2. PIP - PEEP

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In all pressure controlled ventilation modes

Tidal Volume supplied depend on:

1- PIP- PEEP2- Lung mechanics3- Respiratory drive of the patient

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Tidal volume

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SORate MV CO2 wash PaCO2

PIP ∆P TV MV CO2 wash PaCO2

PEEP ∆P TV MV CO2 wash PaCO2

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Rate affects PaCO2 mainly.

PIP & PEEP affect PaCO2 & PaO2 together.PIP affects PaCO2 & PaO2 in different directions.

PEEP affect PaCO2 & PaO2 in the same direction.

FIO2, FLOW & Ti affect PaO2 Only.

May 1, 2023 62

Effect of ventilatory setting on blood gasPaO2 PaCO2 Chang

ePIP

PEEP

Rate

I:E ratio

± Flow±

May 1, 2023 63