Neonatal Mechanical Ventilation Mark C Mammel, MD OF MINNESOT A University of Minnesota Childrens Hospital.

Neonatal Mechanical Ventilation

Mark C Mammel, MD

OF MINNESOTAUniversity of Minnesota

Children’s Hospital

Mechanical ventilation

• What we need to do– Support oxygen delivery, CO2 elimination

– Prevent added injury, decrease ongoing injury

– Enhance normal development

Mechanical ventilation

• Support oxygen delivery, CO2 elimination

– Headbox O2

– Cannula O2

– CPAP ± IMV– Intubation, ventilation

Mechanical ventilation

• Prevent added injury– Minimize invasive therapy – Optimize lung volume– Target CO2, O2

– Use appropriate adjuncts– Manage fluids and nutrition

Mechanical ventilation

• Enhance normal development– Manage fluids and nutrition– Encourage patient-driven support– Maintain pulmonary toilet- carefully

Support devices

Mechanical ventilation

• Key concepts:– Maintain adequate lung volume

• Inspiration: tidal volume• Expiration: End-expiratory lung volume

– Support oxygenation and CO2 removal• Oxygenation: adequate mean airway pressure• CO2 removal: adequate minute ventilation

Mechanical ventilation

• Key concepts:– Optimize lung mechanical function

• Compliance: ∆V/∆P• Resistance: ∆Flow/∆P• Time constant: C x R

Boros SJ et al:

J Pediatr1977; 91:794

Mechanical ventilation: How does it work?

Patient

Exhalation

Patient

Inspiration

Mechanical Ventilation:Mode classification

A. Trigger mechanism• What causes the breath to

begin?

B. Limit variable• What regulates gas flow

during the breath?

C. Cycle mechanism• What causes the breath to

end?A

B C

A. Inspiratory Trigger MechanismA. Inspiratory Trigger Mechanism

•TimeTime–Controlled Controlled MeMechanicalchanical Ventilation – NO patient interactionVentilation – NO patient interaction

•PressurePressure–Ventilator senses a drop in pressure with patient effortVentilator senses a drop in pressure with patient effort

•FlowFlow–Ventilator senses a drop in flow with patient effortVentilator senses a drop in flow with patient effort

•Chest impedance / Abdominal movementChest impedance / Abdominal movement–Ventilator senses respiratory/diaphragm or abdominal Ventilator senses respiratory/diaphragm or abdominal muscle movement muscle movement

•Diaphragmatic activityDiaphragmatic activity•NAVA- Neurally adjusted ventilatory assistNAVA- Neurally adjusted ventilatory assist

B. Limit Variable

Pressure

Volume

A B

B. Volume limited

A. Pressure limited

Ti Ti

C. Cycle MechanismWhat causes the breath to end?

A. Time– All ventilators

B. Flow– Pressure support modes

C. Volume– Adult / pediatric ventilators

Pressure

Flow

A B

Ti Ti

Volume

C

Ti

Basic waveforms

Time cycle- fixed Ti

Flow cycle- variable Ti with limit

Mechanical ventilation:Which vent?

• Conventional Dräger Babylog 8000 Avea Servo i

• High frequency SensorMedics oscillator Bunnell HFJV

Conventional Ventilation

• Modes:– CPAP

• +/- Pressure support (PSV)

– IMV/SIMV• +/- Pressure support (PSV), volume targeting

– Assist/control (PAC)• +/- volume targeting

Continuous positive airway pressure: CPAP

• Goal:– Support EELV in spontaneously breathing infant

(optimize lung mechanics)

• Delivery:– NeoPuff, other dedicated CPAP devices– HFNC– Using mechanical ventilator– May be done noninvasively or via ET tube (HFNC in

extubated patients only)• Patients:

– Newborn infants ≥26 wks with early distress– Infants in NICU with new distress or apnea– Extubated infants

Continuous positive airway pressure: CPAP

• Setup:– NeoPuff, other dedicated CPAP devices:

• Nasal prong interface• Set PEEP (4-6 cm H2O most common)

– SiPAP: special type of CPAP. Uses 2 levels, usually 2-4 cm H2O different

– HFNC• Nasal cannula interface• 2-4 L/min flow

– Monitoring• CPAP: airway pressure displayed and alarmed• HFNC: none

Early CPAP

Columbia Presbyterian500-1500 gm Infants: Variation in CLD500-1500 gm Infants: Variation in CLD

*

*

**

*p<0.0001

Van Marter et al. Van Marter et al. PediatricsPediatrics 2000;105:1194-1201 2000;105:1194-1201

%

Intermittent mandatory ventilation: IMV/ SIMV

• Goal:– Support EELV and improve Ve in spontaneously

breathing infant requiring intubation– Eliminate breath-breath volume variation,

cerebral blood flow abnormalities, allow patient control via synchronization of SOME breaths

• Delivery:– Using mechanical ventilator– May be done noninvasively or via ET tube

• Patients:– Newborn infants requiring intubation– Extubated infants with persistent distress

Intermittent Mandatory Ventilation: IMV/ SIMV

• Setup:– ET tube interface– Variables:

• Rate- range 15-60 bpm; always synchronized• Volume- target volume 4-7 mL/kg• Pressure- Set peak pressure limit (usually 30 cmH2O).

Pressure then adjust based on volume. Set PEEP 5-7 cmH2O

• Time- set Ti at 0.3 – 0.5 sec based on pt size

– Monitoring• Dynamic. Multiple alarm settings. All measured and

calculated parameters may be displayed and trended

IMV- unsynchronized

Impact of synchronization

Assist/control: PAC• Goal:

– Support EELV and improve Ve in apneic or spontaneously breathing infant requiring intubation

– Eliminate breath-breath volume variation, cerebral blood flow abnormalities, allow patient control via synchronization of ALL breaths

• Delivery:– Using mechanical ventilator– Done via ET tube

• Patients:– Newborn infants requiring intubation

Assist/control: PAC• Setup:

– ET tube interface– Variables:

• Rate- set minimum acceptable rate, 40-60 bpm; actual rate depends on patient effort

• Volume- target volume 4-7 mL/kg• Pressure-

– Peak pressure: Set limit (usually 30 cmH2O). Pressure then adjust based on volume.

– PEEP: 5-7 cmH2O• Time- set Ti maximum at 0.3 – 0.5 sec based on pt

size. Actual Ti varies with lung mechanics. Te varies with rate

– Monitoring• Dynamic. Multiple alarm settings. All measured and

calculated parameters may be displayed and trended

Assist/control- full synchronization

Conventional Ventilation

• Variables- What does what?– Minute ventilation (Ve): PaCO2

– Ve = RR x Vt • Vt changes with changing lung mechanics• Tools to change: PIP, PEEP, Ti, Te

– Oxygenation: PaO2, SaO2

– Mean airway pressure (Paw)• Oxygenation varies with lung volume, injury• Tools to change: PIP, PEEP, Ti, Te

Conventional Ventilation

• Variables- What does what?– Minute ventilation (Ve): PaCO2

– Ve = RR x Vt • Vt changes with changing lung mechanics• Tools to change: PIP, PEEP, Ti, Te

Assessment of Vt: PAC (no volume target)

Assessment of Vt: PAC, improved C

Assessment of Vt: PAC + V, imp C- no limit

• Boros SJ, et al. Pediatrics 74;487:1984

Conventional VentilationConventional Ventilation

Mammel MC, et al. Clin Chest Med 1996;17:603

Mammel MC, et al. Clin Chest Med 1996;17:603

Conventional Ventilation

• Variables- What does what?– Oxygenation: PaO2, SaO2

– Mean airway pressure (Paw)• Oxygenation varies with lung volume, injury• Tools to change: PIP, PEEP, Ti, Te

Lung Volume

• Optimize lung volume

– Define opening pressure, closing pressure, optimal pressure: dependent on estimation of lung volume

– Problems: no useful bedside technology to measure either absolute or change in lung volume

Pmax

Popt

Pcl Pop Pressure

Volu

me

Lung Volume

• Optimize lung volume– SaO2 as volume

surrogate

Tingay DG et al. Am J Resp Crit Care Med 2006;173:414

Assessment of Paw – Ti adjustment

Assessment of Paw – PEEP adjustment

Assessment of Paw – PIP adjustment

Assessment of Paw – Rate adjustment

Neonatal Mechanical Ventilation:Ventilator setup

IMV SIMV A/C PSV

Ti0.2-0.5 sec

(flow signal)

0.2-0.5 sec

(flow signal)

0.2-0.5 sec

(flow signal)

Set limit- 0.3-0.5 sec

RR Set based on condition

Set based on condition

Set lower limit for apnea

Set lower limit for apnea

PIP Set based on condition (Vt)

Set based on condition (Vt)

Set limit; based on Vt

Set limit; based on Vt

PEEP 4-10 based on O2 needs, condition

4-10 based on O2 needs, condition

4-10 based on O2 needs, condition

4-10 based on O2 needs, condition

Vt4-6 mL/kg 4-6 mL/kg 4-6 mL/kg 4-6 mL/kg

Flow 3-15 L/min 3-15 L/min 3-15 L/min 3-15 L/min

FiO2Adjust based on O2 sats

Adjust based on O2 sats

Adjust based on O2 sats

Adjust based on O2 sats

Mechanical ventilation

• What we know: general– Support affects pulmonary, neurologic

outcomes• Greater impact at lower GA• VILI is real• Less is usually more

Mechanical ventilation

• What we need to know– Who needs support?– Who needs what support?

• Risk/benefit for various modalities

– When (how) do you wean/stop support?