Neonatal Mechanical Ventilation

Mark C Mammel, MD University of Minnesota Children’s Hospital OF MINNESOT A

Mechanical ventilation

• What we need to do – Support oxygen delivery, CO 2 elimination – Prevent added injury, decrease ongoing injury – Enhance normal development

Mechanical ventilation

• Support oxygen delivery, CO 2 elimination – Headbox O 2 – Cannula O 2 – CPAP ± IMV – Intubation, ventilation

Mechanical ventilation

• Prevent added injury – – – – – Minimize invasive therapy Optimize lung volume Target CO 2 , O 2 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 CO 2 removal • Oxygenation: adequate mean airway pressure • CO 2 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 Inspiration Patient Exhalation

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 Mechanism •Time –Controlled Mechanical Ventilation – NO patient interaction •Pressure –Ventilator senses a drop in pressure with patient effort •Flow –Ventilator senses a drop in flow with patient effort •Chest impedance / Abdominal movement –Ventilator senses respiratory/diaphragm or abdominal muscle movement • Diaphragmatic activity • NAVA- Neurally adjusted ventilatory assist

B. Limit Variable T i T i

Pressure Volume A B A. Pressure limited B. Volume limited

C. Cycle Mechanism What causes the breath to end?

T i T i A. Time – All ventilators B. Flow – Pressure support modes C. Volume – Adult / pediatric ventilators

Pressure Flow Volume

T i

A B C

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 H 2 O most common) – SiPAP: special type of CPAP. Uses 2 levels, usually 2-4 cm H 2 O different – HFNC • Nasal cannula interface • 2-4 L/min flow – Monitoring • CPAP: airway pressure displayed and alarmed • HFNC: none

Early CPAP  Columbia Presbyterian 500-1500 gm Infants: Variation in CLD * % * * * * p<0.0001

Van Marter et al.

Pediatrics

2000;105:1194-1201

• • • Intermittent mandatory ventilation: IMV / SIMV Goal: – Support EELV and improve V e 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 cmH cmH 2 O 2 O). Pressure then adjust based on volume. Set PEEP 5-7 Time- set T i 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 V spontaneously breathing infant requiring intubation e in apneic or – 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 cmH 2 O). Pressure then adjust based on volume. – PEEP: 5-7 cmH 2 O Time- set T with rate i maximum at 0.3 – 0.5 sec based on pt size. Actual T i varies with lung mechanics. T e varies – 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 (V e ): P a CO 2

V e • = RR x V V t t changes with changing lung mechanics • Tools to change: PIP, PEEP, T i , T e – –

Oxygenation: P a O 2 , S a O 2

Mean airway pressure (P aw ) • Oxygenation varies with lung volume, injury • Tools to change: PIP, PEEP, T i , T e

Conventional Ventilation

• Variables- What does what?

– –

Minute ventilation (V e ): P a CO 2

V e • = RR x V V t t changes with

changing lung mech

anics

• Tools to change:

PIP, PEEP, T i , T e

Assessment of V t : PAC (no volume target)

Assessment of V t : PAC, improved C

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

Conventional Ventilation

• Boros SJ, et al. Pediatrics 74;487:1984  Mammel MC, et al. Clin Chest Med 1996;17:603

Conventional Ventilation

• Variables- What does what?

– –

Oxygenation: P a O 2 , S a O 2

Mean airway pressure (P aw ) • Oxygenation varies with

lung volume

, injury • Tools to change:

PIP, PEEP, T i , T e

• 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

Lung Volume

P opt P cl P op P max Pressure

Lung Volume • Optimize lung volume – S a O 2 as volume surrogate Tingay DG et al. Am J Resp Crit Care Med 2006;173:414

Assessment of P aw – T i adjustment

Assessment of P aw – PEEP adjustment

Assessment of P aw – PIP adjustment

Assessment of P aw – Rate adjustment

T i RR PIP Neonatal Mechanical Ventilation: Ventilator setup PEEP IMV 0.2-0.5 sec (flow signal) Set based on condition Set based on condition (Vt) 4-10 based on O2 needs, condition 4-6 mL/kg SIMV 0.2-0.5 sec (flow signal) Set based on condition Set based on condition (Vt) 4-10 based on O2 needs, condition 4-6 mL/kg A/C PSV 0.2-0.5 sec (flow signal) Set limit- 0.3 0.5 sec Set lower limit for apnea Set lower limit for apnea Set limit; based on Vt Set limit; based on Vt 4-10 based on O2 needs, condition 4-6 mL/kg 4-10 based on O2 needs, condition 4-6 mL/kg V t Flow F i O 2 3-15 L/min 3-15 L/min 3-15 L/min 3-15 L/min Adjust 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?