Neonatal Mechanical Ventilation Mark C Mammel, MD OF MINNESOTA University 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 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? B C A

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

C. Cycle Mechanism What causes the breath to end? Ti Ti Ti A. Time All ventilators B. Flow Pressure support modes C. Volume Adult / pediatric ventilators Pressure Flow Volume 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 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 Presbyterian * * *p<0.0001 * * 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 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: Delivery: Patients: 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: Monitoring 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

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

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: PaO2, SaO2 Mean airway pressure (Paw) Oxygenation varies with lung volume, injury Tools to change: PIP, PEEP, Ti, Te

Lung Volume Optimize lung volume Pmax Popt Volume Pcl Pop Pressure 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 Volume Pcl Pop Pressure

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 Ti 0.2-0.5 sec (flow signal) Set limit- 0.3-0.5 sec RR Set based on condition Set lower limit for apnea PIP Set based on condition (Vt) Set limit; based on Vt PEEP 4-10 based on O2 needs, condition Vt 4-6 mL/kg Flow 3-15 L/min FiO2 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?