DEFINITION
In volume-targeted ventilation (VTV) gas delivery is targeted to deliver a pre-set tidal volume. Inspiratory pressure varies with each breath, depending on resistance and underlying lung compliance. The ventilator measures expired tidal volume (Vte) and calculates the pressure required to deliver this volume for the next breath. Available as volume guarantee (VG) on Draeger Babylog®, targeted tidal volume (TTV) on SLE 5000 and VTV on SLE 600
Benefits
- Compared with pressure-controlled ventilation, VTV can reduce:
- mortality
- bronchopulmonary dysplasia
- pneumothorax
- hypocarbia
- severe intraventricular haemorrhage and periventricular leukomalacia
INDICATION
- Primarily used in preterm babies with surfactant-deficient lung disease requiring ventilation
- May be useful in other situations requiring ventilation
CONTRAINDICATION
- ETT leak >50%
- Caution to be used in situations such as pneumothorax, tracheo-oesophageal/bronchopleural fistula; leak may be increased and affect ventilation
TIDAL VOLUMES TO USE
- Vte used as less influenced by ETT leaks
- Vt 4–6 mL/kg
- 5 mL/kg reasonable starting volume
- Acute respiratory distress syndrome (RDS) 4–6 mL/kg
- baby <750 g: 5-6 mL/kg (minimum starting volume 3 mL if 6 mL/kg is <3 mL)
- baby 750–999 g: 4.5–5 mL/kg
- baby ≥1000 g: 4–4.5 mL/kg
- Chronic lung disease: 5–8 mL/kg
- Avoid Vte >8 mL/kg (associated with volutrauma)
- Avoid Vte <3.5 mL/kg (associated with atelectotrauma)
- Change Vte in 0.5 mL/kg increments
MODE
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VG/TTV combined with SIMV, SIPPV, assist control (PTV) or pressure-support ventilation (PSV)
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VG also available for PC-CMV and HFO modes on Draeger VN-500 ventilator
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In SIMV mode, set rate of ≥40/min (baby breaths are unsupported)
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PSV has additional advantage of synchronising inspiration termination
PEAK PRESSURES
- Start PIP limit (Pmax) of ~25–30 cm H2O
- Once baby stable and gases satisfactory adjust Pmax to 5–6 cm H2O above average PIP needed to deliver set tidal volume
- usually set ≤30 cm H2O in preterm babies
- If PIP progressively increases or is persistently high, or if set Vt not delivered, reassess baby
- PEEP set at 4–6 cm H2O
VENTILATOR RATE
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In baby with poor respiratory drive, use rates of 50–60 bpm
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Lower back-up rates of 30–40 bpm can be used with good respiratory drive
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Use Tinsp (inspiratory time) of 0.3–0.4 sec; in PSV mode, set maximum Tinsp at 0.5–0.6 sec – actual Tinsp is adjusted by the ventilator
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Set flow trigger sensitivity at 0.2–0.4 L/min
WEANING
- Pressure weans automatically as lung compliance improves
- Avoid tidal volumes <3.5 mL/kg as increases work of breathing in small babies
- In SIMV, rate reduced to 40 breaths/min. VG/TTV is unhelpful with SIMV rates <40/min as baby breaths are unsupported. Attempt extubation when:
- FiO2 <0.3
- MAP falls consistently <8 cm H2O
- baby has good respiratory drive and satisfactory gases
TROUBLESHOOTING AND PREVENTING PROBLEMS
High CO2
- Review baby
- Is set Vte being delivered?
- Is chest expansion adequate?
- Has leak increased? Change baby’s position before increasing Pmax
- If ETT displaced/obstructed, or pneumothorax suspected, perform chest X-ray
Low CO2
- Decrease Vte by 0.5 mL/kg but maintain ≥4 mL/kg (≥2.5 mL total volume)
- Change to SIMV
- Lower trigger sensitivity
- Check for water in circuit (auto-triggering)
- Decrease rate by 5–10 bpm (in SIMV mode only)
- Increase PEEP (maximum 8 cm H2O)
Low SpO2
- Review baby
- Exclude air leaks
- Worsening RDS: may require additional surfactant dose
- Evidence of PPHN (see Persistent pulmonary hypertension of the newborn (PPHN) guideline)
- Increase FiO2
- If Vte not delivered, increase Pmax
- Baby may benefit from change to high frequency (see Ventilation: high frequency oscillatory ventilation (HFOV) guideline)
- Exclude congenital heart disease
Low Vte alarm
- ETT leak >50%
- Pneumothorax
- Poor compliance/high resistance: increase Pmax
Baby persistently tachypnoeic
- Increase Vte by 0.5–1.0 mL/kg even if gases normal
- Review sedation