NICE QS193 recommends that preterm babies having invasive ventilation are given volume targeted ventilation in combination with synchronised ventilation
DEFINITION
A form of synchronous ventilation in which baby triggers/initiates the breath while ventilator does the work of breathing. In other words, rate of ventilation is determined by baby while pressures are determined by operator via ventilator
SETTING UP TRIGGER VENTILATION
- Set humidifier temperature at 39°C (negative 2) to achieve airway temperature of 37°C
Set up Babylog® (Drager)
- Flow 6–10 L/min
- Select SIPPV mode
- Select highest trigger sensitivity (1: bar is all unshaded)
- Select Tinsp (inspiratory time) between 0.3–0.4 sec
- Adjust Texp (expiratory time) to achieve back-up rate of 35–40/min
- Peak inspiratory pressure (PIP) 16–18 cm H2O
- Peak end expiratory pressure (PEEP) 5 cm H2O
- FiO2 to achieve target SpO2 for gestation (see Oxygen saturation targets guideline)
Set up SLE 5000/6000
- Select patient triggered ventilation (PTV) mode
- Select highest trigger sensitivity (0.2 L/min for ≤28 weeks’ gestation, 0.4–0.6 L/min for >28 weeks’ gestation). Look at baby to confirm triggering adequately by observing baby generated breaths are triggering ventilator support
- Select Tinsp for back-up breaths between 0.3–0.4 sec
- Set back-up rate of 35–40/min
- PIP 16–18 cm H2O
- PEEP 5 cm H2O
- FiO2 to achieve target SpO2 for gestation (see Oxygen saturation targets guideline)
- Software allows compensation for a leak of 10–60%
- Observe tidal volume (Vt) settings to confirm between 4–6 mL/kg
Baby
- If gestation <34 weeks, consider loading baby with IV caffeine citrate (20 mg/kg)
- Discontinue sedation
INITIATING TRIGGER VENTILATION
- Once baby connected to ventilator:
- check SpO2 (see Oxygen saturation targets guideline) and adjust FiO2 accordingly
- check baby’s chest moving adequately, and measured Vt. Chest expansion should be just visible, and Vt should be between 4–6 mL/kg. If not, adjust PIP/PEEP to maintain adequate oxygenation and ventilation
- check ventilator triggering in synchrony with baby. Assess by listening to ventilator while watching baby’s respiratory effort
Most likely cause of baby ‘fighting’ ventilator is ASYNCHRONY (see Management of asynchrony)
SUBSEQUENT ADJUSTMENTS ON SIPPV
- Check blood gas within 30 min of initiation of SIPPV
- Aim for:
- PaO2: 6–10 kPa or target appropriate SpO2 level
- PaCO2: 4.5–8.5 kPa day 1–3, 4.5–10 kPa day 4 onwards
- pH >7.25
To improve oxygenation
- Increase FiO2
- Rule out pneumothorax
- Increase PIP and/or PEEP
- Increase Tinsp (not more than 0.4 sec)
To decrease PaCO2
- Rule out pneumothorax
- Increase PIP
- Check if baby triggering adequately. If not, try shortening Tinsp, or increasing back-up rate
Low PaCO2
- Decrease PIP
- Decrease back-up rate if >35/min (if baby not breathing above this rate)
- In a vigorous hypocapnic baby, transfer to synchronised intermittent mandatory ventilation (SIMV) at a rate of at least 20/min
GENERAL SUPPORT
- Monitor SpO2 continuously
- Check arterial blood gases at least 4–6 hrly depending on stage of disease
- In babies successfully ventilated in SIPPV mode, sedation is unnecessary
- Remember, most common cause of baby fighting ventilator is ASYNCHRONY. Always carry out checks and adjustments (see Management of asynchrony)
- If baby still ‛fights’ ventilator, consider morphine bolus (50–100 microgram/kg)
- If baby continues to ‛fight’ ventilator, use continuous sedation and change to other conventional ventilation (SIMV) mode (see Ventilation: conventional guideline)
Do not use muscle relaxants unless, despite carrying out above checks, baby cannot be ventilated.
If muscle relaxants necessary, revert to conventional ventilation (see Ventilation: conventional guideline)
If muscle relaxants necessary, revert to conventional ventilation (see Ventilation: conventional guideline)
NURSING OBSERVATIONS
While baby on SIPPV, hourly observations
- Back-up rate set
- Baby’s own respiratory rate
- Vt (in mL)
- Minute ventilation [MV (in 1/min)]
If alarm goes off, check
- Synchrony between baby and ventilator
- Excessive water droplets in ventilator tubing
- Flow graph for evidence of blocked tube or excessive Tinsp
- Disconnection
MANAGEMENT OF ASYNCHRONY
Checklist
- Is endotracheal tube (ETT) patent (look at flow graph and Vt)
- Is Tinsp too long? (is baby exhaling against ventilator?), if so shorten Tinsp to 0.3 sec
- Is back-up rate too high? If so, consider dropping to 30–35 breaths/min
- Is there water condensation in ventilator tubing?
- If all above fails, consider morphine bolus (100 microgram/kg) over 3–5 min
- If baby still continues to ‛fight’ ventilator, use continuous sedation and revert to SIMV
AUTOCYCLING (FALSE TRIGGERING)
- False triggering occurs when ventilator delivers a mechanical breath artefactually when baby not actually initiating a spontaneous respiration
- Usually results from presence of water droplets in ventilatory circuit, or an excessive ETT leak
- If baby’s trigger rate appears to be in excess of 80/min, ensure this is actual rate by observing baby’s own respiratory movements. If not:
- check ventilatory circuit for excessive water condensation and empty if necessary
- decrease trigger sensitivity by increasing trigger threshold e.g. from 0.4 to 0.6 L/min
- look for amount of ETT leak on Babylog display. If in excess of 50%, consider changing to slightly wider ETT
WEANING FROM SIPPV
- Once baby stable (triggering above set rate, saturating in FiO2 <0.3), wean by:
- decreasing PIP by 1–2 cm H2O each time (in SIPPV/PTV mode, weaning rate in a baby who is already triggering above it is useless)
- check baby breathing regularly and effortlessly (no chest recessions), and blood gases and oximetry are acceptable
- once PIP between 14–16 cm H2O (depending on size of baby), consider extubation
- assess need for nasal CPAP/high-flow by checking for chest recessions, spontaneous minute ventilation, and regularity of breathing
- During weaning PaCO2 can rise above 7 kPa and Vt may fall below 4 mL/kg
- provided baby triggering well, is not visibly tired and pH >7.25, no action required
- if poor triggering, visibly tired or abnormal pH, increase PIP, and later back-up rate
Date updated: 2024-02-08