Appendix 23.I: Management of Ventilation
Initiation of Ventilation Titration of Ventilation Weaning of Ventilation Initiation of Ventilation Once a patient has been intubated and is appropriately sedated, the ventilator is set as follows: Select the level of support: Assist-Control: Pressure Control or Volume Control The ventilator delivers the same breath during every inspiration, whether initiated by the ventilator or by the patient.
Initiation of Ventilation
Once a patient has been intubated and is appropriately sedated, the ventilator is set as follows:
- Select the level of support:
- Assist-Control: Pressure Control or Volume Control
The ventilator delivers the same breath during every inspiration, whether initiated by the ventilator or by the patient. - Synchronised Intermittent Ventilation: Pressure Control or Volume Control
Minimum rate is set and patient may initiate additional supported breaths. - Spontaneous: Invasive Continuous Positive Airway Pressure (CPAP) with Pressure Support
All breaths are initiated by the patient (no set rate) and a pressure support above Positive End Expiratory Pressure (PEEP) is provided.
- Assist-Control: Pressure Control or Volume Control
- Select the level of supplemental oxygen concentration:
- FiO2 at 1 (or 100%).
- Set the trigger:
- Machine Triggered: Respiratory Rate at 12 to 15 breaths per minute.
- Patient Triggered: Sensitivity - Pressure 2cmH2O or Flow 1-2 L/min.
- Set the Control:
- For Volume Control: Set tidal volume at 5 to 8 ml/kg predicted body weight.
- For Pressure Control: Set the pressure above PEEP to 15cmH2O (driving pressure).
- Set the Cycle:
- Inspiratory:Expiratory Ratio at 1:2.
- Flow Cycling: 30% of Maximum Inspiratory Flow.
- Set the Baseline Pressure:
- Positive End Expiratory Pressure: 5cmH2O.
The following should be monitored for the patient receiving invasive mechanical ventilation:
- Arterial blood gas
- Pulse oximetry
- All ventilator parameters
Titration of Ventilation
- Ventilation must constantly be titrated to the patient’s changing needs.
- Incrementally reduce FiO2 by 0.1 (10%) every 10 minutes to 0.4 (40%) keeping oxygen saturation (SpO2) ≥95%. Patients with, or at risk of Acute respiratory distress syndrome (ARDS) are able to tolerate SpO2 ≥88%.
- Adjust settings to target PCO2 of 4.5-6.0 kPa:
- A lower PCO2 will be targeted to temporarily compensate for a metabolic acidosis while the cause is being corrected.
- A PCO2 of 4.2-4.8 kPa may be targeted in brain injured patients.
- A higher PCO2 may be tolerated in patients with, or at risk of, ARDS to minimise the need for harmful ventilator settings (permissive hypercapnia).
- Do not let respiratory acidosis develop such that pH <7.20.
Note:
- The above targets are guidelines and sometimes cannot be met. In these instances, more injurious/aggressive settings may be required for short periods.
- Mechanical ventilation may also be provided non-invasively (NIV) via face mask (specific instructions to be obtained from consultant regarding patient selection and initial settings).
Weaning of Ventilation
- Weaning of ventilation is a continuous process and cannot be separated from titration of ventilation described above: it is simply the reducing limb of ventilation titration.
- Once a patient is stable on mechanical ventilation and requirements are no longer increasing, ongoing attempts must be made at the progressive stepwise reduction of ventilatory support.
- Reduce ventilatory support, beginning in this order:
- FiO2: aim for FiO2 of 0.4 (40%).
- Respiratory Rate (RR):
- Make multiple attempts to reduce the RR for short periods till the patient starts taking spontaneous breaths.
- If the spontaneous rate is >10/min, place the patient on Pressure support/ Continuous positive airway pressure (PS/CPAP).
- Adjust pressure support to maintain tidal volume as needed.
- Observe to see if stable:
- Pressure Support: progressively reduce PS while maintaining tidal volume >6ml/kg and pH >7.3 until PS = 6cmH2O.
- PEEP: Reduce PEEP by 2cm H2O till PEEP = 6cm H2O.
Note: the minimum levels of PS and PEEP able to be set may vary as per the make of the ventilator
- The patient is ready for liberation from the ventilator once the patient requires minimal ventilatory support as described above and is stable with:
- SpO2 >92%, RR between 10 and 30 breaths/min, tidal volume >6ml/kg, and pH >7.3.
- HR and BP within 20% of patient’s normal; Minimal inotropic support; No new arrhythmias.
- No respiratory distress: Alar flaring, Use of accessory muscles, Paradoxical abdominal movement.
- No sweating.
- To assess patient readiness for extubation:
- Assess for adequate level of consciousness, bulbar function, and muscle strength.
- If patient can cough and maintain own airway, then consider extubation.
- T-piece tests are no longer routinely recommended.
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Standard Treatment Guidelines and Essential Medicines List for South Africa Adult Hospital _Chapter 23: Adult Critical Care_NEMLC Medicine Recommendations Review Cycle_ 2020_2023