Dr Tristan GR Dyer RCSEd Fellow in Pre-hospital Emergency Medicine
To discuss methods of ventilation To discuss mechanical ventilation To introduce some difficult patient groups that make ventilation more challenging To look at future tools to aid ventilatory strategies
Let the patient do it themselves! Manually Mechanically
Deliver oxygen Work with the patient to optimise their position Analgesia Therapeutic interventions (e.g. drugs)
Failure to Ventilate Failure to Oxygenate
Can be used with basic and advanced airway adjuncts. BUT Ties operator up! Inaccurate tidal volumes. Tendency for operator to hyperventilate (the patient!) May not be able to effectively ventilate the patient. Risk of aspiration.
Intermittent application of positive pressure to the upper airway. Inspiration – gas flows into alveoli until the alveolar pressure equals the upper airway pressure. Expiration – positive airway pressure is removed/decreased so the gradient reverses and gas flows out of the alveoli.
Patient has to be anaesthetised or crash intubation. BUT Delivers 100% FiO 2 Accurate tidal volumes. Accurate respiratory rate. Alarms to warn of emergencies developing. Allows inline capnography. Frees up the operator.
Controlled Mechanical Ventilation Assist-Control Ventilation Intermittent Mandatory Ventilation Pressure Support Ventilation Pressure Control Ventilation Inverse I:E Ratio Ventilation
Ensure adequate sedation and paralysis Patient position Clear secretions Treat underlying pathology
Respiratory Rate breaths/min. Tidal Volume 6-8 ml/Kg. Aim to balance adequate ventilation with risk of pulmonary barotrauma and volutrauma at inflation pressures of >35-40 cm H 2 O. Lower mean airway pressures (<20-30 cm H 2 O) can help preserve cardiac output and V/Q relationships. May build TV up to 10ml/Kg.
Used to improve a symptomatic decrease in the Functional Residual Capacity that causes hypoxaemia. Provided by an extra valve applied to the breathing circuit or within the ventilator.
In patients with a reduced lung volume, PEEP stabilizes and expands partially collapsed alveoli. This... Increases FRC and tidal ventilation Improves lung compliance Corrects V/Q abnormalities
Worse at levels >20 cm H 2 0. Barotrauma Worse with underlying lung disease, high rate of breaths, large tidal volumes and young age.
Transmission of elevated airway pressure to the contents of the chest. Reduced cardiac output. Elevated central venous pressure.
Starting PEEP 5-8 cm H 2 O used to compensate for the reduced FRC in anaesthetised patients. Add in increments of 5 cm H 2 O up to 15 cm H 2 O. Aim to improve oxygen saturations.
Low Tidal Volume Low Airway Pressure Modest PEEP
Discussed means of ventilation Focused on mechanical ventilation Talked about difficult patient groups Looked at future adjuncts that may help with ventilatory support