What Can We Do For The Patient?

Dr Tristan GR DyerRCSEd Fellow in Pre-hospital Emergency Medicine

Aims

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

How Can We Ventilate The Patient?

Let the patient do it themselves! Manually Mechanically

Self-Ventilation

Deliver oxygen Work with the patient to optimise

their position Analgesia Therapeutic interventions (e.g.

drugs)

Indications for Ventilatory Support

Failure to Ventilate Failure to Oxygenate

Manual Ventilation

Manual Ventilation

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.

Predictors for Difficult Manual Ventilation

Mechanical Ventilation

How does it work?

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.

Pre-hospital Mechanical Ventilation

Patient has to be anaesthetised or crash intubation.

BUT Delivers 100% FiO2

Accurate tidal volumes. Accurate respiratory rate. Alarms to warn of emergencies

developing. Allows inline capnography. Frees up the operator.

Modes of Ventilation

Controlled Mechanical Ventilation Assist-Control Ventilation Intermittent Mandatory Ventilation Pressure Support Ventilation Pressure Control Ventilation Inverse I:E Ratio Ventilation

Controlled Mechanical VentilationCMV

Patient Factors To Optimise Ventilation

Ensure adequate sedation and paralysis

Patient position Clear secretions Treat underlying pathology

Basic Settings

Respiratory Rate 10-12 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 H2O.

Lower mean airway pressures (<20-30 cm H2O) can help preserve cardiac output and V/Q relationships.

May build TV up to 10ml/Kg.

Advanced Ventilators

Allow for...

Positive End-Expiratory Pressure(PEEP)

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.

Pulmonary Effects of PEEP

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

Adverse Pulmonary Effects

Worse at levels >20 cm H20. Barotrauma Worse with underlying lung disease,

high rate of breaths, large tidal volumes and young age.

Adverse Non-Pulmonary Effects

Transmission of elevated airway pressure to the contents of the chest.

Reduced cardiac output. Elevated central venous pressure.

PEEP Settings

Starting PEEP 5-8 cm H2O used to compensate for the reduced FRC in anaesthetised patients.

Add in increments of 5 cm H2O up to 15 cm H2O.

Aim to improve oxygen saturations.

Lung Protective Strategy

Low Tidal Volume Low Airway Pressure Modest PEEP

Difficult Patient Groups

Trauma

Asthmatics

Pregnant

Bariatric

Elderly

Children

The Future

Arterial Lines

iSTAT

Portable Ultrasound

Inotropes

Any Questions?

Summary

Discussed means of ventilation Focused on mechanical ventilation Talked about difficult patient groups Looked at future adjuncts that may

help with ventilatory support