Prone positioning

Prone positioning is used to treat patients with ARDS to improve gas exchange. Various theories have been proposed to explain improvement, including: reduction in compression atelectasis of dependent lung regions (temporary), reduction in chest wall compliance, increasing intrathoracic pressure and alveolar recruitment, better regional diaphragmatic movement, better V/Q matching, improved secretion clearance, and less alveolar distension leading to better oxygenation.

Indications

Prone positioning may be considered when: PaO2 <8.5, FIO2 0.6, PEEP >10cmH2O despite optimisation of other ventilatory support.

Technique

Positioning the patient takes time and preparation. Four members of staff are required to turn a patient and one person to secure the head and ET tube. The turn itself is a two-stage procedure via the lateral position. The arm on which the patient is to be rolled is tucked under the hip with the other arm laid across the chest. Pillows are placed under the abdomen and chest prior to rotation to the lateral position. If stable, the turn may be completed to prone. Pillows are placed under shoulders and pelvis. The head of bed is raised and one arm is extended at the patient’s side while the other is flexed with head facing opposite way.

Frequency of turns

The response to prone ventilation is difficult to predict. Some patients may have no improvement in gas exchange; others may have a temporary benefit, requiring frequent turns; and others may have difficulty returning to a supine position. For compression atelectasis, it is likely that benefit will last up to 2h before resumption of supine position is required. For other conditions, up to 18h prone position may be required. The head and arms should be repositioned 2-hourly.

Complications

There are problems associated with positioning the patient prone, including; facial oedema, incorrect positioning of limbs leading to nerve palsy, and accidental removal of drains and catheters, pressure necrosis, myositis ossifi cans. These problems are preventable so long as awareness of their potential is understood.

Contraindications

There are two absolute contraindications to prone position: severe head, spinal, or abdominal injury; and severe haemodynamic instability. Relative contraindications include:

• Recent abdominal surgery.

• Large abdomen.

• Pregnancy.

• Spinal instability (though special beds are available for turning affected patients).

• Frequent seizures.

• Multiple trauma.

• Raised intracranial pressure