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Ventilation and Oxygenation Management 405

TABLE 15.8 Complications of mechanical ventilation

Item Complication
Barotrauma ● pneumothorax
● pneumomediastinum
● pneumopericardium
● pulmonary interstitial emphysema
● subcutaneous emphysema
Volutrauma Shearing stress, endothelial and epithelial cell injury, fluid retention and pulmonary oedema, perivascular and
alveolar haemorrhage, alveolar rupture
Biotrauma Activation of systemic and local inflammatory mechanisms
Ventilation/perfusion Alveolar distension causes compression of the adjacent pulmonary capillaries resulting in dead space ventilation
mismatch
↓ cardiac ouput Resulting in hypotension, ↓ cerebral perfusion pressure (CPP), ↓ renal and hepatic blood flow
↑ right ventricular afterload Due to ↑ intrathoracic pressure
May result in ↓ left ventricular compliance and preload
↓ urine output Due to ↓ glomerular filtration rate, ↑ sodium reabsorption and activation of the renin-angiotensin-aldosterone
system
Fluid retention Due to above renal factors as well as ↑ antidiuretic hormone and ↓ atrial natriuretic peptide
Impaired hepatic function Due to ↑ pressure in the portal vein, ↓ portal venous blood flow, ↓ hepatic vein blood flow
↑ intracranial pressure Due to ↓ cerebral venous outflow
Oxygen toxicity Alterations to lung parenchyma similar to those found in ARDS
Pulmonary emboli and Due to immobility
deep vein thrombosis
Ileus, diarrhoea Due to alterations in gastric motility
Gastrointestinal Gastritis and ulceration may occur due to stress, anxiety and critical illness
haemorrhage
ICU-acquired weakness Neuropathies and myopathies develop in association with critical illness, corticosteroids and neuromuscular
blockade
Psychological issues Delirium, anxiety, depression, agitation and post-traumatic stress disorder may be experienced by critically ill
ventilated patients in the acute and recovery phases

The optimal timing of tracheostomy remains uncertain, ● contemporary ventilators now provide a range of
however, tracheostomy should be considered for patients modes to facilitate mechanical ventilation
experiencing weaning difficulty. ● analysis of ventilator graphics provides clinicians with
The goals of mechanical ventilation are to promote gas the ability to assess patient–ventilator interaction,
exchange, minimise lung injury, reduce work of breathing appropriateness of ventilator settings and lung
and promote patient comfort: function
● semirecumbent positioning at 45 degree elevation
● despite its life-saving potential, mechanical ventila- has been shown to reduce VAP but compliance is
tion carries the risk of serious physical and psychologi- poor
cal complications ● recruitment manoeuvres, HFOV, ECMO and prone
● humidification of dry medical gas is required during positioning are strategies that may facilitate manage-
mechanical ventilation to prevent drying of secretions, ment of refractory hypoxaemia
mucous plugging and airway occlusion ● timely recognition of a patients readiness for weaning
● the pressure required to deliver a volume of gas and extubation is imperative. Strategies such as
into the lungs is determined by elastic and resistive weaning protocols, teams and automatic weaning are
forces all aimed at optimising this process.