Table 3

Factors that can lead to weaning failure due to the imbalance between ventilatory needs and respiratory capacity

Factors that increase the load
Increased resistive loads
Increased chest wall elastic loads
Increased lung elastic loads

Bronchospasm
Pleural effusion
Hyperinflation (intrinsic positive end-expiratory pressure)
Airway edema, secretions
Pneumothorax
Alveolar oedema
Upper airway obstruction
Flail chest
Infection
Obstructive sleep apnea
Obesity
Atelectasis
Endotracheal tube kinking
Ascites
Interstitial inflammation and/or oedema
Secretions encrustation
Abdominal distension

Ventilatory circuit resistance



Factors that result in decreased neuromuscular competence
Decreased drive
Muscle weakness
Impaired neuromuscular transmission

Drug overdose
Electrolyte derangement
Critical illness polyneuropathy
Brain-stem lesion
Malnutrition
Neuromuscular blockers
Sleep deprivation
Myopathy
Aminoglycosides
Hypothyroidism
Hyperinflation
Guillain-Barré syndrome
Starvation/malnutrition
Drugs, corticosteroids
Mysthenia gravis
Metabolic alkalosis
Sepsis
Phrenic nerve injury
Myotonic dystrophy

Spinal cord lesion

*Positive test result is a value of rapid shallowbreathing index (f/VT) lower than 105 or 100; negative testresult is a value of f/VT higher than 105 or 100.

Alía and Esteban Critical Care 2000 4:72   doi:10.1186/cc660