Signs and symptoms of respiratory failure
| Symptoms |
| Increasing generalised weakness |
| Dysphagia |
| Dysphonia |
| Dyspnoea on exertion and at rest |
| Fatigue |
| Sleepiness |
| Clinical signs |
| Rapid shallow breathing |
| Tachycardia |
| Weak cough |
| Staccato speech |
| Accessory muscle use |
| Abdominal paradox |
| Orthopnoea |
| Weakness of trapezius and neck muscles |
| Single-breath count |
| Cough after swallowing |
| Laboratory data |
| VC ≤15 mL·kg−1, VC ≤1 L or 50% drop from value in stable state, or >20% drop from sitting to supine position |
| Maximum inspiratory pressure ≤30 cmH2O |
| Maximum expiratory pressure ≤40 cmH2O |
| Nocturnal desaturation |
| Pa,CO2 >45 mmHg (6.7 kPa) |
VC: vital capacity; Pa,CO2: arterial carbon dioxide tension.