A) Forced vital capacity (FVC) of less than 20 mL/kg
B) Maximum inspiratory pressure (MIP) less than 20 cmH2O
C) Inability to stand
D) Inability to lift the elbows
E) Increased Liver enzymes
The objective of the above question is to bring into light the two less known predictors of impending respiratory failure. Clinicians often confused numbers between forced vital capacity (FVC), maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP).
The rule is 20-30-40
- FVC less than 20 mL/kg
- MIP less than 30 cmH2O
- MEP less than 40 cmH2O
(Tip to remember: You are always Forced to Inspire before Expire)
Paying attention to increased liver enzymes may also help. Other easy to notice clinical signs are the inability to cough, stand, lift the elbows or the head.
1. Lawn ND, Fletcher DD, Henderson RD, et al. Anticipating mechanical ventilation in Guillain-Barré syndrome. Arch Neurol 2001; 58:893.
2. Sharshar T, Chevret S, Bourdain F, et al. Early predictors of mechanical ventilation in Guillain-Barré syndrome. Crit Care Med 2003; 31:278.