 When the mechanical load of the respiratory system is too large or continues for a long period of time, the diaphragm can develop contractile fatigue1. This fatigue can be short or long term. Short term is also known as high-frequency fatigue that results from the accumulation of inorganic phosphate23, and to a lesser extent intramuscular acidosis4. On the other hand long term fatigue, otherwise known as low-frequency fatigue is consistent with muscle injury5, 6 and can persist for days. Being able to identify what type of diaphragm fatigue is present could help us understand the patients readiness to be extubated. 