Change in Venous Oxygen Levels During Aerobic Forearm Exercise in a Patient with Mitochondrial Myopathy

 

Patient selection: unexplained exercise intolerance

 

Test: dynamometer for measuring maximum voluntary contraction (MVC) during isometric hand grip exercise

 

In normal patients the PO2 of venous blood drawn from the antecubital fossa will drop during aerobic forearm exercise.

 

In a patient with mitochondrial myopathy the PO2 of venous blood drawn from the antecubital fossa rises during aerobic forearm exercise.

 

change in venous oxygen levels in mm Hg =

= (venous oxygen levels during exercise) - (venous oxygen levels at rest or during recovery)

Condition	Change in Venous Oxygen
normal	negative
mitochondrial myopathy	positive

 

A venous PO2 >30 mm Hg at 50% of maximal voluntary contraction had a sensitivity of 77% and specificity of 100% for detecting mitochondrial myopathy. A venous PO2 < 21 mm Hg at 50% MVC is unlikely with a mitochrondrial myopathy.