Fig. 1. Likely relationship between risk of respiratory complications and train-of-four (TOF) ratio at the adductor pollicis. The exact shape and position of the curve for normal patients (blue ) depend on the definition of “complication,” and are not known for certain. Some conditions are likely to shift (arrow ) the curve to the right (red ), as might occur with the examples given. There are no hard data on the specific conditions and the extent of the shift.