<qa>  What is the distance of the 6-min walk?2. A 6-min walk oximetry tests of ambulatory COPD patients. Patients should be referred to the pulmonary lab for clinical purposes or should be under the rehabilitation procedures. The measurements are taken using Oxitone oximeter and standard fingertip pulse oximeter in accordance with the standard protocol. Measurements are taken continuously prior to the test, during the test and 1 minute after the test, at rest. The distance of the 6-min walk will be recorded. Rehabilitation subjects procedures. The measurements are taken using Oxitone Oximeter and standard fingertip pulse oximeter in accordance with the standard protocol. Measurements are taken continuously prior to the test. The distance of the 6-min walk will be recorded. 