Fig. 1From: Efficacy and safety of long-term use of a positive expiratory pressure device in chronic obstructive pulmonary disease patients, a randomized controlled trialA showed a subject in the intervention group using PEP device (PEP = 5cmH2O). B showed a spring linear pressure resistor. The sham PEP device used in the control group was not loaded with a spring linear pressure resistorBack to article page