Inspiratory Flow Limitation: Comparison of the C-Flex System versus Conventional Therapy -- A Pilot Study.

Question of the study Compliance with nasal continuous positive airway pressure (nCPAP) treatment may be reduced due to difficulties when exhaling against a positive pressure. A recently introduced CPAP system therefore lowers the expiratory pressure proportional to the patient's airflow. To evaluate the theoretical concern that this might induce flow limitations during inspiration, we measured the occurrence of flow limitation during sleep. Patients and methods Eight subjects with treated obstructive sleep apnoea were studied with polysomnography including respiratory flow and oesophageal pressure measurement. Conventional CPAP and three settings of the new system were applied in a randomised order during both NREM and REM sleep. Two approaches for measuring inspiratory flow limitation were used: oesophageal pressure and respiratory resistance. Results Using the oesophageal pressure criterion, 3.5 % of breaths during CPAP mode were flow limited as compared to 1.4 % during the new mode. Flow limitations using the novel system were significantly lower in NREM and REM sleep than when using CPAP. With the criterion of respiratory resistance, we counted 13.6 % of flow-limited breaths during CPAP mode and 10.1% during the new mode. Equivalence testing confirmed equivalence between the novel system and CPAP. Conclusions The results confirm that there is no increase in the number of flow limitations during the new mode as compared to CPAP. [ABSTRACT FROM AUTHOR]