Standardization of the two compartment model for the partitioning of exhaled NO: Effect of different flows and breath-hold periods

Introduction: Peripheral and central airways nitric oxide (NO) can be partitioned using the multiple constant exhalation flows (Tsoukias et al 1998). We hypothesized that the choice of different flows and breath-hold periods may affect the results. Objective: To investigate the effect of different combinations of multiple exhalation flow rates and breath hold on the bronchial production (JawNO) and alveolar concentration of NO(CANO) in healthy subjects. Methods: Fractional exhaled NO (FeNO) was measured (Niox Flex, Aerocrine, Sweden) in 18 healthy subjects (34.5± 6.52 years), using different sets of flows: Set1: 10,30,50,100,200,300 ml/sec; Set2: 30,50,100,200,300ml/sec; Set3: 50,100,200,300ml/sec; Set4: 100,200,300ml/sec; Set5:50,100,200ml/sec; Set6: 30,50,100,200ml/sec; Set7:10,50,100,200ml/sec; Set8: 10,30,50,100,200ml/sec. In addition, in a separate experiment, eExhaled NO was measured after a 20 seconds breath-hold at total lung capacity. Results: JawNO and CANO were significantly affected by different sets of flow rates and varied between 632.5± 70.58 pl/sec and 892.0±109.4 pl/sec (p Conclusion: The choice of different sets of exhalation flow rates significantly affect JawNO and CANO, therefore, standardization of the measurements is required. In addition, breath holding should be avoided as it significantly affects NO parameters. We acknowledge the support of the ERS, Fellowship STRTF 373-2011.