LATE-BREAKING ABSTRACT: Ultrasound capnography: A simple and indirect way to assess airways resistance

Rationale: Volumetric capnography (VC) analyzes the pattern of CO2 elimination as a function of expired volume allowing an estimation of anatomic and functional dead space volumes and ventilation inhomogeneity. Development of ultrasound volumetric capnography (UVC) Scout® technology (Ganshorn Medizin Electronic, Germany) allow to evaluate airflow and gas concentration in expired air at the same time by analysis of expiratory molar mass-volume-curve. Threshold anatomic dead space (VDT) representing the volume of conducting airways that can be functionally correlated with airways resistance (Raw). Objectives: To evaluate reproducibility of UVC derivate parameters in normal subjects and patients with airways obstruction and compare it with traditional and more expensive method (Raw) to evaluate lung function. Methods: Twenty normal subjects (14 males), aged 32 (SD ± 11) years , and twenty patient (15 males), aged 55 (SD ± 12) years, with airways obstruction were enrolled in this study. Normal subject and patients had measurement of spirometry, pletismography and UVC in a random order and duplicate manner. Measures and Main results: Short term reproducibility of UVC did not reveal a systematic difference but demonstrated wide limits of agreement on an individual basis. No direct correlation was found between UVC parameters and traditional lung function in normal subjects. In patients with airways obstruction a significant correlation was found between VDT and Pleth Raw (r = - 0,52; p Conclusions: UVC is a simply, reproducible and cooperation independent method to indirectly evaluate airways function and could became a suitable screening test for lung diseases.