The applicability and interpretation of inert tracer gas washout tests is hampered by the lack of feasible protocols and reproducibility data. We assessed feasibility, variability and reproducibility of a new easy to perform double tracer gas (DTG) single-breath washout (SBW) test and compared this with conventional nitrogen washouts.In 40 healthy nonsmokers and 20 patients with stable chronic obstructive pulmonary disease (COPD), we performed three N 2 vital capacity SBWs, three N 2 multiple-breath washouts and three tidal DTG-SBW tests. Follow-up was after 1 week, 1 month and 6 months. Main outcomes were the lung clearance index (LCI) (N 2 multiple-breath washout), slope of phase III (dN 2 ) (N 2 vital capacity SBW) and slope of phase III (SIIIDTG) (DTG-SBW).In healthy subjects, mean¡SD LCI at baseline was 6.94¡0.61, dN 2 0.99¡0.42% N 2 per litre and SIIIDTG -0.206¡0.108 g?mol -1 ?L -1 . In COPD, LCI and dN 2 were significantly higher (LCI 12.23¡2.67, dN 2 7.43¡5.38% N 2 per litre; p,0.001) and SIIIDTG significantly steeper (-0.653¡0.428 g?mol -1 ?L -1 , p,0.001). Reproducibility was high for main outcome parameters: the intraclass correlation coefficient over 6 months was 0.77 (0.86 in COPD) for LCI, 0.82 (0.89) for dN 2 and 0.83 (0.93) for SIIIDTG.The tidal DTG-SBW is a reproducible test in healthy and COPD subjects that seems attractive for use in routine clinical settings. @ERSpublications DTG-SBW may play a role in detection and monitoring of small airway diseases or as an outcome in drug trials

A wide-band high-speed data acquisition system for electrical impedance tomography (EIT) is described. 32 active electrodes are used in the system, half of them as receive electrodes and the other half as drive electrodes. A buffer is mounted on the back of each receive electrode and a current source on each drive electrode. A multielectrode system with active electrodes was built to make it convenient to attach all the electrodes on the human thorax. The system is suitable for both dynamic imaging and multifrequency electrical impedance tomography (MFEIT). Its operating frequency can be chosen between 24 kHz and 400 kHz. Current is injected sequentially into 16 adjacent current electrode pairs and the 16 voltages between adjacent receive electrodes are measured for each current injection. ECG is collected to determine the relationship between the reconstructed images and cardiac activity. The collection of one frame of data is completed within 25 ms. The system has been successfully used for imaging the variation of conductivity distribution of the human thorax. The beat-by-beat cardiac-related change of conductivity distribution has been imaged by our system. The quasi-periodic variation of the impedance distribution can be seen from the image sequence with breath-holding.

Minimally invasive robotic surgery (MIRS) entails total absence of haptic feedback due to the spatial separation of patient and surgeon. In conventional surgery, however, palpation to detect superficial arteries by a slight pulsation is an important, commonly applied, and security-relevant procedure. Therefore, an ultrasound based unidirectional sensor for MIRS was developed feeding back kinesthetic impulses to the surgeon-sided haptic input device.

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For the assessment of small airway diseases, a noninvasive double-tracer gas single-breath washout (DTG-SBW) with sulfur hexafluoride (SF) and helium (He) as tracer components has been proposed. It is assumed that small airway diseases may produce typical ventilation inhomogeneities which can be detected within one single tidal breath, when using two tracer components. Characteristic parameters calculated from a relative molar mass (MM) signal of the airflow during the washout expiration phase are analyzed. The DTG-SBW signal is acquired by subtracting a reconstructed MM signal without tracer gas from the signal measured with an ultrasonic sensor during in- and exhalation of the double-tracer gas for one tidal breath. In this paper, a simple method to determine the reconstructed MM signal is presented. Measurements on subjects with and without obstructive lung diseases including the small airways have shown high reliability and reproducibility of this method.