There is a lack of noninvasive pulmonary function measurement techniques suitable for continuous long-term measurement of tidal breathing in mobile subjects, although tidal breathing analysis has been shown to contain information that relates to the level airway obstruction. This paper is the first to assess the suitability of impedance pneumography (IP) for measurement of continuous pulmonary flow and volume signals instead of only the respiration rate (RR) or tidal volume ( V(T)). We measured pneumotachograph (PNT) and IP signals simultaneously from 20 healthy male subjects in erect, dorsal supine, and lateral supine positions while voluntarily varying V(T). IP was measured using five different impedance lead configurations with electrodes integrated into a textile chest belt. The IP signals were compared with PNT signals to assess agreement of IP with a more well-established measurement method. The pulmonary flow signal waveform agreement was assessed with standard error of measurement (SEM) between the time-differentiated IP signal and the PNT signal as rho = 1-SEM. Additionally, we assessed the agreement of IP and PNT in V(T) estimation and the magnitude of the cardiogenic oscillation present in the impedance signal. The agreement in the pulmonary flow signal waveform shapes was found excellent at all tidal volumes and postures (mean rho > 0.90). The agreement between the PNT-derived and the IP-derived V(T) estimates was very high when IP values were calibrated per subject and posture (mean difference < 3%). The main source of error in visual inspection of the IP signal was the cardiogenic distortion. From the five novel electrode configurations tested, the lateral ones were found clearly better than the anteroposterior ones. IP potentially enables the development of a noninvasive ambulatory measurement device for long-term studies of certain tidal breathing parameters in mobile subjects.

Impedance pneumography (IP) is a non-invasive respiration measurement technique. Emerging applications of IP in respiratory medicine use the measured signal to monitor pulmonary flow and volume parameters related to airway obstruction during tidal breathing (TB). This requires a high impedance change (ΔZ)-to-lung volume change (ΔV) linearity. Four potential electrode configurations were tested on 10 healthy subjects. Only the novel configuration where the electrodes were placed in both the thorax and the arms yielded a highly linear ΔZ/ΔV in all subjects. The presented electrode configuration may expand the clinical use of IP from the conventional tidal volume estimation to flow measurement.

In this paper, we present an open-source platform for wireless body sensor networks called DexterNet. The system is motivated by shifting research paradigms to support real-time, persistent human monitoring in both indoor and outdoor environments. The platform utilizes a three-layer architecture to control heterogeneous body sensors. The first layer, called the body sensor layer (BSL), deals with design of different wireless body sensors and their instrumentation on the body. We detail two custom-built body sensors: one measuring body motions and the other measuring the ECG and respiratory patterns. At the second layer, called the personal network layer (PNL), the wireless body sensors on a single subject communicate with a mobile base station, which supports Linux OS and the IEEE 802.15.4 protocol. The BSL and PNL functions are abstracted and implemented as an opensource software library, called Signal Processing In Node Environment (SPINE). A DexterNet network is scalable, and can be reconfigured on-the-fly via SPINE. At the third layer, called the global network layer (GNL), multiple PNLs communicate with a remote Internet server to permanently log the sensor data and support higher-level applications. We demonstrate the versatility of the DexterNet platform via three applications: avatar visualization, human activity recognition, and integration of DexterNet with global positioning sensors and air pollution sensors for asthma studies.

Lung function variability is a fundamental feature of asthma but has been difficult to quantify in children due to methodological limitations. We assessed the feasibility and clinical implications of overnight flow variability measurement at home using impedance pneumography in young children.44 children aged 3-7 years with recurrent or persistent lower airway symptoms were recruited. Patients were divided into high- or lower-risk groups (HR and LR groups) based on their risk of asthma (modified Asthma Predictive Index), and a third group was formed of children who had a history of wheeze and who were treated with inhaled corticosteroids (ICS group). Tidal volume and the derived flow were recorded through skin electrodes using impedance pneumography at home during sleep. Quantities describing overnight change in expiratory flow-volume minimum curve shape correlation (CSRmin) and respiratory chaoticity (minimum noise limit (NLmin)) were derived.Recordings were successful in 34 children. CSRmin differed between the HR and LR groups (p=0.002) and between the HR and ICS groups (p=0.003), indicating a stronger change in flow profile shape in the HR group. NLmin differed between the HR and LR groups (p=0.014), indicating momentarily lowered chaoticity in the HR group.Impedance pneumography was found feasible for quantifying nocturnal lung function variability and the measured variability was associated with risk of asthma in young children.

This paper describes a design and implementation of a portable physiological signal recorder. The device is designed for measuring electrocardiography, bioimpedance, and user's activity. The bioimpedance measures the dynamic changes in the impedance, and its main application is monitoring user's respiration. Activity is measured with three-axis acceleration sensor. During the design, a special attention is paid on the device's power consumption and the target has been set to a 24-h operating time. Functionality of the implemented measurement device is proven with test measurements, which include, e.g., comparison of measurement signals against reference signals, testing the device operation under vigorous upper body movements, and during a light exercise. In order to verify the device operation during real-life activities, one full day, 24-h long, measurement is carried out. The measurement system is tested with both commercial Ag/AgCl gel-paste electrodes and custom-made textile electrodes. Device is proven to be operational with both electrodes, but textile electrodes are found to be more sensitive for movement artifacts. This paper also gives a small review of other existing portable and wearable physiological measurement devices and discusses some general requirements of these devices.