We have developed a non-contact microwave radar respirometry method, where the microwave radars are located under the bed, they do not increase the strain on the subjects. In order to evaluate the effectiveness of the microwave radar respirometry, we have conducted clinical tests to make a comparison between the proposed non-contact method and polysomnograph (PSG). We tested the proposed system on twenty subjects suspected to have Sleep Apnea Syndrome (SAS) (male 16, female 4, age 35 to 67, average 49.8±10.1 years old). PSG was adopted as a reference to determine Apnea Hypopnea events. The proposed method detected 75.6% of Apnea Hypopnea events, (2,810 out of 3,716 events), and it was 58.8% of total radar events (2,810 out of 4,780 radar events.).

Evaluation of lung function is a typical application of electrical impedance tomography (EIT) and a wearable EIT has been developed to give easy use and reliable EIT information in an intensive care medicine. However, chest shape information was important factor to decide measurement accuracy and it was very difficult to measure from a patient on a bedside in an intensive care unit. Therefore, we proposed a novel estimation method of a chest shape using curvature data and chest circumference that would be possible to measure with our wearable EIT. Measurement accuracy was evaluated by applying the proposed method to an ellipse shape with 20cm in X-axis and 10cm in Y-axis, the same ellipse with 20% random noise and two CT images of thorax. To evaluate accuracy of estimated shape, we defined eccentricity ‘e’ that was aspect ratio of estimated shape and compared it between actual and estimated shapes respectively. Error in eccentricity ‘e’ was approximately 3% in ellipse shape without noise, 7% in ellipse shape with noise and 7% in two CT images respectively. The result was considered that our proposed method was useful to estimate shape for accurate EIT measurement using a wearable EIT.

It is recommended to verify the dwelling position of nasal feeding tube in the stomach by sampling gastric fluids, however, it is practically difficult to apply. We inserted a nasal feeding tube in 15 subjects, and then attempted to sample gastric fluids and confirmed the position of the tip by a X-ray examination. Measuring lengths of the tube segmented by body-landmarks (e.g., nose, gastric cardia), we verified the correlations between the body-height and the appropriate tube length to be inserted. The average ratio of the tube length from the nose to the gastric cardia against the body-height of the subjects was 0.29±0.01. The average tube length in the stomach was 103.5±9.9 mm, which was not correlated to the subjects′ body-heights. As the results, a simplified formula “Body-height (cm) × 0.3 + 10 cm” can be suggested to estimate the adequate insertion length of the tube which can sample gastric fluids. Further, to easily visualize the dwelling length of the tube in the stomach by a x-ray examination, our results might recommend non-opaque marks with 1-cm increments between the tip and 10 cm-length.