A catheter-type flow sensor for measurement of aspirated- and inspired-air characteristics in the bronchial region

Abstract

We developed a novel catheter-type flow sensor for measuring the aspirated- and inspired-air characteristics trans-bronchially. An on-wall in-tube thermal flow sensor is mounted inside the tube, and it is used as a measurement tool in a bronchoscope. The external diameter of the tube is less than a few mm, and therefore, it can evaluate the flow characteristics in the small bronchial region. We newly developed a fabrication process to miniaturize it to less than 2.0 mm in the external diameter by using a heat shrinkable tube. A film sensor fabricated by photolithography was inserted into the tube by hand. By applying a heat shrinking process, the film was automatically mounted on the inner wall surface, and the outer size of the tube was miniaturized to almost half its original size. The final inner and outer diameters of the tube were 1.0 mm and 1.8 mm, respectively. The relationship between the input power of the sensor and the flow rate obeyed King's equation in both forward and reverse flow conditions. The sensor output dependence on ambient temperature was also studied, and the curve obtained at 39.2 °C was used as the calibration curve in animal experiments. The sensor characteristics under reciprocating flow were studied by using a ventilator, and we confirmed that the sensor was able to measure the reciprocating flow at 2.0 Hz. Finally, we successfully measured the aspirated- and inspired-air characteristics in the air passage of a rat.

Development of implantable catheter flow sensor into inside of bronchi for laboratory animal

“…We previously developed a catheter flow sensor that could be used to trans-bronchially measure aspirated-and inspired-air flow characteristics for precise evaluation of chronic obstructive pulmonary disease and confirmed that it could measure the breathing characteristics at the air passage of mice under anesthesia conditions (Shikida et al 2009(Shikida et al , 2010Yamada et al 2014a). The whole surface of the outside tube in the developed catheter flow sensor was tightly fixed onto the inside surface of the air passage in the measurements in these experiments.…”

Micromachined Flow Sensors in Biomedical Applications

“…The sensor allowed diagnosing sleep-specific respiration disturbances that are a risk factor for basic cardiovascular diseases [47]. The sensing element (Figure 2(a)) provided a short response time (about 2 ms), wide flow range (up to about 400 L·min and showed a response time of about 100 ms [50]. The same author designed an anemometer for evaluating nasal respiration with a measurement range up to 2 L·min ) to implement the principle of hot-wire anemometry (Figure 2(b)): one diode, heated by a polysilicon resistor, was placed on a silicon membrane [52]; another unheated diode measured the environmental temperature.…”

Development of Catheter Flow Sensor for Breathing Measurements at Different Levels of Tracheobronchial Airway

“…However, breathing characteristics are difficult to evaluate directly at lesions region. Thus, microelectromechanical systems (MEMS) technologies were previously applied to produce a novel miniaturized flow sensor to precisely evaluate COPD ( Figure 1) [2]. This flow sensor can measure breathing characteristics in lesions with high accuracy because it is inserted in lesioned parts directly.…”