IDENTIFICATION OF DIFFERENT RESPIRATORY RATE BY A PIEZO POLYMER BASED NASAL SENSOR Roopa G Manjunatha, N. Ranjith, Y.V. Meghashree, K.Rajanna Department of Instrumentation and Applied Physics Indian Institute of Science (IISc) Bangalore, India kraj@isu.iisc.ernet.in D. Roy Mahapatra Department of Aerospace Engineering Indian Institute of Science (IISc) Bangalore, India Abstract— In this paper, we present a new nasal sensor system developed using Polyvinylidene fluoride (PVDF) piezo polymer in cantilever configuration and its applicability for measuring human Respiration Rate (RR). Two identical PVDF nasal sensors are mounted on a headphone such that they are located below Right Nostril (RN) and Left Nostril (LN), in such a way that the nasal airflow during inspiration and expiration impinge on sensors. Due to nasal airflow, piezoelectric natured PVDF nasal sensors generate corresponding voltage signals. The RR is the number of breaths per minute (bpm). The RR was determined from the filtered respiratory signals, by computing a power spectral density (PSD) spectrum using Welch method of averaged periodograms. The developed PVDF nasal sensors were capable of identifying different RR corresponding to normal (18.5±1.5 bpm), tachypnea (34.5±4 bpm), and bradypnea (10.5±2.2 bpm) similar to ‘Gold standard’ Respiratory Inductance Plethysmograph (RIP) method and Nasal Prongs (NP). Keywords: Respiration rate, breathing type, Polyvinylidene fluoride (PVDF), Respiratory Inductance Plethysmograph, Nasal Prongs. I. INTRODUCTION Respiratory Rate (RR) is a very important physiological parameter to be monitored in people both in healthy and critical condition, as it gives valuable information regarding their respiratory system performance [1]. The RR is defined as the number of breaths per minute [2]. A typical RR at resting is 12 and its corresponding frequency is 0.2 Hz [2]. During recovery from surgical anesthesia, a µ-opioid agonists used for pain control can slow down RR leading to bradypnea (RR<12) or even apnea (cessation of respiration for an indeterminate period) [3], while airway obstructions like asthma, emphysema and COPD will increase RR causing tachypnea (RR > 30) [4]. Hence RR measurement becomes clinically very important. The methods commonly used for measuring RR are visual observation, impedance pneumography, acoustic sensing, fiber optic sensing, Respiratory Inductance Plethysmograph (RIP) and nasal prongs (NP) [5]. However, due to very sensitive patients’ movements and high cost, these methods find limited use in the clinical settings [6]. Polyvinylidenefluoride (PVDF) is a piezoelectric polymer that generates an electrical charge when it is mechanically deformed [7]. Earlier, Siivola examined the use of PVDF to record the body movements caused by the respiration and cardiac action in lying position [8]. Choi and Jiang developed a belt sensor with PVDF for measuring respiratory cycle [9]. In our present study, PVDF nasal sensor, RIP and NP were used to measure the RR of healthy human beings at rest. The aim here was to evaluate a new PVDF nasal sensor for identifying different RR compared to ‘Gold standard’ RIP and NP methods. II. METHODS AND MATERIALS PVDF NASAL SENSOR PVDF film ( Precision Acoustics, UK) is taken in the cantilever configuration to form a PVDF nasal sensor [10]. The length, width and thickness of the PVDF cantilever were optimized to 10mm×5mm×28µm. Two such identical nasal sensors were mounted on either side of headphone such that one PVDF nasal sensor is located below Right Nostril (RN) and the other below Left Nostril (LN), such that the nasal airflow during inspiration and expiration impinge on sensors. Since PVDF has piezoelectric property (polarization produced by mechanical forces), it gives corresponding voltage signal when nasal airflow impinge on it. The PVDF nasal sensors measures respiration from RN and LN, separately and simultaneously. Respiratory inductance plethysmograph (RIP) Respiratory inductive plethysmography (Respi-trace TM ) measures the changes in thoracic and abdominal cross- sectional area to provide an indirect measure of respiration [11]. It consists of two flexible sinusoidal wires embedded separately in stretchy fabric bands; one wrapped around the chest and the other around the abdomen .The inductance of each band changes upon rib cage and abdominal displacements and generates a voltage signal proportional to its inductance. The electrical sum of the ribcage and abdominal signals provides the total thoracoabdominal displacement. Nasal Pronges (NP) Assessment of nasal airflow is carried out by recording pressure at the nostrils [12]. To achieve this, conventional 978-1-4673-4642-9/13/$31.00 ©2013 IEEE