Hannu Sorvoja

Wireless sensor and data transmission needs and technologies for patient monitoring in the operating room and intensive care unit

In the intensive care unit, or during anesthesia, patients are attached to monitors by cables. These cables obstruct nursing staff and hinder the patients from moving freely in the hospital. However, rapidly developing wireless technologies are expected to solve these problems. To this end, this study revealed problem areas in current patient monitoring and established the most important medical parameters to monitor. In addition, usable wireless techniques for short-range data transmission were explored and currently employed wireless applications in the hospital environment were studied. The most important parameters measured of the patient include blood pressures, electrocardiography, respiration rate, heart rate and temperature. Currently used wireless techniques in hospitals are based on the WMTS and WLAN standards. There are no viable solutions for short-range data transmission from patient sensors to patient monitors, but potentially usable techniques in the future are based on the WPAN standards. These techniques include Bluetooth, ZigBee and UWB. Other suitable techniques might be based on capacitive or inductive coupling. The establishing of wireless techniques depends on ensuring the reliability of data transmission, eliminating disturbance by other wireless devices, ensuring patient data security and patient safety, and lowering the power consumption and price

Measurement of respiratory rate with high-resolution accelerometer and emfit pressure sensor

Respiratory rate is an essential parameter in the clinical monitoring of hospital patients. It can be measured in various ways, such as by recording chest movements, breathing flow or heart rate variations. Current sensor technology allows the development of new kinds of convenient and portable respiratory rate recorders, including smart shirts, which enable more efficient healthcare processes in hospitals. This study carried out respiratory rate measurements using a sensor belt with a high-resolution accelerometer (capacitive MEMS) and an EMFit (electret film) pressure sensor. Results obtained from tests on 10 subjects showed that both sensors are feasible for respiratory rate measurement; the reliability of the MEMS was 90%, while that of the EMFit was 90- 100%. In addition, the results showed that the location of the sensor module on the chest is important.

Use of EMFi as a blood pressure pulse transducer

This paper describes and tests two prototype series of pressure transducer arrays based on electromechanical film (EMFi). By offering high (/spl sim/T/spl Omega/) resistance, EMFi is an excellent material for low-current long-term measurement applications. About 50 transducer arrays were designed and tested using different configurations and electrode materials to sense low-frequency pressure pulsations on the radial artery in the wrist. Essential requirements included an adequate linear response in the desired temperature range and uniform quality. Transducer sensitivity was tested as a function of temperature in the range of 25/spl deg/C-45/spl deg/C at varying dc and ac pressures. The average sensitivity of the EMFi used in the transducers proved adequate (/spl sim/2.2mV/mmHg and /spl sim/7 mV/mmHg for normal and high-sensitive films) for the intended purpose. Moreover, EMFis spectral response covered the required range for biomedical applications, but it was unable to measure static pressure (f/sub 3 dB//spl ap/38 /spl mu/Hz). The sensitivity of the EMFi material was sufficiently constant for measuring blood pressure pulses in the desired range (0-300 mmHg), and the best achieved deviation in sensitivity was /spl plusmn/5.1%. It was also established that in addition to sensitivity and its standard deviation, crosstalk between electrode elements also depends strongly on electrode thickness.

Fibre optic sensor for non-invasive monitoring of blood pressure during MRI scanning

This report focuses on designing and implementing a non-invasive blood pressure (NIBP) measuring device capable of being used during magnetic resonance imaging (MRI). Based on measuring pulse wave velocity in arterial blood, the device uses the obtained result to estimate diastolic blood pressure. Pulse transit times are measured by two fibre optical accelerometers placed over the chest and carotid artery. The fabricated accelerometer contains two static fibres and a cantilever beam, whose free end is angled at 90 degrees to act as a reflecting surface. Optical fibres are used for both illuminating the surface and receiving the reflected light. When acceleration is applied to the sensor, it causes a deflection in the beam, thereby changing the amount of reflected light. The sensors output voltage is proportional to the intensity of the reflected light. Tests conducted on the electronics and sensors inside an MRI room during scanning proved that the device is MR- compatible. No artifacts or distortions were detected.

A two-threshold fall detection algorithm for reducing false alarms

Wireless health monitoring can be used in health care for the aged to support independent living, either at home or in sheltered housing, for as long as possible. The most important single monitoring need with respect to security and well-being of the elderly is fall detection. In this paper, a two-threshold MATLAB-algorithm for fall detection is described. The algorithm uses mainly tri-axial accelerometer and tri-axial gyroscope data measured from the waist to distinguish between fall, possible fall, and activity of daily living (ADL). The decision between fall and possible fall is done by the posture information from the waist- and ankle-worn devices ten seconds after the fall impact. By categorizing falls into these two sub-categories, an alarm is generated only in serious falls, thus leading to low false alarm rate. The impact itself is detected as the total sum vector magnitudes of both the acceleration and angular velocity exceeds their fixed thresholds. With this method, the sensitivity of the algorithm is 95.6% with the set of 68 recorded fall events. Specificity is 99.6% with the set of 231 measured ADL movements. It is further shown that the use of two thresholds gives better results than just one threshold.

Non-invasive blood pressure measurement based on the electronic palpation method

The most commonly used methods of non-invasive blood pressure monitoring are the auscultation method and the oscillometric method. Although both methods are generally accepted and widely used, they are reportedly inaccurate and irreproducible in terms of specific hypertension screening and control. Here, the authors present a new electronic palpation method based on an arm cuff and a wrist watch type pulse sensor, which they have developed and tested. The results show that this method is more accurate than the auscultation and oscillometric methods. The difference relative to an intra-arterial measurement was -0.8/spl plusmn/4.6 mmHg for systolic values and -1.5/spl plusmn/5.0 mmHg for diastolic values. Moreover, the correlation coefficient of 0.81 was higher than the corresponding figures for the auscultation and oscillometric methods: 0.60 and 0.55, respectively.

Human Heart Pulse Wave Responses Measured Simultaneously at Several Sensor Placements by Two MR-Compatible Fibre Optic Methods

This paper presents experimental measurements conducted using two noninvasive fibre optic methods for detecting heart pulse waves in the human body. Both methods can be used in conjunction with magnetic resonance imaging (MRI). For comparison, the paper also performs an MRI-compatible electrocardiogram (ECG) measurement. By the simultaneous use of different measurement methods, the propagation of pressure waves generated by each heart pulse can be sensed extensively in different areas of the human body and at different depths, for example, on the chest and forehead and at the fingertip. An accurate determination of a pulse wave allows calculating the pulse transit time (PTT) of a particular heart pulse in different parts of the human body. This result can then be used to estimate the pulse wave velocity of blood flow in different places. Both measurement methods are realized using magnetic resonance-compatible fibres, which makes the methods applicable to the MRI environment. One of the developed sensors is an extraordinary accelerometer sensor, while the other one is a more common sensor based on photoplethysmography. All measurements, involving several test patients, were performed both inside and outside an MRI room. Measurements inside the MRI room were conducted using a 3-Tesla strength closed MRI scanner in the Department of Diagnostic Radiology at the Oulu University Hospital.

A mobile user-interface for elderly care from the perspective of relatives.

As the number of elderly people rises, relatives’ care-taking responsibilities increase accordingly. This creates a need for developing new systems that enable relatives to keep track of aged family members. To develop new mobile services for elderly healthcare we tried to identify the most wanted features of a mobile user-interface from the perspective of relatives. Feature mapping was based on two online surveys: one administered to the relatives (N = 32) and nurses (N = 3) of senior citizens and the other to nursing students (N = 18). Results of the surveys, confirmed by face-to-face interviews of the relatives (N = 8), indicated that the most valued features of the mobile user-interface are Accident Reporting (e.g. falling), Alarms (e.g. fire-alarm), Doctor Visits and evaluation of the General Condition of the Senior. The averaged importance ratings of these features were 9.2, 9.0, 8.6 and 8.5, respectively (on a scale from 0 to 10). Other important considerations for the user-interface development are aspiration to simplicity and ease-of-use. We recommend that the results are taken into account, when designing and implementing mobile services for elderly healthcare.

A method to determine diastolic blood pressure based on pressure pulse propagation in the electronic palpation method

Evaluates the accuracy of the pulse transit time method for determining diastolic blood pressure using intra-arterial blood pressure as a reference. First, the paper describes the method. Then it discusses two sets of measurements which were carried out to determine the accuracy of the method with cardiac operated patients and healthy young volunteers. The thus obtained accuracies were +0.7 mmHg /spl plusmn/ 10.7 mmHg for the cardiac patients and -6.6 mmHg /spl plusmn/ 10.5 mmHg for the young volunteers, respectively.

Activity classification using a state transition diagram and activity levels

Wireless health monitoring systems are suggested for use in the health care of the elderly to enable independent but secure living for as long as possible. Activity monitoring is highly valued by welfare and health personnel because it gives an overview of the well-being of the elderly. In this paper, a state transition diagram based activity classification MATLAB-algorithm is described. The state transition diagram takes consideration of the reasonable sequential states. The system distinguishes between different states and activity levels with the help of a single waist worn measurement unit consisting of a tri-axial accelerometer and a tri-axial gyroscope. The allowable states are stand, sit, lie, walk, and fall. Every second of data is classified into one of the previous states, but also into one of the four possible activity levels: passivity, light activity, activity, and intense activity. The performance of the state classification is tested with the data collected in a home environment. The sensitivity and specificity values for the state transitions are in the range of 80-100%. The classifier detects longer continuous periods in the same state with a minimum probability of 85.7%.