英语专业论文 Design a simple apnea detection system
- A crib or bed with piezo electric or strain gauge transducer attached to each leg is used to acquire the movement of infants.
- Whenever the infant is breathing there is a variation in the force distibution in the foam mat, so the vertical force applied on the frame of the crib also varies,which is captured by the sensors attached to the leg of the crib.
- These sensors convert the force into an electrical output signal and gives it to a summing amplifier to provide a summed output signal from all four legs.
- The summed output is given to a microcontroller where it is compared with the patients physical parameters to give an alarm if there is apnea detected using a buzzer or flashing light.
This apparatus helps to detect apnea in infants who can be monitored even at home instead of hospitals.This alarm system is more comfortable to babies as it does not attach any sensor to infant s body.Mainly used to detect death due to apnea (‘crib death’ or ‘cot death’ ) very common in premature infants.
2.7 APNEA MONITOR DATA SYSTEM
- An apnea monitoring system along with a portable data storage cartridge is presented.
- Respiration is monitored through the electrodes located on the thoracic cavity of the patient.
- Detected events are compared with respiration rates and when it is exceeded the signal is transmitted to audio and visual alarms indicating apnea.
- In addition to that a poratable data storage cartridge is provided which has enough memory to store all monitored events and waveforms that can be transferred to computer.
This invention not only helps to monitor also contains a portable cartridge,that can be easily carried or mailed,which makes it time efficient and cost efficient method to store data.Another advantage is that the cartridge is replaceable,which provides an unlimited amount of memory space that helps in transfer of data.
2.8 A MODEL ANALYSIS OF ARTERIAL OXYGEN DESATURATION DURING APNEA IN PRETERM INFANTS
Scott A. Sands, Bradley A. Edwards, Vanessa J. Kelly, Malcolm R. Davidson, Malcolm H. Wilkinson, Philip J. Berge
- Independent influence of clinically relevant cardiorespiratory fators on the desaturation of arterial oxygen during apnea is determined using a two-compartmental lung-body mathematical model which incorporated realistic oxygen stores and gas exchange dynamic
- Analytic solutions were derived for arterial oxygen desaturation to quantify the importance of cardiorespiratory factors on arterial oxygen desaturation such as cardiac output, lung volume, metabolic oxygen consumption, pre-apneic ventilation, blood oxygen affinity, hemoglobin content and blood volume
- The model analysis reveals that lung volume, hemoglobin content, cardiac output, pre-apneic ventilation exerts a unique effect on arterial oxygen desaturation throughout the time-course of desaturation and metabolic oxygen consumption is uniformly influential throughout the process.
- Infants with elvated metabolic needs and low lung volume and those with anemia, cardiac dysfunction or hypovolemia which are common in prematurity are at heightened risk of rapid and profound arterial desaturation during apnea.
A mathematical framework for quantifying the relative importance of key cardiorespiratory factors on the rate of arterial oxygen desaturation during apnea with particular relevance to preterm infants is provided. Each of the factors examined has a signature influence on the trajectory of desaturation, providing quantitativeinsight into the causes of rapidlydeveloping hypoxemia during apnea have been demonstrated.
2.9 OBSTRUCTIVE SLEEP APNEA AS A RISK FACTOR FOR STROKE AND DEATH
H. Klar Yaggi, M.D., M.P.H., John Concato, M.D., M.P.H., Walter N. Kernan, M.D., Judith H. Lichtman, Ph.D., M.P.H., Lawrence M. Brass, M.D., and Vahid Mohsenin, M.D.
- 1.In this study patients underwent polysomnography and subsequent events like stroke and death are verified.
- 2.The diagnosis was based on apnea-hypopnea index of the patients.Patients with apnea-hypopnea index of less than 5 served as a comparison group.
- 3.Proportional hazards analysis was used to determine the independent effect of OSA syndrome on the outcome of stroke or death from any cause.
- 4.The mean apnea-hypopnea index for the patient with syndrome is 35 while the same for patients in the comparison group is 2.
- 5.After adjustment for age,sex, diabetes mellitus, smoking status, alcohol consumption status, body-mass index, hypertension, the OSA syndrome retained a statistically significant association with stroke or death.
The obstructive sleep apnea syndrome significantly and severely increases the chance for stroke or death from any cause. The increase for the risk of stroke or death due to OSA syndrome is independent of the other risk factors,including hypertension.
2.10 AN ECONOMIC ANALYSIS OF CONTINUOUS POSITIVE AIRWAY PRESSURE FOR THE TREATMENT OF OBSTRUCTIVE SLEEP APNEA-HYPOPNEA SYNDROME
Helen L. A. Weatherly, Susan C. Griffin, Catriona Mc Daid, Kate H. Durée, Robert J. O. Davies, John R. Stradling, Marie E. Westwood and Mark J. Sculpher.
- This study reports on the cost-effectiveness of the continuous airway-pressure(CPAP) compared with the dental devices and lifestyle advice to the patient. The Markov model compared the interventions over the patient’s life expectancy.
- The primary measure for cost-effectiveness was the incremental cost per quality adjusted life-year(QALY) gained for every patient.
- On further analysis, CPAP was associated with higher costs and QALYs compared with dental devices and lifestyle advice.
- The result of analysis was that the probability that CPAP is more cost-effective than dental devices or lifestyle advice at a threshold value of £20,000 per QALY was 0.78 for men and 0.80 for women.
This model suggests that CPAP is cost-effective compared with dental devices and also the lifestyle advice for adults with moderate or severe symptomatic Obstructive Sleep Apnea -Hypopnea Syndrome are at the cost-effectiveness thresholds used by NICE. This finding is reflected in the NICE guidance.
3.1 EXISTING METHODS
Several contactless methods are available for monitoring the respiration of infants. The most successful apnea monitors to-date been mattress monitors. These instruments rely for their operation on the fact that the process of breathing redistributes an infant’s weight and this is detected by some form of a pressure sensitive pad or mattress on which infant is nursed. The mattress, in its simplest form, is a multi-compartment air bed, and in this case the weight redistribution forces air to flow from one compartment to another. The air flow is detected by the cooling effect it produces on a heated thermistor bead. Though the technique is simple, the main disadvantage with the air mattress is the short-term sensitivity variation and the double peaking effect when inspiration or expiration produces separate cooling of the thermistor.
Alternatively, a capacitance type pressure sensor in the form of a thin square pad is usually placed under or slightly above the infant’s head. Respiratory movements produce regular pressure changes on the pad and these alter the capacitance between the electrode plates incorporated in the pad. The capacitance change is measured by applying a 200 kHz signal across the electrodes and by detecting the current flow with a phase-sensitive amplifier. The disadvantage of this method is that the system is much too sensitive to people moving nearby and thus an electrically screened incubator is essential for the infant.
3.1.1 METHOD ADOPTED
This project is based on impedance pneumography method. Impedance pneumography is one of the practical methods to monitor the breathing of the patient. The technique also enables the simultaneous monitoring of the heart rate and respiration. This has certain inherent disadvantages. One is that the placement of the electrodes is very critical and other is cardiovascular artifact. This results from the detection of movement between the electrodes because of the cardiovascular system, rather than due to respiration. Apnea monitors need to be designed to reject this artifact.
So in this project the respiratory signal is considered to be acquired by using respiratory sensor. As there is no availability of sensor, respiratory signal is simulated using our own designed impedance pneumography technique based circuit. Then this signal is given to microcontroller where apnea is detected and it then triggers an alarm. The classification of apnea is also done using LabVIEW.
In future respiratory sensor will be designed and the respiratory signal will be acquired. Then this signal can be given to the microcontroller directly.
3.2 RESPIRATORY SIGNAL SIMULATION
The respiratory signal simulation circuit consists of an excitation source and a constant current source circuit which gives a high frequency, low voltage and constant current signal. This constant current will be applied to the thorax of the subject. But due to the ethical issues the current is applied on the resistance circuit which acts as the thorax impedance. This circuit in turn gives a voltage signal. This voltage signal will be amplified by an instrumentation amplifier. The amplified signal will be fed to the LabVIEW for classification of normal and apnea signal and also types of apnea. Figure 3.2.1 shows the block diagram to simulate respiratory signal and the hardware design of the circuit