Sleep Lab Monitor BME 400 University of Wisconsin Madison December 12 2008 Team Jack Page Team Leader Nicole Daehn Communicator Lindsey Carlson BSAC Robyn Hrobsky BWIG Client Christopher G Green MD Department of Pediatrics School of Medicine and Public Health Advisor Willis Tompkins Department of Biomedical Engineering University of Wisconsin Madison Table of Contents Abstract 3 Background 3 Sleep Disordered Breathing 3 Polysomnography 4 Problem Overview and Problem Statement 7 Product Design Specifications Summary 8 Alternate Designs 8 Cuff Design 8 Clip Design 10 Final Design 11 Imbedded Wire Design 11 Attachment Alternative Designs 13 Attachment Design Matrix 14 Attachment Final Design 15 Testing 17 Future Work 21 APPENDICES 23 References 23 Project Design Specifications 24 2 Abstract Sleep disordered breathing SDB is a very common disorder among all ages which can be detrimental to behavioral emotional social and physical health These disorders are diagnosed by polysomnography or more simply sleep studies Most of the people who suffer from SDB are undiagnosed and thus these sleep studies become very important for diagnosing these disorders For pediatric patients there are many weaknesses to the current method of studies Currently a unit containing thermistors and a cannula are stacked on top of each other under the patient s nose Because of the small size of a child s nose this method can obstruct the nostrils and make it difficult to breathe Also because of the small size of a pediatric patient s head and face the method used to secure the devices is not sufficient and the devices may not stay in place throughout the night These problems can lead to inaccurate measurements discomfort and sleep disruption especially in pediatric patients To help solve these problems many different design options were explored and evaluated A prototype of the design that best solves the current issues has been built The prototype combines temperature change during exhalation pressure and end tidal carbon dioxide ETCO2 measurements into one device samples from both nostrils and the mouth and attaches to a pediatric patient in both a durable and comfortable fashion Background Sleep Disordered Breathing Sleep disordered breathing SDB refers to a class of breathing disorders which occur when a person is sleeping SDB includes sleep apnea hypopnea heavy snoring or even increased airway resistance during sleep Three types of sleep apnea are included in this group 3 which affect more than 18 million Americans 1 These are obstructive central and mixed apnea Obstructive apnea is characterized by a blocked airway which ceases breathing However with obstructive apnea the patient is still attempting to breathe 2 Central apnea means that the patient is not breathing but there is no effort to breathe 2 Mixed apnea is a combination of obstructive and central Hypopnea is different than apnea because there is actually airflow occurring However the patient is experiencing very shallow breaths or a very low respiration rate 3 These disorders can be very detrimental to the health of the individual experiencing them These individuals can wake up hundreds of times each night without even knowing it 1 This can lead to behavioral social emotional and physical problems Behavioral problems include the inability to pay attention which can lead to misdiagnoses of Attention Deficit Hyperactivity Disorder ADHD poor academic performance or poor on the job performance caused by fatigue and being tired throughout the day Social and emotional problems include irritability being easily agitated and depression 1 2 More serious physical health problems include delayed mental and physical growth memory problems weight gain and hypertension which can lead to a heart attack or stroke 3 2 Since these disorders occur at night most of the people who suffer from them do not even know that there is a problem For example it is estimated that more than 50 percent of the people who suffer from sleep apnea are undiagnosed 1 This is an immense problem which needs to be resolved The diagnosing of SDB is very important Polysomnography Polysomnography is the technical name for a sleep study Physiological parameters related to sleep and breathing are measured and recorded continuously throughout the night 4 during polysomnography These measurements include an electroencephalogram EEG to measure brain electrical activity an electroocculogram EOG to measure eye movement an electromyogram EMG to measure muscle movement an electrocardiogram ECG to measure heart rate and rhythm piezo crystal effort sensors to measure respiratory effort and a pulse oximeter to measure oxygen saturation These measurements are made by electrodes effort belts and other sensors places on the head eyes chin chest abdomen and legs see Figure 1 There is also a thermistor unit to measure flow and a cannula to measure nasal pressure and endtidal carbon dioxide ETCO2 which are placed on top of each other between the nose and upper lip see Figures 2 and 3 All of the sensors which are hooked up to the patient during the studies are shown in Figure 4 5 6 Each of the measurements taken throughout the night is displayed on computers using software where technicians and doctors can monitor them Figure 5 shows a screenshot of this information The doctors use this information to determine if the patient is suffering from many different conditions For example if the TFlow channel does not show breathing then the doctor knows the patient is experiencing an apnea episode Then the doctor looks at movement in the chest and the abdomen to determine if the apnea is obstructive or central If there is no effort in the chest and abdomen channels then it is central apnea which is shown highlighted in Figure 5 Problem Overview and Problem Statement The three measurements this design focuses on are the measurements taken directly from each breath by devices placed under the nose The following devices are used a thermistor to detect temperature difference between inhaled and exhaled air pressure sensors that show a flattening pressure profile during upper airway narrowing and CO2 sampling tubes to sense ETCO2 These three measurements are taken from two different devices placed under the child s nose with two prongs going into each nostril For the pediatric patient there are many different problems with the way these measurements are taken The thermistor unit shown in Figure 3 is stacked on top of a