New Oxygenation Method Based on Pulse Oximeter

The body’s need of oxygen is certainbecause of its necessity to make energy from the food. Lungs deliver oxygen to the blood and if it cannot get enough oxygen to the blood, the patient feels short of breath, which is very uncomfortable. In this state, oxygen therapy can be help ful. Blood gas measurement provides vital information about oxygenation, ventilation and acid-base status. However, these measurements only provide a snapshot of the patient’s condition taken at the time that blood sample was drawn. Oxygen level can change very quickly. In the absence of continuous oxygenation monitoring, these changes may go undetected until it is too late. In this paper, we present a new method of online oxygenation, which, could g ive oxygen to the patient with high accuracy and solve many problems involved in other methods. Ten patients; five COPD and five patients suffer of asthmawere examined with this new method of oxygenation. None of the patients exh ibited signs of oxygen toxicity during new method of oxygen therapy. Experimental results show the acceptability of new oxygenation method in examined subjects.


Introduction
Oxygen is necessary for the body because all o f the main organs and tissues use it. When the body does not get enough oxygen, the patient may have difficulty b reathing, problems with heart, fatigue, loss of me mory, headaches, or confusion.
Oxygen therapy provides extra o xygen, which the body needs to work well. Normally, lungs absorb oxygen from the air. Ho wever, some d iseases and conditions may prevent patient fro m getting enough oxygen. Oxygen therapy can increase the supply of oxygen to the lungs and thereby increasing the availability of o xygen to the body. Usually oxygen flows through a tube and delivered to the lungs through a nasal cannula, a facemask or a s ma ll tube inserted into windpipe through the front of patient neck.
Oxygen therapy can be done in a hospital, med ical setting, or even at home. If the patient needs oxygen therapy for an ongoing disease or condition, he/she might receive ho me oxygen therapy. The oxygen is prescribed to treat a number of conditions regard lung and heart d iseases such as chronic obstructive pulmonary disease (COPD), chronic bronchitis, emphysema, severe asthma and hypertension.It may be prescribe to treat a group of patients who will require o xygen for palliative care o r short burst needs [1]. Patients, who suffer fro m COPD, rely on o xygen tanks and concentrators to deliver a mo re pure form of o xygen so that they get the right amount to their blood cells.
There are two main methods of oxygen therapy, which are through hydrogen peroxide and ozone treatment: a) Ozone treat ment involves forcing oxygen through a meta l tube carrying a 300-volt charge. Then a pint of blood drawn fro m the patient and placed into an infusion bottle. Ozone is then forced into the bottle and mixed so that the ozone mo lecules dissolve into the blood and, in so doing, destroy all lipid-envelope virus and many disease organisms, but leave the blood unharmed. Then the treated blood returned to the patient [2]. b) Hydrogen peroxide, when exposed to the blood or other body fluids containing the enzy me 'catalase' is chemically splits into oxygen and water. Many people have experienced the foaming effect p roduced by putting hydrogen peroxide on a wound; the foam is o xygen produced by the action of catalase on the hydrogen peroxide [3].
Each o f o xygen therapy methods has some advantages and disadvantages. The point that should be note is that the real-t ime and online o xygen therapy is important to keep the patient in safe condition.
Pulse o ximetry is a technology for noninvasively measurement of o xygen saturation, respiratory rate, etc. Using this technology the hypoxia can be detected before the patient show signs of becoming cyanotic [4]. Without pulse oximetry, it is hard to notice the patient has a decreased arterial o xygen saturation of hemoglobin ( 2 ) until the saturation is between 80-85%. Pu lse oximetry is simple to use and provides an immed iate, objective measure of arterial blood oxygen saturation.
However, the important question remains is that how can we use the pulse oximeter measurements in the best way to compensate the lack of o xygen in patients with different diseases. In fact, once the patient using the store oxygen of the body, the oxygen levelshould return to its regular level within minutes. Therefore, it is essential to use the oxygen at the times it shows low level. In this paper, we present a new method of online o xygenation, which has a reliable accuracy for various types of diseases.

Pulse Oximeter Measurements
Pulse o ximetry is a non-invasive method of determin ing the percentage of hemoglobin ( ) saturated with o xygen. Takuo Aoyagi, a bio medical engineer working for the Shimad zu corporation in Kyoto, Japan, in the early 1970, invented it [5,6].
Knowing what percentage of the hemoglobin is saturated with o xygen is important when providing anesthesia or for determining the effectiveness of the respiratory system as well as helping in diagnosing various illnesses [7][8][9].
Pulse oximeter measures the absorption of red and infrared light passed through the patient's finger (ear lobe) by utilizing light sensors. Within the 2 sensor, light emitting d iodes shine red and infrared light through the tissue.
The blood, tissue and bone at the application site absorb much of the light. However, some light passes through the extremity. A light-sensitive detector opposite the light source receives it .
Hemog lobin that is carry ing o xygen (o xy-hemoglobin) absorbs infrared wavelength of light and hemoglobin not carrying o xygen (de-o xy-hemoglobin) absorbs visible RED wavelength. Hemoglobin is a protein and the main component of red blood cells, and transports oxygen from the lungs, where o xygen tension (partial pressure of oxygen) 2 is high, to the tissues, where oxygen tension is low [10]. The sensor measures the amount of red and infrared light received by the detector and calculates the amount absorbed. Much of it is absorbed by tissue, bone and venous blood, but these amounts do not change dramatically over short periods.
Backg rounds such as fluid, tissue and bone are factored out of the measurement by mon itoring the steady state absorption fro m bone, tissue, venous blood and arterial blood.
LEDs are used as the light source and are sequentially pulsed at a rapid rate. The amount of arterial blood does change over short periods due to pulsation (although there is some constant level of arterial b lood). Because the arterial blood is usually the only light absorbing component, which is changing over short periods, it can be isolated from the other components.
During an arterial pulse, there is an increase blood volume and this AC component is used to calculate the absorption of oxy and de-o xy hemoglobin. The amount of light received by the detector indicates the amount of o xygen bound to the hemoglobin in the blood.
Fro m this data, the pulse oximeter does the mathemat ical calculations based on the Beer-Lambert Law to determine the percent oxygen saturation of the blood [11][12]: = 0 ( ) (1) where 0 is the original intensity of the light, ( ) is the extinction coefficient at a specific wavelength λ. In addition, c is the concentration of the substance absorbing the light, and d is the optical path length.
Pulse oximet ry performed by placing a clip that contains two LEDs and the light sensor either onpatient's finger or on earlobe. One of the LEDs emits red light (600-700 n m) and the other near infrared (800-940 n m).
Oxygen saturation ( 2 ) is defined, as the ratio of the amount of bound o xygen to the total o xygen capacity,equation (2), where ( 2 ) is the concentration of oxy-hemoglob in, and ( ) is the concentration of de-oxy-hemoglob in. If the hemoglobin mo lecule is bound to oxygen then one has oxy-hemog lobin or ( 2 ), and If the hemoglobin mo lecule is bound to carbon mono xide then one has carboxy-hemoglobin or ( ). If the hemoglobin mo lecule is bound to nothing then one has de-oxy-hemoglo bin or ( ) or reduced hemoglobin. If the hemoglobin mo lecule has broken down then one has met-hemoglobin. These all have different spectra but here we concentrate on ( 2 ) and ( ). Oxygen saturation is calculated as a percent or fraction by [13][14][15]: In healthy adults arterial o xygen saturation ( 2 ) is approximately 97%. This depends on physiologicalparamet ers as well as on the oxygen partial pressure of the inspired air.

New Method of Oxygenation
A brief rev iew of pulse o ximeter and measuring the oxygen saturation of blood has been given. In fact, this brief review was necessary to exp lain our invention. The 2 measured by pulse oximeter is an accurate measurement of patient's oxygen saturation level, which in a normal status is about 97-98%.
Usually after measuring the o xygen saturation, depending the 2 value and kind of disease physician prescribes a method to compensate the lack of oxygen.Finding outthe lack of o xygen on time, is a subject that physician and nurses are always worried about it. Some people will experience symptoms such as shortness of breath or difficulty breathing and have a normal blood oxygen level. Others may experience no such symptoms and have a low blood oxygen level. Therefore, even though these symptoms are very impo rtant to watch and consider, it should not be decided to discontinue the oxygen based solely upon symptoms. The only way to know for sure is to have blood oxygen level checked with the o ximetry test.
To solve these problems and increase the accuracy coefficient of o xygenation, we have designed a mechanism that is working with a corresponding software and algorithm based on pulse oximeter measurements.
Figure1 is representing the schema of system and figure 2 and 3 represent the algorithm and block d iagram o f the system respectively. The system consists of a simp le pulse oximeter, an o xygen capsule, an A/D converter (to convert the digital 2 giving fro m pulse o ximeter to the appropriate data for mic ro-programmer [16][17][18]), electric valve for controlling the oxygenation process, and a small LCD fo r showing the results and messages.

Software
The use of microcontroller is co mmon in every field even it can be use in design and fabrication of bio medical equipments. The89s51 (8051) microcontroller was used to develop the oxygenation system. The software of thissystem has the follo wing capabilit ies: a) Measuring the oxygen saturation of blood, b) Co mparing the o xygen saturation with the normal value, c) Alarm to inform the health care staff when a problem like lack of o xygen or even over saturation occurs, d) Controlling the electric valve that is connected to oxygen capsule or central o xygen of the hospital to give on-time o xygen to the patient.

Algorithm of Working
At first step, the kind of disease should be entered by keypad. Since each disease needs a specific amount of oxygen, (for examp le in chronic bronchitis the patient needs 2-3 lit/ min, or in asthma 7-10 lit/ min, and in cardiac ischemic 7-10 lit/ min is needed) the kind of disease should first, be specified.
The device will co mpare the measured 2 with the normal value and display the result. That is, if the measured value is belo w the normal, alarm will also go off warn the health care staff. A warning message will be display on LCD and electric valve will be automatically open to allow the oxygen capsule start the oxygenation process.
Since 2 is measured continuously, as long as it d id not reach to normal value, o xygenation process will be continued. After 2 gained to the norma l value, the electric valve will be closed and oxygenation process will be stopped.
Moreover, this method can prevent the problem of over-saturation that sometimes occurred in other ways of oxygenation. If o xygenation process takes a long time, the over saturation message will represent on LCD and electric valve will be closed.

Results
We studied 10 patients; five COPD and five patients suffer of asthma (4 men and 6 wo men). Their meanage was 36.5 ±3.4 years. None of the patients exhib ited signs of oxygen toxicity during new method of oxygen therapy. The new method showseffective, safe, and on-time o xygenation for both types of examined diseases.

Conclusions
Oxygen therapy helps many people function better and be more active. Although patients may need oxygen therapy for a long term, it does not have to limit their daily routine.
Portable o xygen units can make it easier to move around and do many daily activit ies. More people are using o xygen therapyoutside the hospital, permitting them to lead act ive, productive lives. People with asthma, emphysema, ch ronic bronchitis, occupational lung disease, lung cancer, cystic fibrosis, or congestive heart failure may use o xygen therapy at home.
Hospital environ ment could cause depression especially in patients with long confined period. Therefore, any methods such as oxygenation with pulse o ximeter that can safe patients fro m hospitalization would be desirable.
Experimental results show that new oxygenation method coupled with pulse oximetry analysis is feasible, accurate, inexpensive and applicable to the clin ical setting and home care services.Thepresented system in this paper could work with a 5-volt battery, so it could be a portable systemjust with adding a small o xygen capsule to the system. Therefore, the ho mecare services, wh ich are the most interesting topic in recent decade, could be practicable. Furthermore, by adding a pressure sensor to the oxygenation circuit, the safety of oxygenation especially in homecare services would be twice as much, because the pressure sensor could display the storage amount of oxygen in the capsule.With a simp le calcu lation the capsule's volu me could be estimated, so the user would be informed that the oxygen store would be finished for examp le during 2 hours.
In addition to health economizing the human time and energy spent, it will help the health care staff to increase the accuracy coefficient of o xygenation, especially when the number of patients is more than the staff. This method can avoid the over saturation that can occurs in other methods of oxygenation.
Our future aim is to equip the system, so that the data could be sending using Bluetooth wireless technology. The data can be stored and displayed locally fo r telemedicine applications. It can also transmit in real-time to a central monitoring centre over the internet, which would be well suited for re moterespiratory monitoring and home sleep apnea screening.