Oximeter

Pulse oximeter Check blood glucose Check laboratory tests complete blood count serum chemistries liver function tests arterial blood gas blood cultures serum anticonvulsant levels urine drug/alcohol screen... 

The stoichiometries of both oxygen consumption and of proton release subsequent to Fe(III) hydrolysis have been determined by using a combined oximeter and pH stat (Yang et ah, 1998). The overall reaction at the ferroxidase centre is postulated to be ... 

This aspect makes it clear why optical fibre sensors for medical applications have been characterised by a remarkable development after the introduction of optical fibres. The first invasive optical fibre oximeter which was described in 19641, can be considered one of the first optical fibre sensors. Since then, many sensors have been proposed which find application in different biomedical areas, ranging from cardiovascular and intensive care to angiology, gastroenterology and ophthalmology. Some of these are still at the prototype level, whereas others are already available on the market. 

The development of new oximeters is also in progress, with the application of time- and frequency-domain techniques which are, in principle, capable of discriminating between the absorption and scattering contributions coming from human tissue, thus making possible the detection of tissue oxygenation37 39. 

Cubeddu R., Pifferi A., Taroni P., Torricelli A., Valentini G., Compact tissue oximeter based on dual-wavelength multichannel time-resolved reflectance, Appl. Opt. 1999 38 3670. 

Respiratory alkalosis is associated with low partial pressure of02 (25 to 35 mm Hg) and alkaline pH, but normal bicarbonate. The first two values are measured by arterial blood gas, which also yields partial pressure of carbon dioxide and arterial oxygen saturation. Circulating arterial oxygen saturation can also be measured by an oximeter, which is a noninvasive method that is fairly accurate and useful at the patient s bedside. 

Figure 3. An example of frequency domain instrument. ISS, Inc. s oximeter model 96208.

Selecting an approach If available, a CO-Oximeter, an instrument used to test human blood by measuring its UV-Visible light spectrum, would be ideal. If unavailable, a standard UV-Vis will be used. 

Interpretation/report The spectra of the two different blood samples are different (Fig. 21.12). The Oximeter, though calibrated for human blood, indicates 60-70% of the hemoglobin in the fish from the fish kill is carboxyhemoglobin. The control fish showed less than 10%. Human fatalities have carboxyhemoglobin levels above 30% ... 

There are a number of equations and definitions associated with the principles behind the working of the pulse oximeter. 

In the pulse oximeter, the concentration and molar extinction coefficient are constant. The only variable becomes the path length, which alters as arterial blood expands the vessels in a pulsatile fashion. 

The pulse oximeter is a non-invasive device used to monitor the percentage saturation of haemoglobin (Hb) with oxygen (Spo2). The underlying physical principle that allows this calculation to take place is that infrared light is absorbed to different degrees by the oxy and deoxy forms of Hb. 

Anesthetic techniques that have minimized adverse effects include the use of muscle relaxants and, more recently, nerve stimulators to assess adequacy of relaxation, the introduction of very rapid acting, short-duration barbiturates, and the use of atropinic agents to minimize the cardiovascular response to a combination of a seizure and anesthesia (93). In addition, 100% oxygenation (adequacy monitored by a pulse oximeter) with positive-pressure ventilation can minimize related cardiac events and memory disruption. 

Which estimate of goodness is more important Well, both of them are important. It is important to you and your patient that the reading on a pulse oximeter accurately represents the patient s blood Por Likewise, you won t have confidence in a pulse oximeter if it gives a different reading every time you look at it (assuming the patient s condition has not changed). 

A pulmonary artery (Swan-Ganz) catheter can be used to determine central venous pressure (CVP) pulmouary artery pressure CO aud pulmonary artery occlusive pressure (PAOP), an approximate measure of the left ventricular eud-diastolic volume aud a major determinaut of left veutricular preload. CO (2.5 to 3 L/min) and mixed venous oxygeu saturatiou (70% to 75%) may be very low in a patient with extensive myocardial damage. Respiratory alkalosis is associated with low partial pressure of O2 (25 to 35 mm Hg) and alkaline pH, but uormal bicarbouate. The first two values are measured by arterial blood gas, which also yields partial pressure of carbon dioxide and arterial oxygen saturation. Circulating arterial oxygen saturation can also be measured by an oximeter, which is a noninvasive method that is fairly accurate and useful at the patient s bedside. 

Sigma London Chemical Co Ltd, Poole, Dorset, UK Co-oximeter, IL 282 for the determmation of carbon... 

Constantino, A.G., Park, J., Caplan, Y.H. (1986). Carbon monoxide analysis a comparison of two CO-oximeters and headspace gas chromatography. J. Anal. Toxicol. 10 190-3. 

Oxygen levels were regularly measured in samples taken from the bioreactor by means of a portable oximeter, to maintain the oxygen inside the bioreactor at 2-A mg O2/L. The exit stream of the reactor is impelled to the membranes by a centrifugal pump located at the exit (see Figure 41.2), at a rate of 56 m /h at 4 bar. 

Lin et al. examined the influence of fat layers on the determination of blood oxygenation in 1998 [26]. The phantom experiments showed fat influences patient-to-patient measurements. This is more easily compensated for in any individual patient. Yamamoto addressed the issue of fat interference with an oximeter that corrected for the influence of subcutaneous fat [27]. The wavelengths, again, were the key as was the algorithm. 

K. Yamamoto et al. Near-Infrared Muscle Oximeter that Can Correct the Influence of a Subcutaneous Fat Layer, paper 17, Proc. SPIE 3257 (Photonics West), San Francisco, January, 1998. 

L. C. Henson, C. Calalang, J. A. Temp, and D. S. Ward, Accuracy of a Cerebral Oximeter in Healthy Volunteers under Conditions of Isocapnic Hypoxia, Anesthesiology, 88(1), 58 (1998). 

Brunelle JA, Degtiarov AM, Moran RF, Race LA. Simultaneous measurement of total hemoglobin and its derivatives in blood using CO-oximeters Analytical principles their application in selecting analytical wavelengths and reference methods a comparison of the results and the choices made. Scand J Clin Lab Invest 1996 56,Suppl 224 47-69. 

Bohnhorst B, Peter CS, Poets CF. Pulse oximeters reliability in detecting hypoxemia and bradycardia Comparison between a conventional and two new generation oximeters. Grit Care Med 2000 28 ... 

Kwant G, Oeseburg B, Zijlstra WG. Reliability of the determination of whole-blood oxygen affinity by means of blood-gas analyzers and multiwavelength oximeters. Clin Chem 1989 35 773-7. 

---