Patient Monitor and its Application

• Patient monitor usually is a highly intelligent device,which includes mainframe, display, keyboard, recorderand varies sensors & cables.
• It integrates functions of measuring, recording and alarming together, which are very important and helpful for patient status analysis.
• It can measure and record patient’s vital signs of ECG, blood pressure, respiration, temperature, and SpO2 in real time, continuously and non-invasively.
• It can be widely used in many clinical sites such asoperating room, emergency department, ICU/CCU, etc..

About Pluse Oximeter

1. The importance of Oxygen to the human body

• Oxygen was inspired and get into blood via gases exchange in lung
• emoglobins ( Hb) were oxygenated and brought the oxygen to the organs cells
• Hb + O2 = HbO2 (Oxygenation)
• Arterial blood contains more HbO2 and Venous blood contains less HbO2

2. What is SpO2?

A blood-oxygen saturation reading indicates the percentage of hemoglobin molecules in the arterial blood which are saturated with oxygen. Readings vary from 0 to 100%. Normal readings in a healthy adult, however, range from 94% to 100%.

Blood oxygen saturation = HbO2/(HbO2+Hb)
SaO2--- Arterial blood oxygen saturation
SvO2--- Venous blood oxygen saturation
SpO2--- Pulse oxygen saturation, equals to SaO2
When arterial oxyhemoglobin saturation is measured by an arterial blood gas it is referred to as SaO2. When arterial oxyhemoglobin saturation is measured non-invasively by pulse oximeter, it is referred to as SpO2

History of Pulse Oximeter

• Oximetry measurements can be traced to the early 1930’s when German investigators used pectrophotometers to research light transmission through human skin. In 1934, one investigator reported measuring oxygen saturation in blood flowing through closed vessels in animals
• In 1964, a San Francisco surgeon developed a self-calibrating, 8- wavelength oximeter that was marketed by Hewlett Packard in the 1970’s.
• This system was used in clinical environments but was very large, weighing approximately 35 lbs., and had a bulky, clumsy earpiece.
• The unit was also very expensive (approximately $10,000.00). However, it did allow for continuous noninvasive monitoring of arterial oxygenation
• In the early 1970’s, Takuo Aoyagi (Japanese), found that light transmitted through the ear exhibited pulsatile variations. He recognized that it might be able to use the pulsating changes in the light transmission through the ear to measure arterial oxygen saturation.
• He then went on to develop a pulse oximeter and applied for a Japanese patent.
• At the same time, another Japanese researcher with Minolta was working on the same concept and applied for a patent a month later. This patent was denied in Japan but approved in the U.S.
• In the late 1970’s, the Biox Corporation in Colorado made significant advances in pulse oximetry, 2-wavelength measurements. They first introduced the use of Light Emitting Diodes (LED’s) for the red and infrared light sources.
• Ohmeda Corporation purchased Biox, and in the 1980’s, along with Nellcor, and Novametrix, ontinued to make significant advances in size reduction, cost, and development of multiple site probes
• Today there are many manufacturers of pulse oximeters. All offer a variety of different oximeter boxes with SpO2 and pulse rate readings, waveform displays, alarms, etc.
• While the boxes and the displays may differ, they use a similar method of measuring oxyhemoglobin saturation by two wavelengths of light in the red and infrared range.
• While the two-wavelength method is used to start the SpO2 measurement process, the way the signals are processed after that point, play a major role on how accurate the readings will be, especially through motion and low perfusion.
• During the late 1990’s and into the next decade, ‘new generation’ pulse oximeters have been introduced that have elevated the accuracy of pulse oximeter readings significantly.