![]() Pulsating blood is another prerequisite for an accurate reading. It should be avoided by covering the site or the probe. Light pollution into the sensor part of the probe can be another interfering factor to an accurate reading, such as certain ambient light or other probes emitting light in a similar spectrum in the vicinity of the pulse oximeter probe. Some newer pulse oximeters using multiple wavelengths can display some methemoglobinemias. In that case, a confirmation with a Co-oximeter should be obtained. Äyshemoglobinemias, such as carboxyhemoglobin, methemoglobin, and others, will change the color and absorption spectrum of blood and give false readings. Intravenous dyes such as methylene blue or indocyanine green that are sometimes used for surgical or diagnostic procedures will color the serum in the blood and may interfere with the light absorption spectrum and give low readings. Pulse oximeters can be less accurate at cold temperatures. Warm site temperature (about 33☌) should be maintained for reliable readings. Patients with dark skin may have their oxygen saturation overestimated by ~2%. Placing the sensor sideways on a finger that does not give a reading has sometimes been used with success, but it should be remembered that this will be outside the calibration of that sensor. Because of the ever-changing fashion trends, it will be difficult to make a general statement which nail treatments will be safe and should ideally be avoided. Artificial fingernails have also been reported as either detrimental or having no effect. Numerous publications have covered this topic, but with varying conclusions implicating mostly blue or black colored nails. One of the common examples of interfering factors is nail polish and artificial fingernails. Therefore factors that interfere with those parameters can interfere with the reading of pulse oximeters. Pulse oximetry relies on light absorption through a tissue bed with pulsating blood. However, the critical numbers that require treatment may be lower at high altitude or in patients with hypoxic heart defects where venous blood get mixed with arterial blood going into the systemic circulation. Critical findings that would prompt intervention for most patients would likely be in the mid to high 80% range at sea level as the partial pressure of oxygen would be in the 60 mmHg range. ![]() There are some technical reasons for the 70% calibration however, by that time, the patients usually have clinical signs of hypoxemia that would not need invasive clinical confirmation and treatment to reverse that level of hypoxia would not differ from the treatment for a patient with a saturation of 70%. While they may not demonstrate absolute accuracy, they usually still track the oxygen saturation and display lower numbers. Pulse oximeters are usually calibrated to a range of saturation from 70% to 100% with an accuracy of 2% to 4%, which means that pulse oximeter is reading lower than 70%, may not be accurate compared to the gold standard invasive blood gas measurements. Normal individuals living at higher elevations may have lower oxygen saturation levels. Oxygen saturation levels around 96% to 100% are considered normal at sea level. However, most of those consumer-grade devices have not been evaluated by the Food and Drug Administration to diagnose or treat diseases. Because of the size and low cost of these consumer grade models, many patients with chronic respiratory illnesses are purchasing these to titrate either their medications or oxygen flow at home. In addition to hospital-grade pulse oximeters, newer and much smaller consumer-grade models are rapidly gaining popularity in the sports, private aviation, mountain climbing, and other recreational activity communities. Since its widespread use in hospitals, the incidence of unrecognized desaturations has decreased significantly. It is a standard monitor for all anesthesia cases in most developed countries and also used in emergency departments, hospital wards, and ambulances to assess blood oxygenation in patients with respiratory difficulties or monitor for respiratory depressant effects of pain medications. Deoxygenated and oxygenated hemoglobin absorb light at different wavelengths (660 nm and 940 nm respectively), and the absorbed light is processed by a proprietary algorithm in the pulse oximeter to display a saturation value. Pulse oximetry is a non-invasive monitor that measures the oxygen saturation in the blood by shining light at specific wavelengths through tissue (most commonly the fingernail bed).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |