Pulse Oximeters – Errors and Troubleshooting

While using a pulse oximeter, it is inevitable that errors and problems may sometimes occur. However, most of them can be fixed in a simple and effortless manner. Here are the common problems encountered when using a pulse oximeter and how to solve them.

Failure to obtain a signal

In order to get a reliable and continuous signal, the measuring site must be kept clean and dry. You may reposition the user’s finger. Sometimes, there might be a need to change the monitoring site. If this doesn’t solve the problem, the person’s vital signs should be assessed including the measuring site, whether there is adequate blood flow. The sensor and a blood pressure cuff must not be placed on the same hand. In addition, check for loose wirings or whether the probe is properly attached to the base unit that should be connected to a power source.

Alarm Problems

A common problem encountered when using a pulse oximeter is that the alarm keeps setting off, which is more annoying than useful. This typically occurs when the set is not motion-resistant and excessive movement can trigger the alarm. Check your device manual for this feature. The best way to deal with this is to assess the patient for any other cause of the problem, as well as the device. Some alarms may be turned off, but that is not really helpful as alarms warn you whether the patient is already hypoxic. You may set the alarm limits according to you facility’s policy.

Error Messages

Many pulse oximeters can display on their screen certain error messages. Read the user’s manual in order for you to familiarize these messages and the appropriate troubleshooting steps. Some units may already display troubleshooting tips on its screen.

Erroneous Readings

There are a variety of reasons why a pulse oximeter obtains erroneous readings.

• Room temperature may be one of the reasons behind such. Refer to the user’s manual about appropriate room temperature for optimal functioning.

• Venous pulsation brought about by tricuspid regurgitation or pulmonary hypertension and a tight finger probe may cause erratic SpO₂ readings.

• Additionally, compromised blood flow to the monitoring site may also cause problems. Although many monitors nowadays are equipped with the latest digital signal technology that can detect oxygen saturation even when there is low perfusion, the patient should still be assessed for the cause of blood flow restrictions such as blood pressure cuffs and tight restraints. Check the actual pulse rate from the pulse rate that is being displayed on the unit. If the rates don’t match, the saturation reading cannot be considered accurate. Reposition the probe or change the measuring site as necessary.

• Medical conditions such as elevated carboxyhemoglobin and methemoglobin levels may cause a falsely high oxygen saturation reading. In such scenarios, refer the condition with the physician. A pulse CO-oximeter may be replaced.

Refer to the user’s manual for more troubleshooting tips.

Pulse Oximetry in Dentistry

Like surgery, some dental procedures also require anesthesia administration to promote a convenient and painless operation on the part of the patient. Some clients, especially those who have phobias, prefer to be administered with a sedative to alleviate their anxiety and make them calm throughout the entire procedure.

Sedatives are a class of drugs known to cause calming, relaxation, and oftentimes unconsciousness. In dentistry, the effects of sedatives are reduced to a minimum so that the patient is simply relaxed, on a sleep-like state, but still awake. However, on some scenarios, a patient may be given moderate to deep sedation based on his level of anxiety. The drugs for sedation dentistry may be swallowed, injected intravenously, or inhaled. Many have benefitted from sedation dentistry that’s why it is becoming more popular in clinics.

During sedation, significant desaturation periods may occur, particularly in children. This poses a risk of hypoxemia which is recognized as a serious complication. Hence, a pulse oximeter may prove useful to detect early signs of hypoxemia and respiratory depression.

A pulse oximeter is considered to be a very reliable and a very sensitive tool in identifying low blood oxygen saturation, which is why doctors and surgeons prefer oximetry for continuous monitoring or even periodical assessment of a patient’s status. It measures the saturation of oxygen in a person’s blood to detect whether it is still under normal concentrations. They are typically found in hospitals and operating galleries where anesthesia is more likely to cause respiratory depression. It is also proper to use a pulse oximeter during dental procedures because of the possibility of hypoxemia.

The choice of a pulse oximeter for dentistry should consider probable interferences such as excessive movements brought about by high levels of anxiety. The solution is to pick a type that is portable and motion-resistant. There are also devices that are built for pediatric use while others have added features such as a pletysmograph display, and blood pressure monitoring. There are models of pulse oximeters, but generally they are categorized as fingertip, handheld, and stationary type. Both fingertip and handheld pulse oximeters are commonly found in ambulatory settings because of their low cost but equally excellent results.

Pulse Oximetry Today

More than a decade ago, operating rooms and post-anesthesia care units (PACU) were the common places to encounter the bulky type of pulse oximeters. It was necessary to monitor the SpO2 or the oxygen saturation of the patient’s blood due to a fatal complication of hypoxemia following anesthesia administration. Unlike arterial blood gas which are highly invasive and quite a painful procedure for patients, pulse oximeters are more preferred due to their non-invasive nature and capability of continuous monitoring and accurate results.

But the potential value of pulse oximetry in the care of various cases wasn’t realized until the later part of the 20th century when the microprocessor was developed and sensors were improved. This allows for the invention of a smaller, more convenient yet equally durable pulse oximeter.

Virtually any patient can benefit from the use of pulse oximeters. For this reason, almost every health care facility is required to possess this important tool in the assessment of pulmonary status of a person, or even for intermittent diagnostic testing. It allows physicians to look beyond what the human eye cannot see. Nowadays, with the expansion in its clinical application, pulse oximetry has evolved into a cost-effective, handy equipment capable of the same functions of a conventional oximeter.

A handheld pulse oximeter is composed of a probe that is attached to a part of the patient’s body, usually the fingertip, earlobe, or foot (for neonates), and an LCD screen where the results can be read. Various probes can be used with this device—infant, older children, adult, or even disposable probes depending on the demand. The handheld model is designed either for spot checks or continuous monitoring that can be applied in almost any setting. Its size and simplicity makes it favorable for use even by non-professionals.

Several brands and companies have produced their own version of a handheld pulse oximeter, adding up features such as a waveform display of the pulse rate, device to pc data transmission, extended hours of storage, and perfusion index. However, these add-ons are only optional. The most important part is still the clean transmission of light from the probe as well as the data processing within the unit in order to produce accurate data.

Finger Pulse Oximeter

If you’re concerned with the cost pertaining to the purchase of a pulse oximeter, then a portable fingertip device would probably suit your needs. It’s basically the same—it can measure your pulse rate and oxygen levels, without the hassle of carrying a base unit with you. It’s virtually the perfect tool for monitoring your condition while going on with your daily activities.

There are loads of units in the market which you can select from—pediatric oximeters, adult oximeters, or even for sports applications. Generally, it is portability of the device that makes it a popular choice for home or outdoor use.

There are a lot of reasons why a person would want to purchase a pulse oximeter. Firstly, a finger pulse oximeter can help you track your health. People with chronic respiratory conditions may struggle from shortness of breath and sometimes leading to low oxygen levels in the blood, such as in the case of asthma. In some cases, these people have to bring along with them such equipment and track their oxygen levels as insufficient oxygen could be fatal.

Athletes and mountaineers may also use such portable device because of the nature of their activities. Furthermore, climbing at a higher altitude would mean a decreased amount of oxygen in the atmosphere. This is also the reason why pilots in non-pressurized cabins should also wear finger oximeters to monitor their oxygen levels from time to time.

This type of oximeter can also be used to help diagnose obstructive sleep apnea (OSA). The patient will have to wear the device overnight as it continuously records your oxygen levels. The results are downloaded to a computer for analysis and the physician will use this data to confirm a diagnosis. In doing such, the need to sleep in overnight clinics is eliminated thus lowering your expenses.

Which Pulse Oximeter Should You Choose?

Pulse oximetry has been a standard method in clinical practice for the measurement of oxygen saturation as it shortens the time required to detect hypoxemia. In choosing such a device the features and options you would require would depend on the condition and the setting to which the device will be used.

Hospitals and Clinical Practice

The most commonly employed pulse oximeter in hospitals and ambulatory settings are stationary and handheld pulse oximeters. They are the bulky ones that are located by the bedside. It consists of a typical probe (either a Y-sensor probe, or a fingertip clip) that is wired to a bulky base unit. The base unit does the calculations over the difference in light absorption between oxygenated and deoxygenated blood. They are much preferred due to their cost-effectiveness and large displays that enables the health worker to see the results clearly from a distance. A great example is the Nonin 7500FO, a powerful and reliable digital oximeter that is compatible with many types of sensors (probe), and large visualization.

Home Monitoring

If you plan to use a pulse oximeter by yourself, find a type that is easy to manipulate. You would not want to take a manual with you every time you use the device. Finger pulse oximeters are the most common types purchased for home or outdoor use because of its user-friendly interface and superior portability.

Should there be a need for remote monitoring, wireless pulse oximeters would suit you best. They come with a special capability to transmit data using Bluetooth technology and upload the information to the physician’s clinic via a central notification system.

Probes

There are probes that are only for single-use while there are also some that are reusable. A certain type of probe called a Y-sensor probe can be applied to various sites ranging from fingers, toes, palm, and soles, which can be used for pediatric and adult patients.  In some cases, pediatric patients may need a special motion-resistant feature to produce more reliable results.

Introduction to Pulse Oximeters

For the assessment of respiratory function, it is not uncommon to come across that small device that is clipped to one of your fingertips or earlobe called a pulse oximeter. Generally, the primary purpose of this gadget is to provide an estimate of the oxygen saturation of hemoglobin that cannot be easily detected by physical assessment and the human eye.

The respiratory status of a person may be evaluated through a variety of ways. But diagnostic studies are more accurate. For one, pulse oximetry can give a fast and accurate way of monitoring a patient’s oxygenation. Prior to its development, a patient’s oxygenation can only be determined through arterial blood gas measurements which requires a few minutes for the results to come out. Although ABGs convey very accurate and reliable results, this procedure is usually not considered in situations that require immediate and continuous observation of oxygenation. The pulse oximeter is a safer, noninvasive option which makes it ideal for continuous monitoring. It does not replace arterial blood gas studies, but it is an effective tool to keep an eye for sudden changes in blood oxygen saturation. It can be used in any setting where oxygen saturation monitoring is required such as the hospital, during surgery, and at home.

The pulse oximeter operates based on the principle that red and infrared light absorption varies depending on the color between oxygenated and deoxygenated blood. A sensor is attached to a thin portion of the patient’s body, such as the fingertip or earlobe, and detects the light signals that are reflected by blood present at these sites. However, the device also has its own limitations. Sometimes, the values obtained may be unreliable especially when the patient has severe anemia or a high carbon monoxide level. Thus, it is really a must for both health workers and patients/users to use the pulse oximeter wisely and assume certain responsibilities to monitor its efficiency.

Wireless Pulse Oximeter

In the recent years, there has been a growing necessity for monitoring disease processes remotely. Pulse oximeter systems have undergone a lot of changes as manufacturers strive to improve the quality and accuracy of the data displayed to the users. With the integration of wireless technology to pulse oximetry, a person’s status and condition can now be monitored by the physician as they go about their daily lives.

Bluetooth Wireless Pulse Oximeter

Pulse oximetry has been one of the standard patient monitoring devices in hospitals mainly because of its continuous monitoring system and accurate results in the measurement of oxygen saturation in the blood.  However, because of their size, weight, and attachment, stationary pulse oximeters in the clinical setting makes it troublesome for patients in terms of mobility. Fortunately, as years pass by, pulse oximeters are becoming smaller, more portable, and easy to use. Wireless pulse oximeters are a new type of telemetry units developed to address this problem.

Wireless pulse oximeters transmit data continuously via Bluetooth wireless technology. The data that is shown to the user can also be directed to a central tracking system. For this reason, the device is ideal to use for distant respiratory monitoring and home sleep apnea screening.

The device typically consists of a probe than can be worn on the fingertip or the earlobe. It collects real-time data from the sensors inside, reads it, and sends it to any device with Bluetooth technology such as a laptop. The data can be submitted to a central monitoring system via the Internet which makes it great for home and outdoor use.

Unlike conventional stationary models, wireless pulse oximeters have many advantages. Its lightweight design and superior portability makes it more convenient to use. It also has an exceptional battery life that can help reduce the cost brought about by energy consumption by large bulky units. Information exchange has never been easier with Bluetooth-enabled technology.

Pulse Oximiter – Clinical Applications

Clinical Importance

Since its discovery in the 1900s, pulse oximeters have been widely used for the monitoring of patients suffering from cardiac and respiratory diseases such as chronic obstructive pulmonary disease, severe chronic asthma, cystic fibrosis, chronic heart failure, and pulmonary hypertension. The device provides a very safe, easy, and non invasive approach for continuous monitoring of the oxygenation status of a person. For this reason, this method is deemed to be ideal for the care of patients under critical conditions, both pediatric and adult.

The clinical significance of the pulse oximeter is greatly appreciated because of its highly accurate and immediate results that help health workers identify those persons requiring close monitoring especially during patient transport and narcotic administration.

With the introduction of the pulse oximeter, hypoxia related to the administration of anesthesia can be easily detected, thereby reducing the mortality rate secondary to this condition. In newborns, oxygen toxicity has been one of the major reasons for the development of an eye disease called retrolental fibroplasia or retinopathy of prematurity that could possibly lead to blindness. But now, the oxygen levels in neonates can already be monitored to prevent under and over administration hence, lowering the risks.
Measuring blood oxygenation with pulse oximetry also reduces the need for invasive procedures, such as drawing arterial blood for arterial blood gas analysis of oxygen levels.

Other Uses of Pulse Oximeters

While the application of pulse oximeters in the clinical settings is considered very valuable, apparently, its use outdoors has also been growing over the past years. Hence, measurement of oxygen saturation in the blood is not only confined within the four corners of the hospital.

Portable pulse oximeters such as the handheld and fingertip type have been very useful for pilots operating in a non-pressurized aircraft where supplemental oxygen is required. Athletes and sports buffs have also found the device very useful in checking their blood oxygen level during exercise. They just want to know how they are doing with their training without compromising their health. Low blood oxygen levels (hypoxemia) are extremely life-threatening—it can cause irreversible brain damage within minutes, or worse, death.

Understanding Blood Oxygenation and Circulation

Almost every living organism on the face of this planet relies on the presence of oxygen to fuel their vital processes. In humans, the distribution of oxygen to the tissues is facilitated by the circulatory system.

Oxygen Transport

By assisting in the process called respiration, the blood provides the body cells an effective delivery and disposal system and helps maintain the normal function of cells. Oxygen inhaled by the person from the atmosphere is transported to the body’s tissues by doughnut-shaped red blood cells found in the blood. These red blood cells contain hemoglobin, a substance that takes up oxygen as blood passes through the lungs and releases it into the cells. In turn, it also picks up carbon dioxide for removal. Oxygenated blood is bright red because the hemoglobin portion of the red blood cell is bound with oxygen. Deoxygenated blood has a darker shade of red.

Our cells need a constant supply of energy to power their activities. Likewise, they also need oxygen and utilize it to release energy. When there is an imbalance or interruption in the supply of oxygen in the body, a person may develop conditions that could greatly affect his/her health.

A pulse oximeter measures oxygen saturation based on the light signals that are reflected by pulsating blood at the site of the sensor. It has both red and infrared LEDs as light emitters because oxygenated blood has a different absorption rate for these wavelengths. Inside the device, the red to infrared ratio is calculated and converted to an SpO2 value. Normally, the saturation of peripheral oxygen (SpO2) or the amount of oxygen dissolved in the blood is at around 95-100%. Values lower than 90% is called hypoxemia or a low oxygen level in the blood. This condition indicates that the body is not receiving enough oxygen, and the person requires immediate and further evaluation.

Fetal Pulse Oximetry

Oxygen saturation monitoring does not only apply to infants and adults. In some special cases, even the unborn may need constant monitoring.

The Procedure

Intrapartum oxygen saturation monitoring or fetal oxygen saturation monitoring is an examination performed to assess the well-being of the baby during the early course of labor. This is done by a doctor or a midwife who will insert a catheter-like probe inside the vagina during labor. The catheter should lodge on the face, particularly the cheek or the scalp of the fetus to get a good reading. It may take a few minutes and cause minor discomfort during the insertion. And in most cases, fetal pulse oximetry is done along with an internal fetal monitoring device.

The Device

Fetal pulse oximetry is a relatively new technique in the assessment of a fetus prior to delivery. It has been useful in reducing the number of caesarean sections because of the immediate availability of its results.

The probe transmits specific wavelengths of light to determine the amount of oxygen beneath the baby’s skin. It functions like a fetal scalp electrode that is hooked to an external monitor that reads the data gather from the reflected lights. It measures both the pulse rate and oxyhemoglobin saturation and puts in on display. The data may also be recorded for future reference. Most importantly, the probe should be lodged securely to the skin to get an accurate reading. The physician will provide an objective reading of the results in line with the fetal heart tracing. Should there be any abnormalities in the baby’s oxygenation, he may decide to proceed with a cesarean delivery.

The procedure, however, because of its recent development, studies are yet to be conducted in terms of the reliability of its results. So far, the parameters for false positive and false negative readings are still not available.

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