WELCOME
2013 PROMOTION
Weekly Special
2013 COPD Special
Finger Oximeters
HandHeld Oximeters
HandHeld ECG
Info On Pulse Oximetry
Contact Us
   
 

   Special discount for COPD Patients

We are arranging Special discount on our FDA and Health Canada License approved Pulse Oximeters for  COPD Canada members  and other COPD organization members. You may get more useful information to improve your health from The Lung Association.

Yes, we ensure best offers to COPD patients and for C$2.00/each unit sold to COPD patients in Canada and USA, we will make donations to COPD forcused non-profit organizations!

Living with COPD could be easier than before.


COPD Health Tips

What is a Respiratory Therapist?
Most people take breathing for granted. It's second nature, an involuntary reflex. But for the thousands of Americans who suffer from breathing problems, each breath is a major accomplishment. Those people include patients with chronic lung problems, such as asthma, bronchitis, and emphysema, but they also include heart attack and accident victims; premature infants; and people with cystic fibrosis, lung cancer, or AIDS. In each case, the person will most likely receive treatment from a respiratory therapist (RT) under the direction of a physician. Respiratory therapists work to evaluate, treat, and care for patients with breathing disorders. Learn more about this exciting profession from the AARC, the U. S. Department of Labor (just select your state for local information), and the National Bureau of Labor Statistics.

What is COPD?
Chronic obstructive pulmonary disease, or COPD, is an umbrella term for two respiratory illnesses -- chronic bronchitis and/or emphysema.[1] There are 16 million Americans who have been diagnosed with COPD, of whom 14 million have chronic bronchitis and 2 million have emphysema.[2] COPD results primarily from smoking tobacco.[3] Years of smoking cause damage to the airways in the lungs. This lung damage continues to progress with the use of tobacco.[4] Average current and former smokers will likely not notice or acknowledge symptoms for several years. Typically, they will begin noticing the first symptoms of shortness of breath when they reach their 40s.[6] However, earlier signs of COPD are often present. These include chronic cough and increased mucus production. Recognizing these early signs is important because lifestyle modifications, such as smoking cessation and avoiding respiratory irritants, can be made to prevent additional damage to the airways.[7] In technical terms, COPD is a slowly progressive disease that is characterized by a decrease in the ability of the lungs to maintain the body's oxygen supply and remove carbon dioxide.[8] As a result of this decrease in lung function, COPD patients alter their lifestyles because they become short of breath after minimal exertion. For example, instead of climbing a flight of stairs COPD patients take the elevator. Physical activities also take longer to complete. Lawn mowing that a COPD patient might have finished in 40 minutes only a year ago may now take an hour to do.

Pulse Oximetry InterpretationSynonyms

Oximetry, oxygen saturation check, oxygen sat check, exercise oximetry, oxygen titration by oximetry, oxygen saturation measured using pulse oximetry (SpO2), oxygen desaturation test

Contraindications

No contraindications exist.

Patient care/preparations

Standard pulse oximeter probes may be placed on fingers or earlobes of ambulatory patients. Some oximeters use reflectance probes that can be placed on the forehead. Fingernail polish should be removed, and peripheral circulation should be maximized by warming or by applying vasodilating cream, if necessary.

Test

Although widely used, the practice of assessing oxygen desaturation by pulse oximetry is poorly standardized. The principle of oximetry measurement by spectrophotometry, although improving, is not as reliable as many practitioners believe. One side of the oximeter probe acts as a light-emitting source, and the other side acts as a photodetector. The probe is placed on a finger or earlobe. A forehead reflectance probe may also be used. The relative absorption of red (absorbed by oxygenated blood) and infrared (absorbed by deoxygenated blood) light of the pulsatile (systolic) component of the absorption waveform correlates to arterial blood oxygen saturation.

Resting readings should be made for at least 5 minutes, and the stability of the reading should be characterized on the report. If a finger probe is used when standing, the hand should be placed on the chest at the level of the heart to minimize venous pulsation, which can falsely lower the reading. Correlation of the heart rate displayed on the oximeter with an ECG rate or a manually palpated pulse can help characterize the quality of the signal. Agreement within 5 or more beats per minute generally rules out significant motion artifact. Ideally, correlation of pulse oximetry saturation should be made with a measured oxygen saturation by multiple wavelength spectrophotometry on a simultaneously obtained arterial blood gas sample.

Results

Documentation of the type of pulse oximeter used, probe type, and probe site should be included on each report. The heart rate and SpO2 readings at rest should be reported.

When obtaining pulse oximetry readings during exercise, the type and intensity of exercise (eg, walking speed, duration of activity) along with the heart rate and SpO2 at the end of the activity should be reported. When desaturation is detected, the activity should be repeated with supplemental oxygen in place to demonstrate improvement in SpO2 values.

Pulse oximetry is often performed (though optional) in the setting of the 6-minute walk test, a standardized measure of functional exercise capacity.8 This test is a measure of the maximum distance the patient is able to walk in a hallway with a minimum of 100 feet marked in 5-foot increments. The patient is permitted to slow down or even stop, if required; however, the elapsed time counter continues during rest periods. This test should be performed while exercise oxygen needs are being adequately met with portable oxygen delivery. Borg dyspnea and fatigue scores are collected immediately after completion of the walk.

Interpretation

Interpretation of oximetry studies, while seemingly simple, generally is not possible without characterizing oximeter accuracy by correlating SpO2 with at least one simultaneously obtained arterial oxygen saturation (SaO2). Laboratories should characterize the average oximeter bias (SpO2 - SaO2) through pooled data to better understand the limitations of using the oximeter, but this does not eliminate the possibility that oximeter readings on individual patients may exhibit larger biases. While SpO2 readings greater than 95% make the probability of clinically significant hypoxemia unlikely, clinical suspicion of hypoxemia should initiate the examination of ABGs. The goal of titration of supplemental oxygen should be a stable SpO2 reading of 93% or higher. Arterial desaturation can be considered present when the pulse oximeter saturation falls more than 4% below the baseline reading.

The role of pulse oximetry in the Medicare guidelines for reimbursement for continuous supplemental oxygen therapy are demonstration of one of the following while at rest and breathing room air: PaO2 less than or equal to 55 mm Hg, SaO2 less than or equal to 88%, or SpO2 less than or equal to 88%.

If supplemental oxygen is prescribed at a flow rate of greater than 4 liters per minute (LPM), the results of a PaO2 or oxygen saturation (SaO2 or SpO2) taken on 4 LPM supplemental oxygen must be provided.

Patients may qualify for supplemental oxygen therapy reimbursement even if the PaO2 is greater than 55 mm Hg and the SaO2 or SpO2 is greater than 88% if one of the following conditions is met: (1) dependent edema due to congestive heart failure; (2) cor pulmonale documented by P pulmonale on an ECG or by an echocardiogram, gated blood pool scan, or direct pulmonary artery pressure measurement, and (3) hematocrit greater than 56%.

Technical considerations

Carboxyhemoglobin (CoHb) and methemoglobin (metHb) absorb light at the same wavelength as deoxyhemoglobin, causing a very significant overestimation of SaO2 when these are elevated. Pulse oximetry has other shortcomings. It does not provide information about the oxygen content of the arterial blood. Tissue hypoxia can exist when SpO2 is normal when anemia is present. Elevated levels of dysfunctional hemoglobins (CoHb, metHb) can cause significant overestimation of the actual SaO2.

Additionally, pulse oximetry does not address the adequacy of ventilation, which can be assessed only by evaluation of the partial pressure of carbon dioxide in arterial gas (PaCO2). Motion of the finger within the probe can cause a motion artifact secondary to equal rhythmic absorption of red and infrared light that most oximeters interpret as an SpO2 reading of 85%. Disposable finger probes fixed to the probe site with adhesive and fixed positioning of the probe site during walking can minimize this.

Pulse oximetry tends to overestimate SaO2. One reason for this is the fact that pulse oximetry expresses the percentage of oxyhemoglobin, typically without consideration for CoHb or metHb (see below). One pulse oximetry manufacturer now offers options that allow reporting of total hemoglobin, oxygen content, CoHb and metHb, but these are not yet in widespread use.

SpO2 = oxyhemoglobin/(oxyhemoglobin + reduced hemoglobin [rHb])

In contrast, spectrophotometrically determined oxygen saturation from an ABG sample expresses oxygen saturation as the percentage of the sum of reduced hemoglobin, oxyhemoglobin, CoHb, and MetHb.

SaO2 = oxyhemoglobin/(oxyhemoglobin + rHb + CoHb + metHb)

This significant difference generally results in pulse oximeters reporting an oxyhemoglobin value that is 2-3% higher than the spectrophotometrically determined oxygen saturation, even when the pulse oximeter is functioning perfectly.

While the accuracy of pulse oximetry generally is good in population studies (SaO2 - SpO2 <2%), SpO2 values in individual patients may show a much greater bias, even when dysfunctional Hb levels are normal. Anemia and polycythemia can cause greater oximeter overestimation. SaO2 from simultaneously obtained ABG determinations should be used to characterize oximeter bias in individual patients, although this is not commonly performed.

ABG determinations should be considered whenever the clinical suspicion of hypoxemia exists, even when the oximeter displays a value over the threshold of 88%. Finally, the shape of the oxygen dissociation curve causes the pulse oximeter to be inherently insensitive to mild hypoxemia because relatively large changes in PaO2 in the flat upper portion of the curve cause very small changes in blood SaO2.

Advantages of pulse oximetry include that it is noninvasive, simple, and can be used to evaluate trends (evaluation of oxygenation during exercise, sleep, during procedures).

Disadvantages of pulse oximetry include that it cannot be used to assess oxygen delivery (anemia) or adequacy of ventilation (PaCO2) and that accuracy is lessened in the presence of elevated dysfunctional hemoglobin levels (CoHb, metHb), with a tendency to overestimate SaO2 by an average of 2-3%.

Factors that influence the accuracy of pulse oximetry readings

Overestimation of SaO2 is possible with bright sunlight on the probe, fluorescent lights, operating room lights, infrared heat lamps, elevated CoHb, elevated metHb, anemia, and motion artifact if the actual SaO2 is less than 85%.

Underestimation of SaO2 is possible because intravascular dyes, such as methylene blue and indocyanine green, produce transient reductions in SpO2. Fingernail polish, increased venous pressures, and motion artifact if the actual SaO2 is greater than 85% also can cause underestimation of the SaO2.