25-05-2012, 05:49 PM
CLINICAL USE OF PULSE OXIMETRY
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THE PURPOSE OF THIS GUIDE
Chronic respiratory diseases such as COPD and asthma are among the most common health
conditions seen in primary care practices, affecting more than 1 billion patients worldwide.
Primary care clinicians are also often the first point of contact for patients suffering from
acute respiratory infections such as influenza and pneumonia. These health care professionals
need tools to help them evaluate, monitor, and decide when to refer patients with respiratory
conditions.
Pulse oximetry is a technology that enables the noninvasive measurement of oxygen
saturation, contributing to this measure’s rapid acceptance as a “fifth vital sign” (in addition to
temperature, blood pressure, pulse, and respiratory rate) in clinical assessment. Although the
technology has been available since the 1970s, recent advances have reduced the size and cost
of pulse oximeters, and as a result these devices (Figure 1) are becoming increasingly used in
respiratory patient monitoring in specialty and primary care practice.
In most countries, oximeters are only sold to patients under the guidance of a licensed health
care professional, and use by patients should be supervised by their physicians or other
qualified health care provider. Incorrect or inappropriate use of oximeters will not provide
useful information, and they should be used as part of a broader clinical assessment and not in
isolation.
BACKGROUND AND PRINCIPLES OF PULSE OXIMETRY
Pulse oximetry is a noninvasive method that enables rapid measurement of the oxygen
saturation of hemoglobin in arterial blood. [1] It can rapidly detect changes in oxygen
saturation, thus providing an early warning of dangerous hypoxemia. [2, 3]
The use of pulse oximetry for patient assessment and monitoring is well established in
critical care, anesthesiology, and emergency departments. [2] In recent years, the availability
of small, user-friendly, portable and affordable pulse oximeters, including those worn on
the finger-tip has opened up the potential for use of this technique in an expanded variety
of clinical settings, including primary care.
CURRENT CLINICAL USES OF PULSE OXIMETRY
A small but growing body of research, detailed in Table 2, is establishing the usefulness of
pulse oximetry in primary care, particularly—but not exclusively—for the management of
acute and chronic respiratory disease.
In patients with COPD, pulse oximetry is useful in stable patients with severe disease
(FEV1 < 50% predicted), and in patients with worsening symptoms or other signs of an
acute exacerbation, as a tool for patients to use at home to assist with their management
under physician guidance. It is important to note that pulse oximetry complements, rather
than competes with, spirometry in the assessment of COPD patients. Spirometry remains
the gold standard for diagnosing and staging COPD, while pulse oximetry provides a
method for rapid assessment especially of short-term respiratory compromise.
LIMITATIONS OF PULSE OXIMETRY
Despite recent technological improvements, pulse oximeters have some limitations that can
affect the accuracy of the measurement. Clinicians should be aware of certain situations
where the oximeter reading may not be accurate (Table 3).
In addition, some patients with severe chronic lung disease experience hypoxic drive, in
which respiration is driven by low oxygen levels rather than elevated carbon dioxide levels.
These patients often have severe disease and may already be on long-term oxygen therapy.
This condition does not affect the accuracy of pulse oximetry readings, but it does affect
the goals of monitoring and treatment.