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    PHONOCARDIOGRAPHY

    Phonocardiography is a procedure that graphically depicts heart sounds and

    murmurs on a strip chart recorder. It has been used since the early 1900s to visually

    display the vibrations emanating from the heart and great vessels during different

    phases of the cardiac cycle. Since the availability of Doppler echocardiography,

    phonocardiography is used less often)

    Phonocardiograms are used to confirm the clinical diagnosis of specific valvular

    disease; precisely time cardiac events; and make possible the distinguishing of extra

    sounds, splitting of sounds, and identification and classification of murmurs. It should

    be noted, however, that the phonocardiogram will not make cardiac events audible,

    but rather will display them visually, permitting precise timing and correct diagnosis

    (Figures 4.19 and 4.20).

    The human ear can detect sound vibrations in the range of 20 to 20,000 Hz and since

    most heart sounds are in the 20 to 500 Hz range, they are audible. However, since

    the human ear can hear more easily in the high frequency range, some of the sounds

    go undetected or are difficult to Interpret, Very low - pitched sounds produced within

    the chest are not detected as sound but rather as palpable vibration. During the

    course of the phonocardiogram, certain frequency ranges can be filtered out or

    amplified inorder to zero-in on specific sounds.

    FIGURE 4.19

    Phonocardiogram and carotid pulse tracing (CPT). The ECG is monitored on lead II (Lit) with the

    phono tracing obtained from the left sternal border. S, ~ first heart sound; S2 = second heart

    sound.

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    Technique of Phonocardiography

    After the patient is connected to the phonocardiography machine, the microphones

    are placed on the chest over the base and apex of the heart, and the sound recording

    is done. An M-mode echocardiogram can be done at the same time so that a

    comparison between auscultatory events and valve movements can be made.

    Pharmaacologic agents and physiologic measures are often used to bring about

    and/or accentuate heart sounds and murmurs. When the patient is asked to speed or

    slow his breathing pattern in order to make certain murmurs more evident, the

    inspiratory and expiratory cycles are marked off manually by the technician to

    provide a point of reference.

    Patient Preparation

    No physical preparation is necessary for a pphonocardiogram. The procedure should

    be explained to the patient.It should be stressed that extreme quiet is nessecary

    during the procedure. Also patients should be told that they may be given medication

    or asked to alter their breathing pattern during the procedure to enhance heart

    sounds or murmurs.

    FIGURE 4.20

    Phonocardiogram from a 60-year-old male with aortic stenosis. Demonstrates the crescendo-

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    decrescendo murmur during systole (SM). The ECG is monitored in lead II (LI1).

    NORMAL HEART SOUNDS

    Physical assessment remains a clinically important diagnostic tool in the

    evaluation of heart sounds and murmurs. Cardiac auscultation is perhaps one of the

    most challenging aspects of physical assessment. Heart sounds are transient

    vibrations thought to be secondary to sudden tension on the valve leaflets. Heart

    sounds originating from each particular, valve are usually recorded best from their

    respective auscultatory areas on the chest.

    A quiet environment is of fundamental importance in the detection of most cardiac

    sounds, especially those of high frequency that might otherwise go unnoticed.

    Proper use of a good quality stethoscope is also important. Although the stethoscope

    does not accentuate heart sounds, it does have a limited ability to filter out unwanted

    sounds and allow the examiner to focus in on a specific range of heart sounds.

    Desirable characteristics of a stethoscope include proper-fitting earpieces, tubing

    length of approximately 10 to 12 inches, double tubing (separate or encased), and a

    chest piece with a diaphragm and a bell. The diaphragm is used for listening to high-

    pitched sounds and should be held firmly on the chest wall. The bell is used for

    listening to low-pitched sounds and should be held with the lightest pressure

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    necessary to maintain skin contact. Firm pressure on the bell filters out the low-

    pitched sounds it is designed to detect.

    First Heart Sound

    The first heart sound, S1 occurs at the onset of systole. The sound itself is relatively

    high pitched and originates from vibrations produced after the closure of the mitral

    and tricuspid valves. The mitral valve component is louder than the tricuspid valve

    component due to the higher pressure on the left side of the heart. The mitral valve

    also closes a fraction of a second sooner than the tricuspid valve.

    The is heard best over the apex of the heart. Occasionally both components

    of S1

    (M1) = mitral valve component; T1 = tricuspid valve component) can be heard by

    placing the diaphragm of the stethoscope over the tricuspid area. This is called

    normal splitting of S1.

    Many factors can have an effect on the intensity of S1. The S1 is loudest when the

    mitral valve closes rapidly and when the mitral valve leaflets are widely separated at

    end-diastole. Some conditions that cause an increase in the intensity of S1 are

    tachycardia, rapid atrioventricular conduction (short PR interval), and hyperdynamic

    states such as exercise and fever that increase the force of contraction of the left

    ventricle. Mitral stenosis without calcification of valve leaflets is also associated with

    a loud S1. The intensity of S1 decreases when the atrioventricular conduction is slow

    (long PR interval) because the mitral valve is already partially closed at end-diastole.

    Decreased left ventricular contractility and mitral stenosis with calcification of valve

    leaflets are also associated with a soft S1.

    First heart sounds can vary in intensity and duration when the atria and ventricles

    are asynchronous, as in complete heart block, atria] fibrillation, and ventricular

    tachycardla. This is because leaflet separation and rate of closure In the mitral valve

    vary with eac h beat.

    It is sometimes difficult to differentiate S1 from S2 during rapid heart rates ie. as

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    systole and diastole approach equal duration. It is helpful to bear in mind that S1 is

    consistent with the apical impulse and just precedes the carotid impulse.

    Second Heart Sound

    The second heart sound, S2, occurs at the onset of diastole. The origin of the second

    sound is due to vibrations produced after closure of the aortic and pulmonic valves.

    The S2 is a high-pitched sound that is loudest at the base of the heart. The aortic

    valve component is louder than the pulmonic valve component and the aortic valve

    normally closes just before the pulmonic valve. This separation is augmented during

    active inspiration as pulmonic valve closure is delayed due to increased venous

    return to the right side of the heart. This normal splitting of the components of S2 (A2

    = aortic component; P2 = pulmonic component) is usually easily identifiable with the

    phonocardiogram and is frequently audible with the stethoscope.5 The components

    of the second heart sound are heard best over the pulmonic area with the diaphragm

    of the stethoscope. Erb's point is an area on the chest where many murmurs of aortic

    and pulmonic origin are transmitted (Figure 4.21).

    The S2 can also be abnormally split and is then termed paradoxical (reversed)

    splitting. It is heard characteristically during inspiration, with S2 occurring before A2.

    The most common cause of paradoxical splitting is left bundle branch block.

    Wide splitting of S2 occurs in situations where right ventricular systole is delayed, as

    in right bundle branch block, pulmonic stenosis, and left ventricular pacing. It is

    actually an accentuation of normal splitting. Wide splitting is most pronounced in

    inspiration and often present in expiration.

    Fixed splitting is manifested by wide splitting throughout the respiratory cycle with

    no change between inspiration and expiration. It occurs most commonly with atrial

    septal defect.

    The intensity of S2,can vary as well. Increased intensity of A2 is indicative of arterial

    hypertension. Aortic stenosis causes a decreased intensity of A2. Similarly,

    pulmonary hypertension causes the P2 to increase in intensity whereas pulmonic

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    stenosis causes the P2 to decrease in intensity.

    EXTRA HEART SOUNDS

    Third Heart Sound

    The third heart sound, S3, is an early diastolic sound. The sound is generated from

    vibrations produced during rapid filling of the ventricles in patients with ventricular

    dysfunctions and overfilled ventricles as in CCF. It can also be a normal variant in

    individuals up to 30 years of age. It is a low-frequency pitch that often can be

    detected on phonocardiogram when it cannot be heard at the bedside. For purposes

    of specific timing, it occurs approximately 0.15 second after A2. The S3 can be

    augmented in the left lateral decubitus position and in conditions where the venous

    return is increased. It is heard best at the apex with the bell. An S3 may also be

    heard over the lower left sternal border in patients with right ventricular failure.

    Fourth Heart Sound

    The fourth heart sound, S4, is a low-pitched, presystolic sound. It is secondary to a

    forceful atrial contraction into a ventricle that has decreased compliance. Chronic

    ischemia, ventricular hypertrophy, car-diomyopathy, and idiopathic hypertrophic

    subaortic stenosis are some of the conditions in which an S4 may be heard. The S4 is

    also easily detectable on the phonocardlogram. It occurs prior to the S1, and for

    timing purposes, about 0.14 second after the onset of the P-wave. Like the S3, it can

    be heard best at the apex in the left lateral decubitus position with the bell.

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    Summation Gallop

    The summation gallop is the triple sound complex that is heard during a tachycardia

    in individuals that have both an S3 and an S4. These two sounds fuse together at

    high heart rates to form a diastolic sound. This happens because atrial contraction

    and rapid ventricular filling occur simultaneously with rapid heart rates.

    Ejection Clicks

    Ejection clicks are high-frequency sounds that can immediately follow S1 They are

    frequently heard in pulmonary and systemic hypertension. Aortic ejection clicks are

    heard in aortic stenosis, aortic insufficiency, and aortic dilatation. These sounds are

    heard best at the apex. Pulmonary ejection clicks are heard in pulmonary stenosis

    and pulmonary hypertension and are heard best in the pulmonic area. Because of

    the timing of ejection clicks relative to the cardiac cycle, they can be mistaken for a

    split S1. The distinction can be made based on the location in which the "double

    sound" is heard. The split S1 is best heard over the tricuspid area.

    Clicks that occur in mid - to late-systole are related to the billowing of a mitral valve

    leaflet in mitral valve prolapse. Sometimes more than one click will be present. It is

    believed that these sounds are due to the chordae being pulled taut suddenly during

    systole when the mitral valve billows back into the left atrium. The intensity and

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    timing of a mid- or late-systolic click may vary with changes in position and with

    respiration. It is most easily detected with the diaphragm at the apex of the heart.

    Opening Snap

    Opening snaps are high-pitched sounds that occur upon opening of a stenosed mitral

    or tricuspid valve. The sound is thought to occur as a result of sudden tension on the

    partially open valve leaflets very early in diastole. Opening snaps closely follow A2

    and are heard best at their respective auscultatory areas with the diaphragm (Figure

    4.22).

    Pericardial Friction Rub

    A pericardial friction rub is a high-pitched, grating sound resembling the

    characteristic sound heard when using sandpaper. Some people compare it to the

    sound produced when a lock of hair is held in front of the ear and rubbed between

    the fingers. It occurs in pericarditis and may have as many three components. The

    pericardial friction rub Is usually heard best with the diaphragm at the right and left

    sternal border. It may be accentuated with the patient sitting up and leaning

    forward while holding his or her breath in exhalation.

    FIGURE 4.22

    Heart sounds and the cardiac cycle. Extra heart sounds are graphically depicted as they would

    appear in the cardiac cycle. Always be aware of the effect of splitting and timing on heart sounds:

    St = first heart sound; S2 = second heart sound; S3 = third heart sound;

    S4 = fourth heart sound; E = ejection click (early systolic); M = ejection click (mid systolic); L =

    ejection click (late systolic); OS = opening snap.

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    .0.20 sec

    -------Low frequency sounds ---------High frequency sounds

    MURMURS

    Murmurs are auscultatory events that have a longer duration than heart sounds. On

    the phonocardiogram they are recorded as a series of vibrations. (Figure 4.23).

    Murmurs occur because of turbulent blood flow that results from flow through

    stenotic or regurgitant valves, increased velocity of blood flow, decreased blood

    viscosity (e.g. anemia), flow into a dilated chamber, shunting of blood from a high-

    pressure chamber into a low-pressure chamber, or increased cardiac output (e.g.

    fever or exercise). Murmurs may occur in any part of the cardiac cycle and may be

    normal in some individuals. Often, however, they represent a specific dysfunction

    within the heart.

    Murmurs are evaluated according to their timing in the cardiac cycle, location, and

    Intensity. The Intensity of a murmur is objectively rated on a six-point grading scale;

    Grade 1 a very faint murmur that seems to fade in and out

    Grade 2 a soft but easily detectable murmur

    Grade 3 a moderately loud murmur

    Grade 4 a loud murmur that is associated with a thrill(palpable vibration)

    Grade 5 a very loud palpable murmur that is audible with the stethoscope

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    partly off the chest wall.

    Grade 6 a very loud palpable murmur that is audible with the stethoscope held

    off the chest wall

    FIGURE 4.23

    Murmurs.

    Graphic representations of how the indicated murmurs would appear on a phonocardiographicrecording. This list is not all inclusive and variations in timing within the cardiac cycle can befound among both systolic and diastolic murmurs (i.e., murmurs may be early, middle, or late inoccurrence). Often, certain murmurs will begin with a click or opening snap. In addition, the

    prefixes pan- or holo- are applied to those murmurs that persist throughout systole or diastole(e.g the holosystolic murmur of mitral insufficiency). Systolic murmurs are often described as

    producing a harsh or blowing sound (especially the pansystoiic regurgitant murmur of mitralinsufficiency); diastolic murmurs may assume a rumbling quality. More than one murmur mayalso occur, producing a combination of sounds.

    Heart murmurs are also classified as harsh, rough, blowing, rumbling, musical,

    or

    Machinery like. They may be high, medium, or low pitched, and they may be

    localized or radiate along the precordium. Finally, murmurs may be classified

    according to their intensity and may be diagrammed with a specific shape that

    represents that intensity. For instance, they may be diamond shaped (crescendo-

    decrescendo), progressively increase in intensity (crescendo), progressively decrease

    in intensity (decrescendo), or remain the same intensity throughout the duration of

    the murmur.

    Systolic Murmurs

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    Systolic murmurs may be classified as flow murmurs, ejection murmurs, or

    regurgitant murmurs. Ejection murmurs occur as blood flows forward through the

    semilunar valves during systole. Regurgitant murmurs occur as blood flows backward

    through an incompetent atrioventricular valve during systole.

    Flow MurmursFlow murmurs occur as a result of physiologic changes associated with increased

    cardiac output, such as those consistent with tachycardia and anemia, and fluid

    overload. They are the most common type of murmur and are not indicative of any

    type of heart disease.26 Flow murmurs are usually heard best at the base of the

    heart with the diaphragm.

    Pathologic Ejection Murmurs

    These murmurs are due to stenosis of the aortic or pulmonic valves. Aortic stenosis is

    the most common cause. The murmur of aortic stenosis is harsh and crescendo-

    decrescendo in nature. It is audible with the diaphragm in the aortic area and may

    radiate down the left sternal border or up into the carotid arteries.

    Regurgitant (Pansystolic) Murmurs

    Systolic regurgitant murmurs characteristically have a more even intensity and often

    last throughout systole (i.e., they are "pansystolic"). Pansystolic murmurs often

    obscure the first and second heart sounds. Mitral regurgitation represents the most

    common type of pansystolic murmur, which usually has a blowing quality. It is heard

    best with the diaphragm at the apex and may radiate to the axilla. In individuals

    with mitral valve prolapse, a late systolic mitral regurgitant murmur may be present.

    Blood flow from the left ventricle Intothe right ventricle in ventricular septal defect

    will also produce a pansystolic murmur . This is usually a loud murmur with an

    associated thrill that may be audible over most of the anterior precordium. Tricuspid

    regurgitation, although uncommon, is another cause of pansystolic murmurs.

    Diastolic Murmurs

    Diastolic murmurs always indicate some type of pathology. They are frequently of

    shorter duration than systolic murmurs and, therefore, are sometimes mistaken forextra sounds. The most common diastolic murmurs are those of mitral stenosis and

    aortic insufficiency (regurgitation). Other causes are tricuspid stenosis and

    pulmonary insufficiency. Diastolic murmurs are classified as either mid or early.

    The murmur of mitral stenosis is often difficult to hear. It is a low-pitched, mid-

    diastolic rumbling murmur heard best at the apex with the bell of the stethoscope. It

    is usually very localized and often it will only be audible with the patient lying in the

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    left lateral decubitus position.

    The murmur of aortic insufficiency is a high-pitched, blowing, early-diastolic murmur

    that is heard best with the diaphragm in the aortic area and sometimes down the left

    sternal border. This murmur maybe accentuated with the patient sitting up and

    leaning forward while holding his or her breath in exhalation. The Austin-Flint murmuris a mid-diastolic murmur found in patients with severe aortic insufficiency without

    mitral valve disease. The sound is produced by blood flow across a rapidly closing

    mitral valve. The murmur is usually pandiastolic and rarely accentuated just prior to

    systolic ejection.

    At times, the sounds of a murmur can be heard throughout both systole and diastole.

    Such murmurs are called continuous murmurs and may reflect a single event (as

    occurs in patent ductus arteriosus) or may be the fusion of two or more events that

    must be differentiated. Accurate assessment in this circumstance is made by

    considering the location, intensity, and character of the murmur (Figure 4.23). For

    example, the patent ductus normally closes shortly after birth, so its appearance in

    an adult individual is uncommon. The machinery like sound it produces is the result

    of turbulent blood flow between the aorta and the pulmonary artery and thus is best

    heard in the aortic or pulmonic region. However, the murmur combination of aortic

    stenosis and aortic insufficiency may be a real possibility in the older individual and is

    best appreciated in the aortic area or at the apex; these may be frequent radiation of

    the sound into the carotid arteries.

    Pulse oximetry is a non-invasive method allowing the monitoring of the oxygenation ofa patient's hemoglobin.

    A sensor is placed on a thin part of the patient'sanatomy, usually a fingertip orearlobe,or in the case of a neonate, across a foot, and a light containing bothred and infraredwavelengths is passed from one side to the other. Changing absorbance of each of the twowavelengths is measured, allowing determination of the absorbances due to the pulsingarteriablood alone, excluding venousblood, skin, bone, muscle, fat, and (in most cases)fingernail polish.[1] Based upon the ratio of changing absorbance of the red and infraredlight caused by the difference in color between oxygen-bound (bright red) and oxygenunbound (dark red or blue, in severe cases) blood hemoglobin, a measure ofoxygenation

    (the per cent ofhemoglobinmolecules bound with oxygen molecules) can be made.

    Contents

    [hide]

    1 Indication

    http://en.wikipedia.org/wiki/Non-invasive_(medical)http://en.wikipedia.org/wiki/Oxygenationhttp://en.wikipedia.org/wiki/Hemoglobinhttp://en.wikipedia.org/wiki/Anatomyhttp://en.wikipedia.org/wiki/Anatomyhttp://en.wikipedia.org/wiki/Fingertiphttp://en.wikipedia.org/wiki/Earlobehttp://en.wikipedia.org/wiki/Infanthttp://en.wikipedia.org/wiki/Infanthttp://en.wikipedia.org/wiki/Redhttp://en.wikipedia.org/wiki/Redhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Absorption_spectrahttp://en.wikipedia.org/wiki/Arteryhttp://en.wikipedia.org/wiki/Bloodhttp://en.wikipedia.org/wiki/Veinhttp://en.wikipedia.org/wiki/Veinhttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-0%23cite_note-0http://en.wikipedia.org/wiki/Absorbancehttp://en.wikipedia.org/wiki/Infrared_lighthttp://en.wikipedia.org/wiki/Infrared_lighthttp://en.wikipedia.org/wiki/Hemoglobinhttp://en.wikipedia.org/wiki/Hemoglobinhttp://en.wikipedia.org/wiki/Oxygenationhttp://en.wikipedia.org/wiki/Oxygenationhttp://en.wikipedia.org/wiki/Hemoglobinhttp://en.wikipedia.org/wiki/Hemoglobinhttp://toggletoc%28%29/http://en.wikipedia.org/wiki/Pulse_oximetry#Indication%23Indicationhttp://en.wikipedia.org/wiki/Non-invasive_(medical)http://en.wikipedia.org/wiki/Oxygenationhttp://en.wikipedia.org/wiki/Hemoglobinhttp://en.wikipedia.org/wiki/Anatomyhttp://en.wikipedia.org/wiki/Fingertiphttp://en.wikipedia.org/wiki/Earlobehttp://en.wikipedia.org/wiki/Infanthttp://en.wikipedia.org/wiki/Redhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Absorption_spectrahttp://en.wikipedia.org/wiki/Arteryhttp://en.wikipedia.org/wiki/Bloodhttp://en.wikipedia.org/wiki/Veinhttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-0%23cite_note-0http://en.wikipedia.org/wiki/Absorbancehttp://en.wikipedia.org/wiki/Infrared_lighthttp://en.wikipedia.org/wiki/Infrared_lighthttp://en.wikipedia.org/wiki/Hemoglobinhttp://en.wikipedia.org/wiki/Oxygenationhttp://en.wikipedia.org/wiki/Hemoglobinhttp://toggletoc%28%29/http://en.wikipedia.org/wiki/Pulse_oximetry#Indication%23Indication
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    2 History 3 Limitations 4 See also

    5 References

    [edit] Indication

    Pulse oximetry data is necessary whenever a patient'soxygenation is unstable, includingintensive care,critical care, and emergency department areas of a hospital. Data can alsobe obtained frompilots in unpressurized aircraft,[2] and for assessment of any patient'soxygenation inprimary care. A patient's need for oxygen is the most essential element tolife; no human life thrives in the absence of oxygen (cellular or gross). Although pulseoximetry is used to monitor oxygenation, it cannot determine the metabolism of oxygen,or the amount of oxygen being used by a patient. For this purpose, it is necessary to alsomeasure carbon dioxide (CO2) levels. It is possible that it can also be used to detect

    abnormalities in ventilation. However, the use of pulse oximetry to detect hypoventilationis impaired with the use of supplemental oxygen, as it is only when patients breathe roomair that abnormalities in respiratory function can be detected reliably with its use.Therefore, the routine administration of supplemental oxygen may be unwarranted if thepatient is able to maintain adequate oxygenation in room air, since it can result inhypoventilation going undetected.[citation needed]

    [edit] History

    In 1935 Matthes developed the first 2-wavelength ear O2 saturation meter with red and

    green filters, later switched to red and infrared filters. This was the first device tomeasure O2 saturation.[citation needed]

    In 1949 Wood added a pressure capsule to squeeze blood out of ear to obtain zero settingin an effort to obtain absolute O2 saturation value when blood was readmitted. Theconcept is similar to today's conventional pulse oximetry but suffered due to unstablephotocellsand light sources. This method is not used clinically. In 1964 Shaw assembledthe first absolute reading ear oximeter by using eight wavelengths of light.Commercialized by Hewlett Packard, its use was limited to pulmonary functions andsleep laboratoriesdue to cost and size.[citation needed]

    Pulse oximetry was developed in 1972, byTakuo Aoyagi, a bioengineer, atNihonKohden using the ratio of red to infrared light absorption of pulsating components at themeasuring site. Susumu Nakajima, a surgeon, and his associates first tested the device inpatients, reporting it in 1975.[3] It was commercialized by Biox in 1981 and Nellcor in1983. Biox was founded in 1979, and introduced the first pulse oximeter to commercialdistribution in 1981. Biox initially focused on respiratory care, but when the companydiscovered that their pulse oximeters were being used in operating rooms to monitoroxygen levels, Biox expanded its marketing resources to focus on operating rooms in late

    http://en.wikipedia.org/wiki/Pulse_oximetry#History%23Historyhttp://en.wikipedia.org/wiki/Pulse_oximetry#Limitations%23Limitationshttp://en.wikipedia.org/wiki/Pulse_oximetry#See_also%23See_alsohttp://en.wikipedia.org/wiki/Pulse_oximetry#References%23Referenceshttp://en.wikipedia.org/w/index.php?title=Pulse_oximetry&action=edit&section=1http://en.wikipedia.org/wiki/Oxygenationhttp://en.wikipedia.org/wiki/Oxygenationhttp://en.wikipedia.org/wiki/Intensive_carehttp://en.wikipedia.org/wiki/Intensive_carehttp://en.wikipedia.org/wiki/Critical_carehttp://en.wikipedia.org/wiki/Emergency_departmenthttp://en.wikipedia.org/wiki/Aircraft_pilothttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-1%23cite_note-1http://en.wikipedia.org/wiki/Primary_carehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Hypoventilationhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/w/index.php?title=Pulse_oximetry&action=edit&section=2http://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Photocellhttp://en.wikipedia.org/wiki/Photocellhttp://en.wikipedia.org/wiki/Sleep_laboratoryhttp://en.wikipedia.org/wiki/Sleep_laboratoryhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/w/index.php?title=Takuo_Aoyagi&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Takuo_Aoyagi&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Nihon_Kohden&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Nihon_Kohden&action=edit&redlink=1http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-2%23cite_note-2http://en.wikipedia.org/wiki/Bioxhttp://en.wikipedia.org/wiki/Pulse_oximetry#History%23Historyhttp://en.wikipedia.org/wiki/Pulse_oximetry#Limitations%23Limitationshttp://en.wikipedia.org/wiki/Pulse_oximetry#See_also%23See_alsohttp://en.wikipedia.org/wiki/Pulse_oximetry#References%23Referenceshttp://en.wikipedia.org/w/index.php?title=Pulse_oximetry&action=edit&section=1http://en.wikipedia.org/wiki/Oxygenationhttp://en.wikipedia.org/wiki/Intensive_carehttp://en.wikipedia.org/wiki/Critical_carehttp://en.wikipedia.org/wiki/Emergency_departmenthttp://en.wikipedia.org/wiki/Aircraft_pilothttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-1%23cite_note-1http://en.wikipedia.org/wiki/Primary_carehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Hypoventilationhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/w/index.php?title=Pulse_oximetry&action=edit&section=2http://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Photocellhttp://en.wikipedia.org/wiki/Sleep_laboratoryhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/w/index.php?title=Takuo_Aoyagi&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Nihon_Kohden&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Nihon_Kohden&action=edit&redlink=1http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-2%23cite_note-2http://en.wikipedia.org/wiki/Biox
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    1982. A competitor,Nellcor(now part ofCovidien, Ltd.), Incorporated in 1982, andbegan to compete with Biox for the US operating room market in 1983. Prior to itsintroduction, a patient's oxygenation could only be determined by a painfularterial bloodgas, a single point measure which takes a few minutes processing by a laboratory. (In theabsence of oxygenation, damage to the brainstarts in 5 minutes withbrain death in

    another 1015 minutes). In the US alone, approximately $2 billion was spent annually onthis measurement. With the introduction of pulse oximetry, a non-invasive, continuousmeasure of patient's oxygenation was possible, revolutionizing the practice of anesthesiaand greatly improving patient safety. Prior to its introduction, studies in anesthesiajournals estimated US patient mortality as a consequence of undetected hypoxemia at2,000 to 10,000 deaths per year, with no known estimate of patient morbidity.[citation needed]

    By 1987, the standard of care for the administration of a general anesthetic in the USincluded pulse oximetry. From the operating room, the use of pulse oximetry rapidlyspread throughout the hospital, first in the recovery room, and then into the variousintensive care units. Pulse oximetry was of particular value in the neonatal unit where the

    patients do not thrive with inadequate oxygenation, but also can be blinded with toomuch oxygen. Furthermore, obtaining an arterial blood gas from a neonatal patient isextremely difficult.[citation needed]

    In 1996, Masimo, a California-based company, introduced the first pulse oximeter able toprovide accurate measurements during periods of patient motion or low peripheralperfusion, long thought to be limitations of pulse oximetry technology that could not beovercome. [4] The ability to provide accurate measurements under these difficult clinicalconditions meant pulse oximetry could be used outside the operating room, wherepatients were generally well perfused and not moving, allowing for adoption in neonatalintensive care units, ambulances, and other challenging settings. [5]

    By 2008, the accuracy and capability of Pulse Oximetry had continued to increase, andhad allowed for the adoption of the term High Resolution Pulse Oximetry (HRPO).[6][7][8]

    One area of particular interest in the area of Pulse Oximetry, is the use of Pulse Oximetryin conducting portable and in-home sleep apnea screening and testing.[6][9]

    In 2009, the World's first Bluetooth-enabled fingertip pulse oximeter was introduced byNonin Medical, enabling clinicians to remotely monitor patients pulses and oxygensaturation levels. It also allows patients to monitor their own health through online patienthealth records and home telemedicine system.[10]

    [edit] LimitationsThis is a measure solely of oxygenation, not ofventilation, and is not a substitute forblood gaseschecked in a laboratory as it gives no indication of base deficit,carbondioxide levels, bloodpH, or bicarbonate HCO3-concentration. The metabolism ofoxygen can be readily measured by monitoring expired CO2. Saturation figures also giveno information about blood oxygen content. Most of the oxygen in the blood is carried by

    http://en.wikipedia.org/wiki/Nellcorhttp://en.wikipedia.org/wiki/Covidienhttp://en.wikipedia.org/wiki/Arterial_blood_gashttp://en.wikipedia.org/wiki/Arterial_blood_gashttp://en.wikipedia.org/wiki/Arterial_blood_gashttp://en.wikipedia.org/wiki/Brain_damagehttp://en.wikipedia.org/wiki/Brain_damagehttp://en.wikipedia.org/wiki/Brain_deathhttp://en.wikipedia.org/wiki/Anesthesiahttp://en.wikipedia.org/wiki/Hypoxemiahttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/w/index.php?title=Recovery_room&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Recovery_room&action=edit&redlink=1http://en.wikipedia.org/wiki/Intensive_care_unithttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Masimohttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-3%23cite_note-3http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-4%23cite_note-4http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-sleepreviewmag.com-5%23cite_note-sleepreviewmag.com-5http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-sleepreviewmag.com-5%23cite_note-sleepreviewmag.com-5http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-6%23cite_note-6http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-7%23cite_note-7http://en.wikipedia.org/wiki/Sleep_apneahttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-sleepreviewmag.com-5%23cite_note-sleepreviewmag.com-5http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-8%23cite_note-8http://en.wikipedia.org/wiki/Nonin_Medicalhttp://en.wikipedia.org/wiki/Nonin_Medicalhttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-9%23cite_note-9http://en.wikipedia.org/w/index.php?title=Pulse_oximetry&action=edit&section=3http://en.wikipedia.org/wiki/Ventilation_(physiology)http://en.wikipedia.org/wiki/Ventilation_(physiology)http://en.wikipedia.org/wiki/Blood_gaseshttp://en.wikipedia.org/wiki/Blood_gaseshttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/HCO3-http://en.wikipedia.org/wiki/HCO3-http://en.wikipedia.org/wiki/Nellcorhttp://en.wikipedia.org/wiki/Covidienhttp://en.wikipedia.org/wiki/Arterial_blood_gashttp://en.wikipedia.org/wiki/Arterial_blood_gashttp://en.wikipedia.org/wiki/Brain_damagehttp://en.wikipedia.org/wiki/Brain_deathhttp://en.wikipedia.org/wiki/Anesthesiahttp://en.wikipedia.org/wiki/Hypoxemiahttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/w/index.php?title=Recovery_room&action=edit&redlink=1http://en.wikipedia.org/wiki/Intensive_care_unithttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Masimohttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-3%23cite_note-3http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-4%23cite_note-4http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-sleepreviewmag.com-5%23cite_note-sleepreviewmag.com-5http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-6%23cite_note-6http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-7%23cite_note-7http://en.wikipedia.org/wiki/Sleep_apneahttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-sleepreviewmag.com-5%23cite_note-sleepreviewmag.com-5http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-8%23cite_note-8http://en.wikipedia.org/wiki/Nonin_Medicalhttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-9%23cite_note-9http://en.wikipedia.org/w/index.php?title=Pulse_oximetry&action=edit&section=3http://en.wikipedia.org/wiki/Ventilation_(physiology)http://en.wikipedia.org/wiki/Blood_gaseshttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/HCO3-
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    hemoglobin. In severe anemia, the blood will carry less total oxygen, despite thehemoglobin being 100% saturated.

    Falsely low readings may be caused by hypoperfusionof the extremity being used formonitoring (often due to the part being cold or fromvasoconstrictionsecondary to the use

    of vasopressor agents); incorrect sensor application; highly calloused skin; and movement(such as shivering), especially during hypoperfusion. To ensure accuracy, the sensorshould return a steady pulse and/or pulse waveform. Falsely high or falsely low readingswill occur when hemoglobin is bound to something other than oxygen. In cases ofcarbonmonoxide poisoning, the falsely high reading may delay the recognition ofhypoxemia(low blood oxygen level). Methemoglobinemia characteristically causes pulse oximetryreadings in the mid-80s. Cyanide poisoningcan also give a high reading because itreduces oxygen extraction from arterial blood (the reading is not false, as arterial bloodoxygen is indeed high in early cyanide poisoning).

    Pulse oximetry only reads the percentage of bound hemoglobin. It can be bound to other

    gasses such as carbon monoxide and still read high even though the patient is hypoxemic.The only noninvasive methodology that allows for the continuous and noninvasivemeasurement of the dyshemoglobins is a pulse co-oximeter. Pulse CO-Oximetry wasinvented in 2005 by Masimo and currently allows clinicians to measure totalhemoglobinlevels in addition to carboxyhemoglobin, methemoglobinand PVI, which initial clinicalstudies have shown may provide clinicians with a new method for noninvasive andautomatic assessment of patient fluid volume status.[11][12][13] Appropriate fluid levels arevital to reducing postoperative risks and improving patient outcomes as fluid volumesthat are too low (under hydration) or too high (over hydration) have been shown todecrease wound healing, increase risk of infection and cardiac complications.[14]

    http://en.wikipedia.org/wiki/Hypoperfusionhttp://en.wikipedia.org/wiki/Hypoperfusionhttp://en.wikipedia.org/wiki/Vasoconstrictionhttp://en.wikipedia.org/wiki/Vasoconstrictionhttp://en.wikipedia.org/wiki/Vasoconstrictionhttp://en.wikipedia.org/wiki/Hypoperfusionhttp://en.wikipedia.org/wiki/Hypoperfusionhttp://en.wikipedia.org/wiki/Carbon_monoxide_poisoninghttp://en.wikipedia.org/wiki/Carbon_monoxide_poisoninghttp://en.wikipedia.org/wiki/Hypoxia_(medical)http://en.wikipedia.org/wiki/Cyanide_poisoninghttp://en.wikipedia.org/wiki/Cyanide_poisoninghttp://en.wikipedia.org/wiki/Co-oximeterhttp://en.wikipedia.org/wiki/Masimohttp://en.wikipedia.org/wiki/Hemoglobinhttp://en.wikipedia.org/wiki/Hemoglobinhttp://en.wikipedia.org/wiki/Carboxyhemoglobinhttp://en.wikipedia.org/wiki/Methemoglobinhttp://en.wikipedia.org/wiki/Methemoglobinhttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-10%23cite_note-10http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-11%23cite_note-11http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-12%23cite_note-12http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-13%23cite_note-13http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-13%23cite_note-13http://en.wikipedia.org/wiki/Hypoperfusionhttp://en.wikipedia.org/wiki/Vasoconstrictionhttp://en.wikipedia.org/wiki/Hypoperfusionhttp://en.wikipedia.org/wiki/Carbon_monoxide_poisoninghttp://en.wikipedia.org/wiki/Carbon_monoxide_poisoninghttp://en.wikipedia.org/wiki/Hypoxia_(medical)http://en.wikipedia.org/wiki/Cyanide_poisoninghttp://en.wikipedia.org/wiki/Co-oximeterhttp://en.wikipedia.org/wiki/Masimohttp://en.wikipedia.org/wiki/Hemoglobinhttp://en.wikipedia.org/wiki/Carboxyhemoglobinhttp://en.wikipedia.org/wiki/Methemoglobinhttp://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-10%23cite_note-10http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-11%23cite_note-11http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-12%23cite_note-12http://en.wikipedia.org/wiki/Pulse_oximetry#cite_note-13%23cite_note-13