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By: leslielove (98 month(s) ago)

I remember when I had a surgery when I was about 12 years old. I was hooked up to an oximetry test and it measured the oxygen in my lungs. I had to breath deeply the whole time I used that thing or it would beep like the dickens! They're very useful in the medical field, but they kept me up that whole night because I would try and fall asleep and it would start beeping because I would forget to breath deeply. http://www.cardiocorps.com

By: swatiapu (101 month(s) ago)

can you please give me permission to download your presentation ?

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History : 

History 1935 Carl Matthes – 1st to build the device Development of LED’s, photodetectors and microprocessors refined the technique of pulse oximetry. 1980 William New – Modern pulse oximeter. 1987- standard care for GA included pulse oximeter. 2008- HRPO is used for screening and testing for sleep apnea at home.


INTRODUCTION Pulse oximetry is an optical measurement of oxygen saturation in tissues Non invasive Continuos monitoring of O2 saturation Measures cardiorespiratory function Quickly detects hypoxaemia

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Modern Pulse oximetry was born with realization that pulsatile changes in light transmission through living tissue are due to alteration of the arterial blood volume in the tissue. Measurement of the pulsatile component would eliminate the variable absorption of light by bone, tissue,skin, pigment,etc from analysis.


PULSE OXIMETRY Uses spectrophotometry based on the Beer-Lambert law Differentiates oxy from deoxy Hb by the differences in absorption of light at 660 nm and 940 nm. At 660nm deoxyhb absorbs 10times the light compared to oxyhb. At 940nm oxyhb absorbs more light than deoxyhb. Minimizes tissue interference by separating out the pulsatile signal Estimates HR by measuring cyclic changes in light transmission Estimates functional Hb by comparing amounts of oxy and deoxy Hb


PRINCIPLES Spectrophotometry [light absorbance of oxyhb is different from deoxyhb] Plethysmography [measurement of the fluctuations in the volume of arterial blood between source and the detector] Beer’s law: states that intensity of transmitted light decreases exponentially as the concentration of the substance increases. Lambert’s law: states that intensity of transmitted light decreases exponentially as the distance travelled through the substance increases.


USES OF PULSE OXIMETRY Monitoring oxygenation: O.T,ICU, PACU,Pre hospital rapid sequence intubation,during transport and to diagnose obstructive sleep apnoea. Monitoring circulation Avoidance of hyperoxaemia:retrolental fibroplasia Accurate usage of O2 and avoid wastage: maintaining hypoxic ventilatory drive in resp failure Can replace ABG analysis Monitoring vascular volume


SOURCES OF ERROR Sensitive to motion Sats below 85% have increased error Calibration is performed by company on normal patients breathing various gas mixtures, so cal is accurate only down to 80% Low perfusion state increases error Ambient light interferes with reading Delay in reading of about 12 seconds


SOURCES OF ERROR Skin pigmentation Darker color may make the reading more variable due to optical shunting Dark nail polish has the same effect, especially black, blue, and green…red is OK Hyperbilirubinemia has no effect Methylene blue and indigo carmine (dyes) cause underestimation of the saturation


SOURCES OF ERROR Dysfunctional hemoglobin Carboxyhemoglobin leads to overestimation of sats because it absorbs at 660 nm like oxyHb does MetHb can mask the true saturation because it absorbs at both wavelengths used…sats are overestimated Anaemichypoxia is not detected Pulsatile veins

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Fails to detect hypoventilation, hypercarbia and hyperventilation. Fails to detect disconections or oesophageal intubation or assess the adequacy of ventilation. A capnograph is necessary to detect these complication


NORMAL CAPNOGRAM Phase I: the beginning of exhalation…CO2 level is zero Phase II: alveolar gas begins to mix with the deadspace gas and the CO2 rises rapidly Phase III: elimination of CO2 from the alveoli…usually has a slight upward slope Phase IV: end exhalation Phase 0: inspiration




ABNORMALITIES Increased Phase 3 slope: Obstructive lung dx Phase 3 dip: Spont resp Curare cleft Horizontal Phase 3 with large ET-art gradient: Pulm. Embolism Decreased CO hypovolemia Sudden decrease to 0 Ventilator malfunction ETT disconnect ET obstruction Extubation Sudden decrease Partial obstruction Air leak Exponential decrease Severe hyperventilation CP event


ABNORMALITIES Gradual decrease Hyperventilation Decreased T Gradual decrease in volume Sudden increase Bicarb administration Release of limb tourniquet Gradual increase Fever Hypoventilation Increased baseline Rebreathing CO2 Exhaused CO2 absorber

The Arterial Blood Gas analysis : 

The Arterial Blood Gas analysis

Information Obtained from an ABG: : 

Information Obtained from an ABG: Acid base status Oxygenation Dissolved O2 (pO2) Saturation of hemoglobin CO2 elimination Levels of carboxyhemoglobin and methemoglobin

Indications: : 

Indications: Assess the ventilatory status, oxygenation and acid base status Assess the response to an intervention

Contraindications: : 

Contraindications: Bleeding diathesis AV fistula Severe peripheral vascular disease, absence of an arterial pulse Infection over site

Why an ABG instead of Pulse oximetry? : 

Why an ABG instead of Pulse oximetry? Pulse oximetry does not assess ventilation (pCO2) or acid base status. Pulse oximetry becomes unreliable when saturations fall below 70-80%. Technical sources of error (ambient or fluorescent light, hypoperfusion, nail polish, skin pigmentation) Pulse oximetry cannot interpret methemoglobin or carboxyhemoglobin.

Which Artery to Choose? : 

Which Artery to Choose? The radial artery is superficial, has collaterals and is easily compressed. It should almost always be the first choice. Other arteries (femoral, dorsalis pedis, brachial) can be used in emergencies.

Preparing to perform the Procedure: : 

Preparing to perform the Procedure: Make sure you and the patient are comfortable. Assess the patency of the radial and ulnar arteries.

Collection Problems: : 

Collection Problems: Type of syringe Plastic vs. glass Use of heparin Air bubbles Specimen handling and transport

Type of Syringe : 

Type of Syringe Glass- Impermeable to gases Expensive and impractical Plastic- Somewhat permeable to gases Disposable and inexpensive

Heparin : 

Heparin Liquid Dilutional effect if <2-3 ml of blood collected Preloaded dry heparin powder Eliminates dilution problem Mixing becomes more important May alter sodium or potassium levels

The Kit : 

The Kit

Air bubbles : 

Air bubbles Gas equilibration between ambient air (pO2 ~ 150, pCO2~0) and arterial blood. pO2 will begin to rise, pCO2 will fall Effect is a function of duration of exposure and surface area of air bubble. Effect is amplified by pneumatic tube transport.

Transport : 

Transport After specimen collected and air bubble removed, gently mix and invert syringe. Because the wbcs are metabolically active, they will consume oxygen. Plastic syringes are gas permeable. Key: Minimize time from sample acquisition to analysis.

Transport : 

Transport Placing the AGB on ice may help minimize changes, depending on the type of syringe, pO2 and white blood cell count. Its probably not as important if the specimen is delivered immediately.

Performing the Procedure: : 

Performing the Procedure: Follow asepsis Prepare the site Drape the bed Cleanse the radial area with a alcohol Position the wrist (hyper-extended, using a rolled up towel if necessary) Palpate the arterial pulse and visualize the course of the artery.

Performing the Procedure: : 

Performing the Procedure: If you are going to use local anesthetic, infiltrate the skin with 2% xylocaine. Open the ABG kit Line the needle up with the artery, bevel side up. Enter the artery and allow the syringe to fill spontaneously.

Performing the Procedure: : 

Performing the Procedure: Withdraw the needle and hold pressure on the site. Protect needle Remove any air bubbles Gently mix the specimen by rolling it between your palms Place the specimen on ice and transport to lab immediately.

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