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Pulse Oximetry

Pulse Oximetry

by lauraleighsmith989, May 2011

Subjects: firstsemester physical-chemical

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156 Cards in this Set

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	AANA Standard II During all anesthetics, the patient's ________, ________, ___________, and ________ shall be continuously evaluted.	During all anesthetics, the patient's oxygenation, ventilation, circulation, and temperature shall be continually evaluated.
	How do you monitor ventilation?	Lungs Sounds Bilateral Chest Rise ETCO2 Spirometry and ventilatory pressure monitors.
	How do you monitor oxygenation?	Clinical Observation: Skin color. Pulse Oximetry Arterial Blood Gas Analysis Oxygen Analyzer Alarm tells you if the inspired gas conc is too low. Oxygen supply failure alarm tells you if your O2 pipeline pressure falls below 45 psi.
	What do you do if you omit a monitoring standard? ex: etco2 or something.	You DOCUMENT why and state why you omitted it on the anesthesia record.
	Patient Monitoring Standards	Direct observation by anesthesia provider Ventilation Oxygenation Circulation Body Temperature Neuromuscular Function Body Positioning Anesthesia Equipment
	Causes of Hypoxemia	Low delivered concentration of oxygen. Hypoventilation Impaired alveolar-capillary diffusion Ventilation-perfusion mismatches Increased intrapulmonary shunting. Atelectasis Pulmonary Edema Pulmonary Embolism Aspiration Bronchospasm Hypoventilation
	The minimum required arterial oxygen monitoring is...	Pulse Oximeter
	20-30% of mishaps related to human error in anesthesia occur because of lack of __________.	20-30 of mishaps related to human error in anesthesia occur because of lack of vigilance.
	Two most common monitoring standards:	1) The Harvard Standards of Monitoring. 2) AANA Standards for Monitoring. * these set the minimum amt of monitoring standards required.
	Ventilation is monitored with...	ETCO2 monitor- capnography Chest Rise Bilateral Breath Sounds (use precordial stethescope) Spirometry on ventilators. Airway pressure monitoring devices (tells you airway compliance and resistance).
	During ALL anesthetics you must continously monitor. ....	Oxygenation Ventilation Circulation and Temperature
	Loss of conciousness for how long is considered general anesthesia?	1 sec Therefore must monitor all forms as if general anesthesia.
	How do you monitor inspired gas O2 concentration?	Oxygen analyzer on the inspiratory limb of the breathing circuit.
	How do you monitor arterial oxygen saturation?	Pulse Oximeter ABG if no perfusion or no pulse ox reading.
	Standards for Nurse Anesthesia Practice apply when?	Anytime/ anywhere you are providing an anesthetic.
	What is the only thing that prevents a hypoxic gas mixture?	the oxygen analyzer on the inspiratory limb of the breathing circuit.
	How do you monitor anesthesia equipment	Machine checkout Fill vaporizers, assure adequate gas concentrations. Change absorbers, etc.
	What are the "Six Senses" of a CRNA? (there's really only 5).	INSPECTION ----> Skin: color, cap refill, rash?, edema? ----> Nail Beds: color, cap refill ----> Mucous Membranes: color, moist?, edema? ----> Surgical Field: Blood color, tissue color, rate of blood loss, skeletal muscle relaxation? -----> Movement: purposeful or reflex? -----> Eyes - conjunctiva: color, edema? pupil size and reactivity PALPATION ---> Skin: Temperature and texture ---> Pulses: fullness, rate, and regularity ---> Skeletal Muscle - tone? PERCUSSION ---> Gastric - to check for distention ---> Chest - To check for pneumothorax (hyperresonance = pneumothorax). AUSCULTATION ---> Chest: ventilation and heart sounds ---> Systemic Blood Pressure EXPERIENCE ---> this is the sixth sense.
	Hyperresonance of lung sounds on one side of chest=	Possible pneumothorax.
	Pulse oximetry can tell you...	Arterial hemoglobin saturation. Heart Rate Perfusion
	Causes of Hypoxemia	* Low delivered concentration of Oxygen (Inadequate preoxygenation) * Hypoventilation (decreased Vt (atelectasis) and/or RR) * Impaired alveolar-capillary diffusion (ARDS-decreased capillary permeability, edematous lungs, thickened membranes) * Ventilation-perfusion mismatches (either lack of ventilation or a pulmonary embolus). * Increased intrapulmonary shunting *
	What should be the first monitoring device connected to the pt?	Pulse Oximeter
	Minute ventilation is determined by two factors...	Tidal Volume Respiratory Rate
	What can cause atelectasis?	Long surgeries with inadequate tidal volumes. Thoracotomy - breathing with one lung during sx. Somnulent patients post op.
	Pulmonary Embolism causes hypoxia because...	lack of perfusion past the emboli.
	Is pulmonary edema a ventilation or perfusion problem? Explain pulmonary edema	Perfusion A form of ARDS in which fluid leaks into the alveoli from the capillaries , causing lowered perfusion as well as an interruption of gas diffusion. Caused by: INCREASED HYDROSTATIC PRESSURE ---> Ischemic Heart Disease ---> Left Heart Failure ---> CHF DECREASED INTERSTITIAL PRESSURE ---> Negative Pressure Pulmonary Edema (inspiration with laryngospasm or biting on the tube) *INCREASED CAPILLARY PERMEABILITY ---> Sepsis ---> Aspiration ---> Transfusion Reactions ---> Histamine Release
	Bronchospasm causes hypoxemia because...	Airways contract/ clamp down. Unable to move air through airways.
	How do you treat atelectasis?	Humidified O2 - (may go up to 100% on the O2) Coughing and Deep Breathing, Incentive Spirometry. Postural Drainage - (percussion on the beds to break up secretions) Intermittent positive pressure ventilation.
	What happens with Bronchospasm?	Increase in bronchial smooth muscle tone with resultant closure of small airways - VERY hard to ventilate a pt. (Ex: asthma attacks) Airway edema develops Increased secretions Hypoxemia occurs CLINICAL PRESENTATION: Wheezing Dypsnea Use of Accessory Muscles Tachypnia Increased PIP if intubated CAUSES Aspiration ETT intubation Histamine release due to allergic rxn TREATMENT Beta 2 Agonists - Albuterol, Epinephrine
	Clinical presentations of Bronchospasm	CLINICAL PRESENTATION: Wheezing Dypsnea Use of Accessory Muscles Tachypnia Increased PIP if intubated
	Treatment of Bronchospasm	Beta 2 Agonist * Albuterol * Epinephrine
	Chemical Pneumonitis is defined as ON TEST!!!!!!!!!!!!!!!	Aspiration of gastric contents with a gastric pH of < 2.5 and an aspirated volume of greater than 0.4-1.0 ml/kg ON TEST!!!!!!
	Bronchospasms can cause	Bronchospasm/ Laryngospasm Hypoxemia Atelectasis Interstitial Edema Hemorrhage ARDS Infection Pulmonary Edema
	Causes of Bronchospasm	ETT intubation Aspiration Histamine release from allergic reaction
	ASA closed claims study said that respiratory system events made up ___% of all damaging events.	27%
	ASA closed claims study found that Adverse Respiratory Events can be divided up by the following percentages	38% - Inadequate Hypoventilation 18% - Esophageal Intubation 17% - Difficult intubation
	Why are esophageal intubations often unrecognized at first?	You may get some ETCO2 initially. Therefore, you need a SUSTAINED CO2 level to verify that you have intubated the trachea.
	72% of Adverse Respiratory Events are preventable with __________________.	72% of Adverse Respiratory Events are preventable with pulse oximetry, capnometry, or a combination of the two.
	Non invasive value for hemoglobin O2 saturation:	SpO2
	The pulse Ox signal varies in pitch depending on	The pulse ox signal varies in pitch depending on the SpO2 value. HIgh pitch - good Low pitch - desaturating
	How can you monitor volume status with O2 sat monitors?	Waveform amplitude
	What is the wavelength of red light? In pulse oximetry, what absorbs red light?	660 nm In pulse oximetry red light is absorbed by deoxygenated hemoglobin.
	What is the wavelength of infrared light? In pulse oximetry, what absorbs infrared light?	940 nm In pulse oximetry, infrared light is absorbed by oxygenated hemoglobin.
	The pulse waveform on a pulse oximeter waveform correlates with...	patient's heart rate.
	Why is pulse oximetry especially important when using an electrocaudery unit?	Electrocaudering units can interfere with EKG readings and cause them to be inaccurate. Look at the pulse oximeter heart rate during these times to get an accurate heart rate.
	Tissue oxygenation depends on	Hgb concentration SaO2 Cardiac Output O2 Consumption
	Lambert-Beer Law ON TEST!!!!	Concentration of a liquid is related to the amount of light that will pass through it. Oxy and deoxy Hgb both absorb diff wavelengths of light. Oxyhemoglobin absorbs more infrared light. Therefore, the concentration of oxyhemoglobin depends on the amount of infrared light that is absorbed. Beer-Lambert law: concentration of an unknown solute in a solvent can be determined by light absorption Wavelengths of 660nm (red) and 940nm (infrared) Absorption characteristics of the 2 hemoglobins are different at these 2 wavelengths
	For a normal patient sating 100% on room air paO2 -	90 mmHg Measures parital pressure of O2 in blood plasma.
	Oxyhemoglobin Dissociation Curve assumes that pt has normal values of...	pH= 7.4 PaCO2 = 40 mmHg Temp = 37 deg Celcius Normal 2,3 DPG
	Upper portion of the oxyhemoglobin dissociation curve represents...	O2 loading in the lungs.
	Lower portion of oxyhemoglobin dissociation curve represents...	O2 unloading at the tissue level.
	ON TEST!!!! Tell me what paO2 values correllate with SaO2 values of: SaO2 50% SaO2 75% SaO2 90% SaO2 100%??	SaO2 50% = PaO2 27 mmHg SaO2 75% = PaO2 40 mmHg SaO2 90% = PaO2 60 mmHg SaO2 100%= PaO2 90 mmHg
	Left Shift of the Oxyhemoglobin Dissociation Curve occurs with	Alkalosis Hypothermia Decreased 2,3 DPG levels Decreased PaCO2 Fetal Hgb (Hgb F) Carboxyhemoglobin Methemaglobin Causes decreased O2 extraction at the tissue level.
	Pulse oximeter readings are only accurate for Hgb saturations greater than ___ %.	Pulse oximeter readings are only accurate for Hgb saturations greater than 80 %.
	p50 =	p50 = partial pressure of O2 on oxyhemoglobin dissociation curve at which the Hgb is 50% loaded with O2.
	Right Shifts of the Oxyhemoglobin dissociation curve occur with	Acidosis Hyperthermia Increased 2,3 DPG levels Anemia (causes increased 2,3 DPG levels). Increased PaCO2 Volatile anesthetic Agents Pregnancy This causes increased O2 extraction at the tissue level.
	What can cause false SpO2 readings?	Saturations less than 80% High Intensity Light Patient Movement Electrocautery Peripheral Vasoconstriction IV Dyes Shivering Dark Pigmentation Finger Nail Polish/ Synthetic Nails Cardiopulmonary Bypass Methemoglobinemia Carboxyhemoglobin
	What happens in cardiopulmonary bypass to affect the pulse Ox accuracy?	No pulsatile blood flow. Therefore, you have to get ABG's to determine the O2 value or get a SaO2 value instead of SpO2.
	Carboxyhemoglobin - how does this affect the pule ox accuracy?	The Pulse Ox will read Hgb saturation. CO binds to O2 binding sites on Hgb. the Hgb remains saturated. It absorbs the same infrared wavelengths of light. Sat probe will read false high readings for O2 saturation due to reading CO instead of O2.
	Carbon monoxide has __ times the affinity for Hgb as O2.	Carbon monoxide has 240 times the affinity for Hgb as O2.
	Causes and Treatment of Methemoglobinemia	CAUSES: Nitrate poisoning, Prilocaine given as an LA TREATMENT: Oxygen!! and Methylene Blue 1-2 mL per kg.
	What local anesthetic can cause methemoglobinemia?	Prilocaine
	Methemoglobinemia - how does this affect the pulse ox accuracy?	Methemoglobinemia = Hgb iron is in ferric (Fe3+) form instead of Fe2+. These forms DO NOT combine with O2 because they are oxidized. Methemoglobin refects both red and infrared light equally. This will cause the pulse oximeter to read an SpO2 level of 85%. So if you are actually 90%, it will cause a false low reading. If you are actually 70%, it will be a false high reading. CAUSES: Nitrate poisoning, Prilocaine given as an LA TREATMENT: Oxygen!! and Methylene Blue 1-2 mL per kg.
	What is atelectasis and what can cause atelectasis?	Atelectasis = alveolar collapse. Caused by --> Bronchial Obstructions --> Decreased lung volumes ---> Long sx's with inadequate tidal volumes ---> Somnulence Post Op.
	Pts at highest risk for aspiraton	Obese Truama Diabetics (slow gastric emptying) Reflux Hiatal Hernia Decreased Level of Conciousness (cannot control upper esophageal sphincter).
	Define Hypoventilation	Decrease in respiratory rate or tidal volumes with increase in PaCO2 CAUSE ---> Decrease in central respiratory drive ---> Poor respiratory muscle function ---> Combination of the two.
	Causes of Hypoventilation	CAUSE ---> Decrease in central respiratory drive ---> Poor respiratory muscle function ---> Combination of the two. RESPIRATORY MUSCLE DYSFUNCTION ---> Inadequately reversed NMB pts ---> Surgery of upper abdomen (pain keeps them from breathing) ---> Inadequately positioned pts (slouched and not sitting up) ---> Obesity/ pregnancy ---> Neuromuscular diseases
	What four factors must occur for adequate oxygenation to take place?	1) The blood must have enough O2 dissolved in it (paO2) 2) Hemoglobin levels must be normal (Adequate O2 carrying capacity). 3) There must be adequate cardiac output to carry the O2 to the tissues. 4) The cells must be able to adequately use the O2 that is delivered.
	What percentage of O2 is carried by the blood plasma instead of Hgb?	1-2% The reason this value is so low even though paO2 is so high is because most of the O2 (98-99%) gets grabbed up by Hgb in RBC's.
	PaO2 =	Concentration of O2 in the blood plasma (arteries). this value is obtained with an ABG. Represents 1-2% of the O2 in blood.
	Why is PaO2 so important if it doesn't represent most of the O2 in the blood?	Hgb gets it's O2 from PaO2. If PaO2 is low, then SaO2 could get low.
	Normal SaO2 and SpO2 values...	95-99%
	SpO2 =	Measured with a pulse oximeter Arterial Hemoglobin Oxygen Saturation Similiar to SaO2.
	True or false, a pt with an SpO2 of 97 has adequate arterial oxygen content.	FALSE Unless you know their Hgb value is normal you cannot make this assumption. They are perfusing well, but may not have enough Hgb OR you might have dysfunctional Hgb. Need to get an H and H.
	SaO2 =	Saturation of Hgb with O2. When taken as a standard of comparison for oximeter calibration, this is measured with a direct co-oximeter measurement of an arterial blood sample. (NOT with an ABG analyzer!!!) Represents 98-99% of the O2 in the blood. SaO2 = (Site filled)/ (Tot. site aval.) x 100%
	What is 2-3 DPG?	2,3-diphosphoglycerate (2,3-DPG) is a substance made in the red blood cells. It controls the movement of oxygen from red blood cells to body tissues. Therefore, with increased DPG, the oxyhemoglobin dissociation curve shifts to the right. Hgb loses it's affinity for oxygen. A decrease in 2-3 DPG causes the deoxyhemoglobin dissociation curve to shift to the left. Hgb has an increased affinity for O2. (happens with fetal hemoglobin).
	Decreased 2,3 DPG occurs with what conditons?	Septic Shock Hypophosphatemia Hypothyroidism Stored Blood Bank Carboxyhemoglobin Causes and increased affinity of Hgb and O2 (curve shifts to the left). Less O2 delivery at tissue level.
	Increased 2,3 DPG occurs with what conditions?	In the presence of diminished peripheral tissue O2 avaliability. Chronic Hypoxemia Chronic Lung Disease Anemia Congestive Heart Failure Hyperthyroidism Causes oxyhemoglobin dissociation curve to shift to the right. Hgb has a DECREASED affinity for O2. Allows more O2 delivery to tissues (but makes it harder to pick up O2 in lungs).
	Right Shifts of the Oxyhemoglobin Dissociation Curve occur with	Right shifts - Hgb has a decreased affinity for O2. More O2 extraction at the tissue level. (P-50 higher than 26 mmHg) Decreases in pH (Acidosis). Increases in temp (Hyperthermia) Increases in 2,3 DPG (Anemia) Increased PaCO2 (Alveolar hypoventilation)
	Insufficient oxygenation of arterial blood	Hypoxemia Can be chronic or episodic.
	Insufficient oxygenation of the tissues	Hypoxia
	Pt's at risk for Hypoxemia	Pts in Noncritical Care Setting Postoperative Patients (First few hours after surgery and 5 nights postop due to anesthesia and pain meds) Patients in Pain/ Receiving Pain Management Confirmed Obstructive Sleep Apnea or Morbidly Obese Patients Pts with Pre-existing Cardiopulmonary Disorders Pts Receiving Conscious Sedation Neonatal, Pediatric and Elderly Patients Obstetric Patients The technology-dependent patient
	How can hypoxemia impair cerebral function?	ST memory loss Confusion Cognitive Dysfunction or permanent impairment Cerebral ischemia or stroke
	True or False, as long as the pt's skin is pink, they are not hypoxemic.	False Cyanosis is a LATE sign of hypoxemia and is related to the amt of Hgb in the blood. DeoxyHgb makes the blood turn blue. If the pt is anemic, this color change will not occur. So pink skin can still be present with hypoxemia, especially in anemic patients. Also, dark skin colors will not show cyanosis well and you may miss it.
	True or false, RR changes can accurately detect hypoxemia	FALSE
	How does a pulse oximeter work?	Works by applying a sensor to a pulsating arteriolar vascular bed. The sensor contains a dual light source and photodetector, which are used to measure the amount of O2 that is combined with hemoglobin. The dual light source has a red and infrared light. These light sources are used because each is absorbed differently by oxyhemoglobin and deoxyhemoglobin. Bone, tissue, pigmentation and venous vessels normally absorb a constant amount of light over time. The arteriolar bed, however, pulsates and absorbs variable amts of light during systole and diastole, as blood volume increases and decreases. The ratio of the amt of each light source absorbed at systole and diastole is translated into an O2 saturation measurement. (SpO2)
	Why does a pulse ox have two diff types of light sources?	The red and infrared light sources are absorbed differently by oxyhemoglobin and deoxyhemoglobin.
	Left Shifts of the Oxyhemoglobin Dissociation Curve occur with	Left Shifts - Hemoglobin has a increased affinity for Oxygen. Less O2 extraction at the tissue level. Increased pH (Alkalosis) Decreased temperature (Hypothermia) Decreased PaCO2 (Hyperventilation) Decreased 2,3 DPG (Sepsis, Carbooxyhemoglobinemia, hypophosphatemia, fetal hemoglobin)
	Why does the arterial vascular bed absorb varying amounts of light?	The volume of blood increases and decreases with systole/ diastole.
	How is an SaO2 obtained?	An arterial blood sample is measured directly by a laboratory co-oximeter . NOT by a blood gas analyzer.
	Explain some causes of large variations b/n SaO2 and SpO2.	Blood gas is drawn at a diff time than the SpO2 measurement is taken. (They should be done at the same time). Inaccurate blood gas sampling technique (Follow proper ABG technique). Blood Gas machine is not calibrated accurately. SaO2 is calculated from PaO2 using arterial blood gas analyzer, and not DIRECTLY measured with laboratory co-oximeter. (ABG analyzer values are calculated and not direct measurements). Dysfunctional Hemoglobin in pt: High level of carboxyhemoglobin or methemoglobin will cause SaO2 to differ from SpO2. (Assess Oxygenation using a measured SaO2 whenever dysfunctional hemoglobins are suspected.). Intra-Cardiac Shunting: Causes diff O2 sats in diff parts of the body. (You should be aware of this and choose the right spot for a sample and measurement.) Intravascular Dyes: results in temporary aberration of the SpO2 reading. (Don't take measurements immediately after injection of a dye.)
	Oxismart Technology, what does it do? How does it work?	Provides a way to bypass the artifact alarms and false readings of pulse oximeters from pt movement or poor perfusion. Identifies and rejects artifacts that could otherwise be be mistaken for a pulse. Can also distinguish between actual and loss of pulse and a pulse that is obscurred by low perfusion, motion artifact, and electronic or optical noise. How? It tests the pulse waveform shape and kicks out ones that are not possible. If a pt is moving, it waits until it can get a pulse. If the pt is not moving and it can get no pulse for 6 seconds, then it alarms. As long as the pt is moving, it will continue to look for a pulse for up to 50 seconds, then it will alarm. If it then gets a pulse, it will stop alarming.
	Oxismart XL Technology, what does it do? How does it work?	Employs parallel engines that run simultaneously to qualify pulses, calculate saturation and pulse rate values, and sound a beep tone. Evaluates waveforms like oxismart to verify a pulse but also tracks teh pulse using ADAPTIVE COMB FILTERING. ACF enables the oximeter to read through challenging motion. Also uses additional method for calc. SpO2 adn pulse rate as an adjunct to that of Oxismart.
	What is SatSeconds Alarm Management?	Alarm management system in monitors of oxismart XL engines. Tracks desaturations more accurately and quickly then was previously possible. Allows you to set a threshold of 10, 25, 50, or 100 SatSeconds. Only if the fall in % points of saturation multipled by the duration in seconds exceeds this threshold would the alarm sound. As a safety net, an alarm will sound whenever three alarm limit violations occur in a 60 sec. period, even if a satseconds violation did not occur.
	Transmittance Sensors: how are they applied?	The finger must be in b/n the light source and the photodetector.
	Reflectance sensors: How are they applied?	require proper alignment of the sensor against the surface of the skin. DO NOT APPLY ADDITIONAL TAPE TO THE SENSOR.
	Nelcor re-usable sensors should be moved to another site how often? Why?	Every 4 hours. Must be rotated to preserve skin integrity.
	Nelcor adhesive sensor sites should be checked how often?	Every 8 hours.
	Why don't you add tape to adhesive Pulse oximeters (um it did this all the time...oops. )	To protect circulation.
	How do you clean reusable pulse ox sensors?	With 70% alcohol.
	What is ideal extremity for a pulse ox?	No edema. No BP Cuff Not alot of movement. No art line. No IV.
	Why spot check SpO2 on the floor?	To verify adequate oxygenation and no need for continuous pulse ox monitoring.
	Remote oximetry monitoring.	Measures SpO2 and sends value to a monitor at the nurses station. Can also page the nurse with an alarm. Also can show trends. Cost effective way to assure pt safety when nurse cannot be in the room.
	T/F - pulse oximeters are mandatory monitors for any anesthetic case inc. moderate sedation?	TRUE
	What are the contraindications of pulse oximetry?	None
	How do pulse oximeters work?	a sensor containing light sources and a light detector (photodiode) is placed across a finger, toe earlobe or other perfused tissue that can be transilluminated.
	What is the principle of pulse oximetry?	oxyhb and deoxyhb differ in their absorption of red and infrared light. The change in light absorption during arterial pulsatons is the basis of oximetric determinations.
	What part of pulse oximetry is indicative of tissue perfusion?	Pulse amplitude.
	What can one discern from an SpO2 waveform?	hemoglobin saturation, tissue perfusion and heart rate.
	Roughly, a SpO2 of 90% indicates what in an anesthetized patient?	A PaO2 of < 65 mmHg This compares with clinically detectable cyanosis and usually corresponds to an SpO2 of 80% or so in an unanesthetized patient.
	Can pulso oximetry detect a bronchial intubation?	No...bronchial intubation will usually go undetected in the absence of lung disease or low FiO2%.
	T/F: Methemoglobinemia has no impact on SpO2 readings?	False - b/c methemoglobin has same absortion coeff at both red and infrared wavelengths. This 1:1 absorption ration corresponds to a saturation reading of 85%. So? Methehemoglobinemia causes a false low sat reading when SaO2 is > 85% and a false high sat reading when SaO2 is actually < 85%.
	Causes of pulse-ox artifact?	Excessive ambient light, motion, meth-blue dye, motion, venous pulsatoins in dependent limb, low perfusion states (low CO, hypothermia, increased SVR, profoiund anemia), malpositioned sensor, aptical shunting.
	What are some ways in which pulse oximetry is diagnostic?	Recognition of hypoxia (as occurs in esophageal intubations Furthers goal of monitioring delivery of O2 to vital organs. In RR helps ID postop pulm problems (hypotvent, bronchospasm, atelectasis)
	What is an invasive form of oximetry?	mixed venouis blood oxygen saturation (Svo2) - PAC containing fiberoptics continuously determine SvO2 similar to pulse oximetry.
	What is nonivasive brain oximetry?	A method of monitoring regional oxygen saturation (rSO2) of hb in the brain. Sensor is placed on forehead and emits specific wavelength light & measures light reflected to sensor (near infrared optical spectroscopy). Measure arterial oxygen saturation as well as venous & capillary blood oxyg sats. - gives a represtative reading of avg oxygen satuatio of all regionsl microvascular heomglobin.
	What can cause a dramatic increase in rSO2?	Cardiac arrest ,cerebral emobolus, deep hypothermia, severe hypoxia.
	What is a major complication of sitting craniotomies and how is it detectable?	Air embolism. A rapid fall of EtCo2 is a sensitive indicator of air embolism.
	What are contraindiations to capnography?	None
	What are the two main types of capnographs?	Flowthrough and Sidestream
	What is a problem with flowthrough capnometry?	The sensor, which is placed inline between the patient Y and ett, places traction on the ett. Its radiant heat (older models) can cause burns.
	How do sidestream capnometers work?	They continuously aspirate gas frmo breathing circuit into sample cell where CO2 concentration is determined.
	What makes sidestream capnometry more accurate?	High aspiration rates (250 ML/MIN) and low dead space sampling tubing. (high rates of asp can mix in fresh gas in patients with low Ve and lower detected CO2)
	What can cause underestimation of CO2 in sidestream capnometry?	Low flow rates (<50 ML/MIN) Accumulation of water in the sampling tubing and sampling cell.
	How can EtCO2 detect faulty inspiratory valve?	CO2 will rise b/c this allows rebreathing of CO2...though the FGF will cause monitor to read 0 during inspiratory phase.
	Do capnographs detect bronchial intubation?	No - they DO detect esophageal intubations reliaby, though.
	What is the normal gradient between PaCO2 and EtCO2?	2-5 mmHg (alveolar dead space).
	Is EtCO2 increased or decreased when lung perfusion is reduced? Why or Why not?	EtCO2 is decreased. Anything that decreases lung perfusion (embolism, lowered CO, decreaed BP) increases alveolar deadspace...this air that has no CO2 dilutes the expired CO2 and lessens EtCO2
	What the phases of a capnograph?	I - alveolar deadspace II - upslope; mixture of alveolar dead space and alveolar gas (including CO2) III - alveolar gas plateau Inspiration phase (sharp downslope and return to phase I)
	What does a capnograph with a sloping phase II that never reaches plateau indicate?	COPD - due to the obstructiveness of the disease, slow alveoli constantly empty their contents causing the constant upslope and lack of plateau.
	What is a curare notch?	A depression during phase III that indicates spontaneous respiratory effort.
	What does a prolonged phase III extending into the inspiratory phase indicate?	This is persistence of exhaled gas during the inspiratory cycle. It indicates an incompetent inspiratory valve.
	How can you tell if you have a bad expiratory valve or exhausted CO2 absorber?	Failure of inspired CO2 to return to baseline during phase I.
	How are most anesthetic gases analyzed now?	infrared absorption analysis.
	Do oxygen and nitrogen absorb infrard light? Why or why not?	No - b/c they are nonpolar.
	What is a benefit of dual-beam infrred optical analyzers?	They detect gases seperately and allow detection of an improperly filled vaporizer.
	What does low PIP indicate?	Circuit or ventilator disconnection
	What does high PIP indicate?	An airway obstruction.
	T/F - PETCO2 is a good measure of PaCO2. Why or why not?	Yes - PETCO2 (and PACO2) - PaCO2 gradient is normally <5 mmHg (this represents the portion that is diluted with CO2-free gas from nonperfused alveoli).
	Should the oxygen analyzer always be trusted?	Yes - it is the only indicator of a hypoxic mixture. It needs to be trusted.
	How do you know gas concentration in a solution?	Gas Concentration = solubility coefficient + partial pressure
	What is the P50?	The O2 tension at which hb is 50% saturated and 50% unsaturated.
	What happens when the P50 decreases? What causes this to happen?	The oxy-hb curve shifts to the LEFT. hbg has an increased affinity for O2...does not offload it as easily. -Increased pH (lowering of H+, alkalosis) -Decreased Temp/ Hypothermia (less metabolic activity = less tissue need for O2) -Decreased PaCO2/ Hyperventilation (the low CO2 content of the pulmonary capillaries increases hb affinity for 02 facilitating uptake from the alveoli) -Decreased 2,3 DPG (carboxyhemoglobinemia, hypophosphatemia, fetal hb,stored banked blood, hypothroidism)
	What happens when P50 increases? What causes this to happen?	The oxy-hb curve shifts to the RIGHT. Hb has a lowered affinity for O2...offloads easily making O2 more available at tissues where it is needed. -Decreased pH (Increased H+, acidosis) -Increased temp/hyperthermia (increased prod of CO2 at tissues) -Increased PaCO2 (means increased metabolism = increased need for O2 at tissues; the high CO2 content of venous capillaries decreases hb's affinity for O2 facilitating offloading of O2 at the tissues) Increased 2,3 DPG (anemia, living at high altitudes, chronic hypoxemia, hyperthyroidsim)
	What does a right shift in the oxyhb disassoc curve do?	Decrease hb affinity for O2.
	What does a left shift in the oxyhb disassoc curve do?	Increase hb affinity for O2
	Total O2 content of blood is..	amount dissolved in plasma + amt bound to hb.
	What can account for deficiency in O2 delivery?	Low PaO2 (arterial O2 content), low hb concentration, or inadequate CO.
	T/F - CO2 is more soluble in blood than O2?	TRUE
	What med can inhibit transport of CO2 between cells and alveoli?	ACTZ - it is a carbonic anhydrase inhibitor
	The chloride shift is also known as???	The Hamburger Shift (not lying...it is in the book)
	Why does venous blood carry more CO2 than arterial blood?	B/c Deoxygenated hb has a 3.5x greater affinity for CO2 tha ndoes oxyhb. (Haldane effect.)
	Removal of O2 from hb in tissue capillaries causes hb to to act more like a_____.	base: by taking up H+ ions teh hb shifts the CO2-bicarb equation in favor of greater bicarb formation. (It makes room for MORE H+ - the byproduct of bicarb formation). As a direct result, DEOXY-hb also increases the amount of CO2 that is carried in venous blood as bicarb - as CO2 is taken up from the tissues and converted to bicarb to be carried in the blood, the total CO2 content of blood increases.
	Oxygenation of hb favors its actions as an______.	Acid: the release of H+ ions shifts the equation in favor of CO2 formation. Bicarb conc decreases as CO2 is formed and eliminated...so the toal CO2 concetent of blood decreases in the lungs.
	Oxyhemoglobin dissociation curve	Describes the relationship between the partial pressure of oxygen (PaO2) and the oxygen saturation of hemoglobin(SaO2/ SpO2). Increasing partial pressure of O2 increases hemoglobin's affinity for O2). pO2 - x axis (partial pressure of O2 in blood) SpO2 - y axis (hemoglobin % saturation) Hemoglobin can bind to 4 oxygen molecules. Hemoglobin's affinity for oxygen increases as successive molecules of oxygen bind to it. Hemoglobin's binding to oxygen is also increased by increasing the partial pressure of O2. PO2 changes as blood flows thru the body. The PO2 of the lungs is 100mmHg. The pO2 of the capillaries is 40 mmHg. Therefore, O2 binds to Hgb in the lungs (high affinity) and dissociates from Hgb in the capillaries (low affinity.) More molecules bind as the oxygen partial pressure increases until the maximum amount that can be bound is reached. (At partial pressure above 80 mmHg, the curve is relatively flat and the O2 saturation is not changed with increases in partial pressure.) Therefore, as this limit is surpassed in the lungs, very little additional binding occurs and the curve levels out as the hemoglobin becomes saturated with oxygen. Hence the curve has a sigmoidal or S-shape. Above 80 mmHg partial pressure (in the lungs) , the only way to increase O2 delivery to the tissues would be a PRBC transfusion to increase the amt of hemoglobin carrying it OR to give supplemental oxygen to increase the increase the amt of O2 dissolved in blood plasma (1-2% of O2 is carried this way.) The curve is assumed to occur at normal body condtions (pH of 7.4, PaCO2 of 40 mmHg, Temperature of 37 deg Celcius, Normal Levels of 2,3 DPG.
	What causes unreliable, incorrect, or less informative pulse ox readings?	1) Movement ---> Move sensor to a less active site. May be placed on forehead if pt is not ventilated and is not in the trendelenburg or supine position. 2) Poor Perfusion ---> Use an adhesive digit sensor or an R-15 nasal sensor if the pt is also immobile. Protect the sensor from heat loss. 3) Venous Pulsation ---> Position digit sensor at heart level. Avoid restrictive taping. If pt has elevated venous pressure, be careful to make sure it's reading arterial. 4) Dysfunctional Hemoglobins ---> Carboxyhemoglobin and methemoglobin are unable to carry oxygen. These also will be picked up by the pulse ox since it only discerns hb saturation...not which molecules are doing the saturation. Carboxyhemoglobin will cause false high readings. Methemoglobin will cause false low readings. 5) Anemia ---> SpO2 may be normal in an anemic pt who is HYPOXIC. Due to low hemoglobin. ---> Pulse ox may fail to read if Hgb is below 5. 6) Nail Polish ---> Skews results. Especially Brown, Blue, or Green 7) Intravascular Dyes ---> Skew SpO2 after injection. 8) Edema --> LIght scatters thru swollen tissue. Put sensor on non-edematous sites. ---> Use the RS-15 Nasal Sensor, the Adult Reflectance Sensor, or the D-YSE Ear Clip if necessary. 9) Optical Shunt ---> Some light from the sensor's light reaches the photodetector without first passing through the vascular beds. Make sure it's on right an completely. 10) Light Interference ----> Cover sensor with an opaque material in the presence of bright light sources, including direct sunlight, surgical lamps, infrared warming lamps and phototherapy lights. 11) Electrical Interference ---> Electrical devices release electrical impulses that may interfere with signal acquisition at the sensor site. ---> Plug the sensor in a wall outlet seperate from the other devices. Run it's cable away from and perpendicular to the other cables.

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