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Respiratory Emergencies > Capnography And Pulse Oximetry > Flashcards

Capnography And Pulse Oximetry Flashcards

1
Q

Oxygen dissociation curve landmarks

A

PaO2 of 60mmHg = SaO2 of 90%
PaO2 of 40mmHg = SaO2 of 75%
The P50 is 27mmHg. The Hb has a saturation of 50% at a PaO2 of 27mmHg

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2
Q

Oxyhemoglobin dissociation curve; affinity

A

The strength of noncovalent binds between two substances, as measured by the dissociation constant of the complex

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3
Q

Oxyhemoglobin dissociation curve; left shift

A

Increased affinity for O2
Low pCO2, H+, 2,3-DPG, temp

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4
Q

Oxyhemoglobin dissociation curve; right curve

A

Decreased affinity for O2
High pCO2, H+, 2,3-DPG, temp
Low pH

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5
Q

Haldane effect

A

Describes the ability of hemoglobin to carry increased amounts of carbon dioxide in the deoxygenated state
A high concentration of CO2 facilitates dissociation of oxyhemoglobin

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6
Q

Bohr effect

A

An increase in CO2 results in a decrease in blood pH, resulting in hemoglobin releasing their load of oxygen
A decrease in CO2 provokes an increase in pH, which results in hemoglobin picking up more oxygen

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7
Q

Three types of pulse oximetry

A

-Photoelectric (optical) plethysmography
-Spectrophotometry
-Light emitting diodes (LEDs)

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8
Q

Machine can determine a baseline absorption

A

Tissue, venous blood flow

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9
Q

Dependent on pulsatile flow

A

Absorption changes due to increased arterialized blood flow, determine baseline absorption, subtracting this baseline, the machine is able to determine absorption by arterial blood

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10
Q

Photoelectric (optical) plethysmography

A

-Uses light absorption to produce waveforms from the blood pulsating in the vascular beds
-The amount of light absorbed is proportional to amount of blood flow
-Maximum absorption during systole and minimum during diastole

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11
Q

Spectrophotometry

A

-uses light wavelengths to measure light absorption through a substance, in our case blood
-the two wavelengths that are used in pulse oximetry are; red light - wavelength of 660nm, infrared light - wavelength of 920nm

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12
Q

Light emitting diodes (LED)

A

2 types of oximeter sensors are used; transmission, reflective

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13
Q

Measurement in pulse oximetry

A

-The saturation that we see is calculated
-This is called a functional saturation
-Functional saturation is the ratio of HbO2 to the total Hb available for binding with O2

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14
Q

Indications for using oximetry

A

-Noninvasive
-For continuous monitoring of arterial oxyhemoglobin saturation
-To monitor the adequacy of oxyhemoglobin saturation

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15
Q

Advantages of pulse oximetry

A

-Noninvasive
-Saturations can be monitored continuously at the bedside in real time
-Little training or knowledge is required to use the equipment
-Safe and usually quite accurate

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16
Q

Disadvantages of pulse oximetry

A

-Abnormal forms of Hb can not be measured
-HbCO is measured as HbO2 therefore false SpO2 readings
-Not as accurate as co-oximetry

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17
Q

Appropriate oximetry sites

A

-Finger, toe
-Ear
-Bridge of nose
-Forehead
-Infant; across the foot or hand

18
Q

Factors that effect the accuracy of pulse oximetry

A

-Motion
-Low perfusion
-External lights
-False nails / nail polish
-Wring types of sensor or incorrect placement
-Dysfunctional Hb, anemia
-Vascular dyes

19
Q

Accuracy of pulse oximetry

A

-Accurate witching 2-4% until SpO2 of 80
-False high readings with SpO2 <80

20
Q

PaCO2

A

Partial pressure of CO2 in arterial blood

21
Q

EtCO2

A

Measurement of the concentration of CO2 at the end of exhalation

22
Q

A-ADCO2

A

Difference between ETCO2 and PaCO2 (normally 2-5 mmHg)

23
Q

Capnometry

A

Measurement and the numerical display of CO2 at the patient’s airway

24
Q

Capnography

A

Measurement and waveform display of CO2 concentration at the patient’s airway

25
Q

Capnogram

A

Waveform display of CO2 throughout respiration

26
Q

Indications for ETCO2; intubated applications

A

-verifying ETT placement, monitoring ETT position during transport, head injury, CPR (effectiveness of cardiac compressions, earliest sign of ROSC, predictor of survival)

27
Q

Indications for ETCO2; non-intubated applications

A

-Bronchospastic disease; asthma, COPD
-Hypoventilation states
-Shock states; sepsis, hypovolemia, anaphylaxis, cardiogenic
-Hyperventilation

28
Q

Types of ETCO2 monitoring devices

A

-Spectrophotometry
-Colorimetric
-Mainstream
-Slidestream
-Microstream

29
Q

ETCO2 Spectrophotometry

A

Infrared absorption
Increased CO2 = increased absorption

30
Q

ETCO2 mainstream

A

-In-line with subjects exhaled gas via ETT
-Can pull on the airway (heavy)
-Slight increase in dead space

31
Q

ETCO2 slidestream

A

-Sample rate -150mL / min
-Slight lag in response time
-Slight increase in dead space
-Sample line can occlude with condensation

32
Q

ETCO2 microstream

A

-Newer units have a reduced sample rate - 50mL / min; reduces secretion aspiration
-Smaller bore sample line; quicker response time
-Incorporate nafion tubing to minimize H2O content
-Small sample cell (15uL); quick response time

33
Q

ETCO2 Capnogram; phase 1

A

Respiratory baseline
-Flat
-No CO2 present
-Corresponds with late inspiratory / early expiration part of respiratory cycle

34
Q

ETCO2 Capnogram; phase 2

A

Respiratory upstroke
-Mixture of dead space and alveolar gases

35
Q

ETCO2 Capnogram; phase 3

A

Respiratory plateau
-Represents air from ventilated alveoli
-Nearly constant CO2 level
-Highest point = ETCO2
-Recorded by capnometer

36
Q

ETCO2 Capnogram; phase 4

A

Inspiratory phase
-Sudden downstroke to baseline as atmospheric air is inspired

37
Q

Normal values

A

PaCO2: 35-45 mmHg
ETCO2: 35-45 mmHg

Difference between PaCO2 and ETCO2 is approx 2-5 mmHg

38
Q

Causes of Low ETCO2

A

-Mechanical; circuit disconnect, leaks
-Respiratory; airway obstruction, Bronchospasm, displaced ET tube, hyperventilation, mucous plug
-Circulatory; cardiac arrest, embolism, sudden hypovolemia
-Metabolic; hypothermia

39
Q

Causes of High ETCO2

A

-Mechanical; excessive mechanical dead space, faulty valve
-Respiratory; COPD, respiratory depression or insufficiency
-Circulatory; increased cardiac output
-Metabolic; hyperthermia, malignant hyperthermia

40
Q

Verifying ETT placement

A

-Sensitivity and specifics are up to 100%
-Can’t be used to detect bronchial or some hypopharyngeal misplacements
-Time to detect esophageal intubation using capnography; 1.6 +/- 2.4 sec
-Time to detection of esophageal intubation using clinical signs; 97 +/- 92 sec

41
Q

ETCO2 during CPR

A

-Square box waveform
-ETCO2 10-15 mmHg (possibly higher) with adequate CPR
-Change rescuers if ETCO2 falls below 10 mmHg
-Will detect ROSC

Respiratory Emergencies (6 decks)

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