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Principles I > respiratory monitoring > Flashcards

respiratory monitoring Flashcards

1
Q

what are simple observation monitoring techniques?

A
  • chest rise and fall
  • circuit bag movement and feel of the bag
  • Vt and end expiratory Vt
  • color of lips, nails, blood, conjunctiva
  • accessory respiratory muscles, increased work of breathing
  • respiratory rate and depth
  • rocking = obstruction
  • puffing = patent
  • airway noise
  • air felt on palm
  • precordial stethoscope sounds
  • tube fog
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2
Q

what is gas exchange?

A

addition of O2 to the blood and the elimination of CO2 from the blood

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3
Q

how can assessment of oxygenation and ventilation be invasive and non invasive?

A

non invasive: observation of chest rise and fall;

invasive: ETT insertion and direct measurement of ETCO2, Vt, etc

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4
Q

what respiratory monitors are provided by the anesthesia machine monitor?

A
  • Vt
  • FiO2 and FeO2
  • PiP meter, value and waveform
  • FiCO2 and ETCO2 and capnograph
  • RR (indicator of CO2 response curve)
  • Vm
  • gas analysis
  • inspiratory flow rates
  • misc. values like inspiratory trigger can tell you whether pt. has weak effort
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5
Q

describe the precordial and esophageal stethoscopes.

A
  • heavy weight chest piece placed on skin or esophageal temp probe used
  • custom fitted ear piece connects the tubing to either the chest piece or esophageal probe
  • confirms ventilation by breath sounds
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6
Q

what can the precordial and esophageal stethoscopes detect?

A

-stridor
-wheezing (bronchospasm)
-abnormal heart sounds (arrhythmias, new murmur from
air emboli)
-S3 gallop (CHF)
-absence of heart sounds (cardiac arrest, PEA)
*cannot detect diffusion abnormalities

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7
Q

when are esophageal stethoscopes contraindicated?

A

esophageal varicies

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8
Q

where is the correct placement of precordial and esophageal stethoscopes?

A

at the 4th intercostal space and left sternal border

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9
Q

what are you looking for when monitoring tidal volumes?

A
  • ensure achieving Vt between 6-8 ml/kg IBW
  • do not exceed PiP > 35-40 cmH2O
  • monitor bilaterally equal chest rise and fall
  • Vt need to be enough to control ETCO2, keep alveoli expanded, and deliver volatile anesthetic drugs
  • bellows descend and ascend
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10
Q

what are arterial blood gases?

A

measurement of PaO2, PaCO2, pH, Oxyhgb saturation, base excess and bicarb levels

  • assessment of oxygenation: PaO2 and Oxyhgb Sat
  • assessment of ventilation: PaCO2
  • assessment of acid-base status: pH, bicarb, base excess
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11
Q

what is hypoxemia?

A

decreased blood oxygen levels resulting from decreased delivery of oxygen from atmosphere to the blood (obstruction, decreased hypoventilation)

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12
Q

what is hypoxia?

A

decreased delivery of oxygen to the tissues (caused by hypoxemia)

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13
Q

what are the four categories of hypoxia?

A

1) hypoxemia: low FiO2, hypoventilation, V/Q mismatch,
shunt, diffusion limitations
2) anemic hypoxia: not enough Hgb (RBCs) picking up
O2 to take to tissues
3) circulatory hypoxia: not enough cardiac output to push
Hgb with O2
4) histiocystic hypoxia: cell won’t accept the delivery of
the O2 (cyanide poisoning)

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14
Q

what are some causes of hypoxemia?

A

-decreased inspired oxygen (altitude)
-hypoventilation (resp. center depression, NM disease,
resp. failure)
-shunt: pulm. (atelectasis, pneumonia, pulm. edema,
ARDS) or cardiac (patent foramen ovale)
-V/Q mismatch (airway secretions, bronchospasm)

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15
Q

what are some causes of hypoxia?

A
  • hypoxemia (lower than normal PaO2)
  • anemia
  • circulatory hypoxia (decreased CO, dec. local perfusion)
  • affinity hypoxia (dec. release of O2 from Hgb tissues)
  • histotoxic hypoxia (cyanide poisoning; won’t accept O2)
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16
Q

how do you estimate O2 consumption and O2 delivery to the lungs?

A
  • average O2 consumption is 3 ml O2/kg/min
  • current monitors allow you to determine if O2 delivery is adequate to meet O2 consumption
  • VO2 (consumption) = FiO2-FeO2 x Vm/wt in kg
  • DO2 (delivery to lungs) = FiO2 x Vm / wt in kg
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17
Q

whether O2 gets to the tissues depends on what?

A
  • Hgb
  • cardiac output
  • if sat is near 100%, increasing FiO2 will have little effect on delivery of O2 to lungs; cardiovascular system is the limiting factor in delivery O2 to tissue
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18
Q

describe pulse oximetry.

A
  • dual wavelengths of light (660 nm and 940 nm) pass through tissue and vascular beds via LED
  • tissue and blood absorb light passing through
  • a ratio is calculated at the two wavelengths of light
  • requires pulsatile blood flow (SpO2)
  • can be placed on finger, toe, earlobe, forehead; infants on hand and foot
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19
Q

what are some causes of error in pulse oximetry?

A
  • elevated Hgb species other than Hgb and Oxyhgb
  • improper fitting probe causing light shunt as light is reflected from skin results in falsely low SpO2
  • SaO2 < 60% results in falsely low SpO2
  • poorly perfused areas
  • Hgb concentration (anemia and hypoxemia falsely low)
  • IV methylene blue dye (dramatic falsely low)
  • blue nail polish w/ light absorbance near 660 nm lead to falsely low
  • ambient fluorescent light
  • excessive motion
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20
Q

what can result in a falsely high SpO2?

A

-elevated Hgb species other than Hgb and Oxyhgb
*COHgb absorbs light similarly, resulting in false high
*MetHgb similar to Hgb: if SaO2 > 85% SpO2 will be
low, if SaO2 is < 85% SpO2 will be high
*not affected by fetal hgb or sickle cell
-ambient fluorescent light

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21
Q

what can result in a falsely low SpO2?

A
  • improper fitting probe
  • SaO2 <60%
  • poorly perfused areas
  • low flow in cardiac arrest and vasoconstriction
  • low flow hypothermia, low CO
  • anemia and hypoxemia
  • IV methylene blue dye
  • blue nail polish
  • excessive motion
22
Q

what are some oximetry probe sites?

A
  • finger (most common)
  • toe (desat/ resat detection not as fast)
  • nose (hypothermia, vasopressors; central location makes desat/resat better than peripheral; unreliable with trendelenberg)
  • earlobe (useful when finger, toes not available; failure right higher)
  • tongue (burn pts.; desat/resat quicker than finger)
  • cheek (more accurate than finger; good for poor perfusion states; desat/resat rapid)
23
Q

describe gas and agent analysis.

A
  • some newer gas analyzers are able to recognize different agents while older models can’t
  • older gas analyzers require the anesthetist to select which agent they use and calibrate
  • *failure to select the appropriate agent can cause OD or underdose of agent
  • gas analyzers are pre-calibrated for specific agents
  • most newer analyzers calibrated for volatiles and N2O and will calculate MAC and additive MAC if N2O in use
24
Q

what is capnography?

A

measurement of CO2 during ventilatory cycle

**CO2 is affected by VO2 (O2 consumption), CO2 transport, alveolar ventilation

25
Q

describe capnography.

A
  • CO2 is measured by infrared absorption
  • CO2 gas is measured and a waveform over time is created using the CO2 value
  • mainstream: measurement chamber is placed directly at the airway
  • sidestream: airway gas is aspirated through tubing to a measurement chamber
26
Q

what causes CO2 production, increasing ETCO2?

A
  • fever
  • physical activity
  • seizures
  • sepsis
  • hyperthyroidism
  • trauma and burns
  • high carbohydrate diet
27
Q

what causes decreased elimination of CO2, increasing ETCO2?

A

hypoventilation

28
Q

what decreases ETCO2 due to inability to get CO2 back to the lungs for elimination?

A

-hypotension and decreased CO: not carrying CO2 back
from tissues to heart and lungs
-right to left pulmonary shunt: bypasses the lungs

29
Q

what decreases CO2 production, decreasing ETCO2?

A
  • hypothyroidism
  • paralysis, motionless
  • hypothermia
30
Q

what causes an increase in CO2 elimination, decreasing ETCO2?

A

hyperventilation

31
Q

if there is a sudden decrease in ETCO2, what should you suspect?

A

-no flow, like with a drop in blood pressure

32
Q

what mirrors CO2 level?

A

VO2

33
Q

how does VO2 indicate what ETCO2 will show?

A

bigger O2 consumption (bigger difference in FiO2 and FeO2) end in larger ETCO2 (increased metabolic state)

34
Q

cardiac status and ventilator settings affect what with CO2?

A

-elimination and evacuation of CO2

35
Q

patient metabolic status affects what with CO2?

A

production

36
Q

describe the normal capnograph.

A

Phase I: dead space, expiration (no CO2 d/t no gas exchange)
Phase II: mixed dead space and alveolar gas exchange (CO2 rising)
Phase III: alveolar gas expiration; plateau (CO2 peaks)
Phase IV: upswing that may be seen at end of III
Phase 0: inspiration (CO2 drops down to 0)

37
Q

describe the capnograph in non-intubated patients.

A
  • use special nasal cannula designs that allow sidestream ETCO2 measurement
  • nasal cannula sidestream connection can be created with normal cannula
  • mixed gases of air and oxygen occur
  • inadequate sampling
  • mouth breathers will cause low readings
  • inaccurate low readings and waveforms are common d/t contaminated exhaled gases are mixed with ambient air
  • ETCO2 wave usually has no plateau phase
38
Q

what causes increased PiP and plateau pressure (PP)?

A
  • increased tidal volume
  • decreased pulmonary compliance
  • pulmonary edema
  • trendelenburg
  • pleural effusion
  • ascites
  • abdominal packing
  • peritoneal gas insufflation
  • tension pneumothorax
  • endobronchial intubation
39
Q

what causes increased Pip with unchanged Pplat?

A
  • increased inspiratory gas flow rate
  • increased airway resistance
  • kinked ETT
  • bronchospasm
  • secretions
  • foreign body aspiration
  • airway compression
  • ETT cuff herniation
40
Q

what is static lung compliance?

A
  • during times of NO gas flow
  • measured using plateau pressure (end inhalation prior to exhalation; always lower than Peak pressure)
  • measure of lung compliance
  • constant unless lung compliance changes
41
Q

what is dynamic lung compliance?

A
  • during times of gas flow (active inspiration)
  • measured using peak pressure
  • measures lung compliance plus airway resistance
  • airway resistance contributes to a decrease in dynamic compliance
  • airway resistance can change from breath to breath
42
Q

what is Peak inspiratory pressure (PiP)?

A

highest circuit pressure during inspiratory cycle

*indicator of dynamic compliance when flow is occurring

43
Q

what is plateau pressure (Pplat)?

A

pressure during inspiratory pause, no flow

  • indicator of static lung compliance
  • never greater than PiP
44
Q

an increase in Pplat indicates what?

A
  • decreased compliance of lungs
  • stiff and rigid, no recoil OR too much volume
  • pt moved to trendelenburg; opioids lead to stiff chest; insufflated abdomen during lap chole
45
Q

an increase in Pip indicates what?

A
  • increased inspiratory flow
  • increased airway resistance
  • increased secretions or kinks
46
Q

describe pressure volume loops.

A
  • indicator of lung compliance (change of volume for a given change in pressure)
  • yields info regarding leaks, lung over inflation, and obstruction
  • loops move based on positive or negative pressure
  • counter-clockwise during positive pressure ventilation
  • clockwise during spontaneous respiration
  • slope indicate compliance
47
Q

how does pressure move loops?

A

higher pressure moves loop farther right

48
Q

how does slope indicate lung compliance?

A
  • flatter slope indicates decreased compliance

- steeper slope indicates increased compliance

49
Q

describe flow volume loops.

A
  • normal loop looks like an upside down ice cream cone

* clockwise direction

50
Q

what changes with flow volume loop in restrictive lung disease?

A
  • normal shape
  • lung volumes are smaller
  • flows are reduced
51
Q

what changes with flow volume loop in obstructive lung disease?

A
  • shape is caved in which indicates expiratory obstruction
  • lung volumes are larger
  • flows are reduced
  • *obstructed flow will always yield a flatter, less round shape as air flow is impeded
52
Q

what three types of obstructions can be seen on flow volume loops?

A
  • fixed (tumor) obstruction in and out: impedes inspiration and expiration
  • extrathoracic : airway collapses on inspiration d/t increased negative pressure and opens on expiration with positive pressure (inspiratory impeded)
  • inrathoracic: airway collapse on expiration with positive pressure (COPD and emphysema) (expiratory impeded)

Principles I (18 decks)

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