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Respiratory > Mechanical ventilation > Flashcards

Mechanical ventilation Flashcards

1
Q

What happens to normal preload during PPV?

A

reduced through two mechanisms:
-pressure differential between the abdomen and thorax is decreased
-get decreased venous return
-transmural pressures across ventricular wall change
-decreased compliance and decreased filling

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2
Q

How is decreased compliance depicted graphically on a volume control setting?

A

higher airway pressure per set Tv

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3
Q

How is decreased compliance depicted graphically on a pressure control setting?

A

lower tidal volume for given set pressure

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4
Q

Which triggering method is typically the default for most ventilated patients?

A

flow triggering- ventilator senses changes in inspiratory flow to initiate delivered breaths

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5
Q

What is the normal I:E ratio of a non-ventilated patient?

A

1:2 or 1:3
-inspiration is an active process, exhalation is a passive one
-remember in COPD and asthma exacerbations this is prolonged and needs to be adjusted

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6
Q

Which patient groups should you avoid permissive hypercapnia?

A

TBI and obstructive lung pathology

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7
Q

What vent changes can you make to make the I:E longer?

A

-increasing inspiratory flow
-decrease RR
-decrease Tv

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8
Q

What are advantes to a longer I:E? A disadvanage?

A

-prevents alveolar collapse
-improves gas exchange
-increases PO2

-also increases PCO2

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9
Q

In most patients what flow rate delivers adequate gas exchange?

A

60L/min

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10
Q

What type of flow time curve is seen for patients on a volume control setting? For pressure control?

A

-square wave
-descending ramp (increases inspiratory time)

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11
Q

On a pressure-volume curve what does the slope of the line represent?

A

compliance

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12
Q

What does the lower inflection point on a pressure-volume curve represent? The upper inflection point?

A

point where resistance to the patient’s airway is overcome
-shifts to the right if resistance is high
-the critical opening pressure of alveoli

point of maximal alveoli distention

PEEP should be set between these two points

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13
Q

How can you estimate the amount of auto PEEP occuring in a mechanically ventilated patient?

A

expiratory pause at the end of expiration (only if pt not breathing spontaneously)

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14
Q

On a flow/time curve how is auto-PEEP detected?

A

the expiratory flow curve does not return to 0 before the next breath is delivered

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15
Q

In VC mode what determines the airway pressures?

A

lung compliance

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16
Q

What is the equation for predicted body weight (PBW)?

A

female = 45.5 + 2.3[height(inches) - 60]
male = 50 + 2.3[height(inches) - 60]

female = 45.5 + 0.91[height(centimeters) - 160]
male = 50 + 0.91[height(centimeters) - 160]

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17
Q

What determines a patient’s plateau pressure?

A

lung compliance

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18
Q

How is plateau pressure checked?

A

ventilator pause and pressure check at the end of inspiration

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19
Q

What is the ARDSNet goal for plateau pressure?

A

< 35cmH2O

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20
Q

Why is hypercapnia detrimental to TBI patients?

A

elevated PCO2 leads to cerebral vasodilation which causes an elevation in intracranial pressures

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21
Q

What does SIMV stand for?

A

synchronized intermittent mandatory ventilation

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22
Q

What should be the main strategy for correcting hypoxia in a ventilated patient?

A

increasing the FRC
-due through manipulation of mean airway pressure (via increasing PEEP or delta P on PC, or by lengthening inspiratory time on I:E)

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23
Q

What should be the main strategy for correcting low PCO2 in a ventilated patient?

A

decrease RR or decrease Tv

24
Q

What should be the main strategy for correcting hypercapnia in a ventilated patient?

A

increase RR if not already tachypneic

25
Q

What can the high mean airway pressure alarm mean?

A

issues w/ lung compliance or airway problems

26
Q

What does an increase in peak inspiratory pressure relative to plateau pressure signify?

A

an issue with the airway itself
-ventilator tubing issue
-upper airway obstruction (bronchospasm or increased secretions)

27
Q

What does an elevation in plateau pressure relative to peak inspiratory pressure reflect?

A

issue with compliance

28
Q

What are some examples of causes of decreased compliance?

A

-PTX
-ACS
-ARDS
-PNA
-auto-PEEP dyssynchrony

29
Q

What are some disadvantages to using propofol for sedation in a ventilated patient?

A

-respiratory depression
-hypotension

30
Q

What are some disadvantages to using dexmedetomidine for sedation in a ventilated patient?

A

-bradycardia
-hypotension

31
Q

What is the MOA of propofol?

A

GABA receptor binder

32
Q

What is the MOA of dexmedetomidine?

A

alpha 2 receptor agonist

33
Q

Above what value for minute ventilation is spontaneous respiration unlikely to meet the metabolic demand?

A

10L/min (to know for weaning/extubation)

34
Q

What percent of patients who have intubated for >36hrs have laryngeal edema?

A

5-22%

35
Q

What percent of patients requiring mechanical ventilation die before discharge?

A

30-40%

36
Q

What is a Mallampati class 1 view?

A

uvula and soft palate are fully visible

37
Q

What is a Mallampati class 2 view?

A

hard and soft palate and upper portion of the uvula are visible

38
Q

What is a Mallampati class 3 view?

A

soft and hard palate and base of uvula are visible

39
Q

What is a Mallampati class 4 view?

A

only the hard palate is visible

40
Q

How is compliance measured?

A

delta V / delta P

41
Q

What are some complications of oxygen toxicity d/t high FiO2 settings and hyperoxia?

A

-interstitial fibrosis
-atelectasis
-tracheobronchitis

42
Q

What does APRV stand for?

A

airway pressure release ventilation

43
Q

What are some of the physiologic benefits to APRV?

A

-increased cardiac return
-improved oxygenation
-decreased sedation requirements
-improved lung aeration

44
Q

What is the basic method to wean APRV?

A

Lower Phigh and lengthen Thigh

45
Q

Which of the SBT parameters is the most sensitive and specific predictor of extubation success?

A

RSBI
-sens 97%
-spec 78%

46
Q

What are risk factors for reintubation after extubation?

A

-age > 65
-cardiac failure as a cause of resp failure
-APACHE score > 12 on day of extubation

47
Q

What is the 3-3-2 rule for intubation?

A

-3 fingerbreadths between the upper and lower teeth of an open mouth
-3 fingerbreadths from anterior tip of mandible to anterior neck (hyoid-mental distance)
-2 fingerbreadths between floor of mandible to thyroid notch on anterior neck (hyoid-thyroid cartilage distance)

48
Q

What is the calculation to determine ETT depth?

A

Chula formula
-ETT depth = 0.1(height in CM) +4

49
Q

Which patients are poor candidates when considering inverse ration ventilation?

A

those w/ COPD
-have increased risk of auto-PEEP
-want to do the opposite and increase expiratory time

50
Q

What is the function of adding PEEP to mechanical ventilation?

A

-increases alveolar surface area
-increases FRC
-increases PaO2
-decreases shunt fraction
-decreases hypoxic pulmonary vasoconstriction
-decreases cardiac output ( > 15)
-no change in PaCO2 or pH

51
Q

What is APRV?

A

-airway pressure release ventilation
-inverse ratio, pressure-controlled, intermittent mandatory ventilation
-allows spontaneous breathing

52
Q

What does phase 1 of capnogram (baseline) represent?

A

baseline inspired gas, normally devoid of CO2

53
Q

What does phase 2 of capnogram (upslope) represent?

A

-expired air
-displays the transition from dead space air flow to alveolar air flow

54
Q

What does phase 3 of capnogram (upper plateau of square wave) represent?

A

-partial pressure of CO2 exchanged at alveoli
-represents EtCO2

55
Q

What does phase 4 of capnogram (down slope) represent?

A

-inspiratory point in the ventilation cycle
-displays the transition from alveolar air flow to fresh air flow

56
Q

How do you calculate the airway resistance in a mechanically ventilated patient?

A

airway resistance = peak pressure - plateau pressure

57
Q

What driving pressure is strongly correlated to VILI?

A

driving pressure > 15

(driving pressure = plateau pressure - PEEP)

Respiratory (4 decks)

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