Mechanical Ventilation Flashcards

1
Q

Difference between the 2 types of non-invasive venilation

A

CPAP (continuous positive airway pressure) - no ventilatory assistance; just improves oxygenation by opening the alveoli and improves hemodynamics by decreasing afterload/preload to improve LV function

BiPAP: continuous positive airway pressure + set inspiratory pressure to assist the ventilatory muscles in their effort to generate inspiratory flow, decreasing the WOB

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2
Q

Indications for CPAP?

A

OSA
Cardiogenic pulmonary edema
Acute on chronic respiratory failure (i.e. COPD exacerbation)

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3
Q

Indications for BiPAP?

A

Acute on chronic respiratory failure (i.e., COPD exacerbation)
Other forms of ventilatory failure (neuromuscular disease)
Onc/bone marrow transplant patients w/pneumonia
Acute pulmonary edema (while diuresis works)

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4
Q

Contraindications to non-invasive ventilation?

A

Significant secretions
Facial trauma/burns/other anatomic problems w/mask seal
Aspiration risk

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5
Q

NNT w/non-invasive ventilation to avoid intubation?

A

2

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6
Q

Indications for MV?

A

Anyone who looks like they will die without intubation in the next few minutes

Ventilatory problems (apnea, impending respiratory muscle fatigue, etc.)
Oxygenation problems (hypoxia, etc.)
Protection of the airway
Secretions

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7
Q

List the 4 most commonly used modes of MV.

A

ACVC
ACPC
SIMV
PS

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8
Q

What 3 things does the mode determine?

A

How the ventilator initiates the breath (trigger)
How the breath is delivered (limit)
When the breath is terminated (cycle)

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9
Q

ACVC - trigger, limit, cycle?

A

Trigger: patient or time (negative airway pressure or inspiratory flow)
Limit: flow rate and pattern (constant = square vs. decelerating = ramp)
Cycle: volume (flow lasts until the set TV is delivered)

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10
Q

Compare square vs. ramp

A

Square: minimize inspiratory time to maximize expiratory time (i.e., obstructive lung disease)

Ramp: ventilate a heterogenous lung (i.e., ARDS)

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11
Q

Purpose of PEEP?

A

Prevent atelectasis
Decrease inspiratory WOB
Improve gas exchange

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12
Q

Advantages to ACVC

A

Low work of breathing - every breath is supported, TV is guaranteed

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13
Q

Disadvantages to ACVC

A

Tachypnea can lead to hyperventilation and respiratory alkalosis

Breath stacking can occur when the patient initiates a second breath before exhaling the first, leading to high volumes and pressures (can overcome w/optimal settings and sedation)

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14
Q

Compare SIMV and ACVC.

A

Like AC, SIMV delivers a minimum number of fully assisted breaths per minute that are synchronized w/patient effort. However, off-cycle breaths are not assisted.

Identical modes in patients who are not breathing spontaneously due to heavy sedation or paralysis

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15
Q

In SIMV, set a ___ RR to limit the opportunity for spontaneous breathing.

A

High

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16
Q

Advantage of SIMV?

A

“exercise” the respiratory musculature

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17
Q

Disadvantage of SIMV?

A

May increase WOB and cause respiratory muscle fatigue

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18
Q

What is set in ACPC?

A

RR, peak inspiratory pressure (PIP), inspiratory time (machine pushes in flow until PIP is hit and holds it for the inspiratory time)

19
Q

What is ACPC commonly used for and why?

A

ARDS, because it allows for more time for gas exchange

20
Q

Disadvantages to ACPCP?

A

Risk of barotrauma
Very uncomfortable
Frequently requires paralysis

21
Q

PS - trigger, limit, cycle?

A

Trigger: patient
Limit: pressure
Cycle: flow

Set PIP (patient sets RR and TV)

Inspiratory pressure is added to spontaneous breaths to overcome the resistance of the ETT or to increase the volume of spontaneous breaths

22
Q

Advantages of PS?

A

Reduce the risk of barotrauma, more comfortable

23
Q

Disadvantages of PS?

A

No back-up, cannot be used when comatose, sedated, or fluctuating mental status

24
Q

Typical vent settings?

A
Mode: ACVC
RR: 12
TV: 8-10 mL/kg IBW
FiO2: 60% or lower is non-toxic
PEEP: 5 cm H2O

Regardless of mode, you always have to set FiO2 and PEEP

25
Q

Techniques to improve tissue oxygenation while on MV?

A

Increase FiO2
Increase PEEP
Extend inspiratory time fraction

Bronchodilation
Decubitus, upright, or prone positioning
Decrease O2 requirements, improve O2 delivery
Remove pulmonary vasodilators

26
Q

Settings that affect PaCO2?

A

MV -> RR x TV

27
Q

Compliance = ?

A

TV/(Plateau pressure - PEEP total)

28
Q

Normal compliance in MV?

A

60-80 mL/cm H2O

<20 is stiff

29
Q

Causes of low compliance?

A
Pulmonary edema
ILD
Hyperinflation
Pleural disease
Obesity
Ascites
Pneumothorax
Atelectasis
Pneumonia
Bronchial intubation
30
Q

Resistance = ?

A

(Peak inspiratory pressure - plateau pressure) / flow

If flow is 60L/min = 1L/sec, remove from exation

Normal <15

31
Q

DDx - increased airway resistance

A

Kinking or plugging of ETT
Secretions
Bronchospasm

32
Q

Sedation options on ventilator?

A

PRN and opiate-based

33
Q

Strategies to improve hypoxemia in ARDS

A
  • Rx the cause
  • Increase FiO2
  • Diuresis (theoretically less capillary leakage)
  • Increase PEEP
  • Low TV (permissive hypercapnia)
  • Optimize PmVO2
  • Prone positioning
  • ECMO
34
Q

DDx - ARDS

A
Sepsis or infection (especially pneumonia)
Aspiration/near drowning
Trauma
Burns
Blood transfusion
S/p transplant of lungs, bone marrow
Drugs, alcohol
SIRS, including pancreatitis

3 most common - sepsis, pneumonia, aspiration

35
Q

Strategies to reduce auto-PEEP?

A

Signaled by persistent expiratory flow at the time the next breath is delivered

Measure by performing expiratory hold maneuver

  • Prolong expiratory time (decrease RR, increaase inspiratory flow rate)
  • If severe, disconnect from ventilator and manually decompress the thorax
36
Q

Requirements for extubation?

A
  • Rx underlying cause that lead to ventilation
  • Off pressors
  • <40% FiO2, 5 or less of PEEP
  • Neuro function intact
  • Any impending doom?
37
Q

Weaning parameters (isolated measure of respiratory muscle strength)?

A

Rapid Shallow Breathing Index (RSBI): RR/TV (in L)
-you want <104

Negative Inspiratory Force (NIF)
-you want more negative than -60 cm H2O (-20 to 0 is weak)

38
Q

Cause of HTN following intubation?

A

Stress

39
Q

Cause of hypotension following intubation?

A

Most commonly due to decreased venous return due to PPV

40
Q

Clinical criteria for ARDS?

A

Acute (w/in 7 days of known clinical insult or new/worsening respiratory symptoms)
Hypoxia (PO2/FiO2 <300)
Diffuse bilateral CXR opacities
No clinical hint of heart failure/fluid overload

41
Q

Type of respiratory failure in ARDS?

A

Type 1 (non-ventilatory) - hypoxemia +/- hypercapnia; disease in the lung itself

42
Q

Type of respiratory failure in COPD?

A

Type 2 (failure of alveolar ventilation) - decrease in MV or increase in dead space

43
Q

Mechanism of hypoxemia in ARDS?

A

Shunting; does not respond to supplemental O2