Mechanical Ventilation 101

Question 1

Key parameters for ventilation settings?

Answer 1

#Spontaneous or mandatory?
#Control variable (is ventilator targeting volume or pressure?)
#Breath trigger (patient versus timer versus both)
#Cycling

Question 2

Mandatory (versus spontaneous) ventilation modes?

Answer 2

Predetermine minimum minute ventilation

Question 3

VC-CMV vs VC-IMV

Answer 3

Volume control – continuous mandatory ventilation AKA AC (volume support on every breath)

Volume control – intermittent mandatory ventilation (only support if under certain number of breaths)

Question 4

PC-CMV? How does the ventilator know to open the exhalation valve?

Answer 4

Pressure control – continuous mandatory volume

#Inspiratory time is achieved
#Set I:E is met
#Set volume is achieved

Question 5

AC vs IMV vs PCV vs PC-IMV - Control type? Initiation? Termination?

Answer 5

AC - volume, patient/timer, volume
IMV - volume, patient/timer, volume
PCV - pressure, patient/timer, timer/I:E
PC-IMV - pressure, patient/timer, timer/I:E

Question 6

Pressure support ventilation (spontaneous mode) vs CPAP - Control type? Initiation? Termination?

Answer 6

PSV – pressure, patient, flow change (flow drops as lung gets full)
CPAP - None, patient, none

Question 7

For all modes of ventilation, can set?

Can set inspiratory flow rate in which settings?

Consent inspiratory time in which settings?

Answer 7

FiO2, PEEP

AC and IMV (volume control settings)

PCV and PC-IMV (pressure control settings)

Question 8

Pros and cons for AC?

Answer 8

#All breaths assisted
#Precise control of title volume and minute ventilation (good for unstable patients)

#Airway pressure not controlled during inspiration (can have high pressures in patients with low compliance or high lung resistance)
#Not a weaning mode

Question 9

Pros and cons for IMV?

Answer 9

Can be used as a waiting mode

#Patient discomfort with varying breath volume (not used much anymore)
#Increased work of breathing associated with spontaneous breaths

Question 10

PCV pros and cons?

Answer 10

No guarantee of minute ventilation

#Patient sets inspiratory flowrate 
#Useful in cases of severe hypoxemia
#Provide back up respiratory rate

Question 11

PSV (pressure support ventilation) Pros and cons?

Answer 11

#Patient control of respiration
#Excellent weaning mode

#No guarantee of minute ventilation
#No back up respiratory rate

Question 12

Once on ventilation, seven things to monitor?

Answer 12

Heart rate 
blood pressure
Oxygen saturation
Respiratory rate
EBG
Ventilator waveforms
Pulmonary mechanics

Question 13

Pressure time curve - measures pressure where? (Therefore, not helpful to determine?)

Answer 13

Opening of airway (not alveoli - cannot determine auto-PEEP)

Question 14

Compliance based on pressure-time graph?

Answer 14

Change in V/change in P

Tidal volume/(plateau pressure - PEEP)

Question 15

Resistance based on pressure-time graph?

Answer 15

Change in pressure/flow

(PIP-Plateau)/flow

Question 16

Normal compliance of respiratory system? Normal resistance?

Answer 16

40-70 mL/cm

5-12 cm/L/sec

Question 17

Elevated PIP - if resistance abnormal, problem stems from? (How to tell based on pressure-time graph?)

If compliance problem?

Answer 17

Problem with obstruction of the flow of gas (huge dip from PIP to plateau)

problem with the stiffness of the long (small dip from PIP to plateau)

Question 18

Differential for decreased compliance?

Answer 18

#Pneumonia
#ARDS
#Effusion
#Pneumothorax
#Right mainstem intubation

Question 19

Differential for increased resistance?

Answer 19

#Kink in ventilator tubing
#Obstructed ETT
#Asthma
#COPD

Question 20

Disease that can cause decreased compliance and increased resistance?

Answer 20

CHF

Question 21

Unable to be weaned off mechanical ventilation but normal resistance and compliance - suspect?

Answer 21

Neurological/neuromuscular junction problem

Question 22

When to use non-invasive ventilation before progressing to intubation?

Answer 22

Relatively stable and COPD, fluid overload (stuff that can be reversed quickly)

Question 23

Berlin definition of ARDS?

Answer 23

#Within one week of clinical consult
#Bilateral opacities on chest imaging
#Respiratory failure (not due to CHF or fluid overload)

Question 24

Mild versus moderate versus severe ARDS?

Answer 24

Mild: PaO2/FiO2 200-300 with PEEP over 5

Moderate: PaO2/FiO2 100-200 with PEEP over 5

Severe: PaO2/FiO2 under 100 with PEEP over 5

Question 25

Too much PEEP can lead to?

Answer 25

#Decreased lung compliance
#Pneumothorax
#Decreased cardiac output (obstruct Venus return)
#Shunt Blood to areas of poor ventilation

Question 26

Recruitment?

Answer 26

Open up alveoli with

PEEP 30 for 30 seconds
PEEP 49 for 40 seconds

Question 27

Indications for mechanical ventilation?

Answer 27

#Hypoxemia
#Hypercapnia
#Airway protection (altered, excessive secretions, unstable upper airway)