Mechanical Ventilation

Question 1

VE = Minute Ventilation

Answer 1

Vt x RR = VE expressed in L/min
VE range is 4-8L/min (Infant and Adult)

Question 2

Vt = Tidal Volume

Answer 2

Normal vol of air inspired during each normal quiet respiratory cycle.
Should be enough to overcome dead sapce.
*Starting Vt range is 6-8mL/kg
**Lung protectant 4-6mL/kg

Question 3

Ideal Body Weight calculation

Answer 3

(2.3 x patient height in inches) + 50kg(male);45.5kg(female)

Question 4

Obstructive vs Injury?

Answer 4

Obstruction- COPD and Asthma(Ventilation problem-lower RR/>I:E ratio)
Injury- everything else: Pneumonia, ARDS, CHF, trauma..

Question 5

Alveolar minute ventilation

Answer 5

calculation: Vt x RR - 1mL x IBW in lbs(alveolar VE)
Alveolar VE range = 4-8L/min
Average adult Alveolar VE = 5L/min

Question 6

Anatomincal deadspace

Answer 6

calculation: 1mL x ideal body weight in lbs OR 33% of Vt.
*average anatomincal dead space in adults is 150mL/breath

Question 7

FIO2

Answer 7

Maintain the lowest FIO2 possible in order to maintain proper tissue oxygenation and prevent ROS or free radicals that cause cell damage.
*high FIO2 is important with trauma patients and pregnancy.

Question 8

Absorptive atelectasis

Answer 8

FIO2 concentration that is too high can cause nitrogen washout and lead to alveolar collapse.

Question 9

Vte(exhaled tidal volume

Answer 9

Most accurate measurement of the volume received by the patient.
Confirms actual volume received by the patient.
Can identify air trapping or a leak.
should be within =/- 50mL of the Vt

Question 10

DOPE

Answer 10

Disconnection; dislodgement(circuit, ETT)
Obstructions; suction, kinks
Pneumothorax(tension); Pplat >30?
Equipment; troubleshoot vent settings

Question 11

Mechanical Deadspace

Answer 11

The loss of volume during a VOLUME breath in the vent circuit based on expansion.
Adult circuit: 2mL x PIP
Ped circuit: 1mL x PIP

Question 12

Trigger(sensitivity)

Answer 12

Flow trigger based ib bias flow(very sensitive)
Trigger setting is shown in L/min(10L/min)
*Pressure Triggers are less sensitive and more commonly used

Question 13

I:E Ratio

Answer 13

Time spent in inspiration. Inspiration is always active so it requires less time than expiration.
*Respiratory cycle time is 3.75sec.
Add I and E then divide 3.75 by the sum. This gives you your I time.
Adults I:E= 1:2 Peds I:E = 1:3 with I-time of 0.3-0.7
*Obstructive lung 1:4 or greater. Asthma may benefit from 1:1

Question 14

Expiratory Time Constant

Answer 14

Time it takes for the lungs to fill or empty(suggested time 0.3sec)
Calculation - Raw/flow x time constant = expiratory time needed
Resistance or Raw = PIP-Pplat
Flow is L/min simplified to L/sec

Question 15

PIP

Answer 15

Peak Inspiratory Pressure
*Attempt to keep <35cmH2O in the majority of patients(COPD or Asthma patients may need higher PIP)

Question 16

Plateau Pressure(Pplat)

Answer 16

Measures pressure when inspiratory flow is zero
Applied in VOLUME breath only
Inspiratory hold 0.5 sec
**Goal is <30cmH2O will always be <PIP(or the vent is broken)
Determines alveolar health
Can determine if a simple pneumo is progressing to tension pneumo.

Question 17

Causes of a high PIP and high Pplat

Answer 17

PIP: Upper airway obstruction, suctioning, kinked ETT, kinked vent curcuit, pt trigger(cough), poor sedation, or disease process(asthma, COPD)
Pplat: Pt position(Trendelenburg/pushing things against the diaphragm), Tension Pneumo, abdominal compartment syndrome, Pregnancy, PE, ARDS, or Pulmonary effusions.
*If you have a trauma patient with a suspected/confirmed pneumo and the PIP/Pplat increase, DECOMPRESS THE CHEST!!

Question 18

How to decrease PIP/Pplat in a medical patient

Answer 18

Adjust the Vt to a protective setting/calculation. Potentially need to swap from a VOLUME to a PRESSURE controlled ventilation(IPAP + EPAP)

Question 19

Driving pressure

Answer 19

The difference between Pplat and PEEP(Pplat-PEEP=Driving pressure).
Attempt to keep driving pressure<15cmH2O
Decrease Vt<4-6mL/kg
Increase PEEP
Only in ARDS pt

Question 20

PEEP

Answer 20

Peak End Expiratory Pressure
Pressure applied to the airway at the end of expiration to maintain alveolar recruitment
Quickest way to increase oxygenation
Improves oxygenation by reducing V/Q mismatch

Question 21

Volume ventilation mode

Answer 21

Volume breath is a set volume that is considered mandatory
Set based on IBW
Standard:6-8mL/kg
Lung protection:4-6mL/kg
Monitored with PIP and Pplat

Question 22

Pressure ventilation mode

Answer 22

Pressure breath is a pressure set based on inspiratory pressure(PIP)
Adult start: 20cmH2O(IPAP + EPAP)
Ped start: 10-15cmH2O
Monitored with exhaled tidal volume(Vte)
Compliance based
Reduction in potential barotrauma

Question 23

Assist Control(AC)

Answer 23

Delviers a preset tidal volume & RR
It will deliver preset Vt via volume
Will deliver a pressure where a Vt is targeted
>Indications: normal respiratory drive accompanied by conditions causing increased work of breathing OR Apneic patients

Question 24

Synchronized Intermittent Mandatory Ventilation(SIMV)

Answer 24

Patient receives a set # of breaths at a preset tidal volume, allowing for spontaneous breathing between mandatory breaths
Pt able to trigger own breath based on sensitivity setting
>Indications: Often used with pressure support(PS), Weaning, Increased comfort, and reduced change of hyperventilation.
Could have risk for increase muscle fatigue

Question 25

Pressure Support

Answer 25

SIMV application only
Reduction of deadspace
Applied during spontaneous breath only
Decreased effortand workload on patient
Assists in the weaning process
Starting pressure 10cmH2O(PS + PEEP=10)
*Small changes(1cmH2O = 75-150mL of added potential Vt)
*Spontaneous exhaled tidal volume(spVte) should not exceed 75% of set Vt. Provide more sedation if spVte is >75% of Vt.

Question 26

Rise Time(variable)

Answer 26

Only applies in pressure supported breath(SIMV) or pressure control.
Pressure = the ability to apply Rise Time
Faster Rise Times: (0.1-0.237sec)
Short Inspiratory time(Ti) or Hypoxic/air starved
Slower Rise Times: (0.316-1.0sec)
Small ETT, Bronchospasm, or Pressure Overshoot.
**Your Rise time has to be longer than your Ti or the vent will terminate the breath.

Question 27

Flow Termination

Answer 27

*Only applied in a pressure supported breath
Limits the amount of flow in a breath displayed as a percentage.
EX: 100L/min of flow- if you set flow term to 25%, the patient only receives 75% of the 100L/min setting.
Higher Flow Term % = less Vt and lower Flow Term % = more Vt.

Question 28

Injury Approach

Answer 28

Vt = protection
6-8mL/kh based on IBW
4-6mL/kg for Pplat >30cmH2O(adult only) >4mL/kg go to P not Vol.
–Should not be altered to fix ventilation
–Only gets changed for lung protection to present barotrauma. Look at Pplat pressure.
Settings: RR- 100mL/kg/min = 16bpm, PEEP-minimum 5cmH2O, FiO2- lowest to maintain SpO2 >93%, Pplat- <30cmH2O

Question 29

Obstructive Approach(COPD Asthma only)

Answer 29

RR=protection
RR–10-12bpm. 6-8mL/kg based on IBW.
*COPD I:E ratio >1:4.1 *Asthma - consider I:E ratio of 1:1.1
Rate is not changed to increase VE;Vt only
Expiratory time constant- 0.3sec
Settings: Vt- 6-8mL/kg, Vol mode if available, RR- 10-12, PEEP- minimum 3-5cmH2O, and FiO2- lowest to maintain SpO2 >93%

Question 30

Quiz question
A Pplat of how many mmHg is considered abnormal?

Answer 30

> 30

Question 31

Quiz question
Your patient is demonstrating a sudden increase in PIP, with a normal P plat. The most likely cause of this phenomenon would be what ?

Answer 31

Answer: patient coughing against the vent

Explanation : when looking at vent pressures, always look first at PIP. This looks at volume, compliance, airway, resistance, and flow. If PIP is high and you check your Pplat, which reflects low, you know this elevation and pressure is due to something above the Carina. If both your PIP and Pplat are high, you know that the increase in pressure is caused by a change in upper airway as well as an Alveolar issue.

Question 32

Quiz question
When using a pressure control mode of delivery, what can you expect?

Answer 32

Answer: the vent triggers until a preset pressure limit is reached

Explanation: pressure delivery ventilation is the most gentle way to ventilate your patience. Always remember your patience are sick and have baby lungs. Pressure modes of ventilation are based on compliance and will only apply a pressure based on that compliance.

Question 33

What is Pinsp?

Answer 33

(Pinsp)Total inspiratory pressure= PEEP + pressure support

Question 34

Quiz question
When applying pressure support in a patient on SIMV, what is the stopping point for allowing the patient to take a spontaneous breath?

Answer 34

Answer: Do not allow the patient to exceed 75% of the set Vt