Classification of Ventilators Flashcards

Question

We have a patient that is on a ventilator in CMV mode and set to 12 breaths/min and the patient breathing at 16 breath/min. a) What type of breaths are being delivered b) What is the pt. is now only breathign 11 b/min

Answer 1

a) The ventilator will deliver **16 mandatory assisted breaths** to the patients. If in volume control then these breaths will be to a set volume. If it is in pressure control these breaths will be to a set pressure b) The ventilator will deliver 11 mechanical assisted breaths and 1 mechanical mandatory breath

Answer 2

The goal is to **deliver a set number of mandatory breaths and the patient can breath above the set rate with spontaneous breaths** Generally there is a window in which the patient can trigger a breath and if the patient doesn’t make the effort then a mandatory breath will be delivered at the end of the window This means that in SIMV can be **mandatory, assisted, and spontaneous breaths**

Answer 3

12 are mandatory assisted breaths and 4 are spontaneous breaths

Answer 4

All breaths are spontaneous They can be supported or unsupported by the ventilator

Answer 5

Mechanical Breaths only The mechanical breaths can be VC, PC, or PRVC

Answer 6

Mandatory and Assisted Breaths

Answer 7

Mandatory and Spontaneous Breaths

Answer 8

Mandatory, Assisted, and Spontaneous breaths

Answer 9

Spontaneous breaths only

Answer 10

Also known as mandatory breaths Breaths initiated and controlled by vent Breaths are time triggered

Answer 11

Not used often clinically as it does not allow for pt. efforts

Answer 12

Also have to set a sensitivity

Answer 13

Pt. needs full vent support but are also trying to breath on their own still Often inital mode in crisis management

Answer 14

Can deliver a minimum rate, and pt is able to set there own rate as well Will synchronize with pt. efforts Dependign on breath type can guarentee a pressure or volume

Answer 15

If RR too high can result in respirtory alkalosis Can increase pt. work if sensitivity not set correctly Poorly tolerated in awake pt. B/c the vent is doing a lot of the work there may be resp. muscle atrophy Higher MAP Cause/worsen auto PEEP

Answer 16

Delivered both mandatory and assistented mechanical breaths Also called Assist/Controlled (A/C) Can be CMV-VC, CMV-PV, CMV-PRVC

Answer 17

Mechanical breath Triggered by pt. but the rest is controlled by the vent

Answer 18

Triggered and cycled by pt. Can be supported or non-supported

Answer 19

The breath is triggerd, limited, and cycled by patient Resp muscles take all repsonsibility for breathing

Answer 20

Can be pt (assisted) or time (mandatory)

Answer 21

Mechanism used by vent to initiate the start of inspiration

Answer 22

1. Manual- Button on vent that allows operator to manually trigger a breath 2. Time 3. Patient-Pressure, flow, volume

Answer 23

Breath wil be riggered after a certain period of time Because the time period is set on the ventilator through the RR it is a **mandatory breath** Ex. If the RR is set at 12 b/min then the vent will deliver a breath every 60/12 =5 seconds So 5 seconds is the time trigger for a breath

Answer 24

* Trigger * Patient * Time * Limit * Flow * Cycle * Volume * Baselines * PEEP

Answer 25

Trigger-Patient or time Limit-Flow Cycle-Volume Baseline-PEEP

Answer 26

Trigger-Time or Pt. Limit-Pressure Cycle-Time Baseline-PEEP

Answer 27

Older ventilators in the IMV mode will deliver mandatory breaths regardless to patients efforts (unsynchronized to patient’s breathing), and this still may be used neonatal New ventilators always are synchronized to patients’ breathing. Thus the “S” for synchronization is dropped by the modern classification system. You still may sometimes need to use the SIMV designation.

Answer 28

This means that every 6 seconds (10/60) there will be a breath of 500 mL, and this breath will be delivered regardless of if the patient is already in the middle of a spontaneous breath This can result in ‘breath-stacking’ and asynchrony-both which cause pressures in the chest which magnifies all the negative physiological effects of PPV The patient however can make spontaneous efforts in between these 6 seconds

Answer 29

Variable amount of WOB for the patient Can be used for weaning May reduce the alkalosis assoc’d with A/C Limits respiratory muscle atrophy Lower MAPs

Answer 30

pt work if sensitivity not set appropriately PaCO2, fatigue and tachypnea if RR set too low WOB for S breaths unless PS is added

Answer 31

A mode that is purely spontaneous, meaning that there is only spontaneous

Answer 32

**Spontaneous Unsupported Breath (CPAP)** * Requires a baseline to be set * The patient breathes at this elevated baseline * RR, TI, Vt are the direct result of patient efforts **Spontaneous Supported Breaths** * Requires a baseline pressure to be set and for a support level to be set * i.e. Pressure Limit and Pressure Support Set * The RR, Ti are directly the result of the patients effort * Vt is based on the patient effort and the level of support set

Answer 33

PAV, tube compensation or CSV (VS)

Answer 34

For patient triggering the operator must set a sensitivity Maximum sensitivity means it is the easiest to trigger a breath Both spontaneous supported breaths and assisted breaths are patient triggered

Answer 35

## Footnote The patient’s inspiratory effort will causes a drop in pressure in the circuit, and when this pressure drop created exceeds the sensitivity setting a breath is initiated Eg. Sensitivity set at 2.0 cmH2O – the patient must create a drop in pressure of less than or equal to 2 cmH2O below baseline In newer vents this sensitivity is below baseline (ie. Below the PEEP level) In older vents this could be an absolute setting (doesn’t take PEEP into account)

Answer 36

The vent measure flow through a measurement of the flow leaving the inspiratory and flow entering the expiratory limb Normally you will have a continuous flow throughout the circuit When the patient makes and inspiratory effort the flow returning to the expiratory limb will decrease and this can trigger a breath Flow triggers is considered to be more sensitive than pressure triggering meaning that there is less work of breathing needed by the patient

Answer 37

* A limit variable is a parameter that can be reached and maintained at a present level before inspiration ends * Does not terminate inspiration * The limit variable can be pressure, volume, flow

Answer 38

* There are two ways in which pressure can limit inspiration * **Pressure is the control variable** * PCV, PS * **When flow is the control variable** * Commonly used in infants * Inspiratory flow results in a rise in pressure, the vent will allow this flow until a limit has been reach, then additional flow is vented out of the circuit through a pressure relief valve in order to maintain/limit the pressure that has been set

Answer 39

The most common volume-limited situation is during an inspiratory pause on a volume controlled breath The volume is limits throughout the pause The breath dose not cycle until the pause is up

Answer 40

Flow is the limit whenever the ventilator is in a flow controlled mode (ex. Volume control) This means that the present flow has a maximum valve that can be reached during a breath

Answer 41

The inspiratory phase will always ends when some variable reaches a present value This variable is called the cycle and can be: Pressure, Volume, Time, Flow For each mode there is a primary cycle variable, this is what will normally causes a breath to cycle. However other variables can cause a breath to back-up-cycle (pressure, volume, flow, or time) Eg. When you set a high-pressure alarm, the breath will cycle when it reaches this press

Answer 42

The ventilator ends inspiration after a predetermined volume has been delivered Volume cycling occurs in a **volume controlled setting** (when there is no inspiratory pause set) i.e. When the set Vt has been delivered the breath will end Volume can also act as a back up cycling mechanism-VTi Alarm

Answer 43

The ventilator will end inspiration after a predetermined pressure has been reached The gas is delivered during inspiration under pressure, and when the set pressure has been reached the ventilator cycles out of inspiration This is not a common primary cycling mechanism nowadays, **but is always available as a back up cycling mechanism**

Answer 44

The ventilator will end inspiration after a predetermined time has been reached The vent delivers gas to the patient until the set time interval is over Time-cycling is the primary cycling mechanism used in **PCV and PRVC** (and many other modes) Time is often a back-up cycling mechanism in PSV

Answer 45

The ventilator will end inspiration after a predetermined flow has been reached The positive pressure is provided to the patient until flow drops off to a pre-established level Inspiration ends when this low “terminal” flow is reached This is the primary cycling mechanism for PSV A flow-cycled breath is considered to be patient cycled!

Answer 46

The baseline variable is the parameter controlled during expiration Pressure is the most common parameter controlled Volume or flow could also be baseline variables but this is never seen Baseline pressures are always relative to atmospheric (as are all other ventilatory pressures)

Answer 47

PEEP= Positive End Expiratory Pressure This is the application of positive pressure through expiration By keeping the airway above atmospheric throughout the breathing cycle PEEP maintains the patient FRC and can help to improve residual capacity PEEP is referred to as CPAP when only using spontaneous breathing

Answer 48

A ventilator can use pressure, volume or time (and their derivatives) as conditional variables Conditional variables work on the “if-then” principle: If the value of a conditional variable reaches some preset level, then some action occurs to change the ventilatory pattern These require closed-loop modes

Answer 49

Alarms can be audible, visible, provide messages, or do a combination of these Certain alarms can affect breath delivery: High-pressure alarm in volume control ventilation will cycle the breath (ie. This alarm is a back-up cycle). This means that the breath has ended early Other alarms just function to alert the operator that a parameter is out of the set range Most alarms can be silenced by the operator while they work to correct the situation Some critical alarms cannot be silenced: Loss of power (pneumatic or electrical) and Vent inoperative

Answer 50

35 For the evita to set the high RR alarm you need to subtract you set RR from 35 and then that will be your high RR alarm

Answer 51

Full ventilatory support Acute control of patient ventilation (MV assured)

Answer 52

Lung protective strategies (ARDS) We use a lower tidal volume for patients with ARDS Normal tidal volume is 6-8 mg per kg of ideal body whereas with ARDS you can allow even 4 (permissive hypercapnia- to protect lungs)

Answer 53

Comfort with assured ventilation Patient capable of some WOB

Answer 54

Comfort, physiological advantages Patient has intact ventilatory drive Patient is capable of some WOB Considered to be a weaning model

Answer 55

Mandatory is a type of mechanical breath

Answer 56

Assisted Breath-Type of mechanical breath Supportive Breath-Type of spontaneous breath

Answer 57

Controlled, CMV-VC, IMV-VC, and CSV-VC Any Mode that allows for mechanical breaths

Answer 58

A mechanical breath that delivers a set Vt at a set flow rate or alternatively can set a Vt and a Ti (and a flow) Volume/Flow is the control variable-The volume and flow waveforms remain constant breath-to-breath while the pressure (and P waveform) will vary due to changes in the patients compliance and resistance As patient compliance will increases the tidal volume will still remain the same as it is set on the machine As resistance increase the tidal volume remains the same but the pressure needed to deliver the tidal volume will have to increase

Answer 59

Now PRVC is often the initial mode used clinically instead of CMV (VC)

Answer 60

If patient has there own respiratory drive it would only matter if you set a respiratory rate higher than what they are breathing if you set it lower nothing will be done to the patient

Answer 61

Guarantee a low minute volume You set the minimum RR and Vt Low WOB with CMV(VC) as long as sensitivity and flow are set appropriately Remember both mandatory and assisted breaths are allowed in CMV, if the patient wants more breaths the only work they have to do is to trigger the vent, the vent then controls the rest of inspiration This can also be a disadvantage as the respiratory muscle can atrophy very quickly

Answer 62

Pressures change in response to changes in the patient’s lung mechanics (i.e. Raw and CS) Flow is fixed (remember we are controlling this!) and may not meet changing demands of the patient May result in regional alveolar over-distension Alkalosis is also possible Air will follow the path of least resistance, meaning that it is possible for one part of the lung will become over inflated- Pressure control is one way to help get equal airflow throughout the lung because there will be an equalized pressure throughout the lungs

Answer 63

Will be set as 13 Will determine Total Cycle Time (TCT) which is equal to 60/RR

Answer 64

Tidal Volume=8 x IBW

Answer 65

The shape of the flow waveform chosen Often a square or decelerating flow waveform is used

Answer 66

Something you can set or observe Alternatively some vents will set VT, flow and TItotal. TIdyn is still determined by the VT and the flow, but now the TIpause is equal to the TItotal – TIdyn.

Answer 67

What happen when sensitivity is too high-Take more effort for the patient If it is too low-Too easy for the patient and might hyperventilate the patient (any leak in system machine thinks that they are trying to breath and then sill start a breath for their patient which is know as auto cycling) Set at 2?

Answer 68

Will be determined by Tidal volume and flow Tidyn=Vt (L)/Flow (L/sec)

Answer 69

TiTotal=Tidyn+Tipause

Answer 70

Will be determined through Titotal and TCT TE=TCT-Titotal TiTotal=Tidyn+Tipause

Answer 71

C= Vt (mL) / (Pplat-PEEP) [cmH2O]

Answer 72

R (cmH2O/L/sec) = (PIP- Pplat) [cmH2O] / Flow [L/sec]

Answer 73

MV = Rate [breath/min] \* Vt [mL)

Answer 74

TCT [sec/breath] = 60/Rate [breath per minute]

Answer 75

I:E = Ti/Ti : Te/Ti Answer should be given has whole numbers ex: 1:4.5

Answer 76

FiO2 required = (PaO2 Desired \* FiO2 Present) / PaO2 initial ABG

Answer 77

New PaCO2 Desired = Present PaCO2 – [ (pH Goal – pH Present) / 0.01}

Answer 78

MV required = (PaCO2 Initial \* MV) / PaCO2 desired

Answer 79

Max pressure that a ventilator can increase too and is often tied in with the high pressure alarm lEg. If the High Pressure Alarm is set to 35 cmH2O, the maximum pressure limit delivered on a PRVC breath would be 5 cmH2O below this, and if the vent cannot deliver the target volume within this pressure limit then there will be an alert alarm lThe ventilator will only adjust the delivered pressures in small increments lEg. 3 cmH2O per breath

Answer 80

By adding the PS we increase mouth pressure during inspiration and therefore increase the pressure gradient responsible for flow. Thus, more flow into the patient and a larger VT---all for the same spontaneous effort. ## Footnote As PS levels become high (eg\>20) it is approaching FVS-pt has to make a minimal effort to achieve a VT.

Answer 81

The transthoracic pressure gradient is the difference between the pressure in the pleural space and the pressure at the body surface, and represents the total pressure required to expand or contract the lungs and chest wall.

Answer 82

The transpulmonary pressure gradient is the difference between the pressure in the alveoli and the pleural space, and is responsible for maintaining alveolar inflation.

Answer 83

The transrespiratory pressure gradient is the difference between the atmosphere (Pm) and the alveoli, and is responsible for the actual flow of gas into and out of the alveoli during breathing.

Answer 84

Spontaneous supported breath Can occur in a purely spontaneous mode (CSV-PS) or added to the spontaneous breaths allowed in another mode [eg. SIMV(VC)+PS] The operator sets the inspiratory pressure (PS level), PEEP, FIO2, and sensitivity The patient determines the RR, TI, and inspiratory flow The VT is determined is determined by the PS set, the lung characteristics (R and C) and patient effort This mode looks very similar to PC but is dramatically different, as pressure at the mouth is only supplied during a patients’ spontaneous inspiratory efforts (flow cycled) Pmouth is positive but Palv is negative during inspiration Thus WOB is reduced but more physiologically similar to spontaneous breathing.

Answer 85

Usually called PSV (Pressure Support Ventilation) One of the most used modes of ventilation

Answer 86

Used for spontaneously breathing patients (they must still have their drive to breath) who: Require partial ventilatory support (PVS) not FVS- i.e. The patient is spontaneously breathing but requires some support to ¯ WOB Are being weaned from the ventilator May have a small VT or high RR

Answer 87

Patient sets own rate, TI, inspiratory flow and VT (very comfortable mode) Augments the patient’s tidal volume Increase the VT (with same pt effort) Can be used in conjunction with other modes that allow spontaneous breaths (to ¯ WOB of S breath) Maintains and builds respiratory muscle function (can be used for weaning)

Answer 88

Not to be used on patients with an inconsistent, irregular or unreliable ventilatory drive Need to protect the patient with alarms-especially an apnea alarm

Answer 89

**Trigger**: Patient only **Limit**: Pressure **Cycle**: Inspiratory Flow (Back-up time-cycle in case of leaks)

Answer 90

**PS level** **PEEP** **FIO2** **Sensitivity-**B/c there is pt. triggering, depending on the vent used this may be pressure-triggering, flow-triggering or volume-triggering

Classification of Ventilators Flashcards

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