VENTILATOR

October 05, 2017

VENTILATOR

VENTILATOR

Ventilator Machine: is the machine designed to move breathing air into and out of the lungs, to provide breathing for patient who is physical unable to breath or breathing insufficiently.

CATEGORIES OF VENTILATORS.

There are two categories of ventilator in which ventilator machine is applied,

1:NONINVASIVE VENTILATOR.

These devices provide breathing support through an external interface such as a mask or nasal prongs.

2:INVASIVE VENTILATOR.

Patients on long term ventilation may require ventilation through an endotracheal tube inserted through the mouth or nose or through a tracheotomy tube inserted into an incision in the neck.

objectives of mechanical ventilation are

to deliver adequate minute ventilation (VE) and oxygenation without:

1. damaging the lungs

2. impairing circulation

3. causing unnecessary discomfort

-Selecting the most appropriate method and mode will help meet these objectives

invasive mechanical ventilation

1. ETT

2. Tracheostomy

non-invasive mechanical ventilation

1. CPAP

2. BIPAP

3. IPPB

4. Iron Lung (negative pressure)

5. Cuirass (negative pressure)

3 basic mode types

1. CMV (controlled mandatory ventilation) [Controlled]

2. IMV (intermittent mandatory ventilation)

3. CSV (continuous spontaneous ventilation)[Spontaneous]

Modes of Ventilation

- CMV (Controlled)

1. all breaths are mandatory and can be volume or pressure targeted (time triggered breath) - can be dysynchronous with the vent. Don't use much anymore other than paralyzed patients

2. assist/controlled ventilation - when mandatory breaths are either time triggered or patient triggered (i.e. if pt. initiates breath, they'll get the volume or pressure that is set)

what does the volume waveform look like in CMV (Controlled)

shark fin

other uses for CMV (Controlled) in non-paralyzed patients

1. seizure activity

2. inverse I:E ventilation

3. patient is fighting (bucking) the ventilator

4. complete rest for the patient

CMV (Assist/Control Ventilation) general info

1. a time or patient triggered CMV mode in which the operator sets a minimum rate, sensitivity level, type of breath (volume or pressure)

2. the patient can trigger breaths at a faster rate than the set minimum, BUT only the SET volume or pressure is delivered with each breath

indications for CMV Assist/Control Ventilation

1. patients requiring full ventilatory support

2. patients with stable respiratory drive

advantages of CMV Assist/Control Ventilation

1. decreases WOB (Pt. just needs to trigger, than vent will deliver)

2. allows patients to regulate respiratory rate

3. helps maintain a normal PaCO2

complications of CMV Assist/Control Ventilation

alveolar hyperinflation (hiccups, seizures, tremors can trigger breaths leading to alveolar hyperinflation)

Pressure Control can be used in which modes

CMV or (S)IMV modes

what are phase variables for Pressure Control

1. trigger (time or patient trigger)

2. Limit (pressure limited)

3. Cycle (time cycled)

what is shape of waveform for pressure controlled for a pressure/time graph

square tops

what is Pressure Controlled CMV AKA

1. pressure controlled (PCV)

2. AC-PC

what are some characteristics of pressure controlled ventilation

1. time or patient triggered

2. pressure targeted (limited)

3. time cycled

what does the operator set in pressure controlled vent.

the operator sets the length of inspiration (TI), the pressure level and the back up rate of ventilation

in pressure controlled, what is VT (tidal volume) based on

1. the compliance and resistance of the patients lungs

2. patient effort

3. set pressure

in pressure controlled, volume can be

very variable (compliance Raw)

Pressure Controlled CMV-AC advantages

1. airway pressure is limited (avoid barotrauma)

2. maximum inspiratory pressure is set at about 30-35 cmH2O, especially helpful in patients with ARDS

3. allows application of extended inspiratory time, which may benefit patients with severe oxygenation problems

4. usually reserved for patients who have poor results with a conventional ventilation strategy of volume ventilation

Volume Control

which modes can it be used in

1. CMV

2. (S)IMV

what are Volume Control phase variables

1. trigger (time or patient triggered)

2. Limit - volume limited

3. cycle - volume cycled

in Volume Control, how do pressure and Volume waveforms look

similar (triangular)

characteristics of Volume Control waveforms

1. time triggered

2. descending flows (although can have constant flow which would show squared off flow waveform)

3. volume targeted

in flow waveform what is above and what is below the x-axis

inspiration is above x-axis

expiration is below x-axis

what ends a pressure controlled breath

time

what ends a volume controlled breath

volume

in Volume Ventilation, operator sets

1. volume

2. PEEP

3. Rate

4. Flow

5. FIO2

in Volume Ventilation, ventilator determines

pressure required

volume ventilation advantages

1. guaranteed minute ventilation

2. may be more comfortable for patient

volume ventilation drawbacks

not optimal for poorly compliant lungs (barotrauma from possible high pressures)

in Pressure Ventilation, operator sets

1. PIP

2. PEEP

3. Rate

4. I-time (instead of flow)

5. FIO2

in Pressure Ventilation, ventilator determines

tidal volume given

IMV is

Intermittent Mandatory Ventilation

IMV is in general

1. periodic volume or pressure targeted breaths occur at set interval (time triggering)

2. between mandatory breaths, the patient breathes spontaneously at any desired baseline pressure without receiving a mandatory breath

3. in patient triggered breaths, the patient only gets volume that they get with spontaneous breath

our Boards say that SIMV is a good

weaning mode

(maybe not so much in real world)

indications for IMV and SIMV

1. facilitate transition from full ventilatory support to partial support

advantages of IMV and SIMV

1. maintains respiratory muscle strength by avoiding muscle atrophy

2. decreases mean airway pressure

3. facilitates ventilator discontinuation (weaning)

IMV complications

1. machine and spontaneous rate may be asynchronous causing "stacking"

2. when used for weaning, may be done too quickly and cause muscle fatigue

SIMV is

Synchronized Intermittent Mandatory Ventilation

SIMV general info

operates in the same way as IMV EXCEPT that mandatory breaths are normally patient triggered, rather than time triggered.

Operator sets the volume or pressure target and mandatory breaths are synchronized with the patient

As in IMV, the patient can breathe spontaneously through the ventilator circuit between mandatory breaths

SIMV helps to avoid

stacking

Synchronized IMV - respiratory rate

at a predetermined interval (respiratory rate) which is set by the operator, the ventilator waits for the patients next inspiratory effort

when the ventilator senses the effort, the ventilator assists the patient by synchronously delivering a mandatory breath

SIMV - if the patient fails to initiate ventilation

within a predetermined interval, the ventilator provides a mandatory breath at the end of the time period

what are the three basic means of providing support for continuous spontaneously breathing during mechanical ventilation

1. Spontaneously breathing

2. CPAP

3. PSV (Pressure Support Ventilation)

in spontaneous modes, patients can

breathe spontaneously through a ventilator circuit (i.e. patient can't maintain patent airway but can breath fine)

spontaneous modes advantage

ventilator can monitor the patient's breathing and activate an alarm if something undesirable occurs

spontaneous mode disadvantage

may increase patient's WOB with older ventilators

Spontaneous Modes
- CPAP

ventilators can provide CPAP for spontaneous breathing patients

this is helpful for improving oxygenation in patients with refractory hypoxemia and a low FRC

CPAP setting is adjusted to provide the best oxygenation with the lowest positive pressure and the lowest FIO2

Spontaneous Modes
- CPAP Advantages

ventilator can monitor the patient's breathing and activate an alarm if something undesirable occurs

PEEP commonly implies that

the patient is also receiving mandatory breaths from a ventilator

what do we often use for a term if patient is spontaneously breathing

CPAP

PEEP is intended to improve

oxygenation, not to provide ventilation

what two vent "settings" affect oxygenation

1. PEEP

2. FIO2

what vent "setting" affects ventilation

1. tidal volume (VT)

2. Rate

Pressure Support Ventilation - PSV
Is it really a true mode?

more of an add-on

can add PS to any spontaneous mode (CPAP, SIMV)

i.e. weaning - PS with CPAP

Pressure Support Ventilation - PSV
general info

1. patient triggered

2. pressure targeted

3. flow cycled

4. requires a patient with a consistent spontaneous respiratory rate

5. the ventilator provides a constant pressure during inspiration once it senses that the patient has made an inspiratory effort

Pressure Support Ventilation - PSV
Indications

1. spontaneously breathing patients who require additional ventilatory support to help overcome:

a) increase WOB, decrease compliance, increase Raw

b) respiratory muscle weakness

2. weaning (either by itself or in combination with SIMV)

PSV Advantages

1. full to partial ventilatory support

2. augments the patient's spontaneous Vt

3. decreases the patient's spontaneous RR (if pt. is taking very shallow breaths, body will compensate by increasing RR. PSV will help decrease this)

4. decreases the patient's WOB by overcoming the resistance of the artificial airway, vent circuit and demand valves

5. allows patient control of RR, VT and Flow

PSV more advantages

1. set peak pressure

2. prevents respiratory muscle atrophy

3. facilitates weaning

4. improves patient comfort and reduces need for sedation

5. may be applied to any mode that allows spontaneous breathing (e.g. VC-SIMV, PC-SIMV)

PSV disadvantages

1. requires consistent spontaneous ventilation

2. patients in stand-alone mode should have back-up ventilation

3. Vt variable and dependent on lung characteristics and synchrony

5. fatigue and tachypnea if PS level is set too low

flow cycling - what is the only "mode" it can happen in

Pressure Support Ventilation

flow cycling in PSV

1. occurs when the ventilator detects a decreasing flow which represents the end of inspiration

2. the point is a percentage of peak flow measured during inspiration

3. no single flow-cycle percentage is right for all patients

4. example of a low parentage might be 17%
example of a high percentage might be 57%