basics & principles of mechanical ventilation g.k.kumar
Post on 02-Jan-2016
261 Views
Preview:
TRANSCRIPT
Basics & principles of
mechanical ventilationg.k.kumar
Basics & principles of ventilation
-What is ventilator
-How ventilators work
-How to use
?
Ventilator:
The Machine delivers O2 & removes Co2 with out harming the patient.
The Ventilator should have capacity of delivering a consistent tidal volume under all adverse conditions of lung disease.
Mechanical Ventilation:
The process / method by applying
(intermittent) positive airway pressure
& supplementation of Inspired O2 to
achieve desirable oxygenation.
GOALS of Mechanical Ventilation:
Good ventilation (known by pa Co2) Oxygenation (by pa O2). Alveolar recruitment by peep Lowest O2 supplement. Synchrony between patient & Ventilation. & Safe No Negative hemodynamic effect
No Barotraumas No auto PEEP
Classification of Mechanical ventilation:
Positive / Negative pressure ventilation.
Partial / full ventilation.
Invasive / Non invasive ventilation.
Components of ventilator
1. Power source-electrical/pneumatic/both
2. Control systems-circuits, control panel
3. Display systems
compressor
compressor
Insp. limb
Exp.limbPt
blenderoxy
Central unit
V
V
P Fio2T
Hum&neb
PHASES & VARIABLES INITIATION OF INSPIRATION-TRIGGER
INSPIRATION-LIMIT
MAINTENANCE OF INSPIRATION-CONTROL
CHANGING TO EXPIRATION-CYCLE
Triggering variable:
Triggering is a method of starting the inspiration
Types: Pressure Triggering
Flow Triggering - No lag time
Time Triggering -Less effort
Control Variable:
Setting that maintained thro ‘out inspiration
Type : Volume control.
Pressure control.
PCV VCV Vt. Variable set PIP SET & lesser variable & more Plateau pressure Set Variable Inspiratory flow decelerating type fixed flow
type sinusoidal/square Inspiratory time set set Respiratory rate Set Set Barotrauma Less More
Leak compensation +for minor leak nil
Patients acceptance good -
Limit Variable:
Setting that can't be exceeded during inspiration
Type : Pressure limit- [psv]
volume limit
Flow limit
Cycle variable:
Method of termination of inspiration, I.e. changing over from inspiration to expiration.
Types: Volume cycle Pressure cycle Time cycle flow cycle.
Vt PA range
compliance
ClCcw
PAi
PAe
Raw
Compliance-resistance-volume
C=▲V /▲P R=[PIP-Pp] / F
Normal resistance
Un intubated patient ; 0.6 - 2.4 cm H20 / L / Sec, . at 0.5L /sec
Intubated patient; 6cm H20 / L / Sec
Ventilatory controls-inter relation
MV
fVt
T
Ti
I:E
Te
Ventilator Modes Combination of breath type and phase variable.
Conventional modes Recent modes Newer modes
CMV MMV VAPS, PAug
A/C MV APRV VS, PRVC
IMV & SIMV BIPAP AUTOFLOW
CPAP & PEEP IRV AUTOMODE
VCV DLV PAV,PPS
PSV HFJV ASV
Controlled mechanical ventilation:
-CMV All breaths are delivered by ventilator.
No Patient participation.
Set Vt. Delivered at set RR
Requires sedation & neuromuscular blockade.
Time initiated
Volume limited
Volume cycling
CMV Indications Patient with no efforts / complete respiratory failure. When negative inspiratory effort contra indicated. eg.flail chest. During anesthesia. Disadvantages
Patient participation not allowed. Heavy sedation relaxant – need Long term CMV Respiratory muscle
weakness. Varying PIP according to lung compliance &
patient efforts.
Assist / Control Mechanical ventilation:
Patient can trigger ventilation at a rate more than set RR
All breaths are delivered at set volume , set time & set pressure
Triggering pressure / flow (spontaneous)
Time (Mandatory)
Limiting Volume
Cycling Volume Patient can vary RR only but not vt.
Indications: Patient with normal drive but with respiratory weakness
Recovering patient. To preserve patient efforts
Weaning.
Disadvantages Rapid triggering Hyperventilation
Hypotension
Flow rare should be adjusted according to the need.If RR < RR CMV mode.
Assist / Control Mechanical Ventilation
IMV / SIMV
The patient receives the Mandatory set Vt at set RR. The set Mandatory breaths are synchronized with patient
efforts. Between the mandatory breaths the patient can breath
spontaneously Spontaneous breath vt depends on Patients respiratory effort PS Triggering - Pressure Limiting - Volume Cycling - Time
IMV / SIMV
Advantages: The mandatory breaths are synchronized with
patient’s Spontaneous efforts. Hyperventilation is less More active participation of patient
Disadvantages: More WOB
A/CMV SIMV
Patient decides only RR < -- > patient effort decides RR &vt.
Less WOB as only < -- >more WOB as Initiation by patient patient has to . operate demand
. flow system
Possibility of hyper ventilation < -- > No
CPAP:
A mode is which positive pressure is applied tho’ out the respiratory cycle using during spontaneous ventilation.
(Pr applied in mechanical ventilation :PEEP) No Ventilatory assistance Positive Pressure causes: Prevention of alveolar collapse & alveolar recruitment
Î FRC & Atelecasis
FlO2 requirement
CPAP PEEPPr applied and base line Pr. Applied with
Pr elevated when ventilatory some ventilatory Assistance is nil. Assistance present.
PEEP
Applied when Fio2 requirement is 50% - 60%.
Best Peep: PEEP titrated to achieve optimal respiratory system compliance.
Optimal Peep :Titration of PEEP until Qs /Qt is < 15 %
Volume Control Ventilation:
Vt. Delivery is constant according to pressure regardless of changes in airway resistance or respiratory system compliance.
VCV is given when constant MV is needed (eg, : patient with Î ICT)
Pressure control ventilation: The pressure applied to the airways is constant
regardless of airway resistance and compliance. Constant pressure is delivered throughout inspiration at
set RR Time initiated pressure limiting time cycling. Vt may vary according to patient lung conditions. PCV avoids over distention in patient with ALI, because
PIP can be set.
Settings Preset pressure is equal to half of present PIP. PEEP half of present PEEP (if > 8cm H2 O) I: E is 1:2
PCV VCV Vt. Variable set PIP SET & lesser variable & more Plateau pressure Set Variable Inspiratory flow decelerating type fixed flow
type sinusoidal/square Inspiratory time set set Respiratory rate Set Set Barotrauma Less More
Leak compensation +for minor leak nil
Patients acceptance good -
Pressure – Support Ventilation (Psv)
Patients spontaneous activity is assisted by delivery of a preset amount of inspiratory positive pressure.
Patient triggers set pressure is maintained throughout inspiration.
Pressure initiated. Pressure limiting . Flow Cycling As flow reaches 25% of peak inspiratory flow /5
litres / min
Pressure – Support Ventilation (Psv)
Low PSV – to overcome the patients WOB associated with ETT and circuits.
PSV max – to achieve Vt of 10 -12 ml / Kg - may require upto 40 -50 cm H2O Can be used alone as full ventilatory support or with
SIMV. Can be used as non invasive ventilatory support up to
20cm H2O2 for – transient Ventilatory support ( Narcotic overdose, asthma, acute exacerbation of COPD).
Mandatory Minute Ventilation (MMV):
Preset MV is selected. The Ventilator calculates the patients spontaneous MV. It patients spontaneous MV < set MV, ventilator assists to achieve
set MV
Ventilatory assisstance may be
- Volume controlled SIMV breaths Î RR /Vt
- Î PSV
Mandatory Minute Ventilation (MMV):ADVANTAGES:
•MV guaranteed
•Useful as weaning mode
DISADVANTAGES:
• RR may cause dead space ventilation even with acceptable MV.
•Respiratory muscle fatigue may develop (so high RR alarm should be activated.
Mandatory Minute Ventilation (MMV):
INDICATIONS:
•During weaning period
•To aspiratory flow and WOB
•To overcome ETT/circuit resistance
BILEVEL POSITIVE AIRWAY PRESSURE VENTILATION(BIPAP)
•A pressure controlled ventilation
•Allows unrestricted spontaneous breathing at any point of ventilatory cycle
•Time cycled changes of pressure application.
•Independent positive airway pressure to inspiration & expiration
•Inspiratory set pressure is called IAP/T high& Expiratory set pressure is called EAP/T low
•Usual IAP is 8 cm H2O & EAP is 3 cm H2O
•Trigger:flow, Limit:pressure; Cycle:time
BILEVEL POSITIVE AIRWAY PRESSURE VENTILATION(BIPAP)
•IAP causes better ventilation Paco2
•EAP causes better oxygenation Pao2
•Types
--CPAP+PS
--Two alternating CPAP level
--APRV
BILEVEL POSITIVE AIRWAY PRESSURE VENTILATION(BIPAP)
ADVANTAGES:
•Non invasive ventilation
•Useful in—end stage COPD
---restricted chest wall diseases
---neuromuscular diseases
---nocturnal hypo ventilation
•A weaning mode.
AIRWAY PRESSURE RELEASE VENTILATION(APRV)
A CPAP circuit with release valve at expiratory limb –driven by time device
APRV is a CPAP system causing . alveolar ventilation by briefly interrupting CPAP.
APRV…….,
Release valve opens for 1-2sec.
Pr drops to lower level-low CPAP(0to-2cmH2O)
Lung volume less than FRC in expiration
alveolar ventilation & CO2 elimination
Reapplication of CPAP by closing valve- Higher CPAP(10to 12 cm H2O)
FRC & oxygenation.
APRV…….,
ADVANTAGES:
•Lesser PIP ,so less hemo dynamic changes.
•To alveolar ventilation in ALI of mild to moderate.
•A weaning mode.
INVERSE RATIO VENTILATION(IRV)
•I:E >1
•PC-IRV / VC-IRV
• Ti with set pr opening of stiff alveoli units improved oxygenation
• Te not allowing alveoli to collapse
development of intrinsic PEEP
reduction of shunting
IRV……,Improve oxygenation by
•Reducing intra pulmonary shunting
•Improvement of V/Q matching
•Decreased dead space ventilation
•Increased MAP & intrinsic PEEP
Useful when high FiO2 & high PEEP to be avoided
NEWER MODES
1.Dual modes: VAPS, Paug, - VS, PRVC, Autoflow, VPC
2.Switching modes: Automode
3.Proportional modes: PAV,PPS.
4.Adaptive modes: ASV
DUAL MODES Combination of 2modes of ventilation(PCV&VCV) to
deliver guaranteed Vt/MV
Volume guaranteed pr targeted ventilation
Mode changes occur
with in a breath-VAPS,Paug
over several breaths-VS,PRVC,Auto flow,VPC
DUAL MODES - CHANGES WITH IN BREATH•VAPS:volume assured pr support-T bird,bird8400st
•Paug :pr augmented ventilation-bear 1000
•Vt guaranteed variable pr limited modes
•During inspiration,the ventilator monitors Vt
if desired Vt delivered before flow drops---PSV
if desired Vt not delivered before flow drops—
flow continued at set pr support level till adequate
Vt delivered.
DUAL MODES - CHANGES WITH IN BREATH
•Trigger – patient patient
•Limit -- pressure variable pr
•Cycle -- flow volume
PSV Paug
VAPS
DUAL MODES - CHANGES OVER SEVERAL BREATHS
•PRVC:Pr regulated VC-siemen300
VS:volume support:servo 300
Auto flow;DragerE4
•VS-volume assured PSV
•PRVC-volume assured PCV
•Vt measured over several breaths&adequate MV achieved by changing PS/PC mode for remaining breaths.
DUAL MODES - CHANGES OVER SEVERAL BREATHS
AUTOFLOW:
•Autoflow alters the function of inspiratory and expiratory valves
Allowing patient to receive inspiratory flow demand
•Auto flow provides better ventilatory tolerance
•A weaning mode
Switching modes•Ventilator can switch modes according to monitored information
•Automode:servo300
Switching between control /support mode depending on patient’s respiratory pattern
•Monitoring of patient’s respiration over fixed time period – if 2consecutive effort + PSV . -- if no efforts - PCV
Proportional modes•PAV:proportional assist ventilation-PB840
PPS: proportional PS-Evita-E4
•Proportional modes are assisting spontaneous ventilation
•PPV:a support mode in which pr, flow,volume are set proportional to patient’s inspiratory efforts
Proportional modes
•The more effort pt exerts-the more support the machine provides
•PAV allows patients to comfortably reach whatever the ventilatory pattern that suit their need.
Adaptive modes•ASV-Adaptive support ventilation
•Uses pr targeted breaths to assure a target MV with decreased WOB
•ASV adapts to the changing capabilities of patient’s lung conditions.
•More efforts the patient does less - support the machine provides.
Adaptive modes
•ASV calculate the over all MV combination of volume guaranteed PSV(VS) & volume guaranteed PCV(PAVC)
•ASV can ventilate the patient from acute stage to a weaning stage.
Weaning
Wearing off primary pathology Elimination of effects of sedation & relaxants Absence of sepsis No metabolic / electrolyte abnormality Involvement of patient Nutritionally stable Good & stable CVS
top related