Basics of mechanical ventilation : Basics of mechanical ventilation Presenter: Dr.Manjula.Sudhakar. Rao
Moderator: .Dr.P.N. Vishwanathan
PROF AND HOD Dept of anaesthesiology Introduction : Introduction Mechanical ventilation is a useful modality for patients who are unable to sustain the level of ventilation necessary to maintain the gas exchange functions-oxygenation and carbon dioxide elemination Indications: : Indications: Physiological changes like deterioration of lung parenchyma
Diseased states like chest trauma
Medical/surgical procedures like post operative recovery
Ventilatory failure or oxygenation failure due to
1. Increased airway resistance
2. Changes in lung compliance
4. V/Q mismatch
5. Intrapulmonary shunting
6. diffusion defect Key terms : Key terms Lung compliance: Is the change in volume per unit change in pressure
Static compliance=Correctedtidal volume
= corrected tidal volume
Peak inspiratory pressure-PEEP Slide 5: Plateau pressure- is the pressure needed to maintain lung inflation in the absence of air flow
PIP- Pressure used to deliver the tidal volume by overcoming non elastic (airways) and elastic (lung parenchyma) resistance Slide 6: Static compliance- is measured when there is no air flow.
Reflects the elastic properties of the lung and the chest wall
Dynamic compliance is measured when air flow is present
Reflects the airway resistance (non elastic resistance) and elastic properties of lung and chest wall Slide 7: Low lung compliance increases the work of breathing
Responsible for refractory hypoxemia
Low oxygen tension in blood that responds poorly to oxygen therapy
i.e. when patients PaO2 is 60mmHg or less with FiO2 is 50% or more Clinical conditions that decrease compliance : Clinical conditions that decrease compliance Slide 9: High compliance – exhalation is often incomplete due to lack of elastic recoil by the lungs.
Seen in conditions that increase patients FRC-
Obstructive lung defect
Airflow obstruction Dead space : Dead space Anatomic- conducting airways. Estimated to be about 1ml per pound of ideal body weight
Alveolar- normal lung volume that has become unable to take part in gas exchange because of reduction in pulmonary blood flow
Eg. Pulmonary embolism
Physiologic- Sum of anatomic and alveolar dead space volumes Slide 11: Minute ventilation (VE)
Total amount of gas exhaled/min.
VE = (RR) x (TV)
VE comprised of 2 factors
VA = alveolar ventilation
VD = dead space ventilation
VD/VT = 0.33
VE regulated by brain stem, responding to pH and PaCO2 V/Q Matching. Zone 1 demonstrates dead-space ventilation (ventilation without perfusion). Zone 2 demonstrates normal perfusion. Zone 3 demonstrates shunting (perfusion without ventilation). Slide 12: Origins of mechanical ventilation Negative-pressure ventilators (“iron lungs”)
Non-invasive ventilation first used in Boston Children’s Hospital in 1928
Used extensively during polio outbreaks in 1940s – 1950s
Invasive ventilation first used at Massachusetts General Hospital in 1955
Now the modern standard of mechanical ventilation The iron lung created negative pressure in abdomen as well as the chest, decreasing cardiac output. Iron lung polio ward at Rancho Los Amigos Hospital in 1953. Types of Systems : Types of Systems Negative Pressure Ventilator
“Iron lung” and chest cuirasse
Creates a trans airway pressure gradient by decreasing the alveolar pressures to a level below the airway opening pressure
Allows long-term ventilation without artificial airway
Iron lung- poor patient access and potential for a decreased cardiac output “TANK SHOCK” Types of Systems : Types of Systems Positive Pressure Ventilator
Uses pressures above atmospheric pressure to push air into lungs
Requires use of artificial airway Operating modes : Operating modes Spontaneous
Positive end expiratory pressure (PEEP)
Continuous positive airway pressure (CPAP)
Bilevel positive airway pressure (BiPAP)
Controlled mandatory ventilation (CMV)
Assist control (AC)
Intermittent mandatory ventilation (IMV) Slide 16: Synchronized intermittent mandatory ventilation (SIMV)
Mandatory minute ventilation (MMV)
Pressure support ventilation (PSV)
Adaptive support ventilation (ASV)
Proportional assist ventilation (PAV)
Volume assured pressure support (VAPS) Slide 17: Pressure regulated volume control (PRVC)
Volume ventilation plus (VV+)
Pressure control ventilation (PCV)
Airway pressure release ventilation
Inverse ratio ventilation (IRV)
Automatic tube compensation (ATC) Slide 18: Pressure cycled and volume cycled ventilation Pressure-cycled modes deliver a fixed pressure at variable volume
Volume-cycled modes deliver a fixed volume at variable pressure Volume-cycled modes
Intermittent Mandatory Ventilation (IMV)
Synchronous Intermittent Mandatory Ventilation (SIMV)
Pressure Support Ventilation (PSV)
Pressure Control Ventilation (PCV)
BiPAP Spontaneous ventilation : Spontaneous ventilation Airway
pressure Is not an actual mode on the ventilator since the rate and tidal volume are
determined by the patient
It provides inspiratory flow to the patient in a timely manner
Used with adjunctive modes like PEEP Positive End Expiratory Pressure (PEEP) : Positive End Expiratory Pressure (PEEP) Increases the end expiratory or baseline airway pressure to a value greater than atmospheric(0cmH2O) on ventilator manometer
Not a stand alone mode rather applied in conjunction with other modes
Intrapulmonary shunt and refractory hypoxemia
Decreased FRC and lung compliance
Useful in maintaining pulmonary function in non-cardiogenic pulmonary edema, especially ARDS Physiology of PEEP : Physiology of PEEP Reinflates collapsed alveoli and maintains alveolar inflation during exhalation
Decreases alveolar distending pressure
Increases FRC by alveolar recruitment
Increases V/Q, improves oxygenation, decreases work of breathing DANGERS : High intrathoracic pressures can cause decreased venous return and decreased cardiac output
May produce pulmonary barotrauma
May worsen air-trapping in obstructive pulmonary disease
Increases intracranial pressure
Alterations of renal functions and water metabolism DANGERS Continuous Positive Airway Pressure (CPAP) : Continuous Positive Airway Pressure (CPAP) PEEP without preset ventilator rate or volume
Physiologically similar to PEEP
May be applied with or without use of a ventilator or artificial airway
Requires patient to be breathing spontaneously
CPAP may be given via a facial mask , nasal mask or ET tube BiPAP : BiPAP An airway pressure strategy that applies independent positive airway pressure to both inspiration and expiration
It helps in preventing intubation of endstage COPD patients and in supporting patients with chronic ventilator failure
Initial settings of IPAP and EPAP are 8cm and 4cm of H2O respectively
Can be used as a Cpap device by setting IPAP and EPAP at the same level
IPAP may be increased in increments of 2cmH2O to enhance pressure boost to improve alveolar ventilation, normalise PaCO2 and reduce the work of breathing
EPAP should be increased by 2 cm H2O to increase functional residual capacity and oxygenation in patients with intrapulmonary shunting CONTROLLED MANDATORY VENTILATION(CMV) : CONTROLLED MANDATORY VENTILATION(CMV) CMV : CMV Delivers the preset tidal volume at a time triggered respiratory rate.
Ventilator controls both the tidal volume and respiratory rate of the patient.
Should only be used with a combination of sedatives, respiratory depressants and neuromuscular blockers. Indications : Indications “Fighting” or “bucking”the ventilator means the patient is severely distressed and vigorously struggling to breathe.
Patients rapid spontaneous efforts become asynchronous with the ventilators ability to provide an adequate inspiratory flow resulting in high pressure limit cycling,thus decreases ventilator delivered tidal volume Other Indications : Other Indications Tetanus or seizure activities
Complete rest for the patient for 24 hours
Crushed chest injury patients in whom paradoxical chest wall movement produced due to spontaneous inspiratory efforts COMPLICATIONS : COMPLICATIONS Disconnection or ventilator fails to operate is a primary hazard- in a sedated or apneic patient is the potential for apnea and hypoxia. Slide 30: Assist/Control Mode Assist Mode
Pt initiates all breaths, but ventilator cycles in at initiation to give a preset tidal volume
Pt controls rate but always receives a full machine breath
.Mandatory mechanical breath either triggered by patient spontaneous inspiratory efforts(assist)
Time triggered by a preset respiratory rate – (control)
POTENTIAL HAZARD-alveolar hyperventilation-higher pH and low PaCO2-respiratory alkalosis Ventilator delivers a fixed volume Slide 31: Intermittent mandatory ventilation IMV
Pt receives a set number of ventilator breaths
Different from Control: pt can initiate own (spontaneous) breaths
Different from Assist: spontaneous breaths are not supported by machine with fixed TV
Ventilator always delivers breath, even if pt exhaling
Breath stacking is the complication. SYNCHRONIZED INTERMITTENT MANDATORY VENTILATION(SIMV) : SYNCHRONIZED INTERMITTENT MANDATORY VENTILATION(SIMV) Ventilator delivers control breath (mandatory) to the patient at or near the time of spontaneous breath-TIME TRIGGERED
Mandatory breaths are synchronised with the patients spontaneous breathing effort to avoid breath stacking-PATIENT TRIGGERED Slide 33: If the patient is breathing spontaneously between the mandatory breaths and if patient begins to inspire just prior to ventilator time trigger, ventilator delivers mandatory breath as an assisted patient triggered breath.
Mandatory breath whether time or patient triggered is controlled by mechanical tidal volume settings. Synchronization window : Synchronization window Time interval just prior to time triggering in which ventilator is responsive to the patients spontaneous inspiratory efforts
Varies with ventilator,0.5 is representative ADVANTAGES : ADVANTAGES Maintains respiratory muscle strength/avoids muscle atrophy
Reduces ventilation and perfusion mismatch
Decreases mean airway pressure
Facilitates weaning Slide 36: Pressure Support Ventilation (PSV) Patient determines RR, VE, inspiratory time – a purely spontaneous mode Parameters
Triggered by pt’s own breath
Limited by pressure
Affects inspiration only
Complement volume-cycled modes (i.e., SIMV)
Does not augment TV but overcomes resistance created by ventilator tubing
Used alone for recovering intubated pts who are not quite ready for extubation
Augments inflation volumes during spontaneous breaths
BiPAP (CPAP plus PS) Slide 37: Pressure Control Ventilation (PCV) Ventilator determines inspiratory time – no patient participation Parameters
Triggered by time
Limited by pressure
Affects inspiration only
Requires frequent adjustments to maintain adequate VE
Pt with noncompliant lungs may require alterations in inspiratory times to achieve adequate TV Slide 38: Vent settings to improve <oxygenation> FIO2
Simplest maneuver to quickly increase PaO2
Long-term toxicity at >60%
Free radical damage
Inadequate oxygenation despite 100% FiO2 usually due to pulmonary shunting
Collapse – Atelectasis
Pus-filled alveoli – Pneumonia
Water/Protein – ARDS
Water – CHF
Blood - Hemorrhage PEEP and FiO2 are adjusted in tandem Slide 39: Vent settings to improve <ventilation> Respiratory rate
Max RR at 35 breaths/min
Efficiency of ventilation decreases with increasing RR
Decreased time for alveolar emptying
Goal of 10 ml/kg
Risk of volutrauma
Other means to decrease PaCO2
Reduce muscular activity/seizures
Minimizing exogenous carb load
Controlling hypermetabolic states
Preferable to dangerously high RR and TV, as long as pH > 7.15 RR and TV are adjusted to maintain VE and PaCO2 I:E ratio (IRV)
Increasing inspiration time will increase TV, but may lead to auto-PEEP
Elevated PIP suggests need for switch from volume-cycled to pressure-cycled mode
Maintained at <45cm H2O to minimize barotrauma
Pressure measured at the end of inspiratory phase
Maintained at <30-35cm H2O to minimize barotrauma Slide 40: Ventilator Graphics….. Purpose : Purpose Graphics are waveforms that reflect the patient-ventilator system and their interaction.
Purpose of monitoring graphics includes:
Allows user to interpret, evaluate, and troubleshoot the ventilator and the patient’s response to ventilator.
Monitors the patient’s disease status (C and Raw).
Assesses patient’s response to therapy.
Monitors ventilator function
Allows fine tuning of ventilator to decrease WOB, optimize ventilation, and maximize patient comfort. Measured Parameters…. : Measured Parameters…. Flow
Calculated Parameters …..
Volume (as an integration of flow)
Work of Breathing
Auto-PEEP Slide 43: A. Trigger …….
What causes the breath to begin?
B. Limit ……
What regulates gas flow during the breath?
C. Cycle …….
What causes the breath to end? Basics phase variables………….. Slide 44: The Pulmonary graphics display in two formats………
…………………….Loops ..!!! Most Commonly used Waveforms and Loops…… : Most Commonly used Waveforms and Loops…… Pressure vs. Time
Flow vs. Time
Volume vs. Time
Pressure – volume loop
Flow – volume loop Slide 46: Waveforms: plot pressure/volume/flow against time…time is the x axis
Loops: plot pressure/volume/flow against each other…there is no time component Types of waveforms seen : Types of waveforms seen Pressure waveforms
Exponential decay Types of Waveforms…… : Volume Modes Pressure Modes Types of Waveforms…… Pressure Flow Volume Time Pressure/Time waveform : Pressure/Time waveform In Volume modes, the shape will be an exponential rise or an accelerating ramp for mandatory breaths. In Pressure modes, the shape will be rectangular or square.
This means that pressure remains constant throughout the breath cycle. In Volume modes, adding an inspiratory pause may improve distribution of ventilation. Pressure/Time waveform : Pressure/Time waveform Air trapping (auto-PEEP)
Respiratory Mechanics (C/Raw)
Breath Type (Pressure vs. Volume)
Triggering Effort Can be used to assess: Pressure/Time waveform : Pressure/Time waveform A B 1 2 Inspiratory pause = MAP 1 = Peak Inspiratory Pressure (PIP)
2 = Plateau Pressure (Pplat)
A = Airway Resistance (Raw)
B = Alveolar Distending Pressure The area under the entire curve represents the mean airway pressure (MAP). Pressure/Time waveform : Pressure/Time waveform The baseline for the pressure waveform increases when PEEP is added.
There will be a negative deflection just before the waveform with patient triggered breaths. 5 15 No patient effort Patient effort PEEP +5 Pressure/Time wave form : Pressure/Time wave form Increased Airway Resistance Decreased Compliance PIP Pplat PIP Pplat A. B. A-An increase in airway resistance causes the PIP to increase, but Pplat pressure remains normal.
B-A decrease in lung compliance causes the entire waveform to increase in size.
The difference between PIP and Pplat remain normal. Pressure/Time waveform : Pressure/Time waveform Expiratory hold Set PEEP Auto-PEEP +5 +9 Total-PEEP +14 Air-Trapping (Auto-PEEP) While performing an expiratory hold maneuver, the waveform rises above the baseline.
The +9 of Aut0-PEEP represents 9 cm H2O pressure caused by air trapped in the lungs.
Fix by increasing the amount of “set PEEP” to offset the amount of auto-PEEP.
An acceptable amount of auto-PEEP should be < 5cm H2O Asynchrony : Asynchrony Flow Starvation The inspiratory portion of the pressure wave shows a scooping or “dip”, due to inadequate flow. Volume/Time waveform : Volume/Time waveform The Volume waveform will generally have a “mountain peak” appearance at the top. It may also have a plateau, or “flattened” area at the peak of the waveform. There will also be a plateau if an inspiratory pause set or inspiratory hold maneuver is applied to the breath. Volume/Time waveform : Volume/Time waveform Air trapping (auto-PEEP)
Asynchrony Can be used to assess: Volume/Time waveform : Volume/Time waveform Inspiratory Tidal Volume Exhaled volume returns
to baseline Volume/Time waveform : Volume/Time waveform Air-Trapping or Leak If the exhalation side of the waveform doesn’t return to baseline, it could be from air-trapping or there could be a leak (ETT, vent circuit, chest tube, etc.) Loss of volume Flow/Time waveform : Flow/Time waveform In Volume modes, the shape of the waveform will be square or rectangular.
This means that flow remains constant throughout the breath cycle. In Pressure modes,
(PC, PS, PRVC, VS) the shape of the waveform will have a decelerating ramp flow pattern. Some ventilators allow you to select the flow pattern that you want in Volume Control mode. Flow/Time waveform : Flow/Time waveform Air trapping (auto-PEEP)
Breath Type (Pressure vs. Volume)
Flow Waveform Shape
Triggering Effort Can be used to assess: Flow/Time waveform : Flow/Time waveform Volume Pressure Flow/Time waveform : Flow/Time waveform The decelerating flow pattern may be preferred over the constant flow pattern. The same tidal volume is delivered, but with a lower peak pressure. Flow/Time waveform : Flow/Time waveform Auto-Peep (air trapping) If expiratory flow doesn’t return to baseline before the next breath starts, there’s auto-PEEP (air trapping) present , e.g. emphysema. Start of next breath Expiratory flow doesn’t return to baseline Flow/Time Scalar : Flow/Time Scalar Bronchodilator Response To assess response to bronchodilator therapy, you should see an increase in peak expiratory flow rate.
The expiratory curve should return to baseline sooner. Peak Exp. Flow Improved Peak Exp. Flow Shorter
E-time Pre-Bronchodilator Post-Bronchodilator Pressure/Volume Loops : Pressure/Volume Loops Volume is plotted on the y-axis, Pressure on the x-axis.
Inspiratory curve is upward, Expiratory curve is downward.
Spontaneous breaths go clockwise and positive pressure breaths go counterclockwise.
The bottom of the loop will be at the set PEEP level. It will be at 0 if there’s no PEEP set.
If an imaginary line is drawn down the middle of the loop, the area to the right represents inspiratory resistance and the area to the left represents expiratory resistance. P-V loops…… : P-V loops…… Lung Overdistention
Triggering Effort Slide 68: inspiration expiration 15 30 5 The loop is almost square in PC/PS because of pressure
limiting (constant) , during the inspiratory part of the loop. P-V Loop……. Components Volume Pressure P-V slope A = Inspiratory Resistance/
Resistive WOB B = Exp. Resistance/
Elastic WOB Dynamic
Compliance Pressure mode…… PIP A B P-V Loop……. Components : P-V Loop……. Components Volume PIP VT Pressure A = Inspiratory Resistance/
Resistive WOB B = Exp. Resistance/
Elastic WOB Expiration Inspiration Dynamic
Compliance (Cdyn) The top part of the P/V loop represents Dynamic compliance (Cdyn).
Cdyn = Δvolume/Δpressure Volume mode A B Slide 70: Spontaneous Breath……… Inspiration Expiration 0 20 40 60 20 40 -60 0.2 0.4 0.6 Pressure cmH2O VT Clockwise CPAP Slide 71: Assisted Breath………… Inspiration Expiration 0 20 40 60 20 40 -60 0.2 LITERS 0.4 0.6 Paw cmH2O Assisted Breath VT Clockwise to Counterclockwise PEEP Slide 72: Controlled Breath……. Expiration 0 20 40 60 20 40 -60 0.2 LITERS 0.4 0.6 Paw cmH2O Inspiration VT Anticlockwise PEEP P-V loop and PEEP….. P-V Loops….in Airway Resistance : P-V Loops….in Airway Resistance As resistance increases, the loop will become wider.
An ↑ in expiratory resistance is more common.
↑ inspiratory resistance …….kinked ETT or patient biting. “hysteresis” exp. resistance insp. resistance Decreased Compliance………. : Decreased Compliance………. Volume Pressure ↓compliance… Loops moves down (angle becomes < 40)…….RDS (HMD)
….moves up (>45) …….. ↑ compliance……. Surfactant therapy Lung Compliance Changing in P-V Loop (pressure mode)…………. : Lung Compliance Changing in P-V Loop (pressure mode)…………. Volume Preset PIP VT levels Pressure RDS…lung 1.With surfactant
2. Emphysematous L Constant PIP……… variable VT Lung Compliance Changes and the P-V Loop…. (Volume mode) : Lung Compliance Changes and the P-V Loop…. (Volume mode) Volume PIP levels Preset VT Pressure ↑C C ↓C Constant VT………. Variable Pressure Air leak….. : Air leak….. The expiratory portion of the loop doesn’t return to baseline. This indicates a leak. Inspiration Expiration Insufficient flow…… : Insufficient flow…… Volume Pressure Normal Insufficient Flow Cusping Slide 79: Flow –Volume Loops…… Flow/Volume Loops : Flow/Volume Loops Flow is plotted on the y axis and volume on the x axis
Flow volume loops used for ventilator graphics are the same as ones used for Pulmonary Function Testing, (usually upside down).
Inspiration is above the horizontal line and expiration is below.
The shape of the inspiratory curve will match what’s set on the ventilator.
The shape of the exp flow curve represents passive exhalation…it’s long and more drawn out in patients with less recoil.
Can be used to determine the PIF, PEF, and Vt
Looks circular with spontaneous breaths Flow/Volume Loops : Flow/Volume Loops Air trapping
Water or Secretion accumulation
Asynchrony Can be used to assess: Flow-Volume Loop………. : Flow-Volume Loop………. Volume (ml) Inspiration Expiration Flow (L/min) PIFR PEFR FRC VT Pressure Mode F-V loops…. variations : F-V loops…. variations Air-leak………. : Air-leak………. Volume (ml) Inspiration Expiration Flow (L/min) PIFR PEFR FRC VT Air Leak Slide 85: Volume (ml) Inspiration Expiration Flow (L/min) PIFR PEFR VT Air Trapping……. Does not return
to baseline Airway Secretions ……….Water in the Circuit : Volume (ml) Inspiration Expiration Flow (L/min) PIFR PEFR FRC VT Airway Secretions ……….Water in the Circuit Slide 87: Volume (ml) Inspiration Expiration Flow (L/min) PIFR FRC VT ↓PEFR “Scooped out”
pattern Increased Airway Resistance…… Bronchodilator Response….. F-V loop : Bronchodilator Response….. F-V loop 2 1 1 2 3 3 V
LPS . VT Normal AFTER Bronchospasm Relief 2 1 1 2 3 3 V . Air Trapping (auto-PEEP) : Air Trapping (auto-PEEP) Causes:
Insufficient expiratory time
Early collapse of unstable alveoli/airways during exhalation
How to Identify it on the graphics
Pressure wave: while performing an expiratory hold, the waveform rises above baseline.
Flow wave: the expiratory flow doesn’t return to baseline before the next breath begins.
Volume wave: the expiratory portion doesn’t return to baseline.
Flow/Volume Loop: the loop doesn’t meet at the baseline
Pressure/Volume Loop: the loop doesn’t meet at the baseline
How to Fix:
Give a treatment, adjust I-time, increase flow, add PEEP. Airway Resistance Changes : Airway Resistance Changes Causes:
ETT problems (too small, kinked, obstructed, patient biting)
High flow rate
Damp or blocked expiratory valve/filter
Water in the HME
How to Identify it on the graphics
Pressure wave: PIP increases, but the plateau stays the same
Flow wave: it takes longer for the exp side to reach baseline/exp flow rate is reduced
Volume wave: it takes longer for the exp curve to reach the baseline
Pressure/Volume loop: the loop will be wider. Increase Insp. Resistance will cause it to bulge to the right. Exp resistance, bulges to the left.
Flow/Volume loop: decreased exp flow with a scoop in the exp curve
How to fix
Give a treatment, suction patient, drain water, change HME, change ETT, add a bite block, reduce PF rate, change exp filter. Compliance Changes : Compliance Changes Decreased compliance
How to Identify it on the graphics
Pressure wave: PIP and plateau both increase
Pressure/Volume loop: lays more horizontal Increased compliance
How to Identify it on the graphics
Pressure wave: PIP and plateau both decrease
Pressure/Volume loop: Stands more vertical (upright) Leaks : Leaks Causes
Expiratory leak: ETT cuff leak , chest tube leak, BP fistula, NG tube in trachea
Inspiratory leak: loose connections, ventilator malfunction, faulty flow sensor
How to ID it
Pressure wave: Decreased PIP
Volume wave: Expiratory side of wave doesn’t return to baseline
Flow wave: PEF decreased
Pressure/Volume loop: exp side doesn’t return to the baseline
Flow/Volume loop: exp side doesn’t return to baseline
How to fix it
Check possible causes listed above
Do a leak test and make sure all connections are tight Slide 93: Indications for extubation Clinical parameters
Resolution/Stabilization of disease process
Intact cough/gag reflex
Acceptable vent settings
FiO2< 50%, PEEP < 8, PaO2 > 75, pH > 7.25
Pressure Support Ventilation (PSV) Weaning
Spontaneous breathing trials No weaning parameter completely accurate when used alone Marino P, The ICU Book (2/e). 1998. Slide 94: Spontaneous Breathing Trials Settings
PEEP = 5, PS = 0 – 5, FiO2 < 40%
Breathe independently for 30 – 120 min
ABG obtained at end of SBT
Failed SBT Criteria
RR > 35 for >5 min
SaO2 <90% for >30 sec
HR > 140
Systolic BP > 180 or < 90mm Hg
Sustained increased work of breathing
pH < 7.32 SBTs do not guarantee that airway is stable or pt can self-clear secretions Sena et al, ACS Surgery: Principles and Practice (2005). Slide 95: Ventilator management algorithim Initial intubation
FiO2 = 50%
PEEP = 5 RR = 12 – 15
VT = 8 – 10 ml/kg SaO2 < 90% SaO2 > 90% SaO2 > 90%
Adjust RR to maintain PaCO2 = 40
Reduce FiO2 < 50% as tolerated
Reduce PEEP < 8 as tolerated
Assess criteria for SBT daily SaO2 < 90%
Increase FiO2 (keep SaO2>90%)
Increase PEEP to max 20
Identify possible acute lung injury
Identify respiratory failure causes Acute lung injury No injury Fail SBT Acute lung injury
Low TV (lung-protective) settings
Reduce TV to 6 ml/kg
Increase RR up to 35 to keep pH > 7.2, PaCO2 < 50
Adjust PEEP to keep FiO2 < 60% SaO2 < 90% SaO2 > 90% SaO2 < 90%
Dx/Tx associated conditions (PTX, hemothorax, hydrothorax)
Consider adjunct measures (prone positioning, HFOV, IRV) SaO2 > 90%
Continue lung-protective ventilation until:
PaO2/FiO2 > 300
Criteria met for SBT Persistently fail SBT
Resume daily SBTs with CPAP or tracheostomy collar Pass SBT Airway stable Extubate Intubated > 2 wks Consider PSV wean (gradual reduction of pressure support)
Consider gradual increases in SBT duration until endurance improves Prolonged ventilator dependence Pass SBT Pass SBT Airway stable Modified from Sena et al, ACS Surgery: Principles and Practice (2005). REFERENCES: : REFERENCES: David W.Chang,clinical application of mechanical ventilation;third edition;Thomson Delmar learning
Paul L.Marino,The ICU Book;second and third edition;Wolters Kluver health/Lippincott Williams and Wilkins
Internet references Slide 97: Thank you Thank you