Mv basics lecture
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Transcript of Mv basics lecture
Indications for Mechanical Ventilation
• Airway Compromise/ Respiratory Failure Hypoxemic Respiratory Failure (Type I)
• PaO2 < 60 mmHg in an otherwise healthy individual• SaO2 < 90 %
Hypercapnic Respiratory Failure (Type 2)• PaCO2 > 50 mmHg in an otherwise healthy individual• AKA “Ventilatory Failure”• Caused by increased WOB, ↓ventilatory drive, or muscle fatigue
• Airway Protection/ Prophylactic Ventilatory Support Clinical conditions in which there is a high risk of future respiratory failure
• Examples: Brain injury, heart muscle injury, major surgery, prolonged shock, smoke injury
• Ventilatory support is instituted to:– Decrease the Work of Breathing (WOB)– Minimize O2 consumption and hypoxemia– Reduce cardiopulmonary stress– Control airway with sedation
Criteria
• Clinical Assessment (most important) Clinical deterioration Tachypnea: RR >35; Bradypnea, Apnea Co-morbid conditions
• ABG’s Hypoxia: pO2<60mm Hg Hypercarbia: pCO2 > 50mm Hg
* ABGs and Physiological parameters cannot distinguish between acute and chronic respiratory Failure* What may be “normal” in a COPD patient (RR > 30/min, PCO2 > 60 mm Hg) may be indications for intubation in a young, otherwise healthy adult
V/Q Matching. Zone 1 demonstrates dead-space ventilation (ventilation without perfusion). Zone 2 demonstrates normal perfusion. Zone 3 demonstrates shunting (perfusion without ventilation).
Principles (1): Ventilation• The goal of ventilation is to facilitate CO2 release and maintain
normal PaCO2
• 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
• Ventilation in context of ICU• Increased CO2 production
• fever, sepsis, injury, overfeeding• Increased VD
• atelectasis, lung injury, ARDS, pulmonary embolism• Adjustments: RR and TV
Principles (2): Oxygenation
• The primary goal of oxygenation is to maximize O2 delivery to blood (PaO2)
• Alveolar-arterial O2 gradient (PAO2 – PaO2)• Equilibrium between oxygen in blood and oxygen in alveoli• A-a gradient measures efficiency of oxygenation• PaO2 partially depends on ventilation but more on V/Q
matching
• Oxygenation in context of ICU• V/Q mismatching
• Patient position (supine)• Airway pressure, pulmonary parenchymal disease, small-
airway disease• Adjustments: FiO2 and PEEP
Terminologies
• A/C: Assist-Control• SIMV: Synchronized Intermittent Mandatory
Ventilation• Bi-level/Biphasic: Non-inversed Pressure
Ventilation with Pressure Support (consists of 2 levels of pressure)
• PRVC: Pressure Regulated Volume Control • PEEP: Positive End Expiratory Pressure• CPAP: Continuous Positive Airway Pressure• PSV: Pressure Support Ventilation• NIPPV: Non-Invasive Positive Pressure Ventilation
Pressure Ventilation vs. Volume Ventilation
• Pressure-cycled modes deliver a fixed pressure at variable volume (neonates)
• Volume-cycled modes deliver a fixed volume at variable pressure (adults)
• Pressure-cycled modes• Pressure Support Ventilation (PSV)• Pressure Control Ventilation (PCV)• CPAP• BiPAP
• Volume-cycled modes• Control• Assist• Assist/Control• Intermittent Mandatory Ventilation (IMV)• Synchronous Intermittent Mandatory Ventilation (SIMV)
Pressures in Positive Pressure Ventilation
• Baseline Pressure• Peak Pressure• Plateau Pressure• Pressure at End of Exhalation
Pressures in Positive Pressure Ventilation
• Baseline Pressure– Pressures are read from a zero baseline value– At baseline pressure (end of exhalation), the
volume of air remaining in the lungs is the FRC.
Pressures in Positive Pressure Ventilation
• Baseline Pressure– Continuous Positive Airway Pressure (CPAP)
Pressures in Positive Pressure Ventilation
• Baseline Pressure– Positive End-Expiratory Pressure (PEEP)
• Prevents patients from exhaling to zero (atmospheric pressure)
• Increases volume of gas left in the lungs at end of normal exhalation – increases FRC
Pressures in Positive Pressure Ventilation
• Peak Pressure (PIP)– The highest pressure recorded at the end of inspiration (PPeak,
PIP)– It is the sum of two pressures
• Pressure required to force the gas through the resistance of the airways and to fill alveoli
Pressures in Positive Pressure Ventilation
• Plateau Pressure– At the end of inspiration, before exhalation starts, the
volume of air in the lungs is the VT plus the FRC. The pressure measured at this point with no flow of air is plateau pressure
– Measured after a breath has been delivered and before exhalation
• Ventilator operator has to perform an “inflation hold” – Like breath holding at the end of inspiration
– Reflects the effect of elastic recoil on the gas volume inside the alveoli and any pressure exerted by the volume in the ventilator circuit that is acted upon by the recoil of the plastic circuit
Pressures in Positive Pressure Ventilation
• Pressure at End of Expiration– Pressure falls back to baseline during expiration– Auto-PEEP
• Air trapped in the lungs during mechanical ventilation when not enough time is allowed for exhalation
• When PEEPi occurs, the lung volume at end expiration is greater then the FRC
• Need to monitor pressure at end of exhalation
Pressures in Positive Pressure Ventilation
• Auto-PEEP– Why does hyperinflation occur?
• Airflow limitation because of dynamic collapse• No time to expire all the lung volume (high RR or Vt)• Expiratory muscle activity• Lesions that increase expiratory resistance
• Measured in a relaxed pt with an end-expiratory hold maneuver on a mechanical ventilator immediately before the onset of the next breath
• Adverse effects:– Predisposes to barotrauma– Predisposes hemodynamic compromises– Diminishes the efficiency of the force generated by respiratory
muscles– Augments the work of breathing– Augments the effort to trigger the ventilator
Modes of Ventilation
• Mode– Description of a breath type and the timing of
breath delivery• Basically there are three breath delivery techniques
used with invasive positive pressure ventilation– CMV – Controlled ventilation– IMV – Intermittent ventilation– Spontaneous modes
Modes of Ventilation
• CMV– All breaths are mandatory and can be volume
or pressure targeted• Controlled Ventilation – when mandatory breaths are
time triggered• Assist/Control Ventilation – when mandatory breaths
are either time triggered or patient triggered
Modes of Ventilation
• CMV– when mandatory breaths are time triggered
• ventilator determines the start time (time triggered) and/or the volume or pressure target
• Adequate alarms must be set to safeguard the patient– E.g., disconnection
• Sensitivity should be set so that when the patient begins to respond, they can receive gas flow from the patient
Modes of Ventilation
• CMV– Appropriate when a patient can make no
effort to breathe or when ventilation must be completely controlled• Drugs• Cerebral malfunctions• Spinal cord injury• Phrenic nerve injury• Motor nerve paralysis
Modes of Ventilation
• CMV– In other types of patients, controlled
ventilation is difficult to use unless the patient is sedated or paralyzed with medications• Seizure activity• Tetanic contractions• Inverses I:E ratio ventilation• Patient is fighting (bucking) the ventilator• Crushed chest injury – stabilizes the chest• Complete rest for the patient
Modes of Ventilation
• Assist/Control Ventilation– A time or patient triggered CMV mode in which the
operator sets a minimum rate, sensitivity level, type of breath (volume or pressure)
– 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
Modes of Ventilation
• Assist/Control Ventilation– Indications
• Patients requiring full ventilatory support• Patients with stable respiratory drive• The INITIAL mode usually set upon advent of mechanical
ventilation
Modes of Ventilation
• Assist/Control Ventilation– Advantages
• Decreases the work of breathing (WOB)• Allows patients to regulate respiratory rate• Helps maintain a normal PaCO2• Useful in patients with neuromuscular weakness or CNS disturbances
– Complications• Tachypnea may result in significant hypocapnia and respiratory
alkalosis• Improper setting of sensitivity to trigger the ventilator may result in
“fighting the ventilator” when the sensitivity is set too low• Increased sensitivity may result in hyperventilation; sensitivity is
generally set so that an inspiratory effort of 2 cm H20 / 2 Liters will trigger the ventilation
• Since there is almost no work involved by the respiratory muscles, muscle tone is not well-maintained (data have shown that muscle atrophy starts within 6 hours of AC mode)
Selection of Settings for A/C Mode
• Tidal Volume (VT) : – 8-10 ml/kg of ideal body weight– 6 ml/kg for ALI/ARDS
• Rate (number of tidal breaths delivered/minute):– backup rate is usually set 2 to 4 below the spontaneous rate and then the
effect on the patient of decreasing rate is noted– This can be adjusted depending on the desired PaCO2 or pH ( increased rate
= decreased PaCO2 and increased pH)
• Oxygen Concentration (Fi02): – the initial FiO2 should be 100% unless it is evident that a lower FIO2 will
provide adequate oxygenation
• Inspiratory Flow Rate: – This is the rate air is delivered to the patient to achieve the Tidal Volume set.– The initial flow rate is typically set at 40 to 60 L/minute. – This rate typically needs to be higher in patients with asthma and COPD – An inspiratory flow rate setting LOWER than the patient demand will increase
the work of breathing and is a common cause of patient-ventilator discordance
Selection of Settings for A/C Mode
• Inspiratory Flow Pattern:– This is how flow is distributed throughout the
respiratory cycle– The wave forms usually available are:
1. SINE WAVE - the maximum flow is at mid inspiration and resembles a normal spontaneous tidal breathing
2. SQUARE WAVE - this provides a maximum peak flow throughout the inspiratory period
3. DECELERATING WAVE – the flow is maximal at the start and diminishes as inspiration ends
• PEEP:– “Physiologic PEEP” of about 5 cm H20 should be added
regardless of FiO2 to prevent the alveolar injury due to the shearing effect of opening and closing of the alveoli
Selection of Settings for A/C Mode
• Sensitivity:– Ranges anywhere from –5 to –0.5 cm H20 (pressure
sensitivity) or 1- to 5 liters (flow sensitivity)– The more sensitive (e.g. 0.5 cm or 1 L) , the easier
for patient to trigger the ventilator which may lead to hyperventilation
– The less sensitive (e.g. 5 cm or 5 L), the harder for the patient to trigger the ventilator which can lead to increase of work of breathing and thus can cause patient-ventilator desynchrony
– The usual triggering pressure to start with is –2.0 cm or 2 L
Modes of Ventilation
• CMV– Volume Controlled
– CMV• Time or patient
triggered, volume targeted, volume cycled ventilation
• Graphic (VC-CMV)– Time-triggered,
constant flow, volume-targeted ventilation
Modes of Ventilation
• CMV– Volume Controlled
– CMV• Time or patient
triggered, volume targeted, volume cycled ventilation
• Graphic (VC-CMV)– Time-triggered,
descending-flow, volume-targeted ventilation
Modes of Ventilation
• CMV– Pressure Controlled – CMV
• PC – CMV (AKA – Pressure control ventilation - PCV)
• Time or patient triggered, pressure targeted (limited), time cycled ventilation
• The operator sets the length of inspiration (Ti), the pressure level, and the backup rate of ventilation
• VT is based on the compliance and resistance of the patient’s lungs, patient effort, and the set pressure
Modes of Ventilation
• CMV– Pressure Controlled – CMV
• Airway pressure is limited, which may help guard against barotrauma or volume-associated lung injury– Maximum inspiratory pressure set at 30 – 35 cm H2O– Especially helpful in patients with ALI and ARDS
• Allows application of extended inspiratory time, which may benefit patients with severe oxygenation problems
• Usually reserved for patient who have poor results with a conventional ventilation strategy of volume ventilation
Modes of Ventilation
• CMV– Pressure Controlled – CMV
• Occasionally, Ti is set longer than TE during PC-CMV; known as Pressure Control Inverse Ratio Ventilation– Longer Ti provides better oxygenation to some
patients by increasing mean airway pressure– Requires sedation, and in some cases paralysis
Modes of Ventilation
• Intermittent Mandatory Ventilation – IMV– Periodic volume or pressure targeted breaths occur at
set interval (time triggering)– Between mandatory breaths, the patient breathes
spontaneously at any desired baseline pressure without receiving a mandatory breath• Patient can breathe either from a continuous flow or gas or
from a demand valve
Modes of Ventilation
• Intermittent Mandatory Ventilation – IMV– Indications
• Facilitate transition from full ventilatory support to partial support
– Advantages• Maintains respiratory muscle strength by avoiding muscle
atrophy• Decreases mean airway pressure• Facilitates ventilator discontinuation – “weaning”
– Complications• When used for weaning, may be done too quickly and cause
muscle fatigue• Mechanical rate and spontaneous rate may asynchronous
causing “stacking”– May cause barotrauma or volutrauma
Modes of Ventilation
• Synchronized IMV– Operates in the same way as IMV except that
mandatory breaths are normally patient triggered rather than time triggered (operator set the volume or pressure target)
– As in IMV, the patient can breathe spontaneously through the ventilator circuit between mandatory breaths
Modes of Ventilation
• Synchronized IMV– At a predetermined interval (respiratory rate), which is
set by the operator, the ventilator waits for the patient’s next inspiratory effort
– When the ventilator senses the effort, the ventilator assists the patient by synchronously delivering a mandatory breath
– If the patient fails to initiate ventilation within a predetermined interval, the ventilator provides a mandatory breath at the end of the time period
Modes of Ventilation
• Synchronized IMV– Indications
• Facilitate transition from full ventilatory support to partial support
– Advantages• Maintains respiratory muscle strength by avoiding muscle atrophy• Decreases mean airway pressure• Facilitates ventilator discontinuation – “weaning”
– Complications/Disadvantages• When used for weaning, may be done too quickly and cause
muscle fatigue• With increased WOB resulting in increased oxygen consumption
which is deleterious in patients with myocardial insufficiency/hemodynamic instability
• NOT useful in patients with depressed respiratory drive or impaired neurologic status
Selection of Settings for SIMV Mode
• Rate : – The initial rate set should be close to the
patient’s rate and then the rate decreased noting the effect on patient acceptance.
• Tidal Volume (VT), FIO2, Inspiratory flow rate, Inspiratory flow pattern (Wave form), +/- PEEP are the same as that of A/C.
Modes of Ventilation
• Spontaneous Modes– Three basic means of providing support for continuous
spontaneous breathing during mechanical ventilation• Spontaneous breathing• CPAP• PSV – Pressure Support Ventilation
Modes of Ventilation
• Spontaneous Breathing– Patients can breathe spontaneously through a
ventilator circuit; – sometimes called T-Piece Method because it
mimics having the patient ET tube connected to a Briggs adapter (T-piece)
– Advantage• Ventilator can monitor the patient’s breathing and
activate an alarm if something undesirable occurs– Disadvantage
• May increase patient’s WOB with older ventilators
Modes of Ventilation
• Spontaneous Modes– CPAP
• Ventilators can provide CPAP for spontaneously breathing patients– 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
• Advantages– Ventilator can monitor the patient’s breathing and activate an alarm if
something undesirable occurs– Serves to keep alveoli from collapsing, resulting in better oxygenation
and less WOB.
• Pre-set pressure is present in the circuit and lungs throughout both the inspiratory and expiratory phases of the breath.
• Commonly used as a mode to evaluate the patients readiness for extubation.
Modes of Ventilation
• PEEP (Positive End Expiratory Pressure)– “According to its purest definition, the term PEEP is defined as positive
pressure at the end of exhalation during either spontaneous breathing or mechanical ventilation. However, use of the term commonly implies that the patient is also receiving mandatory breaths from a ventilator.” (Pilbeam)
– PEEP becomes the baseline variable during mechanical ventilation
– Helps prevent early airway closure and alveolar collapse and the end of expiration by increasing (and normalizing) the functional residual capacity (FRC) of the lungs
– Facilitates better oxygenation– NOTE: PEEP is intended to improve oxygenation, not to provide
ventilation, which is the movement of air into the lungs followed by exhalation
Modes of Ventilation
• Pressure Support Ventilation – PSV– Patient triggered, pressure targeted, flow
cycled mode of ventilation– Requires a patient with a consistent
spontaneous respiratory pattern– The ventilator provides a constant pressure
during inspiration once it senses that the patient has made an inspiratory effort
Modes of Ventilation
• PSV– Indications
• Spontaneously breathing patients who require additional ventilatory support to help overcome
• WOB, CL, Raw• Respiratory muscle weakness• Weaning (either by itself or in combination with SIMV)
Modes of Ventilation
• PSV– Advantages
• Full to partial ventilatory support• Augments the patients spontaneous VT
• Decreases the patient’s spontaneous respiratory rate• Decreases patient WOB by overcoming the resistance of the
artificial airway, vent circuit and demand valves• Allows patient control of TI, VI, f and VT
• Set peak pressure• Prevents respiratory muscle atrophy• Facilitates weaning• Improves patient comfort and reduces need for sedation• May be applied in any mode that allows spontaneous
breathing, e.g., VC-SIMV, PC-SIMV
Modes of Ventilation
• PSV– Disadvantages
• Requires consistent spontaneous ventilation• Patients in stand-alone mode should have back-
up ventilation• VT variable and dependant on lung
characteristics and synchrony• Low exhaled VE • Fatigue and tachypnea if PS level is set too low
Modes of Ventilation
• Spontaneous Modes– Flow Cycling During PSV
• Flow cycling occurs when the ventilator detects a decreasing flow, which represents the end of inspiration
• This point is a percentage of peak flow measured during inspiration– PB 7200 – 5 L/min– Bear 1000 – 25% of peak flow– Servo 300 – 5% of peak flow
• No single flow-cycle percent is right for all patients
Modes of Ventilation
• Spontaneous Modes– Flow Cycling During
PSV• Effect of changes in
termination flow
• A: Low percentage (17%)
• B: High percentage (57%)
• Newer ventilators have an adjustable flow cycle criterion, which can range from 1% - 80%, depending on the ventilator
Modes of Ventilation
• Spontaneous Modes– PSV during SIMV
• Spontaneous breaths during SIMV can be supported with PSV (reduces the WOB)
PCV – SIMV with PSV
Modes of Ventilation
• Spontaneous Modes– PSV during SIMV
• Spontaneous breaths during SIMV can be supported with PSV
VC – SIMV with PSV
Modes of Ventilation
• PSV– NOTE: During pressure support ventilation (PSV), inspiration ends if
the inspiratory time (TI) exceeds a certain value.
• This most often occurs with a leak in the circuit. For example, a deflated cuff causes a large leak. The flow through the circuit might never drop to the flow cycle criterion required by the ventilator.
• Therefore, inspiratory flow, if not stopped would continue indefinitely.
• For this reason, all ventilators that provide pressure support also have a maximum inspiratory time.
Modes of Ventilation
• PSV– Setting the Level of Pressure Support
• Goal: To provide ventilatory support– Spontaneous tidal volume is 10 – 12 mL/Kg of ideal
body weight– Maintain spontaneous respiratory rate <25/min
• Goal: To overcome system resistance (ET Tube, circuit, etc.) in the spontaneous or IMV/SIMV mode– Set pressure at (PIP – Pplateau) achieved in a volume
breath or at 5 – 10 cm H2O
Selection of Settings for PSV
• Inspiratory Pressure: – start with a pressure which gives a desired tidal volume (5 to 7 ml/kg) and
the respiratory muscles have been unloaded– One can start with lower pressures (e.g. 15 to 20 cm H20) and titrate up
until the desired tidal volume is reached.– One good clue that the desired inspiratory pressure is reached is the note of
a decreased frequency in respiratory rate
• FIO2:– set at the inspired oxygen which can give an O2 saturation of 92% or higher
• PEEP:– this can be added on to improve oxygenation or prevent shearing injury to
the alveoli
• TIDAL VOLUME will be dependent on:– Patient’s resistance and compliance– The preset Inspiratory Pressure– The preset Inspiratory Time (which can be adjusted by setting an
Inspiration:Expiration (I:E) time
PSV vs. PCV
PSV• Patient determines RR, VE, inspiratory
time – a purely spontaneous mode• Parameters
• Triggered by pt’s own breath• Limited by pressure• Affects inspiration only
• Uses• Complement volume-cycled modes (i.e.,
SIMV)• Does not augment TV but overcomes
resistance created by ventilator tubing
• PSV alone• Used alone for recovering intubated
pts who are not quite ready for extubation
• Augments inflation volumes during spontaneous breaths
• BiPAP (CPAP plus PS)
PCV• No Patient participation• Parameters
• Triggered by time• Limited by pressure• Affects inspiration only
• Disadvantages• Requires frequent
adjustments to maintain adequate VE
• Pt with noncompliant lungs may require alterations in inspiratory times to achieve adequate TV
Modes of Ventilation
• Bilevel Positive Airway Pressure (BiPAP)– An offshoot of PEEP/CPAP therapy– Most often used in NPPV– AKA
• Bilevel CPAP• Bilevel PEEP• Bilevel Pressure Support• Bilevel Pressure Assist• Bilevel Positive Pressure• Bilevel Airway Pressure
Modes of Ventilation
• Bilevel Positive Airway Pressure (BiPAP)– Commonly patient triggered but can be time
triggered, pressure targeted, flow or time cycled– The operator sets two pressure levels
• IPAP (Inspiratory Positive Airway Pressure)– IPAP is always set higher than EPAP– Augments VT and improves ventilation
• EPAP (Expiratory Positive Airway Pressure)– Prevents early airway closure and alveolar collapse at the end
of expiration by increasing (and normalizing) the functional residual capacity (FRC) of the lungs
– Facilitates better oxygenation
Modes of Ventilation
• Bilevel Positive Airway Pressure (BiPAP)– The operator sets two pressure levels
• IPAP• EPAP
NOTE: The pressure difference between IPAP and EPAP is pressure support
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
Vent settings to improve <oxygenation>
• PEEP • Increases FRC
• Prevents progressive atelectasis and intrapulmonary shunting
• Prevents repetitive opening/closing (injury)
• Recruits collapsed alveoli and improves V/Q matching• Resolves intrapulmonary shunting• Improves compliance
• Enables maintenance of adequate PaO2 at a safe FiO2 level
• Disadvantages• Increases intrathoracic pressure (may
require pulmonary a. catheter)• May lead to ARDS• Rupture: PTX, pulmonary edema
PEEP and FiO2 are adjusted in tandem
Oxygen delivery (DO2), not PaO2, should be used to assess optimal PEEP.
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
• TV
• Goal of 10 ml/kg• Risk of volutrauma
• Other means to decrease PaCO2
• Reduce muscular activity/seizures• Minimizing exogenous carb load• Controlling hypermetabolic states
• Permissive hypercapnea• 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
• PIP• Elevated PIP suggests need for
switch from volume-cycled to pressure-cycled mode
• Maintained at <45cm H2O to minimize barotrauma
• Plateau pressures• Pressure measured at the end
of inspiratory phase• Maintained at <30-35cm H2O to
minimize barotrauma
Alternative Modes• I:E inverse ratio ventilation (IRV)• ARDS and severe hypoxemia• Prolonged inspiratory time (3:1) leads to
better gas distribution with lower PIP• Elevated pressure improves alveolar
recruitment• No statistical advantage over PEEP, and
does not prevent repetitive collapse and reinflation
• Prone positioning• Addresses dependent atelectasis• Improved recruitment and FRC, relief of
diaphragmatic pressure from abdominal viscera, improved drainage of secretions
• Logistically difficult• No mortality benefit demonstrated
• ECHMO• Airway Pressure Release (APR)
• High-Frequency Oscillatory Ventilation (HFOV)• High-frequency, low amplitude
ventilation superimposed over elevated Paw
• Avoids repetitive alveolar open and closing that occur with low airway pressures
• Avoids overdistension that occurs at high airway pressures
• Well tolerated, consistent improvements in oxygenation, but unclear mortality benefits
• Disadvantages• Potential hemodynamic
compromise• Pneumothorax• Neuromuscular blocking agents
References
• Mechanical Ventilation for Nursing by M Dearing and C Shelley (ppt)
• Mechanical Ventilation Handout by DM Lieberman and AS Ho (ppt)
• Mechanical Ventilation by Marc Charles Parent (ppt)• Principles of Mechanical Ventilation RET 2284 by
Stultz (ppt)• Sena, MJ et al. Mechanical Ventilation. ACS Surgery:
Principles and Practice 2005; pg. 1-16.• Marino, PL. The ICU Book. 2nd edition. 1998.• Byrd, RP. Mechanical ventilation. Emedicine, 6/6/06.