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What are the characteristics of mandatory breath?
Machine sets the start time and/or Vt
Machine triggers and cycles the breath
All mandatory breaths are unassisted
What are the characteristics of CMV (Control Mode Ventilation)
Ventilator will initiate breaths at a preset rate
Pt not allowed to initiate a breath and provides full ventilatory support
100% of breathing done by ventilator
What is CMV indicated for?
Head trauma/surgery patients (for induced hypocarbia)
Status asthmaticus (Progressive SOB and expiratory wheezes despite giving bronchodilator)
Traumatic flail chest (Blunt force trauma to the chest)
What needs to be done to the patient for CMV to be effective and why?
Sedation and/or muscular paralysis of patient needed to avoid patient ventilator asynchrony, so patient doesn\'t fight the ventiator.
What is the most common initial mode in ICU and CCU?
Assist/Control mode
What are the characteristics of assist/control mode?
Each breath is a positive pressure breath (assisted) which can be triggered by patient.
Provides full ventilatory support
What two parameters has to be set correctly for a patient to trigger a breath on A/C mode?
Trigger sensitivity
Peak flows
What factors can make a patient trigger breaths faster than back up rate are?
Metabolic acidosis
Inappropriately set trigger sensitivity
Inadequate peak flows
What type of patients on A/C mode are more likely to hyperventilate and air-trap (intrinsic peep)
How is hyperventilation and air-traping treated on Ventilator on A/C mode on a patient with COPD?
Switch the patient to SIMV mode
A/C can be provided in __________ or __________ targeting.
Volume or pressure
What is the most common mode of ventilation used worldwide?
Volume target A/C mde
A/C mode can be triggered by _____________ or _______________, flow ______________ and ___________ cycled.
Ventilator or patient trigger, flow limited, volume cycled
During volume cycled A/C mode what is set?
Targeted tidal volume and flow
During volume cycled A/C mode what varies based on changing airway resistance and compliance?
Peak airway pressure and I-time
What alarm should be used to monitor volume cycled A/C mode?
High minute volume alarm.
Volume cycle ventilation guarantees what?
Minimum tidal volume (minimum minute volume)
Because the flow during volume cycle A/C mode tends to follow the path of least resistance what happens to lung units with high compliance?
Become over ventilated and over distended?
During volume cycled A/C mode ventilation the least compliant diseased lung units remain under ventilated and results in what?
An uneven distribution of ventilation, causing ventilation/perfusion mismatch resulting in high local ventilating pressures and increases the potential for barotrauma/VILI
What are the disadvantages of volume targeted A/C mode?
V/Q mismatch and acid-base imbalance
Baraotrauma/ VILI
Hemodynamic impairment
What are the advantages of volume targeted A/C mode?
Guarantees minimum tidal volume
Prevent atelectasis
Pressure control ventilation is Triggered by what?
Patient or time triggered.
Pressure control ventilation is limited by what?
Pressure limited
Pressure control ventilation is cycled by what?
Time cycled
During pressure control ventilation what are constant?
PIP and I-Time are constant
On pressure control ventilation what varies?
Total volume and flow.
What are the indications for pressure control ventilation?
Very stiff non-compliant lungs (ARDS)
Chronic refractory hypoxemia (non-responsive hypoxemia)
Restrictive lung disease
also used as a lung protective strategy
When is pressure control ventilation used as a lung protective strategy?
PIP > 50
Plateau pressure > 30
delta P > 20 cmH2O (difference between PIP and PIP)
What are the advantages of pressure control ventilation.
Lower peak airway pressures minimizing the potential for volutrauma / barotraumas.
Imroves V/Q mismatch
Improved synchrony between patient and ventilator
More comfortable for the patient and is better tolerated by the patient
Decreases the Vd/Vt ratio
Decreases intrapulmonary shunting (better PaO2)
Promotes better distribution of gas and improves oxygenation
On pressure targeted ventilation high lung compliance/lower airway resistance can result in what?
Higher lung volumes.
In pressure targeted ventilation low lung compliance/ higher airway resistance can result in what?
Lower lung volumes.
What alarms are used to monitor pressure targeted ventilation?
Monitor with high and low tidal volume alarms.
What is IMV ( Intermittent Mechanical Ventilation)
Ventilation where breaths can be spontaneous or mandatory.
What are the advantages of IMV?
Prevent muscle atrophy
Allows patient to reach baseline ABG\'s
Decrease the mean intrathoracic pressure
Avoids decreased venous return
Avoids cardiac embarrassment
May avoid positive fluid balance, edema, and weight gain
Helps weaning gradually
May allow decreased use of pharmacological agents
What are the problems of IMV?
Machine breath is time cycled and not initiated by the patient
Fighting the ventilator
Breath stacking
What is SIMV?
A/C with spontaneous breaths (provides full and partial ventilatory support)
What is the second most common mode used in ICU and CCU?
VC SIMV with pressure support.
What are characteristics of SIMV?
Prevents stacking of breaths (Patient can breath spontaneously through demand valve)
Used on all microprocessor ventilators
Patients breathe spontaneously between mandatory machine breaths
The machine breath is patient triggered
What are the advantages of SIMV?
Allows the clinician to vary the amount of support provided from minimal to full ventilator support.
Keeps the airway pressures to the minimum
Weaning protocols effective in removing patients from mechanical support
May prevent hyperventilation and respiratory alkalosis
May provide lower mean airway pressure than assist control Ventilation
May help maintain ventilatory muscle strength and coordination
The benefits SIMV provide is lower mean airway pressure than assist control it which causes.
Less chance of developing intrinsic-PEEP
Less chance of barotrauma
Less hemodynamic impairment
What are the disadvantages of SIMV?
Possible development of respiratory muscle fatigue
Increase in WOB
When using SIMV what type of patients are at risk of developing respiratory muscle fatigue?
Patients with rapid shallow spontaneous breathing patterns
When using SIMV what can cause an increase in WOB?
Demand flow system, vent circuit, and artificial airway
Due to inappropriate trigger sensitivity or ventilator peak flow settings
How is Ve calculated on SIMV?
Mechanical Vt x Mechanical rate + Spontaneous Vt x Spontaneous rate
What Ventilator mode prevents air-trapping in COPD patients?
What are the characteristics of spontaneous breath?
Patient decides the start time and Vt
Patient triggers and cycles the breath
May be assisted or unassisted
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