Ventilators Flashcards
Pleateau pressures should generally be kept below ___
Pleateau pressures should generally be kept below 30 mmHg
To limit barotrauma
Anyone being mechanically ventilated should have ___ to prevent aspiration and VAP
Anyone being mechanically ventilated should have the head of the bed elevated to at least 45 degrees to prevent aspiration and VAP
Atrophy of the diaphragm may occur in ___ if a patient is not actively participating in ventilation
Atrophy of the diaphragm may occur in 2 weeks or less if a patient is not actively participating in ventilation
Most patients will be started on ___ for mechanical ventilation
Most patients will be started on assist control mode for mechanical ventilation
AC mode entails: Fixed tidal volume either at set intervals or whenever the patient initiates a breath. Volume will always be the same irrespective of pressures required to achieve it.
You will want to wean patients off of this mode onto pressure support as soon as feasible to maintain the patient’s respiratory control and respiratory muscle strength.
Best initial settings for a patient requiring AC mechanical ventilation
6 mL/kg TV
Pleateau pressure < 30 cm H2O
PEEP of 5 cm H2O
FiO2 100%
Acceptable RR
IV lidocaine prior to intubation
May decrease risk of cardiac arrhythmia and reduce the bronchospasm induced by ETT insertion into the trachea.
MV-associated anxiety
Best way to minimize this is with a mode that utilizes patient-initiated breaths
Synchronized intermittent mandatory ventilation (SIMV)
Delivers a mandatory number of breaths with a set volume while at the same time allowing spontaneous breaths.
Associated with improved synchronization between the patient’s natural breathing pattern and the MV. So, it may be a good weaning mode (AC -> SIMV -> Pressure support)
When is extubation considered successful?
When reintubation is not required within the next 48 hours
Who gets daily CXRs for ventilator positioning and complications?
Everyone on MV who is in the acute phase of disease
Once they are relatively stabilized, you no longer need to check unless there is a specific concern
Recommended placement of the EET with respect to the carina
3-4 cm above the carina
To avoid descending into a mainstem bronchus with chin motion
Volume vs time for different modes of mechanical ventilation:
- Controlled ventilation
- Assist-controlled ventilation
- Synchronous intermittent mandatory ventilation
- Pressure support ventilation + SIMV
- High frequency positive pressure ventilation
- Volume diffusive respirator
Risks of auto-PEEP
Auto-PEEP is notorious for causing hypotension and hemodynamic instability if unmonitored
Ensuring that the patient has adequate circulating volume helps to prevent these complications by reducing the compressibility of small pulmonary vessels.
What is auto-PEEP?
Auto-PEEP is the result of ventilator tachypnea with breath-stacking due to insufficient exhalatory time
Lengthening the expiratory time will decrease auto-PEEP, but may also result in aoveolar de-recruitment
With SIMV, at least ___ should always be applied
With SIMV, at least 5 cm H2O of PEEP should always be applied
This helps prevent alveolar derecruitment on irregular breathing
Difference between PCV and PSV modes
With PCV, there is a minimum preset pressure that MUST be achieved with every patient-initiated breath
PCV will only activate if the patient’s own pressure is insufficient to reach this goal
PSV and PCV are best used when. . .
. . . there is concern for barotrauma and low airway pressures are required
As in patients with pneumothorax
Jet ventilation
Rarely used in clinical practice
Bronchopleural fistula is the main situation where it may be required, typically in neonates.
High frequency (RR 180-600), low volume ventilation. Patient must be paralyzed for this type of ventilation.
Volumetric diffusive respiration
High frequency ventilation, “percussive” ventilation
Helps clear the airways of secretions.
Indications include cystic fibrosis and smoke inhalation injury, both due to copious secretions.
“Ventilator bundle”
- Head elevation at 45 degrees
- Sedation with daily sedative interruption
- DVT prophylaxis (pneumoboots, SQH)
- GI prophylaxis (famotidine or PPI)
- Daily spontaneous breathing trial
When using an ETT, aerosolized medications. . .
. . . must have their dosage doubled
Since you lose a lot of medication in the tubing
AC ventilation mode is likely to result in atypical __ values
AC ventilation mode is likely to result in atypical pCO2 values
This is because AC does not take into account the patient’s own regulation of respiratory drive, frequently resulting in hypocapnia or, less likely, hypercapnia.
For this reason, PS-SIMV is superior if a patient has low pCO2.
How do you want to ventilate a patient with ARDS?
Low volume ventilation with PEEP
This minimizes barotrauma while recruiting alveoli for gas exchange.
Do you need neuromuscular blockade on a ventilated patient?
No! Only for intubation, if even that.
It should be avoided since it is associated with long-term neurologic side effects.
Unnecessary changing of or finagling with the tubing of the ventilator. . .
. . . increases the risk of VAP
Artificial noses
Basically internal humidifiers that are part of the ventilator
These redue the risk of waterborne respiratory infections when compared with external in-line humidifiers.
Steps of the ventilator weaning process
- Treatment of acute respiratory failure
- Clinical judgement that weaning may be possible based on clinical status
- Usually PaO2 < 60 mmHg, FiO2 < 60%, RR < 25
- Assessment of the readiness to wean
- RSBI index: RR / TVLiters < 105
- Spontaneous breathing trial while on sedation vacation
- Extubation (may use BiPAP bridge)
- Possible reintubation
Optimal nutrition for a patient on a ventilator
Avoidance of carbohydrates is optimal, as they increase the respiratory coefficient and will produce extra CO2 requiring additional ventilation.
Fatty acids are preferred for their increased energy density and reduced CO2 production.
A negative inspiratory force greater than ___ is predictive of successful weaning from mechanical ventilation.
A negative inspiratory force greater than -25 cm H2O is predictive of successful weaning from mechanical ventilation.
Utilizing a tracheostomy in ventilation
Very useful for weaning difficult patients. A tracheostomy tube is usually far less irritating to the patient than an ETT, and the reduced need for sedation facilitates weaning.
Also provides a secure airway, minimizing the work of breathing and minimizing the risk of VAP.
Simplest and most effective way to wean patients from mechanical ventilation
Pressure support ventilation (with gradually decreasing support as tolerated)
Cardiopulmonary stress of extubation
When a patient is no longer being mechanically ventilated, their respiratory effort and myocardial oxygen demand increase in order to take over the work of ventilation
This cardiac stress may produce hypotension and hemodynamic instability in critically ill patients.
The solution is to avoid reintubating unless absolutely necessary and instead provide external noninvasive ventilatory support.
Parameters you are looking for to gauge that a patient is ready for extubation
RSBI ( RR / VT, Liters ) < 105
Inspiratory force > 25 cm H2O
