icu mechanical ventilation Flashcards
what is shunt?
normal
perfusion but decreased or no ventilation
physiological example: normal shunting from
pleural coronary circulation, dormant alveoli
pathologic: atelectasis , secretion, emphysema
what is dead?
normal ventilation but decreased or no perfusion
physiological example: peripheral airway like trachea, bronchi
pathologic: pulmonary embolism
what is synchronised intermittent mandatory ventilation?
- pt. receive a pre set number of breath per minute of pre set tidal volume between these machine initiated breath, pt. may initiate spontaneous breaths depending on his respiratory efforts.
- SIMV differs from IMV in that instead of delivering the mandatory breath at precise time regardless of where the pt. is in his ventilatory cycle, the ventilator delivers the mandatory breath simultaneously as it senses the pt. inspiratory effort.If the pt. does not make the inspiratory effort at the given time, mandatory breath is delivered.
- SIMV differs from A/c mode in a way that in the A/c mode the pt. receive a guaranteed TV whereas in the SIMV the tv variable as it depands on the pt. effort
what is indication in simv?
normal respiratory drive but pt. is unable to perform all the wob
To wean pt. off the ventilator
what is advantages in SIMV?
less atrophy of muscle
negative effect of positive pressure breathing are less as compared to A/c or cmv mode
prevention of stacking of breath
what is the disadvantages in SIMV?
if the sensitivity is not set properly,The pt. WOB may increase
what is assist control?
- ventilator delivers a pre set number of breath per minute of pre se tidal volume between these machine initiated breaths, pt. may trigger spontaneous breaths
- when the ventilator sense pt. effort the ventilator delivers the breath of pre set tidal volume
- the only work pt. performs is the negative inspiratory effort required to trigger the ventilator & the ventilator perform the rest of WOB.
- the difference between A/C & CMV is that in the A/c mode, the ventilator is sensitive to & the response to the pt. effort & allows some work from the ventilatory muscle
what is the indication of assist control?
- normal respiratory drive but weak muscle.
* normal respiratory drive but increased WOB
what is the advantage of assist control?
Allows pt. to control the rate of breathing & yet guarantees delivery of a minimal preset rate & volume
•allows some work from ventilatory muscle
what are the disadvantages of assist control?
there is pt. tendency for hyperventilation due to anxiety, pain , etc.
What is Positive end expiratory pressure?
PEEP is the application of a constant positive in the airways so that at end expiration the pressure is never allowed to return to the atmospheric pressure
the positive pressure is applied throughout the ventilatory cycle but is used for its physiologic effect at end expiration
•normal setting:5-20 cms of water
•by exerting the positive pressure at end expiration PEEP
>recruit atelectatic alveoli
>internally splint & distend already patent alveoli
>counteract alveoli & small airway colusure during expiration
indication in peep?
in pt. with pa02 <60 mmhg , peep can improve oxygenation
for internal stabilisation of chest wall, to minimise paradoxical chest wall movement in flail chest
relatives contraindications in peep?
unilateral lung diseases increase in FRC pneumothorax bronchi- pleural fistula intra cardiac shunt
adverse effect of peep?
•reduction in cardiac output becoz of
- decrease in venom return
- increase pulmonary vascular resistance
- impaired LV diastolic filling becoz of sift of the interventricular septum
complications of mechanical ventilation?
- problems related to positive pressure
- problems related to artificial airway
- infection
- pt. anxiety & stress
- gastric distress
- complications attributed operations or operator of the ventilator