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
problems related to positive pressure?
- ventilator induced lung injury
- reduction in cardiac output
- alterations in renal function & positive fluid balance
- impaired hepatic function
- increase intracranial pressure
- ventilation / perfusion mismatch
what is ventilator induced lung injury?
- Barotrauma- rupture or tear of alveoli as a result of excessive pressure volume or both
- volutrauma- refers to the local overdistention of normal alveoli.
- atelectrauma. Atelectotrauma, atelectrauma, cyclic atelectasis or repeated alveolar collapse and expansion are medical terms for the damage caused to the lung by mechanical ventilation under certain conditions.
- oxyegen toxicity Oxygen toxicity is lung damage that happens from breathing in too much extra (supplemental) oxygen. It’s also called oxygen poisoning. It can cause coughing and trouble breathing. In severe cases it can even cause death.
- biotrauma as a severe inflammatory response such as cytokines & chemokines produced in the lungs of patients who breathe by means of a mechanical ventilator for a long period of time
reduction in cardiac output?
3 mechanism are involved in development of decreased co
- positive pressure increase lung volume, alveolar pressure & pleural pressure. this positive pressure decrease the venous return to the heart
- pulmonary vascular resistance is increased as increased in lung volume results in possible compression of pulmonary capillaries
- increased ra afterload may result in increased rv end systolic volume causing the interventicular septum to bulge into the left ventricle. this decrease the size , volume, compliance & output of left ventricle
alterations in renal function & positive fluid balance?
reduction of co may lead to reduction of renal blood flow. A decrease in renal perfusion may result in stimulation of rennin angiotensin aldosterone system causes retention of sodium and water
impared hepatic function
the downward movement of diaphragm & impaired venous return lead to increase in portal veins pressure followed by decrease portal venous flow to liver and impairment of bile & hepatic vein flow
increased intracranial pressure
increase in superior vena cava and jugular vein pressure diminishes cerebral venous outflow and as a result increase intracranial pressure
ventilation perfusion mismatch
b/q mismatch may occur as a result of alveolar overdistenion which result in compression of adjacent pulmonary capillaries and regional hyperfusion
that increase in dead space ventilation decreased carbon dioxide elimination
overdistension may also result in redistribution of pulmonary blood flow to unventilated region which result in hypoxemia
infection?
factor leading to infection include poor hygiene, aspiration contaminated respiratory therapy equipment, poor hand washing by caregiver breach of aseptic technique during suctioning or handing of respiratory equipment impairment of mucociliary system inadequate hydration poor nutrition
patient anxiety and stress
sedation and analgesic
communication
