Topic 3: Pulmonary Response to CPB Flashcards
Atelectasis
A complete or partial collapse of a lung or
a lobe of the lung-develops when the alveoli become deflated and don’t inflate properly
most common pulmonary complication?
(70%)
ATELECTASIS
With Atelectasis – variable degree remains when lungs are re-expanded and ventilated
microscopic
lobar
hard to differentiate mechanical changes caused by bypass versus other parts of the surgery
Impaired Oxygenation
decreased functional residual capacity
— After general anesthesia?
By 20% after general anesthesia
Impaired Oxygenation
decreased functional residual capacity
— After CPB?
By 40-50 % after CPB
Impaired Oxygenation (4)
decreased functional residual capacity
decreased lung compliance
increased veno-arterial admixture
Alveolar-arterial oxygen gradient
P(A-a)O2 increasesFactors contributing to Atelectasis? Pre operative (3)
smoking, chronic bronchitis
obesity
cardiogenic pulmonary edema
Factors contributing to Atelectasis?
Intraoperative (3)
anesthesia: reduced surfactant function
passive ventilation
monotonous ventilator pattern
Factors contributing to Atelectasis?
Bypass (5)
surfactant inhibition
plasma, lung distention, lung ischemia
increased extravascular lung water (complement activation)
heart rests on immobile left lower lobe
open pleural cavity–accumulation of blood and fluid
what can we do to prevent ATELECTASIS?
Not Much
What can we do to prevent Atelectasis – Anesthesia controls what?
Anesthesia has more control (i.e. how lungs
are deflated and re-inflated)
PEEP (post-end expiratory pressure)
CPAP (Continuous positive airway pressure)
OLC (open lung concept)
Continuous positive airway pressure (CPAP) is?
the use of continuous positive pressure to maintain a continuous level of positive airway pressure in a spontaneously breathing patient. It is functionally the same as PEEP as both are used to stent alveoli open and recruit alveoli of the lungs for more surface area for ventilation.
Positive end-expiratory pressure (PEEP) is
the pressure in the lungs (alveolar pressure) above atmospheric pressure (the pressure outside of the body) that exists at the end of expiration.
The two types: are extrinsic PEEP (PEEP applied by a ventilator) and intrinsic PEEP (PEEP caused by a non-complete exhalation). Pressure that is applied or increased during an inspiration is termed pressure support.
Open Lung Ventilation - OLC
a strategy that is utilized by several modes of mechanical ventilation to combine low tidal volume and applied PEEP to maximize recruitment of alveoli. The low tidal volume aims to minimize alveolar overdistention and the PEEP minimizes cyclic atelectasis. Working in tandem the effects from both decrease the risk of ventilator-associated lung injury.
– “Pump Lung”: acute respiratory failure characteristics? (5)
lungs diffusely congested intra-alveolar and interstitial edema hemorrhagic atelectasis vessel lumina full of neutrophils diffuse swelling of endothelial cells
What might cause Acute Lung Injury ? (5)
Embolic load Membrane damage from immune response Decreased pulmonary blood flow Hemodilution Elevated pulmonary artery pressure
Emboli can lead to areas of ventilation/perfusion mismatching which can lead to what? (5)
aggregated proteins disintegrated platelets damaged neutrophils fibrin fat globules
Better the filtration=
more normal the lungs
