ARDS and Pathology of ARDS Flashcards
Components of ARDS
Low PaO2 (hypoxemia), bilateral infiltrates, low lung compliance. NO left atrial hypertension (problem is ALL pulmonary).
Definition of ARDS
PaO2/FIO2 re getting 100% fio2.
Definition of ALI
PaO2/FIO2 <300.
Causes of ARDS
Sepsis, pneumonia, aspiration, pancreatitis, burns, trauma, transfusions and toxic inhalation.
Pathologic state of ARDS and ALI
Diffuse alveolar damage. This is a failure of the alveolar capillary membrane which causes the flooding of alveolar airspaces with proteinaceous material.
Makeup of fluid in the alveolar spaces during ARDS
Proteinaceous
What happens when there is diffuse alveolar damage?
Proinflammatory cells release proinflammatory cytokines TNF, IL1, IL8. This also causes the production of oxygen derived free radicals.
What is the difference between fluid produced in ARDS and left heart failure?
Left heart failure = clean, not proinflammatory like ARDS
What happens during ARDS
Depletion of surfactant, disturbance of microcirculation, and fibroblast proliferation in the late stage.
What is the consequence of surfactant depletion?
Atalectasis, gas exchange disturbance and decreased pulmonary compliance
What is the consequence of microvascular disturbance?
Altered response to NO, cytokine induced activation of the coagulation cascade. This is enhanced by hypoxemia, so theres a high degree of vasoconstriction occurring.
Fibroblast proliferation in the late phase
After day 7, fibroblasts enter to help heal and lay down scartissue.
VILI
Ventilator induced lung injury. Positive airway pressure delivered to lung can cause barotrauma and volutrauma. This exacerbates the cytokine release and damages the good area of the lung.
Distribution of DAD in the lung?
Diffuse!!! Patchy!
Phases of ARDS and timing
Exudative phase to start off: Edema from 0-3d. Hyaline membranes from 1-14d. Proliferative phase begins at day 7 with interstitial inflammation and fibrosis.
When do type 2 pneumocytes become hypeprlastic
During the proliferative phase.
Imaging of ARDS
Bilateral infiltrates and hypoxemia, but normal left heart function. Imaging tells us nothing about the cause. The xray looks whited out. CT scan reveals the patchy nature of ARDS.
Management of ARDS
Treat underlying cause first. ARDS is a syndrome, not a disease. Then engage in lung protective strategy of mechanical ventilation with low tidal volume. Also supportive care like pain management and prevention of DVT
What happened to other interventions?
Steroids, prone positioning, inhaled NO. DIdn’t work