Chest Trauma, ALI, ARDS

Question 1

Define ARDS

Answer 1

Acute respiratory distress syndrome

A severe form of ALI
PaO2/FiO2

Question 2

Describe effects of direct trauma on pulmonary function

Answer 2

Aspiration (gastric contents destructs alveoli, infected fluid gives you pneumonia, particulate matter gives you atelectasis or collapse)

Near drowning (inflammatory response, denatured surfactant, destructs alveoli, intrapulmonary shunting)

Inhalation (steam only thermal damage, aldehydes, cast formation eww)

Question 3

Describe effects of mechanical trauma (rib # and flail segment) on pulmonary function

Answer 3

decreased rib mvmt
decreased gas mvmt generalized and localized = decreased PaO2
Increased load plus decreased ability to cope with load = increased PaCO2 and decreased efficiency
Decreased secretion mvmt due to insp volume
Long term decrease in RVC and PEFR

Question 4

Describe effects of mechanical trauma (pulmonary contusion) on pulmonary function

Answer 4

Oedema increases 48hrs
Infiltration and consolidation (alveolar haemorrhage)
Activation of coagulation cascade = impaired lung function
Decreased lung compliance
Decreased O2 mvmt
Long term = fibrosis, decreased VC, FRC, PEFR, PaO2

Question 5

Define ALI

Answer 5

Acute lung injury

PaO2/FiO2

Question 6

Describe the pathophysiology of ALI and ARDS

Answer 6

Exudative phase 5-7days
Fluid rich oedema in alveoli (increased permeability) surfactant dysfunction, micro vascular occlusion

Proliferative phase 7-14 days
Formation of hyaline membrane in alveoli (thickening endothelium, epithelium and interstitial space. Type I cells replaced by type II)

Fibrotic phase >2weeks
Decreased lung compliance, emphysematous changes (increase Raw), increased dead space, increased PaCO2, decreased PaO2

Question 7

List causes of ALI/ARDS

Answer 7

Direct lung injury eg pneumonia, lung contusion, near drowning, smoke inhalation

Indirect lung injury eg anything activating SIRS like sepsis, cardiopulmonary bypass, burns