Acute Respiratory Syndrome

Question 1

Definition

Answer 1

ARDS is a form of hypoxemic respiratory failure due to inflammatory injury to alveolar
capillary barrier

Question 2

Etiology

Answer 2

acute endothelial damage resulting from
Aspiration
Infection / sepsis
Pancreatitis
Multiple blood transfusions
Lung injury
Major trauma / burns
Near-drowning
Drug overdose

Question 3

Histology
Exudative

Answer 3

Initially
Hyaline membrane comprised of fibrin forms

Question 4

Histology
Proliferative

Answer 4

3 days
Alveolar exudate resolves/organizes

Question 5

Histology
Fibrotic

Answer 5

3-4 weeks
Alveolar ducts and spaces undergo fibrosis

Question 6

Symptoms

Answer 6

Can manifest within 1 week of known clinical insult
Dyspnea / shortness of breath
Fever

Question 7

Physical Exam

Answer 7

Tachypnea / intercostal retractions
Bilateral rales/crackles and rhonchi
Mottled, cyanotic skin

Question 8

Evaluation
Timing

Answer 8

Within 1 week of clinical insult or new/worsening symptoms

Question 9

Evaluation
Chest Imaging

Answer 9

Diffuse bilateral opacities not explained by effusions, lobar/lung collapse, or nodules

Question 10

Evaluation
Origin of edema not fully explained by cardiac failure or fluid overload

Answer 10

Rule out cardiogenic pulmonary edema via objective factors (e.g., BNP, echocardiogram)

Explore other etiologies of ARDS via bronchoalveolar lavage or flexible bronchoscopy if clinical history is inadequate

Question 11

Evaluation
Severity of hypoxemia

Answer 11

Mild: PaO2 / FiO2 ratio 200 to 300 mm Hg with peak end-expiratory pressure
(PEEP) or continuous positive airway pressure (CPAP) > 5 cm H2O

Moderate: PaO2 / FiO2 ratio 100 to 200 mm Hg with PEEP > 5 cm H2O

Severe: PaO2 / FiO2 ratio less than 100 mm Hg with PEEP > 5 cm H2O

Question 12

Non-operative Treatment

Answer 12

Treat the underlying pathology/disease
Conservative fluid management with diuresis
Ensure adequate nutrition, ideally enteral
Stress ulcer and DVT prophylaxis
Prevention and management of nosocomial infections

Question 13

Operative/ interventional treatment

Answer 13

Mechanical ventilation; low tidal volume: goal of 4-6 cc/kg ideal body weight to maintain plateau
pressure of <30 cm H2O
High plateau pressure can cause volutrauma on alveoli
Oxygenation: goal of PaO2 55-80 mm Hg or SaO2 88-95%
Can be attained by adjusting peak end-expiratory pressure (PEEP)
pH goal of 7.3 to 7.45
Inspiratory:expiratory ratio goal of 1:1 to 1:3

Question 14

Prognosis

Answer 14

High mortality rate (50% overall) is associated with ARDS even in setting of ICU

Question 15

Prevention

Answer 15

Closely monitor PEEP in patients at-risk of ARDS
Serial X-rays in concerning patients can assist in early identification and
intervention

Question 16

Complications

Answer 16

Pneumothorax secondary to ventilator with high PEEP

Question 17

High Yield

Answer 17

Pulmonary capillary wedge pressure is no longer used in the diagnostic criteria of
ARDS, especially since Swan-Ganz catheters are less used in the critical care setting
today

However, you may still see questions regarding PCWP in ARDS patients because of its
physiological lesson
If PCWP is < 12 mm Hg, cardiogenic pulmonary edema is not likely
If PCWP is > 15 mm Hg, cardiogenic pulmonary edema is more likely