12. Acute Respiratory Distress Syndrome (ARDS) & Acute Lung Injury (ALI)

Question 1

ARDS and ALI are syndromes caused by

Tip: this exam always includes several Q on this topic. study it!

Answer 1

a variety of acute conditions that trigger an inflammatory response, resulting in an increase in the permeability of the pulmonary capillary membrane, which allows a transudation of proteinaceous fluid into the interstitial and alveolar spaces. They may also be referred to as “noncardiogenic pulmonary edema.” Damage to Type II alveolar cells is one of the pathological consequences. Since these are the cells that are responsible for the production of surfactant, massive atelectasis occurs.

Question 2

All the criteria in table 4-16 must be present for a diagnosis of ARDS or ALI.

Answer 2

The pulmonary edema is not due to heart failure. Hypoexmia is REFRACTORY, meaning that the FiO2 is increased to the maximum of 100% and hypoxemia is still present.

Question 3

Since a shunt is present, __

Answer 3

PEEP needs to be provided in order to increase alveolar recruitment and treat the refractory hypoxemia.

Question 4

How does Peep treat a shunt?

Answer 4

by preventing alveolar collapse. It does not necessarily decrease pulmonary shunting.

Question 5

Criteria for ARDS

Answer 5

-Acute onset with precipitating even.
-Bilateral infiltrates consistent with pulmonary edema
-PaO2/FiO2 ratio less than/equal to 200 mmHg,
regardless of PEEP level
-PAOP less than/equal to 18 mmHg

Question 6

Criteria for ALI

Answer 6

-acute onset with precipitating event
-bilateral infiltrates consistent with pulmonary edema
-PaO2/FiO2 ratio between 201 and 300
-PAOP less than/equal to 18 mmHg

Question 7

PaO2/FiO2 example:

Pt receiving 50% FiO2 and PaO2 is 90:

Answer 7

90 ÷ 0.50 = 180

Question 8

PaO2/FiO2 example:
The pt is receiving 30% FiO2 and PaO2 is 110:

Answer 8

110 ÷ .30 = 367

Question 9

PaO2/FiO2 example:

Pt receiving room air and PaO2 is 62

Answer 9

62 ÷ .21 = 295

Question 10

PaO2/FiO2 example:

Pt is on 100% FiO2 and PaO2 is 95

Answer 10

95 ÷ 1.00 = 95

Question 11

Remember: it is not only the PaO2/FiO2 ratio that is to be considered when diagnosing ALI or ARDS; __

Answer 11

the other 3 factors also need to be present

Question 12

Surfactant

Answer 12

-Phospholipid/lipoprotein produced by Type II alveolar cells
-Stabilizes alveoli, “keeps them open”
-Increases lung compliance
-Eases work of breathing

Question 13

-With ARDS (destruction of Type II alveolar cells) leads to…

Answer 13

-Massive atelectasis, alveolar collapse
-Decreased compliance
- increased work of breathing
-decreased functional residual capacity (FRC)

Question 14

Figures 4-14 and tables 4-17 & 4-18 show the pathophysiology, etiology and signs/symptoms of ARDS and ALI

Answer 14

see figure 4-14

Question 15

Etiology of ARDS/ALI “Direct” Injury

Answer 15

-Aspiration
-Pneumonia
-Pulmonary contusion
-Fat/air embolism
-O2 toxicity
-Inhalation injury
-Drowning
-Transthoracic radiation

Question 16

Etiology of ARDS/ALI “Indirect” Injury

Answer 16

-Sepsis
-Shock
-Head Injury
-Non-thoracic trauma
-Blood Transfusion
-Pancreatitis
-Burns
-Heart bypass
-DIC

Question 17

Signs/Symptoms of ARDS/ALI - Early

Answer 17

-Tachycardia
-Apprehension, restlessness
-Mild dyspnea
-Respiratory alkalosis
-Few crackles
-Chest XR –>isolated infiltrate or “ground-glass”
appearance
-PaO2 on room air ~ 60 mmHg

Question 18

Signs/Symptoms of ARDS/ALI - Late

Answer 18

-Tachycardia, episodes of bradycardia
-Agitation
-Extreme dyspnea
-Respiratory and metabolic acidosis
-Crackles, wheezes
-CXR shows whiteout/bilateral infiltrates
-PaO2 on room air ~ 30 mmHg, refractory hypoxemia despite increased FiO2

Question 19

Treatment of ARDS/ALI

**Pulmonary Stabilization strategies

Answer 19

-Intubation with mechanical ventilation

-PEEP, usually 15 cm H2O or greater; monitor for barotrauma and decreased Cardiac Output; treat hypotension, but do NOT discontinue PEEP

-Limit plateau pressure to 30 cm H2O or less

-Limit tidal volume (Vt) to 5-6 mL/kg –> permissive hypercapnia” to prevent volutrauma.
-A low Vt will cause a rise in the the PaCO2 and a drop in the pH; however, pts tend to tolerate a pH as low as 7.2

Question 20

Treatment of ARDS/ALI

Cardiovascular stabilization

Answer 20

-Support the BP (fluids, vasopressors, especially when ARDS is due to septic shock).
-Monitor for and treat arrhythmias.

Question 21

Treatment of ARDS/ALI

Prone positioning:

Answer 21

Helps deliver blood flow to under perfused lung units, thereby improving ventilation/perfusion; keeps alveolar lung units open, thus improving gas exchange and preventing further injury
-Use extreme caution to avoid misplacement or loss
of airway
-Prevent a pressure injury

Question 22

Treatment of ARDS/ALI

Other important trmt

Answer 22

-Monitor acid-base balance
-DVT and stress ulcer prophylaxis
-analgesia, sedation
-nutritional support
-nitric oxide, prone positioning may provide
improvement in oxygenation
-coordinate the interdisciplinary team–PT, OT, and
dietician
-Prevent, identify organ failure
-Provide emotional support (to the pt and the pt’s
family)
-Monitor for complications
-NO STERIODS (except for select pts with COVID-19 pneumonia)

Question 23

Complications of ARDS/ALI

Answer 23

The mortality from ARDS is still around 30%, although pts do not die from hypoxemia. Instead, they die from multiple organ dysfunction syndrome (MODS) and other complications, as listed below:

-secondary infections
-pulmonary embolus
-ileus
-skin breakdown
-malnutrition
-barotrauma: pneumothorax, subcutaneous
emphysema