ARDS & Bronchiolitis Obliterans

Question 1

Acute Respiratory Distress Syndrome (ARDS)

Answer 1

Aka “Shock Lung”

Not a particular disease, but a syndrome of a diseased lung itself caused by some inciting event.

Question 2

What is the 5th vital signs?

Answer 2

Pain, but also always ask for O2 saturation along with vital signs

Question 3

Causes of Hypoxia:

Answer 3

Diffusion.
Hypoventilation. 
V/Q shunt. 
Right to Left shunt. 
Low inspired oxygen.

Question 4

General (Berlin) definition of ards:

Answer 4

“ARDS is an acute, diffuse, inflammatory lung injury that leads to increased pulmonary vascular permeability, increased lung weight, and a loss of aerated tissue”

Question 5

ARDS etiology:

Answer 5

Incidence of 86/100K person-years
190, 000 cases of ARDS in US per year. 
Most common causes: Pneumonia, aspiration, trauma, transfusions, drugs and alcohol. 
Can be anything that injures the lung!
>60 identified causes.

Question 6

ARDS pathophys.

Answer 6

Impaired gas exchange.
Reduced lung compliance.
Pulmonary hypertension.

Question 7

ARDS stages:

Answer 7

1. Exudative (acute inflammation)
2. 7-10 days later, proliferative phase (chronic, proliferative inflammation involving myofibroblasts).
3. Fibrotic stage– diffuse fibrosis (scarring).

Question 8

ARDS clinical presentation:

Answer 8

Rapid development of respiratory failure
Bilateral (often diffuse) crackles.
Presence of Inciting event.
Hypoxia

Question 9

ARDS: Berlin definition

Answer 9

Timing: Within 1 week of clinical insult.
Imaging: bilateral opacities.
Origin of pulmonary edema: not explained by cardiac failure or fluid overload.
Hypoxia: PaO2/FiO2 ratio =300.

Question 10

P:F ratio:

Answer 10

PaO2 on ABG in mmHg or % saturation if ABG not available. 
Divided by fraction of inspired oxygen. 
PaO2 of 55/21% inspired oxygen. 
55/.21=262. 
Score of =300 is consistent with ARDS.

Question 11

Classifying ARDS based on PaO2:FiO2 ratio:

Answer 11

= 300 = ARDS
201-300 = Mild ARDS
101-200 = Moderate ARDS
= 100 = Severe ARDS

Question 12

ARDS Dx workup:

Answer 12

Look for other causes of pulmonary edema, like CHF (BNP, echocardiogram). Check BNP and CBC to look for evidence of renal failure, anemia.
History of respiratory exposures, trauma, viral infection. Sick contacts.
CXR for pneumonia, respiratory cultures, flu test.

Question 13

ARDS Tx:

Answer 13

Treat the underlying cause.
Bipap if possible, but if progresses will need intubation.
Mechanical ventilation if needed.

Question 14

Low Tidal Volume Ventilation:

Answer 14

Studies have shown survival significantly improved with low tidal volume ventilation of 6cc/kg of ideal body weight.
Low tidal volume reduced stretching of lungs and reduced inflammation.

Question 15

Prognosis of ARDS:

Answer 15

Mortality in ARDS is 40%, reduced to 31% with low tidal volume ventilation.
Survival has been improving.
Mortality is higher in more severe ARDS, and higher ages.
Mortality is lower in lower age, less severe ARDS, and obesity.

Question 16

ARDS complications:

Answer 16

ARDS survivors are left with residual disability that often lasts > 1 year.
Persistent problems include cognitive dysfunction, PTSD, anxiety/depression.
Reduced lung function and persistent dyspnea are common following ARDS.

Question 17

ARDS summary:

Answer 17

Inflammatory disease»Acute onset, diffuse involvement» severe hypoxia.
Most common caused by pneumonia, sepsis, aspiration.
P/F<300, bilateral infiltrates not from cardiac cause
Low tidal volume ventilation of 6cc/kg improves outcomes.

Question 18

Bronchiolitis Obliterans:

Answer 18

Inflammation of the small airways (<2mm).

Non-reversible.

Question 19

B.O. Vs. Asthma:

Answer 19

Chronic inflammatory disease of the larger bronchioles.
Typically involves an allergic reaction to environmental exposures.
Symptoms are acute» identifiable triggers which lead to airway inflammation.
*Asthma is reversible.

Question 20

B.O. vs. COPD/Chronic Bronchitis

Answer 20

chronic, inflammation of the large to small airways» bronchi»bronchioles.
Loss of functioning alveolar sacs and non-reversible airway constriction.
Symptoms are chronic, slowly progressive.
Etiology is usually smoking and long term occupational exposures.

Question 21

B.O. Vs. Childhood bronchiolitis:

Answer 21

Acute inflammation of the bronchioles in children.
Symptoms resolve after disease runs its course.
Usual etiology is viral.

Question 22

B.O. vs. B.O. Syndrome:

Answer 22

Occurs in transplant recipients.
Occurs in bone marrow transplant recipients and as a graft vs host disease.
Occurs in lung transplant recipients as graft rejection.
Poor prognosis in both situations.

Question 23

B.O. vs. B.O.O.P.

Answer 23

Bronchiolitis obliterans organizing pneumonia.
Involves proliferation of inflammation from bronchioles to the alveolar sacs.
Has been renamed as Cryptogenic Organizing Pneumonia (COP).

Question 24

B.O. Etiology:

Answer 24

Bronchiolitis obliterans in adults most commonly occurs as an acute injury to an exposure.

• Inhalational toxins, volatile chemicals,etc.
• Drug reaction- busulfan, gold, cocaine
• Infection: viral infections, bordetella, mycoplasma.
• Rheumatoid diseases.

Question 25

B.O. Clinical Findings:

Answer 25

Dyspnea, cough which are slowly progressive over weeks/months.
History of rheumatoid arthritis or toxin exposure.
Obtain a detailed work and hobby/home exposure history, in particular exposure to fumes.
Main challenge will be differentiating the disease from asthma
Obtain a detailed work and hobby/home exposure history, in particular exposure to fumes.

Question 26

B.O. Clinical findings cont.

Answer 26

Clinical findings are similar to asthma» dyspnea, cough, wheezing.
BUT: non-reversible, minimal relief from bronchodilators.
Chronic, slowly progressive symptoms, history of inhaled toxin exposure.

Question 27

B.O. diagnostic evaluation:

Answer 27

CXR finding- nonspecific.
PFT- non-reversible airflow obstruction.
Hi-res CT: bronchial wall thickening, mosaic pattern, Ground glass.

Question 28

Definitive B.O. diagnosis:

Answer 28

surgical lung biopsy

Question 29

B.O. bronchoscopy:

Answer 29

helpful to obtain cultures and biopsies. These are helpful in excluding other possibility like infection or malignancy, but can not diagnose the disease.

Question 30

B.O. TX:

Answer 30

Disease if often refractory to treatment.
-Removal of offending agent
-Symptomatic treatment with bronchodilator, cough suppressant.
-Oxygen therapy if o2 sat = 88%
Smoking cessation.
-Steroids??» often used but little benefit.

Question 31

B.O. Prognosis:

Answer 31

Variable, if the offending agent is removed early enough, symptom progression can be stopped.
If the offending agent is removed early enough, progression can be halted.
patients will progress to severe respiratory failure.
Lung transplantation.

Question 32

B.O. summary:

Answer 32

Consider B.O. in “asthma” with:
No reversibility, No COPD/emphysema. 
History of inhalational exposure. 
Minimal improvement with asthma Rx. 
Chronic, progressive dyspnea and cough over months and years.

Question 33

Popcorn lung:

Answer 33

Diacetyl: caused outbreak of bronchiolitis obliterans among popcorn factory workers.
Popcorn manufacturers removed it.
What popular consumer product contains diacetyl and other agents known to cause Bronchiolitis Obliterans?
-do you even vape bro?