Pathoma 9.3 Pulmonary Infections

Question 1

What is pneumonia?

Answer 1

Infection of the lung parenchyma (alveoli)

Question 2

Pneumonia occurs when the lung’s ______ are impaired.

Answer 2

Normal defenses

Question 3

What are some of the lung’s normal defenses?

Answer 3

1. Cough reflex (remove organisms and particles through coughing) 2. Mucociliary escalator (the lung conducting system is lined by respiratory epithelium which is ciliated. The cilia push the mucus that’s in the conducting system up the airway so it can be swallowed down the throat. This helps you clear any organisms or particles trapped in the mucus)

Question 4

What is the mucociliary escalator?

Answer 4

The lung conducting system is lined by respiratory epithelium which is ciliated. The cilia push the mucus that’s in the conducting system up the airway so it can be swallowed down the throat. This helps you clear any organisms or particles trapped in the mucus

Question 5

What is an example of something that can damage the mucociliary escalator?

Answer 5

A viral pneumonia could damage the respiratory epithelial cells. This damage could damage the mucociliary escalator which would leave the lungs at increased risk to develop bacterial pneumonias on top of the viral pneumonia.

Question 6

Name 3 examples of how normal defenses of the lung can be impaired.

Answer 6

1. Impaired cough reflex (unable to cough 2. Damage to mucociliary escalator (e.g. viral pneumonia damaging respiratory epithelial cells) 3. Mucus plugging (generally, any time that you block a tube in pathology, you get increased risk of infection distal to the block. Mucus plugging blocks airways which would increase infections distal to the block.)

Question 7

What are the clinical features of pneumonia?

Answer 7

1. Fevers and chills 2. Cough with yellow-green or rusty sputum 3. Tachypnea with pleuritic chest pain 4. Decreased breath sounds with dullness to percussion 5. Elevated WBC count (because patient is infected)

Question 8

What is pleuritic chest pain? What causes this?

Answer 8

Pain that arises when you breathe in, your lungs expand, and the pleura stretches. The pleura is innervated and is sensitized in the presence of bradykinin and prostaglandin-E2 that’s generated by inflammatory response (your 2 key mediators of pain).

Question 9

Pneumonia can cause ____ breath sounds with _____ to percussion. Why?

Answer 9

Decreased, dullness The lung is like a drum–it’s full of air. If you replace the air with consolidation due to the production of exudate from the inflammatory response, the exudate will decrease the breath sounds and a dullness to percussion.

Question 10

When patients have pneumonia, they can get fevers and chills. What causes this?

Answer 10

Organisms leaking into the blood

Question 11

What are the two common colors for sputum caused by pneumonia and what do the colors generally indicate?

Answer 11

Yellow-green (representing pus), rusty (representing blood)

Question 12

What are the diagnostic tools used for pneumonia?

Answer 12

1. Chest X-ray 2. Sputum gram stain (to help identify a bacteria) and culture (to help subtype) 3. Blood cultures (because organisms are often present in the blood)

Question 13

What 3 patterns are classically seen on chest X-ray for pneumonia? Which typically indicate bacterial infection and which indicate viral infection?

Answer 13

1. Lobar pneumonia (bacterial) 2. Bronchopneumonia (bacterial) 3. Interstitial pneumonia (viral)

Question 14

On CXR, what does a lobar pattern for pneumonia look like?

Answer 14

The consolidation is taking over an entire lobe

Question 15

On CXR, what does a bronchopneumonia pattern look like?

Answer 15

The consolidation runs along the small airways which appears in a patchy manner

Question 16

On CXR, what does interstitial pneumonia look like?

Answer 16

There is no consolidation present. Instead, you have inflammation within the interstitium of the lung. (The interstitium is the connective tissue of the alveolar air sacks). The key pattern in an x-ray is an increase in the lung markings.

Question 17

What are the 2 most common organisms that cause lobar pneumonia?

Answer 17

Streptococcus pneumoniae, Klebsiella pneumoniae

Question 18

What is seen here?

A. Lobar pneumonia

B. Bronchopneumonia

C. Interstitial pneumonia

Answer 18

Lobar pneumonia

Question 19

What’s going on here?

Answer 19

The air sacs are full of neutrophils (spots) and exudate (pink frothy material)

Question 20

Tell me about streptococcus pneumoniae (4)

Answer 20

Streptococcus pneumoniae is…

1. the most common cause of community-acquired pneumonia
2. the most common cause of secondary pneumonia (bacterial pneumonia superimposed ona viral upper respiratory tract infection)
3. usually seen in middle-aged adults and elderly
4. represents about 95% of lobar pneumonia cases

Question 21

Tell me about klebsiella pneumoniae. (5)

Answer 21

Klebsiella pneumoniae

1. makes up about 5% of all lobar pneumonias
2. is an enteric flora that is aspirated. Because it is aspirated, it is most often seen in people who are at increased risk for aspiration (E.g. elderly in nursing homes, alcoholics, etc)
3. often affects malnourished and debilitated individuals, especially elderly in nursing homes, alcoholics, and diabetics.
4. has a thick mucoid capsule which results in gelatinous sputum (currant jelly)
5. is often complicated by abcess

Question 22

What are the four classic phases of lobar pneumonia?

Answer 22

1. Congestion (congested vessels and edema)
2. Red hepatization (due to exudate, neutrophils, and hemorrhage filling the alveolar air spaces, giving the normally spongy lung a solid consistency)
3. Grey hepatization (due to degradation of red cells within the exudate)
4. Resolution

Question 23

What happens in the congestion phase of lobar pneumonia? (phase 1 of 4)

Answer 23

When you get an infection, you’re going to congest the blood vessels by dilating those blood vessels, increasing the amount of blood in the vessels, which results in edema.

Question 24

What happens in the red hepatization phase of lobar pneumonia? (phase 2 of 4)

Answer 24

You develop an exudate in the lung which contains neutrophils and some blood which fills the alveolar air sacs. This changes a normally spongy lung to a solid consistency–hence the term hepatization (liver like change to the normal spongy lung). It is red because of the red blood cells coming into the alveolar air space.

Question 25

What happens in the grey hepatization phase of lobar pneumonia? (phase 3 of 4)

Answer 25

The RBCs are eventually broken down and turn grey.

Question 26

What happens in the resolution phase of lobar pneumonia? (phase 4 of 4)

Answer 26

Exudate is resolved and healing begins.

After a patient gets pneumonia, the lung heals by regenerating the tissue that was normally present. The type 2 pneumocytes are the stem cells of the lung that help to regenerate the lining of the alveolar air sacks.

Question 27

What’s going on here?

Answer 27

Lobar pneumonia. On the right side is the consolidated lobe. You can see that it becomes solid instead of spongy (hepatization). In this particular case, the consolidation is full of red blood cells so this is the red hepatization phase (phase 2 of 4) of pneumonia. Once the red blood cells are broken down, it would turn grey for the grey hepatization phase and then resolve.