Respiratory

Question 1

What is the gold standard for evaluating gas exchange function of the lung?

Answer 1

Arterial blood gas

Question 2

Define hypoxemia

Answer 2

PaO2 less than 80 mmHg

Question 3

List the 5 major causes for hypoxemia

Answer 3

1. Low partial pressure of inspired oxygen (low PiO2)
2. Alveolar hypoventilation
3. Ventilation-perfusion inequality
4. Right-to-left shunt
5. Diffusion impairment

Question 4

What is the formula for alveolar partial pressure of oxygen (PAO2)?

Answer 4

PAO2 = [FiO2 * (PB - PH2O)] - PaCO2/RQ)
FiO2 = fraction of inspired oxygen (21% at room air)
PB = barometric pressure in mmHg
PH2O = water vapor pressure (at body temperature) in mmHg
RQ = respiratory quotient (Ratio of oxygen consumed and carbon dioxide produced during metabolism of mixed metabolic fuels; Normally 0.8)

Question 5

What is the primary determinant of PAO2

Answer 5

Ventilation

Question 6

What is the A-a gradient?

Answer 6

Difference between the estimated PAO2 and measured PaO2. Normally <10-15 mmHg and up to 100% when FiO2 = 100%.

Question 7

In a V/Q mismatch, what is the cause of a decreased V/Q (less than 1), and what are differential diagnoses?

Answer 7

Obstruction to ventilation
Ddx: Airway obstruction, pulmonary edema, pneumonia, asthma

Question 8

In a V/Q mismatch, what is the cause of an increased V/Q (greater than 1), and what are differential diagnoses?

Answer 8

Obstruction to blood flow
Ddx: Pulmonary thromboembolism

Question 9

True or false: A diffusion impairment is responsive to supplemental oxygen.

Answer 9

True

Question 10

Which of the five major causes of hypoxemia is not responsive to supplemental oxygen?

Answer 10

Left-to-right shunt

Question 11

What is the oxygen dissociation curve?

Answer 11

The oxygen dissociation curve is a graphical representation that shows the relationship between the oxygen saturation of hemoglobin and the partial pressure of oxygen in the blood. It helps illustrate how readily hemoglobin in the red blood cells picks up and releases oxygen molecules into tissues throughout the body.

Question 12

What is 2,3-diphosphoglycerate (2,3 DGP)?

Answer 12

A molecule that is an end product of RBC metabolism that regulates hemoglobin oxygen binding affinity. It binds to hemoglobin and lowers its affinity for oxygen, facilitating the release of oxygen into the tissues, particularly under conditions of lower oxygen availability or higher demand, such as during physical activity or at high altitudes.

Question 13

List causes of a left shift in the oxygen dissociation curve.

Answer 13

Left shift = Increased affinity for O2
1. Decreased H+
2. Decreased PCO2
3. Decreased temperature
4. Decreased 2,3 DGP

Question 14

List causes of a right shift in the oxygen dissociation curve.

Answer 14

Right shift = Decreased affinity for O2
1. Increased H+ (more acidic)
2. Increased PCO2
3. Increased temperature
4. Increased 2,3 DPG
5. Increased O2 demand (e.g., exercise)

Question 15

What is C-reactive protein (CRP)?

Answer 15

A highly sensitive acute phase protein produced by the liver with increased production shortly after initiation of infectious, immunologic, neoplastic, or traumatic processes.

Question 16

How is CRP testing useful in cases of respiratory disease?

Answer 16

Aids in discriminating between bronchopneumonia and other pulmonary diseases. Can be used to assess response to treatment of bronchopneumonia since serum CRP concentrations decrease rapidly after initiation of antibiotic treatment.

Question 17

What is cytochrome b5 reductase deficiency?

Answer 17

A disease in which there is a decrease in functional cytochrome b5 reductase which is the primary pathway by which methemoglobin is reduced back to hemoglobin.

Question 18

What genetic abnormality causes cytochrome b5 reductase deficiency?

Answer 18

2 missense variants in the CYB5R3 gene resulting in either Arg219pro or Ile194Leu substitutions.

Question 19

How is cytochrome b5 reductase deficiency diagnosed?

Answer 19

One drop of blood from the patient is placed on a piece of absorbent white paper and a drop of normal control blood is placed next to it. If the methemoglobin content is 10%, the patient’s blood should have a noticeably brown coloration compared to the bright red color of the control blood.

Question 20

Patients with cytochrome b5 reductase deficiency typically have a normal life expectancy with minimal clinical signs. If clinical signs arise, what is the treatment of choice?

Answer 20

Methylene blue (MB): An NADPH driven reductase pathway converts MB to leukomethylene blue, the reducing agent responsible for reduction of methemoglobin to hemoglobin. This is given as 1 mg/kg IV over 20 min.

Question 21

What is idiopathic eosinophilic bronchopneumopathy (EBP)?

Answer 21

A disease characterized by eosinophilic infiltration of the pulmonary and bronchial mucosa, considered to be manifestations of immunological hypersensitivity

Question 22

Which two breeds are predominately affected by eosinophilic bronchopneumopathy (EBP)?

Answer 22

Siberian Husky
Alaskan Malamute

Question 23

How often is a peripheral eosinophilia noted in dogs with eosinophilic bronchopneumopathy (EBP)?

Answer 23

60% of cases

Question 24

What gene mutation is associated with primary ciliary dyskinesia in Old English Sheepdogs?

Answer 24

CCDC39

Question 25

Kartagener’s syndrome occurs in 50% of cases of primary ciliary dyskinesia. What is Kartagener’s syndrome?

Answer 25

A subset of primary ciliary dyskinesia in which patients also have bronchiectasis, situs inverses, and chronic rhinosinusitis.

Question 26

What is bronchiectasis?

Answer 26

An abnormal and permanent dilatation and distortion of subsegmental airways, resulting from chronic airway inflammation that damages elastic components of the bronchi leading to bronchial wall destruction and impaired clearance of respiratory secretions.

Question 27

What is bronchomalacia?

Answer 27

Weakness of the wall of principal or smaller bronchi leading to collapse of the bronchial wall.

Question 28

What is Paragonimus kellicotti?

Answer 28

The trematode lung fluke that can infect dogs and cats.

Question 29

Describe the pathogenesis of Paragonimus kellicotti.

Answer 29

Typically infection occurs after eating crayfish. The parasite migrates from the intestine into the peritoneum, across the diaphragm, and into the pleural space. Soon thereafter, immature flukes invade the subpleural tissues, where they cause eosinophilic and neutrophilic inflammation. Mature flukes have access through a series of communicating “tunnels” to the bronchioles, allowing ova to be coughed up and swallowed before fecal shedding.

Question 30

What is the treatment for Paragonimus kellicotti?

Answer 30

Fenbendazole 50 mg/kg PO q24h for 10-14 days or praziquantel 25 mg/kg PO q8h for 3 days.

Question 31

What are Filaroides spp? Name the two species of concern in dogs and cats.

Answer 31

These are adult nematodes that reside in alveolar spaces and terminal bronchioles. Filaroides hirthi and Filaroides milksi are the two species of concern. Transmission is fecal-oral or transmammary.

Question 32

What is the treatment for a Filaroides spp infection?

Answer 32

Fenbendazole (25-50 mg/kg PO q24h for 10-14 days) or ivermectin (0.4 mg/kg SC for dogs lacking MDR-1 mutation, repeated in 1 week) is used most often.

Question 33

What is Angiostrongylus vasorum?

Answer 33

AKA the French heartworm, it is a metastrongylid parasite of dogs that can cause respiratory disease or bleeding diathesis.

Question 34

Describe the pathogenesis of Angiostrongylus vasorum.

Answer 34

Dogs are infected after consuming infected intermediate (i.e., mollusk) or paratenic (e.g., frog) hosts; L3 larvae are liberated into the intestine to the liver, then L4 and young adults migrate to the pulmonary vasculature via hepatic veins and the vena cava. Adults in right ventricle and pulmonary arteries lay eggs which are carried to the pulmonary capillaries, where they hatch to L1 larvae. The L1 larvae then migrate into the alveoli. After gaining entrance to the airways, the larvae can be coughed up and swallowed.

Question 35

What are the treatment options for Angiostrongylus vasorum?

Answer 35

Fenbendazole (25-50 mg/kg PO q24h for 10-20 days) or
Ivermectin (0.2 mg/kg SC each week for two doses) or
Milbemycin oxime (0.5 mg/kg PO each week for 4 weeks)

Question 36

How are mycobacteria identified on cytology?

Answer 36

Acid-fast stain. Without the stain, they may be seen as “negative-staining” or “empty” rods.

Question 37

What is the treatment protocol for cats with mycobacterium avium and other saprophytic mycobacteria?

Answer 37

Rifampicin, a fluoroquinolone (preferably pradofloxacin), and clarithromycin or azithromycin

Question 38

What is Yersinia pestis?

Answer 38

A gram-negative coccobacillus that is the etiologic agent of Plague.

Question 39

Describe the three forms of Plague.

Answer 39

1. Bubonic plague: Development of suppurative lymphadenitis (buboes) initially in the submandibular and cervical nodes. Sometimes bubo formation is accompanied by bacteremia, endotoxemia, sepsis, and formation of hemorrhagic, neutrophilic, and necrotizing lesions in many organs.
2. Septicemic form: Sepsis without identifiable buboes
3. Pneumonic plague: Hematogenous spread of bacteria to lungs, less often by inhalation of organism resulting in dyspnea/cough

Question 40

Describe the pathogenesis of Plague.

Answer 40

Y. pestis is taken up by mononuclear cells where it survives, replicates, and produces F1 capsular envelope antigen (the envelope helps resist phagocytosis. It is then carried by lymphatics to regional lymph nodes.

Question 41

How is Plague diagnosed?

Answer 41

1. Heat-fixed slides prepared from lymph node aspirates can be submitted for immunofluorescent antibody (direct IFA) against the F1 envelope antigen.
2. Cytologic examination of exudate or lymph node aspirates typically reveals bipolar, safety-pin-shaped Gram-negative rods.

Question 42

What is the treatment of Plague?

Answer 42

Aminoglycosides, fluoroquinolones, chloramphenicol, and tetracyclines all have been used for the treatment of Y. pestis.
- Tetracyclines (doxycycline 10 mg/kg/day for 10 days)
- Aminoglycosides (gentamicin 5-8 mg/kg IV, IM, SC q24h for 10 days)
- Fluoroquinolones (enrofloxacin 5 mg/kg IV, IM, or PO q24h for 10 days)
- Treat for flea infestation

Question 43

Name the two specific strains of influenza A virus that cause canine influenza.

Answer 43

H3N8: From 2004 outbreak in Greyhound kennels
H3N2: From Asian epidemic that spread to USA

Question 44

Classify the influenza virus in dogs (genetic makeup/envelope).

Answer 44

Family Orthomyxoviridae
Negative-sense, single-stranded, RNA virus
Enveloped

Question 45

What is Pneumocystis carinii (now Pneumocystis jirovecii)?

Answer 45

A saprophytic fungus that causes opportunistic pneumonia that primarily affects immunocompromised animals.

Question 46

List immunodeficiencies (and associated breeds) that can result in opportunistic Pneumocystosis.

Answer 46

1. Common variable immunodeficiency (Dachshunds, Pomeranians)
2. IgG deficiency (Cavalier King Charles Spaniels)
3. CD40 ligand deficiency (Shih Tzu)

Question 47

What is the treatment of choice for Pneumocystosis?

Answer 47

Trimethorpim-sulfa (TMS); 15 mg/kg, every 8 hours, or 30 mg/kg, every 12 hours, for 3 weeks