Respiratory Flashcards
What are the cut-offs for pulmonary arterial (PA) systolic and mean pressures that define pulmonary hypertension (PH)?
PA systolic > 30mmHg, PA mean >20mmHg
List the 5 disease classes which can lead to pulmonary hypertension.
ACVIM consensus
Group 1 (pulmonary arterial hypertension) – primary diseases of the vasculature. E.g. idiopathic, familial, drugs/toxins, congenital heart disease (systemic-to-pulmonary shunts), HWD, veno-occlusive disease, persistent PH of newborns.
Group 2 (pulmonary venous hypertension) – left-sided heart disease & chronic increases in LA pressure. Valvular or myocardial dz. MOST COMMON in dogs.
Group 3 (PH associated with lung diseases or hypoxemia) – obstructive pulmonary disease, interstitial lung disease, alveolar hypoventilation, sleep apnea, chronic exposure to high altitude, developmental abnormalities.
Group 4 (PH associated with chronic thrombotic or embolic) – obstruction of proximal or distal PAs, non-thrombotic embolism (HWD or other parasites, neoplasia, foreign material – catheter or coil)
Group 5 (systemic & other disorders) – compression of pulmonary vessels, lymphadenopathy, neoplasia, fibrosing mediastinitis, granulomatous disease, others (histiocytosis, sarcoidosis, lymphangiomatosis)
Bronchial collapse occurs most commonly in which regions?
L cranial & R middle bronchi
Bronchial collapse occurs most commonly in which regions?
L cranial & R middle bronchi
Thoracic radiographs most sensitive for the diagnosis of airway collapse in which regions of the lungs?
Sn for the detection of bronchoscopically identified collapse was highest for radiography at the trachea, left lobar bronchi & right middle bronchus. But relatively low Sp.
What clinical sign can epiglottic entrapment of the soft palate cause?
Reverse sneezing
How to calculate estimated systolic PA pressure from echo?
Measure TRV max
Modified Bernoulli equation:
Pressure gradient (aka estimated systolic PAP) = 4 x (TRVmax)^2 in mmHg
ACVIM consensus panel’s definition (cut-offs) for pulmonary hypertension in dogs?
TR PG cut-off of >46 mmHg (TRVmax >3.4 m/s)
Defined as moderate PH historically
Specific treatment for PH targets which 3 pathways?
ACVIM consensus.
NO, endothelin & prostacyclin pathways
These mediate pulmonary arterial/arteriolar vasoconstriction (secondary to endothelial injury).
What is a rare disease to be suspected if a dog with pulmonary hypertension develops pulmonary oedema after sildanefil treatment? How does this occur?
ACVIM consensus
Pulmonary veno-occlusive disease or pulmonary capillary hemangiomatosis.
Also caution when administering PDE5-i in dogs with LHD & congenital shunts.
Reactive” or “responsive” pulmonary arteries (or arterioles) have an unpredictable response to tx. Increased right sided CO, acutely increases pulmonary VR to the LA»_space; subsequently increase LA & thus pulmonary venous and capillary pressures»_space; pulmonary oedema.
What anti-neoplastic drug may be considered as an adjunct treatment for refractory PH in dogs & MOA? What evidence is there to support its efficacy?
ACVIM consensus
TKIs (e.g. toceranib, imatinib) - cause PA vasodilation by inhibiting action of PDGF (by inhibiting phosphorylation of PDGF-receptor TK). Used in people, little data in dogs, but imatinib reduced PAP in dogs with PH 2’ to LHD in 1 study.
Define the 2 kinds of gas transfer, and list examples of gases under these classifications.
Diffusion limited: gas transfer is limited by the diffusion properties of the blood gas barrier. E.g. CO (binds with high affinity to Hb, pp doesn’t change in blood)
Perfusion limited: gas transfer limited by capillary blood flow. E.g. NO, CO2 (diffusion stops when capillary & alveolar P equilibrate). NB CO2 has 20x solubility in blood vs O2.
O2 is in between. Normally perfusion limited; when blood-gas barrier thickened > becomes diffusion limited.
(T/F) Hypoxic pulmonary vasoconstriction occurs as a local response secondary to changes in arterial PO2.
False. True as local response, but determined by alveolar PO2 (occurs regardless of PaO2 value)
(T/F) Hypoxic pulmonary vasoconstriction occurs as a local response secondary to changes in arterial PO2.
False. True as local response, but determined by alveolar PO2 (occurs regardless of PaO2 value). Marked vasoconstriction when PAO2 <70mmHg.
Which of the following causes of hypoxemia result in an increased A-a gradient?
- V/Q mismatch
- Diffusion limitation
- Shunt
- Hypoventilation
All except hypoventilation (A-a gradient is normal i.e. PaO2 = PAO2 +/- 10mmHg)
(Causes of hypoventilation = airway obstruction, decreased ventilatory muscle function e.g. GA, CNS disease, polyneuro/myopathy, NMJ dz, fatigue), chest wall/pleural space dz, COPD
One of the main regulators of ventilation involves the effect of PaCO2 on……
CSF pH (CO2 diffuses across BBB > H+ + HCO3-, where H+ is a potent stimulator of central chemoreceptors in the chemosensitive area in the medulla > inspiration)
NB: CO2 is the most potent (indirect) stimulator of CSF pH (not H+ directly)
Increased PaCO2 –> cerebral vasodilation –> increased ICP
What % of dogs with laryngeal paralysis are diagnosed with hypothyroidism? Does thyroxine supplementation help to improve clinical signs of lar par?
30% (but no direct association proven).
No.
What treatments are available for treatment of nasopharyngeal stenosis in dogs/cats? Recurrence and complication rates?
Berent VCNA review
1. Balloon dilation + topical mitomycin C 0.1% OR triamcinolone submucosal inj:
- Cats - 50% success (typically thinner, patent, caudal NP). Dogs - 30% with single dilation, 40% with up to 3 procedures.
2. Metallic stent placement (covered vs uncovered)
3. Temporary silicone tubing after stenosis dilation.
Complications
Stenosis recurrence - >70% (esp with BD alone)
Tissue ingrowth - most common, esp in balloon dilation cases (60-70%), least in covered metallic stent cases (0%)
Oronasal fistula - middle NP stenosis, related to stent mvt
Cats overall better success (87%) vs dogs (60%) - can be imperforate
Define hypoxemia and list the 5 causes of it?
PaO2 <80mmHg (severe <60mmHg).
Low FiO2, global hypoventilation, R-L shunt, diffusion impairment, V/Q mismatch (most common)
What drug can cause neutrophilic-eosinophilic lower airway disease in cats?
KBr
What is a normal A-a gradient?
Equations to calculate A-a gradient?
PAO2 = 150 - PaCO2 / 0.8
A-a gradient = PAO2 - PaO2
Normal <10, >15-20 = abnormal –> diffusion impairment.
(NB brachys have higher A-a gradient)
(Assume Patm = 760mmHg, a water vapor of 47mmHg, FiO2 0.21) R (respiratory quotient) = 0.8
What are the 3 complications of oxygen therapy?
- O2 toxicity: prolonged exposure to high O2 concentrations (e.g. 100% O2 for >12hrs). Toxic effects are due to the formation of O2-derived free radical species, which induce endothelial and epithelial cell damage, increase endothelial permeability, and ultimately cause inflammation and alveolar damage.
- Absorption atelectasis: high concentrations of O2 being delivered to the alveoli result in a washout of the nitrogen support skeleton, resulting in alveolar collapse.
- Hypoventilation: O2 replaces CO2 as the main respiratory stimulus in patients with COPD/brachys. O2 supp can decrease respiratory drive & result in significant hypoventilation.
What are the adverse effects of using albuterol chronically in asthmatic cats?
Inhalant albuterol is a racemic mixture consisting of the R-enantiomer (possesses bronchodilatory properties) & S-enantiomer (promotes bronchospasm and inflammation). With chronic/repeated use, S-enantiomer preferentially accumulates in the lung because of slower metabolism/clearance, enhancing bronchoconstrictive and proinflammatory effects.
What is a distinguishing feature between feline asthma & chronic bronchitis which can be demonstrated using barometric whole body plethysmography (BWBP)?
Airway hyperresponsiveness (bronchoconstriction) is more prominent with feline asthma at lower bronchoprovocant doses.
List some metabolic functions of the lungs (i.e. secretion/inactivation of which substances)?
Activates AT-I to AT-II (via ACE enzyme)
Metabolizes & releases arachidonic acid (via phospholipase A2 = component of surfactant)
Secretes IgA into the bronchial mucus (mucosal immunity)
Secretes mast cells (containing heparin)
Inactivates NE (up to 30% removed)
Inactivates bradykinin (up to 80% inactivated via ACE)
Inactivates serotonin (via uptake and storage)
Releases + inactivates PGE1/E2/F2α, leukotrienes
- Leukotrienes (via lipoxygenase) – inflammatory responses.
- PGs – vasoconstrict/dilate, platelet aggregation, clotting and bronchoconstriction
The ratio of total systemic vascular resistance to pulmonary vascular resistance is about …..
10:1
Factors that shift the O2Hb dissociation curve to the LEFT?
Causes that decrease O2 unloading to tissues.
- Increased pH = alkalosis
- Decreased temperature
- Decreased pCO2
- Decreased 2,3 DPG (stored blood)
- CO poisoning
What is the Bohr effect?
Refers to the O2Hb dissociation curve shifting RIGHT & downward in response to increased CO2 > increased H+
- Curve changes > reduces O2 binding affinity of Hb > increased O2 delivery to tissues
List 4 parasites that can be detected using the faecal Baermann sedimentation test (which stage), spp affected, and their predilection sites?
- Aelurostrongylus abstrusus - cat lungworm. L1 larvae. Terminal bronchioles, alveolar ducts.
- Strongyloides stercoralis (threadworm) – dogs. SI.
- Crenosoma vulpis – dogs. Canine fox lungworm. Bronchioles. (Canada)
- Angiostrongylus vasorum (French HW) – dogs. PA, R heart. Pulm hypertension Similar appearance to cat lungworm.
List dog breeds affected by congenital laryngeal paralysis, and the mode of inheritance if known?
- Bouvier des Flandres (autosomal dominant)
- Siberian huskies, Alaskan malamutes & X-es (autosomal recessive)
- White coated GSDs (Wallerian degeneration of recurrent laryngeal n.; central loss of motor neurons innvervating the muscles of soft palate/laryngx/pharynx/upper O)
- Dalmatians, Rotties: suspected hereditary LP-polyneuropathy syndrome (megaO, ataxia, poor px)
What is Kartagener’s syndrome and what disease is it associated with? List 3 breeds affected and what is the causal gene mutation?
Dysfunction of the monocilia of the embryonic node might also lead to the randomization of the left‐right body asymmetry & transposition of the thoracic and abdominal organs such that left-sided structures are found on the right and vice versa). Associated with primary ciliary dyskinesia (50% dogs)
Old English Sheepdog, Bobtail, Border Collies
CCDC39 point mutation, autosomal recessive.
List parasitic causes of pneumonia in cats?
- Aelurostrongylus abstrusus
- Troglostrongylus brevior
- Eucoleus aerophilus (formerly Capillaria aerophilia)
- Dirofilaria immitis (feline heartworm)
- Toxocara cati
- Paragonimus kellicotti (lung fluke)
Which infectious agent may cause nodular changes in bronchioles of dogs? Where does this organism predominantly reside?
Oslerus osleri
Carina, mainstem bronchi
Which lung lobes are most commonly affected by bronchial collapse? Which conditions is this most commonly associated with?
Left cranial & R middle.
Tracheal collapse (60% dogs), BOAS (87% dogs have L cranial lobar bronchial collapse esp Pugs)
What are the limitations of radiographs in planning for tracheal tstent placement?
TC noted at the incorrect location in 44% of dogs, missed in 8% of dogs.
Underestimate tracheal size measurements
Underestimate presence and/or severity of lower airway dz
What intervention is indicated for extrathoracic/cervical tracheal collapse? What is a major complication & additional procedure that improves outcome?
Extraluminal tracheal ring placement.
Lar par - 31-56% dogs at some stage post-op; 11-12% in immediate post-op period, smaller % late stage due to long-term rubbing, granulation tissue formation or contact with a prosthesis.
Concurrent left arytenoid lateralisation + ring placement reported, sig reduced post-op complication rate (to 4%) with 75% dogs having good long term outcome.
Angiostrongylus vasorum - state:
- Hosts (intermediate, reservoir, paratenic)
- Life cycle (brief summary)
- Clinical manifestations
- Diagnostics
- Tx
AKA canine french HW.
- Molluscs (snail, slugs) = IH, frogs = paratenic host, Red foxes = reservoir host.
- Dogs shed L1 in faeces. L1-L3 in IHs. L3 (immature larve) is infective stage - ingested by dogs > released in GIT & migrates to liver > veins > R heart –> L3 to adult in R heart & PAs > shed eggs which travel to pulm capillaries (lungs) –> eggs hatch to L1 which migrate to alveoli –> L1 coughed up & swallowed > shed in faeces
Clin path: subclinical poss. Pulm hypertension, coagulopathies, CNS signs (hemorrhage), V+, ascites, syncope, anemia, eosinophilia, thrombocytopenia, coag abnormalities, hyperCa.
Dx:
- L1 in BAL cytology or faecal Baermann.
- Ag (Angiodetect IDEXX POC test or ELISA). False neg <5wks PI.
- Ab (against adult): ELISA. + result = exposure vs early infx (<5wks PI).
– PCR (faeces/lungs) - more Sn, can differentiate from A. cantonensis & costaricensis. qPCR on BALF higher Sn vs Ag.
Tx
FBZ, milbemycin, moxidectin top, abamectin SQ. MLs for prevention.
What is the utility of the following markers for the diagnosis of respiratory diseases in dogs:
- Endothelin-1
- PIIINP (Procollagen type III amino-terminal propeptide)
Serum ET-1 can differentiate **IPF dogs **from EBP or CB dogs. Cut-off of 1.8 pg/mL had 100% Sn & 81.2% Sp for detection of IPF.
Serum/BALF PIIINP = marker of collagen type III synthesis. Increased in EBP (upregulated collagenolysis) & IPF
NB: Other markers for IPF - IL-8, chemokine (C-C) ligand 2 (higher at dx = neg px for survival), BALF TGF-beta (mediator of fibrosis
Pulmonary surfactant
- Components
- Site of production
- Roles
Dipalmitoyl phosphatidylcholine (DPPC) (main component), phospholipid, Ca2+, apoproteins
Type II alveolar epithelial cells
Reduce surface tension, increase lung compliance, prevents alveolar collapse, keeps alveolar dry
How may assessment of tidal breathing flow-volume loops (TBFVL) help to differentiate dogs with tracheal collapse cf healthy dogs? What changes are expected with TC?
Assessment of inspiratory time (TI), expiratory time (TE), inspiratory flow (PIF) & expiratory flow (PEF) rates
Flattening of inspiratory phase/plateau.
