Chapter 103 Lungs Flashcards
How many paris of ribs do dogs and cats have and how may sternebrae?
13 pair of ribs and 8 sternebrae
List the subdivisions of bronchi, from mainstem bronchus –> alveloi
- Two principal bronchi
- Lobar bronchi that supply each lung lobe
- Segmental bronchi that supply bronchopulmonary segments.
- Dichotomous branching of the airway continues through subsegmental bronchi, terminal bronchioles, and respiratory bronchioles. Respiratory bronchioles give rise to alveolar ducts, alveolar sacs, and pulmonary alveoli.
Along which aspect of bronchi do arteries run? Where is oxygenated supple received from?
Arteires run cranial and dorsal (veins caudal/ventral).
Bronchooesophageal arteries supply oxygenated blood
Name the principla mechanisms responsible for normal inspiration and expiration?
Inspration due to diaphragmatic contraction, expiration due to elastic recoil
List 4 muscles that assist with inspiration when necessary
And expiration?
Inspiration
- External intercostal muscles
- Scalenus
- Serratus ventralis
- Sternocleidomastoid
Expiration
- Internal intercostals
- Rectus abdominis
Define elastance and compliance
- Elastance* (recoil) degree to which lung can return to its dimensions after removal of distending forces. Pressure change required to elicit a unit volume change (ΔP/ΔV)
- Compliance* measure of lung distensibility (reciprocal of elastance) (ΔV/ΔP). Can be estimated from pressure-volume loops (steeper slope = greater compliance). Normally lung compliance os lowest at high and low volumes.
What type of cells secrete surfactant?
Type 2 alveolar cells
What is normal PaO2?
What is considered hypoxaemic?
>90 mmHg (N.B. should be approx x5 Fi oxygen)
<80 mmHg moderate hypoxaemia
<60 mmHg severe hypoxaemia (approx SpO2 of 90%)
List the percentage contribution of nares/nasal, larynx and small airways to inpiration.
And to expiration
Inspiration
Nares 79%
Larynx 6%
Small airways 15%
Expiration:
Nasal 74%
Larynx 3%
Small airways 23%
What are the most important regulators of ventilation?
Chemoreceptors (central in medulla of brain) and carotic and aortic bodies (peripheral. Usually have more rapid but smaller magnitude of response)
Change in ventilation has the greatest response to PaCO2 (as opposed to PaO2 or pH), but if PaO2 falls below 60 mmHg ventilation increases - what is the name of this response?
Hypoxic ventilation drive
What is typical canine and feline tidal volume?
10 ml/kg
What does Fick’s law state?
Fick’s law states that rate of transfer of a gas through a sheet of tissue is proportional to surface area available for diffusion, diffusion coefficient of the gas, and difference in gas partial pressure between the two sides and inversely proportional to the tissue thickness (distance the gas must travel).
What id the approx surface area of the lungs?
An thickness of at blood-gas interface?
At the blood-gas interface, the lungs have a surface area of 50 to 100 m2
0.3-µm thickness
How does the diffusion coefficient of CO2 differ from O2?
The diffusion coefficient of CO2 is 20 times greater than that of oxygen; CO2 therefore diffuses more rapidly
i.e. if limited space for diffusion and diffusion distance inreased, hypoxaemia can occur before evidence of hypercapnia
What is the formula for amount of dissolved oxygen in plasma?
0.003 x PaO2 (ml O2/100 mL blood)
What proportion of oxygen delivered to tissues is protein bound?
What are the two types of haemoglobin?
98.5%
Ferrous haemoglobin
Ferric haemoglobin aka methaemoglobin (has no affinity for O2)
How much oxygen can one gram of Hb combine with?
1g of Hb can combine with 1.39 mL of oxygen
(Normal blood has approximately 15g Hb /100 mL blood)
What 5 factors shift the oxygen-haemoglobin dissociation curve to the right? (i.e. decreased affinity)
“CADET, look right”
C - carbon dioxide
A - Acidosis
D - 2,3 DPG
E - Excercise
T - Temperature
What is the formula for arterial oxygen content (CaO2)?
CaO2 = (1.36 x HB x %O2Sat/100) + (0.003 x PaO2)
N.B. Final until is mL oxygen/100 mL blood
Carbon dioxide transport in RBCs is mainly transported in three forms - what are they and what % does each make up?
What proportion is dissolved in plasma
63% as bicarb (carbonic anhydrase transforms carbonic acid into bicarb and H+)
21% in combination with proteins (carbamino coponds)
5% dissolved in RBC
11% dissolved in plasma
List a cause of high V/Q and low V/Q
(V = ventilation, Q = perfusion)
High V/Q: PTE
Low V/Q: Oedema, pneumonia
List 5 causes of hypoxaemia
- Hypoventilation
- Low inspired O2
- Diffusion impairment (fibrosis, early oedema)
- V/Q mismatch
- Shunting (e.g. r to l heart shunt)
What can be used to determine whether a V/Q mismatch is present?
What is the formula?
And the simplified version?
A (Alveolar)-a(arterial) gradient
Alveolar pressure of O2 (PAO2) should more or less equal arterial pressure of O2 (PaO2).
PA-a O2 should be <10 mmHg.
>20 warrants oxygen supplementatio
>30 considered severe gas exchange impairment
A-a gradient formula:
[FIO2 x (Pbarometric - PH20)] - (1.2 x PaCO2) - PaO2
Simplified if room air and sea level
150 - (1.2xPaCO2) - PaO2
What is the difference betweena bulla vs a bleb?
How can a bulla/bleb be differentiated from a cyst?
Bulla in parenchyma, bleb between visceral pleura and parenchyma
Cyst has respiratory epithelial lining
What is the sensitivity of CT for diagnosing cause of spontaneous pneumothorax?
42-58%
What is the recommended contrast medium for bronchooesophageal fistula and why?
Non-ionic iodine agent as low tissue reactivity.
What 4 bacteria are most commonly isolated form canine pyothorax?
And additional ones isolated in cats?
E coli, Klebsiella pneumoniae, Staph, Strep, Pseudomonas, Fusobacterium
Nocardia and Corynebacterium
List 3 CT features of bronchiectasis
What was the MST for dogs treated for bronchiectasis?
Airway dilation, lack of tapering, lobar consolidation
MST 16 months
What % of torsed lungs appear emphysematous radiographically?
What is reported survival rate in tobias for lung lobe torsion?
And recent papers?
97%
50-60% survival in tobias
90-95% survival in recent papers
List 4 primary lung tumours
What are prognostic factprs in dogs?
And in cats?
- Bronchial/alveolar carcinoma
- SCC
- Histiocytic sarcoma
- Anaplastic tumours
Prognostic factors:
Dogs
- Histologic cell type
- Size <5cm
- Metastasis
- Pleural effusion
- Clinical signs
MST 400-550d if no clinical signs/no LN involvement, vs 26 - 200 if LN involvement/clinical signs (respectively)
Cats
- Degree of differentiation
What si the open and closed height of TAV3 staples?
Open height 2.5mm, closed 1mm (3 rows as opposed to 2 with other TA staples)
What anaestehtic technique can be used to facilitate thoracoscopic lung lobectomy?
One lung ventilation
recommend open if mass >8cm or dog <10kg.
What percentage of lung mass do right vs L lung represent?
R lung = 58%, L lung = 42%
Experimentally dogs tolerates acute loss of 505 lung volume but die after 75% loss. Tobias says likely to die if acute R pneumonectomy.
Acute restriction of >60% pulmonary artery outflow if fatal as can induce acute pulmonary hypertension.
