Approach to LRT Disease in SA

Question 1

What is the structure of the mammalian airway?

Answer 1

•Airways of the mammalian lung consists of a branching tree of blind ending tubes.

This design creates physiological problems.

•Mammalian lung contains two types of airways:

• Conducting - carry air to and from respiratory airways.
• Respiratory - responsible for gaseous exchange with blood.
• ‘inverted’ tree – gaseous exchange at pulmonary parenchyma
• Disease gets worse when its higher up – e.g. worse to have a tracheal occlusion rather than part of an alveoli of the left lobe for example
• Cyanosis is difficult to generate with lung disease – if cyantoci with lung disease, a LOT of the lung is abnormal but can get quite cyanotic quite quickly with laryngeal disease

Question 2

How do we approach animals with lower airway disease?

Answer 2

•Signalment (age, breed, sex, neuter status)

–Important for breed related disorders and helping to organise your differentials list

•Full and thorough clinical history

–Including:

• Diet, drinking, eating, urination, defecation, fluctuations in body weight
• Abnormal clinical signs at home/outside
• Any changes in activity level at home
• Any changes in personality / behaviour
• Changes in voice – laryngeal lesions – any change with bark or meow – rarely asked! If you don’t ask, you don’t know
• Facial deformity

Question 3

How should I approach this LRT case in the consulting room?

Answer 3

•Observe the patient closely

–First critical aspect is whether the patient requires emergency admission or appears clinically stable – what are they doing at rest?

•A significant number animals with lower airway disease will be presented for acute deterioration

–Condition of patient

–Breathing character

•rate, pattern, regularity, depth and apparent effort

–Mucus membrane colour

• Pale, cyanotic, normal
• Some animals that are anaemic will look like they have resp disease to compensate for lower oxygen
• Behaviours that are worrying the owner

Question 4

What breathing patterns are demonstrated?

Answer 4

• Normally inspiratory phase is longer than expiratory, in lower airway disease this is often reversed.
• Normal respiratory effort is minimal at rest
• Upper respiratory tract disease – slow respiratory rate and an exaggerated inspiratory effort (longer phase)

–Inspiratory effort increased

•Lower respiratory restrictive disease e.g. IPF, pleural effusion – fast shallow breaths

–Often both phases of breathing altered

–Interstitial fibrotic lung disease often limited to increased inspiratory effort – due to reduced lung compliance

•Pleural diseases – loss of pleural adhesion increases required effort to breathe.

–Inspiratory effort increased – lungs not stuck to body wall, so have to increase effort to expand the lungs

Question 5

What is paradoxial respiration?

Answer 5

•Paradoxical respiration – respiratory muscle fatigue leading to opposing movements of the chest and abdominal wall. e.g. inspiration the caudal ribcage collapses inward and the abdominal contents are displaced caudally. Can occur in may cases of respiratory disease but is generally a poor sign.

–May get loss of syncope between chest and abdomen

Question 6

Define:

• Tachypnoea
• Hyperpnoea
• Orthopnoea
• Trepopnoea

Answer 6

•Tachypnoea

–Increased respiratory rate

•Hyperpnoea

–Increased respiratory effort

•Orthopnoea

–Dyspnoea in any position other than standing or erect sitting – usually due to bilateral pulmonary oedema

–Abnormal breathing in a position

•Trepopnoea

–Postural abdnormalities on one side compared to other e.g. one lung may be abnormal e.g. a tumour, when they are lying in their cage after sedation for example – remember not to lie them on their good lung! Don’t put good lung underneath as they will struggle

–Dyspnoea in one lateral recumbency but not the other – unilateral lung or pleural disease, or unilateral airway obstruction e.g unilateral pleural effusion

• Often seen in patients when in hospitalised and in lateral recumbency
• Can be dramatic deterioration so always be vigilant for this

Question 7

How do I approach a thoracic examination?

Answer 7

•Thoracic palpation

–Presence of - apex beat, rhonchi, masses, deformities, pain (e.g. rib fractures)

•Thoracic auscultation

–Hindered by purring, panting, growling!

–Use both sides of your stethoscope

•Normal sounds

–Inspiratory – soft, low pitched

–Expiratory – none or softer and lower pitched

–Listen to both phases and across the chest

Question 8

What are crackles? What are the different types?

Answer 8

•Crackles – ‘sweet wrappers’ (rales) – Dry or moist

–moist – CHF and most prominent on inspiration (right hilar position 1st) – usually some resp distress. Moist crackles – low pitched, fine popping inspiratory sounds

–Dry – acute or chronic. Dry crackles – higher pitched inspiratory sounds

–All crackles usually discontinuous

Question 9

What are wheezes and rhonchi and what is the difference between them?

Answer 9

•Wheezes (high pitched) and rhonchi (low pitched):

–narrowing of airway (bronchi/trachea)

–Can be inspiration or expiration but most commonly expiration

–Wheezes and rhonchi – usually secondary to bronchial narrowing.

–These may be high or low pitched, abnormalities as there is something going wrong in the lumen

–Most commonly heard on expiration

–

Question 10

How do I examine the chest using percussion?

Answer 10

• Determine the density of a part by tapping the surface with a finger
• Best for larger dogs and cats
• Determine whether the tympanic sounds created by the chest wall are normal, increased or decreased

–e.g pleural effusion – dull below fluid line and normal above it

–There are many different causes of increased and decreased tympanic sounds on percussion

• Increased tympanic sounds – pneumothorax, feline asthma, emphysema
• Decreased tympanic sounds usually unilateral – diaphragmatic hernia, chest masses, unilateral pleural effusion

Question 11

How do I investigate the patient with lower respiratory tract disease?

Answer 11

• History – is the animal coughing or having respiratory difficulty/changed character
• Clinical examination
• Routine haematology and biochemistry

–Specific blood tests - e.g. serum Pro-BNP concentration

–Blood gas evaluation

•Diagnostic imaging

–Thoracic radiographs, fluoroscopy, CT, Ultrasound, scintigraphy, MRI

• Tracheal washes/Bronchoscopy – will it help?
• Lung FNA/biopsies – bronchoscopy may not be useful for this!
• NB these are often older dogs with concurrent disease other tests as clinically indicated!
• Recovery – its when they come around that you need to know what needs to be done, part of thorough history and where its problems are

Question 12

With lower respiratory, what laboratory testing should you have?

Answer 12

•Minimum database of biochemistry and haematology – to make sure of no limiting comorbidities

–Always of value in respiratory patients

–Determines if underlying systemic condition present/likely

• Anaemia
• Eosinophilia, neutrophilia

–Use of assays such as NT-ProBNP to determine between cardiac and respiratory causes of coughing

•Blood gas evaluation (arterial and venous)

–Enables determination of oxygenation, ventilation/perfusion mismatching and acid-base balance

–Handheld analysers available

–Hypoxaemia – PaO2 <80mmHg

–Equations for determining effective perfusion and oxygenation of blood in standard texts

–Caution as sample for PaO2 needs to be arterial and taken in the absence of air

Question 13

When are thoracic radiographs useful for LRT disease?

Answer 13

•Thoracic radiographs

–Where thoracic disease is suspected thoracic radiographs (at least 2 views) should always be taken. If just looking for significant parenchymal disease, a L and DV may ne okay but if looking for mets then probably need 3 views.

–Radiographs should only be taken when the patient is stable enough to do so!

–Severely dyspnoeic patients should be stabilised prior to radiographs in all but extremely exceptional circumstances

–Can consider horizontal beam radiographs for patients too dyspnoeic to lay down

• Aids with fluid identification and free gas
• Radiation safety issues may preclude this approach

Question 14

What advantages does thoracic CT have over radiographs?

Answer 14

• Increased sensitivity (high resolution CT: 300 micrometers)
• Spatial assessment of disease
• Value to differentiate pleural, extrapleural and mediastinal disease

Question 15

What disadvantages does thoracic CT have?

Answer 15

• Unable to perform easily in conscious patient
• Increased costs and limited availability

Question 16

What are some pros and cons of thoracic ultrasound for LRT disease?

Answer 16

–Good for looking for stuff that’s not airated

–Value for pleural disease, to identify poorly aerated lung (atelectasis, consolidation, torsion)

–No real value in normal lung tissue as US cannot pass through air

Question 17

When is transthoracic FNA useful?

Answer 17

–Ultrasound guidance in patients with discrete lesions

–Can also use fluoroscopic or CT guidance

–Lesions >1cm ideally

Question 18

What are some contraindications for transthoracic FNA for LRT disease?

Answer 18

• Pulmonary bullae or cysts
• Coagulopathies
• Pulmonary hypertension

–Increases pressure in the chest, could end up with nasty haemoarrhage

• Pre-existing pneumothorax
• Suspected infectious process

Question 19

What are some potential complications with transthoracic FNA?

Answer 19

Pneumothorax, empyema, bleeding, implantation, seeding of neoplasia – be careful with transthoracic FNAs

Question 20

Why would you perform a tracheal wash?

Answer 20

–Main indication is for patients suspected to have large airway disease

–Now recognised to provide information about the small airways as well when cough reflex retained

•Can be either trans-tracheal (TTW) or endotracheal (ETW)

–TTW benefits as cough reflex retained therefore better information from lower airways

Question 21

When is tracheal washing indicated?

Is BAL more or less sensitive?

Answer 21

• Indicated in patients that you have concerns about anaesthetizing – wont be able to do bronchoscopy in a patient that is awake
• Is less sensitive than BAL but is easier to perform and can be carried out in the conscious patient.
• Both try to obtain information from lower airways

Question 22

Describe how to perform a tracheal wash?

Answer 22

• Catheter required – usually through the needle type but any can be used.
• Need to have sufficient diameter needle to pass catheter through
• Different lengths of catheter, longer in a large dog
• Different lengths for different sizes of animals – cats and small dogs 19-22g 8inch
• Larger dogs may use 19g12 or 24 inch catheter
• Clip and pre area around larynx and ventral neck
• Feel for laryngeal cartilages as landmarks
• Surgically prepare area
• Infiltrate with local anaesthetic to facilitate easy passage of needle and catheter
• If patient not cooperative – can sedate – important to retain cough reflex though – pure opiods as can reverse once catheter in place or ketamine/BDZ as retains cough reflex
• 2 points of entry – through cricothyroid ligament triangular depression at base of thydoi cartilage or between tracheal rings (preferable as less sensitive to animal)
• Placement of catheter (over the needle type with stylet removed)
• Use sterile saline as wash fluid
• Wash is then attached to catheter and steadily instilled. Coupage is performed following introduction and
• Volumes around 3-5ml for cats and small dogs
• For large dogs 10-20ml sufficient
• Immediately begin steadily suction on catheter
• Only small volume of fluid usually retrieved
• Care with active suction devices as these can damage airway and cells

Question 23

What are the indications for bronchoscopy?

Answer 23

• Investigation of unexplained clinical signs
• To obtain diagnostic samples of something we can see or something with chronic cough and there may be inflammation or something else
• Evaluate radiographic lung lesions
• Assessment of airways
• Treatment of airway disease
• Bronchoscopy usually follows H, PE, radiographs, bloods, ? Therapeutic trials have failed to give an answer for the LRT disease
• Chronic cough, haemoptysis, acute / chronic resp distress
• Animals unlikely to benefit are those with primary disease of the vasculature and those with discrete pulmonary lesion

Question 24

What are the benefits of bronchoscopy?

Answer 24

• Relatively safe procedure
• Diagnostic for a number of conditions
• Allows collection of samples
• Allows removal of foreign material
• Obtain material for bacteriology, mycoplasma, cytology, bronchial brushes, transbronchial biospy / brushings
• Assesment of airways – tracheal / bronchial tears, trachealbronchial, or bronchialoesophgeal fistulas, lung lobe torsion, tracheal / bronchial collapse
• Assessment of airway injury – noxious gases, aspiration pneumonia
• Removal of FB, suction aspirated material, removal of viscous substances – mucus plugs in some cases aid diff intubation.

Question 25

What are the contraindications of bronchoscopy?

Answer 25

•Care with hyper-responsive airways –e.g. cats with allergic bronchial disease –Dogs with wheezing suggesting airway spasm - Be careful if animal has a wheeze before hand, increased risk of spasm * Unstable cardiac failure / arrhythmias * Care in those patient with tracheal obstruction * Haemorrhage – increased risk with: –Pulmonary hypertension –Uraemia –Coagulopathies –Neoplasia/gross lesions

Question 26

How do we perform bronchoscopy?

Answer 26

•Sterilisation - according to manufacturers recommendations –If unusual / repeated bacteria isolated swab scope –Could misinterpret results if scope not clean •Care of scope – very delicate –Fibreoptic or video •Under GA as prevents scope damage –Airway diameter vs scope diameter important –Not the same therefore as humans or horses * Sternal recumbency with head elevated generally * Elevate head so nose is parallel to the table * Specialised brushes to brush scope and ports * Ideally hand scopes up or in case – do not bend in sharp corners / drop etc * Sternal recumbency * Can shorten ET tube so can visualise more of the trachea * Y or T shaped adaptor – attached to end of ET tube to allow passage of O2 and anaesthetic gas during the procedure * IMPPORTANT THAT DISEASE MAY BE IN TRACHEA OBSCURED BY ET TUBE SO REMOVE AND SCOPE THIS AREA * Sterile, large ET tube * Y connector / T connector * Adaptor self sealing port * Lubricate scope as necessary - sterile lube required * Watch ventilation

Question 27

How can you collect samples with bronchoscopy?

Answer 27

–Saline lavage – bronchoalveolar lavage (BAL) –Surface brushing (cytology brush) –Biopsies – care with technique

Question 28

How are samples from bronchoscopy submitted?

Answer 28

–Culture – bacterial/mycoplasmal/fungal –Viral isolation –PCR for infectious organisms e.g. mycoplasma –Cytology

Question 29

What is the equipment required for a Bronchoalveolar Lavage (BAL)?

Answer 29

* BAL for lobar or diffuse lower airway disease or interstitial lung diseases * 0.9% sterile saline solution * Bacterial swabs * Sterile plain tubes (plastic) * EDTA tubes * BAL catheter * Urinary catheter if not able to do a normal BAL, tip snipped off * Continuous suction device to retrieve saline * Syringes * An assistant! * Formalin if you want to take a biopsy

Question 30

What is the technique to do a BAL?

Answer 30

* Pre-oxygenate – 2 minutes in compromised patients * Lodge endoscope in small airway, get it down as far as you can. Tying to block off one tube, pass catheter and saline down and wash it around and then take it back out… * Instil sterile saline via catheter –Volume not been established various amounts depending on author/clinician preference –For medium to large dogs ~25ml per lobe (2 lobes washed) –For small dogs and cats ~10ml per bolus (up to 4 sites) * Immediate suction after instillation of fluid * If too much suction then causes airway collapse and damage (100-170mmHg pressure max) –Care with suction chambers as more likely to damage cell morphology •Repeat boluses in same position –First bolus has largest amount of material from large airways * If negative pressure is obtained rather then fluid, less suction to stop airways collapsing if still no joy then withdraw endoscope and then reapply less suction. If withdraw too far then no longer sung fit and will not obtain a good sample. * Airway collapse most common problem in dogs with chronic airway inflammation (bronchitis) * Lavage several lobes * Coupage whilst fluid is being instilled * Good quality sample * Foam on top – due to surfactant in fluid * \>50% of fluid retrieved * In one study mean volume retrieved was 48% 1 * Retrieval volume should increase with each subsequent lavage

Question 31

How do we manage patients post-BAL?

Answer 31

* 100% Oxygen for 5-10 minutes * Gentle positive pressure ventilation –May aid with opening of atelctatic alveoli •If previous stable patient does not respond to oxygen consider: –Obstruction of ET tube –Bronchospasm - bronchodilator –Pneumothorax * Normal to auscultate crackles for up to 24 hours post BAL * PPV helps open up airways where alveoli have collapsed * isotonic saline is reabsorbed quickly from alveoli

Question 32

Are URT and large airways sterile?

Answer 32

•URT and large airways are not sterile –have commensal bacteria –Numbers are increased in dogs with reduced clearance

Question 33

What different bacterial cultures can you have with a BAL?

Answer 33

•URT and large airways are not sterile –have commensal bacteria –Numbers are increased in dogs with reduced clearance •Quantitative culture – –rarely performed in veterinary medicine, can be requested •Evidence of infection –Intra-cellular bacteria – is it something we can see on the slide at the time? –Growth from BAL fluid –Neutrophilic inflammation on cytology * Chronic bronchitis, bronchiectasis, ciliary dyskinesia * BUT problem cases those with, neutrophilic inflam, no IC bacteria, culture from BAL only with enrichment in low numbers * ? True infection, low bacterial count due to dilution, previous a/b therapy or not true infection

Question 34

What are some problems with diagnosing bacterial infection with the LRT and BAL?

Answer 34

* Veterinary medicine BAL often not performed until after antibiotic therapy has not resolved clinical signs * Antibiotics persist in lung in sufficient quantities for at least 7 days or longer * Also risk of contamination from URT * Trying to do diagnostics on something on antibiotics – you underestimate the severity as the Abs can carry on being present in airway for up to a week * Can pull down contaminants from URT to LRT

Question 35

What are some treatments for Lower airway disease?

Answer 35

•Inhaled medications –Corticosteroids –Bronchodilators –nebulisers •Oral therapy –Anti-inflammatories •Corticosteroids, NSAIDs, anti-leukotrienes –Bronchodilators * Terbutaline * Theophylline –Antibiotics, anthelminthics –Mucolytics – N-acetyl cysteine (NAC)

Question 36

How do we deliver inhaled medications?

Answer 36

* Mask * Spacing device/chamber * Metered dose inhaler (MDI) * For most effective use of an MDI requires inhalation to be purposely coordinated with actuation of the device. In children and animals this is not possible, therefore use spacing device which allows MDI to be used without the need to coordinated their breathing pattern. * Spacing device contains the aerosol so it can be inhaled by the animal

Question 37

What is the value of inhaled medications?

Answer 37

* Management of chronic airway disease * Minimal absorption into systemic circulation –Less systemic side effects – particularly steroids •Faster onset of action

Question 38

What are some drugs that may be delivered by inhalation?

Answer 38

•Beta 2 agonist –Salbutamol (albuterol in USA) –Salmeterol – longer acting medication •Corticosteroids –Fluticasone - most common –Beclomethasone •Inhibition of mast cell degranulation –(unclear efficacy in dogs and cats with airway disease) –Cromolyn sodium/sodium cromoglicate

Question 39

Name an inhaled bronchodilators?

Answer 39

•Salbutamol (ventolin) –Beta 2 agonist –Fast onset of action –Lasts \>3hrs –Cleared renally and metabolism –10-20% inhaled reaches lower airways –SE: tachycardia, arrhythmias, tremors –Absorbed from lower airways into the pulmonary tissue and circulation, then metabolised by liver or excreted in urine as drug. Rest of drug deposited in orophaynx as is swallowed. Absorbed by GIT and high first passs metabolism

Question 40

Name some inhaled glucocorticoids

Answer 40

•Fluticasone propionate –Flixotide (trade name) in UK •Slowly absorbed from lung –Long dwell time in lungs –High potency first pass metabolism steroid •Rapid first pass metabolism in liver –Less systemic side effects * Long half life * Least bioavailable – but doesn’t matter as it gets into lung and stays there for a while * Side effects –Oral infections e.g. candidiasis, coughing, wheezing – if owner tells you there is coughing or wheezing, can be a mild SE but this may be more tolerable than the original problem! –Side effects oral thrush, coughing and wheezing (minimized with concurrent use of bronchodilator), using space and washing mouth afterwards reduces risk.

Question 41

Why are inhaled medications valuable?

Answer 41

* Reduces systemic exposure to GC * Dose of GC required is lower * Reduces systemic side effects * Effective in acute situations –Acute respiratory distress – beta agonists –Evidence for efficacy * Humans – extensive evidence * Veterinary – increasing evidence

Question 42

What are some disadvantages of inhaled medications?

Answer 42

* Expensive * Time consuming * Owner compliance * Patient compliance * Would recommend prior to using inhalers therapeutically that animals are allowed to become accustomed to device * Bring to face and remove on and off before making breathe in * Dispense medication into chamber before apply to face * Spray often puts animals off and may therefore prevent this method being used long ter

Question 43

What are the benefits of glucocorticoids on the airway?

Answer 43

* Broncho-dilatory * Anti-inflammatory * Inhibit both prostaglandin & leukotriene synthesis * Potentiate beta-2 adrenergic activity * Reduce leukocyte accumulation * Reverse increased vascular permeability * Alter macrophage function * Inhibit fibroblast growth * Modulate the immune system * BUT adverse side effects – thus dose limitin

Question 44

What are the benefits of Bronchodilators on the airway?

Answer 44

* Reduce spasm of lower airways * Decrease intrathoracic pressures * Decrease tendency of larger airways to collapse * Improve diaphragmatic function * Improves muco-ciliary clearance * Inhibit mast cell degranulation (reduced release of mediators of bronchoconstriction) * Possible additional ways that signs are improved: * Improves pulmonary circulation * Improves cardiac function * Reducing respiratory effort

Question 45

When are antibiotics indicated with LRT diseases?

Answer 45

•Most chronic bronchitis cases do not have bacterial infection as a causal agent –If there is secondary infection requires immediate therapy due to compromised resistance mechanisms •Antibiotics indicated if C&S results +ve, or if intracellular bacteria seen on BAL cytology –Empirical treatment then initiated prior to culture results –Care if using fluoroquinolones with theophylline as they inhibit metabolism increase concentration of theophylline – risks toxicity

Question 46

When are mucolytics useful? Name some

Answer 46

•Can be useful to help reduce mucus accumulation in chronic bronchitis and other conditions with compromised muco-ciliary clearance –Bromohexine – increases lysosyme activity and IgA concentration in experimental studies •Licensed product - bisolvon –NAC – Effective at breaking mucin disulphide bonds * no current published efficacy data * Anecdotal evidence some evidence for efficacy when administered orally between 125-600mg B-TID PO * Cannot be nebulised as causes bronchospasm

Question 47

When are antibiotics useful for respiratory tract disease?

Answer 47

* Antibiotic selection should ideally be based on C&S * Require high concentration in the lungs * Need to penetrate, dissolve in blood-bronchus barrier * Lipophilic antibiotics penetrate this best * Needs to be effective against respiratory pathogens * Ideally a/b should be bacteriocidal * May need to select combination a/b e.g. complex pneumonia/mixed infection * Ensure adequate treatment period at least 4-6 weeks for severe/chronic infections * Primary infection is uncommon in dogs * Secondary respiratory tract infections common * in chronic bronchitis, compromised mucociliary clearance * Essentially – remember, do we have an infection? Use cytology. Do we have a drug that is effective for this bug? Based on C&S. then, do we have an antibiotic that its sensitive to, that gets into the respiratory tract! Some Abs don’t penetrate very well and some that do, don’t always kill the bug

Question 48

How do we decide which antibiotics we need for respiratory tract disease?

Answer 48

•Good airway penetration –Drugs reach airway by passive diffusion –Favourable characteristics * Lipophilicity and low Mr * Few drugs reach same conc as plasma * Depends on nature of organism –Mycoplasma inherently resistant to certain antibiotics as no cell wall – choices include macrolides and fluoroquinolones, can consider tetracyclines •No current evidence that inhaled antibiotics have any efficacy and so oral medication always required –However may have a role to play in B. Bordetella infections * Fluoroquinolones are concentrated significantly in canine alveolar macrophages good penetration into airway * Macrolides are reasonably well concentrated into respiratory tract –Azithromycin very good distribution into pulmonary tissues –Metronidazole accumulates well in bronchial secretions –Drugs with long half life accumulate in secretions – e.g. doxycycline * Lincosamides – accumulate well in phagocytes * Penicillins have relatively poor distribution into bronchial tissue –Some are better than others e.g. amoxicillin \> ampicillin * Cephalosporins – variable penetration depending on generation although better than penicillins * Tetracyclines – reasonable concentration in secretions relative to plasma