Certificate In Anatomy And Physiology
Panting in dogs is a normal mechanism to assist with cooling, it allows increased evaporation of mucosal secretions in the oral cavity and increasing of dead space ventilation within large airways which aids in reducing temperature. Panting can be seen in warm/hot/humid weather and after vigorous exercising. Panting can also be a response to stimulation of thesympathetic nervous system related to anxiety, also with heart, respiratory or endocrine disorders.
Symptoms of dogs presenting in respiratory distress or dyspnoea (difficulty breathing) include: tachypnoea (rapid respirations) and tachycardia (rapid pulse), orthopnea (positioning upright required to assist respiration), increased respiratory effort including open mouth breathing and increased abdominal muscle effort, respiratory sounds, injected mucous membranes (bright red mucous membranes due to vasodilation, hyperthermia), pale mucous membranes (due to anemia or vasoconstriction), cyanotic mucous membranes due to poor perfusion (hypoxemia) but the mucous membranes may also be pink, petechia indicating coagulation problems such as DIC as a result of heatstroke, lethargy, decreased CRT due to hypo perfusion or increased CRT due to vasodilation as in sepsis and hyperthermia and lethargy due to increased respiratory energy requirement or pathophysiology of the condition.
Signs of orthopnea in dogs includes elevated and extended neck, abduction of the thoracic limbs (splay elbows away from midline), typically standing, sit or sternal recumbency to assist minimising airflow resistance and aid with chest wall expansion.
Using a stethoscope to listen to chest sounds is called auscultation. The sounds vary with respiratory volume, velocity of airflow, presence of fluid or air or lung parenchyma disease. Respiratory sounds you may hear in a dog with upper respiratory presentation can include stertor which is a snoring type noise on inspiration/expiration indicating upper airway obstruction in the pharynx, stridor a higher pitched noise on inspiration/expiration in the larynx/trachea. These can be heard without a stethoscope. Sounds over the bronchial area of the chest will typically be higher pitched and loud compared to the lung parenchyma which are typically softer and lower pitched. Sounds over the larynx and trachea more intense can indicate upper obstruction or disease. Wheezes caused by movement through restricted airways usually indicate bronchial constriction or inflammation.
Crackles may indicate air movement through fluid such as pneumonia or pulmonary oedema. Ventral crackles are seen in pneumonia while dorsal crackles are seen with pulmonary oedema. Dull lungs sounds can indicate pleural space disease (the space between the visceral and parietal pleura)
or lung collapse.
Respiratory presenting patients must be managed carefully as additional stress can increase oxygen demand and hypoxemia and lead to respiratory arrest.
It is important to stabilise animals with respiratory distress.
· First priority is to initially assess the airway is patent, as the animal may require intubation.
· Provide oxygen supplementation via face mask 2-5L/pm, flow by oxygen 2-10L/pm, ET tube (dependent on circuit) or nasal prong oxygenation 50-100ml/kg/pm.
· Obtaining intravenous access is important for blood testing, medication/anaesthesia, and IV fluids.
Once stabilised a more thorough examination can begin.
· Pulse oximetry to measure arterial haemoglobin saturated with oxygen. SaO2 normal saturation >95%.
· Arterial blood gases analysis measure amount of oxygen and carbon dioxide dissolved in plasma. PaO2 parameters 80-110mmHg (breathing room air). PaCO2 parameters 32-43mmHg. Arterial carbon dioxide will only change with ventilation changes so PaCO2 can define hypoventilation >43mmHg and hyperventilation < 32mmHg
· Haematology including CBC, PCV, TS.
· Blood pressure. Parameters Systolic 100-160, Diastolic 60-100 Mean 80-120
· ETCO2 can be measured if ET intubated or placed in a face mask with supplemental oxygen. Normal ETCO2 in a dog is 35-45mmHg.
· Thoracic radiographs
Treatments may include;
· Sedation to reduce anxiety using anxiolytics or sedative analgesics such as butorphanol.
· Corticosteroids such as dexamethasone for inflammation causing oedema.
· Diuretics such as Furosemide for pulmonary oedema.
· Bronchodilators for broncho constriction.
· Cooling for hyperthermia with use of fan, room temperature IV fluids, cool water to auxilla, inguinal area and feet. Active cooling until temperature drops to 39.5 monitor Q5 for heatstroke patients.
In this case the dog is a pug, a brachycephalic breed and presenting with panting, orthopnea, elevated temperature and lethargy. Respiratory stertor is present and the dog is overweight. Once stabilised with oxygen, further examination under anaesthesia reveals BOAS brachycephalic
obstructive airway syndrome. Treatment is surgery to reduce the length of the soft palate, weight management and an exercise regime to reduce overheating