U3 O2 - Respiratory Emergencies Flashcards
What is respiratory distress?
Difficulty in breathing - seen in patients with respiratory
compromise
Difficulty breathing N.B. this is subjective (e.g. what an individual is feeling) so in veterinary patients the term respiratory distress is generally used instead
What is fractional inspired oxygen concentration (FiO2)?
Fractional inspired oxygen concentration is a measurement of the amount of oxygen being breathed in or delivered to the patient. Room oxygen is assumed to have an FiO2 of 0.21 i.e. 21% because the composition of room air is ~ 78% nitrogen, ~ 21% oxygen, ~ 0.96% argon and 0.04% carbon dioxide
For moderately dyspnoeic patients it is necessary to increase FiO2 above 0.5-0.6 and for severely dyspnoeic patients it is necessary to raise it above 0.9.
N.B. In a normal patient, the measured PaO2 should equal 5 x FiO2.
What are blood gases?
Oxygen and carbon dioxide levels are reflected by the PaO2 and PaCO2
What is Hypercapnia/hypercarbia?
Increased levels of arterial carbon dioxide
Hypocapnia/ hyporcarbia?
Decreased levels of arterial carbon dioxide
Wat is hypoxaemia?
Often used synonymously with hypoxia. However, the specific definition of hypoxaemia is decreased arterial oxygen level
What is hypoxia?
Decreased oxygen supply to all or part of the body. This can be due to hypoxaemia, reduced oxygen delivery (e.g. cardiac disease) or decreased tissue oxygen uptake (e.g. respiratory obstruction).
What is PaO2? What is the normal PaO2?
Partial pressure of oxygen in arteries - meaning the amount of oxygen present in arterial blood. Normal lung function should result in a PaO2 greater than 85mmHg when breathing room air (range ~ 90-100 mmHg). This indicates how well the blood is being oxygenated.
What is PaCO2? What is the normal PaCO2?
Partial pressure of carbon dioxide in arteries - meaning the amount of carbon dioxide present in arterial blood (range ~ 35-45 mmHg). This indicates the effectiveness of ventilation (breathing).
PaCO2 levels above 50mmHg are significantly elevated and require treatment; those above 70mmHg are imminently lifethreatening and often require mechanical ventilation to manage and reverse the respiratory acidosis. The level of CO2 in the blood stream regulates cerebral blood flow with hypercapnia increasing cerebral blood flow and hypocapnia decreasing cerebral blood flow. PaCO2 levels below 20mmHg, because of hyperventilation, can result in excessive cerebral vasoconstriction and therefore decreased cerebral blood flowthis can be life-threatening. As CO2 is acidic in solution,
increased levels in the bloodstream (arteries) will cause the pH of blood to decrease = respiratory acidosis. Decreased levels in the bloodstream (arteries) will cause the pH of blood to increase = respiratory alkalosis It is important to remember the role of blood CO2 in respiration. Increased levels of blood CO2 stimulate increased rate and depth of breathing. So, if PaCO2 levels drop dramatically, apnoea and respiratory arrest can occur.
What is SaO2?
This is a measurement of the % of haemoglobin that is saturated with oxygen.
What is SpO2?
This is a measure of SaO2 measurement determined by pulse oximetry. Because of where the pulse oximeter is applied this is a measure of the peripheral capillary saturation with oxygen.
What is ventilation?
The exchange of air between the lungs and the atmosphere i.e. breathing
What is hypoventilation?
Under-ventilation e.g. breathing is inadequate to eliminate CO2 and take in enough O2. Will result in increased PaCO2 and decreased PaO2
What is hyperventilation?
Over-ventilation e.g. breathing is excessive. Excessive
elimination of CO2. Will result in decreased PaCO2
What is Eupneoa?
Normal breathing
What is hyperpnoea?
Increased depth and rate of breathing usually to meet
physiological demands e.g. exercise. Blood gasses are normal
What is bradypnoea
Abnormally decreased respiratory rate
What is tachypnoea?
Abnormally increased respiratory rate
What is orthopnoea?
Adopting an upright/ standing or sitting position due to difficulty breathing often with the elbows abducted and neck extended
What is apnoea?
Abscence of breathing
What is paradoxical respiration?
This description can be applied to two situations.
1. A lack of synchronous movement of the chest and
abdominal muscles due to marked dyspnoea. Increased
intercostal muscle action, during inspiration, draws the
diaphragm cranially so the abdominal muscles appear to
be sucked inwards. This link demonstrates a cat showing
paradoxical respiration.
https://www.youtube.com/watch?v=fx2V0bZlIjg
2. A patient may have a flail chest following thoracic trauma.
As a result of having multiple, adjacent, segmental rib
fractures, the flail segment will move in an opposite
direction to the rest of the thorax during respiration.
See 3.2.6.4 Flail chest
What is Cheyne stokes respiration?
Pattern of crescendo-decrescendo respirations followed by a period of apnoea – may be present in a patient in a coma or if damage to medulla in the brain
What is agonal respiration?
Slow, shallow irregular respirations caused by brain
anoxia. Apnoea is imminent.
What is air hunger?
An animal in severe respiratory distress often adopts a posture to maximise intake of air- orthopnoea, elbows abducted, and head and neck extended
What is the main stimulus for the rate and depth of breathing?
In dogs and cats, the main stimulus for increased rate and depth of breathing is increased carbon dioxide levels in the blood stream (hypercapnia) rather than
decreased arterial oxygen (hypoxemia).
Arterial oxygen levels must fall very low (<
50 mmHg) before hypoxaemia stimulates breathing Decreased blood carbon dioxide (hypocapnia) is the main stimulus for decreasing ventilation. Respiratory distress is caused by decreased arterial oxygen levels (hypoxaemia) and/or increased arterial
carbon dioxide levels (hypercapnia)
Why is it important to monitor a patients respiration after an RTA, even if initially they seem to be fine?
The respiratory system should be assessed in all patients that present as an emergency, particularly if they have been involved in an RTA. It should be
remembered that a patient who has recently sustained thoracic trauma, and presents with mild to no respiratory distress, may deteriorate and require supportive measures e.g. the signs of pneumothorax will develop as more air builds up in the
thorax. A patient with pulmonary contusions may deteriorate over 6-12hrs despite having normal rate and effort on presentation. Animals with any respiratory compromise at presentation will require respiratory support and should be monitored for response to therapy. It is absolutely vital that a RVN carrying out triage can recognise a patient with even mild respiratory distress, as the risks of decompensation during the stabilisation period are significant. Special consideration
must be given to handling and housing to minimise stress whilst allowing the patient to receive intensive monitoring.
What are the signs of respiratory distress?
Signs of respiratory distress can include postural changes such as neck extension and elbow abduction ‘air hunger’; paradoxical abdominal breathing; restlessness; deep or shallow breaths; and increased or decreased respiratory rate.
How do you handle a patient that is in respiratory distress?
It is important to remember that a patient demonstrating these signs is at their limit of physiologic
reserves with a significantly decreased lung functional residual capacity. It is essential to minimise patient stress to avoid respiratory arrest and/or cardiac arrest;
it is also essential that handling or positioning of the patient does not prevent them adopting its preferred position. Ideally a patient would be observed from a distance initially to obtain a true assessment of the its respiratory rate, effort and pattern with minimal stress
What is the normal respiratory rate for dogs
The normal respiratory rate is ~ 10-30/ minute in dogs
What is the normal respiratory rate for cats
The normal respiratory rate is ~ 20- 30/ minute in cats (range 24 - 48 breaths per minute)
What rate is tachypnoea generally considered to be?
Increased respiratory rate (tachypnoea) in dogs
and cats is generally considered to be above 50 breaths per minute.
What can be other causes of tachypnoea unrelated to respiratory distress? What is the white coat effect?
However, it is important to assess it in context - the respiratory rate may be increased in a patient
who is anxious or painful. “White coat” effect is common in patients presenting to veterinary practice – it is important to appreciate the patient’s respiratory rate may be elevated purely in response to being in the clinic.
Other causes of tachypnoea should be considered in trauma patients since an increase in respiratory rate does not always indicate respiratory compromise. Pain,
fever, hyperthermia, stress/fear, and compensation for metabolic acidosis will all cause an increase in respiratory rate.
What is increased respiratory effort characterised by?
Normal respiratory effort involves only slight outward movement of the thorax during inspiration with minimal movement of the abdominal musculature – if there is
abdominal muscle involvement in breathing, the walls of the thorax and the abdominal wall move outwards at the same time during normal inspiration. Increased
respiratory effort (respiratory distress) is characterised by increased thorax and abdominal musculature motions; and is perceived as laboured or difficulty in
breathing. In some patients there may only be increased thoracic excursion.
Signs of increased respiratory effort include extension
of the head and neck and abduction of the elbows. Nostril flare may be observed.
Open-mouthed breathing may be a sign of severe respiratory distress in cats, especially
What respiratory signs are seen in a patient with a tension pneumothorax? What action needs to be taken?
It should be noted that in a patient with a tension pneumothorax, there is actually reduced movement of the thorax as the pressure in the intra-thoracic space
increases and minimises the ability to ventilate at all. This is a respiratory emergency and needs rapid intervention.
What pleural space disease can cause respiratory effort?
An increase in respiratory effort can be seen with pleural space disease (e.g. pneumothorax, haemothorax or diaphragmatic hernia), pulmonary parenchymal
disease (e.g. pulmonary contusions, pulmonary oedema and pneumonia) and upper airway disease.
What type of respiratory problems are associated with laboured inspiration?
Upper airway problems such as brachycephalic obstruction syndrome, laryngeal paralysis or airway obstruction are associated with laboured inspiration.
What type of respiratory problems are associated with laboured expiration?
Lower airway problems are associated with laboured expiration.
What type of respiratory problems are associated with laboured inspiration and expiration?
Parenchymal (lung tissue) conditions are associated with laboured inspiration and expiration.
What type of respiratory problems are associated with rapid and shallow inspiration and expiration?
Pleural space disease is associated with rapid and shallow inspiration and expiration.
What disease processes or intoxications can lead to reduced respiratory effort?
Decreased respiratory effort is less commonly seen and is characterised by decreased thorax and abdominal muscle movement. Disease processes associated
with decreased respiratory effort include brain and spinal injury, and end stage respiratory fatigue. It may also be seen with some intoxications that cause severe
respiratory depression such as baclofen ingestion.
What is paradoxical respiration and what causes it?
Paradoxical respiration is an indicator of severe inspiratory effort where the thorax moves outwards with inspiration; and the abdominal muscles are pulled inwards. Causes of paradoxical respiration include upper airway obstruction, diaphragmatic injury (rupture; or paralysis secondary to injury to the cervical spinal cord or the phrenic nerve) and severe decreases in pulmonary compliance (as may occur with severe pulmonary contusion).
What is a flail chest?
A flail chest is a type of segmental fracture where fractures of two or more adjacent ribs, in two or more locations, results in a ‘flail segment’. This may be caused by a crush injury e.g. small dog/cat grasped by large dog; fall or kick.
What will be noted on a patient’s respiration if they have a flail chest?
The fractured section of the chest wall moves in the opposite direction to the rest of
the thorax during breathing. It is drawn inward on inspiration due to negative
pressure generated within the thorax and the free-floating nature of the fractured
segment. Similarly, the segment will move outward on expiration.
What type of pain relief will a patient with a flail chest require?
This is a very painful condition and provision of analgesia is essential. A local anaesthetic ring
block either side of the flail segment, in addition to systemic opioid, is commonly required.
Why should flail segments be splinted?
Additionally, the flail segments are often splinted to reduce the movement and discomfort associated with the fractured ribs grating against each other and to
decrease the risk of the fractured ribs causing lung damage.
Why is it important that a patient with a flail chest is repositioned if they prefer to lie on the affected side?
A patient with a flail chest will often prefer to lie on the affected side as this minimises movement of the
flail segment. However a significant nursing consideration/ concern for this patient is the need to re-position to avoid atelectasis and further compromise of ventilation.
What is the normal partial pressure of oxygen in arterial blood?
The partial pressure of oxygen in arterial blood (PaO2) should normally be > 90-100 mmHg
When is cyanosis seen and what partial pressure of oxygen will there be in arterial blood?
Cyanotic mucous membranes are seen
with severe hypoxaemia (PaO2 < 80 mmHg)
How much haemoglobin is present in a patient with cyanosis?
By the time cyanosis is apparent, it means the haemoglobin is very poorly oxygenated i.e. a profound disturbance in the oxygenation of haemoglobin. At this point there is at least 50 g/L of deoxygenated
haemoglobin in the bloodstream meaning that significant hypoxaemia must therefore occur before a patient’s mucous membranes are cyanotic. Thus, it is essential to be aware that the absence of cyanosis does not rule out significant respiratory compromise.
Why might a patient with an SPo2 reading of >90% be seriously hypoxaemic?
even if PaO2 has declined significantly/ dangerously from 100-80 mmHg, the pulse oximeter reading SpO2 remains relatively high (> 90 %). It is only when the PaO2 declines even lower (< 60 mmHg) that the
pulse oximeter reading starts to decline significantly. Most sources state that if the SpO2 is less than 94%, for a patient breathing room air, then supplemental oxygen
should be supplied because this patient is likely to be seriously hypoxaemic (PaO2 < 80 mmHg.) See 3.2.8 for a description of assessment of pulmonary function in
relation to PaO2, SaO2 and SpO2 etc.
What toxin can causes the mucous membranes to be a cherry red colour?
There are toxins that can cause respiratory difficulty/ distress and can alter the colour of blood. Examples are carbon monoxide (which can turn the blood/ mucous
membranes cherry red)
What toxin can causes the mucous membranes to be a muddy brown colour?
There are toxins that can cause respiratory difficulty/ distress and can alter the colour of blood. Examples paracetamol (which turns the blood/ mucous
membranes a muddy brown colour).
What effect does paracetamol have on red blood cells and haemoglobin?
In addition to causing liver damage, metabolites of paracetamol cause damage to red blood cells. This oxidative damage leads to alteration of the iron in
haemoglobin leading to formation of methaemoglobin. Unlike haemoglobin, methaemoglobin does not release oxygen molecules to tissues which results in
hypoxia. Methaemoglobinaemia causes the blood and mucous membranes to appear brown therefore pulse oximeter readings will not be accurate. Brashear
(2013) discusses acetaminophen (paracetamol) toxicity and includes an image of an effected patient
How does Carbon monoxide effect red blood cells and haemoglobin?
Carbon monoxide has a much stronger affinity for binding with haemoglobin than oxygen – resulting in oxygen being displaced from the haemoglobin molecule. This results in decreased oxygen delivery to cells and progressive hypoxia. The patient may have cherry red mucous membranes but this is not a
consistent finding. Pulse oximetry readings will also not be accurate in this condition demonstrating the importance for all patients of assessing the patient clinically rather than relying on monitoring devices.
What is subcutaneous emphysema?
Air under the skin
If a patient has subcutaneous emphysema, it feels as if there is crackling under the skin when palpating the skin around the neck and thorax.
If there are abnormal sounds such as hissing in a patient in respiratory distress what might this indicate?
Any abnormal noises should be noted e.g. hissing. This might indicate air leakage from e.g. a tracheal rupture. Subcutaneous emphysema is another clinical sign that
might be present in a patient with rupture or penetrating wound of the larynx, trachea or the bronchial tree
If crackles are heard on thoracic auscultation what could this indicate?
Crackles are produced by a gas/fluid interface (e.g. oedema, pneumonia, contusion, haemorrhage);
If wheezes are heard on thoracic auscultation what could this indicate?
wheezes typically from the movement of air through a narrowed airway (e.g. feline lower airway disease). Wheezes may have a musical quality
If there are quiet lung sounds on thoracic auscultation what could this indicate?
Auscultation of the thorax of patients with pleural space disease will reveal quiet lung sounds
If gut sounds/borborygmi are heard on thoracic auscultation what could this indicate?
if the patient has diaphragmatic rupture, gut sounds/ borborygmi may be auscultated.
If loud lung sounds are heard on a dyspnoeic patient on thoracic auscultation what could this indicate?
If there is pulmonary parenchymal disease, and the animal is dyspnoeic then louder lung sounds than normal will usually be heard
If quiet lung sounds are heard dorsally on thoracic auscultation what could this indicate?
Quiet lung sounds dorsally are consistent with a pneumothorax
If quiet lung sounds are heard ventrally on thoracic auscultation what could this indicate?
quiet lung sounds ventrally are consistent with a pleural effusion
How do you manage a patient that is in respiratory distress when it presents for an emergency?
Where possible a patient should be left to rest
and supplied with oxygen before it is examined e.g. a cat placed in an oxygen cage.
However, as mentioned above with pleural space disease emergency thoracocentesis may be required as soon as possible to facilitate improved ventilation. In this scenario, it is sensible to provide supplemental oxygen to the patient whilst the equipment is prepared for thoracocentesis. The veterinary surgeon may decide that mild sedation, alongside oxygen therapy, should be administered if the patient does not appear to be in pain. In this situation, butorphanol is often used as it has a predictable onset and duration of action, with minimal cardiovascular and respiratory depression. If the patient is in respiratory distress following a painful, traumatic incident, then a stronger analgesic will be more appropriate.
What inspired oxygen content is produced from 2-3 l/min of flow by oxygen?
Flow-by oxygen, 2-3 l/min, may produce an inspired oxygen content that is ~ 25%- 40% (x2 concentration of oxygen in normal room air) i.e. a FiO2 of 0.25-0.4; at a flow rate of 5-6 l/min, a loose-fitting mask will provide ~35-55 % (x 2-4 concentration of oxygen in normal room air) i.e. a FiO2 of ~ 0.35- 0.55
What oxygen level can a tight fitting mask provide? What is the disadvantage of this?
A tight-fitting mask in a collapsed individual can provide an oxygen level of 70-90% (> x 4 room air) i.e. FiO2 of 0.7-0.9 but promotes rebreathing of CO2 and may cause hyperthermia
How do you give flow by oxygen effectively?
Flow by is only effective if it is very close to the patient’s mouth and nose - having the end of the oxygen line more than a cm or so away from the patient probably has minimal benefit. It can be useful, if the patient tolerates it, to hook the line through the patient’s collar, if wearing one, and then position it in such a way it is
close to the mouth and nose.
If using a tight-fitting mask for oxygen delivery, it should be removed intermittently to clear away condensation that will build up and build-up of CO2. Patients receiving oxygen via mask should have their eyes lubricated often as oxygen is a cold dry gas
which can dry the corneas and lead to ulcers.
How do you provide oxygen using a oxygen collar tent?
Oxygen collar tent - ‘Crowe Collar’
Other techniques can be employed. These include applying an Elizabethan collar to the patient: making sure it extends beyond the patient’s nose. The front of the collar is then covered with cling-film; the tubing from the oxygen supply is then fed in from the animal’s collar/neck. It is important to leave a 2.5-5cm opening at the top of the cling-film to ensure carbon dioxide and moisture can escape - as oxygen is heavier than air it will remain within the ‘tent’. Despite this, the temperature and humidity within the mask can still rapidly increase and some patients do not tolerate this
technique of oxygenation
What should inspired oxygen levels be if the oxygen level is at 1-8l/minute using an oxygen collar tent?
At 1-8 l/minute (depending on the patient size), inspired oxygen levels should be ~30- 60 % i.e. FiO2 0.3-0.6
What are the disadvantages of an oxygen cage?
Disadvantages of oxygen cages include patient isolation (Waddell and King, 2018), the prolonged
period it can take for the, often, large space to reach significant oxygen enriched levels (meaning that it is only ~ 50% oxygen being delivered i.e. FiO2 of 0.5
; and the cost of oxygenating so much free space.
Large patients are unlikely to be able to fit into them. The oxygen levels decrease rapidly each time the cage is opened. Improvised oxygen cages can develop high
humidity and temperature levels; and can make it difficult for the nurse and clinician to monitor the patient.
Oxygen cages can either be improvised within the practice or specifically designed for the purpose e.g. a Snyder oxygen cage. In theory an oxygen cage should be able to provide a FiO2 of 1.0 e.g. 100% oxygen
What are the advantages of an oxygen tent?
They may be beneficial where other techniques are not being tolerated by the patient; and, in the case of cats, where confinement away from other animals and humans can allow them to calm down and so reduce their oxygen demand. Placing cooling devices e.g. icepack on top of the oxygen cage, can help
with cooling
What are the advantages of an incubator?
Incubator
Paediatric, thermostatically controlled, human incubators can be used for small patients and are very efficient- reaching oxygen levels of ~ 80-90% i.e. FiO2 of 0.8- 0.9. They also have the benefit of humidifying the gases. Small doors allow for patient monitoring without significant oxygen loss.
What are the different nasal catheters/prongs for oxygen delivery?
Two main types of nasal catheter can be used - the single nasal catheter that may, either, be an adapted pliable feeding tube, a red rubber urinary catheter or a
dedicated nasal catheter; or nasal prongs, as used in human medicine, which sit as a looped tube around the nose, with a small prong from the tube inserted into each nostril.
What is the percentage of fractional inspired oxygen concentration for a patient with bilateral nasal catheters?
Using nasal catheters bilaterally will increase the FiO2 by up to 60% if used in both nostrils
What are the disadvantages of nasal oxygen catheters?
Nasal oxygen catheters are not effective at increasing FiO2 in patients that are panting or open mouth breathing. Some animals do not tolerate nasal
prongs and they are easily dislodged. Brachycephalic breeds may have stenotic nares (abnormal narrowing or constricted) that may not allow insertion of a catheter – however in many brachycephalic patients nasal prongs are well-tolerated and remain in place. A tape bridge over the nasal prongs can be helpful. On occasion, if a patient requires long term supplementation e.g. aspiration pneumonia, a clinician may suture nasal prongs to the lateral edge of the alar fold.
What is trans-tracheal oxygen delivery?
Trans-tracheal oxygen provision is a temporary rescue procedure until a patent airway can be provided e.g. a tracheostomy tube. As oxygen is delivered via a
catheter or needle placed between tracheal rings, the pressure and flow rate can be compromised due to the narrow bore.
What level of oxygen and for how long would impose a risk of oxygen toxicity?
For all methods of oxygen delivery, if prolonged supplementation is required, the oxygen should be humidified; if supplementary oxygen is supplied at an FiO2 > 0.6 for long time (>12 hours), the lungs are at risk of damage- ‘oxygen toxicity’
What is the most efficient means of oxygen delivery in an unconscious patient?
Endotracheal (ET) intubation
In the unconscious, emergency patient without an upper airway obstruction, placing an ET tube ensures a patent airway and is the most efficient means of oxygen delivery. It also allows intermittent positive pressure ventilation (IPPV) to be performed as well as the provision of 100% oxygen.
In what situations might a tracheostomy be required?
Where complete upper airway obstruction has occurred, e.g. a pharyngeal foreign body, laryngeal or tracheal trauma (especially dog bites), pharyngeal or laryngeal foreign bodies, or laryngeal paralysis an emergency tracheostomy may be required
When should tracheostomy tube be placed?
If there is any chance that a patient might require a tracheostomy, the procedure should ideally be performed before the patient becomes apnoeic
secondary to the airway obstruction. Therefore, very careful patient monitoring is essential with the veterinary surgeon being alerted immediately if the patient worsens. Any patient deterioration e.g. worsening of stertor/ stridor, increased respiratory rate and effort and signs of air hunger is an indication for tracheostomy in this situation . It is far safer to place a tracheostomy tube in a controlled manner than
as an emergency once the patient arrests.
What are some effective cooling techniques?
Effective cooling techniques include electric
fans, spraying with tepid (not cold water), cool intravenous fluids (but avoiding over infusion) and cool packs in the axillae and inguinal region N.B. ice should not be applied directly to the skin as it can cause burns. If ice or cold water is applied to the skin, it may cause peripheral vasoconstriction thus limiting heat loss and shunting the hot blood back to the main organs so risking further damage occurring. Placing towels soaked in cool water over the patient will insulate the patient
and prevent further heat loss- therefore this is not an effective means of promoting heat loss
What is the use of ultrasound in a patient in respiratory distress?
Point of care ultrasound examination (POCUS) can be an especially useful technique in trying to determine the cause of respiratory distress in an emergency
patient. It can be performed kennel-side with minimal to no patient restraint being required. As with all POCUS/FAST techniques, the aim is to answer specific
questions i.e. is there evidence of pleural effusion, pneumothorax or pericardial effusion? It may also identify soft tissue within the thorax (Waddell and King, 2018).
Ultrasound can also be used when emergency procedures are being performed e.g. thoracocentesis
What use is radiography in a patient in respiratory distress?
Radiography of the thorax may provide useful information e.g. identify rib fractures, cardiomegaly, pulmonary contusions etc. However, its use is limited in the patient in respiratory distress as any manipulation for X-ray positioning could cause the patient
to deteriorate further. The only position a patient with respiratory distress could possibly be placed in is sternal recumbency for a dorso-ventral (DV) view- however this should not be attempted if it causes any further distress to the patient. A DV view
of small patients can sometimes be obtained by X-raying them in an oxygen cage. If radiography is performed, it may be possible to angle the beam by 90˚ to obtain a lateral view with horizontal beam radiography. Although great care must be taken
when performing this view to avoid accidental exposure of personnel to ionising radiation.
What is the commonest form of laryngeal disease?
The commonest form of laryngeal disease is laryngeal paralysis.
What is laryngeal paralysis generally caused by?
This is generally caused by compromised nerve supply to the muscles of the larynx which are responsible for moving vocal folds and so altering the size of the glottis during inspiration.
What are the two different types of laryngeal paralysis?
This can be congenital or acquired.
What is the commonest form of larygeal paralysis and what species/breed does it affect?
Idiopathic, acquired, laryngeal paralysis is the commonest form, generally seen in older, large-breed dogs such as Labrador Retrievers and Golden Retrievers. It can occur in cats occasionally. Other acquired forms can occur due to neck or thoracic
trauma
Where does the recurrent laryngeal nerve originate from and travel to?
The recurrent laryngeal nerve originates from the cervical spinal cord but travels down into the thorax, before then returning to the neck to innervate the
larynx.
What signs will an animal with laryngeal paralysis display?
The patient often presents in respiratory distress with marked inspiratory effort and stridor due to the narrowing of the larynx. The stridor commonly sounds like a whistle which becomes higher in pitch as the obstruction worsens . The patient may be collapsed and cyanotic, with/ without a cough. The owner may report a recent change in phonation, exercise tolerance, noisy breathing and/ or dysphagia. The patient may also be hyperthermic which further increases the oxygen demand, hypoxia and patient distress
How do you diagnose laryngeal paralysis?
The history, presentation and physical examination are usually highly suggestive of laryngeal paralysis. Once the patient is stable, the diagnosis can be confirmed under general anaesthetic by visualising movement of the vocal folds of the larynx, using a laryngoscope (or endoscope). Both unilateral and bilateral paralysis may occur.
describe the initial management and nursing of a patient with laryngeal paralysis?
Initial management involves placing in a low stress environment with minimal handling and provision of oxygen therapy (see above). Cooling of the patient, as
described in 3.2.3.2 will be required if the patient is hyperthermic. Sedation, on veterinary direction, will often have an anxiolytic effect and help to improve the
patient’s breathing, hopefully preventing the need for further emergency intervention, until medical treatment and active cooling starts to be effective. Corticosteroids (e.g. dexamethasone) are likely to be administered for their anti-inflammatory effect.
Whilst anti-tussive medication may also be considered in some patients, care must be taken not to suppress coughing if there is any risk of aspiration pneumonia. As there will often be large amounts of mucous and saliva in the pharynx/ oral cavity, suction may be required. This should be readily available for any patient who requires rapid anaesthetic induction and intubation.
In severe cases the patient may need to be anaesthetised and intubated for a period until the swelling and oedema has reduced. Occasionally a patient may need to undergo an emergency tracheostomy if they cannot be managed by other means.
describe the initial management of a patient with laryngeal paralysis?
Initial management involves placing in a low stress environment with minimal handling and provision of oxygen therapy (see above). Cooling of the patient, as
described in 3.2.3.2 will be required if the patient is hyperthermic. Sedation, on veterinary direction, will often have an anxiolytic effect and help to improve the
patient’s breathing, hopefully preventing the need for further emergency intervention, until medical treatment and active cooling starts to be effective. Corticosteroids (e.g. dexamethasone) are likely to be administered for their anti-inflammatory effect.
Whilst anti-tussive medication may also be considered in some patients, care must be taken not to suppress coughing if there is any risk of aspiration pneumonia. As there will often be large amounts of mucous and saliva in the pharynx/ oral cavity, suction may be required. This should be readily available for any patient who requires rapid anaesthetic induction and intubation.
In severe cases the patient may need to be anaesthetised and intubated for a period until the swelling and oedema has reduced. Occasionally a patient may need to undergo an emergency tracheostomy if they cannot be managed by other means.
What monitoring should a patient with laryngeal paralysis have?
Ongoing monitoring and nursing care requires assessment of respiratory rate and pattern, mucous membrane colour, body temperature (hypothermia should be avoided; pyrexia may be present if aspiration pneumonia) and perfusion parameters (care must be taken not to over-infuse IV fluids and cause greater breathing difficulties). Arterial blood gas measurement (PaO2 and PaCO2) is the best indicator of effective ventilation. If arterial sampling is not possible venous blood gas measurement can be performed. The patient should be cage-rested and exercise restricted. Great care should be taken when feeding if the patient has dysphagia. In this situation, food is normally fed ‘balled up’ and from a height to encourage appropriate swallowing. If placed careful monitoring and maintenance of the tracheostomy tube and the tracheostomy site (see section 3.2.7.3) is required.
Longer term a weight loss programme may be required; surgical solutions to laryngeal paralysis include laryngeal tie-back (arytenoid lateralisation). In the period between initial presentation and surgical intervention, acupuncture may provide
some relief for a patient with laryngeal paralysis
Describe the nursing considerations for a patient with laryngeal paralysis?
A patient with laryngeal paralysis is often middle to older aged and often a larger breed. Additional concerns and co-morbidities may be present e.g. osteoarthritis.
Padded bedding in the kennel and protection of pressure points may be needed.
Stress must be kept to a minimum and ongoing sedation may be indicated to manage this in some patients. Recumbency management, including adjustments in
position to avoid further compromise of lung function, is indicated. If the patient is mobile and the veterinary surgeon approves, short periods of slow calm exercise will help maintain mobility and, in the case of patients with pneumonia/aspiration pneumonia will loosen lung secretions. Coupage may also be indicated for these
patients. Alongside assessment of the respiratory system function, ongoing monitoring must also focus on the patient’s ability to carry out day to day activities. If there is any disparity between this and the patient’s ability, then nursing care must be provided to bridge the gaps until the patient recovers.
Where is the most serious tracheal foreign body found and why? What is it important not to do?
Foreign bodies (FB) may lodge in the trachea. The most serious foreign body, however, is likely to be found in the caudal pharynx, just in front of the epiglottis. This may cause a complete obstruction of the airway. It occurs relatively commonly in dogs with ‘the swallowed ball syndrome’, causing rapid asphyxiation, respiratory arrest and death. It is very important not to try to remove a pharyngeal foreign body from the conscious patient (and to advise the owner of this). It is very unlikely to be successful; will distress the patient further; possibly cause injury to the handler and run the risk of dislodging the foreign body further into the trachea. N.B. It is much harder, in a sedated patient, to retrieve a tracheal foreign body, than a pharyngeal foreign body.
What breed is tracheal collapse most commonly seen?
Tracheal collapse is commonly seen in smaller breeds, particularly the Yorkshire Terrier.
What is tracheal collapse due to?
The condition is due to a weakness of the cartilage that maintains the luminal shape of the trachea. In affected dogs, the unsupported section of the trachea (dorsal tracheal membrane) dips into the lumen causing partial to complete occlusion during respiration
What signs are seen in a patient with tracheal collapse?
This results in chronic cough and exercise intolerance. A patient with tracheal collapse often has a distinctive cough, which is usually harsh and dry cough - sounding like a goose ‘honk
With tracheal collapse and tracheal stenosis, the patient will usually have a history of persistent cough and exercise intolerance. Palpation of the distal cervical trachea is likely to induce a harsh cough. The patient may present in acute respiratory distress with tachypnoea and marked inspiratory effort, if there is complete collapse of the trachea
What are the signs of a partial or complete tracheal foreign body obstruction?
With a foreign body, causing a partial obstruction, there may be harsh, coughing and a foul-smelling odour. The odour originates from the airways, particularly if the FB
has been there for a few days. In the case of a complete airway obstruction, as can occur with a ball caught in the caudal pharynx, the dog will often impersonate a goldfish-opening and shutting its mouth but unable to breathe or make a sound. This
is naturally a hyperacute emergency, as after a minute or so of a complete obstruction, the patient will be comatose
How are tracheal abnormalities e.g. foreign body or collapse, diagnosed?
History, and palpation of the neck and pharyngeal region (if appropriate) will often detect a pharyngeal foreign body; or stimulate a cough reflex in tracheal collapse cases. An examination of the oral cavity will determine if a pharyngeal foreign body exists, although this is unlikely to be appropriate in distressed patient; anaesthesia may be required to confirm the presence, and remove, many foreign bodies. If a
pharyngeal foreign body e.g. grass blade in a cat or tracheal foreign body, of several days’ duration, exists then there is often a foul odour to the breath.
Further diagnostic testing for tracheal conditions, may include endoscopy under general anaesthesia. The tracheal lumen can be assessed; and tracheal foreign
bodies may be identified and removed. Radiodense tracheal foreign bodies can be detected radiographically. Because the gas-filled tracheal lumen appears radiolucent radiographically, even slightly radiopaque foreign bodies may be apparent.
Radiography can be used to assess the trachea for e.g. stenosis or collapse but dynamic real-time fluoroscopic imaging is of greater diagnostic value.
Describe the initial management of a patient with a partial or complete tracheal obstruction?
The initial management of the emergency presentation, with a partial or complete tracheal obstruction, is to try to minimise respiratory distress whilst anticipating that further veterinary interventions will be required. Patient handling should be limited, flow-by oxygen should be provided and preparation for the general anaesthetic, that will probably be required, should be performed. Sedation may be indicated to reduce the patient’s level of distress. However, it is vital that everything is prepared for a rapid induction of anaesthesia as the patient y can decompensate very quickly.
In a patient with complete airway obstruction, the veterinary surgeon must be summonsed immediately. However, the RVN can and should place an endo-tracheal tube, if appropriate i.e. not a foreign body obstruction and provide oxygen until the veterinary surgeon arrives. Rapid intravenous anaesthetic induction will be required, followed by manual removal either through the mouth, in the case of a pharyngeal
foreign body; or via endoscopy/ tracheotomy for a tracheal foreign body. An emergency tracheostomy or trans-tracheal catheterisation may be required, prior to
pharyngeal foreign body removal, to provide emergency oxygen to help stabilise/calm the patient - see section 3.2.7.3 for further information on these
techniques.
Additional, initial management of other tracheal conditions is aimed at counteracting the hyperthermia that occurs following upper airway obstruction and calming the patient. The animal may be cooled as previously discussed; the veterinary surgeon may prescribe an anxiolytic (mild tranquilliser), e.g. acepromazine to reduce excitation and aid treatment of hyperthermia. However, these drugs should be used
with caution in brachycephalic breeds and patients with cardiovascular disease. Any patient who has received acepromazine, needs constant monitoring for evidence of hypotension, especially if brachycephalic or with pre-existing cardiovascular disease.
The head and neck should always be kept extended in sedated patients, with the mouth opened and the tongue pulled forward if possible.
In a patient with tracheal collapse, anti-inflammatory medication, to decrease tissue inflammation/oedema, and anti-tussive medication may be administered. Opioids e.g. codeine or butorphanol, at doses lower than used for sedation, have a moderate anti-tussive effect. Tracheostomy is not likely to help a patient with tracheal collapse as large sections of the cervical and thoracic trachea can be affected (Waddell and
King, 2018). If medical management is not successful, surgical treatment may be indicated e.g. tracheal stenting or placement of extraluminal tracheal ring
prostheses.
What monitoring should be carried out on a patient during the initial management of a partial or complete tracheal obstruction?
In addition to monitoring the respiratory system, perfusion parameters should be constantly monitored. SPO2 monitoring provides valuable information about the ability to deliver oxygen during the recovery period. Blood pressure should be monitored regularly- many sedatives and anaesthetic agents cause vasodilation and hypotension. This may need to be managed during sedation, anaesthesia or recovery.
Close, careful monitoring is indicated in a patient that has had treatment for tracheal obstruction. It is possible the obstruction will re-occur in a patient with tracheal
collapse. Also, a patient which has had a solid foreign body removed may have increasing swelling due to ongoing inflammation and/or infection. If a patient
recovering from upper airway obstruction, develops increasingly noisy breathing the veterinary surgeon should be immediately alerted and the cause investigated as soon as possible.
Aside from tracheal obstruction what might be other causes that a patient presents with upper respiratory tract signs?
Inflammatory naso-pharyngeal polyps in cats, upper airway masses, feline viral upper respiratory tract disease, infection laryngotracheitis ‘kennel cough’ in dogs and smoke inhalation are other possible causes of a patient presenting as an emergency
with upper respiratory tract signs.
What reasons might a patient present to emergency due to nasal disease/injury?
There are various reasons for emergency presentations due to nasal disease/ injury including brachycephalic obstructive airway syndrome (BOAS), nasal foreign bodies, trauma, neoplasia and nasal/nasopharyngeal polyps. Stenotic nares and narrow nasal passages associated with brachycephalic obstructive airway syndrome; and trauma of the nasal passages can lead to upper airway obstruction
What is BOAS?
brachycephalic obstructive airway syndrome
What breeds are typically seen with BOAS?
BOAS is typically seen in brachycephalic breeds such as English and French Bulldogs, Boston Terriers and Pugs, especially if they are obese
What conformational problems are associated with BOAS?
The conformational problems associated with BOAS include- stenotic nares, excessive pharyngeal soft
tissue, elongated soft palate and hypoplastic trachea
Why does the pharynx, soft palate and larynx of brachycephalic dogs become oedematous, swollen and hyperplastic?
Affected dogs must increase their inspiratory effort to help overcome the resistance created by the various upper airway obstructions. This high negative pressure leads to the soft tissues of the upper respiratory tract being sucked into the air passages so causing further obstruction (University of Cambridge, 2019). The soft tissues become oedematous, swollen and hyperplastic and the negative pressure causes the laryngeal saccules to collapse so compounding the problem. The combination of swollen, oedematous, hyperplastic tissues (pharynx, soft palate and larynx) plus
laryngeal saccule eversion and laryngeal collapse can lead to asphyxiation.
Why are brachycephalic breeds prone to hyperthermia?
Brachycephalic obstructive airway syndrome (BOAS) can also lead to rapid onset hyperthermia, especially in hot weather, due to the muscular effort required to
breathe
What secondary causes might a patient present with epistaxis?
Patients may also present with epistaxis secondary to trauma, coagulopathy, nasal aspergillosis or neoplasia
Epistaxis is usually unilateral but could be bilateral secondary to coagulopathy or erosion of vomer bone by tumour. There may be evidence of head trauma and it is important to assess the patient carefully for neurological signs in this case; or hypovolaemia if coagulopathy is a possibility. Epistaxis can be associated with other trauma e.g. knock on the nose with a heavy ball etc. The nose, especially in dogs, has a well-developed supply of arteries and veins and so bleeding can be significant.
What are foreign bodies of the nasal cavities associated with? What signs may be apparent?
Foreign bodies of the nasal cavity are often associated with grass blades or grass seeds but can also be sticks etc. Grass blades may be swallowed, coughed or
regurgitated and can lodge in the caudal nasal passages or nasopharynx. Grass seeds can also be inhaled into the nasal cavity and travel to the lungs where they can cause further damage
Nasal foreign bodies are usually unilateral- clinical signs are variable. There may be sneezing and/or a unilateral nasal discharge; or gagging and dysphagia. There may be an odour from the affected nostril. Sometimes affected cats are anorexic, lethargic and depressed but with no obvious nasal signs.
What can be the cause of inspiratory stridor in young cats?
Nasopharyngeal polyps are common in cats and may be found in the nasal passages, the pharynx or the middle ear cavity with the clinical signs being dependant on the location. Those in the nasopharynx can be a cause of inspiratory stridor often in young cats.
What are the clinical signs of BOAS in animals that present as an emergency?
In a patient with BOAS, the clinical signs will depend on the degree of obstruction and secondary complications at presentation. The patient may only have stertorous (snoring, sonorous respiration) breathing; or it may be making marked inspiratory effort, with mouth breathing and respiratory distress, as well as being hyperthermic. It could be collapsed and cyanotic. It should be noted when carrying out triage of brachycephalic breeds, that many clients consider the stertor or stridor associated with their pet’s breathing to be completely normal. It is important, therefore, not to be judgemental - it is often more beneficial to ask the owner if the breathing noises have worsened over time.
What are the signs of nasopharyngeal polyps?
Nasopharyngeal polyps may cause a marked inspiratory stertor, often in young cats, which may result in mouth breathing. They may also cause sneezing, nasal discharge, gagging, dysphagia and altered voice. Whilst the naso-pharyngeal polyp, may have been present for some time, signs may appear to develop suddenly.
Nasal tumours will have similar respiratory signs as nasopharyngeal polyps although there may be other signs e.g. epistaxis, pain, deformity. The signs are usually unilateral initially.
How do you diagnose BOAS?
Brachycephalic obstructive airway syndrome may be suspected from the breed, clinical history and presenting signs. Following emergency stabilisation, endoscopic or laryngoscopic examination of the caudal pharynx and larynx, under anaesthesia, will show evidence of soft tissue oedema and inflammation, elongated soft palate, eversion of the laryngeal saccules and possibly laryngeal collapse.
How would you diagnose and treat a nasal foreign body?
Nasal foreign bodies may be visualised using fine needle or rigid endoscopes. Alternatively, a bronchoscope may be passed through the mouth, in the anaesthetised patient, and reflexed rostrally to look behind the soft palate as many blades of grass are only visible caudally.
Nasal foreign bodies may be manually removed, using endoscopic equipment, under anaesthesia. Antibiotics may be required if there is secondary infection.
How do you diagnose a nasopharyngeal polyp?
Nasopharyngeal polyps may be seen at the nares rostrally; or may require a needle or rigid endoscope to visualise them.
