73 | The step-by-step guide to managing pleural space disease as a vet nurse
Today we’re kicking off a little mini-series on pleural space disease in dogs and cats.
Pleural space disease is a big topic, so we’ll spend the next few episodes looking at some of these diseases in more detail - but today we’ll look at what the pleural space is, why it should be there, and what happens when things end up in there when they shouldn’t.
We’ll touch on the common causes, the signs to look out for, and the diagnostic, treatment, and nursing care needs these patients have, so that you can make more of a difference to them in practice.
So let’s get to grips with what pleural space disease is, and how to help patients with it.
Let’s start from the top: What is the pleural space, and why is it so critical?
The pleural space is a tiny space sitting between the lungs and the chest wall. This space is normal - unless it becomes bigger and fills with content.
The lungs and the chest wall are covered with thin membranes called pleura.
The visceral pleura covers the outer surface of the lungs, while the parietal pleura lines the inside of the chest wall, the diaphragm, and parts of the mediastinum.
Between these pleural membranes lies a small amount of pleural fluid. This fluid acts as a lubricant, reducing friction as the lungs expand and contract during normal respiration.
Since our patients are negative pressure ventilators - ie, the chest is a vacuum, which ‘pulls’ air in to expand the lungs - the pleural space is also under negative pressure. This helps to keep the lungs inflated and functioning efficiently, pulling oxygen-rich air into the alveoli for gaseous exchange.
That negative pressure is lost when the pleural space fills with air, fluid, or tissue. The lungs can't fully expand, and oxygen delivery is compromised. In a nutshell, that’s pleural space disease.
If air enters the pleural space, the lungs recoil inward due to changing pressures within the chest. If fluid enters, it compresses the lungs from the outside.
Either way, the result is hypoventilation and respiratory distress - all very bad news for our patient.
So that’s what pleural space disease is - but what causes it?
There are lots of different types of pleural space disease. We see some, like pneumothorax or pyothorax, commonly; others less so.
Many terms are also used to describe pleural space diseases - so let’s break them down.
First, let’s look at pleural effusion.
Pleural effusion is a generalised term for fluid accumulating in the pleural space. There are many different types of fluid, including:
Transudate: a low-protein, low cellularity fluid usually seen due to hypoalbuminaemia or right-sided congestive heart failure.
Modified transudate: similar to transudate but higher in protein/cellularity, potentially caused by things like neoplasia.
Exudate: a protein-rich and highly cellular fluid seen due to infection or inflammation.
Chylothorax: the accumulation of chyle within the pleural space. Chyle is a lymphatic fluid that appears milky white-pink and is high in triglycerides. It can be seen due to trauma or scarring/damage to the thoracic duct, but most cases are idiopathic.
Haemothorax: the accumulation of blood in the pleural space, usually from trauma or coagulopathies.
Pyothorax: the accumulation of pus in the pleural space, usually caused by parapneumonic spread, a migrating foreign body, or a penetrating wound (such as a bite).
Then there’s pneumothorax.
As the name suggests, with pneumothorax, air enters the pleural space. Causes include:
Trauma (dog attacks, RTAs)
Ruptured bullae or lung blebs (causing spontaneous pneumothorax)
Iatrogenic causes (such as thoracocentesis or barotrauma from excessive ventilation)
This air causes the lung or lungs to collapse, leading to respiratory compromise. This collapse will be full or partial, depending on how much pressure the air exerts on the lungs.
Lastly, we have diaphragmatic hernias.
These aren’t always classified directly as a pleural space disease. Still, they act like one, so the result for our patient is the same - compromised lung expansion and impaired oxygen delivery.
With a ruptured or herniated diaphragm, abdominal organs move into the thoracic cavity. This leaves less room for the lungs to expand, causing hypoventilation. The degree of hypoventilation (and therefore the severity of the patient’s signs) depends on how many organs have herniated, and to an extent, which ones they are. For example, if the stomach herniates and the patient eats, the stomach will increasingly decrease lung expansion.
Regardless of the underlying cause, the net result for our patient is the same: each of these causes will reduce lung capacity, impair ventilation, and can rapidly become life-threatening without intervention.
Ok, so those are the types of pleural space disease we see. But what clinical signs do they cause?
Most patients will present in respiratory distress, with classic clinical signs including:
Tachypnoea
Shallow respiration exhibiting a restrictive lung pattern, because the lungs cannot expand
Abdominal effort, since the chest cannot expand sufficiently
Orthopnoea, where patients adapt their body position to ease ventilation
Open-mouth breathing, especially in cats
Cyanosis in severe cases, though patients with pink mucous membranes can still be hypoxaemic!
Exercise intolerance, lethargy, and potentially collapse due to poor oxygen delivery.
On physical examination, muffled heart and lung sounds are commonly auscultated. The location of these muffled sounds indicates what could be causing the patient’s pleural space disease - dorsal muffling is more indicative of pneumothorax. In contrast, ventral sounds indicate pleural effusion more since gravity pulls that fluid down to the ventral thorax.
Once you suspect your patient has pleural space disease, how do you diagnose it?
Without sounding like a broken record, stabilisation is the first thing we need to prioritise.
Now, an oxygen and hands-off approach will only get you so far in patients with pleural space disease.
Of course, we need to minimise stress, provide anxiolytics and give them oxygen - they’re still on that knifedge, balancing their increased oxygen demand with decreased oxygen delivery - but until we allow the lungs to expand, we’re not really solving much.
This might mean we reach for some of our diagnostic procedures earlier than usual in a respiratory distress patient, especially in severe cases.
Draining something - even a small amount - from the chest will help improve lung expansion and ventilation if you can.
Ok, ok, stabilise first. But then what?
We’ll confirm our patient has pleural space disease (and which specific type they have) using a variety of tests, including:
Physical examination: listening for dull/muffled heart and lung sounds.
Thoracic radiographs: where you may see retracted lung lobes, fluid lines, free gas in the chest, or abdominal organs in the case of diaphragmatic rupture.
Thoracic ultrasound: an invaluable tool in pleural space disease, especially in dyspnoeic patients who can’t safely tolerate X-rays. You can visualise fluid, confirm a pneumothorax, and guide thoracocentesis.
Thoracocentesis: Sampling the pleural content is both diagnostic and therapeutic. As well as improving our patients’ condition, it also allows us to diagnose their underlying cause.
Fluid analysis: Always keep samples of fluid collected in both EDTA and plain tubes, and send them for cytology and culture. Look at the fluid in house, noting the colour, clarity, protein levels, cellularity and triglyceride levels, to determine your patient’s underlying disease.
Bloodwork: Haematology and biochemistry, coags, and other tests are often required to assess the patient’s general status and look for potential causes.
As nurses and technicians, our role in this is vast. We’re not just here to hold the patient for a thoracocentesis - there’s no reason we can’t be assisting with that procedure, performing imaging, looking at fluid and much more.
Providing careful patient support during these tests is essential if you assist with diagnosis: calm, quiet environments, oxygen on standby, and gentle restraint are vital, and don’t be afraid to ask the vet to stop if the patient isn’t coping.
And once you’ve got a diagnosis? It’s time to treat (and nurse) your patient.
Once we’ve confirmed pleural space disease, we need to plan our patient’s treatment and nursing care.
The specific treatments used will vary depending on the type of pleural space disease our patient has, for example:
Pneumothorax is usually self-sealing but can require lung lobectomy or pleurodesis in severe cases where centesis alone is not sufficient.
Haemothorax should not be managed with excessive thoracocentesis, since this can cause anaemia. Instead, the patient should have just enough pleural blood removed to improve their signs, and their underlying coagulopathy should be treated. The rest of the pleural blood will be reabsorbed over time.
Chylothorax patients often require surgery, undergoing pericardectomy and thoracic duct ligation.
Patients with pleural effusion due to congestive heart failure will require treatment with diuretics such as furosemide.
Pyothorax patients require drainage alongside appropriate antibiotics, and pleural lavage in some cases.
Aside from this, it’s all about keeping the pleural space empty, the lungs free to ventilate, and providing supportive care.
Depending on the severity of the patient’s pleural space disease, thoracocentesis alone may be enough, or indwelling chest drains (thoracostomy tubes) may be used. These require careful nursing management to keep them clean, patent, and complication-free.
Analgesia is also essential in these patients. Even if their disease process is not directly painful, their chest drain will be. Providing appropriate analgesia, ideally multimodally via a combination of opioids, non-opioid medications and potentially local anaesthesia via the chest drain, is essential.
There’s a lot to think about when nursing these patients, too.
This includes:
Ongoing respiratory monitoring, particularly looking at their respiratory effort, pattern and rate and their SpO2,
Performing chest drain care and management, noting the volumes and appearance of the content drained,
Recumbency care, where appropriate, to prevent atelectasis, further compromising lung function.
Nutritional support,
Client care and communication,
And much more.
And whilst these patients are complex and often challenging to nurse, there are a lot of skills we get to use whilst caring for them - from emergency triage and stabilisation, to assisting with chest drain placement, performing imaging and fluid analysis, providing oxygen and much more.
But above all, our ability to recognise the subtle and early signs of deterioration in these patients, support them during diagnostics, and advocate for their well-being makes us so critical to their recovery.
So there you have it - pleural space disease in a nutshell. We’ve looked at the common causes of pleural space disease, their impact on our patients, and our role in their diagnosis, treatment and care. And over the next few episodes, we’ll look at pneumothorax, pyothorax and a couple of others in much more detail.
I’ve also got some helpful chest drain management resources in the medical nursing library that you can access for free - head to the downloads page to grab them!
Did you enjoy this episode? If so, I’d love to hear what you think. Take a screenshot and tag me on Instagram (@vetinternalmedicinenursing) so I can give you a shout-out and share it with a colleague who’d find it helpful!
Thanks for learning with me this week, and I’ll see you next time!
References and Further Reading
Barrs, V.R. and Beatty, J.A., 2009. Feline pyothorax: a retrospective study of 27 cases in Australia. Journal of Feline Medicine and Surgery, 11(10), pp.803–810.
King, L.G. and Boag, A., 2007. Textbook of Small Animal Emergency Medicine. Iowa: Wiley-Blackwell.
Merrill, L. 2012. Small Animal Internal Medicine for Veterinary Technicians and Nurses. Iowa: Wiley-Blackwell.
Nelson, R.W. and Couto, C.G., 2020. Small Animal Internal Medicine. 6th ed. Missouri: Elsevier.
