What Does Crackle In The Lungs Mean?

The lungs make many sounds, as you might expect. Some of these sounds are normal respiratory sounds, however there are certain noises that may mean something more is going on. This article can give you an insight into a subsection of these sounds crackles. 

Crackles in the lung are usually due to an accumulation of fluid. This fluid could come from various sources. The location, viscosity and volume of the fluid will give rise to various types of noises.

There’s a variety of causes for this fluid build-up, meaning there are multiple pathologies that can lead to crackling lungs. 

Introduction

What are lung sounds? 

As air moves in and out of our lungs, noises are generated. Much like if you had a pipe with multiple small balloons attached to the end of it. If you blew into that pipe and put a stethoscope along it you would hear the air whooshing around. So, there are noises that are considered normal when listening to the chest. In fact, if the chest was completely silent on auscultation, then we’d be concerned! These ‘normal’ noises within the lungs are referred to as vesicular breathing. The other form of ‘normal’ noises is bronchial breathing. This is commonly heard over the big airways within the chest (also known as the bronchi). 

What does crackle in the lungs mean?

Causes and risk factors

There are a variety of causes for crackles within the lungs. The main cause for crackles is some form of fluid accumulation. Common causes include:

• Pneumonia – this is a medical term that means there is an area of infection within the lungs
• Fluid in the lungs (pulmonary oedema) – there are a variety of causes for water in the lungs
• Inflammation – any inflammatory process occurring in the lungs or bronchi can lead to crackles

Infection in the lung is called pneumonia.¹ This occurs when there is a microorganism that has invaded the lungs and given rise to an infection there. These are usually caused by bacteria or viruses, however can also be caused by fungus in certain cases. Common risk factors for 

Pneumonia include: 

• Extremes of age (under 5 and above 65) 
• Being hospitalised
• Having a chronic illness 
• Being immunosuppressed¹

An immunosuppressed person is someone who has a weaker immune system. This can either be from birth (congenital), acquired throughout life or through treatment for other conditions.

Pulmonary oedema refers to the fluid buildup within the lung itself. The lung consists of alveoli which are small sacs filled with air. This is where gas exchange occurs. As such, we want these spaces to be filled with air and not fluid, as the fluid impedes the rate of gas exchange. Often pulmonary oedema is categorised as cardiogenic (originating from the heart) and non-cardiogenic (originating elsewhere) causes. 

Cardiogenic causes

• Congestive heart failure – the heart is unable to pump effectively. This leads to the heart not being able to move blood around properly.  Therefore blood remains in the respiratory system (the lungs and airways) for longer than it should, causing diffusion of fluid from the blood vessels into the alveoli
• Heart attacks – when a heart attack happens part of the heart muscle has decreased blood supply, leading to damage and sometimes death of that part. As a result the heart is no longer able to pump as effectively as prior to the heart attack
• Valvular disease – the heart has 4 chambers, with vessels attached to each of these chambers. There are valves between the upper chambers (atria) and the lower chambers (ventricles), as well as valves between the chambers and the arteries. In total there are 4 valves within the heart. If these valves are damaged or malfunctioning for any reason then this will obstruct the blood flow within the heart

There are a range of lifestyle factors that make heart failure more likely: smoking, high fat intake, high cholesterol intake and a sedentary lifestyle. Alongside these risk factors, there are certain conditions that are associated with heart failure: 

• Coronary artery disease
• Heart attacks
• High blood pressure
• Diabetes
• Obesity
• Valvular disease within the heart
• Heart muscle disease (e.g. cardiomyopathy)
• Birth defects of the heart
• Some respiratory diseases. 

Non cardiogenic causes 

• Acute respiratory distress syndrome – usually caused by severe infection, trauma to the lung or inhalation of toxins.
• Renal failure – the kidneys are responsible for filtering a lot of things out from the blood. If they fail then there will be an excess of fluid within the cardiovascular system, meaning that the load on the heart is increased. As a result some of this fluid will leak out into the lungs (and potentially other areas in the body). 
• High altitude pulmonary oedema – this is cause by a rapid ascent in altitude. 

Inflammation of the airways (bronchitis) is often seen in children, people exposed to materials that cause damage to the lungs or those who have immunosuppression. Bronchitis can be acute or chronic. 

Symptoms

If you have fluid instead of air in your lungs then you’ll have a few symptoms that may warrant investigation. Symptoms of fluid in the lungs include:

• Difficulty breathing 
• Shortness of breath
• Decreased exercise tolerance
• Tiring easily 
• A new cough
• Needing more pillows to sleep at night due to inability to lie flat
• Chest pain 

Of course, there are symptoms that may or may not be present depending on the cause of the crackles. For example if there is an infection you may also experience: 

• Fevers
• ausea
• Muscle aches
• Lethargy

Complications 

There can be various complications that arise from a buildup of fluid in the lungs. Mostly the complications vary depending on the underlying cause of the crackles. 

Diagnosis

The diagnostic process starts from the moment you walk into the doctor’s office. The doctor should take a history from you and examine your chest (including auscultation) to assess the respiratory system. They will record some observations, one of which should be your oxygen saturation. If this is low then this is an indicator that there is something wrong! They may also do an ECG at this stage to assess heart function. 

If they suspect there is something going on they will likely request some blood tests. The blood tests requested may differ based on what they think the underlying cause is, but usually consist of the following:

• Full blood count
• Urea and electrolyte
• Liver function tests
• Coagulation screen 
• CRP 
• BNP
• Arterial blood gas measurement 

They may request imaging of the chest if they hear crackles. It is common to start with a chest x-ray in order to visualise the lung. You can usually see if there is an area that has opacity (indicating an anomaly), and also assess the size of the heart. If there is an increase in opacity in the area where the crackles are heard then this can be indicative of a buildup in that area. If there is an enlarged heart this could indicate an element of heart failure. 

Usually this combination is enough to diagnose the condition, however if there is still some confusion then they may opt to organise a CT scan of your chest for further clarity. 

How does it feel having a crackle in the lungs?

The feeling will vary due to the cause of the crackles. Usually people will have difficulty breathing and struggle to exercise. If there is accumulation of fluid then you may struggle to lie flat, as this will make you feel like you’re drowning. If there’s an underlying infection then you may have symptoms similar to a cold, along with a cough which is bringing up phlegm. 

Treatment and prevention

Treatment is geared towards helping the underlying cause. For infective causes treatment is usually a course of antibiotics, as most causes of pneumonia are bacterial in nature. ¹

If there is an element of heart failure then the doctor is likely to commence you on medications to help the heart. There are a variety of medications that are designed to help with heart failure:^2,3 

• Beta-blockers – this helps to slow down the heart and helps decrease blood pressure
• Diuretics – these medications reduce the level of fluid in the body, therefore relieving pressure on the heart
• Anti-hypertensives – high blood pressure can increase the load on the heart, therefore giving anti-hypertensives can help to relieve the pressure
  • ACE inhibitors – cause vessels to relax and open (vasodilate), therefore reducing load on the heart 
  • Angiotensin-2 receptor blockers – similar effect of action as ACE inhibitors

Alongside the medication there are lifestyle factors that can be addressed to help prevent heart failure:⁴

• Stop smoking
• Reduce fat intake 
• Reduce salt intake
• Exercising regularly 

There can also be other interventions if there is a cause identified:

• Pacemakers – put in if the heart is not beating normally, helps to regulate the herat rate 
• Implantable cardioverter defibrillator – if you have an abnormal heart rhythm that has cause the heart failure
• Valve surgery – can be a replacement or a valve repair
• Coronary angioplasty or bypass-angioplasty is when a small balloon is used to open up arteries in the heart that have become blocked. A bypass is when a vessel is taken from another part of the body (commonly the leg) and used to divert blood around clogged arteries 

When to seek medical attention

If you are concerned that there has been a change to your normally accustomed chest sounds, then you should really seek medical attention. If you are experiencing symptoms such as those mentioned in this article you should get assessed. It may be crackles, but there could also be other causes for your symptoms. 

Summary

• There are various causes for crackles in the lungs, the most common being infection and pulmonary oedema
• If you are struggling with breathing, or have a sensation of drowning, then you should seek medical aid