Introduction

Respiratory failure is a complex medical condition that occurs when the respiratory system is unable to perform its vital functions, of providing oxygen from the lungs into the bloodstream to be carried to the rest of the body. Any irregularities in the function of these fundamental components, including failure to remove carbon dioxide from the body may result in respiratory failure. Understanding respiratory failure is crucial because it can be a life-threatening condition that can make it difficult for a person to breathe on its own. It can be caused by various factors such as lung diseases, trauma, infections, and drug overdose. Recognising the signs and symptoms of respiratory failure and seeking prompt medical attention can be life-saving Respiratory failure can be acute, occurring suddenly and requiring immediate medical attention or it can be chronic, caused by an ongoing condition that develops over time. The chronic type may require long-term treatment.

Normal respiratory function

The respiratory system is an intricate network of organs and tissues that work together to facilitate the exchange of gases between the body and the environment. It is composed of numerous essential components, including the lungs, trachea, bronchi, bronchioles, alveoli, and diaphragm.

The trachea, bronchi, and bronchioles are responsible for forming the airways that transport air to and from the lungs. These airways are lined with a layer of mucus, which helps to filter out harmful particles and prevent them from entering the bloodstream.

The alveoli, which are the tiny air sacs in the lungs, play a crucial role in gas exchange. Oxygen from the air that we breathe diffuses across the walls of the alveoli and into the bloodstream, where it is transported to the cells of the body. At the same time, carbon dioxide, a waste product of cellular respiration, diffuses out of the bloodstream and into the alveoli, where it can be exhaled.

The diaphragm, a large muscle that separates the chest cavity from the abdomen, is responsible for regulating the volume of the chest cavity and the flow of air in and out of the lungs. When we inhale, the diaphragm contracts and flattens out, which causes the chest cavity to expand and air to be drawn into the lungs. When we exhale, the diaphragm relaxes back into its original position, which causes the chest cavity to decrease in volume and air to be pushed out of the lungs.

Types of respiratory failure

There are two main types of respiratory failure, Type 1 and Type 2.

Type 1 respiratory failure: which is also called hypoxemic respiratory failure arises when the oxygen levels in the blood are low (hypoxemia).¹ This is usually triggered by a problem with the lungs themselves. This type can be caused by the following factors

• Diffusion defect, resulting from lung diseases such as emphysema and interstitial lung disease (ILD)
• Low atmospheric pressure, which occurs at high altitudes
• Ventilation/perfusion mismatch (when the airflow/ blood flow in the lungs is impaired)

Type 2 respiratory failure: which is referred to as hypercapnic respiratory failure, occurs when the respiratory system is unable to effectively remove carbon dioxide from the body, resulting in high levels of carbon dioxide (CO₂) in the body (hypercapnia). This can be triggered by a problem with the lungs or the muscles involved in breathing. Common causes of type 2 respiratory failures include 

• Respiratory pump failure - The respiratory pump consists of the chest wall, pulmonary parenchyma (thin-walled alveoli, creating an enormous surface area which functions to retain proper gas exchange), the muscles of respiration, as well as the central and peripheral nervous systems
• Increased CO₂ production – when your breathing is unable to keep up with the need to exhale CO₂ from the body this results in high CO₂ levels in the blood¹

Causes and risk factors of respiratory failure

There are several different factors (differential diagnosis) that can lead to respiratory failure.

• Chronic obstructive pulmonary disease (COPD) - This is a progressive lung disease that makes it difficult to breathe. It includes conditions such as chronic bronchitis and emphysema. COPD is usually caused by long-term exposure to cigarette smoke
• Asthma - is a chronic lung disease that causes inflammation and narrowing of the airways, leading to difficulty breathing and wheezing
• Pneumonia - is a lung infection that can cause inflammation and fluid buildup, resulting in difficulties breathing
• Acute respiratory distress syndrome (ARDS) - is a severe lung condition caused by infection, injury, or trauma. It results in fluid buildup in the lungs
• Pulmonary embolism – this typically occurs when a blood clot travels to the lungs and blocks blood flow, leading to difficulty breathing and potentially respiratory failure
• Neuromuscular diseases – this refers to diseases such as; muscular dystrophy and amyotrophic lateral sclerosis (ALS) that affect the nerves and muscles involved in breathing
• Chest wall deformities - abnormalities in the structure of the chest wall, such as scoliosis, can make it difficult to breathe and lead to respiratory failure
• Drug overdose - certain medications or illicit drugs can weaken the respiratory system and cause respiratory failure
• Muscle abnormalities - abnormalities in the muscle function and anatomy such as diaphragmatic paralysis and muscular dystrophy can reduce the functionality of the respiratory pump, resulting in hypoventilation

It is important to note that respiratory failure can be caused by a combination of factors, and some people may be more susceptible to developing it due to underlying health conditions or lifestyle factors. Age is commonly reported as a risk factor for respiratory failure, with the population over 65 years at risk of developing ARDS. Premature infants are also at risk of respiratory distress syndrome which occurs when the lungs are not fully developed and are unable to provide enough oxygen, causing breathing difficulties, it is a major cause of mortality in premature infants. 

Signs and symptoms

Respiratory failure type 1 (Hypoxemia)

• Shortness of breath
• Confusion
• Irritability
• Drowsiness
• Fast heart rate
• Irregular heartbeat
• Short fast and shallow breathing
• Cyanosis – when the skin, lips and nails turn blue due to lack of oxygen

Respiratory failure type 2 (Hypercapnia)

• Behavioural changes
• Headaches
• Coma
• Warm extremities
• Asterixis - when muscles suddenly relax or lose tension involuntarily
• Papilloedema – swelling of the optic disc, due to increased intracranial pressure

Other signs and symptoms from underlying diseases:

• Fever
• Cough
• Production of mucus
• Chest pain
• Medical history of sepsis (when the body responds inappropriately to an infection, potentially leading to tissue damage and organ failure)
• Polytrauma – trauma patients with multiple injuries in various parts of the body¹

Diagnosis

Due to respiratory failure being caused by a multitude of health problems, there is no single algorithm for assessment. Suitable diagnostics may include a combination of a physical examination and laboratory analyses such as:

• Complete blood count – used to check overall health
• Infectious workup – a test that can identify bacteria or fungi causing an infection in the blood
• 12-lead electrocardiogram - a test that detects electrical activity of the heart, which can also be used to detect respiratory abnormalities
• Arterial blood gas sample - a blood sample from an artery, which provides precise information on the capacity of the respiratory system to exchange oxygen and carbon dioxide

Treatment and management

Respiratory failure treatment should be directed towards the underlying cause. Supportive measures on airway management must be put in place to maintain sufficient ventilation and rectify blood gas abnormalities. Initial management of patients with acute respiratory failure must begin with assessing their airway, breathing, and circulation. 

Hypoxemia correction

 The main aim is to sustain sufficient levels of oxygen in the tissues. Uncontrolled oxygen supplementation can lead to oxygen toxicity and CO₂ narcosis (drowsiness).

• Based on the clinical situation oxygen can be delivered via face mask, nasal cannula or high-flow nasal cannula
• Stubborn non-responsive cases may require extracorporeal membrane oxygenation (a machine that pumps and oxygenates blood outside the body)

Hypercapnia correction

Treating the underlying cause or providing ventilatory support can accomplish this. Patients with severe acute respiratory failure are usually intubated (inserting a tube into a patient's mouth or nose down into their windpipe). The aim of ventilatory support in respiratory failure is to:

• Correct hypoxemia
• Correct acute respiratory acidosis (when CO₂ builds up quickly before the kidneys can return to a state of balance)
• Allow ventilatory muscles to rest
• Some cases can be treated with non-invasive respiratory support - ventilatory support without intubation, for patients with mild to moderate respiratory failure

Prevention

• Smoking Cessation
• Seeking medical advice at early signs of a bacterial infection, cough, fever or mucus production
• Getting enough exercise to enhance lung function

Summary

Respiratory failure is a complicated condition that occurs when the respiratory system is unable to perform its vital functions. There are two types of respiratory failure: type 1 and type 2. Type 1 arises when the oxygen levels in the blood are low and is referred to as hypoxemic respiratory failure. The other, type 2 respiratory failure, occurs when the respiratory system is unable to effectively remove carbon dioxide from the body, resulting in high levels of carbon dioxide and referred to as hypercapnic respiratory failure.

Several different factors can lead to respiratory failure, with some people being more susceptible to developing it due to underlying health conditions or lifestyle factors. Effective treatment should be directed towards the underlying cause. However, prevention can be obtained by, stopping smoking, exercising enough to enhance lung function and seeking medical help during early signs of a bacterial infection, cough, fever or mucus production.