Respiratory failure happens when the respiratory system fails to maintain adequate gas exchange, leading to low blood oxygen levels (hypoxemia) and potentially high blood carbon dioxide levels (hypercapnia). Understanding this condition requires knowledge of how normal respiration works and what can go wrong.
What is respiratory health?
The notion of “ideal health” suggests an opposite state of “impaired health,” an intermediate step between health and disease. However, tracking how individuals transition from ideal health to lung disease is complex because no longitudinal studies cover respiratory health across the lifespan.
While known factors like smoking and environmental exposures have been studied, recent research has uncovered additional risk factors. Yet, the absence of life-long studies makes it difficult to map out how these factors affect lung health over time.
A way to propose a model to better understand respiratory health over the lifespan. Central to this is pulmonary reserve (the peak lung function typically reached in early adulthood) and susceptibility (the risk of a faster decline in lung function later in life). Impaired respiratory health, characterized by reduced lung function, might serve as a precursor to chronic diseases like COPD or interstitial lung disease in some, but not all, individuals.
Lung function is recognized as a key indicator of respiratory health, but it’s rarely measured outside of those already diagnosed with a disease. This highlights the need for better early detection and monitoring.
Respiratory disease is a significant public health issue, affecting one in five people and being the third leading cause of death, behind cancer and cardiovascular diseases.
Diseases like lung cancer, pneumonia, and COPD contribute heavily to this statistic. Hospital admissions related to respiratory illness have been rising at a faster rate than other admissions, particularly during the winter months when non-elective admissions for respiratory conditions double, placing pressure on the NHS.
This piece underscores the importance of developing a more nuanced understanding of respiratory health, including risk factors and the transition from health to disease, to improve prevention and treatment strategies.
How Normal Respiration Works:
- Oxygen Intake: When we breathe in, oxygen from the air enters the lungs.
- Gas Exchange: Oxygen crosses over from the lungs into the blood, while carbon dioxide (a waste product produced by organs) moves from the blood into the lungs.
- Oxygen Transport: Oxygen-rich blood is transported by the heart to various organs.
- Carbon Dioxide Expulsion: We breathe out carbon dioxide, expelling it from the body.
Components Involved in Respiration:
- Lungs: Facilitate the exchange of gases.
- Heart: Pumps oxygenated blood to organs and returns deoxygenated blood to the lungs.
- Chest Respiratory Muscles: Aid in the mechanics of breathing.
- Brain: Regulates the rate and depth of breathing.
Causes of Respiratory Failure:
Respiratory failure can result from the dysfunction of any of these components. The most common causes are lung and heart disorders.
Lung Disorders:
- Chronic Obstructive Pulmonary Disease (COPD): Causes airflow obstruction, reducing oxygen intake and carbon dioxide expulsion.
- Asthma: Leads to airway constriction, making it difficult to breathe and exchange gases.
- Pneumonia: Infection that inflames the air sacs in the lungs, impeding gas exchange.
Heart Disorders:
- Heart Failure: The heart’s inability to pump blood effectively can result in inadequate oxygen delivery to the body and insufficient removal of carbon dioxide.
- Heart Attack: Can damage heart tissue, reducing its ability to support efficient gas exchange.
When any part of the respiratory process is impaired, it disrupts the balance of oxygen and carbon dioxide in the blood, leading to respiratory failure. This condition requires immediate medical attention to restore proper gas exchange and support the affected organs.
Types of Respiratory Failure
Respiratory failure can be categorized into two main types based on blood gas levels:
Type I Respiratory Failure:
- Definition: Low blood oxygen levels (hypoxemia) with normal or low blood carbon dioxide levels.
- Causes: This type is often caused by conditions that affect oxygen exchange but not necessarily carbon dioxide removal. Common causes include:
- Pneumonia
- Pulmonary oedema
- Acute respiratory distress syndrome (ARDS)
- Pulmonary embolism
Type II Respiratory Failure:
- Definition: Low blood oxygen levels (hypoxemia) with high blood carbon dioxide levels (hypercapnia).
- Causes: This type occurs when there is a problem with the mechanics of breathing or an issue with the control of breathing, leading to inadequate ventilation. Common causes include:
- Chronic obstructive pulmonary disease (COPD)
- Severe asthma
- Drug overdose (which can suppress the respiratory center in the brain)
- Neuromuscular disorders (such as amyotrophic lateral sclerosis (ALS) or muscular dystrophy)
Temporal Classification of Respiratory Failure:
Respiratory failure can also be classified based on how quickly it develops:
Acute Respiratory Failure:
- Onset: Develops within minutes to hours.
- Characteristics: Typically occurs in individuals with no underlying lung disease or in those with an acute worsening of their condition.
- Examples:
- Acute asthma attack
- Acute respiratory distress syndrome (ARDS)
- Severe pneumonia
Chronic Respiratory Failure:
- Onset: Develops over several days or longer.
- Characteristics: Usually found in individuals with underlying chronic lung diseases, where the body has partially compensated for the gradual decline in respiratory function.
- Examples:
- Chronic obstructive pulmonary disease (COPD)
- Interstitial lung disease
Acute on Chronic Respiratory Failure:
- Onset: A sudden or rapid worsening of respiratory function in someone with pre-existing chronic respiratory failure.
- Characteristics: Represents an acute exacerbation of a chronic condition, leading to significant deterioration in respiratory function.
- Examples:
- COPD exacerbation
- Infection in someone with pre-existing chronic lung disease
Understanding these types and classifications of respiratory failure is crucial for timely and effective management, ensuring appropriate treatment and interventions to stabilize the patient’s condition.
Causes of respiratory failure
Common causes of type I respiratory failure
- Chronic obstructive pulmonary disease (COPD).
- Pneumonia.
- Pulmonary oedema.
- Pulmonary fibrosis.
- Asthma.
- Pneumothorax.
- Pulmonary embolism.
- Pulmonary hypertension (high blood pressure in the blood vessels that supply the lungs).
- Cyanotic congenital heart disease.
- Bronchiectasis.
- Acute respiratory distress syndrome (ARDS): a life-threatening condition in which the lungs are unable to provide enough oxygen. It usually occurs as a complication of a serious existing health condition.
- Respiratory illness associated with HIV infection.
- Kyphoscoliosis.
- Obesity.
Common causes of type II respiratory failure
- COPD.
- Severe asthma.
- Drug overdose, poisoning.
- Myasthenia gravis.
- Polyneuropathy.
- Poliomyelitis.
- Muscle disorders.
- Head injuries and neck injuries.
- Obesity.
- Pulmonary oedema.
- Acute respiratory distress syndrome.
- Hypothyroidism.
Symptoms of Respiratory Failure
Respiratory failure can manifest slowly, leading patients to adapt by reducing physical activity, though it can also present with more acute symptoms. Common symptoms include:
- Shortness of Breath: Initially occurs with exertion but can progress to happening at rest and during sleep.
- Tiredness: Due to insufficient oxygen reaching the body’s organs.
- Cyanosis: A bluish tinge to the hands or lips, noticeable at rest and worsening with exertion.
- Confusion and Reduced Consciousness: Caused by low blood oxygen levels or high carbon dioxide levels.
- Symptoms of the Underlying Cause: Such as chest pain in heart disease, limb weakness in neurological disorders, or wheezing in asthma.
Clinical Assessment
Healthcare professionals may observe:
- High Respiratory Rate
- Cyanosis: Bluish tinge to lips and fingers.
- Restlessness, Anxiety, Confusion, Seizures, or Coma: Due to abnormal blood gas levels.
- Lung Sounds: Indicative of infection, fluid overload, or asthma.
- Right-Sided Heart Failure: Known as ‘cor pulmonale,’ characterized by fluid retention, enlarged liver, abdominal swelling, and leg swelling.
Diagnosis
Arterial Blood Gas Analysis: Essential for diagnosing respiratory failure by measuring blood oxygen and carbon dioxide levels. Typically, blood is drawn from the wrist, but alternative sites like the groin or elbow may be used if necessary.
Identifying the Underlying Cause
Investigations to determine the cause of respiratory failure include:
- Chest X-ray: Detects infection, fluid, or tumors.
- Blood Tests: Includes full blood count, kidney and liver function tests, and checks for anemia.
- Troponin Tests: Assesses recent heart damage, such as from a heart attack.
- Thyroid Function Tests: Identifies underactive thyroid contributing to respiratory failure.
- Spirometry: Measures lung volumes and capacities, especially in chronic cases.
- Echocardiography: Evaluates cardiac causes, like heart valve issues or heart failure.
Treatment
Immediate Hospitalization: Required for acute or newly diagnosed chronic respiratory failure, with potential admission to an intensive care unit for artificial ventilation and life support.
Chronic Management: Some patients with chronic respiratory failure can be treated at home, depending on severity, underlying cause, coexisting illnesses, and social circumstances.
Treatment Goals: Improve blood oxygen levels, reduce carbon dioxide levels, and address the underlying cause. Methods include:
- Oxygen Therapy: Administered via mask; lower levels may be needed for patients adapted to high carbon dioxide levels.
- Artificial Ventilation:
- Mechanical Ventilation: Invasive, involving sedation, paralysis, and a tube inserted into the trachea. Patients are weaned off once the underlying cause is treated.
- Non-Invasive Ventilation (NIV): Used for low blood oxygen and high carbon dioxide levels, especially in COPD patients. Also aids in weaning from mechanical ventilation.
- Extracorporeal Membrane Oxygenation (ECMO): Blood is oxygenated and carbon dioxide removed by an external machine; used in severe heart failure cases.
Additional Treatments: Steroids, antibiotics, and other medications based on the underlying cause. Palliative care may be needed for terminal cases.
Complications
Respiratory failure can lead to:
- Lung Complications: Pulmonary embolism, fibrosis, pneumothorax, chronic respiratory failure, ventilator dependence.
- Heart Complications: Heart failure, pericarditis, heart attack.
- Polycythemia: Increased red cell count, leading to blood clots.
- Neurological Complications: Prolonged low oxygen can cause irreversible brain damage, seizures, coma, or brain death.
- Prolonged Hospital Stay Complications:
- Hospital-acquired infections
- Malnutrition, requiring assisted feeding
- Complications from immobility: muscle wasting, pressure sores, deep vein thrombosis, depression
Prognosis
Outcomes depend on age, underlying cause, speed of diagnosis, presence of other illnesses, and complications. Some patients may deteriorate despite treatment and require palliative care.
Key preventive measures include:
- Smoking Cessation: Stopping or never starting smoking is crucial in preventing respiratory failure.
Understanding and managing respiratory failure effectively involves recognizing symptoms, timely diagnosis, appropriate treatment, and addressing underlying causes to improve patient outcomes.