Introduction

Acute respiratory failure is a severe medical condition characterised by the inability of the lungs to adequately exchange oxygen and carbon dioxide. This failure leads to severe hypoxemia (low blood oxygen levels) or hypercapnia (high carbon dioxide levels), causing significant risks to life.¹ Identifying the early symptoms of acute respiratory failure is crucial for timely intervention and treatment. This article aims to inform about the early signs of acute respiratory failure in adults.

Overview of acute respiratory failure        

Acute respiratory failure can occur suddenly. It happens when the body cannot maintain adequate gas exchange in the lungs, leading to severe hypoxemia or hypercapnia. It is important to identify and address this condition at the earliest, or else it can become life-threatening.¹

Certain populations are more susceptible to developing acute respiratory failure. Those at-risk include:¹

• Elderly patients
• Individuals with chronic lung disease
• Immunocompromised patients
• Patients with cardiovascular disease
• Post-surgical patients
• Those who have suffered from the coronavirus (COVID-19) infection

Other risk factors include certain medical conditions, such as chest or back injuries, smoking, substance abuse, and the use of certain medications during surgeries, including anaesthesia.¹

Causes of acute respiratory failure

Understanding the etiological factors of acute respiratory failure is essential in identifying early symptoms. Common causes of this condition include hypoxemia, hypercapnia, and acute respiratory failure in perioperative patients or those who experience shock. 

Hypoxemia 

Hypoxemia happens due to the lung’s inability to supply adequate oxygen to the body. The primary reason for this failure is often impaired gas exchange. It is associated with various conditions such as severe pneumonia, acute respiratory distress syndrome (ARDS), emphysema, interstitial lung disease, chronic obstructive pulmonary disease (COPD), and pulmonary embolism.¹

Hypercapnia 

Hypercapnia occurs when the lungs are incapable of effectively removing carbon dioxide from the body, leading to elevated levels of blood carbon dioxide. It often results from respiratory pump failure and is commonly associated with conditions affecting the respiratory muscles, the central nervous system, or neuromuscular conditions. These conditions include:¹

• Encephalitis
• Stroke 
• Guillain-Barré syndrome 
• Amyotrophic lateral sclerosis 
• Myasthenia gravis 
• ARDS
• Bronchitis 
• Bronchiectasis 
• Ruptured diaphragm
• Kyphoscoliosis

Acute respiratory failure in perioperative patients 

Several factors like atelectasis, bronchospasm, pulmonary aspiration, and anaesthetic effects are among the more frequent causes of acute respiratory failure in perioperative patients.²

Acute respiratory failure from shock

This critical condition is often linked to sepsis or septic shock. It happens due to a combination of cardiovascular conditions, pulmonary oedema, and impaired gas exchange.³

Early symptoms of acute respiratory failure

Identifying the initial symptoms of acute respiratory failure is very important. While the specific clinical manifestations vary depending on the underlying cause, the common early indicators include:

Breathing difficulties

Shortness of breath 

Shortness of breath (dyspnea) is often the most noticeable symptom. Patients usually present with laboured breathing. They experience increased effort in breathing and a subjective sense that they cannot get enough air. These symptoms indicate respiratory distress and can be seen at rest or with exertion.⁴

Increased respiratory rate 

An increased respiratory rate (tachypnea) is an early indicator of this condition and is defined as a rapid breathing rate that is higher than normal. In response to reduced oxygen levels, the body often compensates by increasing the respiratory rate. This compensatory mechanism to cope with the inadequate oxygen supply indicates that the patient is progressing towards respiratory failure.⁴

Use of accessory muscles

The body makes use of additional muscles to assist with breathing. The muscles of the neck, shoulders, and upper chest work to help the diaphragm and intercostal muscles with inhalation and exhalation. Patients present with signs of retractions (visible contraction of the muscles and tissues located between the ribs as they pull inward with each breath). It indicates that the patient is having difficulty in breathing and is advancing to respiratory failure.⁴

Orthopnea

Orthopnea is the shortness of breath that occurs when a person is lying flat and is relieved by sitting or standing up. It is often seen in patients with underlying conditions such as cardiovascular and chronic lung diseases.⁴

Paroxysmal nocturnal dyspnea (PND)

PND is a sudden and severe shortness of breath that typically occurs during the night, indicating an underlying cardiac or pulmonary condition.⁴

Oxygen deprivation (hypoxemia) symptoms

Cyanosis

Cyanosis happens when oxygen saturation levels decrease significantly, causing bluish discolouration of the skin, particularly visible on the lips, face, and extremities. This symptom reflects severe hypoxemia and signals that the body tissues are not receiving sufficient oxygen.⁴

Confusion or altered mental status

Impaired oxygenation affects brain function, leading to confusion, disorientation, and restlessness. Patients exhibit difficulty concentrating, increased irritability, or lethargy. In severe cases, patients can become unresponsive. Altered mental status is often a sign that significant oxygen deprivation is occurring, necessitating immediate medical attention.⁴

Rapid heart rate (tachycardia)

Tachycardia is a significant clinical indicator of acute respiratory failure. The heart rate increases more than normal to compensate for oxygen deficiency. It reflects compensatory mechanisms during hypoxemia and indicates the severity of acute respiratory failure.⁴​

Carbon dioxide buildup (hypercapnia) symptoms

Headache

Headaches are an often-overlooked symptom of early respiratory failure. The buildup of carbon dioxide in hypercapnic respiratory failure can cause dilation of blood vessels in the brain, leading to pressure and discomfort. The headaches are commonly characterised as dull and persistent.⁴

Confusion and lethargy

Confusion and lethargy are nonspecific but common early signs of respiratory failure in both hypoxic and hypercapnic respiratory failure. It affects the central nervous system, causing fatigue, drowsiness and even carbon dioxide narcosis in severe cases.⁴

Flushed skin

It is an early visual indicator of this condition. Hypercapnia causes vasodilation that leads to redness of the skin. This occurs because dilation of peripheral blood vessels brings more blood to the surface of the skin, causing a flushed appearance, especially in the face.⁴

Asterixis

Asterixis is often seen in severe hypercapnia. It is a type of involuntary motor disorder characterised by sudden, brief, irregular jerking movements.⁴

Diagnostic approaches

Identifying symptoms such as rapid breathing, shortness of breath, rapid heart rate, and cyanosis is crucial for early diagnosis of acute respiratory failure and allows for timely intervention. The typical diagnostic approach includes:⁴

• Clinical evaluation - Detailed patient history and physical examination play an important role in the early diagnosis of acute respiratory failure. A thorough assessment enables clinicians to observe vital signs and clinical manifestations that indicate respiratory failure
• Arterial blood gas (ABG) test: ABG analysis plays a vital role in diagnosing acute respiratory failure. It provides critical details on arterial oxygen, carbon dioxide levels and acid-base disturbances. It helps differentiate between types of respiratory failure by indicating whether the patient is hypoxic or hypercapnic
• Oxygen saturation monitoring: Pulse oximetry is a vital non-invasive test that measures the oxygen saturation of haemoglobin in the blood. A saturation level below 90% is indicative of hypoxemia, necessitating further evaluation and intervention
• Radiography: Chest X-rays or computed tomography (CT) scans are used to assess potential causes of respiratory failure such as pneumonia, pulmonary oedema, or pleural effusions
• Pulmonary function tests (PFTs): PFTs provide information about the underlying chronic respiratory conditions contributing to acute respiratory failure

Management and treatment

Treatment of acute respiratory failure involves restoring respiratory function and addressing the underlying cause. Managing patients with acute respiratory failure involves assessing the airway, breathing, and circulation. Different treatment approaches include: ⁴

• Oxygen therapy is given for the treatment of hypoxemia
• Extracorporeal membrane oxygenation (ECMO) for patients not responding to conventional treatments
• Mechanical ventilation for severe patients to assist with breathing
• Medications such as bronchodilators, corticosteroids, antibiotics, diuretics, sedatives, and analgesics are administered based on the underlying cause
• Fluid management, positioning strategies and ensuring proper nutritional intake are also important aspects of effective management.

Prevention and monitoring

Preventive strategies involve managing risk factors and monitoring high-risk individuals. Key practices include:

• Continuous monitoring of vital signs, such as respiratory rate, heart rate, and oxygen saturation, in patients at risk for acute respiratory failure
• Managing underlying conditions like chronic pulmonary conditions and cardiovascular diseases

Summary

Acute respiratory failure is a potentially life-threatening condition that requires early identification and intervention. Symptoms such as dyspnea, tachypnea, use of accessory muscles, altered mental status, cyanosis, headache, and tachycardia serve as critical early indicators of respiratory failure. Certain populations are more susceptible to developing this condition, such as individuals with pre-existing conditions such as chronic lung disease, cardiovascular disease, or individuals on immunosuppressants. Different diagnostic methods are used in the early detection of symptoms, such as TFT, ABG test, and continuous monitoring of a patient’s vitals, which is essential for the timely diagnosis of this condition. Management of acute respiratory failure includes oxygen therapy, medications such as bronchodilators, corticosteroids, etc. and mechanical ventilation in severe cases. This article highlighted the importance of identifying early signs of acute respiratory failure for effective management and improving patient outcomes. Awareness, early detection, and timely action can make a significant difference in managing this life-threatening condition effectively.