History and exam
Key diagnostic factors
common
presence of risk factors
Common risk factors include tobacco use, young age, old age, respiratory system illness, injury or infection, cardiac failure, and hypercoagulable states.
direct trauma to the thorax and neck
Cervical spine injury may cause loss of nerve function to drive respiratory muscles. Chest and abdominal injuries can cause a pneumothorax, haemothorax, and/or pulmonary contusion. Chest and abdominal trauma can result in structural injury to the chest wall and diaphragm, resulting in poor respiratory function.
dyspnoea
The physiological need to breathe more vigorously to compensate for decreased tissue oxygen is an indication of hypoxaemia. Dyspnoea should be differentiated from hyperventilation that occurs with metabolic acidosis (diabetic ketoacidosis) and panic attacks.
confusion
Hypercapnic respiratory failure can cause central nervous system depression, which may present as confusion and somnolence. Decreased ventilation effort associated with exhaustion and fatigue is also associated with confusion and somnolence.
tachypnoea
Hypoxaemic respiratory failure often results in an increased effort to ventilate and extract the oxygen from air. A rapid respiratory rate (RR) is a sensitive indicator for respiratory distress, as this is one of the first physiological responses to hypoxia. If oxygen therapy is initiated and the RR normalises from a rapid rate, this adds further evidence to suggest a significant hypoxic state. As acute respiratory failure progresses, a patient may become fatigued and exhibit a decrease in respiratory rate. A decrease in respiratory rate, particularly with the development of somnolence, which is probably due to hypercapnia, is a serious sign of impending respiratory failure and arrest.
accessory breathing muscle use
Use of the abdominal and neck muscles to augment chest expansion indicates severe respiratory distress.
stridor
May be suggestive of a possible upper airway obstruction. Airway obstruction can result from a foreign body, infection, tumour, secretions, anaphylaxis, or external mass.
inability to speak
May be suggestive of a possible upper airway obstruction. Airway obstruction can result from a foreign body, infection, tumour, secretions, anaphylaxis, or an external mass.
May also occur in patients with extreme dyspnoea without upper airway obstruction (e.g., severe asthma).
retraction of intercostal spaces
Occurs in respiratory distress of any cause, including upper airway obstruction.
cyanosis
Acute or chronic cyanosis can develop as blood oxygenation decreases. Central cyanosis (examined under the tongue) occurs first and can progress to peripheral cyanosis (seen on the face, neck, and extremities).
uncommon
loss of airway/gag reflex
Revealed using tongue depressor or laryngoscope blade. Indicates the need for emergency intubation.
Other diagnostic factors
common
anxiety
Lack of oxygen delivery to the brain can result in anxiety and agitation. Patients suffering hypoxaemia often feel non-specific anxiety and fear.
headache
Non-specific but frequent in both hypoxaemic and hypercapnic respiratory failure. Hypercapnic respiratory failure can cause cerebral vascular dilation and increased intracranial pressure.
hypoventilation
Patients with severe hypercapnia often appear comfortable and resting while actually progressively hypoventilating.
People using drugs with respiratory depressant effects may hypoventilate and have decreased levels of consciousness. The drugs most commonly associated with hypoventilation are opioids.
cardiac rhythm disturbances
Acute hypoxaemic respiratory failure causes physiological increases in heart rate to increase blood flow and oxygen delivery to tissues. Prolonged hypoxaemia can cause bradycardia and myocardial irritability with ventricular ectopy. Hypercapnic states can cause direct myocardial depression with bradycardia and ventricular ectopy.
Patients with long-standing pulmonary disease may develop chronic atrial dysrhythmias and cor pulmonale.
uncommon
underlying neuromuscular disorder
Decreased ventilation from limited chest expansion can be due to a number of neuromuscular disorders, including myasthenia gravis, polyneuropathy, motor neuron disease, poliomyelitis, and muscular dystrophy.
drug use
Accidental or intentional respiratory depression from opioid and sedative drugs can lead to acute respiratory failure.
seizure
Marked cerebral hypoxia can cause seizures.
coma
Marked cerebral hypoxia and/or hypercapnic respiratory failure that results in severe respiratory acidosis can depress the central nervous system and cause coma.
asterixis
Tremor of the wrist can be a sign of hypercapnia.
papilloedema
Hypercapnia induces cerebral vascular dilation and increased intracranial pressure, causing reversible papilloedema.
Risk factors
strong
cigarette smoking
Smoking cigarettes, cigars, and pipes is a major risk factor for respiratory disease and respiratory failure, resulting in premature death in the US.[16]
Direct or secondary exposure to cigarette smoke is associated with pulmonary disease and secondary risk for respiratory failure. Data are poor and inconsistent with regard to possible risk for smoking cannabis or inhaling vaporised nicotine.[17][18]
young age
Respiratory failure can occur at any age, but is most common in young people and older adults.
Children of younger age and older people are prone to infections affecting the respiratory system, which predisposes them to respiratory failure.
older age
Respiratory failure can occur at any age, but is most common in children and older adults.
Children of younger age and older people are prone to infections affecting the respiratory system, which predisposes them to respiratory failure.
Older patients often have decreased pulmonary capacity and can develop chronic pulmonary conditions that increase the risk for respiratory failure.
Older people are particularly at risk for accidental drug-induced respiratory depression and failure.
pulmonary infection
Acute respiratory failure is commonly associated with viral respiratory infection (e.g., influenza, COVID-19), as well as bacterial, or rarely fungal, pneumonia. Pneumonia can result in acute hypoxaemic respiratory failure by infiltration of alveoli. Similarly, viral respiratory infections can cause alveolar dysfunction. Infections of the upper airways can lead to obstruction of airflow and hypercapnic respiratory failure.
Older persons and those with chronic diseases that affect the immune system are at higher risk for development of acute respiratory failure with COVID-19.[19] COVID-19 infection may also cause myocardial injury that can result in cardiogenic shock and subsequent acute respiratory failure.[20]
chronic lung disease
COPD, cystic fibrosis, and asthma are major risk factors for respiratory failure, as they increase both susceptibility to pulmonary infection and risk of lower airway obstruction. Patients with poorly controlled or highly reactive asthma are at risk of respiratory failure. Asthma complicated by acute viral/bacterial respiratory infections has a higher risk of progressing to respiratory failure. Patients with chronic lung disease are at risk of respiratory failure. Often stable chronic lung disease will be made acutely worse from respiratory infection or cardiac failure. Chronic lung disease also predisposes to pulmonary embolism, which may lead to acute respiratory failure.
upper airway obstruction
Upper airway obstruction may occur from mechanical or structural causes. Structural causes in the upper airway can include retropharyngeal abscess, epiglottitis, and swelling due to acute allergy or anaphylaxis. Mechanical causes can include obstruction from food or accidentally inhaled foreign bodies. Acute upper airway obstruction can inhibit airflow into the lungs and cause respiratory failure. Lower airway obstruction from chronic lung disease is more common.
lower airway obstruction
Asthma affects the lower airways and is a common cause of acute respiratory failure. Inflammation and secretions cause obstruction of intermediate and small airways. This leads to inhibited pulmonary gas exchange and can result in hyperinflation of the chest, leading to further inefficient ventilation. Cystic fibrosis and bronchial inflammation and infection are also forms of lower airway obstruction.
alveolar abnormalities
The surface area available for gas exchange is reduced when there is destruction or infiltration of alveoli. Examples include emphysema, pneumonia, pulmonary oedema, pulmonary haemorrhage, Goodpasture's syndrome, granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis), and trauma. In addition, aspiration of stomach contents or fluids can interrupt alveolar surface gas exchange.
perfusion abnormalities
Conditions such as hypovolaemia, shock, and severe anaemia may lead to poor perfusion of the brain, heart, and lungs and can result in respiratory failure.
cardiac failure
Chronic and acute cardiac failure with secondary pulmonary oedema or low flow states can cause respiratory failure secondary to alveolar dysfunction.
peripheral nerve abnormalities
Neurological conditions such as Guillain-Barre syndrome, myasthenia gravis, and amyotrophic lateral sclerosis can inhibit respiratory muscle function and cause respiratory failure.
muscle system abnormalities
Conditions such as muscular dystrophy can inhibit respiratory muscle function and cause respiratory failure.
opioid and sedative medicines
Toxicity and overdose by these types of medicine may decrease respiratory drive and result in hypoxic respiratory failure.
toxic fumes and gases
The inhalation of substances such as chlorine, smoke, carbon monoxide, and hydrogen sulfide can cause damage to the upper airway, lower airway, or alveoli.
traumatic spinal injury
Spinal injuries can result in phrenic nerve damage, leading to a lack of ability to ventilate due to inadequate respiratory muscle function.
traumatic thoracic injury
Injuries including rib fractures, penetrating lung injuries, penetrating pulmonary vasculature injuries, diaphragmatic injury, and pulmonary contusion may result in a number of abnormalities that can lead to respiratory failure.
central nervous system (CNS) disorders
Cancers of the CNS, head injury, direct brain injury, infections, primary CNS disorders, and stroke may result in loss of respiratory drive, causing respiratory failure.
acute vascular occlusion
Pulmonary artery embolisation may lead to insufficient blood flow to functioning alveoli, causing ventilation-perfusion mismatch.
pneumothorax
Typically causes respiratory failure in the presence of underlying pulmonary dysfunction. Insufficient lung reserve can lead to respiratory failure. Bilateral pneumothoraces can cause catastrophic respiratory failure and rapid cardiac arrest.
hypercoagulable states
Previous pulmonary embolism, deep venous thrombosis, and/or family or known individual history of hypercoagulable states (e.g., inherited protein deficiencies, antiphospholipid syndrome, systemic lupus erythematosus) increase the risk of acute pulmonary embolism, which can lead to respiratory failure.
weak
pulmonary effusion
Effusions due to infection, malignancy, trauma, cardiac failure, and collagen vascular disease may compress pulmonary tissues and cause respiratory failure.
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