Respiratory failure, acute
When the lungs can’t adequately maintain arterial oxygenation or eliminate carbon dioxide (CO2), acute respiratory failure results. Unchecked and untreated, the condition leads to tissue hypoxia. In patients with essentially normal lung tissue, acute respiratory failure usually produces a partial pressure of arterial carbon dioxide (Paco2) above 50 mm Hg and a partial pressure of arterial oxygen (Pao2) below 50 mm Hg.
These limits, however, don’t apply to patients with chronic obstructive pulmonary disease (COPD). These patients consistently have a high Paco2 level (hypercapnia) and a low Pao2 level (hypoxemia). So for patients with COPD, only acute deterioration in arterial blood gas (ABG) values—with corresponding clinical deterioration—signals acute respiratory failure.
Causes
Acute respiratory failure may develop from any condition that increases the work of breathing and decreases the respiratory drive. These conditions may result from respiratory tract infection (such as bronchitis or pneumonia), bronchospasm, or accumulated secretions secondary to cough suppression. Other common causes are related to ventilatory failure, in which the brain fails to direct respiration, and gas exchange failure, in which respiratory structures fail to function properly.
Complications
Tissue hypoxia, metabolic acidosis, lactic acidosis, multiple organ dysfunction, cardiac arrhythmias, and respiratory and cardiac arrest are among possible complications.
Assessment
Because acute respiratory failure is life-threatening, you probably won’t have time to conduct an in-depth patient interview. Instead, you’ll rely on family members or the patient’s medical records to discover the precipitating incident.
On inspection, you’ll note nasal flaring, ashen skin, and cyanosis of the oral mucosa, lips, and nail beds. You may observe the patient yawning and using accessory muscles to breathe. He may appear restless, anxious, depressed, lethargic, agitated, or confused. Additionally, he usually exhibits tachypnea, which signals impending respiratory failure.
Palpation may reveal cold, clammy skin and asymmetrical chest movement, which suggests pneumothorax. If tactile fremitus is present, you’ll notice that it decreases over obstructed bronchi or pleural effusion areas but increases over consolidated lung tissue.
Percussion—especially in patients with COPD—reveals hyperresonance. If acute respiratory failure results from atelectasis or pneumonia, percussion usually produces a dull or flat sound.
Auscultation typically discloses diminished breath sounds. In patients with pneumothorax, breath sounds may be absent. In other cases of respiratory failure, you may hear adventitious breath sounds such as wheezes (in asthma) and rhonchi (in bronchitis). If you hear crackles, suspect pulmonary edema as the cause of respiratory failure.
Diagnostic tests
ABG analysis is the key to diagnosis (and subsequent treatment) of acute respiratory failure. Progressively deteriorating ABG values and pH level—compared with the patient’s normal values—strongly suggest acute respiratory failure. In patients with essentially normal lung tissue, a pH below 7.35 usually indicates acute respiratory failure. In patients with COPD, the pH deviation from the normal value is even lower.
Chest X-rays identify underlying pulmonary diseases or conditions, such as emphysema, atelectasis, lesions, pneumothorax, infiltrates, and effusions.
Electrocardiography (ECG) can demonstrate arrhythmias. Common ECG patterns point to cor pulmonale and myocardial hypoxia.
Pulse oximetry reveals decreasing arterial oxygen saturation.
Blood test results, such as an elevated white blood cell count can indicate infection. Abnormally low hematocrit and hemoglobin levels signal blood loss, which indicates decreased oxygen-carrying capacity.
Serum electrolyte findings vary. Hypokalemia may result from compensatory hyperventilation, the body’s attempt to correct alkalosis; hypochloremia usually occurs in metabolic alkalosis.
Pulmonary artery catheterization helps to distinguish pulmonary and cardiovascular causes of acute respiratory failure and monitors hemodynamic pressures.
Additional tests, such as a blood culture, Gram stain, and sputum culture, may identify the pathogen.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
