What are the symptoms and treatment of acute respiratory failure?

Symptoms of Acute Respiratory Failure

Acute respiratory failure presents with dyspnea, tachypnea (respiratory rate >30 breaths/min), use of accessory muscles, inability to speak in full sentences, and altered mental status ranging from agitation to drowsiness—all indicating severe respiratory distress requiring immediate arterial blood gas analysis. 1

Cardinal Clinical Manifestations

Respiratory Symptoms

• Severe dyspnea is the hallmark symptom, often accompanied by dry cough or frothy sputum in cardiogenic pulmonary edema 2
• Tachypnea with respiratory rate >30 breaths/min indicates severe distress and impending failure 1
• Inability to speak in full sentences signals critical respiratory compromise 1
• Use of accessory muscles (sternocleidomastoid, intercostals) demonstrates increased work of breathing 1
• Paradoxical chest wall motion or abdominal breathing indicates respiratory muscle fatigue 1

Neurological Manifestations

• Altered mental status progressing from restlessness and agitation to confusion, drowsiness, and eventually obtundation 2, 1
• Deteriorating conscious level is a critical sign of treatment failure requiring immediate escalation to mechanical ventilation 1
• These neurological changes result from hypoxemia and hypercapnia affecting cerebral function 3

Cardiovascular Signs

• Pallor or cyanosis indicating severe hypoxemia 2
• Cold, clammy skin suggesting poor peripheral perfusion 2
• Blood pressure may be normal, elevated (in hypertensive acute heart failure), or low (in cardiogenic shock) 2
• Tachycardia is common as a compensatory mechanism 3

Physical Examination Findings

Pulmonary Auscultation

• Fine rales (crackles) audible over lung fields in left heart backward failure and pulmonary edema 2
• Expiratory wheezing ("cardiac asthma") may occur in cardiogenic pulmonary edema 2
• Decreased breath sounds may indicate pleural effusion or pneumothorax 3

Cardiovascular Examination

• Assess apex beat quality and location 2
• Listen for heart murmurs indicating valvular pathology 2
• Evaluate for jugular venous distension in right heart failure 2

Diagnostic Confirmation

The diagnosis of acute respiratory failure requires arterial blood gas (ABG) analysis showing PaO₂ <60 mmHg (8 kPa) and/or PaCO₂ >50 mmHg with pH <7.35, combined with clinical assessment. 1 The clinical manifestations alone are nonspecific, making ABG analysis essential for diagnosis 3.

Type Classification

• Type I (Hypoxemic) Respiratory Failure: PaO₂ <60 mmHg with normal or low PaCO₂ 1
• Type II (Hypercapnic) Respiratory Failure: PaCO₂ >50 mmHg with pH <7.35, often with hypoxemia 1

Critical Pitfalls to Avoid

• Do not rely on pulse oximetry alone for diagnosis, as patients with chronic CO₂ retention may have acceptable oxygen saturations despite severe hypercapnia 1
• Avoid targeting SpO₂ >92% in COPD patients, as excessive oxygen worsens V/Q mismatch and hypercapnia; target 88-92% instead 1, 4
• Recognize that symptoms are nonspecific; maintain high index of suspicion and obtain early ABG analysis 3
• Monitor for respiratory muscle fatigue indicated by decreasing respiratory rate with worsening hypercapnia and confusion—this mandates intubation 2

Immediate Assessment Requirements

• Obtain ABG, chest X-ray, electrocardiogram, and complete blood count immediately to identify underlying causes (pneumonia, pulmonary edema, pulmonary embolism, pneumothorax) 1, 4
• Repeat ABG after 1-2 hours of initial treatment to assess response 1
• If no improvement after 4-6 hours, consider escalation to invasive ventilation 1
• Monitor continuously with pulse oximetry for at least 24 hours, though this cannot replace ABG analysis 1