Acute Respiratory Failure Causes and Treatment

Acute Respiratory Failure

Etiology

• Respiratory Center Depression:
  • Drug overdose
  • Stroke
  • Trauma
  • Infection (e.g., meningitis, encephalitis)
• Lung Parenchyma Disease:
  • Pneumonia
  • Pulmonary edema
  • Pulmonary embolism
  • Asthma/COPD exacerbation
• Airway Obstruction:
  • Foreign body aspiration
  • Laryngeal edema
  • Tracheal stenosis
• Neuromuscular Disease:
  • Guillain-Barré syndrome
  • Myasthenia gravis
  • Amyotrophic lateral sclerosis (ALS)

Oxygenation Strategies

• Oxygen Therapy:
  • Low-flow oxygen (nasal cannula or mask)
  • High-flow oxygen (non-rebreather mask or helmet)
• Non-Invasive Ventilation (NIV):
  • Continuous Positive Airway Pressure (CPAP)
  • Bilevel Positive Airway Pressure (BiPAP)
• Invasive Mechanical Ventilation:
  • Volume-controlled ventilation
  • Pressure-controlled ventilation

Ventilator Settings

• Mode:
  • Assist-Control (AC) mode
  • Synchronized Intermittent Mandatory Ventilation (SIMV) mode
• Tidal Volume (VT):
  • 6-8 mL/kg ideal body weight
• Respiratory Rate (RR):
  • 12-20 breaths per minute
• Positive End-Expiratory Pressure (PEEP):
  • 5-15 cmH2O
• Fraction of Inspired Oxygen (FiO2):
  • 0.21-1.0

Pathophysiology

• Hypoxemic Respiratory Failure:
  • Inadequate oxygenation of the blood
  • PaO2 < 60 mmHg
• Hypercapnic Respiratory Failure:
  • Inadequate removal of carbon dioxide
  • PaCO2 > 50 mmHg
• Respiratory Acidosis:
  • pH < 7.35

Complications

• Respiratory Muscle Fatigue
• Pneumothorax
• Ventilator-Associated Pneumonia (VAP)
• Acute Respiratory Distress Syndrome (ARDS)
• Multi-Organ Dysfunction Syndrome (MODS)

Respiratory Infections

• Hospital-Acquired Pneumonia (HAP)
• Ventilator-Associated Pneumonia (VAP)
• Community-Acquired Pneumonia (CAP)
• Healthcare-Associated Pneumonia (HCAP)

ARDS

• Definition:
  • Acute onset
  • Bilateral infiltrates on chest radiograph
  • PaO2/FiO2 ratio < 200 mmHg
• Stages:
  • Mild ARDS: PaO2/FiO2 ratio 200-300 mmHg
  • Moderate ARDS: PaO2/FiO2 ratio 100-200 mmHg
  • Severe ARDS: PaO2/FiO2 ratio < 100 mmHg

Antibiotics

• Empiric Therapy:
  • Broad-spectrum antibiotics (e.g., ceftriaxone, vancomycin)
  • De-escalation to targeted therapy based on culture results
• Targeted Therapy:
  • MRSA: vancomycin or linezolid
  • Pseudomonas aeruginosa: anti-pseudomonal beta-lactam (e.g., piperacillin-tazobactam)
  • Gram-negative bacteria: fluoroquinolone or aminoglycoside

Acute Respiratory Failure

Etiology

• Respiratory center depression can be caused by drug overdose, stroke, trauma, or infection
• Lung parenchyma disease can lead to ARF due to pneumonia, pulmonary edema, pulmonary embolism, or asthma/COPD exacerbation
• Airway obstruction can cause ARF due to foreign body aspiration, laryngeal edema, or tracheal stenosis
• Neuromuscular disease can cause ARF due to Guillain-Barré syndrome, myasthenia gravis, or amyotrophic lateral sclerosis (ALS)

Oxygenation Strategies

• Oxygen therapy can be administered via low-flow oxygen or high-flow oxygen
• Non-invasive ventilation can be used, including continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP)
• Invasive mechanical ventilation can be used, including volume-controlled ventilation or pressure-controlled ventilation

Ventilator Settings

• Assist-control (AC) mode and synchronized intermittent mandatory ventilation (SIMV) mode are common modes used
• Tidal volume (VT) should be 6-8 mL/kg ideal body weight
• Respiratory rate (RR) should be 12-20 breaths per minute
• Positive end-expiratory pressure (PEEP) should be 5-15 cmH2O
• Fraction of inspired oxygen (FiO2) should be 0.21-1.0

Pathophysiology

• Hypoxemic respiratory failure occurs when PaO2 < 60 mmHg
• Hypercapnic respiratory failure occurs when PaCO2 > 50 mmHg
• Respiratory acidosis occurs when pH < 7.35

Complications

• Respiratory muscle fatigue, pneumothorax, ventilator-associated pneumonia (VAP), acute respiratory distress syndrome (ARDS), and multi-organ dysfunction syndrome (MODS) are possible complications

Respiratory Infections

• Hospital-acquired pneumonia (HAP), ventilator-associated pneumonia (VAP), community-acquired pneumonia (CAP), and healthcare-associated pneumonia (HCAP) are types of respiratory infections

ARDS

• ARDS is defined by acute onset, bilateral infiltrates on chest radiograph, and PaO2/FiO2 ratio < 200 mmHg
• Stages of ARDS include mild (PaO2/FiO2 ratio 200-300 mmHg), moderate (PaO2/FiO2 ratio 100-200 mmHg), and severe (PaO2/FiO2 ratio < 100 mmHg)

Antibiotics

• Empiric therapy involves using broad-spectrum antibiotics, which can be de-escalated to targeted therapy based on culture results
• Targeted therapy includes using vancomycin or linezolid for MRSA, anti-pseudomonal beta-lactam for Pseudomonas aeruginosa, and fluoroquinolone or aminoglycoside for Gram-negative bacteria

Respiratory Infections

• Pneumonia is an inflammation of the respiratory tract, often caused by bacterial or viral infections
• Community-acquired pneumonia (CAP) is acquired outside of healthcare settings
• Hospital-acquired pneumonia (HAP) is acquired in healthcare settings
• Ventilator-associated pneumonia (VAP) is acquired in patients on mechanical ventilation
• Other respiratory infections include bronchitis, bronchiolitis, sinusitis, and influenza

HAP/VAP/CAP

• Hospital-acquired pneumonia (HAP) has a high mortality rate of up to 50%
• HAP is often caused by multidrug-resistant bacteria such as MRSA and Pseudomonas
• Ventilator-associated pneumonia (VAP) has a high risk of mortality of up to 70%
• VAP is often caused by Gram-negative bacteria such as Pseudomonas and Acinetobacter
• Community-acquired pneumonia (CAP) is the most common cause of infectious disease-related hospitalization
• CAP is often caused by Streptococcus pneumoniae, Haemophilus influenzae, and viruses

Acute Respiratory Distress Syndrome (ARDS)

• ARDS is an acute inflammatory lung injury, characterized by bilateral infiltrates on chest X-ray, hypoxemia (PaO2/FiO2 < 200), and no evidence of heart failure or fluid overload
• ARDS can be caused by sepsis, pneumonia, trauma, aspiration, and pancreatitis
• The pathophysiology of ARDS involves increased permeability, inflammation, and damage to the alveolar-capillary membrane
• Treatment for ARDS includes supportive care, mechanical ventilation, and adjunctive therapies such as prone positioning and inhaled nitric oxide

Antibiotics

• Empiric therapy for respiratory infections involves broad-spectrum antibiotics, often including beta-lactams, macrolides, and fluoroquinolones
• De-escalation involves narrowing the antibiotic spectrum based on culture results and clinical response
• Antibiotic resistance is an emerging concern, particularly with Gram-negative bacteria such as carbapenem-resistant Enterobacteriaceae