Acute Respiratory Failure – Respiratory Medicine Y4

Acute Respiratory Failure – Respiratory Medicine Y4

# What is Acute Respiratory Failure (ARF)?

Acute Respiratory Failure (ARF) is a condition where the body cannot provide enough oxygen or eliminate enough carbon dioxide, leading to decreased oxygen in the blood and potentially increased carbon dioxide in the blood.

# Classification of ARF

ARF is categorized into two types:

• Type 1: Low PaO2 (partial pressure of oxygen in arterial blood).

• Type 2: Low PaO2 and high PaCO2 (partial pressure of carbon dioxide in arterial blood).

# What are PaO2 and SaO2?

• PaO2: The partial pressure of oxygen dissolved in arterial blood.

• SaO2: The oxygen saturation of hemoglobin in arterial blood.

# Factors Affecting Respiration

Respiratory function relies on three main factors:

• Pulmonary Ventilation (most common): The process of gas exchange between the lungs and the environment.

• Pulmonary Blood Circulation: The amount of blood circulating through the lungs.

• Diffusion Capacity Across the Alveolar-Capillary Membrane: The ability of gas exchange between the lungs and blood.

# Ventilation-Perfusion Mismatch

Normally, the ratio between ventilation (Va) and pulmonary blood flow (Q) is 0.8.

This mismatch often occurs in situations like:

• Pneumonia, Atelectasis, Pulmonary Airway Obstruction (reduced Va): Reduced air intake to the lungs.

• Shock, Pulmonary Embolism, Heart Failure (reduced Q): Reduced blood circulation through the lungs.

• Shunt: Blood passing through the lungs without gas exchange.

# Causes of ARF

ARF can be caused by various factors, categorized into four main groups:

• Nervous System:

• Central Nervous System (CNS) Damage: Traumatic brain injury, cerebral hemorrhage, meningitis, encephalitis, tuberculosis, brain abscess, Reye syndrome (brain-liver disease), sedatives, poisoning.

• Respiratory System:

• Pneumonia: Bacterial pneumonia, tuberculosis pneumonia, viral pneumonia.

• Pulmonary Airway Obstruction (PAO): Severe PAO, foreign body airway obstruction, pulmonary edema, drowning, acute respiratory distress syndrome (ARDS).

• Respiratory Muscles:

• Respiratory Muscle Paralysis: High body paralysis, Guillain-Barré syndrome, myelitis, spinal cord injury, myasthenia gravis, muscular dystrophy.

• Circulatory Failure (CF):

• Shock: Septic shock, anaphylactic shock, hemorrhagic shock.

• Pulmonary Embolism: Pulmonary embolism due to blood clots, pulmonary embolism due to fat.

# Diagnosis of ARF

• Clinical Examination: Dyspnea (shortness of breath), cyanosis.

• Paraclinical Examination: PaO2 < 60 mmHg and/or PaCO2 > 50 mmHg, SaO2 < 85%.

# Differential Diagnosis of ARF

ARF should be differentiated from:

• Hyperventilation due to metabolic acidosis, poisoning: Causes dyspnea due to increased ventilation.

• Dyspnea due to heart failure, kidney failure: Causes dyspnea due to reduced respiratory efficiency.

# Principles of ARF Management

• Ensure Ventilation: Provide oxygen, respiratory support with a ventilator if necessary.

• Ensure Blood Flow: Fluid replacement, hemodynamic adjustment.

• Correct Acid-Base Imbalance: Add alkali if needed.

• Treat the Underlying Cause: Manage the cause of ARF.

# Management of Children with Foreign Body Airway Obstruction

• Children > 2 years old: Apply the Heimlich maneuver (abdominal thrusts).

• Children < 2 years old: Apply chest thrusts.

# Oxygen Supply

• Indications: Cyanosis and/or SaO2 < 90% and/or PaO2 < 60 mmHg.

• Methods:

• Cannula: Soft nasal cannula made of silicone, FiO2 30-40%, 0.5-3l/p.

• Mask: FiO2 40-100%, 6-8l/p.

# Ensuring Ventilation Flow

• Oxygen Supply: Adequate oxygen supply.

• Hematocrit: Maintain hematocrit 30-40%.

• Fluid Replacement: Replace fluids adequately, manage electrolyte imbalance.

• Increased Cardiac Contractility: Use cardiac stimulants.

• Blood Pressure Elevation: Use blood pressure elevating drugs if needed.

# Signs Indicating the Need for Enhanced Ventilation

• Increased Respiratory Rate: Increased by 30-50% compared to the normal respiratory rate.

# Note

Acute Respiratory Failure is a dangerous condition that requires prompt management. Parents should take their child to a healthcare facility for examination and treatment.