week 3 Acute Respiratory Failure Quiz

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Questions and Answers

What is the definition of acute respiratory failure (ARF)?

A condition in which the respiratory system fails in one or both of its gas-exchange functions, namely oxygenation and elimination of Carbon Dioxide (CO2)

What are the conventional criteria for defining acute respiratory failure?

PaO2 < 60 mmHg and/or PaCO2 > 45 mmHg & pH < 7.35, or both

What is the normal range for PaO2 in arterial blood?

80-100 mmHg

What is the general treatment for acute respiratory failure?

Oxygen delivery through invasive ventilation, non-rebreather, or nasal specs, depending on the severity of the condition Signup and view all the answers

What are the two components of the respiratory system that can fail, leading to respiratory failure?

The lungs (gas exchange) and the ventilatory pump Signup and view all the answers

What is the difference between Type I and Type II respiratory failure?

Type I is lung failure, characterized by hypoxemia, while Type II is pump failure, characterized by hypercapnia Signup and view all the answers

What are the two main categories of causes of acute respiratory failure?

Intrapulmonary and extrapulmonary causes Signup and view all the answers

What are some common clinical features of acute respiratory failure?

Dyspnoea, tachypnoea, orthopnoea, inability to speak, and use of accessory muscles Signup and view all the answers

What is the most common cause of hypoxaemia in respiratory failure?

Ventilation-perfusion mismatch (V/Q mismatch) Signup and view all the answers

What are the determinants of gas exchange in the lungs?

Thickness of the alveolar-capillary membrane, surface area of the membrane, diffusion coefficient of the gas, and pressure difference between the two sides of the membrane Signup and view all the answers

What is the main difference between a shunt and dead space in V/Q mismatch?

A shunt is a region of low ventilation and normal perfusion, while dead space is a region of normal ventilation and low perfusion Signup and view all the answers

What is the main difference between Type 1 and Type 2 respiratory failure?

Type 1 has low PaO2 and normal or low pCO2, while Type 2 has low PaO2 and high pCO2 Signup and view all the answers

What is the primary goal of managing respiratory failure?

Maintain airway patency, optimise oxygen delivery, and identify and treat the underlying cause Signup and view all the answers

What is the priority in managing respiratory failure?

Maintaining airway patency and optimising oxygen delivery Signup and view all the answers

What is the main difference between stagnant hypoxia and anemic hypoxia?

Stagnant hypoxia is due to inadequate blood flow, whereas anemic hypoxia is due to insufficient amount of functional hemoglobin. Signup and view all the answers

What are the early and late respiratory features of hypoxia?

Early features: dyspnoea, tachypnoea, hyperpnoea. Late features: bradypnoea or agonal breathing. Signup and view all the answers

What are the effects of hypercarbia on the oxy-haemoglobin dissociation curve?

Hypercarbia shifts the oxy-haemoglobin dissociation curve to the right, decreasing the affinity of Hb for O2 and increasing unloading of O2 to the tissues. Signup and view all the answers

What are the clinical manifestations of hypercarbia at different levels of PaCO2?

At PaCO2 60-75mmHg: tachypnoea, dyspnoea, peripheral vasodilation. At PaCO2 80-100mmHg: asterixis, confusion, lethargy. At PaCO2 120-150mmHg: anaesthesia, DEATH. Signup and view all the answers

What is the main cause of Type II respiratory failure?

Hypoventilation. Signup and view all the answers

What is the effect of hypoxia on the cardiovascular system?

Early: tachycardia, mild hypertension. Late: bradycardia, hypotension, arrhythmias, and Angina. Signup and view all the answers

What is the effect of hypoxia on the neurological system?

Headache, restlessness, agitation, confusion, paranoia, combative behavior, loss of coordination, CNS depression, and coma. Signup and view all the answers

What is the effect of hypercarbia on the respiratory system?

Hypercarbia displaces alveolar O2, reduces PaO2, and increases pulmonary vascular resistance, leading to cor pulmonale (right heart failure) and myocardial dysfunction. Signup and view all the answers

whats the Mechanisms of hypoxaemia

Low Fraction of inspired oxygen (FiO2) V/Q mismatch Diffusion defect Signup and view all the answers

example of shunt

Pneumonia Pulmonary oedema Signup and view all the answers

example of dead space ventilation

Pulmonary embolism Signup and view all the answers

Determinates of Gas Exchange

The thickness of the membrane e.g., pulmonary fibrosis • The surface area of the membrane e.g., atelectasis • The diffusion coefficient of the gas (O2 has a lower molecular weight than CO2 and therefore can be expected to diffuse across the respiratory membrane faster) e.g., temperature • The pressure difference between the two sides of the membrane (alveoli and capillary) e.g. The partial pressure of oxygen in the alveoli is about 104 mm Hg, whereas its partial pressure in the blood of the capillary is about 40 mm Hg. Signup and view all the answers

What are the causes of hypoxia in acute respiratory failure?

Causes of Hypoxia Signup and view all the answers

Who is at risk of CO2 retention

COPD ▪Severe chronic asthma ▪Cystic fibrosis ▪Kyphoscoliosis ▪Neuromuscular disease ▪Obesity hypoventilation Signup and view all the answers

Management of Respiratory Failure-Failure to oxygenate

Oxygen therapy Maintaining lung volumes using alveolar recruitments strategies ▪PEEP / CPAP / *NHF Signup and view all the answers

Management of Respiratory Failure-Failure to ventilate

NIV / BiPAP / IPPV Signup and view all the answers

mechanisms' of hypercarbia

displaces alveolar o2 and decrese pao2 shifts OHD curve to the right decrease affinity of hb for o2 , increase unloading to tissues Signup and view all the answers

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Study Notes

Acute Respiratory Failure (ARF)

Defined as a condition in which the respiratory system fails in one or both of its gas-exchange functions: oxygenation and elimination of carbon dioxide
Classified into two types: Type I (Failure to Oxygenate) and Type II (Failure to Ventilate)

Type I Respiratory Failure: Failure to Oxygenate

Characterized by hypoxaemia (PaO2 < 60 mmHg)
Mechanisms of hypoxaemia: low fraction of inspired oxygen (FiO2), V/Q mismatch, diffusion defect
Causes: intrapulmonary diseases (COPD, pneumonia), extrapulmonary diseases (pulmonary oedema, cardiac failure), and others

Type II Respiratory Failure: Failure to Ventilate

Characterized by hypercapnia (PaCO2 > 45 mmHg) and usually accompanied by hypoxaemia
Caused by hypoventilation due to various factors such as central nervous system disorders, peripheral nervous system disorders, and others

Clinical Features of Acute Respiratory Failure

Variable and dependent on the underlying cause, degree of hypoxaemia, hypercarbia, and acidosis
Symptoms: dyspnoea, tachypnoea, orthopnoea, inability to speak, use of accessory muscles, intercostal retractions, paradoxical abdominal movement, noisy breathing, anxiety, restlessness, confusion, lethargy, and coma

Mechanisms and Features of Hypoxaemia

Defined as deficient oxygenation of arterial blood (PaO2 < 80 mmHg)
Causes: stagnant hypoxia, anaemic hypoxia, histotoxic hypoxia
Clinical features: respiratory, cardiovascular, neurological, and skin-related symptoms

Mechanisms and Features of Hypercarbia

Defined as deficient elimination of carbon dioxide (PaCO2 > 45 mmHg)
Causes: hypoventilation due to various factors
Clinical features: tachypnoea, dyspnoea, headache, restlessness, agitation, confusion, coma, and death in severe cases

Management of Respiratory Failure

General goals of therapy: maintain airway patency, optimise oxygen delivery, optimise CO and ensure adequate Hb, minimise oxygen demand, identify and treat the underlying cause, and prevent complications
Specific therapies: oxygen therapy, NIV, IPPV, PEEP, CPAP, and others

ABG Analysis and Interpretation

VBG and ABG normal values: pH, PvO2, PvCO2, HCO3-, BE
Interpretation of ABG results: assessment of oxygenation, ventilation, and acid-base status

Case Study

25-year-old female with mild SOB and chest pain, presented to ED with negative cardiac troponin level
ABG results: PaO2 = 70 mmHg, pH = 7.25, PaCO2 = 51 mmHg, HCO3- = 24 mEq/L
Diagnosis and management of acute respiratory failure

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