RESPIRATORY FAILURE FINAL NOTES PPT.pptx
- 1. RESPIRATORY FAILURE PRESENTER: KUKUNDAKWE ONESIMUS FACILITATOR: DR. KISUULE IVAN
- 2. SCOPE • Introduction • Aetiology • Classification • Pathophysiology • Management
- 3. Introduction • Respiratory failure is a condition in which the respiratory system fails in one or both of its functions of gas exchange i.e oxygenation of mixed venous blood and removal of carbondioxide. • It is conventionally defined as an arterial PO2 less than 60mmHg, an arterial PCO2 more than 45mmHg, or both.
- 4. • Respiratory failure can be viewed as impaired gas exchange due to either pump(heart) or lung failure or both. • It is not a specific disease but can occur in the course of a number of conditions that impair ventilation, compromise the matching of ventilation and perfusion or impair gas diffusion.
- 5. EPIDEMIOLOGY • Incidence is about 360,000 cases per year in the US • 36% die during hospitalization • Morbidity and mortality rates increase with age and presence of comorbidities
- 6. Aetiology Causes of hypoxemic respiratory failure include; • Chronic obstructive pulmonary disease • Restrictive lung disease • Severe pneumonia • Atelectasis Conditions that lead to impaired diffusion • Pulmonary oedema • Acute lung injury/acute respiratory distress syndrome
- 7. • Causes of hypercapnic respiratory failure include; Conditions that lead to upper airway obstruction • Infection e.g epiglotitis • Laryngospasm • Tumours
- 8. Conditions that cause weakness or paralysis of respiratory muscles • Brain injury • Drug overdoze • Guillan-Barre syndrome • Muscular dystrophy • Spinal cord injury • Poliomyelitis • Multiple sclerosis • Chest wall injuries
- 9. CLASSIFICATION • Respiratory failure is divided into two pathophysiologic categories • TYPE I (Hypoxaemic respiratory failure) • This is due to failure of gas exchange function of the lungs which leads to hypoxaemia and normal/low carbondioxide levels.
- 10. PATHOPHYSIOLOGY • Two major pathophysiologic factors contribute to lower arterial pressure of oxygen: Mismatching of ventilation and perfusion. • Occurs when areas of the lung are ventilated but not perfused or when areas are perfused but not ventilated. The hypoxaemia associated with ventilation-perfusion disorders is often exaggerated by conditions such as hypoventilation and decreased cardiac output.
- 11. Impaired perfusion • Impaired diffusion describes a condition in which gas exchange between the alveolar air and pulmonary blood is impeded because of an increase in the distance for diffusion or a decrease in the permeability or surface area of the respiratory membranes to the movement of gases.
- 12. TYPE II (hypercapnic/hypoxaemic respiratory failure) • Is due to ventilatory failure impeding gas exchange between alveoli and pulmonary blood. • In the hypercapnic form of respiratory failure, patients are unable to maintain a level of alveolar ventilation sufficient to eliminate carbondioxide and keep arterial oxygen levels within normal range.
- 13. • Hypoventilation or ventilatory failure occurs when the volume of fresh air moving into and out of the lung is significantly reduced. • It is commonly caused by conditions outside the lungs. Hypoventilation has two important effects on arterial blood gases; • first it almost always causes an increase in PCO2 , the rise in PC02 is directly related to the level of ventilation (reducing the ventilation by one half causes doubling of the PC02).
- 14. • Second, it may cause hypoxeamia , although hypoxaemia caused by hypoventilation can be readily abolished by readily abolished by administration of supplemental oxygen. • Some patients have a combination of respiratory and ventilatory failure
- 15. CLINICAL FEATURES • Acute respiratory failure is usually manifested by varying degrees of hypoxemia and hypercapnia. The signs and symptoms of acute Respiratory failure include those of the underlying disease combined with those of hypoxemia and hypercapnia. • Hypoxemia is accompanied by increased respiratory drive and increased sympathetic tone. • Potential signs include cyanosis, restlessness, confusion, anxiety, delirium, fatigue, tarchypnoea, hypertension, cardiac arrhythmias, and tremors.
- 16. • The pulmonary vasculature constricts in response to low alveolar PO2 and if this is severe, it may result into right ventricular failure with manifestations such as jugular vein distension, and dependent oedema. Profound hypoxemia can cause convulsions, retinal haemorrhages and permanent brain damage. Hypotension and bradycardia are usually pre- terminal
- 17. • Raised levels of PCO2 greatly increases cerebral blood flow which results in headache, increased Cerebral Spinal Fluid pressure, and sometimes papilledema. Headache is due to dilation of cerebral vessels. • Additional indicators of hypercapnia include warm and flushed skin and hyperemic conjunctiva
- 18. • Hypercapnia produces nervous system effects similar to those of anaesthetic, such as progressive somnolence, disorientation and if left un treated coma. • Air hunger and rapid breathing occur when alveolar PCO2 levels rise to approximately 60- 75mmHg.
- 19. MANAGEMENT • Effective management requires prompt diagnosis and treatment of the underlying disorder. The treatment of respiratory failure focuses on correcting the problems causing impaired gas exchange when possible and on relieving hypoxemia and hypercapnia
- 20. • A number of treatment modalities including establishment of the airway, use of broncho- dilating drugs, Antibiotics for treatment of Respiratory Tract Infections • Hypoxemia resulting in impaired diffusion can be partially or completely corrected by administration of high concentration of oxygen.
- 21. • In this case, the high concentration of oxygen serves to overcome the decrease in diffusion by establishing a larger alveolar-to-capillary diffusion gradient. • Controlled oxygen therapy and mechanical ventilation are used in treating blood gas abnormalities associated with respiratory failure.
- 22. • When alveolar ventilation is inadequate to maintain PO2 or PCO2 levels, because of respiratory or neurologic failure, mechanical ventilation is life saving. • Very ill patients may require tracheal intubation and mechanical ventilation
- 23. • Close monitoring of Arterial Blood Gases is key to management of respiratory failure • Treatment with respiratory stimulants such as doxapram improves respiratory rate of patients with respiratory failure.
- 24. REFERENCES • Kumar. V., Abbas. A.K. and Aster.C.J. (2018). Basic pathology (10th ed.). Washington, DC. • Davidson. R.(2005). Principles and practices of medicine (20th ed.) • Ellen. L. and Banaski. J. (2010). Pathophysiology.(5th ed.). Riverport Lane, St. Mouris
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