Respiratory failure & Cor Pulmonale

1. Respiratory failure&CorPulmonale Dr SD Maasdorp

2. Introduction • Primary function of respiratory system: • Supply O2 to blood • Remove CO2 from blood

3. Introduction cont… • Adequate gas exchange require: • Ventilation • Perfusion • Diffusion • Ventilation-perfusion matching

4. Definitions • Respiratory failure: • Failure of lungs to oxygenate arterial blood adequately and/or prevent CO2 retention • Not a primary disease, but syndrome caused by many different diseases

5. Respiratory failure Type 1 (Hypoxemic) Type 2 (Hypercapnic) Acute Chronic Acute Chronic

6. Definitions cont… • Acute: • Develops in minutes to hours • Chronic: • Develops over several days or longer • Types: • Type 1(hypoxemic): • PaO2 < 60 mmHg, PaCO2 N/↓ • Type 2(hypercapnic): • PaO2 < 60 mmHg, PaCO2> 50 mmHg (Acute – pH ↓, Chronic – pH normal)

7. Causes of ↓PaO2 • Decreased inspired PO2 • Hypoventilation • Diffusion impairment • Shunt • Ventilation-perfusion mismatch

8. Causes of ↑PaCO2 • Hypoventilation • Ventilation-perfusion inequality

9. Hypoventilation A: Impaired respiratory drive: • Peripheral and central chemoreceptors: • Carotid body dysfunction • Metabolic alkalosis • Brainstem respiratory neurons: • Pharmacologic eg narcotic or sedative overdose • Structural egmeningoencephalitis, localized tumors, vascular abnormalities of medulla, strokes affecting medullary control centres • Metabolic egmyxedema, hepatic failure, uremia

10. B: Defective respiratory neuromuscular system: • Spinal cord and peripheral nerves: • High cervical trauma • Poliomyelitis • Motor neuron disease • Guilain-Barré syndrome • Respiratory muscles: • Myasthenia gravis • Myopathy

11. C: Impaired ventilatory apparatus: • Chest wall: • Kyphoscoliosis • Ankylosingspondylitis • Obesity hypoventilation • Airways and lungs: • Laryngeal and tracheal stenosis • COPD

12. Clinical features Hypoxia : Dyspnoea Central cyanosis Agitation Restlessness Confusion Hypercapnia: Headache Peripheral Vasodilatation Tremor / flap Bounding pulse Drowsiness Coma

13. Acute on Chronic respiratory failure • COPD = most common cause • Chronic CO2 retention → renal HCO32+retention → normal pH (compensated respiratory acidosis) • Hypoxia is main stimulus for ventilation • New insult eg acute exacerbation → sudden ↑PaCO2 and acidemia→ drowsiness and coma. • Aim of management: • Airway protection • Controlled O2 therapy to improve oxygenation without removing hypoxic respiratory drive completely • Treat specific precipitating cause

14. Approach to patient with ↓PaO2 PaCO2↑ ? Yes No PAO2 – PaO2↑ ? Hypoventilation Yes No PAO2 – PaO2↑ ? Is low PO2 correctable with O2? ↓ FIO2 No Yes No Yes Hypoventilation alone Hypoventilation + another mechanism Shunt V/Q mismatch

15. Management of respiratory failure • Depends on the cause: • Ensure open airway • O2 via face mask or nasal cannulae – 35-55% O2 • Venturi mask – controlled delivery of 24 or 28% O2 • Mask with reservoir bag – delivers almost 100% O2 • Mechanical ventilation – invasive or non-invasive

16. CorPulmonale • Right ventricular hypertrophy or failure as a result of pulmonary hypertension caused by diseases affecting the lung or its vasculature • Acute and life threatening or chronic and slowly progressive

17. Possible mechanisms: • Pulmonary vasoconstriction (secondary to alveolar hypoxia or blood acidosis) • Anatomic reduction of pulmonary vascular bed (emphysema, pulmonary emboli) • Increased blood viscosity (polycythemia, sickle-cell disease) • Increased pulmonary blood flow

18. Clinical features • Symptoms: • Dyspnea on exertion • Fatigue • Lethargy • Chest pain • Syncope on exertion • Cough • Hempotysis • Anorexia • Right upper quadrant discomfort

19. Signs: • Pulmonary hypertension • S2 loud, palpable, narrowly split • Systolic ejection murmer • Diastolic PR murmer • RV hypertrophy • Prominent A wave of JVP • Right-sided 4th heart sound • Left parasternal heave • RV failure • Elevated JVP • Prominent V-wave • Right ventricular 3rd heart sound • TR murmer • Hepatomegaly • Other • Peripheral edema

20. Chest X-ray

21. ECG

22. Echocardiography

23. Management of corpulmonale • Oxygen therapy for hypoxemic patients • Relieves pulmonary vasoconstriction • Diuretics • Improve function of both right and left ventricles by reducing preload and right ventricular filling pressure • Caution: • Excessive volume depletion can reduce cardiac output • Metabolic alkalosis can suppress ventilation • Phlebotomy • If hct > 55% and patient symptomatic

24. Case studies • A mountain climber is 5800m above sea-level (barometric pressure = 380 mmHg). He has headache, looks disoriented and is hyperventilating. An ABG reveals a PaO2 of 40 mmHg and PaCO2 of 25 mmHg. Why is he hypoxic?

25. After passing the recent grade 12 exams, a young female experienced with narcotics and accidentally took and overdose of heroin. She is brought to casualty comatose. ABG reveals PaO2 of 50 mmHg and PaCO2 of 80 mmHg with pH 7.0 Why is she hypoxic?

26. A 24 year old university student presents at casualty with recent onset of severe fever, coughing and dyspnea. ABG reveals a PaO2 of 35 mmHg and PaCO2 of 25 mmHg. After giving him 40% via facemask, his PaO2 improves to 70 mmHg. Why is he hypoxic?