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Acute Respiratory Obstruction and Restriction

Acute Respiratory Obstruction and Restriction. ICU nurses course 2004 Tim Smith. Topics. Asthma (acute bronchospasm) Acute Exacerbation of COPD Pneumothorax Pleural Effusion. Acute Asthma. Asthma. Chronic inflammatory condition of the lung airways characterised by:

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Acute Respiratory Obstruction and Restriction

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  1. Acute Respiratory Obstruction and Restriction ICU nurses course 2004 Tim Smith

  2. Topics • Asthma (acute bronchospasm) • Acute Exacerbation of COPD • Pneumothorax • Pleural Effusion

  3. Acute Asthma

  4. Asthma Chronic inflammatory condition of the lung airways characterised by: • Reversible airflow limitation • Airway hyperresponsiveness • Bronchial inflammation • Increasing prevalence • 10-15% of pop. In 2nd decade

  5. Pathogenesis • Extrinsic vs. Intrinsic • Mast cells (histamine, LTC4, PGD2) • T cells (cytokines) • Eosinophils (ECP, MBP) • C-fibres (NKA, CGRP, SubP)

  6. Precipitating Factors • Allergens • Flour • Washing powder • Animals • Non-specific • Exercise • Cold air • Emotion • Occupational • Isocyanates • Colophony fumes

  7. Mechanisms • Bronchoconstriction • Airway inflammation • Microvascular leak • Oedema • Increased (viscid) mucus production AIRWAY OBSTRUCTION

  8. Physiological Effects • Increased work of breathing • Accessory muscle use • Increased oxygen demands • Air trapping • Prolonged active expiratory phase • Auto-PEEP • V/Q mismatch • Hypoxia • Increased respiratory drive

  9. Clinical Features 1 Related to severity: • Moderate asthma exacerbation • Breathlessness • Wheeze (expiratory) • PEF 50-75%

  10. Clinical Features 2 • Acute Severe Asthma One of: • PEF 33-50% • RR >= 25 /min • HR >= 110/min • Inability to complete sentences

  11. One of: PEF <33% SpO2 <92% PaO2 <8kPa Normal PaCO2 Silent chest Cyanosis Feeble respiratory effort Bradycardia Dysrhythmia Hypotension Exhaustion Confusion Coma Clinical Features 3 • Life threatening Asthma

  12. Clinical Features 4 • Near Fatal Asthma One of: • High PaCO2 • Mechanical ventilation

  13. Chest X Ray • Hyperinflation • Flattened diaphragm

  14. Chest X Ray 2

  15. CT Scan

  16. MRI with He3 Before 40 min after Albuterol

  17. Medical Therapy • Oxygen • β2-agonists • Nebulised if possible • Steroids • Ipratropium Bromide • Magnesium Sulphate • Life threatening or poor response • Aminophylline • Perhaps in some patients

  18. Indications for ITU • Deteriorating PEF • Worsening hypoxia • Hypercapnia • Worsening acidosis • Altered conciousness • Exhaustion • Respiratory arrest

  19. ITU treatment • Continue full medical treatment • NIV • Perhaps • IPPV • For worsening hypoxia/hypercapnia • Exhaustion • Reduced concious level • Optimise • Fluid status • Hypokalaemia (steroids, β2-agonists)

  20. Ventilation • Conventionally volume controlled • Slow rate • Long expiratory time • Low/no PEEP eg. MV 115 ml/kg, TV 6-8 ml/kg, RR 8-10, PEEP 0 • FiO2 to keep SpO2 >=94% • Remember: hypotension, pneumothorax, EMD

  21. Acute Exacerbation of COPD

  22. Acute Exacerbation of COPD • COPD affects 5% of adult population • Fifth most common cause of death world wide. • Chronic irreversible disease • Acute deterioration can be precipitated by diverse causes

  23. Pathologic Processes • Bronchiolitis (inflam. airway narrowing) • Loss of connective tissue tethering • Loss of alveoli and capillaries • Increased closing volume • Increased pulmonary vascular resistance • Resulting in: • V/Q mismatch • Increased resistance • Dynamic hyperinflation • Increased work of breathing

  24. Causes of Exacerbations • Infection (50%) • Heart Failure (25%) • Sputum Retention • PE • Pneumothorax • Sedation • Medication • Malnutrition

  25. Treatment Treat underlying cause and support: • Oxygen (titrate avoiding carbonarcosis) • Bronchodilators • Steroids (not if pneumonic cause) • Antibiotics for infectious cause • Clearance of secretions • Physio, mucolytics, suctioning, bronchoscopy • Hydration, Diuretics, Vasodilators • DVT prophylaxis • Nutrition • no benefit from respiratory stimulants

  26. Non-invasive Ventilation 1 • Ventilatory support via nasal/facemask • Aims: • Unload respiratory muscles • Augment ventilation • Improve oxygenation • Reduce CO2

  27. Non-invasive Ventilation 2 Indicated for: Worsening COPD with: • Acute dyspnoea • RR >28/min • PaCO2 > 6kPa and pH < 7.35 in spite of maximal medical therapy and not related to XS O2

  28. Invasive Ventilation 1 • Indications: • Exhaustion despite NIV • Deteriorating concious level • Hypoxia • Failure of secretion clearance • Respiratory arrest • Need for mechanical ventilation dramatically decreases survival. • Weaning often difficult.

  29. Invasive Ventilation 2 • Strategy: • Low RR • Low TV • Prolonged expiration • Pitfalls: • Dynamic hyperinflation • Barotrauma • Prolonged difficult wean

  30. Invasive Ventilation 3 • Outcome: • ITU mortality 10-30% • 1 year survival 50% • Depends more on previous state, nutrition, age than on measured variables.

  31. Pneumothorax Pathological collection of extraalveolar air in the pleural space.

  32. Causes • Spontaneous: • Primary – no underlying lung disease • Secondary – COPD/CF/AIDS/Ca/chemo • Traumatic: • blunt or penetrating chest trauma • iatrogenic – central lines/surgery • Barotrauma: • positive pressure ventilation (4-15%) • ARDS & IPPV (up to 60%) • (COPD/asthma)

  33. Clinical Features 1 • Decreased or absent breath sounds • Hyperresonant percussion • Chest pain • Dyspnoea (worse if secondary) • Tachycardia • Pleural line & lucent space on CXR • Hypoxaemia (if large)

  34. Pneumothorax

  35. Stab wound

  36. Clinical Features 2 • Pneumothorax may be difficult to detect in ventilated patient with poorly compliant lungs: • Stiff lungs do not collapse readily • Gas exchange often already disordered • Subtle early signs: • Decreased urine output • Increased CVP • Tachycardia • Decreased CI • High index of suspicion • CT scanning may be useful

  37. Tension Pneumothorax • One way valve effect • Intrapleural gas accumulates • Displacement of mediastinum • Compression of contralateral lung • Hypoxaemia due to shunt • Decreased VR and CO • Hypotension and EMD arrest

  38. Tension Pneumothorax

  39. Treatment 1 • Spontaneously breathing patient • Small pneumothorax (<20%) if asymptomatic can be treated conservatively. • Larger pneumothorax must be aspirated or drained. • Recurrence requires pleurodesis

  40. Treatment 2 • Ventilated patient: • Low threshold for draining pneumothoraces as risk of tension • Place chest drain in patient with pneumothorax requiring ventilation

  41. Treatment 3 • Tension pneumothorax: • Potentially rapidly fatal • Rapid decompression based on clinical diagnosis improves survival • Don’t wait for the X-ray

  42. Pleural Effusion • Pathological collection of fluid within the pleural space. • Starling Forces normally keep pleural space dry. • Effusion results from: • Increased pulmonary capillary pressure • Increased capillary permeability • Hypoalbuminaemia • Lymphatic obstruction

  43. Clinical Features • Pleuritic pain • Cough • Dyspnoea. • Decreased air entry • “stony” dullness • Restrictive defect

  44. Radiology • CXR (upright PA) • >300ml loss of costophrenic angle • Larger effusions cause opacification • Lateral decubitus films • more sensitive (5ml) • Impractical on ITU • USS • Extremely sensitive (2ml) • Can be used to guide drainage

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