CURRENT Essentials of Critical Care.pdf

Chapter 8 Respiratory Failure 105■■■Respiratory Failure from ChronicObstructive Lung DiseaseEssentials of Diagnosis• Chronic bronchitis or emphysema• Increasing dyspnea, often with cough, decreased exercise capacity,increased sputum production, respiratory muscle fatigue• Mild to moderate hypoxemia; may have PaCO 2 50 mm Hgwith acute respiratory acidosis (pH 7.35), even in those withoutchronic CO 2 retention• Mechanisms include increased airway resistance (bronchospasm,increased secretions, airway edema), infection andhost response to infection (change in bacterial type, purulentsputum), altered lung mechanics (hyperinflation)Differential Diagnosis• Asthma, pneumonia, pulmonary edema• Neuromuscular weakness or central hypoventilation syndromeTreatment• Identify most severe: very low peak expiratory flow, pH 7.25with PaCO 2 60, right heart failure, pneumothorax, pneumonia,poor response to bronchodilators, malnutrition, multiorgan failure• Oxygen: 2–4 L/min nasal cannula or FIO 2 0.28–0.40 by Venturimask• Aerosolized albuterol and ipratropium bromide; theophyllinenot recommended• Intravenous or oral corticosteroids; taper 7–10 days• Antibiotics against S pneumoniae, H influenzae, M catarrhalis(2nd generation cephalosporins, extended-spectrum macrolides,fluoroquinolones)• In selected patients, noninvasive positive pressure ventilation upto 12–24 hours• Mechanical ventilation if severe, nonresponse to therapy, alteredmental status, muscle fatigue■ PearlPatients with most severe hypoxemia and lowest pH (acute respiratoryacidosis) are at highest risk for worsening hypercapnia with administrationof oxygen.ReferenceBach PB et al: Management of acute exacerbations of chronic obstructive pulmonarydisease: a summary and appraisal of published evidence. Ann InternMed 2001;134:600. [PMID: 11281745]