What are the key considerations and treatment approaches for critical respiratory conditions, such as pulmonary embolism, acute respiratory distress syndrome (ARDS), and status asthmaticus, in older adults with underlying medical conditions like chronic obstructive pulmonary disease (COPD) or heart disease?

Critical Respiratory Conditions in Older Adults: Key Board Exam Considerations

Acute Respiratory Distress Syndrome (ARDS)

Immediate Ventilatory Management

All patients with ARDS require mechanical ventilation with low tidal volumes (4-8 ml/kg predicted body weight) and plateau pressures ≤30 cm H₂O, regardless of age or comorbidities 1. This lung-protective strategy reduces mortality and is the cornerstone of ARDS management 1.

• **Severe ARDS (PaO₂/FiO₂ <100):** Implement prone positioning for >12 hours daily, which significantly improves survival in severe cases 1
• Moderate-to-severe ARDS (PaO₂/FiO₂ <200): Use higher PEEP (≥12 cm H₂O) and consider recruitment maneuvers, though evidence is less robust 1
• Avoid high-frequency oscillatory ventilation in moderate or severe ARDS, as it does not improve outcomes and may cause harm 1

ECMO Considerations

For refractory severe ARDS with PaO₂/FiO₂ <70 for ≥3 hours or <100 for ≥6 hours despite optimized ventilation (including prone positioning and neuromuscular blockade), consider venovenous ECMO within 7 days of onset 1. If concurrent severe cardiogenic shock exists (requiring norepinephrine >0.5 µg/kg/min or significant inotropic support), venoarterial ECMO may be indicated 1.

Hemodynamic Monitoring in ARDS

Monitor for right ventricular dysfunction using echocardiography, particularly in patients with underlying heart disease, as RV failure is a critical determinant of mortality 1. Prone positioning may improve RV function by reducing ventilator-induced lung injury and improving ventilation uniformity 1.

Status Asthmaticus

Initial Assessment and Bronchodilator Therapy

Begin with nebulized β-agonist (salbutamol 2.5-5 mg or terbutaline 5-10 mg) plus ipratropium bromide 0.5 mg, repeated every 4-6 hours or more frequently in severe cases 2, 3. The combination provides superior bronchodilation compared to either agent alone 2.

• Administer oxygen to maintain adequate saturation while avoiding hyperoxemia 1
• Add systemic corticosteroids (prednisolone 30 mg daily or hydrocortisone 100 mg IV) immediately in severe presentations 1, 2
• If inadequate response after initial nebulization, increase frequency to every 1-4 hours and consider hospital admission 3

Critical Pitfalls in Older Adults

β-agonists may precipitate angina in elderly patients with coronary disease—the first treatment must be supervised 2. When using ipratropium in patients with glaucoma, use a mouthpiece rather than face mask to minimize ocular exposure 2, 3.

Escalation Strategy

If no improvement after optimized nebulized therapy, consider intravenous aminophylline (0.5 mg/kg/hour) with daily theophylline level monitoring, though evidence for effectiveness is limited 1.

COPD Exacerbations

Bronchodilator Approach

Start with nebulized salbutamol 2.5-5 mg or terbutaline 5-10 mg; if response is inadequate, add ipratropium bromide 0.25-0.5 mg 1, 2. For severe exacerbations, use both agents together from the outset 1, 2.

• Continue nebulized therapy for 24-48 hours until clinical improvement, then transition to metered-dose inhalers 1
• Add systemic corticosteroids (prednisolone 30 mg daily) for 7-14 days in moderate-to-severe exacerbations 1
• Initiate antibiotics if sputum becomes purulent (amoxicillin, tetracycline derivatives, or amoxicillin/clavulanic acid for 7-14 days) 2

Oxygen Management in COPD

If PaCO₂ is elevated or respiratory acidosis is present, drive nebulizers with compressed air, not oxygen, to prevent worsening hypercapnia 1, 2. Between nebulizations, use 24% Venturi mask for controlled oxygen delivery 2, 3.

Ventilatory Support Thresholds

Consider non-invasive positive pressure ventilation (NIPPV) or invasive ventilation when pH <7.26 with rising PaCO₂ despite optimal medical therapy 1. NIPPV reduces the need for intubation and shortens hospital stay when initiated early 1. Doxapram infusion may provide temporary support (24-36 hours) while treating the underlying cause 1.

Pulmonary Embolism in COPD Patients

Diagnostic Challenges

In severe COPD patients, acute PE often presents with acute reduction in previously elevated PaCO₂ (increased alveolar ventilation) plus worsening hypoxemia, rather than typical dyspnea alone 4. Standard clinical and radioisotopic studies have limited diagnostic value in this population 4.

Risk Stratification

Use the Pulmonary Embolism Severity Index (PESI) or simplified PESI to identify low-risk patients (PESI Class I-II or sPESI=0) who may be candidates for outpatient management 1. In older adults, age >70 years, systolic BP <90 mmHg, respiratory rate >20/min, cancer, chronic heart failure, and COPD are independent prognostic factors 1.

Echocardiographic Assessment

Perform echocardiography to assess for RV dysfunction, which occurs in ≥25% of PE patients and predicts adverse outcomes 1. Presence of patent foramen ovale or right heart thrombi further increases mortality risk 1.

Anticoagulation in Acute Respiratory Failure

Administer prophylactic subcutaneous heparin for all patients with acute-on-chronic respiratory failure to prevent thromboembolic complications 1.

Fluid Management Across All Conditions

Use restrictive fluid strategies in ARDS patients without shock or multiple organ dysfunction 5. Diuretics are indicated only when peripheral edema and elevated jugular venous pressure are present 1.

Common Board Exam Pitfalls

• Do not use peak flow meters for asthma diagnosis—spirometry is required for objective assessment 1
• Do not routinely use high-frequency oscillatory ventilation in ARDS—it increases mortality 1
• Do not withhold prone positioning in severe ARDS due to perceived difficulty—it is strongly recommended and improves survival 1
• Do not assume wheezing in older adults is always COPD or asthma—consider PE, congestive heart failure, and mechanical airway obstruction 1, 4
• Do not use continuous thermodilution or pulse contour cardiac output monitoring in patients on ECMO—these methods are unreliable 1