When is bilevel positive airway pressure (BiPAP) indicated in adults (or selected adolescents) with hypercapnic respiratory failure such as acute COPD or asthma exacerbation, neuromuscular weakness (myasthenia gravis, Guillain‑Barré), obesity hypoventilation syndrome, or acute cardiogenic pulmonary edema who are able to protect their airway, cooperative, and hemodynamically stable?

When BiPAP is Recommended

BiPAP should be initiated in adults with acute hypercapnic respiratory failure (pH ≤7.35, PaCO₂ >45 mmHg) due to COPD exacerbation, neuromuscular disease, chest wall deformity, or obesity hypoventilation syndrome who are cooperative, hemodynamically stable, and able to protect their airway. 1

Primary Indications for BiPAP

COPD Exacerbation with Respiratory Acidosis

• Initiate BiPAP when pH <7.35 (H+ >45 nmol/L) persists despite maximal medical therapy on controlled oxygen, with PaCO₂ >45 mmHg and respiratory rate >20-24 breaths/min. 1
• There is no lower pH threshold below which BiPAP is inappropriate, though risk of failure increases as pH decreases—patients require very close monitoring with rapid access to intubation. 1
• BiPAP reduces mortality (RR 0.63,95% CI 0.46-0.87) and intubation rates (RR 0.41,95% CI 0.33-0.52) in COPD patients with acute hypercapnic respiratory failure. 1

Neuromuscular Disease and Chest Wall Deformity

• BiPAP is indicated for acute or acute-on-chronic hypercapnic respiratory failure due to neuromuscular disease (myasthenia gravis, Guillain-Barré) or chest wall deformity. 1
• These patients may present in respiratory failure without significant breathlessness, requiring a low threshold for arterial blood gas measurement. 1

Obesity Hypoventilation Syndrome

• Use BiPAP (bi-level pressure support) for decompensated obesity hypoventilation syndrome when respiratory acidosis is present (pH <7.35). 1

Cardiogenic Pulmonary Edema (Second-Line)

• Reserve BiPAP for cardiogenic pulmonary edema patients who remain hypoxic or develop hypercapnia despite CPAP and maximal medical treatment. 1
• CPAP is the preferred initial non-invasive ventilation mode for cardiogenic pulmonary edema; BiPAP should only be used when CPAP is unsuccessful. 1

Ventilator Weaning

• BiPAP should be used when conventional weaning strategies from invasive ventilation fail. 1

Critical Patient Selection Criteria

Required Patient Characteristics

• Cooperative and able to follow commands 1
• Hemodynamically stable 1
• Able to protect airway (intact gag reflex, not vomiting) 1
• Conscious enough to tolerate mask interface 1

Absolute Contraindications

• Recent facial or upper airway surgery 1
• Facial burns, trauma, or abnormalities preventing mask seal 1
• Fixed upper airway obstruction 1
• Active vomiting 1
• Recent upper gastrointestinal surgery 1
• Inability to protect airway 1

When NOT to Use BiPAP

Acute Asthma

• BiPAP should NOT be used routinely in acute asthma. 1
• The evidence does not support routine BiPAP use for asthma exacerbations, unlike COPD. 1

Bronchiectasis (Limited Role)

• A trial of BiPAP may be attempted in bronchiectasis with respiratory acidosis (pH <7.35), but excessive secretions typically limit effectiveness—do not use routinely. 1

Pneumonia (Cautious Use Only)

• BiPAP can be used as an alternative to intubation if pneumonia patients become hypercapnic, but only in ICU settings for intubation candidates. 1
• Many pneumonia patients with hypoxemia resistant to high-flow oxygen will require intubation; trials of BiPAP should only occur in HDU or ICU. 1

Practical Implementation Algorithm

Pre-Initiation Decision

• Document intubation decision BEFORE starting BiPAP—determine if this is a therapeutic trial with intubation backup or ceiling of treatment. 1
• Verify decision with senior medical staff immediately. 1

Initial Settings

• Start IPAP 8-12 cmH₂O and EPAP 4-5 cmH₂O 2, 3
• Maintain minimum pressure differential (IPAP-EPAP) of 4 cmH₂O 2, 3
• Titrate FiO₂ to maintain SpO₂ 85-90% in COPD patients or 90-96% in non-COPD patients 1, 2

Monitoring Requirements

• Reassess arterial blood gases at 1 hour after BiPAP initiation—most trials show improvement evident at 1 hour and certainly by 4-6 hours. 1
• Close monitoring with prompt evaluation is essential to prevent delayed intubation. 1
• Guidelines recommend judging patient condition within 1-2 hours after starting BiPAP. 1

Signs of Treatment Failure Requiring Intubation

• Deteriorating conscious level 1, 4
• Failure to improve arterial blood gases (pH, PaCO₂) within 1-4 hours 1
• Development of complications (pneumothorax, aspiration) 1, 4
• Patient-ventilator asynchrony despite adjustments 1
• Hemodynamic instability 4
• Persistent pH <7.25 despite optimal settings 4

Common Pitfalls and How to Avoid Them

Delayed Intubation

• The greatest risk of BiPAP is delaying necessary intubation—do not persist beyond 1-4 hours if no improvement occurs. 1
• Have a low threshold for intubation in patients who are immediately deteriorating. 1

Inadequate Secretion Management

• Excessive secretions limit BiPAP effectiveness—assess secretion burden and consider physiotherapy before initiating. 4
• This is particularly relevant in bronchiectasis and pneumonia. 1

Wrong Mode Selection

• BiPAP is preferred over CPAP for type 2 respiratory failure (hypercapnia); CPAP is indicated for hypoxemic respiratory failure. 1, 2
• In cardiogenic pulmonary edema, start with CPAP first—only escalate to BiPAP if CPAP fails or hypercapnia develops. 1

Inadequate Monitoring Location

• Patients who are intubation candidates if BiPAP fails should only receive BiPAP in ICU settings. 1
• Chest wall trauma patients on BiPAP require ICU monitoring due to pneumothorax risk. 1

Patient Intolerance

• Approximately 29% of COPD patients do not tolerate BiPAP—have backup plans ready. 5
• Poor mask fit and interface issues are common causes of treatment failure. 3