What pressure support settings are recommended for a Chronic Obstructive Pulmonary Disease (COPD) patient with type 2 respiratory failure on Continuous Positive Airway Pressure (CPAP)?

Pressure Support Settings for COPD Patients with Type 2 Respiratory Failure

For COPD patients with type 2 respiratory failure, you should use bilevel positive airway pressure (BiPAP) rather than CPAP alone, starting with IPAP 10-12 cmH₂O and EPAP 4-5 cmH₂O, as CPAP is primarily indicated for hypoxemic respiratory failure and does not provide the ventilatory support needed to reduce PaCO₂ in hypercapnic patients. 1, 2

Why BiPAP Over CPAP for Type 2 Respiratory Failure

CPAP alone is insufficient for type 2 respiratory failure because it does not provide pressure support to augment tidal volume and reduce work of breathing. 1 While CPAP can offset intrinsic PEEP and reduce inspiratory muscle work in COPD patients, it conventionally is not considered respiratory support and its main indication is to correct hypoxemia, not hypercapnia. 1

BiPAP combines inspiratory pressure support (IPAP) with expiratory pressure (EPAP), where the difference between these two pressures provides the ventilatory assistance needed to improve alveolar ventilation and reduce PaCO₂. 1 The IPAP generates tidal volume, while EPAP recruits underventilated lung, offsets intrinsic PEEP, and aids triggering. 1

Initial BiPAP Settings

Start with the following settings: 3, 2, 4

• IPAP: 10-12 cmH₂O (can start at 8-10 cmH₂O if patient is very frail or intolerant) 3, 2
• EPAP: 4-5 cmH₂O to counteract intrinsic PEEP and facilitate triggering 1, 2, 4
• Backup rate: 12-15 breaths/min in spontaneous-timed (S/T) mode to ensure minimum ventilation if respiratory drive is poor 1, 2
• Inspiratory time: 1.2-1.6 seconds (corresponding to 30-40% of respiratory cycle at rate of 15 breaths/min) 1
• Supplemental oxygen: Titrate to SpO₂ 88-92% (not higher, to avoid worsening hypercapnia) 2

Titration Strategy

Increase IPAP by 2 cmH₂O every 5-15 minutes if: 3, 2

• pH remains <7.35 or is worsening
• PaCO₂ is not improving
• Respiratory rate remains >25-30 breaths/min
• Patient continues to show signs of respiratory distress

Target IPAP is typically 14-20 cmH₂O for most COPD patients with acute hypercapnic respiratory failure. 4 The median effective IPAP in successful cases is approximately 14 cmH₂O. 4

Adjust EPAP cautiously: 1, 2

• EPAP of 4-6 cmH₂O is usually sufficient to offset intrinsic PEEP in COPD patients 4
• Do not set EPAP higher than the patient's intrinsic PEEP, as this can worsen hyperinflation and increase work of breathing 2, 5
• Excessive EPAP can paradoxically increase PaCO₂ and respiratory effort 5

Monitoring and Goals

Check arterial blood gases at 1 hour and 4 hours after initiating BiPAP: 2

Target parameters: 2

• pH >7.25-7.30 (ideally >7.35)
• Improving or stable PaCO₂
• SpO₂ 88-92% (avoid hyperoxia which worsens hypercapnia)
• Respiratory rate <25 breaths/min
• Improved work of breathing and patient comfort

Within 1-2 hours, the patient should show clinical improvement. 2, 4 If there is no improvement or worsening (pH <7.20, worsening acidosis, decreased consciousness, inability to clear secretions), prepare for intubation. 2

Critical Pitfalls to Avoid

Do not use CPAP alone for type 2 respiratory failure - it will not provide adequate ventilatory support to reduce PaCO₂. 1, 2 While CPAP at 3-6 cmH₂O can reduce intrinsic PEEP and work of breathing in COPD patients, it does not augment tidal volume sufficiently to improve hypercapnia. 6, 7

Avoid excessive EPAP - setting EPAP greater than intrinsic PEEP can worsen air trapping and increase work of breathing in COPD patients. 2, 5 Research shows that BiPAP with inappropriately high EPAP can actually increase work of breathing compared to pressure support alone. 5

Do not target SpO₂ >94% - excessive oxygen administration in type 2 respiratory failure can suppress respiratory drive and worsen hypercapnia. 2 Target 88-92% is appropriate. 2

Do not delay intubation if BiPAP is failing - if there is no improvement within 1-2 hours or if the patient deteriorates (worsening acidosis, altered mental status, hemodynamic instability), proceed to intubation. 2, 4 Delayed intubation increases mortality. 2

Mode Selection

Use spontaneous-timed (S/T) mode rather than spontaneous mode alone to provide backup breaths if the patient's respiratory drive is inadequate. 1 In S/T mode, the ventilator delivers assisted breaths triggered by the patient, but will deliver mandatory breaths at the backup rate if the patient fails to trigger. 1

Pressure support (PS) mode is superior to other BiPAP modes for reducing respiratory muscle effort in spontaneously breathing COPD patients. 5 Research demonstrates that pressure support reduces work of breathing more effectively than other biphasic modes in COPD. 5