A patient with long-standing COPD is admitted to the respiratory ward with an acute exacerbation of the disease. They have received salbutamol, ipratropium, prednisolone


An ABG shows:


||||
|--------------|:-------:|------------------|
|pH|7.31|7.35 - 7.45|
|PaO₂|7.2 kPa|11 - 15|
|PaCO₂|6.6 kPa|4.6 - 6.4|
|Bicarbonate|32.5 mmol/L|22 - 30|
|Lactate|1.2 mmol/L|0.6 - 1.4|
|Sodium|136 mmol/L|135 - 145|
|Potassium|4.3 mmol/L|3.5 - 5.3|
|Non-fasting Glucose|7 mmol/L|< 6.1|




Which form of respiratory support would be most appropriate to select?

Options:
explanation: CPAP provides continuous pressure during inhalation and exhalation (like trying to breathe against the wind). This is better for improving oxygenation, e.g. in acute heart failure and respiratory distress, rather than ventilation. This patient has a type 2 respiratory failure with associated acidosis, so BiPAP (which will improve ventilation and the removal of CO2) is a more appropriate choice here.
name: Continuous positive airway pressure (CPAP)
label: b
answer: no
explanation: This is a mode of invasive mechanical ventilation (delivered via an endotracheal tube), which is not yet indicated. The British Thoracic Society guidelines recommend BiPAP (non-invasive ventilation) is attempted in COPD patients whose condition does not improve after 1 hour of maximal medical management and who have a pH of 7.25-7.35. Invasive ventilation would be indicated with a pH of 7.15 or below.
name: Pressure support ventilation (PSV)
label: d
answer: no
explanation: This is a mode of invasive mechanical ventilation (delivered via an endotracheal tube), which is not yet indicated. The British Thoracic Society guidelines recommend BiPAP (non-invasive ventilation) is attempted in COPD patients whose condition does not improve after 1 hour of maximal medical management and who have a pH of 7.25-7.35. Invasive ventilation would be indicated with a pH of 7.15 or below.
name: Volume-controlled ventilation (VCV)
label: e
answer: no
explanation: BiPAP (non-invasive ventilation) is an appropriate choice for this patient; it will improve oxygenation, as well as ventilation, reducing the patient's pCO2 which is resulting in a respiratory acidosis. NIV is indicated in COPD with acidosis (pH 7.25 - 7.35), hypercapnia (pCO2 >6 kPa), or increased work of breathing (respiratory rate >23) when 1 hour of optimal medical management has not improved the situation. If the pH is 7.15-7.25, NIV can still be tried, but the patient is at very high risk of needing to be intubated and needs to be closely monitored. Intubation is advised when the pH is <7.15.
name: Bi-level positive airway pressure (BiPAP)
label: a
answer: yes
explanation: This is a mode of invasive mechanical ventilation (delivered via an endotracheal tube), which is not yet indicated. The British Thoracic Society guidelines recommend BiPAP (non-invasive ventilation) is attempted in COPD patients whose condition does not improve after 1 hour of maximal medical management and who have a pH of 7.25-7.35. Invasive ventilation would be indicated with a pH of 7.15 or below.
name: Airway pressure release ventilation (APRV)
label: c
answer: no

Correct answer: a


Learning point: Bi-level positive airway pressure (BiPAP) is indicated in COPD exacerbations with respiratory acidosis and hypercapnia when medical management fails.