CPAP, bilevel PAP and non-invasive ventilation describe overlapping parts of respiratory care. They are not a simple ladder in which a more expensive mode is always a stronger or better treatment. The appropriate choice depends on the breathing problem and the support required.
Is the main problem airway obstruction?
CPAP maintains a pressure that helps keep the upper airway open. APAP adjusts pressure within a prescribed range. Both can be used for appropriate adults with obstructive sleep apnea.
Bilevel may be considered for selected patients, including some who have difficulty with the required CPAP treatment. Before changing modes, clinicians review mask fit, leak, comfort and whether the initial therapy was properly assessed.
Is ventilation inadequate?
Ventilation concerns how effectively air moves in and out of the lungs, including removal of carbon dioxide. Some people with respiratory-muscle weakness, chest-wall disease or chronic hypercapnic COPD need non-invasive ventilatory support.
The diagnosis alone does not select a particular algorithm. For example, ATS guidance recommends CPAP first for stable ambulatory obesity hypoventilation syndrome with coexisting severe OSA. Other presentations or an inadequate response may require NIV. It is inaccurate to send everyone with raised carbon dioxide directly to a volume-assured mode.
Are central events present?
Central sleep apnea needs assessment of its cause and the person's wider health. CPAP, selected backup-rate modes, adaptive servo-ventilation and other treatments have different roles; there is no universal CPAP-to-ST-to-ASV sequence.
Heart failure requires particular care. Current AASM guidance places ASV use in reduced-ejection-fraction heart failure in experienced centres with close monitoring. Applicable device contraindications and safety notices must also be respected. A general article cannot choose the safe mode for an individual.
How dependable must support be?
The team considers how long support is required, what happens if it stops, secretion management, the interface, alarms, backup power and caregiver capability. A home ventilator can deliver non-invasive support; the distinction is not determined solely by whether a tracheostomy is present or by a fixed number of hours per day.
Before obtaining equipment, ask the provider to confirm the exact prescribed mode and required capabilities in writing. A familiar pressure range or the label “bilevel” is insufficient. Training, follow-up and an interruption plan are part of matching the device to treatment.
Related reading: Volume-assured pressure support: targets and limitations