Two Functions
Bilevel devices serve two primary purposes:
- Provide noninvasive positive pressure ventilation (NPPV, sometimes NIPPV) therapy for hospital or in-home use
- Provide positive airway pressure therapy for sleep-disordered breathing patients who are noncompliant with CPAP therapy
Although both are non-invasive, Bilevel and CPAP therapy differ in two significant ways:
- Bilevel devices deliver two levels of air pressure that are set to coincide with the patient's inspiratory and expiratory efforts
- Bilevel therapy can be used to treat conditions other than sleep apnoea (OSA) and is the first line of treatment for a wide-range of respiratory disorders
What conditions are frequently treated with bilevel devices?
A broad range of conditions, including some that require 24-hour ventilatory support:
- Respiratory muscle dysfunction
- Previous poliomyelitis
- Muscular dystrophies
- Myopathies
- Neurological disorders
- Neuropathies
- Bilateral diaphragmatic paralysis
- Spinal cord injury
- Brainstem lesions
- Primary alveolar hypoventilation
- Chest wall deformity
- Upper airway disorders
- Severe OSA
- Obesity hypoventilation
- Lung disease
- COPD
- Cystic fibrosis
- Bronchiectasis
- Acute respiratory failure
- Hypercapnic respiratory failure
- Hypoxemic respiratory failure
- Obstructive sleep apnoea (OSA) without hypoventilation
- Poor compliance with CPAP
- Inability to exhale against CPAP
Is bilevel therapy typically prescribed for OSA patients?
No.
Bilevel therapy is not typically prescribed for OSA patients; however, OSA patients who require high treatment pressures or have another respiratory condition may be candidates for bilevel therapy.
Do most bilevel devices offer ventilatory assistance or support?
Most bilevel devices assist a patient's breathing, whereas critical care and some homecare ventilatory devices support a patient's breathing.
Why might bilevel devices be preferred for treatment (if ventilatory support is not required)?
Bilevel devices are often preferred by patients and caregivers (if ventilatory support is not required) as they tend to be:
- Smaller than ventilators
- Lighter than ventilators
- Quieter than ventilators
Bilevel Terminology
IPAP
IPAP (inspiratory positive airway pressure) - The pressure delivered to assist the patient when inhaling.
EPAP
EPAP (expiratory positive airway pressure) - The pressure delivered when the patient is exhaling. Naturally this pressure is less than IPAP because the patient breathes against it. For many conditions EPAP is necessary for airway patency.
Maximum IPAP time
Maximum IPAP time (maximum time a device will deliver IPAP) - Most bilevel devices have a three-second, non-adjustable maximum IPAP time. ResMed bilevel devices are the only ones with the IPAP MaxTM feature that allows clinicians to set the optimal maximum IPAP time for each patient during spontaneous breathing mode.
Recent studies show that almost all patients on bilevel therapy experience mouth leaks, which interfere with a device's triggering sensitivity from IPAP to EPAP. Poor triggering sensitivity results in poor synchrony of the patient's spontaneous breathing pattern and the bilevel's assistance. Asynchrony causes the patient to exhale against a higher pressure, increasing work of breathing and reducing the comfort and quality of therapy.
IPAP Max
IPAP Max counteracts the effect of mouth leak and improves synchrony so that therapy remains comfortable even in the presence of mouth leaks.