Volume Assured Pressure Support Ventilation


c) 54 y/o F with BMI 55, pCO2 55, AHI 78, REM-related hypoventilation that is not controlled on CPAP or BiPAP therapy

Volume assured pressure support (VAPS) targets minute ventilation and is used for hypoventilatory syndromes.
The patient described likely has obesity hypoventilation syndrome and is included in one of the groups that may benefit from this form of therapy. Other groups include patients who have neuromuscular disorders, patients who have extrinsic ventilatory restrictive disorders (e.g., kyphoscoliosis), and patients who have chronic lung disease (severe COPD), who may hypoventilate more during sleep.
A bi-level positive airway pressure (BPAP) device may also be indicated, but would not necessarily be as responsive to the patient’s needs as it gives a fixed amount of pressure support for each breath (and in this case was found to be ineffective). Currently, however, there are few head-to-head trials comparing outcomes among various devices.

The option of complex sleep apnea (positive airway pressure treatment emergent central events) is wrong because this patient would be better treated with an adaptive servoventilator that specifically targets airflow and increases pressure support to treat central apneas and hypopneas.

Similarly, adaptive support ventilation (ASV) would be a better treatment for the patient with central sleep apnea due to oxycodone.

The patient who has severe sleep apnea would probably be better served with a switch to a bi-level machine to allow higher pressure levels to treat obstructive events.


Volume targeted vs pressure support NIV in patient with super obesity and chronic respiratory failure: a randomized controlled trial. Thorax 2012;67(8):727-734
Automatic titration modes of non-invasive ventilation, including average volume assured pressure support (AVAPS), are hybrid technologies that target a set volume by automated adjustment of pressure support (PS). These automated modes could offer potential advantages over fixed level PS, in particular, in patients who are super obese.
Consecutive patients with obesity hypoventilation syndrome were enrolled in a two-centre prospective single-blind randomised controlled trial of AVAPS versus fixed-level PS using a strict protocolised setup.
The primary outcome was change in daytime arterial PCO(2) (PaCO(2)) at 3 months. Body composition, physical activity (7-day actigraphy) and health-related quality of life (severe respiratory insufficiency questionnaire, SRI) were secondary outcome measures.
50 patients (body mass index 50±7 kg/m(2); 55±11 years; 53% men) were enrolled with a mean PaCO(2) of 6.9±0.8 kPa and SRI of 53±17. 46 patients (23 AVAPS and 23 PS) completed the trial. At 3 months, improvements in PaCO(2) were observed in both groups (AVAPS 0.6 kPa, 95% CI 0.2 to 1.1, p<0.01 vs PS 0.6 kPa, 95% CI 0.1 to 1.1, p=0.02) but no between-group difference (-0.1 kPa, 95% CI -0.7 to 0.6, p=0.87). SRI also improved in both groups (AVAPS 11, 95% CI 6 to 17, p<0.001 vs PS 7, 95% CI 1 to 12, p=0.02; between groups 5, 95% CI -3 to 12, p=0.21). Secondary analysis of both groups combined showed improvements in daytime physical activity that correlated with reduction in fat mass (r=0.48; p=0.01).
The study demonstrated no differences between automated AVAPS mode and fixed-level PS mode using a strict protocolised setup in patients who were super obese. The data suggest that the management of sleep-disordered breathing may enhance daytime activity and promote weight loss in super-obese patients.