Impact of volume targeting on efficacy of bi-level non-invasive ventilation and sleep in obesity-hypoventilation

Summary

Background

Volume targeting by bi-level positive pressure ventilation (BPPV) has recently been made available by several manufacturers for home care ventilators. Although it may improve nocturnal ventilation, we hypothesized that increased pressure swings related to volume targeting may have a deleterious effect on sleep structure and patient comfort.

Methods

Patients in stable clinical condition (n = 12) treated by BPPV for obesity-hypoventilation (BMI: 44 ± 8 kg/m²) for a median of 30 months (range: 2–138), underwent nocturnal polysomnography with transcutaneous capnography on 2 consecutive nights with either BPPV and usual ventilator settings or BPPV with volume targeting, in randomized sequence. Subjective quality of sleep (St. Mary's Hospital Questionnaire) and comfort of ventilation (VAS scales) were also assessed.

Results

Mean IPAP, mean tidal volume, and total ventilation increased significantly with volume targeting. Control of nocturnal hypoventilation was slightly improved with volume targeting (nocturnal TcPCO₂: 42 ± 9 vs. 45 ± 5 mm Hg, p = 0.04). However, total sleep time and stage 2 sleep were greater without volume targeting, and wake after sleep onset and awakenings >20 s increased with volume targeting. Subjectively, patients described a lighter sleep, of lesser quality and more frequent awakenings with volume targeting; ventilation was perceived as less comfortable, with an increased perception of leaks and of “too much air”.

Conclusion

In stable patients treated by BPPV for obesity-hypoventilation, volume targeting improved control of nocturnal hypoventilation at the expense of a slight decrease in objective and subjective sleep quality, and comfort of ventilation.