Elsevier

Respiratory Medicine

Volume 101, Issue 6, June 2007, Pages 1229-1235
Respiratory Medicine

Non-invasive positive pressure ventilation improves lung volumes in the obesity hypoventilation syndrome

https://doi.org/10.1016/j.rmed.2006.10.027Get rights and content
Under an Elsevier user license
open archive

Summary

Background

Our objective was to study the long-term effects of non-invasive positive pressure ventilation (NPPV) on lung function and gas exchange in patients with the obesity hypoventilation syndrome (OHS).

Design

Prospective observational study in OHS patients performing NPPV over a period of 24 months.

Results

We studied 35 clinically stable OHS patients with a mean body mass index (BMI) 45.9±8.8 kg/m2 and daytime PaCO2 at room air of 6.92±0.48 kPa at baseline. Nocturnal NPPV was initiated with pressure-cycled devices on IPAP 24±3 cm H2O, EPAP 6±2 cm H2O and respiratory frequency of 18.8±3.7/min. After 12 and 24 months of NPPV hypercapnia was persistently normalized and hypoxemia was markedly improved while no changes in calculated alveolar–arterial oxygen difference occurred. Augmented ventilation was followed by a significant reduction in hemoglobin and hematocrit (P<0.001 each). Daily duration of ventilator use significantly correlated with the decrease in PaCO2 after 12 months (r=0.37; P<0.05) and 24 months (r=0.47; P<0.05). Vital capacity (VC) and expiratory reserve volume (ERV) significantly increased after 12 and 24 months NPPV compared to the baseline values, though BMI was only slightly reduced. The 2-year survival rate was 91% with three patients (9%) discontinuing NPPV during the study period.

Conclusion

Long-term domiciliary NPPV normalizes hypercapnia and markedly improves hypoxemia as well as polycythemia in OHS patients. In addition, NPPV leads to a significant reduction in restrictive ventilatory disturbance, predominantly by increasing ERV. Application of high inspiratory pressures and good adherence to therapy are presumed to be the basis for the beneficial effects of NPPV in OHS.

Keywords

Chronic ventilatory failure
Non-invasive positive pressure ventilation
Obesity hypoventilation syndrome
Pulmonary function test
Restrictive ventilatory disorder

Abbreviations

A–aDO2
alveolar–arterial oxygen difference
BE
base excess
BMI
body mass index
EPAP
expiratory positive airway pressure
ERV
expiratory reserve volume
FEV1
forced expiratory volume in 1 s
FRC
functional residual capacity
Hb
hemoglobin
Hc
hematocrit
IC
inspiratory capacity
IPAP
inspiratory positive airway pressure
NPPV
non-invasive positive pressure ventilation
P0.1
mouth occlusion pressure at 100 ms
PaCO2
arterial carbon dioxide tension
PaO2
arterial oxygen tension
PImax
maximal inspiratory pressure
RV/TLC
ratio residual volume/total lung capacity
SaO2
arterial oxygen saturation
SRtot
total specific resistance
TLC
total lung capacity
VC
vital capacity.

Cited by (0)