Usefulness of Transcutaneous Capnography to Assess Residual Hypoventilation in Obesity-Hypoventilation Syndrom Treated by Non Invasive Ventilation at Home : a Prospective Study
Usefulness of Transcutaneous Capnography to Assess Residual Hypoventilation in Obesity-Hypoventilation Syndrom Treated by Non Invasive Ventilation at Home : a Prospective Study
Transcutaneous capnography (PtcCo2) recently showed good agreement with blood gases to assess
 hypercapnia. There is no study that has evaluated the benefit to realise systematically a
 nocturnal PtcCo2 in the follow-up of home-ventilated patient with obesity hypoventilation
 syndrome (OHS). The investigators will evaluate the intake bring by nocturnal transcutaneous
 capnography, compared to nocturnal oximetry and blood gases, to diagnose nocturnal alveolar
 hypoventilation in a population of patient presenting an OHS, treated by non invasive
 ventilation (NIV) at home .
Patients will be evaluated once a year in consultation with a blood gases, and then a
 nocturnal recording at home including a transcutaneous capnography and an oximetry.

 Some data will be registered too : cardiovascular and neurological comorbidities, diabetes
 mellitus, treatment, parameters of the non-invasive ventilation, duration of compliance and
 apnea-hypopnea index (if available).

 The investigators will perform a sequential analysis of nocturnal hypoventilation with first
 blood gases, then nocturnal oxymetry and to finish nocturnal PtcCo2. It will allow us to
 determine if PtcCo2 catch up some nocturnal hypoventilation, undetected by the first two
 exams.

 The investigators plan that the study will last 18 months. The analysis will be descriptive.
 Quantitative variables will be described with mean, standard deviation, minimum, maximum and
 median. Quantitative variables are presented with number and percentage.

 Comparison of blood gas / oximetry association with blood gas / oximetry / transcutaneous
 capnography using a McNemar test
Inclusion Criteria:

 -  Obesity Hypoventilation Syndrom defined by a diurnal PaCo2> 45 mmHg, in stable
 conditions, in a patient presenting an obesity (BMI > 30 kg/m²)

 -  treated by non invasive ventilation since at least 3 weeks, and seen in follow-up
 consultation

 Exclusion Criteria:

 -  minors

 -  refusal to participate

 -  under guardianship or trusteeship

 -  pregnant woman

 -  other etiology of hypoventilation : copd, kyphoscoliosis, neuromuscular disorders,
 diaphragmatic pathology