Usefulness of Transcutaneous Capnography to Assess Residual Hypoventilation in Obesity-Hypoventilation Syndrom Treated by Non Invasive Ventilation at Home : a Prospective Study

Overview

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

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