Sleep related respiratory events during non-invasive ventilation of patients with chronic hypoventilation

Background: Non-invasive ventilation (NIV) is increasingly used in the treatment of patients with chronic hypercapnic respiratory failure (CRF). Residual sleep related respiratory events under NIV such as obstructive or central apnea/hypopnea (AH), or patient-ventilator asynchrony (PVA), may compromise treatment efficacy and/ or comfort. Aims of study: 1/to quantify the frequency and describe the types of both AH and PVA in a large group of stable patients with CRF during night-time NIV; 2/to analyze the influence of these events on overnight pulse oximetry and transcutaneous CO2 and 3/to assess interrater agreement in identifying and quantifying AH and PVA. Methods: We quantified AH and PVA by performing sleep polygraphy in 67 patients during elective follow-up visits. Traces were scored by two trained physicians. Results: Residual AH were frequent: 34% of the patients had an AH Index > 5/hour, with obstructive hypopnea being the most frequent event. In addition, 21% of the patients had PVA > 10% of total recording time. No correlation was found between respiratory events and overnight hypercapnia. The intraclass correlation coefficients for scoring AHI and time with PVA were 0.97 (0.94-0.98) and 0.85 (0.75-0.91) respectively. Conclusions: Residual respiratory events are common in patients treated with long term NIV for chronic hypercapnic respiratory failure and can be scored with a very high interobserver agreement. However, these events were not associated with persistent nocturnal hypercapnia; thus, their clinical relevance has yet to be clarified. ClinicalTrials.gov registration No: NCT01845233.