Diagnostic accuracy of simple tools in monitoring patients with chronic hypoventilation treated with non-invasive ventilation; a prospective cross-sectional study

Objectives To evaluate the sensitivity and specificity of a screening test panel for nocturnal hypoventilation (NH) and other sleep related respiratory events during monitoring of patients with chronic hypercapnic respiratory failure (CRF) treated with NIV. Methods We performed a prospective study at Oslo University Hospital. Eligible for inclusion were consecutive adults with CRF due to neuromuscular diseases or chest walldisorders treated with NIV scheduled for a follow-up visit. All patients underwent the screening test panel (clinical evaluation, daytime arterial blood gas (ABG), nocturnal pulse oximetry (SpO2) and data from ventilator software) and the reference tests; sleep polygraphy and nocturnal transcutaneous CO2. Results Of 67 patients included, NH was confirmed in 23–50 according to the 3 definitions used for NH, apnea-hypopnea index (AHIpolygraphy) ≥ 10 was confirmed in 16 and patient-ventilator asynchrony (PVA) ≥ 10% of total recording time in 14. Sensitivity of the combined screening test panel for NH was 87% (95% confidence interval 66–97), 84% (66–95) and 80% (66–90), for abnormal AHIpolygraphy 91% (59–100) and for PVA 71% (42–92). Sensitivity for NH of SpO2 was 48% (27–69), 39% (22–58) and 38% (24–53) and of daytime ABG 74% (52–90), 74% (55–88) and 68% (53–80). Sensitivity and specificity of AHIsoftware for AHIpolygraphy ≥ 10 was 93% (68–100) and 92% (81–98) respectively. Discussion In patients treated with long term NIV, screening test panel, nocturnal SpO2 and daytime ABG all failed to accurately detect NH, underlining the importance of nocturnal monitoring of CO2. AHIsoftware accurately identified obstructive events and can be used to modify NIV settings