X3.2 Non-invasive positive pressure ventilation

Non-invasive ventilation (NIV) should be strongly considered in patients with an exacerbation of COPD who present with hypercapnic respiratory failure as defined on an arterial blood gas with a PaCO2 above 45mmHg and a pH less than 7.35 (Osadnik 2017) [evidence level I].

NIV is an effective and safe means of treatment of ventilatory failure. Its use allows preservation of cough, physiological air warming and humidification, and normal swallowing, feeding and speech. Applying NIV in addition to conven­tional therapy reduces the risk of mortality by 46% (risk ratio (RR) 0.54, 95% confidence interval (CI) 0.38 to 0.76); NNT 12 and decreases the risk of needing endotracheal intubation by 65% (RR 0.36, 95% CI 0.28 to 0.46; NNT 5) (Osadnik 2017). This benefit is similar for patients with mild acidosis (pH 7.30 to 7.35) versus a more severe nature (pH < 7.30), and when NIV is applied in a ward or intensive care unit (Osadnik 2017). The use of NIV reduces hospital length of stay mean difference -3.39 days (95% CI -5.93 to -0.85) (Osadnik 2017).

A local prospective observational cohort study demonstrated that ward-based NIV (managed by respiratory medical and nursing staff) compared with high dependency unit (HDU) and ICU-based NIV achieved equivalent clinical outcomes and was substantially more cost-effective (Parker 2018). These findings were replicated in a similar but retrospective study based in a teaching hospital in China (Hong 2020). The optimal location for provision of NIV should be determined by local experience and availability of expertise.

Hartley et al used a derivation cohort of 489 patients to derive a mortality prediction score for patients with with an exacerbation of COPD and hypercapnic respiratory failure receiving NIV. The NIVO score was then validated in a group of 733 patients from across 10 hospitals in England and Wales. The NIVO score consisted of 6 measures that should be available at the bedside (see below). The area under the curve form predicting mortality was 0.79.  The score also allowed for mortality risk stratification – see table below.  The NIVO score performed better in this patient group than all other mortality prediction scores tested.  Use of this score may assist clinicians, patients and their carers in making decisions regarding acute non-invasive ventilation (Hartley 2021) [evidence level III].