Introduction Use of NIV for AHRF in COPD, obesity related morbidity, chest wall and neuro muscular conditions have increased significantly over the past decade – there has been a documented 462%increase in acute NIV use in COPD (Chandra D et al. AJRCCM 2011) over 11 years in the United States with similar changes noted in smaller surveys in the UK. In the UK, this has led to the movement of NIV service provision out of critical care at ward-based NIV units. We felt it necessary to analyse temporal trends in the severity and outcomes of ward-based NIV practises.
Methods Comparison of the in-house NIV registry data 01/08/2004 –31/01/2006 (Period 1) with 01/01/2011 – 30/06/2012(Period 2) at an 11-bedded ward-based NIV unit within a 1000-bedded hospital Trust in central England, looking at mortality, length(duration) of NIV and initial arterial blood pH, the latter being widely accepted as a marker of AHRF severity.
Results There were 281 episodes of AHRF treated in Period 1 and 240 in Period 2 with similar distribution of gender (non-significant increase in the number of women); acute exacerbations of COPD constituted similar proportion (about 70%)of dominant diagnosis behind AHRF in both periods (associated risk factor documentation, e.g. kyphoscoliosis not analysed); the initial arterial blood pH was significantly lower (median initial pH 7.280 vs 7.261; Wilcoxonrank sum test: p=0.03134; pH significantly lower in Period 2); the mean length (duration) of NIV was significantly higher (median length of NIV 4.0 days vs 6.0 days; Wilcoxon rank sum test: p=0.0000018; Length of NIV is significantly higher in period 2), whilst in-hospital mortality was similar (21.6% vs. 22.7%).
Discussion Our data confirm the clinical surmise that over time, our ward-based NIV unit is treating more severely ill patients with AHRF who are spending longer periods under acute NIV with no significant change in mortality. Further analysis of population characteristics, co-morbid risk factors for respiratory failure and Domiciliary NIV/Home Mechanical Ventilation practises as well as national trends in NIV use are needed to inform health policy/strategies to deal with long term respiratory conditions.