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Abstract
Introduction NIV for acute hypercapnic respiratory failure (AHRF) in COPD, obesity related morbidity, chest wall and neuromuscular conditions has become widespread in the UK over the past decade. In terms of acute NIV set up, the BTS/Royal College of Physicians/Intensive Care Society 2008 guidance recommends starting with an inspiratory positive airway pressure (IPAP) of 10 cm H2O and expiratory positive airway pressure(EPAP) of 4–5 cmH2O, with small increments in IPAP aiming for apressure target of 20 cm H2O or until therapeutic response is achieved. We felt it necessary to analyse trends in maximum pressures achieved in the evolution of a respiratory ward-based NIV Unit (established2004).
Methods Comparison of the in-house NIV registry data01/08/2004 –31/01/2006(Period 1) with 01/01/2011–30/06/2012 (Period 2) at an 11-bedded ward-based NIV unit within a1000-bedded hospital Trust in central England, looking at maximum IPAP and maximum EPAP achieved. There were 281 episodes of AHRF treated in Period 1 and 240 in Period 2 with similar distribution of gender.
Results Maximum IPAP achieved for period 2 was significantly higher than period 1 (median IPAP max achieved=20 cmH2O vs. 14 cmH2O; Wilcox on rank sum test p=2.2 × 10–16) and the maximum EPAP achieved for period 2 was higher than period 1 (median EPAP max achieved=5 cmH2O vs. 14 cmH2O; Wilcoxonrank sum test p=8.068 × 10–6).
Discussion We have previously shown that we achieved adequate therapeutic response with median IPAP max of 16.7 and median EPAP max of 5.2 cmH2O (Ali A et al. Pressure support in acute hypercapnic respiratory failure in an acute clinical setting. European Respiratory Journal 2011; 38:55. 683s.). However, as the ward-based, physiotherapy-intensive, multidisciplinary NIV service matures over an 8-year period, we are achieving significantly higher maximum IPAP and maximum EPAP. This is probably (a) in keeping with the increasing severity of AHRF that is being treated in the unit with similar in-hospital mortality (around 22%) and (b) demonstrates a learning curve. Further analysis of population characteristics and comparison with units of similar size may give further insights intoorganisational learning in relation to NIV.
Comparison of the distribution of the maximum IPAP achieved
Comparison of the distribution of the maximum EPAP achieved