Objective: We reviewed data of 208 episodes of acute respiratory failure due to chronic obstructive pulmonary disease treated by non-invasive ventilation (NIV) in our Respiratory Intensive Care Unit (RICU) from its opening in 1992 to 1999.
Material and methods: We assessed whether the rate of NIV success, the severity of the disease, and the associated costs changed in this period during which the staff and the equipment did not change.
Results: The failure rate was constant over the years (17.2% on average). The severity of the episodes of ARF, defined by pH and APACHE II at admission, worsened during the years. The statistical change point test allowed us to identify 1997 as the year of a significant change in the severity of admission pH and therefore to identify two different periods: 1992-1996 (mean pH = 7.25+/-0.07) and 1997-1999 (7.20+/-0.08; P<0.001). In this latter period the risk of failure for a patient with a pH <7.25 was threefold lower than in 1992-1996. In 1997-1999 an increasing number of episodes of ARF with a pH >7.28 were treated in the Medical Ward (20% vs 60%). This allowed a significant reduction of daily cost per patient treated with NIV (558+/-8 Euros vs 470+/-14 Euros, respectively; P<0.01).
Conclusions: We conclude that, over time, experience with NIV may progressively allow more severely ill patients to be treated without changing the rate of success. The daily cost of NIV per patient can be reduced by treating less severely ill patients outside the RICU.