2002 NIPPV for Acute Hypercapnic Respiratory Failure in Patients with COPD: A Prospective Follow-up Study
Dr Veronica Lee Chan, United Christian Hospital
Abstract Background
Non-invasive positive-pressure ventilation (NIPPY) is increasingly used in
patients with chronic obstructive pulmonary disease (COPD) to reduce the
mortality associated with acute hypercapnic respiratory failure (AHRF).
Previous studies had mainly focused on the acute outcomes. This study
aimed to evaluate the clinical outcome beyond the index admission.
Method
Design:
Prospective observational study
Setting:
Respiratory high-dependency area in a regional public hospital in
Hong Kong
Patients:
100 consecutive patients admitted to respiratory high-dependency area
being treated with NIPPY for their acute respiratory failure from
1/10/2000 to 30/6/2001. Only COPD patients with acute hypercapnic
respiratory failure were included for final analysis.
Main Outcome Measures
Primary outcome measure is survival after index episode of acute
hypercapnic respiratory failure. Secondary outcome measure is time to any
post-discharge adverse outcomes, including either death or subsequent
episodes of acute hypercapnic respiratory failure requiring re-institution of
NIPPY or endotracheal intubation. We also attempt to identify factors from
the baseline characteristics that are predictive of these outcomes.
Results
One hundred consecutive patients had been non-selectively recruited from
1 October 2000 to 30 June 2001. Eighty-nine COPD patients with acute
hypercapnic respiratory failure were included for the final analysis (70 men
and 19 women; mean age = 73.0 ::I:: 8.6 years). Thirty-nine patients had
refused intubation if they failed to respond to NIPPY. NIPPV was given by
a Bi-level Positive Airway Pressure (BiPAP) device through a nasal or
oronasal mask. Mean NIPPV use was 3.7::1::2.8 days. In-hospital mortality was 18.0%, and the mean length of hospital stay for the index admission
was 24.2::1::16.3 days. Seventy-three patients (82%) were able to be
discharged after the current episode of acute respiratory failure.
Kaplan-Meier estimate of survival rate at one year after individual date of
discharge from the index admission was 60.6::1::6.4%.Multivariate Cox
regression analysis had shown that poor pre-morbid Katz's ADL score
(adjusted hazard ratio [AHR] = 3.1, 95% confidence interval [CI] 1.3-7.0,
p= 0.008) and length of hospital stay for more than 30 days in the past one
year (AHR=3.2, 95% CI 1.2-8.3, p=0.017) being independent predictors for
increased post-discharge mortality. Forty-five patients (61.6%) developed
one of the adverse events during their post-discharge follow up. Median
time to the development of any adverse outcome was 246 days (95% CI
161-331 days). Length of hospital stay for more than 30 days in the past
one-year was found to be the only independent predictor for early
development of post-discharge combined adverse event (AHR=2.9, 95% CI
1.5-5.9, p=0.002).
Conclusion
Post-discharge progress, in terms of survival and combined adverse events
in COPD patients treated with NIPPY for their acute hypercapnic
respiratoary failure were systematically described. Pre-morbid ADL
functional status and hospital stay in the past one-year were more important
predictors for post-discharge mortality and combined adverse outcome.
Identification of these high-risk patients might form the basis of future
randomized controlled trials in formulating strategies to improve
post-discharge outcome in COPD patients requiring NIPPY for AHRF.
