In-hospital death in patients with chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is escalating in importance in the United States. With an aging population and the continued effects of cigarette smoking, the number of patients with COPD is growing. COPD is the fourth leading cause of death in the United States. (1) In COPD, the obstructive defect is incompletely reversible with bronchodilator therapy and is progressive. After an exacerbation, there is often a decline in quality of life and requirement for readmission within the next 6 months. (2)

Acute exacerbations of COPD may require hospitalization, with severe respiratory failure requiring intensive care unit admission. Studies have shown the benefits of inhaled bronchodilator therapy, corticosteroids, antibiotics, and oxygen. (2) Noninvasive positive-pressure ventilation is frequently used in patients with COPD exacerbation, especially patients with hypercapnia, and has been successful in averting intubation. Lower mortality rates and reduced rates of nosocomial infections have been attributed to management with noninvasive compared with invasive ventilation. (3) Mechanical ventilation in patients with obstructive lung disease carries the hazard of dynamic hyperinflation, with its sequelae of hypotension and barotrauma.

One recent study of outpatients with COPD found that death could be predicted by integrating four factors: the body mass index, a measure of airflow obstruction (FE[V.sub.1]), dyspnea score, and exercise measured by the 6-minute walk. (4) Reliable markers of death among patients hospitalized with COPD exacerbation are not established. Studies have shown an in-hospital mortality rate of 2.5 to 11% (5-7) and a higher mortality rate of 24 to 28% among patients requiring mechanical ventilation. (6,8,9) Predictors of inpatient mortality have included age, degree of airflow obstruction, the presence of hypercapnia, and need for mechanical ventilation. Death after a hospitalization is elevated, with 1-year death reported in the range of 23 to 43%. (5,7,10)

In contrast to FE[V.sub.1], measurement of peak expiratory flow (PEF) has not been studied as extensively as a predictor of outcome in patients with COPD. In one study of outpatient subjects with COPD, PEF was found to be equal to best FE[V.sub.1] in predicting death. (11) PEF showed better association with body mass index, possibly reflecting the effect of muscle strength on this maneuver. (11) A low PEF rate after bronchodilator therapy surely identifies severe expiratory airflow obstruction. The PEF is an essential measure of severity and response to therapy in severe asthma, (12) but it has not traditionally been applied to acute COPD management. The PEF measured during the acute COPD exacerbation may be more relevant than the baseline FE[V.sub.1].

The study by de la Iglesia et al (13) published in this month's issue of the Journal investigates factors related to death in patients hospitalized with COPD exacerbation. The authors examined 284 patients admitted to a short-stay unit in Spain for COPD exacerbation. There were 11 in-hospital deaths, yielding a mortality rate of 3.9%, which is in the range of other studies reported in the literature. (5-7) The authors identified three independent predictors of death: the PEF, requirement for long-term oxygen therapy, and the body mass index.

The authors conclude that a PEF below 150 L/min best predicts death, while recognizing that the study is limited by the small number of deaths. Although the low specificity and likelihood ratio for death reveal the PEF to be of limited value as a predictor of death, this test may be helpful in concert with the clinician's judgment. In clinical practice, the utmost attention must be paid to COPD patients with marked tachypnea and depressed level of consciousness, which were also found to be univariate death predictors in this study.

Early identification of the patient at risk for death may prompt early triage to critical care, administration of aggressive medical therapies, and perhaps even initiation of noninvasive ventilation. Even if mechanical ventilation is required, there remains a good prospect of survival with appropriate critical care. For some patients, such information about outcome may encourage advance planning. (5) As we can expect to care for more patients hospitalized with COPD exacerbations, clinical information that leads to increased vigilance, enhanced management, and improved patient understanding and decision-making should be welcome.

The doctor of the future will prescribe no drugs but will interest his
patients in the care and nutrition of the human frame and in the cause
and prevention of disease.
--Thomas Edison

Accepted October 20, 2004.

Please see "Peak Expiratory Flow Rate as Predictor of Inpatient Mortality in Patients with Chronic Obstructive Pulmonary Disease" on page 266 of this issue.

References

1. Mannino DM, Homa DM, Akinbami LJ, et al. Chronic obstructive pulmonary disease surveillance: United States, 1971-2000. MMWR Surveil Summ 2002;51:1-16.

2. Snow V, Lascher S, Mottur-Pilson C, et al. Evidence base for management of acute exacerbations of chronic obstructive pulmonary disease. Ann Intern Med 2001;134:595-599.

3. Girou E, Brun-Buisson C, Taille S, et al. Secular trends in nosocomial infections and mortality associated with noninvasive ventilation in patients with exacerbation of COPD and pulmonary edema. JAMA 2003;290:2985-2991.

4. Celli BR, Cote CG, Marin JM, et al. The body-mass index, airflow obstruction, dyspnea, and exercise capacity index in chronic obstructive pulmonary disease. N Engl J Med 2004;350:1005-1012.

5. Connors AF, Dawson NV, Thomas C, et al. Outcomes following acute exacerbation of severe chronic obstructive lung disease. Am J Respir Crit Care Med 1996;154:959-967.

6. Patil SP, Krishnan JA, Lechtzin N, et al. In-hospital mortality following acute exacerbations of chronic obstructive pulmonary disease. Arch Intern Med 2003;163:1180-1186.

7. Groenewegen KH, Schols AMWJ, Wouters EFM. Mortality and mortality-related factors after hospitalization for acute exacerbation of COPD. Chest 2003;124:459-467.

8. Seneff MG, Wagner DP, Wagner RP, et al. Hospital and 1-year survival of patients admitted to intensive care units with acute exacerbations of chronic obstructive pulmonary disease. JAMA 1995;274:1852-1857.

9. Nevins ML, Epstein SK. Predictors of outcome for patients with COPD requiring invasive mechanical ventilation. Chest 2001;119:1840-1849.

10. Almagro P, Calbo E, de Echaguen AO, et al. Mortality after hospitalization for COPD. Chest 2002;121:1441-1448.

11. Hansen EF, Vestbo J, Phanareth K, et al. Peak flow as predictor of overall mortality in asthma and chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2001;163:690-693.

12. Corbridge TC, Hall JB. The assessment and management of adults with status asthmaticus. Am J Respir Crit Care Med 1995;151:1296-1316.

13. de la Iglesia F, Diaz JL, Pita S, et al. Peak expiratory flow rate as predictor of inpatient mortality in patients with chronic obstructive pulmonary disease. South Med J 2005;98:266-272.

Janet M. Shapiro, MD

From the Medical Intensive Care Unit, St. Luke's-Roosevelt Hospital Center, New York, NY.

Reprint requests to Dr. Janet M. Shapiro, Division of Pulmonary and Critical Care Medicine, St. Luke's-Roosevelt Hospital Center, 1111 Amsterdam Ave., New York, NY, 10025. Email: [e-mail]