ACUTE RESPIRATORY FAILURE IN PATIENTS WITH SEVERE COMMUNITY-ACQUIRED PNEUMONIA: A PROSPECTIVE RANDOMIZED EVALUATION OF NONINVASIVE VENTILATION

To the Editor :

We read with interest the results of the randomized controlled trial presented by Confalonieri and colleagues (1). The authors compared noninvasive mechanical ventilation (NIMV) associated with standard medical therapy (SMT) with SMT alone in the treatment of acute respiratory failure (ARF) due to severe community-acquired pneumonia. A lower rate of endotracheal intubation and a reduced length of ICU stay in the group of patients receiving NIMV were the main findings of this interesting study.

Current evidence (2) indicates that the addition of NIMV to SMT can effectively reduce the rate of endotracheal intubation and improve the rate of survival in COPD patients with acute hypercapnic respiratory failure. In non-COPD patients requiring mechanical ventilation to treat hypoxemic ARF, Antonelli and colleagues (3) recently compared NIMV with invasive mechanical ventilation. Although the two techniques were equally effective in improving gas exchange, the length of ICU stay was significantly reduced in the group of patients receiving NIMV. However, thus far no study has definitely proved the ability of NIMV to avoid endotracheal intubation in non-COPD patients with ARF. Does the study by Confalonieri and colleagues provide new information to this regard? Not really. In fact, due to the inclusion criteria in this study, both 23 COPD patients with hypercapnic ARF and 33 non-COPD patients with hypoxemic ARF were recruited. Using a post-hoc analysis the authors provide separate results for the two subgroups of patients. NIMV did not result in any improvement or trend toward improvement in the group of non-COPD patients, while, despite the relatively small patient sample, the group of COPD who received NIMV significantly improved.

According to these data, NIMV efficacy seems to be more related to the presence of underlying COPD than to the cause that precipitates ARF. It is also indirectly suggested that the aid provided by the ventilator to the respiratory muscle pump (4) rather than the facilitated removal of secretions (1) is presumably the mechanism by which NIMV works.

We believe that further research is still required to determine whether or not NIMV can effectively improve the outcome of patients with hypoxemic ARF by preventing endotracheal intubation.

Pulmonary Unit, Baretta Rehabilitation Center, Ospedale Valduce, Costamasnaga, Italy

1. Confalonieri, M., A. Potena, G. Carbone, R. Della, Porta, E. A. Tolley, and G. U. Meduri. 1999. Acute respiratory failure in patients with severe community-acquired pneumonia: a prospective randomized controlled evaluation of noninvasive ventilation. Am. J. Respir. Crit. Care Med. 160: 1585-1591 [Abstract/Free Full Text].

2. Keenan, S. P., P. D. Kenerman, D. J. Cook, C. M. Martin, D. McCormack, and W. J. Sibbald. 1997. Effect of noninvasive positive pressure ventilation on mortality in patients admitted with acute respiratory failure: a meta-analysis. Crit. Care Med. 25: 1685-1692 [Medline].

3. Antonelli, M., G. Conti, M. Rocco, M. Bufi, R. A. De Blasi, G. Vinino, A. Gasparretto, and G. U. Meduri. 1998. A comparison of noninvasive positive-pressure ventilation and conventional mechanical ventilation in patients with acute respiratory failure. N. Engl. J. Med. 339: 429-435 [Abstract/Free Full Text].

4. Elliott, M. W.. 1995. Noninvasive ventilation in chronic obstructive pulmonary disease. N. Engl. J. Med. 333: 870-871 [Free Full Text].

From the Author s:

Oxygenation failure is the physiological end point of an heterogenous group of conditions characterized by different pathophysiologic abnormalities. Our work (1) was limited to the study of patients with severe community-acquired pneumonia and cannot be generalized to other conditions leading to severe hypoxemia. Prior to our work, only 13 patients with community-acquired pneumonia (CAP) and acute respiratory failure (ARF) were included in noninvasive positive pressure ventilation (NPPV) randomized studies (2) while other randomized studies (5, 6) excluded patients with pneumonia. Chronic obstructive pulmonary disease (COPD) is recognized as a risk factor for developing severe CAP and was included in our study. All our patients met criteria for severe hypoxemia with a Pa_O2:FI_O2 ratio less than 250. Among COPD patients with a similar severity of illness at ICU admission, we have found a significant advantage for NPPV. Among patients without COPD, those randomized to NPPV had a higher APACHE II score (p < 0.05) than controls did and had a similar outcome. By multiple logistic regression analysis we did not identify hypercapnia as a marker of NPPV success. We agree with Drs. Navalesi and Polini that a randomized study is indicated to establish the role of NPPV in ARF caused by community-acquired pneumonia in patients without COPD.

The metaanalysis conducted by Keenan and colleagues (7) reviewed the literature on NPPV published up to September 1995. Until 1996, the NPPV literature included 22 studies involving 527 patients (111 with hypoxemia ARF); since then 24 new studies have been published involving 781 patients (395 with hypoxemic ARF). Until 1996, only one randomized study included patients without COPD (8). Since then five randomized studies have been published that evaluate patients with hypoxemic ARF (1, 2, 4, 9, 10). Lately, a randomized prospective comparison of NIMV versus usual medical therapy in patients with ARF of various etiologies (11) showed that patients with hypoxemic ARF in the NIMV group had a lower intubation rate than those in the control group. Moreover, we have recently participated into a multicenter study involving 354 patients with hypoxemic ARF, which was submitted in abstract form (10). It is possible that a metaanalysis incorporating the work of the last four years will provide a more encouraging report for the use of noninvasive ventilation in selected conditions associated with hypoxemic ARF.

M. CONFALONIERI

G. U. MEDURI

Unità Operativa di Pneumologia

Ospedali Riuniti di Bergamo

Bergamo, Italy

1. Confalonieri, M., A. Potena, G. Carbone, R. Della, Porta, E. A. Tolley, and G. U. Meduri. 1999. Acute respiratory failure in patients with severe community-acquired pneumonia: a prospective randomized evaluation of noninvasive ventilation. Am. J. Respir. Crit. Care Med. 160: 1585-1591 .

2. Wood, K. A., L. Lewis, B. Von Harz, and M. H. Kollef. 1998. The use of noninvasive positive pressure ventilation in the emergency department: results of a randomized clinical trial. Chest 113: 1339-1346 [Abstract/Free Full Text].

3. Kramer, N., T. J. Meyer, J. Meharg, R. D. Cece, and N. S. Hill. 1995. Randomized, prospective trial of noninvasive positive pressure ventilation in acute respiratory failure. Am. J. Respir. Crit. Care Med. 151: 1799-1806 [Abstract].

4. Antonelli, M., G. Conti, M. Rocco, M. Bufi, R. A. De Blasi, G. Vivino, A. Gasparetto, and G. U. Meduri. 1998. A comparison of noninvasive positive-pressure ventilation and conventional mechanical ventilation in patients with acute respiratory failure. N. Engl. J. Med. 339: 429-435 .

5. Brochard, L., J. Mancebo, M. Wysocki, F. Lofaso, G. Conti, A. Rauss, G. Simonneau, S. Benito, A. Gasparetto, F. Lemaire, D. Isabey, and A. Harf. 1995. Noninvasive ventilation for acute exacerbations of chronic obstructive pulmonary disease. N. Engl. J. Med. 333: 817-822 [Abstract/Free Full Text].

6. Barbé, F., B. Togores, M. Rubi, S. Pons, A. Maimo, and A. G. Agusti. 1996. Noninvasive ventilatory support does not facilitate recovery from acute respiratory failure in chronic obstructive pulmonary disease. Eur. Respir. J. 9: 1240-1245 [Abstract].

7. Keenan, S. P., P. D. Kerneman, D. J. Cook, C. M. Martin, D. McCormack, and W. J. Sibbald. 1997. Effect of noninvasive positive pressure ventilation on mortality in patients admitted with acute respiratory failure: a metaanalysis. Crit. Care Med. 25: 1685-1692 .

8. Wysocki, M., L. Tric, M. A. Wolff, H. Millet, and B. Herman. 1995. Noninvasive pressure support ventilation in patients with acute respiratory failure: a randomized comparison with conventional therapy. Chest 107: 761-768 [Abstract/Free Full Text].

9. Antonelli, M., G. Conti, M. Bufi, M. G. Costa, A. Lappa, M. Rocco, A. Gasparetto, and G. U. Meduri. 2000. Noninvasive ventilation for treatment of acute respiratory failure in patients undergoing solid organ transplantation: a randomized trial. J.A.M.A. 283: 235-241 [Abstract/Free Full Text].

10. Antonelli, M., A. Esquinas, G. Conti, G. Gonzales, M. Confalonieri, P. Pelaia, T. Principi, C. Gregoretti, F. Beltrame, M. A. Pennini, A. Arcangeli, R. Proietti, M. Passariello, and G. U. Meduri. 1999. Risk factors for failure of noninvasive ventilation in acute hypoxemic respiratory failure: a multicenter study (abstract). Intensive Care Med. 25: S56 .

11. Martin, T. J., J. D. Hovis, J. P. Costantino, M. I. Bierman, M. P. Donahoe, R. M. Rogers, J. W. Kreit, F. C. Sciurba, R. A. Stiller, and M. H. Sanders. 2000. A randomized, prospective evaluation of noninvasive ventilation for acute respiratory failure. Am. J. Respir. Crit. Care Med. 161: 807-813 [Abstract/Free Full Text].