REBUTTAL FROM DR. ROSSI

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At the end of his article, Dr. Hill reminds us that "This goes with the usual disclaimer that more studies are clearly needed." And sure, Dr. Hill is an honorable man (1). But how can he not appreciate the profound inconsistency between this wise conclusion and the tough initial statement that "Noninvasive ventilation has been shown to be ineffective in severe stable COPD"? If this ineffectiveness was shown so clearly and unquestionably, why do we need further expensive and time- consuming studies? To keep people (patients, nurses, residents, statisticians, etc.) busy during several otherwise tedious weekends? Wouldn't you rather be sailing?

Dr. Hill reports the study by Shapiro and colleagues (2) to support his view. But there are several problems involved in using that study in this manner. First, it was designed based on the assumption that chronic respiratory muscle fatigue exists in advanced COPD, without any concern for CO₂ retention. Second, a cumbersome device was used to apply intermittent negative pressure ventilation (NPV), with adverse consequence on patients' compliance. Third, NIV was applied during the day. The Shapiro study shows that daytime intermittent application of NPV is not indicated as a routine practice in severe stable COPDnothing more than that. Any extrapolation from these data to support the "ineffectiveness" statement goes far beyond the scientific content of that study. By contrast, Gutierrez and colleagues (3) observed that NPV did improve respiratory function in hypercapnic COPD patients. Should that observation be dismissed with contempt because it is not coming from an RCT? RCTs are essential, but it does not advance science to restrict medical knowledge to RCTs alone.

  I speak not to disprove what Dr. Hill spoke,

  but here I am to speak what I do know (1).

In Dr. Hill's article, the negative study of Strumpf and colleagues (4) is cited to counterbalance the positive trial of Meecham-Jones and colleagues (5). This won't work. First, the so-called milder hypercapnia (46 mm Hg, on average) of Strumpf's patients is in the upper bound of the normocapnic range. Nobody with any common sense would think to ventilate patients with those Pa_CO2 values. Second, one would like to know why 14 patients finished Meecham-Jones's study, whereas only 7 completed the Strumpf trial. Third, Meecham-Jones's patients (5) had a higher number of hypopneas per hour (around 10) than Stumpf's patients (apnea-hypopnea index < 5) (4). This difference might well reflect the higher Pa_CO2 of one study (5) compared to the other (4), rather than of patients with "overlap" syndrome (5) versus uncontaminated COPD (4).

Finally, Dr. Hill concludes that "these differences (4, 5), combined with findings from the negative pressure ventilator studies (2), suggest that NIV is ineffective in stable COPD patients."

  O masters! If I were dispos'd to stir

  Your hearts and minds to mutiny and rage,

  I should do Dr. Hill wrong . . . 

  Who, you all know, is an honourable man (1).

The correct conclusion is that both the Shapiro (2) and Strumpf (4) studies discourage long-term ventilation in severe stable COPD without significant hypercapnia. By contrast, in addition to several physiologic studies, the Meecham-Jones study (5) demonstrates that nocturnal ventilation provides significant physiologic and clinical benefits to severe stable COPD with significant hypercapnia.

To view the data otherwise would require excessive extrapolation on one hand and rigidity on the other hand, along with unrestrained pessimism.

  O judgement, thou are fled to brutish beasts.

  and men have lost their reason (1).

	References

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1. Shakespeare, W. 1998. Julius Caesar. BUR, Torino, p. 120-122.

2. Shapiro, S. H., P. Ernst, K. Gray-Donald, and et al. 1992. Effect of negative pressure ventilation in severe chronic obstructive pulmonary disease. Lancet 340: 1425-1429 [Medline].

3. Gutierrez, M., T. Berolza, G. Confreras, and et al. 1988. Weekly cuirass ventilation improves blood gases and inspiratory muscle strength in patients with chronic air-flow limitation and hypercapnia. Am. Rev. Respir. Dis. 138: 617-623 [Medline].

4. Strumpf, D. A., R. P. Millman, C. C. Carlisle, L. M. Grattan, S. M. Ryan, A. D. Erickson, and N. S. Hill. 1991. Nocturnal positive-pressure ventilation via nasal mask in patients with severe chronic obstructive pulmonary disease. Am. Rev. Respir. Dis. 144: 1234-1239 [Medline].

5. Meecham-Jones, D. J., E. A. Paul, P. W. Jones, and J. A. Wedzicha. 1995. Nasal pressure support ventilation plus oxygen therapy alone in hypercapnic COPD. Am. J. Respir. Crit. Care Med. 152: 538-544 [Abstract].