JMPT October 2002 • Volume 25 • Number 8
To the editor
Congratulations to Dr Bronfort and the team of researchers at NWCC who recently published the results of their pilot trial of chiropractic manipulative therapy (CMT) for the treatment of asthma.[1]
It adds to a curious trend reported in the literature, namely that patients report improvement in their asthma after a course of CMT. Consistent with previous literature reports, the patient-reported improvements in this study do not appear to be significantly superior to the improvements that are also reported in the sham manipulation control group.[1-3]
Unfortunately, like other attempted placebo controlled trials of chiropractic manipulation for asthma, this study appears to suffer from a serious design flaw and relies on certain assumptions made by the investigators that may not be supported by the literature.
One obvious problem in this study that is common to studies of physical-type treatments in general is an inadequate placebo treatment in the control or sham group. It is not inadequate in the classical sense of lacking a control group but inadequate in the sense that the sham control may be introducing a second active treatment in the supposed inert placebo intervention. The sham procedure used in this study requires some questionable assumptions.
According to the authors, the sham treatment in this study incorporated a “drop” type manipulation.[1] This would appear to be the identical sham manipulative intervention described and used in a previous study of chiropractic manipulation for asthma.[3] In fact, one of the investigators of the current pilot trial, Dr Bronfort, was also one of the coauthor's of the study published in Clinical Experimental Allergy. The sham manipulation was described as follows.
In the description(s) of the sham manipulation in these studies, the authors' suggest that no direct manipulative thrust was applied to the patient's spine. The tension of the drop mechanism was set merely enough to support the weight of the patient. “While no direct thrust was applied to the spine, the patient experienced a rapid momentary change of the position of the spinal section under influence, very similar to an active treatment.”[1,3] Citing Brennan et al [4], Nielson states that “similar maneuvers have been shown to be acceptable placebo treatments.”
Using a sham intervention designed for lower back pain in a trial for asthma assumes that chronic lower back pain and asthma have similar etiologies and neurobiologic mechanisms[3] and is questionable. If chiropractic manipulation can offer benefit to patients with asthma (which at least from a patient's perspective it appears to do), the likely mechanism is by modulation of the nervous system and its interaction with immune function in the airway.[5-7] It is not at all clear that chronic lower back pain has the same or even similar nervous system–immune interactions as those found in the physiopathology of asthma.
The use of this sham control further presupposes that the effects of chiropractic manipulative therapy are related to the force of the manipulative thrust rather than the subsequent movement of the vertebrae. Brennan et al
[4] demonstrated that manipulative thrusts in the neighborhood of 900 N caused a posttreatment increase in Substance P. Further postulating that manipulations of force less than those shown to cause elevated manipulative procedures for asthma based on these criteriais dangerous for the following reasons: (1) It fails to consider that elevated Substance P levels in asthmatic patients may actually increase signs and symptoms of asthma[7,8] (potentially diluting the improvement seen in the treatment group), and (2) it ignores the fact that manipulative procedures with forces less than 900 N, while not elevating levels of Substance P, are known to cause significant alternations in the nervous system that are similar to those of forceful manipulation[9,10,11-13] (potentially effecting nerve-immune interactions in the airways and causing an unintended treatment effect in the sham group).
These potential confounding variables do not appear to be adequately controlled for in any of the published studies of the chiropractic treatment of asthma.[1-3] Better study design is essential to tease out the reason(s) why patients report improvement in their asthma after CMT. It is impossible to determine from the published studies to date whether the reported improvements are the result of a specific effect of CMT on the nervous system, a nonspecific effect of CMT, or a result of some other aspect of the patient encounter. I hope Dr Bronfort and his team will consider these concerns when they design their full-blown RCT.
George W. Kukurin, DC
2415 Sarah St., Pittsburgh, PA 15203, USA
Correction
In a Letter to the Editor by George W. Kukerin in the October 2002 issue, an error appeared in the text on page 541. Beginning with the second sentence of the second paragraph on that page, the text should read as follows:
Brennan et al[4] demonstrated that manipulative thrusts in the neighborhood of 900 N caused a posttreatment increase in Substance P,[7] further postulating that manipulations of force less than those shown to cause elevated substance P levels could be used as a sham manipulation.[7] Developing true and sham manipulative procedures for asthma based on these criteria is dangerous for the following reasons: . . .
We apologize for the error and regret any confusion it may have caused.
References
1. Bronfort G, Evans RL, Kubic P, Filkin P. Chronic pediatric asthma and chiropractic spinal manipulation: a prospective clinical series and randomized clinical pilot study. J Manipulative Physiol Ther 2001;24:369-77.
2.
Balon J, et al.
A Comparison of Active and Simulated Chiropractic Manipulation as Adjunctive Treatment
for Childhood Asthma
New England Journal of Medicine 1998; 339(15): 1013-1020
3. Nielson NH, Bronfort G, Bendix T, Madsen F, Wecke B. Chronic asthma and chiropractic spinal manipulation: a randomized clinical trial. Clin Exp Allergy 1995;25:80-8.
4.
Brennan PC, Kokjohn K, Kaltinger CJ, Lohr GE, Glendening C, Hondras MA, McGregor M.
Enhanced Phagocytic Cell Respiratory Burst Induced by Spinal Manipulation: Potential Role of Substance P
J Manipulative Physiol Ther 1991 (Sep); 14 (7): 399–408
5. Barnes PJ. Neuroeffector mechanisms: the interface between inflammation and neuronal responses. J Allergy Clin Immunol 1996;98:S73-81discussion S81-3.
6. Carr MJ, Undem BJ. Inflammation-induced plasticity of the afferent innervation of the airways. Environ Health Perspect 2001;109(Suppl 4):567-71.
7. Choi DC, Kwon OJ. Neuropeptides and asthma. Curr Opin Pulm Med 1998;4:16-24.
8. Joos GF. Potential usefulness of inhibiting neural mechanisms in asthma. Monaldi Arch Chest Dis 2000;55:411-4.
9. Fujimoto T, Uchida S, Suzuki A, Meguro K. Arterial tonometry in the measurement of the effects of innocuous mechanical stimulation of the neck on heart rate and blood pressure. J Auton Nerv Syst 1999;75:109-15.
10. Pickar JG, Wheeler JD. Response of muscle proprioceptors to spinal manipulative–like loads in the anesthetized cat. J Manipulative Physiol Ther 2001;24:2-11.
11. Purdy WR, Frank JJ, Oliver B. Suboccipital dermatomyotomic stimulation and digital blood flow. J Am Osteopath Assoc 1996;96:285-9.
12. Cottingham JT, Porges SW, Lyon T. Effects of soft tissue mobilization (Rolfing pelvic lift) on parasympathetic tone in two age groups. Phys Ther 1988;68:352-6.
13. Cottingham JT, Porges SW, Richmond K. Shifts in pelvic inclination angle and parasympathetic tone produced by Rolfing soft tissue manipulation. Phys Ther 1988;68:1364-70.
