Review for 10.1186/1471-230X-4-24 (2004)

Reviewer's report 
 The effect of straining on the diaphragmatic crura with identification of the straining-crural Title: 
reflex. The reflex theory in gastroesophagael competence: a new concept 
 1  4 February 2004 Version: Date: 
 Ravinder K Mittal Reviewer: 
Reviewer's report: 
General 
Shafik et al investigated the effects of coughing and straining on crural diaphragm EMG activity and 
lower esophageal sphincter pressure in anesthtized humans. Side hole manometry was used to 
measure LES pressure and bipolar concentric needle electrodes were used to measure EMG activity 
of the crural diaphragm. Their data show that during coughing and straining there is a large increase 
in the LES pressure as well as EMG activity of the crural diaphragm. While conclusions and finding 
seems valid there are number of concerns regarding the ethical nature of the experiment and the 
methodology used in the studies. It seems that the authors are not aware of the large amount of 
already published literature on this topic. Furthermore, this reviewer is concerned about the ethical issues in conducting the experiments. 
It is not clear how could they induced coughing and straining in the anesthetized human. I suspect 
that the subjects were kept lightly anesthetized for the experimental purposes? The method used to 
induce two different patterns during anesthesia is not properly described. Injection of lidocain into the 
crural diaphragm also does need seem to be ethical? Localized injection of anesthesia around the 
EMG needle electrode will abolish the crural EMG activity, however, that does not mean that the 
whole crural diaphragm is paralyzed by the local injection. 
As described in the previously reported studies the major problem in recording LES pressure during 
diaphragmatic contraction is that the LES moves in the aboral direction during its contraction and the 
side hole of the manometry catheter does not necessarily move with the LES thus creating a relative 
motion artifact in the recordings. Reverse perfused sleeve sensor is the best possible technique to 
measure LES pressure during diaphragmatic contraction. 
Methods of EMG quantitation are not of the international standard. In order to quantify EMG signal 
processing of these signals such as waveform rectification, integration and moving time averaging is required. 
Authors state that crural diaphragm does not share the respiratory movement of the costal 
diaphragm which is not correct. In fact the crural diaphragm moves in the oral and aboral diaphragm 
during expiration and inspiration respectively, just likely costal diaphragm. The difference, however, 
is that crural diaphragm in addition to axial movements associated with respiration also has a 
circumferential squeeze action. 
Investigators imply that lidocain blocks only the sensory fibers and not the motor fibers which is not 
correct. 
This reviewer refers these investigators to the extensive work of Dr R.K. Mittal and colleagues on the 
action of crural diaphragm in humans. 
Mittal RK, Balaban D. Esophagogastric Junction: Physiology and Pathophysiology. New England 
Journal of Medicine. 1997;336:924-32 
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