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Communications to the Editor |

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Richard S. Irwin, MD, FCCP
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Division of Pulmonary, Allergy, and Critical Care Medicine University of Massachusetts Medical School Worcester, MA



Chest. 1999;115(2):602-603. doi:10.1378/chest.115.2.602-a
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To the Editor:

Because of space constraints, the Consensus Panel Report of the American College of Chest Physicians on “Managing Cough as a Defense Mechanism and as a Symptom,”1 while comprehensive, could not be as exhaustively complete as the panel members would have liked. Consequently, although (1) the protective role of cough as a defense mechanism against aspiration, (2) acute and chronic cough caused by a variety of aspiration syndromes in adults and children, and (3) the importance of having a high index of suspicion for aspiration in the elderly patient with cough because the classic signs and symptoms of aspiration may be minimal or nonexistent1 are issues mentioned in multiple places throughout the document, Drs. Teramoto, Matsuse, and Ouchi have correctly noted that the age-related changes in the cough reflex were not specifically mentioned. I thank them for doing so.

Given the opportunity to expand upon the discussion of aspiration and taking the lead of Drs. Teramoto, Matsuse, and Ouchi, I believe the possibility that an aspiration syndrome is causing any pulmonary problem should be considered in every patient, but especially in elderly, debilitated, or sedated patients with unexplained deterioration in pulmonary status and in any patient presenting with a potential aspiration syndrome2 (Table 1 ). While a compromised cough reflex places patients at risk for an aspiration syndrome, I believe that one should not solely consider respiratory defense mechanisms against aspiration. The situation is much more complicated. For instance, there are other nonrespiratory, airway-protective mechanisms that also may be dysfunctional and play an equal or more important role.

Shaker3 has divided airway protective mechanisms into the following two categories: (1) protective mechanisms against anterograde aspiration (ie, aspiration during swallowing); and (2) protective mechanisms against retrograde aspiration (ie, aspiration during reflux of gastric contents). In managing our patients with aspiration syndromes, I believe that it is important to consider and assess the adequacy of mechanisms against deglutitive aspiration ,2,,4,,5,,6,,7,,8 and to consider that airway protective mechanisms against gastroesophageal, esophagopharyngeal, and pharyngolaryngeal reflux may be inadequate.3 In regard to the latter, it appears, based upon experimental studies in human volunteers, that these mechanisms are multiple and involve delicate interaction between upper gastrointestinal and upper respiratory tracts.3

Shaker3 divides airway protective mechanisms against retrograde aspiration into the following two groups: (1) basal mechanisms that include competence of lower and upper esophageal sphincters; and (2) response mechanisms that include secondary esophageal peristalsis, esophago-upper esophageal sphincter contractile reflex, esophagoglottal closure reflex, pharyngo-upper esophageal contractile reflex, pharyngoglottal adduction (closure) reflex, and pharyngeal (secondary) swallow. The roles and relative importance of these protective mechanisms in patients with aspiration syndromes await future investigation.

I also believe that it is important to stress that clinically significant aspiration can be entirely silent, including the absence of cough.9This issue has been prospectively assessed using videofluoroscopic tapes of modified barium swallow procedures in two studies in stable patients receiving long-term mechanical ventilation via tracheostomy.10,,11 Both studies showed that bedside evaluations to exclude swallowing dysfunction were insensitive and should only be counted on as a screening procedure to detect gross disturbances. In one of the studies,10 aspiration occurred in 50% of patients and was silent in 77% of these. Choking, coughing, or respiratory distress occurred in the minority of patients who aspirated.

While the gag reflex is assessed by many to predict the adequacy of swallowing and mental alertness, theoretical considerations, and the relatively few studies do not support this practice.9 I do not believe that it should be assumed that testing for a gag reflex helps assess the risk of aspiration during swallowing for the following reasons: (1) the stimuli and the neuromuscular processes involved in gagging and swallowing are different4; (2) many normal individuals who do not have a gag reflex can swallow normally4; and (3) I am aware of no studies that show the presence or absence of a gag can predict adequacy of swallowing. Moreover, in a small study comparing obtunded patients and alert medical staff members, it was determined that the gag reflex poorly and unreliably predicted the level of consciousness.12

Correspondence to: Richard S. Irwin, MD, FCCP, Department of Medicine, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655-0330

Table Graphic Jump Location
Table 1. The Spectrum of Aspiration Syndromes2*
* 

This listing is not meant to be all inclusive.

References

Irwin, RS, Boulet, LP, Cloutier, MM, et al (1998) Managing cough as a defense mechanism and as a symptom: a consensus panel report of the American College of Chest Physicians.Chest114(Suppl),133S-181S
 
Irwin RS. Aspiration. In: Irwin RS, Cerra FB, Rippe JM, eds. Intensive care medicine. 4th ed. Philadelphia, PA: Lippincott-Raven Publishers, 1999, 685–692.
 
Shaker, R Airway protective mechanisms: current concepts.Dysphagia1995;10,216-227
 
Logemann, JA Swallowing physiology and pathophysiology.Otololaryngol Clin North Am1988;21,613-623
 
Robbins, J, Hamilton, JW, Lof, GL, et al Oropharyngeal swallowing in normal adults of different ages.Gastroenterology1992;103,823-829
 
Schmidt, J, Holas, M, Halvorson, K, et al Videofluoroscopic evidence of aspiration predicts pneumonia and death but not dehydration following stroke.Dysphagia1994;9,7-11
 
Shaker, R, Dodds, WJ, Dantas, RO, et al Coordination of deglutitive glottic closure with oropharyngeal swallowing.Gastroenterology1990;98,1478-1484
 
Buchholz, DW Oropharyngeal dysphagia due to iatrogenic neurological dysfunction.Dysphagia1995;10,248-254
 
Irwin, RS, Parrillo, JE, Albert, R, et al ACCP SEEK critical care medicine, Vol. VI.1996,156 American College of Chest Physicians. Northbrook, IL:
 
Elpern, EH, Scott, MG, Petro, L, et al Pulmonary aspiration in mechanically ventilated patients with tracheostomies.Chest1994;105,563-566
 
Tolep, K, Getch, CL, Criner, GJ Swallowing dysfunction in patients receiving mechanical ventilation.Chest1996;109,167-172
 
Kulig, K, Rumack, BH, Rosen, P Gag reflex in assessing level of consciousness [letter]. Lancet. 1982;;1 ,.:565
 

Figures

Tables

Table Graphic Jump Location
Table 1. The Spectrum of Aspiration Syndromes2*
* 

This listing is not meant to be all inclusive.

References

Irwin, RS, Boulet, LP, Cloutier, MM, et al (1998) Managing cough as a defense mechanism and as a symptom: a consensus panel report of the American College of Chest Physicians.Chest114(Suppl),133S-181S
 
Irwin RS. Aspiration. In: Irwin RS, Cerra FB, Rippe JM, eds. Intensive care medicine. 4th ed. Philadelphia, PA: Lippincott-Raven Publishers, 1999, 685–692.
 
Shaker, R Airway protective mechanisms: current concepts.Dysphagia1995;10,216-227
 
Logemann, JA Swallowing physiology and pathophysiology.Otololaryngol Clin North Am1988;21,613-623
 
Robbins, J, Hamilton, JW, Lof, GL, et al Oropharyngeal swallowing in normal adults of different ages.Gastroenterology1992;103,823-829
 
Schmidt, J, Holas, M, Halvorson, K, et al Videofluoroscopic evidence of aspiration predicts pneumonia and death but not dehydration following stroke.Dysphagia1994;9,7-11
 
Shaker, R, Dodds, WJ, Dantas, RO, et al Coordination of deglutitive glottic closure with oropharyngeal swallowing.Gastroenterology1990;98,1478-1484
 
Buchholz, DW Oropharyngeal dysphagia due to iatrogenic neurological dysfunction.Dysphagia1995;10,248-254
 
Irwin, RS, Parrillo, JE, Albert, R, et al ACCP SEEK critical care medicine, Vol. VI.1996,156 American College of Chest Physicians. Northbrook, IL:
 
Elpern, EH, Scott, MG, Petro, L, et al Pulmonary aspiration in mechanically ventilated patients with tracheostomies.Chest1994;105,563-566
 
Tolep, K, Getch, CL, Criner, GJ Swallowing dysfunction in patients receiving mechanical ventilation.Chest1996;109,167-172
 
Kulig, K, Rumack, BH, Rosen, P Gag reflex in assessing level of consciousness [letter]. Lancet. 1982;;1 ,.:565
 
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