Dust clouds and spread of infection

Dust clouds and spread of infection

CORRESPONDENCE tube placement in stroke patients should not be encouraged before more is known about the incidence of pneumonia after tube placement...

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tube placement in stroke patients should not be encouraged before more is known about the incidence of pneumonia after tube placement.

Ouchi Y. Simple two-step swallowing provocation test for elderly patients with aspiration pneumonia. Lancet 1999; 353: 1243.

Kiyohisa Sekizawa Division of Respiratory Medicine, Institute of Clinical Medicine, University of Tsukuba, Tsukuba City, Ibaraki 305-8575, Japan 1



Dziewas R, Ludemann P, Konrad C, Stogbauer F. Simple method for placing nasogastric tubes in patients with dysphagia. Lancet 2001; 358: 725–26. Wynne JW, Modell JH. Respiratory aspiration of stomach contents. Ann Intern Med 1977; 87: 466–74. Nakajoh K, Nakagawa T, Sekizawa K, Matsui T, Arai H, Sasaki H. Relation between incidence of pneumonia and protective reflexes in post-stroke patients with oral or tube feeding. J Intern Med 2000; 247: 39–42.

Sir—Rainer Dziewas and colleagues’ report1 prompted us to try placing nasogastric tubes by their method in patients with dysphagia after stroke, because we have many patients older than 80 years who need tube feeding but who have difficulty swallowing the tubes spontaneously. 23 patients (mean age 86·7) with various degrees of cerebral infarction were enrolled in our study. By use of the swallowing reflex, we successfully placed tubes in 19 of 23 attempts. In three patients swallowing reflex could not be provoked, and in one, vomiting accompanied by severe coughing stopped the placement of nasogastric tubes. Large amount of sputa and secretions in the oropharynx frequently prevented induction of the swallowing reflex by injection of distilled water. Sufficient aspiration of these secretions should be done before this procedure. In our successful trials, we compared the latent time between water injection (1·0 mL) through a small nasal catheter (internal diameter 0·5 mm) and swallowing, between a supine position and minimum 30 degree head-up tilt position, as used by Teramoto and colleagues.2 Latent time was significantly shorter in the head-up tilt position than in the supine position (mean 2·16 vs 2·97 s, p=0·048). The tilt position might aid more rapid insertion of the tubes. *Ken-ichiro Inoue, Takano Horohisa, Takashi Yamada, Yukihiro Tsuchida, Toshikazu Yoshikawa *Frist Department of Internal Medicine, Naka Central Hospital, Naka-gun, Ibaraki Prefecture, 311-0134 Kyoto, Japan; and Prefectural University of Medicine, Kyoto (e-mail: [email protected]) 1


Dziewas R, Ludermann P, Konrad C, Stogbauer F. Simple method for placing nasogastric tubes in patients with dysphagia. Lancet 2001; 358: 725–26. Teramoto S, Matsuse T, Fukuchi Y,

Dust clouds and spread of infection Sir—In the Caribbean some days are hazy with a seemingly high amount of dust on our vehicles. These are signs that the Sahara dust is in the air. People are believed to be more allergic on such days, although I know of no proof of this effect. In his Aug 11 news item,1 Mike McCarthy reports on the role of Saharan dust as a vehicle for the spread of human and other infection, and even as a possible trigger to asthma in the Caribbean. Some evidence suggests that the prevalence of asthma has risen in the Caribbean since 1970, about the same time that McCarthy notes a rise in the amount of African dust arriving in the Caribbean. In 1969–70, Pearson2 did a survey of school-aged Barbadian children for symptoms of asthma. Prevalence of asthma was just more than 1%. In 1996, the Barbados National Asthma and Allergy Survey assessed the prevalence of asthma among children aged 6–7 years and 12–13 years: prevalence exceeded 15% in each group.3 In the acute asthma care facility at the Queen Elizabeth Hospital in Barbados, the main accident and emergency facility for the island, there was a tenfold increase in the number of patients attending for acute asthma treatment between 1970 and 1995. During this period the population rose by only 10%.3 Although these increases might be due to confounding variables such as improved diagnosis of the disease, could there also be some relation with the increased exposure to African dust? More patients attend accident and emergency departments across the Caribbean in the rainy season (midMay to December) than in the dry season (January to mid-May). The number of admissions rises sharply and starts from September to November or December from Trinidad in the south to Antigua in the north.3 According to McCarthy, the African dust reaches the Caribbean in summer, which presumably coincides with our rainy season. Studies of climatic variables in relation to asthma admission to accident and emergency departments have been done in Trinidad and Barbados.4 Humidity and wind speed are most closely linked to asthma admissions. A high humidity and low wind speed might facilitate settling of dust particles that could be inhaled.

THE LANCET • Vol 359 • January 5, 2002 • www.thelancet.com

Climate, however, explains only 8% of variation in adult and paediatric admissions.4 Could climatic variables affect indirectly? In Trinidad, there is a lag period of about 3 months between the onset of the rainy season and the rise in acute asthmatic admissions. Curiously, July and August have low admission rates. Could increase of plant-derived or other allergens be associated with the African dust? Finally, Blades and colleagues5 have attempted to correlate Sahara dust days with asthma admissions in Barbados, but have seen no correlation. However, we in the Caribbean must continue to investigate the potential impact of the African dust on our health and fragile economies. To this end, I hope the workers will see fit to work with regional people in analysing the infectious and non-infectious impact of the Sahara dust on our island states. Michele A Monteil Department of ParaClinical Sciences, Faculty of Medical Sciences, University of the West Indies, Trinidad, West Indies (e-mail: [email protected]) 1

2 3



McCarthy M. Dust clouds implicated in spread of infection. Lancet 2001; 358: 478. Pearson RSB. Asthma in Barbados. Clin Allergy 1973; 3: 289–97 Monteil MA. Asthma in the English-speaking Caribbean. West Indian Med J 1998; 47: 125–28. Ivey MA, Simeon DT, Juman S, Hassanally R, Williams K, Monteil MA. Association between climate variables and asthma visits to accident and emergency facilities in Trinidad, West Indies. Allergol Intl 2001; 50: 29–33. Blades E, Naidu R, Mathison G. The microbial analysis of Sahara dust and its association with asthma in Barbados. West Indian Med J 1998; 47 (suppl 2): 34–35.

Sir—Michael McCarthy1 describes the role of north African desert dust clouds in the long-distance carriage of infectious micro-organisms and warns that drought conditions have increased levels of atmospheric aerosols with potential implications to the spread of infection. Dust may also facilitate the development of disease through other mechanisms. Epidemics of meningococcal meningitis occur throughout sub-Saharan Africa, most frequently in an area, known as the meningitis belt, that stretches from the Sahelian zone of west Africa to the Hom of Africa. This region is a major source of atmospheric dust over most of north Africa and has epidemics and seasonal upsurges in endemic disease in the latter part of the dry season, characterised between November and May by low absolute humidity and the dust-laden Harmattan trade winds.


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