communications to the editor CommunictJfloru for thu section will be published tu IfXlCl! and prioritie8 pennit. 1fae comment& 8hould not exceed 350 words in
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Incorrect Use of Metered-Dose Inhalers 7b the Editor: In the treatment ofairway diseases, metered-dose inhalers (MDls) offer signmcant advantages over other delivery systems. I However, incorrect technique may limit efBcacy and pose unique hazards."1 I would like to alert the medical community to two additional forms ofccMDI misadventure" that I have encountered. In the 6rst case, a patient continued using an empty inhaler because "the expiration date showed it was stiD good." The second case was of a boy who consumed MOl prescriptions at twice the expected rate, alarming both his pharmacist and his physician, until the explanation became apparent-the product discharged into his back pocket every time he sat down. When properly addressed, the problems in both cases promptly resolved.
Neil Kao, M.D., FeC.C.l,
exchanger (HME) during long-term mechanical ventilation. This
work raises interesting questions about the adequate humidi6cation
of respiratory gases. As reported by the authors, the choice of the Pall Ultipore Breathing Filter BB2215 (PUBF) is probably not optimal; more efBcient hygroscopic HMEs are now available. Recent~ a study was interrupted after the death of a patient in a PUBF group because of total obstruction of the tracheal tube.1In an unpublished study, we found that the PUBF was signi6cantly less effective than two other HMEs (Hygrobac [DAR] and Humid-Vent [Gibeck Respiration» in tenns of physiologic perfonnance and clinical tolerance. Like Martin et al,1 we suspended evaluation of the PUBF during prolonged ventilation foDowing several dramatic instances of tracheal tube occlusion. Tracheal tube occlusion is not completely prevented by tracheal instillations. ' .3 In spite of the very high efBciency of the PUBF as a bacterial 6lter, we decided that its use as a passive humidi6er should de6nitely be avoided and that it should be replaced by a more effective device. Furthermore, an HME should be used no longer than 48 h; increase in thickness of bronchial secretions can be relatively occult (unproductive tracheal aspiration), developing in several hours or days and suddenly leading to acute respiratory failure requiring extraction of a bronchial cast. 3 Subjective evaluation of tracheal secretions is not always reliable. Measurement of biorheologic properties of sputum (spinnabilit>; viscosity) requires specific expensive devices, and the current data are not conclusive for application in clinical practice. 4•5 Daily bronchoscopic evaluation could be an alternative but is not defensible in clinical practice.
lJeptJr.tment of Allergy and Clinical Immunology, Rtuh-Pm,byterian-St. Luke; Medical Center; Chicago
'l1aierrrJ SottIau%, M.D., Intenlioe Care Unit,
Clinique Notre-Daml! de Grt2ce,
REFERENCES 1 Saunders KB. The limits of inhalation therclpy. Geriatr Med 1980; 2
10:9-10 Oolovich M, Ruftin RE, Roberts R, Newhouse MT. Optimal delivery of aerosols from metered dose inhalers. Chest 1981; 80:911-15 Epstein S~ Manning CPR, Ashley MJ, Corey PN. Survey of the clinical use of pressurized aerosol inhalers. Can Med Assoc J 1979; 120:813-16 Saunders KB. Misuse of inhaled bronchodilator agents. BMJ 1965; 1:1037-38 Orehek J, Grimaud C, Charpin J. Patient error in use of bronchodilator metered dose aerosols. BMJ 1976; 1:76 Li ]TC, Gundenon D. Inhalation of the cap of a metered-dose inhaler. N Engi J Med 1991; 325:431 Schultz CH, Hargarten S~ Babbitt J. Inhalation of a coin and a capsule from metered-doseinhalers. N EnglJ Med 1991;325:43132
Use of a Heat and Moisture Exchanger during Long-term Mechanical Ventilation 7b the Editor: I read with interest the data reported by Misset et all in the July 1991 issue of Che., concerning the use of a heat and moisture
REFERENCES 1 Misset B, Escudier B, Rivara 0, Leclercq B, Nitenberg G. Heat and moisture exchanger vs heated humidi6er during long-term mechanical ventilation: a prospective randomized stud~ Chest 1991; 100:160-63 2 Martin C, Perrin G, Gevaudan MJ, Saux ~ Gouin F. Heat and moisture exchangers and vaporizing humidi6ers in the intensive care unit. Chest 1990; 97:144-49 3 Perch SA, Realey AM. Effectiveness of the Servo SH 150 "Artificial Nose-- humidi6er: a case report. Respir Care 1984; 29:1009-12 4 Sottiaux 'I: GofJart At Van Der Linden ~ Roeseler J, Van Melsem A, Reynaert M. Variations of spinability and protein content of bronchial mucus during controDed ventilation. Acta Anaesth ltal 1990; 41:33-6 5 Conti G, Spunticchia G, Rocco M, Nicoli ~ CogIiati A. Mesure de la viscosite des secretions trachM-bronchiques chez les patients SODS ventilation mecanique avec filtre-humidi6cateur chaufFant (HME) on humidi6cateur rechatdfe. Presented at the 18th Congres de la Societe de Reanimation de Langue Fran9lise, Paris, November 23-26, 1989
7b the Editor: Dr Sottiaux is reluctant to use the Pall heat and moisture exchanger (HME) during long-term mechanical ventilation (MV) because of the high rate of tracheal tube occlusion observed with CHEST I 102 I 3 I SEPTEMBER. 1992