MASA syndrome

To the Editor:

We read with interest the article by Flemons and coworkers (1) regarding the access to diagnosis and treatment of patients with suspected sleep apnea hypopnea syndrome. A similar issue has been raised in Spain.

The Spanish Group of Breathing Sleep Disorders (SGBSD) has performed two previous studies (2, 3) and a more recent one (October 2001 to February 2002) aimed to assess the Spanish situation regarding the diagnosis of suspected sleep apnea hypopnea syndrome. In the last study, we contacted 233 public hospitals to complete a questionnaire set up in a Web site by the Spanish Respiratory Society (SEPAR); of these 233 public hospitals, about half performed sleep studies. A total of 63 hospitals performed limited sleep studies (level III with 4 information channels) and complete polysomnography (PSG) and 46 other centers performed only limited sleep studies. The total limited sleep studies per year were 24,259 and the total PSG per year were 17,270. The mean waiting time for the performance of diagnostic PSG was 261 ± 241 days (range, 65-918). This delay is similar to that reported by Flemons and colleagues (1).

Our number of full PSG beds per 100,000 population was similar to the UK (1) (0.29 in Spain and 0.30 in the UK) but still less than the numbers reported in Belgium (1.5), Australia (1.3), the United States (1.3) and Canada (1.4). A similar issue happens with the number of full PSG studies per 100,000 population per year: Spain 45.6; UK 42.5; Belgium 177.2; Australia 282.0; United States 427.0; and Canada 370.4. Also, as reported by Flemons and colleagues (1), we found important regional differences within our country. In addition, we have increased the number of limited sleep studies, as commented in Dr. Pack's editorial (4), to avoid expanding the waiting list. These data reinforce our awareness that the capacity for diagnosis of suspected sleep apnea is much less than the demand. Therefore, it is imperative to design new strategies, such as performing simplified studies for the diagnosis, and to increase the resources to adapt our capacity to the current requirements of our population.

Conflict of Interest Statement: J.F.M., J.M.M., and J.D. do not have a financial relationship with a commercial entity that has an interest in the subject of this letter.

JUAN F. MASA

San Pedro de Alcantara Hospital

Caceres, Spain

JOSE M. MONTSERRAT

Clinic Hospital

Barcelona, Spain

JOAQUIN DURAN

Txagorritxu Hospital

Vitoria, Spain

AND THE SPANISH GROUP OF BREATHING SLEEP DISORDERS

References

1. Flemons WW, Douglas NJ, Kuna ST, Rodenstein DO, Wheatley J. Access to diagnosis and treatment of patients with suspected sleep apnea. Am J Respir Crit Care Med 2004; 169:668-672.

2. Duran Cantolla J, Amilibia Alonso J, Barbe Illa F, Capole Gil F, Gonzalez Mangado N, Jimenez Gomez A, Marin Trigo JM, Masa Jimenez JF, Montserrat Canal JM, Teran Santos J. Grupo de Trabajo de Area de Insuficiencia Respiratoria y Trastornos del Sueno: disponibilidad de recursos tecnicos para el diagnostico y tratamiento del sindrome de apnea obstructive del sueno en los hospitales de la red publica del estado. Arch Bronconeumol 1995;31:463-469.

3. Teran Santos J, Fernandez Garcia C, Cordero Guevara J. Situation en Espana de los recursos diagnosticos y de los tratamientos con presion positiva continua sobre la via aerea, en el sindrome de apneas-hipopneas obstructivas del sueno. Arch Bronconeumol 2000;36:494-499.

4. Pack AI. Sleep-disordered breathing: access is the issue. Am J Respir Crit Care Med 2004;169:666-667.

From the Authors:

The letter of Dr. Masa and colleagues adds further support, from the vantage point of current practice in Spain, to the conclusions drawn from the report of Flemons and colleagues (1) and the accompanying editorial (2). They confirm the discrepancy between the demand for sleep diagnostic services in Spain and the current capacity to deliver them. There is little doubt that this discrepancy is a major contributing factor as to why physicians in Spain, and other countries, are making widespread use of ambulatory approaches to diagnosis. The experience of the Spanish group, together with that of physicians in other countries, argues that ambulatory studies are likely to be a viable and reasonable approach to diagnosis of this common disorder. This raises the question as to why they are not recommended (3). As outlined in the editorial (2), the issue is likely not the technology per se, but rather the state of evidence. The evidence-based review (4) on which recommendations on ambulatory diagnostic approaches are based (3) addressed the ability to rule out or rule in sleep apnea on the basis of an arbitrary threshold of apnea-hypopnea index (AHI) greater than 15 episodes (3). This question was driven by the approaches used in the published literature (for reviews, see [4]). It is not the most appropriate question. Differences between results of an ambulatory study at home and an in-laboratory full-sleep study on another night can arise from at least three sources: (1) night-to-night variability in AHI (5, 6); (2) differences in sleep-for example, amount of REM sleep-between in-laboratory and at home; and (3) differences between estimates of AHI by different technologic approaches. Assuming, therefore, that any differences between diagnostic approaches are simply the result of technologic differences is incorrect and leads to a biased and negative view of the validity of ambulatory approaches. We will only make progress in this area if studies address the relative magnitude of these different sources of variance. Moreover, we need to move away from evaluations of diagnostic accuracy based on an arbitrary threshold of unproven clinical significance for a variable measure-that is, AHI (5, 6)-and toward evaluations based on clinical outcomes. We need to urge our professional societies to impanel a working group to address the issues raised in the evidence-based review (4), recommendations (3), and editorial (2) so that the role of ambulatory approaches to diagnosis can be more reasonably assessed.

Conflict of Interest Statement: A.I.P. has a grant from ResMed, Inc. to study the relative role of ambulatory recording of sleep-disordered breathing as it compares to full sleep study; he also receives royalties from Marcel Dekker Publishers for a book he edited entitled Sleep Apnea: Pathogenesis, Diagnosis, and Treatment; and he has a patent pending related to the use of serotonin agonists to treat sleep apnea in mammals. W.W.F. does not have a financial relationship with a commercial entity that has an interest in the subject of this letter.

ALLAN I. PACK

University of Pennsylvania

Philadelphia, Pennsylvania

W. WARD FLEMONS

University of Calgary

Calgary, Alberta, Canada

References

1. Flemons WW, Douglas NJ, Kuna ST, Rodenstein DO, Wheatley J. Access to diagnosis and treatment of patients with suspected sleep apnea. Am J Respir Cri t Care Med 2004;169:668-672.

2. Pack AI. Sleep-disordered breathing: access is the issue. Am J Respir Crit Care Med 2004;169:666-667.

3. Chesson AL, Berry RB, Pack A. Practice parameters for the use of portable monitoring devices in the investigation of suspected obstructive sleep apnea in adults. Sleep 2003;26:907-913.

4. Flemons WW, Littner MR, Rowley JA, Gay P, Anderson WM, Hudgel DW, McEvoy RD, Loube DI. Home diagnosis of sleep apnea: a systematic review of the literature. Chest 2003;124:1543-1579.

5. Bliwise DL, Carey E, Dement WC. Nightly variation in sleep-related respiratory disturbance in older adults. Exp Aging Res 1983;9:77-81.

6. Wittig RM, Romaker A, Zorick FJ, Roehrs TA, Conway WA, Roth T. Night-to-night consistency of apneas during sleep. Am Rev Respir Dis 1984;129:244-246.

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