By Jeffrey J. Fredberg*
Professor, Harvard School of Public Health
Let me pose two questions that ought to be of interest to every reader of this magazine. The answers might surprise you. The first is this. What subject area of science or medicine is has undergone explosive growth, has accumulated peer-reviewed publications in the primary archival scientific literature that already number almost 800 and growing, has accumulated annual citations of these publications for the year 2011 alone projected to top 1000, and has cumulative citations by year-end projected to top 10,000? The graphic below is from the Web of Science and depicts the evolution of this emerging subject area broken down by year.
The answer is this: acoustic rhinometry and acoustic pharyngometry. Surprised? I was. For any subject area in general science these might be thought of as impressive numbers, but for a specialized branch of clinical medicine they are astounding. What do these numbers teach us?
They teach us, first, that these technologies must be filling an important niche, and about that niche I will say more below. Second, these numbers show us that that niche is evolving in a fashion that can only be called dynamic. And finally, we have to remember that these numbers refer to publications in the scientific literature. As such, they are telling us that there is still a great deal that we do not yet know about how these technologies inform diagnostics, treatment, community medicine and private practice, for once all these questions are finally answered there would be nothing left to publish. Fields in which all the questions are already answered are scientifically moribund, after all. For acoustic rhinometry and acoustic pharyngometry, this is most certainly not the case. Together, they comprise an ongoing and evolving success story that is built on a foundation of continuing research efforts.
This brings me to my second question, which relates to the niche that these technologies help to fill. The question is this. What does undiagnosed obstructive sleep apnea (OSA) have to do with cardiovascular disease? The answer is: quite a lot. By some metrics the prevalence of OSA in males and females approaches 24% and 9%, respectively, whereas only one in five subjects with an elevated apnea-hypopnea index (AHI) complains of daytime sleepiness. Yet OSA is known to trigger increased sympathetic activity, systemic inflammation, oxidative stress, and endothelial dysfunction, and is known to be linked tightly to hypertension, stroke and death. In those OSA patients with hypertension, treatment using continuous positive airway pressure (CPAP) reduces hypertension, while the 18 year mortality follow up on the Wisconsin Sleep Cohort shows that untreated subjects with elevated baseline AHI are at increased risk of cardiovascular mortality irrespective of daytime sleepiness.
Taken together, these findings show that undiagnosed /untreated OSA comprises a public health problem of major proportions, and even impacts pediatric populations. Acoustic rhinometry and acoustic pharyngometry are certainly not going to provide all the answers, but they comprise arrows in our quiver. In a variety of clinical settings they are increasingly being found to be a useful part of our armamentarium for determining diagnosis and guiding treatment. Their dynamic record of scientific citations attests to the fact that we are continuing to discover how to use these tools in better and more effective ways in order to help address a major public health problem.
*The author holds the US patents on acoustic rhinometry and pharyngometry. His current research focuses on the basic science of asthma and other lung diseases.
