Essentials of Polysomnography: A Training Guide and Reference for Sleep Technicians

THE FOUNDATION OF EVERY SLEEP CENTER CURRENTLY RESTS ON THE POLYSOMNOGRAM. WITHOUT THE SUCCESSFUL COLLECTION OF THESE DATA, THE clinical evaluation of patients with sleep disorders would flounder due to the lack of objective data on which to base diagnoses and guide therapeutic interventions. Essential to this foundation is the well-trained and knowledgeable polysomnographic technician. To this end, William H. Spriggs, BS, RPGST has attempted to produce a comprehensive textbook, titled Essentials of Polysomnography: A Training Guide and Reference for Sleep Technicians, directed at these important individuals on the frontlines of sleep medicine. This book provides a resource not only for polysomnographic technicians, but for all involved in the field of sleep medicine who desire an in-depth understanding of polysomnography. It is well organized, and the wealth of information is presented in a systematically outlined progression that is easy to read and understand. The book contains numerous examples of polysomnographic recordings that illustrate the topics covered in the text. The initial chapter outlines the importance of sleep on an individual and societal level and reviews the characteristics of normal sleep. Next, the author provides an overview of pathologic sleep that could also serve as an excellent introduction to general practitioners hoping to recognize sleep disorders in their patients. The next sections encompass the nuts and bolts of polysomnography: patient flow, the equipment used in polysomnographic recordings, and sensor placement. Successive chapters are devoted to the signals acquired during the polysomnogram, identification and troubleshooting of artifacts, filter settings, and sleep staging. An excellent chapter entitled “Abnormal Events” cites the scoring rules and provides many examples of important findings, eg, limb movements and apnea/hypopneas. Other chapters discuss positive airway pressure titration, electrocardiographic abnormalities, and pediatric polysomnography. Finally, there is a comprehensive self-test with annotated answers that surveys the information provided throughout the book. This last portion will be particularly useful in assisting individuals in the initial phases of a career in sleep medicine to recognize what they have learned and areas of weakness on which to focus. Though perhaps beyond the scope of the book, the technical aspects of ambulatory portable monitor recordings are not addressed, despite the growing use of portable monitor testing to evaluate patients with suspected obstructive sleep apnea. In addition to providing a thorough discussion of all the technical aspects of polysomnography, the author also emphasizes the technician's critical role as a member of the sleep center team. A chapter devoted to the “Life as a Sleep Technician” explores the importance of maintaining an environment that is conducive to patient care and safety and putting the patient at ease during what otherwise might become a stressful experience. The importance of the literal “bedside manner” can be lost when one focuses on the complex technologic requirements of polysomnography: therefore, it is commendable to see it emphasized early in the book. That being said, accurate and consistent scoring of polysomnograms is an essential feature of reliable sleep studies and, ultimately, appropriate patient care. The numerous polysomnographic examples in the book provide a comprehensive scoring atlas. Although their presentation employs the most recent nomenclature and scoring criteria recommended by the American Academy of Sleep Medicine, some of the examples may confuse readers. In particular, the important differences between the oronasal thermistor and the nasal pressure signals as surrogate markers of airflow, including the distinction between these 2 signals in the scoring rules of apneas, are not addressed. The American Academy of Sleep Medicine scoring manual specifies that an apnea requires a flat line on the oronasal thermistor signal.1 Many have criticized that controversial decision, stating that the oronasal thermistor signal only detects expiratory airflow and cannot recognize airway obstruction on inspiration. Although the reviewers agree that respiratory events with a flat nasal pressure signal but persistent fluctuations in the oronasal signal should be scored as obstructive apneas (see example on page 373), these events would be scored as hypopneas based on criteria in the American Academy of Sleep Medicine scoring manual. Also, there are large sections of the book with examples of polysomnographic epochs displayed across the top half of the page, leaving the remainder of the page blank. The resulting low amplitude of the signals makes it difficult to appreciate some of the findings. Full-page displays or examples printed in landscape format would have made it easier to appreciate the findings of interest. When electroencephalographic frequency or amplitude or the duration of the event is critical to classification, the inclusion of time and microvolt scales would have been helpful. Perhaps in part due to the inherent subjectivity that arises from scoring qualitative signals, there are examples presented in the chapters and the self-test with which the authors of this review disagree. Specifically, the examples of bruxism are not what we view as the classic images, as the bursts of electromyography are timed to inspiration and occur at a lower frequency than that associated with most chewing movements. These shortcomings aside, this textbook achieves its stated goal as a reference for the polysomnographic technician. It will serve as a useful guide to the performance of these complex physiologic recordings and complement the practical training, experience, and supervision that lead to the high-quality recordings essential for providing excellent patient care.