Advanced Positive Airway Pressure Therapies for Sleep-Disordered Breathing

LEARNING OBJECTIVES

On completion of this chapter, the reader should be able to:

1. Understand the fundamentals of advanced positive airway pressure devices used in the sleep center setting: adaptive servo-ventilation, spontaneous timed, and volume-assured pressure support.
2. Recognize the indications and limitations of these therapy modes.
3. Understand the operation and algorithm for the titration of both ResMed and Philips Respironics model devices.

INDICATIONS FOR ADVANCED POSITIVE AIRWAY PRESSURE THERAPY MODES

Positive airway pressure (PAP) technology has advanced drastically since continuous positive airway pressure (CPAP) was first offered as a treatment for sleep-disordered breathing (SDB) in 1983 (1, 2). One of the many reasons for these advancements is the increase in the understanding of SDB. Conditions that were once frustrating and baffling to both sleep technologists and physicians are now treatable by specific PAP therapy modes utilizing advancements in technology and algorithms (2). This chapter focuses on advanced PAP therapy modes applicable to a typical sleep disorders center: adaptive servo-ventilation (ASV), volume-assured pressure support (VAPS), and spontaneous timed (ST). This chapter will cover the indications for their use and the specific devices used in the sleep disorders center at the time of this writing. The two manufacturers of these advanced PAP devices, ResMed and Philips Respironics, each offer training and documentation with every major release in technology; however, the mode types and principles of their instructions have been consistent since their development. The technologist must have a clear understanding of each modality and their indications to properly perform testing using these therapies.

ASV for Central Sleep Apnea Syndrome

ASV is a PAP therapy mode specifically intended for central sleep apnea syndrome (CSAS) (3). The International Classification of Sleep Disorders (ICSD) 3 identifies eight different forms of central sleep apnea (CSA): Central Sleep Apnea with Cheyne-Stokes Breathing, Central Apnea Due to Medical Disorder without Cheyne-Stokes Breathing, Central Sleep Apnea Due to High-Altitude Periodic Breathing, Central Sleep Apnea Due to Medication or Substance, Primary Central Sleep Apnea, Primary Sleep Apnea of Infancy, Primary Sleep Apnea of Prematurity, and Treatment-Emergent Central Sleep Apnea (4). CSAS is described thoroughly in Chapter 13. ASV was first introduced by ResMed and was first validated as a treatment for CSAS with Cheyne-Stokes breathing in 2001 (5). Philips Respironics soon produced their own version (2, 6). By 2012, ASV was an American Academy of Sleep Medicine (AASM)-recommended treatment option (7). Before the availability of ASV, treatment of CSAS was especially difficult. CPAP, bilevel positive airway pressure (BPAP), BPAP ST, and oxygen therapy were long-standing treatment options for CSAS with varying levels of success (2, 8). The primary function of ASV is to respond to irregular ventilation caused by CSA to maintain proper respiration. ASV is indicated only for CSA (2, 3, 5, 6, 7).

VAPS for Hypoventilation Syndromes

VAPS is a type of PAP therapy that is applicable to patients diagnosed with hypoventilation disorders (9, 10). Sleep-related hypoventilation disorders include Obesity Hypoventilation Syndrome, Congenital Alveolar Hypoventilation Syndrome, Late-Onset Central Hypoventilation with Hypothalamic Dysfunction, Idiopathic Central Alveolar Hypoventilation, Sleep-Related Hypoventilation Due to a medication or Substance, and Sleep-Related Hypoventilation Due to a Medical Disorder (4). Therefore, indication for VAPS in the sleep center setting may include patients with diagnosed chronic hypoventilation syndromes such as neuromuscular/restrictive disorders, chronic obstructive pulmonary disorder, or obesity hypoventilation. There is a full explanation of obesity hypoventilation syndromes in Chapter 14. Although there are many similar terms and setting descriptions between ASV and VAPS, the two modalities are not interchangeable (10, 11). VAPS uses variable pressure support to achieve a target tidal volume (Vt), in contrast to ASV that performs a quick constant breath-by-breath response and does not augment the patient’s Vt consistently (10, 11). VAPS is an AASM-recommended option for chronic hypoventilation patients receiving PAP therapy adjustment in the sleep center (12).

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