Hypopnea definitions, determinants and dilemmas: a focused review

Abstract Obstructive sleep apnea (OSA) is defined by the presence of repetitive obstructive apneas and hypopneas during sleep. While apneas are clearly defined as cessation of flow, controversy has plagued the many definitions of hypopneas, which have used variable criteria for reductions in flow, with or without the presence of electroencephalographic (EEG) arousal, and with varying degrees of oxygen desaturation. While the prevalence of OSA is estimated to vary using the different definitions of hypopneas, the impact of these variable definitions on clinical outcomes is not clear. This focused review examines the controversies and limitations surrounding the different definitions of hypopnea, evaluates the impact of hypopneas and different hypopnea definitions on clinical outcomes, identifies gaps in research surrounding hypopneas, and makes suggestions for future research.https://deepblue.lib.umich.edu/bitstream/2027.42/144503/1/41606_2018_Article_23.pd

The Veterans Administration and Department of Defense clinical practice guidelines for the diagnosis and management of sleep disorders: what does this mean for the practice of sleep medicine?

In 2017 the Veterans Administration (VA) and Department of Defense (DOD) launched development of clinical practice guidelines (CPGs) for the diagnosis and treatment of sleep disorders, with the goal of informing and improving patient care. The guideline development process followed GRADE methodology, considering studies and systematic reviews published over the 10-year period prior to guideline development. A total of 41 recommendations were made,18 related to the diagnosis and treatment of obstructive sleep apnea (OSA) and 23 regarding chronic insomnia disorder. In contrast to other published guidelines, the VA DoD CPGs provide a comprehensive approach to diagnosis and management of the two most common sleep disorders, including a discussion of the sequencing of diagnostic approaches and treatment options. Regarding OSA, strong recommendations were made for follow-up evaluation after non-diagnostic home sleep apnea tests, positive airway pressure therapy as first-line treatment, and the incorporation of supportive, educational and behavioral interventions for patients at high risk for PAP therapy non-adherence due to comorbid conditions. Strong recommendations were also made for the use of cognitive-behavioral therapy for insomnia and against the use of kava (an herbal supplement) in the treatment of chronic insomnia disorder. These guidelines, while intended to directly inform care within VA and DOD, are broadly relevant to the practice of sleep medicine. The majority of scientific evidence was based on studies of non-military, non-veteran populations. The CPG is a major milestone for the VA and DOD in recognizing the importance of evidence-based treatments for sleep disorders in military personnel and veterans

Increased Propensity for Central Apnea in Patients with Obstructive Sleep Apnea: Effect of Nasal Continuous Positive Airway Pressure

Rationale: There is increasing evidence of increased ventilatory instability in patients with obstructive sleep apnea (OSA), but previous investigations have not studied whether the hypocapnic apneic threshold is altered in this group

Prevalence of central sleep apnea among veterans and response rate to continuous positive airway pressure therapy.

STUDY OBJECTIVES: Sleep-disordered breathing (SDB) is common in the Veteran population. In this retrospective study, we investigated the prevalence of comorbid central and obstructive SDB and the response rate to PAP among Veterans. METHODS: Veterans were screened from a single VA medical center who had polysomnography (PSG) study from 2017 to 2021 to ascertain the presence, severity, and type of SDB by measuring the apnea-hypopnea index (AHI) and central apnea index (CAI). Patients were excluded if they did not have complete studies (diagnostic and PAP titration studies). The inclusion criteria for these analyses were central sleep apnea (CSA) defined as AHI ≥ 10 events/hour and CAI ≥ 5 events/hour. Diagnostic CSA only was defined as AHI ≥ 10 events/hour and CAI ≥ 50% of AHI. OSA only was defined if AHI ≥ 10 events/hour and CAI < 5 events/hour. Comorbid central and obstructive sleep apnea (COSA) was defined if AHI ≥ 10 events/hour and CAI > 5 events/hour but < 50% of AHI. The responsiveness to PAP therapy was determined based on the CAI < 5 events/hour on the titration study. RESULTS: A total of 90 patients met the inclusion criteria and from those 64 Veterans were found to have COSA (71%), 18 (20%) were CSA only, and 8 (9%) were OSA only. A total of 22 (24.4%) Veterans diagnosed with CSA or COSA were responsive to PAP therapy. Sixty days after treatment initiation, both responsive and nonresponsive groups had significant decreases in AHI and CAI (p < 0.05). CONCLUSIONS: Comorbid central and obstructive SDB is common among Veterans. The response to PAP therapy is suboptimal but improves over time

Tetraplegia is associated with increased hypoxic ventilatory response during nonrapid eye movement sleep

Abstract People with cervical spinal cord injury (SCI) are likely to experience chronic intermittent hypoxia while sleeping. The physiological effects of intermittent hypoxia on the respiratory system during spontaneous sleep in individuals with chronic cervical SCI are unknown. We hypothesized that individuals with cervical SCI would demonstrate higher short‐ and long‐term ventilatory responses to acute intermittent hypoxia (AIH) exposure than individuals with thoracic SCI during sleep. Twenty participants (10 with cervical SCI [9 male] and 10 with thoracic SCI [6 male]) underwent an AIH and sham protocol during sleep. During the AIH protocol, each participant experienced 15 episodes of isocapnic hypoxia using mixed gases of 100% nitrogen (N2) and 40% carbon dioxide (CO2) to achieve an oxygen saturation of less than 90%. This was followed by two breaths of 100% oxygen (O2). Measurements were collected before, during, and 40 min after the AIH protocol to obtain ventilatory data. During the sham protocol, participants breathed room air for the same amount of time that elapsed during the AIH protocol and at approximately the same time of night. Hypoxic ventilatory response (HVR) during the AIH protocol was significantly higher in participants with cervical SCI than those with thoracic SCI. There was no significant difference in minute ventilation (V.E.), tidal volume (V.T.), or respiratory frequency (f) during the recovery period after AIH in cervical SCI compared to thoracic SCI groups. Individuals with cervical SCI demonstrated a significant short‐term increase in HVR compared to thoracic SCI. However, there was no evidence of ventilatory long‐term facilitation following AIH in either group