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Volume 14 No. 12
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Accepted Papers

Case Reports

The Value of a Well-Trained Ear: Incidental Detection of Catathrenia on Home Sleep Apnea Tests in Patients With Low Probability for Obstructive Sleep Apnea

Louis Kazaglis, MD
Fairview Health Services, Minneapolis, Minnesota; University of Minnesota, Minneapolis, Minnesota


Catathrenia is a rare sleep-related breathing disorder marked by nocturnal groaning during prolonged exhalation. Home sleep apnea tests are growing in popularity, but no prior case reports exist documenting catathrenia detected by a home sleep apnea test. We report two cases of catathrenia incidentally detected in patients with low to intermediate risk of obstructive sleep apnea, in which diagnostic polysomnography was recommended but denied by insurers. Events were automatically scored as central apneas, leading to diagnostic uncertainty. The key to identification of catathrenia in both patients was combination of audio review of events, pattern of expiratory air trapping, and mismatch between central apnea flow signal attenuation and increased sound noted on audio amplitude signal. Diagnostic polysomnography was ordered in both cases for confirmation of diagnosis, leading to increased care costs.


Kazaglis L. The value of a well-trained ear: incidental detection of catathrenia on home sleep apnea tests in patients with low probability for obstructive sleep apnea. J Clin Sleep Med. 2018;14(12):2083–2086.


A home sleep apnea test (HSAT) is one of the primary tests for sleep-related breathing disorders (SRBD) due to concerns over cost, patient convenience, and insurer policies.1 The American Academy of Sleep Medicine (AASM) recommends an HSAT over polysomnography (PSG) in situations where a patient is at high risk for moderate to severe obstructive sleep apnea (OSA) and has no other significant concerns or comorbid conditions that might affect the accuracy of an HSAT.2 Unfortunately, many insurers do not follow AASM policy, and as a result there is the potential to misclassify severity or misdiagnose SRBD.3,4 We describe two such cases where PSG tests were denied by insurers in favor of HSAT, in which catathrenia was manually detected by expert review, and characterize features of catathrenia present on HSAT.

Catathrenia, or prolonged exhalation with associated groaning, was first described by Pevernagie and colleagues in 2001 as a parasomnia.5 It is now thought to be rare SRBD, although specific prevalence estimates do not exist.68 Although catathrenia is considered a benign condition, it has been reported to carry significant social burden.7 Treatment options are burdensome and often not covered by insurance.7 Catathrenia events may be frequently mistaken for central apneas due to similar event characteristics, with prolonged lack of inspiratory airflow and minimal discernible change in effort over the duration of the events.9 Many HSAT systems employ automated event detection and scoring systems that may identify such events as central apneas. Although manual review of HSAT is considered standard of care, characterizing central events on a HSAT is often difficult because of a lack of sleep staging, ancillary signal information (ie, chin electromyography), or video recording. Romigi and colleagues have previously reported on a 15-year-old patient with catathrenia noted on cardiorespiratory polygraphy and confirmed on PSG, but there are no prior reported cases of detection in adults on HSAT.9 In this report, we describe two cases of catathrenia automatically scored as central sleep apnea on HSAT and only identified by combination of clinical suspicion and review of synchronized audio recordings. To our knowledge—and although we suspect more cases exist—these are the first reported cases of adult catathrenia detected by HSAT.


Patient characteristics and diagnostic testing information are noted in Table 1. Catathrenia events were classified under central apneas for clinical and recording purposes.

Demographic and diagnostic information.


table icon
Table 1

Demographic and diagnostic information.

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Case 1

The patient was a 52-year-old man with a history of OSA diagnosed at an outside sleep center 16 years prior (records of outside testing were destroyed) who presented because of trouble with snoring on continuous positive airway pressure (CPAP). At the time of presentation, he had no other significant medical history and was on no medications. He had no history of parasomnias. After prior diagnosis of OSA the patient underwent adenotonsillectomy and uvulopalatopharyngoplasty and was subsequently placed on CPAP at 10 cmH2O because of persistence of symptoms. At our center, the patient's presenting symptoms were CPAP intolerance, continued snoring, and episodes of nocturnal breath-holding. Because of prior OSA diagnosis and lack of high pretest probability for moderate to severe OSA, PSG was recommended. The insurer denied PSG and the decision was upheld on appeal.

The patient underwent HSAT with Noxturnal T3 device (Nox Medical, Reykjavik, Iceland), consisting of oronasal flow pressure sensors, thoracic and abdominal respiratory inductance plethysmography effort bands, body position sensor, actigraphy, audio recording, and pulse oximeter. Results were automatically annotated by Noxturnal software and were predominantly reported as central apneas. However, upon manual review of events, audio recordings revealed labored grunting expiratory noises with waxing and waning intensity, as seen on the audio channel in Figure 1 (blue bar). Additionally, the airflow signal demonstrated significant negative (expiratory) flow with decay to zero (black arrow). During the airflow decay, the thoracic and abdominal bands did not return immediately to baseline but slowly decreased until a sudden change (gray arrow). The sudden negative deflection, suspected to represent final glottic opening at the end of the event, was accompanied by a loud, brief huff. A rapid positive deflection in thorax and abdomen signals with increased positive airflow followed and was the result of the recovery breath.

Example of catathrenia detected as central apnea in case 1.

Representative example of catathrenia detected on case 1. Black arrows = persistence of negative (expiratory) flow (airflow) and air trapping after inhalation (thorax/abdomen). Gray arrows = onset of recovery inhalation (rapid positive deflections) following glottic opening (rapid negative deflection in thorax/abdomen channel).


Figure 1

Example of catathrenia detected as central apnea in case 1.

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Because of the nature of events, confirmatory PSG was performed and demonstrated presence of prolonged expiratory events associated with labored grunting, consistent with catathrenia. Of the 81 scored central apneas, 41 were unambiguously catathrenia events and in contrast to earlier reports7, all of the patient's events were noted in non-rapid eye movement sleep. There was no evidence of nocturnal seizures or other significant SRBD. The patient was reassured on the benign nature of this condition and declined further treatment.

Case 2

The patient was an 18-year-old woman with a history of obesity who presented due to reported episodes of cessation of breathing during sleep. The patient was concerned about complaints from her college roommate about nocturnal moaning episodes. She had no other significant medical history and medications consisted only of an oral contraceptive pill. There was no history of parasomnias and only sporadic reports of snoring. Because of a lack of high pretest probability for OSA, PSG was recommended. The insurer denied PSG and the decision was upheld on appeal.

The patient underwent HSAT with Noxturnal T3 device. Similar to case 1, testing revealed primarily events automatically notated as central sleep apnea by Noxturnal software. Once again, upon listening to events, labored grunting expiratory noises were noted. Because of the nature of events, confirmatory PSG was performed and confirmed the presence of prolonged expiratory events associated with labored grunting, consistent with catathrenia. Unlike case 1, all of the patient's events occurred during rapid eye movement sleep. There was no evidence of nocturnal seizures or other significant SRBD. The patient was reassured on the benign nature of this condition.


Catathrenia is considered a rare SRBD, although its exact prevalence remains difficult to estimate because of a lack of widespread knowledge of disease. There are no widely tolerated, routinely reimbursed, and effective treatment options for catathrenia, but the disease can be associated with significant social burden. As demonstrated in these two cases, catathrenia events may be automatically misclassified as central apneas on HSAT; a high burden of central apneas should raise suspicion for catathrenia. Prolonged expiratory phase of respiration alone is unlikely to identify catathrenia.10 However, catathrenia may be identified and differentiated through careful review of audio patterns in concert with timing, magnitude, and direction of airflow and respiratory effort. Although identification and differentiation is possible, it requires a high degree of clinical suspicion, multichannel respiratory signal recording with high-quality audio, and an expert reviewer.

Inappropriate shunting of patients with low to intermediate probability of OSA to HSAT may lead to misdiagnosis, additional and unnecessary care costs, and inappropriate treatment plans. In cases where catathrenia is suspected and PSG tests are not covered, limited channel or alternative sensor-based HSAT devices (eg, peripheral arterial tonometry) may not provide enough information. Multichannel HSAT devices capturing at a minimum respiratory effort, airflow, and audio recording signals should be used to reduce uncertainty. Ultimately, clinical evaluation with a board-certified sleep medicine specialist and PSG are the standards of care to establish the diagnosis of catathrenia. There is no substitute for an experienced set of ears, in the clinic or in the laboratory.


The author reports no conflicts of interest.



American Academy of Sleep Medicine


continuous positive airway pressure


home sleep apnea test


obstructive sleep apnea




sleep-related breathing disorder



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