Longitudinal Home Sleep Testing Suggests a Patient's Therapy Was Not Sufficient for Severe OSA

Multi-night home sleep testing showed that a patient with severe sleep apnea was not sufficiently treated by hypoglossal nerve stimulation (HGNS).

Background

We present a 47-year-old male with a BMI of 29.7 and a history of obstructive sleep apnea. The patient was previously diagnosed with severe obstructive sleep apnea (AHI: 54) and was initially placed on CPAP. After failing to adhere to CPAP due to comfort issues, the patient was prescribed HGNS as an alternative therapy. HGNS is a device that stimulates the hypoglossal nerve in the neck, which helps maintain tone of the tongue and upper airways during sleep. This helps reduce airway obstruction.

The patient’s HGNS stimulation setting was titrated to the maximum setting. The patient returned to his HGNS care team multiple times as he felt the device was not working due to continued symptoms consistent with severe obstructive sleep apnea. Symptoms included excessive daytime sleepiness with an inability to stay awake while driving, continued breathing obstructions, severe cognitive issues, and hypertension.

His HGNS care team recommended that he see a specialist to investigate if hyoid suspension surgery would be complementary to his HGNS therapy. Hyoid suspension was deemed unlikely to be effective for improving his sleep apnea. The patient was then referred to a specialist for Maxillomandibular Advancement (MMA) Surgery, which was assessed to be a better option. The patient used Wesper home sleep testing to better understand the severity of his breathing while using HGNS and to provide data for the MMA specialist.

Explanation of metrics:

• Breathing events: Moments of increased respiratory effort, which include reduced airflow and prolonged breathing stoppages.
• Snoring %: Percentage of snoring detected for the duration of the test
• Total sleep time: Total accumulation of sleep in minutes.
• Sleep quality score: Takes into consideration both sleep duration and sleep efficiency.
• Awakenings: The total number of awakenings during the testing period.
• Apnea/Hypopnea Index (AHI): the combined average number of apneas and hypopneas that occur per hour of sleep
• Respiratory Event Index (REI): the number of apneas and hypopneas per hour of recording time
• Oxygen Desaturation Index (ODI): the number of times per hour of sleep that the blood oxygen level drops by ≥ 3% from baseline
• Mean SPO2: The average blood oxygen saturation score
• Minimum SPO2: The lowest blood oxygen saturation score

The patient has completed 10 tests while using his HGNS device over a one-month period.

Findings

The patient’s original diagnostic test calculated an AHI of 54. With the use of HGNS at its maximum setting, the patient’s average number of breathing events per hour across 10 Wesper tests was 29 (min/max: 15/42). While breathing events are not a 1:1 ratio to AHI, breathing event severity correlates with AHI severity in clinical settings, when measured against PSG. This means that if the patient’s breathing event severity was considered moderate (15-30 events per hour) to severe (>30 events per hour), we would expect to see the patient’s AHI fall within that severity range.

Since the patient’s average breathing event score was 29 and 50% of his Wesper tests placed his breathing events in the severe range, we would expect his AHI to fall within the moderate to severe range with additional diagnostic testing.

In addition to the patient’s breathing, we also tested sleep metrics to assess how his OSA was affecting sleep quality.

The patient’s average total sleep time was 6.6 hours (low)

The patient’s average sleep quality score was 57.3% (low)

The patient’s average prolonged nighttime awakenings was 6 (high)

The patient’s Wesper test results suggested that his HGNS device was only offering moderate improvements, as indicated by continued poor breathing quality and reduced overall sleep quality. The data pointed to a need for additional therapy, such as possible MMA surgery, to treat the patient's severe OSA if CPAP was not an option.

Conclusion

Longitudinal Wesper testing was consistent with the patient’s concern that his HGNS therapy was not sufficiently treating his severe OSA. The patient’s Wesper data was shared with his MMA specialists. The patient has been cleared for MMA surgery, and the patient will be retesting with Wesper after surgical recovery. This case illustrates the value of confirming treatment response with objective, multi-night testing and monitoring the patient over the long term, so that insufficient therapy can be addressed in a reasonable timeframe.

Update (February 2023)

In February 2023, approximately 7 months after the patient initially started using Wesper, he was referred to a new sleep specialist for a new PSG to confirm that his sleep apnea was still poor while using HGNS. The new PSG was ordered specifically because

1. Wesper data showed a high level of breathing events while the patient used HGNS at its highest setting.
2. Before MMA surgery is considered, a new titration study for his HGNS device must be conducted.
   

The patient shared his new PSG results with Wesper to compare with his Wesper tests. The pre-titration PSG indicated that with HGNS, the patient had an AHI of 26.8 and a sleep efficiency of 41%. SPO2 was not provided.

Additionally, the patient upgraded from Wesper’s 2-component test to the 3-component test during the same time period and ran two Wesper tests with the pulse oximeter. The two 3-component tests showed that his sleep apnea was still within the moderate to severe range despite using HGNS.

His average AHI between the two tests was 27.55 with the highest recorded AHI at 37.3. The average ODI was 42.3 with the highest recorded ODI at 62.4. The average mean SPO2 was 92.5% with the lowest recorded mean SPO2 at 91%. The average minimum SPO2 was 73% with the lowest recorded minimum SPO2 at 72%. The Wesper tests were consistent with the results of the patient’s overnight PSG.

Wesper also showed that his sleep apnea severity was largely dependent on sleeping position, with an average supine AHI of 37.8 (Max 50.7). Side sleeping, however, resulted in an average AHI of 9.68, suggesting that he may be a candidate for positional therapy in combination with his HGNS device. However, on consultation, the patient revealed he’s intolerant to positional therapy as it causes him pain issues.

The patient is currently awaiting a second sleep study in April 2023 for additional titration of his HGNS device. If additional titration is unsuccessful, the patient will be considered for MMA surgery. The patient plans on continuing to test with Wesper to collect more data.