Predictors of response to a nasal expiratory resistor device and its potential mechanisms of action for treatment of obstructive sleep apnea

Abstract

Study objective: A one-way nasal resistor has recently been shown to reduce sleep disordered breathing (SDB) in a subset of patients with Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS). The purpose of this study was to examine characteristics predictive of therapeutic response to the device and provide pilot data as to its potential mechanisms of action. PATIENTS, INTERVENTIONS, AND MEASUREMENTS: 20 subjects (15M/5F, age 54 ± 12 years, BMI 33.5 ± 5.6 kg/m²) with OSAHS underwent 3 nocturnal polysomnograms (NPSG) including diagnostic, therapeutic (with a Provent® nasal valve device), and CPAP. Additional measurements included intranasal pressures and PCO₂, closing pressures (Pcrit), and awake lung volumes in different body positions.

Results: In 19/20 patients who slept with the device, RDI was significantly reduced with the nasal valve device compared to the diagnostic NPSG (27 ± 29/h vs 49 ± 28/h), with 50% of patients having an acceptable therapeutic response. Among demographic, lung volume, or diagnostic NPSG measures or markers of collapsibility, no significant predictors of therapeutic response were found. There was a suggestion that patients with position-dependent SDB (supine RDI > lateral RDI) were more likely to have an acceptable therapeutic response to the device. Successful elimination of SDB was associated with generation and maintenance of an elevated end expiratory pressure. No single definitive mechanism of action was elucidated.

Conclusions: The present study shows that the nasal valve device can alter SDB across the full spectrum of SDB severity. There was a suggestion that subjects with positional or milder SDB in the lateral position were those most likely to respond.

Keywords: Expiratory positive airway pressure; nasal valve; obstructive sleep apnea; sleep apnea therapy.

Figure 1

15-second window showing airflow and pressure tracings recorded during the NPSG with the nasal valve device in place, demonstrating increased pressure during expiration with no pressure during inspiration

Figure 2

When comparing the group with therapeutically acceptable response to the non-responders, the lateral RDI at baseline tended to be lower (6 ± 19.4/h vs 59.8 ± 43.9/h, p = NS), while the ratio of supine to lateral RDI at baseline tended to be higher (2.8 ± 2.3 vs 1.2 ± 0.2), suggesting that positional variability of RDI may be predictive of the response to NEPAP

Figure 3

Awake lung volumes (FRC) obtained without nEPAP; data shown are the FRC in sitting supine and lateral positions In this figure subjects are grouped by response to the nasal valve device (therapeutic, partial, and no response).

Figure 4

Lowest effective expiratory pressure (LEP) which was sufficient in ameliorating SDB throughout the entire night against therapeutic CPAP Each point represents data from one subject.

Figure 5

Two-min periods during sleep with the nasal valve device in one patient Figure 5A shows maintenance of 17 cm H₂O of end-expiratory pressure without evidence of sleep disordered breathing. Figure 5B shows evidence of sleep disordered breathing events during a period of lower end expiratory pressures.

Figure 6

Repeat episodes of mouth breathing (arrowhead▲) resulting in immediate loss of intranasal pressure (arrow↓) Mouth closure results in reestablishment of therapeutic intranasal pressures.

Figure 7

Period of regular arousals which appear to be related to rapid increases in intranasal pressure (up to 22 cm H₂O) without evidence of sleep disordered breathing Patient with therapeutic nEPAP pressure of 8 cm H₂O elsewhere during the study.

Figure 8

Arousal resulting in mouth opening and loss of therapeutically acceptable intranasal pressure (20 cm H₂O) Therapeutic pressure is reestablished after gradual “pumping up” of intranasal pressure.

Figure 9

Time series of lung volumes obtained in one subject from MRIs using a gradient echo sequence that was developed for real-time imaging of the lung at a frequency of 10 images per second Subjects breathed quietly with normal tidal breaths through the nose and through mouth with (A) and without (B) the nasal valve device in place. Figure 9A shows breathing with the device in place (nasal respiration with device vs oral respiration bypassing device). Figure 9B shows period of breathing without the device (nasal vs. oral respiration).