EPAP-Emergent Central Sleep Apnea Notes

EPAP-Emergent Central Sleep Apnea: Insights from a Novel “Clip-on” Pressure Transducer Flow Cannula

Overview

  • Nasal Expiratory Positive Airway Pressure (EPAP) therapy as an alternative to Continuous Positive Airway Pressure (CPAP) for managing Obstructive Sleep Apnea (OSA).
  • Established OSA interventions (CPAP, mandibular advancement devices, tracheostomy, hypoglossal nerve stimulation) can induce or unmask Central Sleep Apnea (CSA).
  • A review found one case of EPAP-emergent CSA with the discontinued Provent nasal EPAP device.
  • Current FDA-cleared EPAP devices (Bongo Rx and ULTepap) have no reported TECSA cases in literature.
  • Historically low TECSA detection rates possibly due to technical limits in measuring flow during nasal EPAP therapy.
  • This report presents a case of ULTepap-emergent CSA, confirmed using a novel "clip-on" pressure transducer flow cannula for quantitative nasal airflow measurement.

Introduction

  • Nasal Expiratory Positive Airway Pressure (EPAP) therapy is an alternative for managing Obstructive Sleep Apnea (OSA).
  • Mahadevia and Lopata's research showed EPAP's effectiveness in reducing apnea index and improving nocturnal oxygenation.
  • Several EPAP devices (Provent, Bongo Rx, and ULTepap) have been developed and FDA-cleared to treat OSA.
  • Treatment-emergent central sleep apnea (TECSA) is a potential adverse outcome of OSA therapies.
  • A literature review found one documented case of TECSA linked to the discontinued nasal Provent EPAP device.
  • Current FDA-cleared EPAP technologies, like Bongo Rx and ULTepap, have no reported TECSA incidents in scientific literature.
  • This report presents a case of ULTepap-emergent CSA, diagnosed using a novel “clip-on” pressure transducer flow cannula for quantitative measurement of nasal airflow.

Case Report

  • A 76-year-old male veteran with cardiovascular and respiratory comorbidities, including heart failure with preserved ejection fraction (HFpEF), post coronary artery bypass graft, mild chronic obstructive pulmonary disease, and moderate OSA, was referred for sleep apnea management.
  • The patient was previously treated with continuous positive airway pressure (CPAP) and bilevel PAP with poor response.
  • Reassessment with PAP titration showed severe CSA with Cheyne-Stokes breathing and a SpO2 "banding pattern."
  • CPAP download showed poor compliance, with an average use of 2 hours and a residual apnea-hypopnea index (AHI) of 11 events/h at CPAP of 12 cmH_2O.
  • Due to poor CPAP compliance, Bongo Rx was attempted without success.
  • ULTepap was subsequently prescribed, and the patient was able to use it for 4 hours at night.
  • A split night study was performed using ULTepap and a novel “clip-on” pressure transducer flow cannula.
  • The diagnostic portion revealed severe OSA (AHI 46 events/h) with primarily obstructive hypopneas.
  • The therapeutic portion with ULTepap demonstrated TECSA with crescendo-decrescendo breathing pattern and an AHI of 62 events/h

Discussion

  • Multiple OSA interventions, including CPAP, mandibular advancement devices (MAD), tracheostomy, and hypoglossal nerve stimulation (HNS), can induce or unmask CSA.
  • The reported prevalence of treatment-emergent central sleep apnea (TECSA) varies across therapies: 5.0% to 20.3% in CPAP therapy, 3.3% in HNS, and 1.8% in maxillofacial surgery.
  • While no cohort studies have established the TECSA prevalence in MAD, existing case reports support its occurrence.
  • The pathophysiology behind TECSA primarily involves ventilatory instability, altered chemosensitivity to PaCO_2, and low arousal threshold of newly treated OSA.
  • CPAP can potentially increase lung volume and activate lung stretch receptors, but it remains uncertain whether EPAP can produce similar effects.
  • Some patients may suffer from comorbidities associated with high loop gain, as seen in this patient who has a history of HFpEF.
  • The prevalence of TECSA associated with nasal EPAP therapy remains poorly characterized.
  • The historically low detection rate of TECSA may be attributed to technical limitations in accurately measuring flow during nasal EPAP administration.
  • Conventional diagnostic modalities, such as in-lab polysomnography (PSG) and type 3 flow-based home sleep apnea testing (HSAT), are constrained in their ability to assess airflow in the presence of nasal EPAP due to the incompatibility of standard nasal flow sensors with EPAP devices.
  • Alternative non-flow-based sleep technologies, including WatchPAT, novel photoplethysmography (PPG)-based and non-PPG-based OSA-detecting wearables, as well as pulse oximeters, can be utilized to evaluate EPAP efficacy, but these technologies may lack sufficient reliability in detecting CSA.
  • In this case, a novel ULTepap-compatible “clip-on” pressure transducer airflow catheter was used to obtain flow signals during in-lab PSG, enabling the identification of TECSA during therapeutic efficacy assessment.
  • This case may represent the first documented instance of TECSA developed during two distinct OSA therapeutic modalities, detected several months apart after the initiation of each treatment.
  • While TECSA typically resolves within a few months following the commencement of therapy, this was not observed in the patient, suggesting that the development of TECSA may not be contingent upon the specific therapeutic intervention employed but may, instead, be linked to elevated loop gain secondary to the underlying pathophysiology of HFpEF.
  • In summary, this report documents the first instance of TECSA associated with ULTepap, confirmed through quantitative flow measurements obtained using an innovative cannula specifically engineered for ULTepap application.
  • The development and availability of this novel catheter represents a welcomed advancement for patients undergoing ULTepap nasal EPAP therapy, enabling efficacy assessments and facilitating longitudinal follow-up of TECSA.

Abbreviations

  • AHI: Apnea-Hypopnea Index
  • CPAP: Continuous Positive Airway Pressure
  • CSA: Central Sleep Apnea
  • EPAP: Expiratory Positive Airway Pressure
  • HFpEF: Heart Failure with Preserved Ejection Fraction
  • HSAT: Home Sleep Apnea Testing
  • OSA: Obstructive Sleep Apnea
  • PSG: Polysomnography
  • TECSA: Treatment-Emergent Central Sleep Apnea

Figure Captions

  • Figure 1: Novel pressure transducer flow cannula specifically engineered for ULTepap application. (A) cannula (BRIGGS Medical, Avon, Ohio); (B) cannula clipped on ULTepap on a model.
  • Figure 2: Split night polysomnography epochs. (A) Obstructive events were observed during the baseline diagnostic portion; (B) Central sleep apneas with a crescendo-decrescendo breathing pattern emerged while patient was on ULTepap during the second half of the night. Nasal flow signal was obtained using the novel ULTepap-compatible clip-on pressure transducer airflow cannula.