Quantitative validation of the suprasternal pressure signal to assess respiratory effort during sleep

Abstract

Objective Intra-esophageal pressure (Pes) measurement is the recommended gold
standard to quantify respiratory effort during sleep, but used to limited extent
in clinical practice due to multiple practical drawbacks. Respiratory inductance
plethysmography belts (RIP) in conjunction with oronasal airflow are the accepted
substitute in polysomnographic systems (PSG) thanks to a better usability, although
they are partial views on tidal volume and flow rather than true respiratory effort and
are often used without calibration. In their place, the pressure variations measured
non-invasively at the suprasternal notch (SSP) may provide a better measure of
effort. However, this type of sensor has been validated only for respiratory events
in the context of obstructive sleep apnea syndrome (OSA). We aim to provide an
extensive verification of the suprasternal pressure signal against RIP belts and Pes,
covering both normal breathing and respiratory events. Approach We simultaneously
acquired suprasternal (207) and esophageal pressure (20) signals along with RIP belts
during a clinical PSG of 207 participants. In each signal, we detected breaths with a
custom algorithm, and evaluated the SSP in terms of detection quality, breathing rate
estimation, and similarity of breathing patterns against RIP and Pes. Additionally,
we examined how the SSP signal may diverge from RIP and Pes in presence of
respiratory events scored by a sleep technician. Main results The SSP signal proved to
be a reliable substitute for both esophageal pressure (Pes) and respiratory inductance
plethysmography (RIP) in terms of breath detection, with sensitivity and positive
predictive value exceeding 75 %, and low error in breathing rate estimation. The
SSP was also consistent with Pes (correlation of 0.72, similarity 80.8 %) in patterns
of increasing pressure amplitude that are common in OSA. Significance This work
provides a quantitative analysis of suprasternal pressure sensors for respiratory effort
measurements.