Respiratory Inductance Plethysmography to Quantify Changes in Ventilation in Obstructive Sleep Apnea.

BACKGROUND AND

OBJECTIVE

The study aims to determine whether respiratory inductance plethysmography (RIP) signals can be used to quantify changes in ventilation and provide advanced obstructive sleep apnea (OSA) severity metrics. This approach seeks to address limitations in current airflow-based OSA measures, particularly those relying on nasal pressure, which may be compromised by oral breathing.

METHODS

Adult patients with OSA (N = 89, 68Male:21Female) completed in-laboratory polysomnography (PSG) allowing for RIP-based ventilation estimates to be compared against a gold standard oronasal-pneumotach (normalized ventilation %eupnea). Concordance was assessed on three levels: 1) individual breath ventilation, 2) individual respiratory event depth (percentage reduction in ventilation from local average), and 3) patient-specific OSA severity in terms of average event depth and ventilatory burden (average event depth x average event duration x event rate). To address overestimation of RIP ventilation during obstruction, we developed and applied a calibration and linearization method ("RIP correction"). Concordance analysis evaluated median bias for both small (<70%eupnea) and large breaths (>130%eupnea), along with bias and intraclass correlation coefficient (ICC) calculation for events and patient-specific measures.

RESULTS

For individual breaths (N = 495,631), RIP correction reduced overestimation bias for small breaths from 12 to 2%eupnea. For individual events (N = 34,497), RIP correction reduced mean bias for event depth estimates from 9 to 1%eupnea. For patient-specific analysis underestimation of average event depth was attenuated from 9 to 4%eupnea and for ventilatory burden, from 275 to 117%eupnea min/hr. Additionally, RIP correction improved ICC for event depth and patient-level traits.

CONCLUSION

RIP signals, with appropriate processing, enable quantification of advanced ventilation-based OSA metrics, addressing concerns that airflow-based measures may be affected by breathing route.