Abstract
Patients with central respiratory paralysis can benefit from diaphragm pacing to restore respiratory function. However, it would be important to develop a continuous respiratory monitoring method to alert on apnea occurrence, in order to improve the efficiency and safety of the pacing system. In this study, we present a preliminary validation of an acoustic apnea detection method on healthy subjects data. Thirteen healthy participants performed one session of two 2-min recordings, including a voluntary respiratory pause. The recordings were post-processed by combining temporal and frequency detection domains, and a new method was proposed—Phonocardiogram-Derived Respiration (PDR). The detection results were compared to synchronized pneumotachograph, electrocardiogram (ECG), and abdominal strap (plethysmograph) signals. The proposed method reached an apnea detection rate of 92.3%, with 99.36% specificity, 85.27% sensitivity, and 91.49% accuracy. PDR method showed a good correlation of 0.77 with ECG-Derived Respiration (EDR). The comparison of R-R intervals and S-S intervals also indicated a good correlation of 0.89. The performance of this respiratory detection algorithm meets the minimal requirements to make it usable in a real situation. Noises from the participant by speaking or from the environment had little influence on the detection result, as well as body position. The high correlation between PDR and EDR indicates the feasibility of monitoring respiration with PDR.
Highlights
Impairment of ventilatory control may lead to a dependence on external mechanical ventilation, even though the main inspiratory effector, the diaphragm, is intact
We show that detection can be improved by combining the detection results from the temporal and frequency detection domains and Phonocardiogram-Derived Respiration (PDR)
We showed the feasibility of evaluating respiratory effort with PDR by comparing the result with ECG-Derived Respiration (EDR)
Summary
Impairment of ventilatory control (central respiratory paralysis) may lead to a dependence on external mechanical ventilation (usually with intermittent positive pressure via tracheotomy), even though the main inspiratory effector, the diaphragm, is intact. These may be due to the interruption in the transmission of the control commands (essentially post-traumatic upper cervical spinal cord injury) or abnormalities in the genesis of the control (central, congenital, or acquired alveolar hypoventilation) [1]. Implanted phrenic nerve electric stimulators for diaphragm pacing are notable exceptions to this rule They include built-in electronic dysfunction alarms but are devoid of “efficacy” alarms. An apnea (absence of flow for at least 10 s [5]) due to airway obstruction (obstructive apnea, with respiratory effort) or diaphragmatic neurotransmission failure (central apnea, without respiratory effort) will not result in an immediate alarm if the patient is not equipped with an additional flow sensor [6]
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