Use of a Transformed ECG Signal to Detect Respiratory Effort During Apnea

Abstract

Study Objectives: To evaluate the ability of a transformed electrocardiography (ECG) signal recorded using standard electrode placement to detect inspiratory bursts from underlying surface chest wall electromyography (EMG) activity and the utility of the transformed signal for apnea classification compared to uncalibrated respiratory inductance plethysmography (RIP). Methods: Part 1: 250 consecutive adult studies without regard to respiratory events were retrospectively reviewed. The ECG signal was transformed with high pass filtering and viewed with increased sensitivity and channel clipping to determine the fraction of studies with inspiratory burst visualization as compared to chest wall EMG (right thorax). Part 2: 445 consecutive studies were reviewed to select 40 with ≥ 10 obstructive and ≥ 10 mixed or central apneas (clinical scoring). Five obstructive and 5 central or mixed apneas were randomly selected from each study. A blinded scorer classified the apneas using either RIP or a transformed ECG signal using high pass filtering and QRS blanking. The agreement between the two classifications was determined by kappa analysis. Results: Part 1: Inspiratory burst visualization was noted in the transformed ECG signals and chest wall EMG signals in 83% and 71% of the studies (P < .001). Part 2: The percentage agreement between RIP and transformed ECG signal classification was 88.5%, the kappa statistic was 0.81 (95% CI 0.76 to 0.86) and interclass correlation was 0.84, showing good agreement. Conclusions: A transformed ECG signal can exhibit inspiratory bursts in a high proportion of patients and is potentially useful for detecting respiratory effort and apnea classification.

Assessment of respiratory effort with EMG extracted from ECG recordings during prolonged breath holds: Insights into obstructive apnea and extreme physiology

“…The struggle phase is different, as the voluntary suppression of respiratory motor behavior is won over by powerful involuntary contractions of the respiratory muscles. The increase in EMG amplitude as the struggle phase progresses bears a striking resemblance to what has been observed in obstructive apnea under various conditions, including obstructive sleep apnea (Berry et al, ,,2016, 2019), obstructive apnea associated with epileptic seizure activity in people (Lacuey et al, 2018; Sivathamboo et al, 2020) and in experimental animals (Irizarry et al, 2020; Jefferys et al, 2019; Nakase et al, 2016). This close resemblance is the reason that we suggest that the struggle phase of a prolonged breath hold can be used as a model for obstructive apnea found during sleep or in association with epileptic seizures conditions where the periods of obstructive apnea are unpredictable and where their durations can be much shorter (sleep) or life threatening (epilepsy).…”

“…The struggle phase is different, as the voluntary suppression of respiratory motor behavior is won over by powerful involuntary contractions of the respiratory muscles. The increase in EMG amplitude as the struggle phase progresses bears a striking resemblance to what has been observed in obstructive apnea under various conditions, including obstructive sleep apnea (Berry et al, ,,2016(Berry et al, ,, , 2019, obstructive F I G U R E 4 Cardiac and respiratory measures during breath holds. (a) Mean RR interval (seconds) for each 60 second segment across all subjects.…”

“…The resulting filtered signal was squared as a method to full‐wave rectify the signal and enhance the signal‐to‐noise ratio, smoothed (50 sample half width), and then enveloped with a Hilbert transform (Balan et al, 2013; Benitez et al, 2001) using National Instruments LabVIEW software (2019, Austin, TX, USA). Peaks in the transform as a function of time were integrated as a magnitude measure (an alternative method is given in (Berry et al, 2019). Units for the resulting Hilbert area measure were filtered squared voltage • seconds.…”

“…The struggle phase in volitional apnea and obstructive apnea is generally defined with inductance plethysmography (e.g., (Kogan et al, 2016)), however, this technique indirectly assesses respiratory effort. Berry and colleagues demonstrated chest wall electromyographic (EMG) signals associated with the electrocardiogram (ECG) were useful in defining periods of obstructive sleep apnea (Berry et al, ,,2016, 2018, 2019). Similar EMG signals associated with periods obstructive apnea during epileptic seizure activity in patients or animal models correlated with inductance plethysmography or intratracheal pressure recordings (e.gLacuey et al, 2018; Nakase et al, 2016; Stewart et al, 2017).…”

Causes and Effects Contributing to Sudden Death in Epilepsy and the Rationale for Prevention and Intervention

“…EMG evidence of the unproductive inspiratory effort can appear in ECG and EEG records ( 1 , 45 ). This measure has been used in studies of obstructive sleep apnea ( 75 – 77 ) and can been seen in recordings from elite apneists (e.g., breath-holding divers) ( 78 ), where stertorous breathing is not a confound. Inductance plethysmography in epilepsy patients also shows the inspiratory effort ( 73 ).…”