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Mechanisms of ventilatory periodicities
1Department of Medicine, University of Pennsylvania Medical Center, Philadelphia.
Annals of Biomedical Engineering
|September 1, 1993
Summary
Periodic breathing, linked to obstructive sleep apnea, arises from chemical instability in respiratory control or sleep state changes. These factors can interact, causing complex breathing oscillations during sleep.
Area of Science:
- Respiratory Physiology
- Sleep Medicine
- Control Systems Engineering
Background:
- Obstructive sleep apnea (OSA) is frequently associated with abnormal breathing patterns during sleep.
- Ventilatory periodicities, or oscillations in breathing, are observed in conditions like OSA, hypoxia, and heart failure.
- Understanding the mechanisms of periodic breathing is crucial for managing sleep-disordered breathing.
Purpose of the Study:
- To investigate the underlying causes of ventilatory periodicities, particularly in relation to obstructive sleep apnea.
- To differentiate between chemical and state instability as drivers of periodic breathing.
- To explore the interaction between chemical and state instability in generating complex ventilation patterns.
Main Methods:
- Analysis of ventilatory control systems, focusing on feedback loop dynamics.
- Examination of conditions leading to chemical instability (gain and phase lag criteria).
- Investigation of state instability, involving sleep onset, blood gas changes, and arousal.
- Consideration of the interplay between chemical and state instability mechanisms.
Main Results:
- Periodic breathing occurs at the lowest points (nadir) of ventilatory oscillations during sleep.
- Chemical instability, defined by loop gain ≥ unity and 180° phase lag, explains periodic breathing in hypoxia and heart failure.
- State instability, characterized by ventilation decline, blood gas changes, and arousal, also drives periodic breathing.
- Interactions between chemical and state instability can lead to complex oscillatory breathing patterns.
Conclusions:
- Ventilatory periodicities and apneas in sleep are primarily driven by either chemical instability or state instability.
- Chemical instability arises from the feedback control system regulating breathing, while state instability relates to sleep state transitions.
- These two mechanisms can interact, contributing to the diverse patterns of abnormal breathing observed in sleep disorders.