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The effect of decreased intrathoracic pressure on ventricular function
1Sleep/Wake Disorders Center, Pulmonary and Critical Care Division, Long Island Jewish Medical Center, Long Island Campus for the Albert Einstein College of Medicine, New Hyde Park, NY 11042, USA.
Journal of Sleep Research
|June 1, 1995
Summary
Obstructive sleep apnea (OSA) causes large intrathoracic pressure swings, but experimental data do not strongly support decreased intrathoracic pressure increasing left ventricular afterload. Further research is needed for extreme OSA cases.
Area of Science:
- Cardiology
- Respiratory Physiology
- Sleep Medicine
Background:
- Obstructive apnoeas cause significant decreases in inspiratory intrathoracic pressure (ITP).
- These pressure changes affect cardiac function through altered preload and afterload, influenced by blood volume shifts and hypoxemia.
Purpose of the Study:
- To investigate the cardiac effects of decreased ITP during obstructive apnoeas.
- To evaluate the hypothesis that decreased ITP increases left ventricular (LV) afterload in conditions relevant to obstructive sleep apnea (OSA).
Main Methods:
- Review of animal studies and physiological principles related to ITP swings during obstructed breathing.
- Comparison of cardiac effects between obstructive and central apnoeas.
- Analysis of ventricular interdependence and autonomic modulation.
Main Results:
- Obstructed breathing leads to increased venous return and right ventricular (RV) volume, with decreased LV diastolic compliance and preload.
- Sustained decreases in ITP (Müller manoeuvre) inhibit LV ejection, increasing afterload.
- Short, repetitive ITP decreases during airway obstruction primarily reduce LV stroke volume due to decreased preload, with afterload potentially decreasing initially.
- Obstructive apnoeas increase RV volume, while central apnoeas increase pulmonary blood volume.
Conclusions:
- Experimental evidence does not strongly support the role of decreased ITP in increasing LV afterload in typical OSA.
- The effects of extreme ITP swings and timing differences in OSA require further investigation.