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Acute systemic blood pressure elevation in obstructive and nonobstructive breath hold in primates
S G White1, E C Fletcher, C C Miller
1Department of Medicine, Houston Veterans Affairs Medical Center, Texas, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 1, 1995
Summary
Negative intrathoracic pressure (NIP) changes during obstructive apnea (OA) do not significantly impact blood pressure (BP) response in anesthetized baboons. These findings suggest mechanical factors may play a minor role in BP elevation during apnea.
Area of Science:
- Cardiovascular Physiology
- Respiratory Physiology
- Sleep Medicine
Background:
- Obstructive apnea (OA) in humans causes a characteristic blood pressure (BP) increase, often attributed to negative intrathoracic pressure (NIP) release.
- The precise role of NIP in mediating BP changes during apnea remains incompletely understood.
Purpose of the Study:
- To investigate the contribution of mechanical factors, specifically NIP, to BP elevation during obstructive apnea (OA).
- To compare BP responses between mechanically obstructed apneas and non-obstructive apneas in an animal model.
Main Methods:
- Created single obstructive apneas (OAs) and non-obstructive apneas (e.g., paralysis, ventilator cessation) of fixed durations (30, 45, 60s) in anesthetized baboons.
- Measured systemic blood pressure (BP) before apnea (T0), during the last 5s of apnea (T1), and during the first 5s after respiration resumed (T2).
- Monitored NIP fluctuations during apneas.
Main Results:
- Despite significant NIP and BP fluctuations during OA, no significant differences in BP elevation were observed between OA and non-obstructive apneas at T0, T1, or T2 for any tested duration.
- BP levels at the end of apnea (T1) and immediately after resumption of respiration (T2) did not differ between obstructed and non-obstructed conditions.
- The resolution of NIP changes upon obstruction release did not accentuate BP increases compared to non-obstructive apneas.
Conclusions:
- Mechanical changes related to NIP do not appear to be a major determinant of the overall maximum BP response during obstructive apnea in this anesthetized baboon model.
- Caution is advised when extrapolating these findings to human sleep apnea due to physiological differences between anesthetized animals and humans during natural sleep.