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Effect of chronic resistive loading on hypoxic ventilatory responsiveness
H E Greenberg1, R S Rao, A L Sica
1Division of Pulmonary and Critical Care Medicine, Long Island Jewish Medical Center, Albert Einstein College of Medicine, New Hyde Park, New York 11040, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 1, 1997
Summary
Endogenous opioids acutely suppress ventilation after airway resistance increases. This opioid effect on breathing diminishes over time, even though CO2 sensitivity remains impaired long-term.
Area of Science:
- Respiratory Physiology
- Neuroscience
Background:
- Increased airway resistance can acutely depress ventilation.
- Endogenous opioids are implicated in this ventilatory depression.
Purpose of the Study:
- To investigate the chronic effects of increased airway resistance on hypoxic ventilatory responsiveness.
- To determine the role of endogenous opioids in these responses over time.
Main Methods:
- Tracheal banding in rats to increase airway resistance.
- Measurement of ventilation and hypoxic ventilatory response using barometric plethysmography.
- Administration of naloxone to assess opioid receptor blockade.
Main Results:
- Obstructed rats showed hypercapnia and suppressed hypoxic ventilatory response acutely post-surgery.
- Naloxone partially reversed acute hypoxic ventilatory suppression.
- Hypoxic responsiveness returned to control levels by 6 weeks post-surgery.
- Naloxone had minimal effect on hypoxic responsiveness at 6 weeks.
Conclusions:
- Endogenous opioids acutely modulate ventilatory control following airway loading.
- The influence of opioids on hypoxic ventilatory response wanes significantly within 6 weeks.
- This contrasts with persistent CO2 sensitivity deficits, suggesting distinct mechanisms over time.