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Respiratory, cardiovascular, and metabolic adjustments to hypoxemia during sleep in piglets
1Department of Pediatrics, The Jeremy Rill Center for SIDS and Control of Breathing Disorders, Montreal Children's Hospital, McGill University, QC, Canada. acotpul@mch.mcgill.ca
Insights
Active sleep significantly alters how piglets respond to low oxygen levels (hypoxemia), affecting breathing and blood flow to the brain and respiratory muscles. These sleep-dependent changes are crucial for understanding physiological responses during hypoxemia.
Area of Science:
- Physiology
- Sleep Science
- Neonatal Research
Background:
- Sleep influences physiological functions including ventilation and cardiovascular regulation.
- Hypoxemia presents a significant challenge to physiological systems, particularly in developing organisms.
- Understanding sleep's role in hypoxemia is critical for neonatal care and developmental physiology.
Purpose of the Study:
- To investigate the impact of sleep states on physiological responses to moderate hypoxemia in piglets.
- To examine age-related differences in sleep-dependent responses to hypoxemia.
- To determine the specific effects of active sleep on ventilation, metabolic rate, and blood flow distribution during hypoxemia.
Main Methods:
- Measurements of ventilation and metabolic rate in a metabolic chamber.
- Blood flow assessment using the microsphere technique.
- Cardiac output monitoring via dye-dilution and continuous monitoring of oxygen saturation (SaO2).
Main Results:
- Sleep did not alter metabolic or cardiac output responses to hypoxemia.
- Active sleep was associated with reduced ventilatory response and altered breathing patterns in older piglets.
- Active sleep led to increased brain blood flow during hypoxemia.
- Age influenced ventilatory and metabolic responses to hypoxemia, but not cardiovascular responses.
Conclusions:
- Active sleep is the primary driver of sleep-dependent alterations in physiological responses to moderate hypoxemia.
- Age-related differences in ventilatory responses to hypoxemia are linked to variations in oxygen consumption.
- Findings highlight the critical role of sleep state in modulating cardiorespiratory adjustments during hypoxemia in developing mammals.
Abstract:
The influence of sleep on ventilation, metabolic rate, cardiovascular function, and regional distribution of blood flow during hypoxemia (PaO2 of 45-50 mm Hg (1 mm Hg = 133.3 Pa)) was studied in piglets at 6+/-1 and 34+/-5 days (mean+/-SD). Measurement of ventilation and metabolic rate was done in a metabolic chamber, and blood flow was measured using the microsphere technique. A subgroup of animals was instrumented for cardiac output measurement (dye-dilution technique) and continuous monitoring of the hemoglobin saturation in oxygen (SaO2). We found that although sleep did not influence the metabolic and cardiac output response to hypoxemia, it affected the ventilatory response as well as the brain and the respiratory muscle blood flows. During active sleep in the older animals, the ventilatory response to hypoxemia was smaller than in the other two states; marked drops in SaO2 occurred with changes in the breathing pattern; and that state was associated with the highest rate of brain blood flow. As well, age affected the ventilatory and metabolic response, but not the cardiovascular response to hypoxemia. The age-dependent ventilatory changes with hypoxemia (smaller ventilatory response in the young than in the older animals) were related to the different levels of oxygen consumption. In summary, active sleep was responsible for all the sleep-dependent changes in the response to a moderate degree of hypoxemia.