Related Experiment Video
Updated: Jun 25, 2026
14:09
Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance
Published on: March 21, 2013
[The ventilatory response to isocapnic hypoxia during head-down tilt]
Rossiiskii Fiziologicheskii Zhurnal Imeni I.M. Sechenova
|February 10, 2009
Summary
Body position significantly impacts the ventilatory response to isocapnic hypoxia in rats. The head-down tilt position markedly reduces the lung ventilation response compared to the supine position.
Area of Science:
- Physiology
- Respiratory Physiology
- Cardiovascular Physiology
Background:
- The ventilatory response to hypoxia is crucial for maintaining oxygen homeostasis.
- Body position can influence physiological responses, including respiration.
- Understanding these influences is vital for respiratory and critical care medicine.
Purpose of the Study:
- To investigate the effect of body position on ventilatory response to isocapnic hypoxia.
- To quantify the changes in ventilation during supine and head-down tilt positions.
Main Methods:
- Anesthetized and tracheostomized rats were subjected to rebreathing techniques.
- Isocapnic hypoxia was induced, maintaining constant end-tidal P(A)CO2.
- Ventilatory response was measured as the slope of ventilation against end-tidal P(A)O2 in supine and 30-degree head-down tilt (HDT) positions.
Main Results:
- Maximal minute lung ventilation was significantly higher in the supine position (269 +/- 30%) compared to the HDT position (117 +/- 21%).
- The slope of ventilation versus decreased end-tidal P(A)O2 was threefold greater in the supine position than in HDT.
- These findings indicate a substantial blunting of the hypoxic ventilatory response in the head-down tilt position.
Conclusions:
- Body position demonstrably alters the ventilatory response to isocapnic progressive hypoxia.
- Hemodynamic changes, altered respiratory resistive loads, and modified chemoreceptor/baroreceptor activity likely contribute to these positional effects.
- Further research is warranted to elucidate the precise mechanisms underlying these observed physiological adaptations.
Related Concept Videos
01:25Hyperpnea and Hyperventilation
Hyperventilation refers to a higher-than-normal rate and depth of breathing, often associated with anxiety attacks. This excessive breathing surpasses the body's need to expel CO2, leading to a condition known as hypocapnia - an unusually low level of carbon dioxide in the blood. Hypocapnia can constrict cerebral blood vessels, reducing blood flow to the brain, which may result in dizziness or fainting. Early signs include tingling and muscle spasms in the hands and face, caused by falling...
01:21Acute Respiratory Failure-II
Type I Respiratory Failure, or hypoxemic respiratory failure, occurs when the partial pressure of oxygen (PaO2) in arterial blood falls below 60 mmHg while breathing room air without a corresponding increase in arterial carbon dioxide levels (PaCO2). This condition highlights a significant impairment in the lungs' capacity to oxygenate the blood.
The underlying physiological abnormalities that contribute to hypoxemic respiratory failure include:
The underlying physiological abnormalities that contribute to hypoxemic respiratory failure include:
01:30Alterations in Respiration II
There are numerous types of normal and abnormal respiration. Based on ventilatory movements, breathing patterns are classified as regular, deep, or shallow. Examples include Biot's breathing, Cheyne-Stokes respiration, Kussmaul's breathing, hyperventilation, and hypoventilation. Each pattern is clinically significant and aids in evaluating patients.
In Biot's breathing, the respiratory rate and depth are irregular, alternating between periods of deep gasping and apnea. Common causes include...
In Biot's breathing, the respiratory rate and depth are irregular, alternating between periods of deep gasping and apnea. Common causes include...
01:29Mechanical Ventilation I: Indication and Settings
Mechanical ventilation is a life-saving technique for managing acute respiratory failure and other respiratory complications. The process involves using a machine known as a ventilator to supply oxygen to the lungs and assist in removing carbon dioxide. It serves as a bridge to long-term mechanical ventilation or a temporary measure until ventilatory support is discontinued. The ventilator can maintain this function for a prolonged period, providing critical support for patients until they can...
01:24Pulmonary Ventilation: Inhalation
Pulmonary ventilation is a vital process that ensures the exchange of oxygen and carbon dioxide in the lungs. It refers to the movement of air into and out of the lungs, enabling the body to obtain oxygen and remove waste carbon dioxide. In this article, we will explore the intricacies of pulmonary ventilation, including its underlying principles, mechanisms, and the interplay of pressures within the respiratory system.
Boyle's law becomes particularly pertinent when examining respiratory...
Boyle's law becomes particularly pertinent when examining respiratory...
01:23Physiological Control of Respiration
Introduction
Breathing, a seemingly passive process, is regulated by the respiratory center in the brainstem. This center coordinates the involuntary control of respirations, which means it occurs without conscious effort, ensuring a smooth and uninterrupted pattern.
Regulation of Ventilation
The body maintains ventilation by monitoring levels of carbon dioxide (CO2), oxygen (O2), and hydrogen ion concentration (pH) in the arterial blood. Among these factors, the level of CO2 plays a crucial...
Breathing, a seemingly passive process, is regulated by the respiratory center in the brainstem. This center coordinates the involuntary control of respirations, which means it occurs without conscious effort, ensuring a smooth and uninterrupted pattern.
Regulation of Ventilation
The body maintains ventilation by monitoring levels of carbon dioxide (CO2), oxygen (O2), and hydrogen ion concentration (pH) in the arterial blood. Among these factors, the level of CO2 plays a crucial...