Chapter 13: Vital Signs: Respiration

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13.2:

Physiological Control of Respiration

JoVE Core
Nursing

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JoVE Core Nursing

Physiological Control of Respiration

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13.1: Respiration

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13.4: Mechanism of Breathing I: Inspiration

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The physiological control of respiration originates from neurons in the medulla and pons. The medulla signals the muscles involved in breathing, and the pons control the breathing rate. Together, these respiratory centers regulate the involuntary control of respiration, whereas the cerebral cortex allows voluntary control of breathing. The most vital respiratory stimulant is carbon dioxide. It causes an increase in respiratory depth and rate. Chemoreceptors monitor arterial blood for changes in the pH and partial pressure of carbon dioxide and oxygen and communicate to the medulla to send nerve impulses to respiratory muscles. From the spinal cord, the phrenic, vagus, and posterior thoracic nerves signal the ascending respiratory pathway to stimulate the diaphragm and intercostal muscles. The function of these muscles involves facilitating ventilation by inducing volume and pressure alterations within the respiratory system. As a result, this conscious effort of ventilation aids in eliminating excess carbon dioxide while simultaneously boosting oxygen levels within the body.

13.2:

Physiological 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 role in ventilation control. An increase in CO₂ triggers the respiratory control system to elevate the rate and depth of breathing, facilitating the removal of excess CO₂ through increased exhalation.

Hypoxemia and Ventilation Control

Patients with chronic lung disease experience ongoing hypercarbia. As a compensatory mechanism, chemoreceptors in the carotid artery and aorta become sensitive to hypoxemia, indicating low levels of arterial O₂. These chemoreceptors are specialized cells that detect changes in the chemical composition of the blood. When arterial oxygen levels fall below a certain threshold, these receptors signal the brain to increase the rate and depth of ventilation. This interplay between hypoxemia and ventilation control, mediated by the chemoreceptors, helps maintain a delicate balance in patients with chronic lung disease.

Supplemental Low-Dose Oxygen Therapy

In cases where arterial oxygen levels fall below 88%, supplemental low-dose oxygen may be required. Continuous long-term oxygen administration has been shown to improve the survival of patients with COPD, a prevalent chronic lung disease. Studies have demonstrated the benefits of supplemental oxygen in managing arterial oxygen levels, reducing the risk of complications such as pulmonary hypertension, and enhancing the overall well-being of individuals with COPD.

Conclusion

The physiological control of respiration is a multifaceted process involving intricate mechanisms to ensure the exchange of gases within the body. Understanding the interplay between factors such as CO₂, O₂, and pH is key to comprehending the regulation of ventilation. Additionally, the significance of hypoxemia and the role of supplemental low-dose oxygen therapy in managing chronic lung disease have been highlighted.