Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

22. The Respiratory System

Pressure in the Lungs and Pleural Cavity

Anatomy & Physiology

22. The Respiratory System

Pressure in the Lungs and Pleural Cavity

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Problem 28

Textbook Question

Cary hyperventilates for several minutes before diving into a swimming pool. After he enters and begins swimming underwater, he blacks out and almost drowns. What caused this to happen?

Verified step by step guidance

Understand the physiological effects of hyperventilation: Hyperventilation involves rapid and deep breathing, which decreases the level of carbon dioxide (CO2) in the blood (hypocapnia). CO2 is crucial for regulating the body's pH and stimulating the breathing reflex.

Recognize the role of CO2 in the breathing reflex: The primary drive to breathe is triggered by rising CO2 levels in the blood, not by low oxygen (O2) levels. Hyperventilation reduces CO2 levels, delaying the urge to breathe even as oxygen levels drop dangerously low.

Analyze the impact of reduced CO2 levels underwater: When Cary hyperventilates before diving, his CO2 levels are already low. As he swims underwater, his oxygen levels decrease, but the low CO2 levels fail to trigger the breathing reflex in time to prevent hypoxia (low oxygen).

Understand the consequences of hypoxia: Hypoxia can lead to loss of consciousness (blackout) because the brain is deprived of sufficient oxygen to function. This is particularly dangerous underwater, as it increases the risk of drowning.

Conclude the sequence of events: Cary's blackout was caused by hypoxia due to delayed breathing reflex from hyperventilation-induced hypocapnia. This highlights the importance of avoiding hyperventilation before underwater activities to prevent such incidents.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hyperventilation

Hyperventilation is a condition characterized by rapid or deep breathing that leads to an excessive loss of carbon dioxide (CO2) from the bloodstream. This can result in respiratory alkalosis, where the blood becomes too alkaline, causing symptoms such as dizziness, tingling, and even loss of consciousness. In Cary's case, hyperventilation before diving likely reduced his CO2 levels, impairing his body's natural urge to breathe while underwater.

Oxygen Deprivation

Oxygen deprivation occurs when the body or a part of the body does not receive enough oxygen to sustain normal physiological functions. When Cary hyperventilated, he may have felt a temporary sense of euphoria or lightheadedness, but as he swam underwater, the lack of CO2 buildup would delay his body's response to breathe, leading to a critical drop in oxygen levels and ultimately causing him to black out.

Swim Safety and Blackout Risks

Swim safety involves understanding the risks associated with swimming, particularly in relation to breath-holding and underwater activities. A blackout while swimming can be life-threatening, as it can lead to drowning. Cary's experience highlights the importance of recognizing the dangers of hyperventilation and the need for proper training and awareness of safe practices when engaging in underwater swimming.

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In the context of lung physiology, what is the typical state of intrapleural pressure during normal breathing?

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Why is the pressure in the pulmonary circulation lower than in the systemic circulation?

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Which pressure actually keeps the lungs from collapsing?

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The contraction of the diaphragm and the external intercostal muscles begins inspiration. What happens, in terms of volume and pressure changes in the lungs, when these muscles contract?

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