30 - Respiratory Physiology and Regulation

Breathing Underwater and CO2 Levels

• Understanding CO2 Levels when Swimming Underwater:

  • When you hold your breath underwater, CO2 levels in your body:

  • Increase (Answer: A)

  • Holding your breath leads to CO2 accumulation because you are not exhaling, which can trigger a dive reflex that prioritizes oxygen conservation until resurfacing is possible.

Effect of CO2 on pH Levels

• Impact of Increased CO2 on pH:

  • The buildup of CO2 in the bloodstream results in an increased production of H⁺ ions, leading to a decrease in pH (making the blood more acidic).

  • Therefore, as CO2 increases, pH will:

  • Decrease (Answer: B)

  • This shift in pH can affect various bodily functions, influencing respiratory drive and metabolic processes consistently.

Regulating pH Levels

• Upon surfacing, options for restoring normal pH include:

  • Breathe Faster:

  • This method rapidly increases CO2 elimination, helping to correct acidosis in the bloodstream.

  • Breathe Slower:

  • Slowing down breath might lead to a controlled accumulation of CO2, which may be necessary in certain physiological conditions.

  • Clicker Application:

  • Considerations include an increased breathing rate during exercise or high-stress situations to manage fluctuating pH levels effectively.

Hyperventilation and CO2 Levels

• Hyperventilation:

  • This condition results in abnormally decreased levels of CO2 due to rapid and shallow breathing leading to respiratory alkalosis.

  • Suggested method to counter hyperventilation:

  • Breathing into a paper bag:

  • This practice allows a person to rebreathe exhaled CO2, thus normalizing CO2 levels and re-establishing a balanced state.

Ventilation Regulation by CO2

• CO2 as a Key Regulator:

  • CO2 levels serve as the primary driver for adjusting the respiratory rate and depth to maintain proper gas exchange and homeostasis in the body.

  • Minute Volume Equation:

  • (Total Pulmonary Ventilation = Ventilation Rate × Tidal Volume)

  • As PCO2 increases, the ventilation rate increases linearly to expel excess CO2 and restore normal pH levels.

Chemoreceptors and Breathing Control

• Chemoreceptors Role:

  • Central chemoreceptors located in the medulla oblongata and pons, along with peripheral chemoreceptors in the carotids and aortic arch, continually monitor blood pH, O2, and CO2 levels.

  • Changes in arterial PCO2 or acidity (indicated by H+ concentrations) have direct effects on respiratory rate, prompting needed adjustments.

  • Central Chemoreceptors:

  • These are the primary drivers of respiratory control, primarily responding to increases in CO2 levels which stimulate breathing.

Understanding Low PO2

• Low PO2 Effects:

  • Decreased PO2 has only a minor impact on ventilation; the primary stimulant for ventilation is increased CO2 levels.

  • O2 levels have a more pronounced influence on ventilation predominantly under conditions of hypoxia, where oxygen deficiency occurs.

Central Pattern Generator and Voluntary Control

• Voluntary Control of Breathing:

  • Breathing can be managed voluntarily through input to the brainstem, which does not solely rely on chemoreceptor feedback. This ability enables activities such as speaking, singing, or swimming without losing breath control.

Carbon Monoxide (CO) Poisoning

• Risks of CO Exposure:

  • Carbon monoxide competes with oxygen for binding sites on hemoglobin, disrupting normal oxygen transport.

  • CO's affinity for hemoglobin is approximately 200 times greater than that of oxygen, which means even small amounts of CO can significantly displace O2, leading to tissue hypoxia and severe health consequences.

High-Altitude Sickness and Response

• Physiology of High Altitude Effects:

  • Primary Challenge: The decrease in atmospheric PO2 poses substantial challenges to the cardiovascular and respiratory systems.

  • Ventilation Response: A physiological adaptation occurs, involving hyperventilation to counteract low oxygen availability, leading to decreased PCO2 and consequently resulting in respiratory alkalosis.

  • Pulmonary Effects:

  • Vasoconstriction of pulmonary arterioles can occur, which increases pulmonary hydrostatic pressure and can lead to a severe condition known as pulmonary edema (HAPE).

  • Symptoms:

  • Affected individuals may experience shortness of breath, fatigue, and in severe cases, cough with possible pink, frothy sputum due to fluid accumulation.

  • Treatment:

  • The most effective treatment is to descend to lower altitudes and if necessary, administer supplemental oxygen to alleviate symptoms