Lecture notes, lecture Breath Holding and Hyperventilation PDF

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Breath Holding and Hyperventilation Hyperventilate - fast and deep breathing - increased pH (decreased CO2 and increased pO2) - Increasing ventilation beyond that required to meet metabolic needs (hyperventilation). BREATH HOLD = APNOEA Applications: - hunting, gathering, competition, warfare, diving - free-divers rely only on the air they can hold in their lungs When holding breath after hyperventilation, decreased demand of oxygen as blood is loaded (with increased O2) Temperature of water slows the heart (rate) down If you keep breathing into a sealed bag  increase in CO2 level - therefore, breaths will be slower or more shallow The rising concentration of pCO2 is primarily responsible for the drive to end breath-hold. Involuntary mechanism controlled by specialized centers in the brainstem normally overrides voluntary breath-holding and causes the breath that defines the breakpoint. Hyperventilation is the most well-known manipulative practice used to increase breath-hold time. Basis: - Difference between high concentration of CO 2 in the body and low concentration in the air. - Hyperventilation can rapidly reduce pCO2 levels. Breath-hold dive prolonged since the drive to breathe will not develop until the normal trigger point of CO2 is reached. - still prolonged compared to holding tidal breath PRIMARY RISK: - hypoxia (decrease pO2) and loss of consciousness 1) Breathing Cycle Ventilatory cycle consisting of an inspiration followed by the expiration of a volume of gas called the tidal volume.

Normal – high amplitude and longer time Rapid – low amplitude and high frequency If inspiring or expiring deeply, the amplitude will increase and length (of time) will increase (less frequency). 2) Effect of holding the breath Breath holding increases the rate and depth of the subsequent respiratory pattern. Breath can be held longer following forced inspiration. 3) After holding – the urge to breathe is: Inspiratory if breath is held on an empty lung Expiratory if the breath is held on a full lung. 4) Hyperventilation - Increased rate and/or depth of breathing - Increasing ventilation beyond that required to meet metabolic needs - increased pH (decreased CO2 and increased pO2) After hyperventilation, the breath is held for longer than normal breathing. 5) When could hyperventilation provide a significant advantage? Athletic performance - Decreased CO2 and increased pO2 o Hypocapnia and ____ - Blood pH is increased [more alkali] - Augment greater Cardiovascular (CV) performance due to better tolerance of accumulating metabolic waste products.

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Rebreathing from a closed bag results in arterial hypercapnia (raised partial pressure CO2) This evidently stimulates respiration

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Rebreathing showed increased DEPTH and increased FREQUENCY in the cycle

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when hyperventilating, the air is moving in and out of the body too rapidly which, in turn, brings the level of carbon dioxide in the blood below normal. Low carbon dioxide levels cause the calcium levels in the body's fluids to also go below normal, which affects the nerves (hence the tingling and dizziness).

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When breathing into a paper bag (more calmly and slowly, if possible) will increase the carbon dioxide level in the bag. Then, as you rebreathe the air you just exhaled, the increased level of carbon dioxide in the air you're in taking will increase the level of CO2 in your bloodstream and restore your calcium levels.

7) Heart rate trace while breath held. - decreased demand of oxygen as blood is loaded (with increased O2) - decreased demand for respiration to replenish reserves - therefore, decreased HR - HR relaxed Diagrams in Q1 8) Which part of nervous system is activated? The spinal cord consists of the Brainstem which is involved in life sustaining functions. Part of the brainstem, the Medulla Oblongata, controls heartbeat, breathing, blood pressure, digestion Breathing slowly and mindfully activates the hypothalamus, connected to the pituitary gland in the brain, to send out neurohormones that inhibit stress-producing hormones and trigger a relaxation response in the body.

FURTHER QUESTIONS 1) Hypercapnia is a condition of elevated partial pressure of carbon dioxide. Detected by chemoreceptors in the aortic and carotid bodies and powerfully stimulates ventilation (respiration) through effects on pontine nuclei. Results from increased production as during exercise or reduced elimination as in reduced alveolar ventilation. 2) When breathing underwater with scuba equipment, the tank at supplies gas higher than atmospheric pressure to overcome the extra pressure imposed by the overlying water. According to Boyleʹs Law, during ascent when the pressure falls, the volume of gas contained in the lungs will expand. If not permitted to escape through the mouth, it will damage the lung, sending air into the bloodstream.

FROM THE WEB – 1

1) Variations in heart rate during the breathing cycle are believed to be due to variations in activity in the vagal nerve supply to the heart. What is the effect of the vagus nerve on the heart?

2) What other nerves control heart rate?

FROM THE WEB - 2 Exercise 1: Normal respiration 1. Describe the normal respiratory movements. Note the characteristics of the trace such as the rate, and the relative durations of inspiration (breathing in) and expiration (breathing out). 2. In your own words, explain the effect of holding the breath on the subsequent respiratory pattern. 3. During which phase of respiration can the breath be held longer? 4. After holding the breath, is the resulting urge to breathe expiratory or inspiratory? 5. Did breathing recovery after holding the breath differ for expiratory and inspiratory phases? Exercise 2: Hyperventilation 1. In your own words, define hyperventilation. 2. After hyperventilation, is the breath held for a longer or shorter duration compared to holding the breath after normal breathing? 3. When could hyperventilation provide a significant advantage? (Athletic performance, for instance? If so, how?) Exercise 3: The effect of rebreathing 1. Describe the effects of rebreathing that you observed. 2. Rebreathing from a closed bag results in arterial hypercapnia (raised partial pressure of carbon dioxide), which stimulates respiration. How was this evident in this exercise? (That is, did the depth or rate or both increase during rebreathing compared to normal breathing?) Exercise 4: Breathing and heart rate 1. In what way does the heart rate change during the breathing cycle? 2. What happened to the heart rate trace while the breath was held? Did this effect occur similarly in other volunteers?...