Answer to Question #315416 in Human Anatomy and Physiology for Sonia

Question

1. Using a spirogram, describe the lung volumes and capacities.
2. Describe what changes are likely to occur in the pulmonary circulation of an adult who ascends to very high altitude.
3. Explain what Laplace’s Law is and how it applies to the lung with surfactant.
4. Describe the difference between alveolar ventilation and minute ventilation. Explain the relationship between alveolar ventilation and PaCO2, PACO2, PAO2, and PaO2.

Answer 1

1.Spirometry is a measurement of lung volumes during quiet breathing, maximum inhalations and exhalations, with forced exhalation. This is the main research method that is necessary for the attending physician to assess the condition of a patient with a lung disease. During spirometry, the following indicators are determined (accepted international designations in brackets):

BF - Respiratory frequency, the number of respiratory movements in one minute. Normally 16-18.

TV Tidal volume - the volume of air in one breath, normally 500-800 ml.

MTV Minute respiratory volume is the amount of air that passes through the lungs calmly in one minute. This parameter reflects the processes of gas exchange in the tissues of the lungs.

VC - Vital Capacity - Vital capacity of the lungs, the volume of air at maximum expiration after maximum inspiration. the maximum amount of air exhaled after the deepest breath.

2.The decrease in PaO2, recorded by peripheral chemoreceptors, leads to activation of the sympathetic nervous system and increased secretion of catecholamines. If the increase in the level of adrenaline is transient, then the increase in the content of norepinephrine nalin in the blood persists for several days. The resultant action is an increase in cardiac output due to an increase in heart rate abbreviations. There is no increase in stroke volume, it even decreases following effect of hypovolemia. The total peripheral resistance increases (observed spasm of peripheral vessels), which leads to an increase in blood pressure and redistribution of blood flow with its centralization (increased blood flow in the heart

and the brain and a decrease in peripheral tissues).

3.According to Laplace's law (Laplace),

P = 2 T/R,

where P is the pressure in the alveoli,

T - surface tension of the alveoli,

R is the radius of the alveoli.

According to the formula, the smaller the size of the alveoli, the more pressure is required to expand them. However, this does not happen normally: the concentration of surfactant is higher precisely in the alveoli of a small radius, the surface tension in them decreases to a greater extent and they are more pliable than the alveoli with a large radius. As a result, during inhalation at the same pressure, the alveoli with different radii expand to the same extent.

4.Minute ventilation is the tidal volume times the respiratory rate, usually, 500 mL × 12 breaths/min = 6000 mL/min. Increasing respiratory rate or tidal volume will increase minute ventilation. Alveolar minute ventilation is less than minute ventilation and is calculated as ([tidal volume − dead space] × respiratory rate) or ([500 mL − 150 mL] × 12 breaths/min) = 4200 mL/min. Increasing tidal volume increases alveolar ventilation more effectively than does increasing respiratory rate (see the earlier discussion of restrictive and obstructive disease). Hypoventilation (reduced alveolar ventilation) decreases PAO2 and increases PaCO2, decreasing PaO2. With pure hypoventilation (A-a) DO2 is not changed.