Please make up own values and scenarios Respiratory System: Ventilation Air flow

Question

Please make up own values and scenarios

Respiratory System: Ventilation Air flow (F) is a measure of the volume of air moving in or out of the lungs in a given time frame. Air flow into or out of the lungs is determined by the following equation: F=(P1-P2) / R Pl and P2 are air pressures in specific locations. What specific air pressures do these represent? se of ventilation? Number the following events in the correct sequence for inspiration: Alveolar (intrapulmonary) pressure drops Inspiratory muscles contract Air moves into the lungs Alveolar volume increases What type of pressure is present in the pleural cavity (i.e. negative or positive)? Explain why this pressure is important for inspiration: A condition called pneumothorax results from a puncture through the thoracic wall to the pleural cavity. Explain what effect this would have on the intrapleural pressure, and how this change in pressure would affect ventilation. Why is expiration under resting conditions considered a passive process? In what kinds of circumstances or situations would the body need to engage in active expiration? What muscles are used for this process? Describe two types of abnormalities that would decrease the compliance of the lungs.

Explanation / Answer

Equation F=(P1-P2)/R, is analogous with Ohm's law.

P1 represents atmospheric pressure

P2 represents alveolar pressure

As P1 is atmospheric pressure it's an external factor which cannot be manipulated by the body, so the alveolar pressure P2 is manipulated.

Alveolar pressure drops- 2

Inspiratory muscles contract - 1

Air moves into the lungs-3

Alveolar volume increases - 4

During quiet breathing the pressure in the pleural cavity is Negative.

Negative pressure in the pleural cavity is important for inspiration as it signifies that the pressure in the pleural cavity is less than that of the atmospheric pressure. Air flows from higher pressure area to lower pressure area; thus negative pressure in the pleural cavity helps draw air into the lungs from the atmosphere during inspiration.

In pneumothorax the air reaches the pleural cavity and the pressure is the cavity shifts from negative to equal or more than atmospheric pressure. This increase in pressure within the cavity compresses the lungs leading to collapsed lungs thereby reducing the uptake of oxygen by the lungs. The negative pressure in the cavity under normal conditions facilitate inspiration, so a shift in pressure affects the ventilation process.

Expiration is called as passive process as it doesn't involve any active muscle unlike inspiration. Expiration in resting condition occur due to the recoil effect of elastic tissues in chest, lungs and diaphragm.

Active expiration occurs when there is forced expiration or when the lungs elasticity reduces as in emphysema.

Muscles acting during forced expiration

1.internal intetcostal

2.abdominal Muscles- rectus abdominis, external oblique, internal oblique, transverse abdominis

2.Lattismus dorsi

3.quadratus lumborum

Lung compliance is measure of lungs ability to stretch and expand that is the distensibility of elastic tissue. Decrease in lung compliance occurs in restrictive lung diseases like

Fibrosis of lungs

Interstitial pneumonia

Sarcoidosis

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