Step I Lung & Chest Wall

[Oblique]

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Can someone help me understand this graph in first aid (p. 597)
I would like to understand the very basics of what this graph is trying to illustrate. Thanks

 

[K.E.]

it's describing expansive forces of chest wall when breathing in or out it also illustrates recoil of lung compared with chest wall when breathing in and out

 

[K.E.]

the two forces "expansile" are equal and opposite during inspiration and expiration

 

[Dharma]

…equal and opposite when reaching that balance point at FRC; so after a normal exhalation this would be the volume in lungs afterwards (RV + ERV). Notice that where the green line intersects at 0, the distance of each line (representing chest wall expansion and alveolar collapse) is equidistant to that point. (Just remember, as FA mentions, that intrapleural pressure is still negative at this point to prevent pneumothorax).

If this doesn't make sense, go back to the lung spirometry diagram to help work through this.

 

[Oblique]

Thank you for the replies. I think I have a good idea of the concepts illustrated here.

…equal and opposite when reaching that balance point at FRC; so after a normal exhalation this would be the volume in lungs afterwards (RV + ERV). Notice that where the green line intersects at 0, the distance of each line (representing chest wall expansion and alveolar collapse) is equidistant to that point. (Just remember, as FA mentions, that intrapleural pressure is still negative at this point to prevent pneumothorax).

If this doesn't make sense, go back to the lung spirometry diagram to help work through this.

Can you please explain how negative intrapleural pressure prevent pneumothorax? I understand that a negative intrapleural pressure will help prevent the alveoli from collapsing (atelectasis), but how does it prevent a pneumothorax?

 

[HatWobble]

Can you please explain how negative intrapleural pressure prevent pneumothorax? I understand that a negative intrapleural pressure will help prevent the alveoli from collapsing (atelectasis), but how does it prevent a pneumothorax?

Preventing the alveoli from collapsing and preventing the pleural space from inflating (i.e. pneumothorax) are one in the same, really. The negative pressure keeps the visceral and pareital pleural sucked together so a pneumothorax doesn't form, thus letting the lung stay inflated. If pleural pressure > zero then the pleural space would inflate (i.e. pneumothorax) and prevent the lung from expanding.

 

[Oblique]

Preventing the alveoli from collapsing and preventing the pleural space from inflating (i.e. pneumothorax) are one in the same, really. The negative pressure keeps the visceral and pareital pleural sucked together so a pneumothorax doesn't form, thus letting the lung stay inflated. If pleural pressure > zero then the pleural space would inflate (i.e. pneumothorax) and prevent the lung from expanding.

Thanks!