Intrapleural Pressure in pleural cavity is > or < than ATM?
less than ATM (756): keeps lungs expanded and chest wall from overexpanding
So does this mean when intrapleural pressure is < ATM (also < lungs), then lungs are expanded?
Pressure inside lungs equals
ATM (760)
When PrLung< Patm, air rushes into lungs (inhale)
When Plung>Patm, air rushes out of lungs (exhale)
- 5 cm H2O in pleural cavity is > ATM by 5 cm ???
Lung elastic forces want to collapse
chest wall elastic forces want to expand
Lung “elastic forces” (recoil = return back) are due to:
1) collagen and elastin in interstitial matrix
2) surface tension forces in alveoli
Chest wall recoil/elastic forces are due to:
1) tendons and muscles between ribs
Antagonistic action of these forces generates (-) Intrapleural Pressure which counteracts elastic force (recoil): (lungs wanting to collapse and chest wall wanting to expand ??)
Atelectasis
absence of gas from all or part of a lung due to a failure of expansion
What happens if the chest wall (thoracic wall is covered with parietal pleura) is punctured
Pneumothorax: lung collapses, chest wall springs away (because chest wall elastic forces/recoil favor expansion (due to tendons/muscles btw ribs)
???Is it bc air rushes into intrapleural sack and Pis raises and can no longer oppose the recoil of chest wall and lung???
Diaphram contract more during
excercise
When inspire: Vol chest cavity (lungs????) increases and lowers Pip causing lungs to expand
Increase in volume causes decrease in intrapleural pressure
Muscles involved:
Diaphragm: when contracts, it flattens, goes down
external intercostals: elevate ribs and sternum
accessory m: SCM and scalenes : elevate chest only during excercise
Eupnea
resting
During excercise, diaphragm raises or depresses with inspiration?
Depresses (could up t 10 cm)
During eupnea (resting) inspiration
Diaphragm derpresses 1 cm with inspiration
Tidal Volume: Tv (500 ml)
Volume of air moving in and out of lungs with each breath
Residual volume (1200 ml) (RV)
lung volume remaining AFTER maximal expiration.
Vital Capacity (VC) (4500)
Total Lung Capacity (TLC) - Residual Volume (RV)
Maximum of what can be exhales
Total lung capacity (TLC) (5700 ml)
Vital Capacity (VC: all that can be exhaled) + Residual Volume (RV) (can’t be exhaled)
Expiratory reserve volume (ERV) (1000 ml)
additional air that can be exhaled after a normal exhalation
Functional residual capacity (FRC 2200 ml)
Air that’s in reserve: part can be exhaled after normal exhale and part can’t ever be exhales
Expiratory reserve volume (ERV: additional air that can be exhaled after normal) + residual volume (RV: can’t exhale at all)
Restrictive lung disease
Lung and chest walls can’t expand as well: need greater change in intrapleural pressure (Pip) to produce to produce the same change in volume (to push air out or breath in)
Which each inhale or exhale effort, lung volume is reduced
Examples: pulm fibrosis, partial resp muscle paralysis, massive obesity, rib fusion
Pulm fibrosis is an example of
Restrictive Lung Dz
Restrictive Lung Dz
ALL lung volumes REDUCED
(Vt: air in and out) may be unaffected
Reduced:
- TLC (total lung volume) because lungs can’t be expanded
- RV (residual volume: can’t exhale)
But: since both are reduced, the ratio or RV/TLC is NORMAL (0.2-0.3)
Obstructive Lung Dz is due to
increase in airway resistance
Increase:
residual volume (RV) and functional residual capacity (FRC: RV+ERV) (and TLC Total lung volume if chronic)
e.g:
asthma - airways constrict and mucus section increases
bronthitis - inflammation of bronchi, increase mucus and hypertrophy of mucus glands and over time walls: lumen gets smaller
emphysema - alveolar degeneration, increased compliance, airways close early when exhale
COPD - bronchitis and emphysema (chronic obstructive pulmonary dz)
