STATIC MECHANICAL PROPERTIES OF THE LUNGS, DIAPHRAGM AND CHEST WALL ch 7
Air flows along a ____ pressure gradient during inhalation A single alveoli cannot collapse spontaneously on its own because of
Negative Alveolar interdependence (mesh like system)
At end of expiration transmural pressure is Pressure between alveoli and airway is
+5 Equal, both at atmospheric ->so no air flows in
Sequence of evens for expiration
1. Inspiratory muscles relax, diaphragm rises, rib cage descends due to recoil of costal cartilege 2. Thoracic cavity volume decreases-> intrapulmonary V decreases as lung recoil as well 3. Leading to increased intrapulmonary pressure +1 mmHG, so gases flow OUT of lungs Dow pressure gradient until intrapulmonary pressure is 0 mmHg.
Sequence of evens for inspiration
1. Main inspiratory muscle aka diahpram contracts , descends an drib cage RISES 2. VOLUME IN THORACIC CAVITY INCREASES 3. Lungs expand/stretch, lung volume increases 4.intrapulmonary pressure DROPS (due to decreased lung volume) 5. Air flows INTO lungs down pressure gradient until intrapulmonary pressure is ZERO (was -40ish) aka equal to atmospheric pressure (due to decreased intrapulmnary pressure after lung volume expanded due to diaphragm going down and ribs raising via bucket handle action)s
Hysteresis: If observing the compliance of lung and its perspective volume during inhalation and exhalation Difference in compliance (change volume/change pressure) is due to the additional energy required to 1. overcome surface tension during inspiration as well as the energy required to 2. Recruit additional alveoli in the mesh honeycomb system Cosnequently, lung volume ay any given pressure is smaller during inspiration, than during expiration aka recoil does not need to
1. Recruit and inflate additionally alveoli 2. Overcome surfactant surface tension forces So recoil occurs at a faster rate then inspiration (hysteresis)
Three reasons intrapleural p is always negative:
1. The surface tension of the alveolar fluid. • The surface tension of the alveolar fluid tends to pull each of the alveoli inward and therefore pulls the entire lung inward (due to bonding between the amphoteric dipalmitoyl lecithin). Surfactant reduces this force. 2. The elasticity of the lungs. • The abundant elastic tissue in the lungs tends to recoil and pull the lung inward. As the lung moves away from the thoracic wall, the pleural cavity becomes slightly larger. The negative pressure this creates acts like a suction to keep the lungs inflated. 3. The elasticity of the thoracic wall. • The elastic thoracic wall tends to pull away from the lung, further enlarging the pleural cavity and creating this negative intrapleural pressure. The surface tension of pleural fluid resists the actual separation of the lung and thoracic wall.
Surfactant produced ___ weeks of gestation onwards Consists of
28 wks Dipalmitoyl lecithin
Inspiration is a ______ process
Active process with helo of respiratory muscles and diahgpram contraction/moving downwards
During rest alveolar pressure is ___ During active inspiration alveolar AND pleural pressure becomes ____
Atmospheric SUBatmospheric (less than pressure in the airway) so gas can go into the lungs down its conc gradient (lungs fill with air during inspiration) with the help of volume increasing in the thoracic cavity due to chest muscles contracting (expanding)
During inspiration the LOWER ribs move in a ___ ____ action to increase the TRANSVERSE diameter of the thoracic
Bucket handle
Distensibilty of lung formula
C(compliance) = change V/ change P
Aside form lubrication and reducing heat buildup from friction an important job of the pleura is to Without it the lung can
Create surface tension to cause lung to remain against the thoracic Collapse
Main breathing muscle is the Accessory muscles _____ breathing
Diaphragm Augment
Pressure and tension in an alveoli are Pressure and radius are
Directly related Inversely related
Type 2 alveolar cels have what on their surface Respiratory membrane thickness Surfactant phospholipid talks face
Microvilli and are cuboidal 1/2 micron Inward
FRC (functional residual capacity)
ERV + RV Amount of air left in lungs after normal passive exhalation (AKA how much air your lungs can clear)
At TOTAL lung capacity (max level of inhalation or max air lung can hold)
Elastic recoil of BOTH lung and chest wall is directed inward (lung recoil is greater; lung wants to collapse), favoring decrease in lung volume
Functional Residual Capacity (FRC)
Elastic recoil of chest all si EQUAL and OPPOSITE to elastic recoil of lungs . Lungs and chest wall are in equilibrium
Elastic properties of lung and chest wall: At residual volume
Elastic recoil of chest wall is outward and exceeds smaller recoil of lungs inwards
a larger volume of air
Elastic recoil of chest wall is smaller/outwards than elastic recoil of lungs inwards
During active inspiration the ribs are ____ , sternum ____, external intercostal ____ and diapghram ___
Elevated Flares Contract Descends
Emphysema as explaned by the compiance formula
Emphysema creates a GREATER volume, which must be compensated by a smaller pressure in the alveoli in order to have the same C
Surfactant reduces surface tension and pressure is ____ in the large and small bubbles Surfactant increases lung _____
Equalized (Reducing surface tension aka the pressure trying to collapse the alveoli) Complicancy
During a pneumothorax (collapsed lung) the pressure of the pleural ____ atm presssure The pleural is compromised so the lungs ____ and the chest wall/ribs ____ slightly
Equals Collapses (shrink), expand
Airflow stops when p in airway is ___ to pressure at alveoli At this point we can use the pressue at the airway to measure the p of the ____
Equals (point in between insp and exp) Alveoli
Pleural pressure is determined from p in the ____ Alveolar p is determined form p in the _____ (when there is no airflow aka alveolar p is equal to atom p)
Esophagus Airway Recall that as lungs expand intraalveolar p becomes negative / SUBatmospheric, when recoil begins it increases until it reaches or atmospheric (this is point of no airflow in between insp and exp) and once expiration/recoil begins P starts to increases within alveoli to expel air
During passive expiration the inspiratory muscles relax, the lungs recoil (return to smaller size) -> causing the pressure at the alveoli to ______ pressure at the airway opening (aka alveolar pressure > atmospheric), so air flows ____ of the lung and into capillaries
Exceed Out
How much air your lungs can clear And what is in equilibrium
Functional residual capacity Elastic recoil of chest wall outwards and lounges inward is equal and opposite
An increase in resistance or complicancy ____ time it takes to fill the alveoli Effects of pressure needed to extend alveoli at a small versus large area?
Increases Increased filling time at increased compliance means that the larger pressure in the smaller alveoli will be spent on stretching the alveoli so flow into that alveoli ends up being the same as flow into a larger alveoli and prevents air from the smaller one from going into the larger alveoli
During inspiration intrapleural pressure becomes more ____ the trandsmural pressure _____ and th ealveoli are _____, thus ____ alveola rpressure below atmospheric which causes air to flow ___ the lungs
More negative , increases distends , decreasing , Into
Airway potency (open) from the large airway (trachea) level tot he smallest is
Interaction of viscerala and parietal player-> cartilage in the conviction/ dead space -> alveolar septal indedependence (non cartilege bronchioles an dalveoli) -> surface tension created by surfactant within the alveoli
Alveolar pressure throughout the lungs is equalized by surfactant having a greater effect on surface tension if small alveoli (reduced tension and increases complicacency) so more p is spend in filling the alveoli (smaller) ands air does not flow into the ____ ____
Larger alveoli
Effect of gravity one regional ventilation: Alveoli at the apex are ____ sand expand ____ because they are already ______ due to the greater_____ presssure Alveoli at the base of the lung are ___ and expand _____
Larger, less (already expanded), transpumonary p (p between alveoli and pleural space) Smaller, more
Ventilation diff in apex versus base alveoli: Larger apex alveoli have ___ compliance, ___ ventilation, ___ transmural pressure gradient,_ more ____ intrapleuaral pressure
Less (already stretched) Less ventilation Greater transmural p More negative intrpleural p
Perfusion at larger alveoli on Lung apex compared to less distended alveoli at long base: ____ intravascular p, ____ recruitment distensión, _______ resistance, _____ blood flow
Lower Less Higher Lower (blood does not flow as much because there is less gas exchange occurring due to the reduced volume and increased resistance)
Liquid covered lungs require a ___ pressure to maintain a given volume than do lungs filled with air because of elimination of _____-____ interface
Lower Liquid-air
• Intrapleural pressure is the pressure within the pleural cavity. Intrapleural pressure is always ______, which acts like a _____ to keep the lungs inflated. Pleural p. Changes by becoming more ____ during inspiration and retiurining back to its Régular negative state at the end of expiration
Negative, suction Negative o
Static compliance measurements ar Meade during..... Monitors... Includes...
No flow conditions Elastic resistance only Recoil of lungs and thorax
Naturally the elastic recoil of the diaphragm and chest wall pull outwards , while the natural recoil of the lungs pull inwards. Their recoil forced are ____ and equal at rest (no movement)diur Intrpleaural pressure is ____atmoshereic at ___mmhG The pleural is the one thing creating tension between the chest wall/dsiaghgpram and lungs so that the lungs do not collapse In a pneumothorax their sealed pleural cavity is ____ and air flows ___ the pleural membrane
Opposite SUBatmospheric, -3mmHg Opened, in
expiration is a ___ process
Passive process (passive lung recoil aka retuning to normal size)
Collapse of the bronchiole sand alveoli is possible due to their lack of cartilage but doe snot occur because they are attached to the ____via the alveolar septa The outer most layer of the bronchialor walls is surrounded by dense connective to tissue with many ___ fibers
Pleura and chest wall Elastic
Transthorasic p (elastic recoil of chest wall) formula Transpulmonary p (elastic recoil of lungs) formula
Pleural p - p at surface of chest/body surface Alveolar p (airway p figuring no flow) - pleural p (esophogeal p)
Laplace's law Relate p in alveoli (sphere) to surface tension and radius
Pressure in the alveoli is directly proportional to the surface tension and inversely proportional to the radius of the alveoli P=2t/r. *recall t= wall tension
During inspiration the upper ribs move in ____ ____ motion to increase the anterior posterior dimension of the thoracic cavity The
Pump handle
The alveoli are interconnected in a mesh like layer, similar to a honeycomb where the outer layers are connected to the pleura via alveolar ___ If one alveoli collapses it pulls the rest inwards and they all collapse
Septum
During inhalation alveolar pressure is _____ atmospheric During expiration alveolar pressure is ___ than atmospheric Pleural pressure is always ______ at rest, inspiration and expiration . However it becomes MORE negative during _____
Sub. (Air flows into lungs) Greater (air flows out of lungs) Subatmospheric Inspiration
At approximately 70% of total lung air capacity the chest wall recoil reaches ____ and is at
The chest wall recoil equals zero and is at equilibrium
Why is there greater transmpulmonbary p at the alveoli on the apex of the lungs versus alveoli at the base?
The lungs hang by the bronchus, so the mesh network on top are stretched while the ones on the bottom are not (have less alveoli connected sacs pushing down on it) Decreased p at larger alveoli lead to a larger diff betwee pleural and alveoli p so transpulmonary/ p is higher at the apex
acute respiratory distress syndrome (ARDS)
respiratory failure as a result of disease or injury in the ALVEOLI that leads to: ***Inactivated surfactant RBC Diminished BM Hyaline membrane aka smooth m hyperplasia Protease Activated alveolar macrophages secreting cytokines Activated neutrophils Briunchial epithelium sloughing etc.
trans pulmonary pressure
the difference between alveolar and pleural pressures
transplural pressure (diff between p in the alveoli and pleural) is greatest at ..... with the big negative pressure being at the ___
the end of inspiration (so air can flow out of alveoli into pleura) Pleura (-10) and back to zero at the alveoli during the end of inspiration