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