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Physio > Mechanics Of Breathing > Flashcards

Mechanics Of Breathing Flashcards

1
Q

Diaphragm

A

. Primary muscle of respiration during quiet breathing
. Dome-shaped sheet of skeletal muscle btw thoracic and abdominal cavities
. When it contracts the vertical dimension of thoracic cavity is inc. and lower rib margins are lifted and moved out to inc. traverse diameter
. Normally only moves 1 cm but can move as much as 10 cm
. Movement accounts for 75% f change in intrathoracic volume during quiet inspiration

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2
Q

Phrenic n.

A

Innervates sides of diaphragm

.. from C3-5

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3
Q

External intercostal mm. Function

A

. Optimize actions of diaphragm
. Connec adjacent robes and when they contrast are pulled upward and forward
. Cause inc. in thoracic dimensions (buckle handle)
. Active during active inspiration, play secondary role to primary action of diaphragm

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4
Q

Accessory mm. Of inspiration

A

. Inc. thoracic volume by raising sternum or upper ribs
. Scalenes and SCM most important (active during forced respiration)
. Others reduce resistance to airflow ( flare nostrils, maintain laryngeal opening)
. Not a lot fo movement during normal breathing but can contact vigorously during exercise/ forced respiration

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5
Q

Muscles of expiration

A

. Abdominal muscles: inc. intrabdominal pressure that exerts upward force on diaphragm to dec. vertical dimension
. Internal intercostal muscles: flatten thorax by pulling ribs down and in dec. front-to-back and side-to-side dimensions
. Both only active during forced expiration

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6
Q

Boyle’s law related to respiration

A

. When volume of enclosed space inc., the pressure dec.

. In respiratory system the changes in volume are due to respiratory muscles

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7
Q

Pressure cycle during inspiration

A

. Contraction of mm. Of inspiration inc. intrathoracic volume
. As thoracic cavity inc., the intraplureal pressure (pressure surrounding lungs) dec. from -4.5 to -8 cm H2O
. As lungs are pulled into a more expanded position the intrapulmonary pressure becomes slightly neg.
. As result air flows into the lungs
. Strong inspiratory efforts dec. intrapleural pressure as low as -40 cm H2O corresponding to stronger degree of lung inflation

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8
Q

What occurs to pressure at end of inspiration and expiration?

A

. The lung recoil pulls the check back into the expiratory position
. The intrapulmonary pressure becomes slightly positive
. Air flows out of lungs
. Expiration during quiet breathing is passive (no muscles contract)

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9
Q

Barometric pressure

A

. Pressure exerted by the weight of air in atm above earth’s surface
. Sea level normally 760 mmHg

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10
Q

Atmospheric pressure

A

. Same as barometric pressure except that atmospheric pressure is at 0 pressure point of reference when measuring pressure inside the body

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11
Q

Intrapleural/pleural/or intrathoracic pressure

A

. Pressure within pleural cavity exerted outside lungs w/in the thoracic cavity
. Usually less than atm pressure

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12
Q

Intrapulmonary/ alveolar pressure

A

. Pressure w/in alveoli
. Alveoli communicate w/ atmosphere through conducting airways ad air flows down it’s pressure gradient any time intrapulmonary pressure differed from atm pressure

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13
Q

Transpulmonary pressure

A

. Difference in pressure to inside and outside of alveoli

. Equal to intrapulmonary pressure minus intrapleural pressure

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14
Q

Airway pressure

A

Pressure w/in airway

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15
Q

Transmural airway pressure

A

. Difference in pressure w/in airway and that surrounding airway
. Pressure surrounding airway w/in thoracic cavity is approx/ same as intrapleural pressure
. Equal to airway pressure minus the intrapleural pressure

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16
Q

Negative intrapleural pressure

A

. When lungs expand and contract they slide w/in pleural cavity
. To facilitate this, a thin layer of serous fluid lies btw visceral and parietal pleura
. Lymph system continuously pumps excess fluid from pleural cavity to create neg. pressure normally found
. Neg. intrapleural pressure keeps the lungs pulled tightly against the parietal pleura of the chest cavity

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17
Q

Pressure-volume curve

A

. Describe elastic properties of the lungs
. When intrapleural pressure dec., the lung expands
. Curve generated while lung is inflated and deflated

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18
Q

Hysteresis

A

. Pressure-volume curve behaves different when lungs is inflated versus when it is deflated
. At any pressure, the volume is greater during deflation than during inflation

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19
Q

Airway closure

A

. Normally at 0 pressure the Lung still has volume
. As pressure surrounding lung approaches 0 or becomes positive, the small airways collapse trapping air inside the alveoli
. Contributes to residual volume

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20
Q

Static compliance

A

C = change volume/change pressure
. Measure of distensibility
. Steep pressure-volume curve indicates high compliance
. Lung volumes near FRC the lung is very compliant, but becomes less compliant as TLC is approached
. At higher lung volumes a greater change in pressure is required to produce a given change in volume

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21
Q

Elastic recoil

A

. Elasticity due to elastin and collagen in parenchyma as well as air-liquid interfacesurrounding bronchioles and pulmonary capillaries
. Elastin stretches, collagen limits stretching
. Opposes lung compliance
. High elastic recoils = low compliance and inflates with more difficulty
. As you age, the recoil dec. and compliance inc. due to fiber changes in lungs

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22
Q

Emphysema effect on lung compliance

A

. Results from release of destructive enzymes (trypsin) from alveolar macrophages in response to smoke exposure destroying elastin network
. Dec. elastic recoil inc. compliance
. At any lung volume, a given change in transpulmonary pressure produces large change in lung volume
. Loss of elastin causes dec. radial traction and keeps small airways stretch open that can result in airway collapse especially during expiration
. Inc. airway resistance

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23
Q

Pulmonary fibrosis effect on lung compliance

A

. Inc. fibrous material w/in lung interstitial
. Causes lungs to stiffen and dec. in compliance
. Elastic recoil inc.
. At any given change in transpulmonary pressure, a smaller than normal change in volume occurs

24
Q

What are conditions that prevent inflation of some alveoli?

A

. Alveolar edema
. Pulmonary venous pressure increased
. Both of these cause dec. lung compliance

25
Q

Surface tension of lungs

A

. Inner surface of alveoli is covered in thin liquid film
. At air-liquid interface in alveoli, the forces btw adjacent molecules of liquid are much stronger than those btw the liquid and the gas next to the liquid
. Surface tension at the air-liquid interface results in SA of liquid becoming as small as possible
.surface tension resists any attempt to inc. that SA as this would inc. the distance btw adjacent molecules of the liquid

26
Q

Surfactant

A

. Liquid film linking alveolar surface
. Produced by type II granular pneumocytes in alveolar wall
. Made up of H2O and DPPC (dipalmitoyl phosphatidyl choline)
. Has low surface tension, minimizes the surface tension in alveoli so lung compliance inc. and work for each breath dec.
. As SA of surfactant film inc., the surface tension inc. (opposite hold true too)that helps maintain stability of alveoli to prevent collapse
. Minimizes fluid accumulation in alveoli by dec. alveolar surface tension

27
Q

DPPC

A

. Lipoprotein complex
. Has detergent-like qualities
. Interferes w/ attractive forces btw H2O molecules

28
Q

Characteristics of lung w/ air-water interface

A

. Surface tension would be large

. Lung would be very hard to inflate

29
Q

Characteristics of lung completely filed w/ saline and air-liquid surface is absent

A

. Surface tension forces would be abolished

. Compliance would be much greater than the air-filled lung

30
Q

Qualities of lung w/ air-surfactant interface

A

. Lung compliance midway between the air-water and saline filled lungs
. Hysteresis is considerable int his lung, but would be greatly reduced in saline=filled and air-water lungs

31
Q

Laplace’s law inn respiratory system

A 
. P = 2T/r
. P = pressure 
. T = surface tension 
.r = radius 
. W/ surfactant the smaller alveoli have lower surface tension than larger alveoli
32
Q

Respiratory distress syndrome

A

. Alveoli unstable and less is less compliant due to inadequate surfactant upon birth
. Open offices in premature births due to majority of surfactant being made between weeks 28-32 weeks

33
Q

Interdependence in respiratory system

A

. Alveoli have honeycomb arrangement and are supported by other alveoli
. If 1 alveolus is reduced or inc. in volume it is opposed by adjacent alveoli
. If alveoli start to collapse, the physical forces exerted by other surrounding alveoli tend to prevent collapse
. If one alveoli overinflate, the surrounding alveoli will tend to prevent this too

34
Q

Elastic properties of the chest wall

A

. The chest wall at FRC has elastic recoil directed outward
. Assists in inspiration
. If wall is expanded beyond its equilibrium position, the chest wall tends to recoil inward
. At volume less than equilibrium position, the recoil of the chest wall is directed outward
. At residual volume the outward recoil of chest wall is large and compliance of chest wall is low determining the RV

35
Q

Resting volume of chest wall

A

. If the chest wall is unopposed by the tendency of the lungs to recoil inwards, the chest wall would expand 70% of TLC
. The respiratory mm. Are at rest
. Pressure difference across chest wall is 0

36
Q

Overall recoil pressure of total respiratory system

A

PRS = PL + PCW
. PL: passive recoil of the lung
. PCW: passive recoil of chest wall
. At volume above FRC it exceeds atm pressure and net recoil favors dec. in lung volume so volume above FRC can only be maintained by mm. Of inspiration
. At volume below FRC it is below atm pressure and favors inc. in lung volume so volume below FRC can only be maintained by mm. Of expiration

37
Q

When are PL and PCW equal but opposite?

A

At FRC
. All respiratory mm. Are relaxed, the lung and chest wall are in equilibrium
. Ches wall is pulled inward by lungs and lungs are pulled outward by chest wall
. Intrapleural pressure is negative and glues the lungs to the chest wall so they move in and out together

38
Q

Puncture pneumothorax

A

. When this occurs the intrapleural pressure inc. to atm pressure
. Unopposed lung tissue will recoil inward while unopposed chest was LL will spring outward
. Results in collapsed lung inward and chest wall continues to spring outward

39
Q

Pulmonary resistance

A

. Consists of pulmonary tisssue resistance and frictional resistance of air moving through airways
. Tissue resistance is caused by friction encountered as lung tissue move against each other when lung expands, contributes to 20% resistance but can inc. in fibrotic conditions

40
Q

Respiratory pressure changes from at rest to vigorous inspiration

A

. At rest the glottis is open and airway pressure is 0, transmural pressure if +5 and expands airways to extent of compliance
. Vigorous inspiration: intrapleural pressure and alveolar pressure is neg creating gradient of 0 at mouth and -15 in lungs so air flows in and dilation of airway
.

41
Q

Respiratory pressure changes during forced expiration

A

. Intrapleural and alveolar pressure is pos.
. Gradient of airway pressure 0 at mouth and +15 a lungs so air flows out
. At some point along airway the intrapleural pressure will be same as airway pressure
. At points closer to the mouth than this point, a neg. transmural pressure would cause airways to collapse w/o cartilage support

42
Q

Dynamic airway compression

A

. Inc. resistance of the airways during forced expiration
. Any additional expiratory effort will not once more air out or inc. expiratory flow rate but instead causes airway to collapse

43
Q

Pressure changes with pursed lip breathing

A

. Creates artificial high resistance at lips
. Causes a greater share of the airway pressure drop to occur at lips rather than along collapsible airways
. Result is airway pressure are maintained during expiration and have reduced tendency to collapse

44
Q

Closing volume

A

. Lung volume at which airway begins to occur

. During forced exhalation some airways at base of the lung close first before the alveoli

45
Q

Closing capacity

A

. Closing volume + residual volume

46
Q

Radial traction and the difference btw elastic recoil and it

A

. Occurs w/ elastic recoil that occurs at high lung volumes
. Traction force on adjacent airways keeps them pulled open
. At lower lung volumes there is less traction and the diameter of airways dec.
. Elastin that surrounds as ingle airway produces radial traction, whereas all elastin in lung acting together produces the lung elastic recoil

47
Q

Max expiratory Flow-volume loops

A

. Curve is constructed by plotting airflow against lung volume when person completes vital capacity maneuver w/ max exhalation
. Airflow peaks near beginning of forced expiration (vol. slightly lower than TLC) then lung volume, elastic recoil, and transmural airway pressure dec. and resistance inc. so rate of flow dec. through remainder of forced expiration

48
Q

Max inspiratory flow-volume loop

A

. Curve generated during rapid forceful inspiration from RV to TLC
. Changes in airflow w/ changes in lung volume differ during max inspiratory and expiratory maneuvers
. Flow reaches high level while lung volume is still low and then flow remains constant until TLC is approached

49
Q

Peak expiratory flow

A

. Increases w/ increasing expiratory efforts
. Occurs near beginning of the expiratory effort at high lung volume
. At lung volumes below FRC the greater air flows are not achieved w/ inc. in expiratory efforts due to airway resistance inc.
. At low lung volumes, expiratory airflow becomes independent of effort from dynamic airway compression w/ more positive intrapleural pressure

50
Q

Peak expiratory flow in pathological conditions

A

. Restrictive disease: PEF and lung volume dec., if PEF is related to absolute lung volume then the flow rate is abnormally high during latter part of expiration from inc. radial traction
. Obstructive: flow rate is low in relation to lung volume, TLF is abnormally large but expiration ends prematurely

51
Q

Elastic work of breathing

A

. Makes up 65% of work
. Done to overcome the elastic recoil of chest wall and lung parenchyma
. Also done to overcome surface tension of alveoli

52
Q

Resistance work of breathing

A

. Work done to overcome the tissue resistance and airway resistance
. Airway resistance makes up 28% work
. Tissue resistance makes up 7% of work

53
Q

Work of breathing during quiet breathing

A

. Very small, Ess. Than 5% of total resting O2 consumption

. breath rate usually 12-20 breaths per minute for minimal work

54
Q

How work is affected from breathing at slow rate

A

. Slow rate w/ large tidal volume inc. elastic work done to overcome elastic recoil of lung tissue and alveolar surface tension
. Seen in people w/ obstructive diseases

55
Q

How work is affected by rapid breathing

A

. Small tidal volumes generates high airflow rates
. Inc. both airway and tissue resistance
. Causes an inc. in resistive work of breathing
. Seen is people w/ restrictive lung diseases

Physio (62 decks)

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