L16 Respiratory Physiology 1 : Volumes And Pressures

Front 1

What is the main function of the respiratory system?

Back 1

Main function of Respiratory System:Provide oxygen (O2) and remove carbon dioxide (CO2)

Front 2

What is the first step in respiration?

Back 2

Ventilation: Exchange of airbetween atmosphere and alveoli

Front 3

What is the second step in respiration?

Back 3

Exchange of O2 and CO2 betweenalveolar air and blood in lungcapillaries by diffusion

Front 4

How is O2 and CO2 transported through the pulmonary and systemic circulation?

Back 4

Transport of O2 and CO2throughpulmonary and systemic circulationby bulk flow

Front 5

How is O2 and CO2 exchanged between blood in capillaries and in tissues?

Back 5

Exchange of O2 and CO2 betweenblood in tissue capillaries and cellsin tissues by diffusion

Front 6

How many lobes does each lung have?

Back 6

Right lung has 3 lobes andleft lung has 2, each canfunction independently

Front 7

What are the Functions of the upper respiratory tract?

Back 7

Filtration, Conditioning of air, Speech

Front 8

How does the upper respiartory tract bring about filtration?

Back 8

An important defence mechanismagainst infection.

Inhaled particles are trapped by hair andmucus in nasal passages.

Particles activate irritant receptorstriggering sneezing reflex.

Excess mucus also passes back topharynx to be removed by swallowing,or is expulsed through nose.

Front 9

How does the upper respiartory tract bring about the conditioning of air?

Back 9

Air passing through nasal cavityis warmed and humidified.

Necessary for optimal gasexchange in the alveoli.

Nasalpassages have a rich blood supplyfor this purpose.

Front 10

How does the upper respiratory tract bring about speech?

Back 10

Larynx contains vocal cords: twofolds of elastic tissue stretchedacross its lumen. These vibrate asair flows across them, producingsound.

Front 11

The lower respiratory tract is divided into 2 zones. What does the conducting zone consist of?

Back 11

Conducting Zone: Trachea & Bronchi

Front 12

What type of pathway is the conducting zone?

Back 12

Low resistance pathway for air flow

Front 13

What keep the airways open?

Back 13

C-shaped bands of rigid cartilage keepairways open

Front 14

What spans ends of cartilage bands?

Back 14

Trachealis muscle spans gaps betweenends of cartilage bands. Contracts to aidexpulsion of blockages, eg. coughingreflex

Front 15

What happens when there is a narrowing if the lumen?

Back 15

Narrowing of lumen increased pressure

Front 16

What do the bronchi branch into?

Back 16

Bronchioles

Front 17

What are the features of the bronchioles?

Back 17

No cartilage.

Smooth muscle bundles.

Normallyrelaxed, allowing air to reach alveoli.Contraction prevents irritants andparticles from entering alveoli.

Front 18

What does the respiratory tract need to defend against?

Back 18

Defence against microbes, chemicals and other foreign matter

Front 19

What does mucus consist of?

Back 19

Mucinfrom goblet cellswater,

NaCl, NaHCO3from sub-mucosal glands

Front 20

What happens in mucociliary transport?

Back 20

Foreign particles trapped in mucus ---> Continuously beating cilia movesmucus gel phase from bronchioles upto the pharynx for ejection bycoughing or swallowing --->

Smoking inhibits cilia movement

---> smoker’s cough

Front 21

What do macrophages do?

Back 21

Macrophages remove bacteria and other small particles

Front 22

What do bronchioles have fewer of?

Back 22

Bronchioles have fewer cilia and less mucus than upper airways

Front 23

What is the respiratory zone of the lower respiratory tract?

Back 23

Respiratory zone =respiratory bronchiolesAlveolar ductsalveoli

Front 24

What is the function of the lower respiratory tract?

Back 24

Respiratory Zone: Gaseous exchange

Front 25

What happens at the respiratory bronchioles?

Back 25

Respiratory bronchioles:Minimal actual gaseousexchange. They branch intoindividual alveoli or alveolarducts.

Front 26

What happens at the alveolar ducts and alveolar sacs?

Back 26

Alveolar ducts and alveolarsacs (40-50 alveoli in eachsac):Site of gaseous exchange.Extensive blood supply,surrounded by capillaries

Front 27

How many alveoli do the lungs contain?

Back 27

Lungs contain ~300x106 alveoli, eachwith diameter of ~0.2mm.

Front 28

What does the very high surface area of the alveoli enable?

Back 28

Very high surface area of ~85m2 andvery thin walls of ~0.2µm, maximisesgaseous exchange.

Front 29

What are the 2 types of alveolar cells or pneumocytes?

Back 29

Type I flattened epithelium(gaseous exchange)Type II thicker cells(secrete surfactant)

Front 30

What are the pores in the lungs?

Back 30

Pores = gaps between alveoli.Allow entry of air even if duct isblocked.

Front 31

What are the overall functions of the lungs?

Back 31

Provides oxygen & removes carbon dioxideForm speech sounds (phonation)

Protection from microbes & other foreign matter

Front 32

What else do the lungs do regarding blood ph?

Back 32

Regulates blood hydrogen ion concentration (pH)

Front 33

What do the lungs remove?

Back 33

Removal of micro-thrombi arising in systemic veins

Front 34

What effect do the lungs have on circulating vasoactive hormones?

Back 34

Removal or deactivation of circulating vasoactive hormones eg. Bradykinin

Front 35

How do the lungs facilitate the conversion of angiotensin I to angiotensin II?

Back 35

Activation of angiotensin II:

Angiotensin converting enzyme (ACE) on surface of pulmonary endothelium convertsangiotensin I into angiotensin II.

Front 36

What is angiotensin II?

Back 36

Angiotensin II = vasoconstrictor, triggers release of aldosterone from adrenal cortex

Front 37

What is the tidal volume?

Back 37

In normal steady quiet breathing, the volume of air inspired isequal to the volume expired. This is the Tidal Volume (VT). ~500ml

Front 38

What is the inspiratory reserve volume?

Back 38

The maximum amount that lung volume can be increased aboveVTis the Inspiratory Reserve Volume (IRV). ~3000ml

Front 39

What is the Expiratory Reserve Volume?

Back 39

After expiring VT, a further maximal exertion of the expiratorymuscles a further volume can be expired. This is the ExpiratoryReserve Volume (ERV). ~1200ml

Front 40

What is the residual volume?

Back 40

Even after maximal expiratory effort, the lungs cannot becompletely emptied, a sizeable volume always remains. This theResidual Volume (RV). ~1200ml

Front 41

Can lung volumes vary between individual?

Back 41

Lung volumes vary between individuals:Influenced by age, gender and height.

Values quoted hereare for an averageyoung adult male

Front 42

What are lung capacities?

Back 42

The sum of two or more ‘volumes’ are known as ‘Capacities’

Front 43

What is the inspiratory capacity?

Back 43

The sum of IRV+VTis the Inspiratory Capacity (IC) ~3500ml

Front 44

What is the Vital Capacity?

Back 44

The sum of IRV+VT+ERV is the Vital Capacity (VC). ~4700ml

Front 45

What is the Functional Residual Capacity?

Back 45

The sum of ERV+RV is the Functional Residual Capacity(FRC). ~2400ml

Front 46

How can some lung volumes and capacities be measured?

Back 46

Some lung volumes and capacities can bemeasured directly using a water Spirometer:

On inspiration, pen moves up

On expiration, pen moves down

Note: Modern versions of this device use forcetransducers and record electronically.

Front 47

Why can't all capacities be measured by this device?

Back 47

Note that because lungs cannot be completely emptied, no ‘baseline’ can berecorded. therefore RV, and all capacities that include RV (FRC and TLC), cannotbe measured directly using this device.

Front 48

What is a graph of these spirometer capacities and volumes?

Back 48

Front 49

What is ventilation?

Back 49

Exchange of air between atmosphere and the alveoli = Ventilation

Front 50

What is minute ventilation?

Back 50

Total ventilation per minute = Minute Ventilation (VE).

Front 51

What is alveolar ventilation?

Back 51

Volume of fresh air reaching alveoli per minute = Alveolar Ventilation (VA)

Front 52

How can minute ventilation be calculated?

Back 52

Minute ventilation (VE) can easily be calculated:If respiratory rate (R) = 12 breaths/min and tidal volume (VT) = 500ml,then: VE = 500 x 12 = 6000 ml/min, or 6.0 L/min

Front 53

Is VA different from VE?

Back 53

Yes, because gaseous exchange occurs primarily in alveoli andminimally in respiratory bronchioles, while pharynx and conducting zoneof lower respiratory tract do not contribute at all to this.

Front 54

What is the anatomical dead space?

Back 54

The volume from the top of the pharynx down to terminal bronchioles isknown as the Anatomical Dead Space.

In adults this is fixed and is ~150 ml.

Front 55

What volume of air remains in the conducting zone from previous breath?

Back 55

150 ml of air remains in conductingzone from previous breath.

Of the 500 ml tidal volume, 350ml will reach the alveoli forgaseous exchange, while 150 mlwill remain in the conducting zoneand not be absorbed.

Front 56

What does VT equal?

Back 56

VT = VD + VA

Alveolar vent. (VA) = minute vent. (VE) - dead space vent.= (500 x 12) – (150 x 12) = 4200 ml/min

Front 57

Is physiological dead space fixed?

Back 57

Although anatomical dead space is fixed, Physiological Dead Spaceis not

Front 58

What is the situation in healthy lungs?

Back 58

In healthy lungs: Anatomical Dead Space = Physiological Dead Space.

Front 59

Why does no gas exchange take place in some alveoli?

Back 59

However, If some alveoli are poorly perfused (with blood), then no gasexchange occurs in those areas. This is the Alveolar Dead Space.

Front 60

What does the physiological dead space equal?

Back 60

Physiological Dead Space = Anatomical Dead Space + AlveolarDead Space

Front 61

What are SI units of pressure?

Back 61

SI units of pressure = kPa (1kPa =7.5mmHg)

Front 62

What are the units of pressure?

Back 62

PressureEg. Atmospheric pressure = Patm

Front 63

How is partial pressure represented?

Back 63

Partial pressure, Eg. of O2 = PO2

Front 64

How is fractional concentration represented?

Back 64

Fractional concentration, Eg. of O2 = FO2(or %).

Front 65

How are inspired, alveolar and arterial pressures and fractional concentrations represented?

Back 65

• Inspired = PIO2, FIO2

• Alveolar = PAO2, FAO2

• Arterial = PaO2, FaO2

Front 66

How does ventilation work?

Back 66

Air moves from a region of high pressure to a region of low pressure

Flow (F) = difference of pressure ∆P or P1-P2 / Resistance R (to the flow)

Front 67

What are the important pressures in ventilation?

Back 67

In ventilation important pressures are atmospheric pressure (Patm)and alveolar pressure (Palv)

F = Palv – Patm / R

Front 68

When does movement into or out of the lungs occur?

Back 68

Movement of air into and out of lungs occurs when Palv becomessmaller or larger than Patm, respectively.

So, in between breaths, when Palv is the same as Patm, there is no flowof air

Front 69

What is Boyles law?

Back 69

The pressure (P) of a fixed amount of a gas (at a constant temperature)is inversely proportional to the volume (V) of the container in which it isplaced.

Front 70

What happens at functional residual capacity?

Back 70

At Functional Residual Capacity (end ofnormal breath out), all respiratory muscles arerelaxed and inward recoil of lungs isbalanced by outward recoil of chest wall.

This generates a negative pressure betweenthe pleural membranes

Front 71

What would happen if the chest wall was opened?

Back 71

If chest wall was opened, intrapleuralpressure would be normalisedwith atmospheric pressure.

Lungs would collapse due to inwardrecoil. Chest wall would expand due tooutward recoil.

Front 72

What is the trans-pulmonary pressure?

Back 72

Difference between alveolar pressureand intrapleural pressure (PIP) is thetrans-pulmonary pressure (PTP).

PTP = Palv – PIP

Front 73

What happens when the chest expands?

Back 73

At FRC, PTP = 0.5 kPa,

But, as chest wall expands, PIPbecomes -0.7 kPa, and PTP increases.

This lowers alveolar pressure

Front 74

What are the Sequence of events in inspiration?

Back 74

Nerves stimulate diaphragm and otherinspiratory muscles to contract,expanding the chest wall ---->

Intrapleural pressure falls – (becomesmore negative -0.7 kPa) ---->

Alveoli are expanded (due toincreased PTP causing increasedpressure difference across alveoli) ----->

Pressure in Alveoli falls (BoylesLaw) ---->

Increased pressure gradient from mouthto alveoli - air flows into lungs

Front 75

What are the Sequence of events in normal expiration?

Back 75

Nerves decrease firing to diaphragm and intercostals, muscles relax. ---->

Expanded chest wall recoils inward ---->

Intrapleural (PIP) pressure goes back towards pre-inspiration levelTranspulmonary pressure decreases to pre-inspiration level ----->

Expanded lungs which have a greater elastic recoil, reduce in size ---->

Air in alveoli gets compressed (Boyles Law) --->

Air flows out of lungs

Front 76

What happens in forced expiration or high ventilation?

Back 76

In forced expiration or high ventilation: abdominal muscles increase recoil ofdiaphragm and speed shrinkage of chest wall and lungs. INTRAPLEURALPRESSURE MAY BE POSITIVE.

Front 77

What does dry air consist of?

Back 77

Dry air = mixture of gases, primarily N2 and O2

Front 78

What are the fractional concentrations of these gases?

Back 78

Fractional concentrations:

FN2 + inert gases = ~0.79 (79%)

FO2 = ~0.21 (21%)

FCO2 = <0.0004 (0.04%)

Front 79

What happens in humidified air?

Back 79

Humidified Air: presence of water vapour alters relativeconcentrations of other gases

Front 80

What is pressure exerted by a gas directly proportional to?

Back 80

Pressure exerted by a gas is directly proportional to:Temperature + number of gas molecules in a given volume(concentration)

Front 81

What is Daltons Law?

Back 81

Daltons Law.

Individual pressure of a particular gas (eg. O2) in a mixture of chemicallynon-reactive gases is called the partial pressure

Front 82

What is the total pressure?

Back 82

Total pressure (P) = sum of all the individual partial pressuresPa + Pb + Pc …

Front 83

What is PO2 if Patm is 101.3 and FO2 is 0.21?

Back 83

In dry air, if Patm = 101.3 kPa and FO2is 0.21Then: PO2 = 101.3 x 0.21 = 21.2 kPa

Front 84

What happens in aerobic respiration?

Back 84

In aerobic respiration, cells require O2 and produce CO2.

O2 must be absorbed from the air and transported to cells

CO2 must transported from cells and released into the air

Front 85

Why are volumes of O2 consumed and expired and CO2 consumed and expired different?

Back 85

Oxidation of organic fuelproduces H2O as well as CO2

Front 86

What is the respiratory quotient?

Back 86

CO2 produced/O2 consumed = respiratory quotient = 0.8

Front 87

What is the Volume O2 transported per min at rest?

Back 87

Alveolar ventilation(VA) = 4.2L/min

21% of 4200ml = 882 ml O2Of this 882ml, 250 ml isabsorbed into blood added toreservoir of 750ml

250ml used by cells per min

Front 88

What is the Volume CO2 transported per min?

Back 88

Tissues produce 200 ml

CO2Per min

Added to a large reservoir of2400ml200ml CO2 expired per min