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Page 1: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Physiology of respiration

Page 2: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Respiration – principal and vital function of the respiratory system

• external respiration – exchange of the respiratory gases: atmosphere blood

• internal respiration - exchange of the respiratory gases: blood tissues

• cellular respiration – utilization of O2/ production of CO2 in the cell metabolism

• Respiration

• –function of: respiratory system - cardiovascular system – blood = the transport system

Other functions: vocalization, protection, acid-base balance, metabolic functions, water

and heat balance

atmosphere cells-metabolism

Page 3: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

THE FUNCTIONS OF THE RESPIRATORYPASSAGEWAYS

Page 4: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

A/ Conducting zone• upper respiratory passageways

– nasal cavity (+ paranasal sinuses)– (naso-) pharynx – larynx

• lower respiratory passageways(intrathoracic)– trachea– bronchi – terminal bronchioles

F: conduction, conditioning of the air

B/ Respiratory zone= lung parenchyma

– respiratory bronchioles– alveolar ducts– alveolar saccules– alveoli

F: exchange of the respiratory gases(air – blood)

Components of the respiratory system

Page 5: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

- between trachea and alveoli the airways

divide 23 times

(23 generations of bronchi)

- bronchi

• primary bronchi – branches of trachea

(right, left)

• lobar (secondary) bronchi (3R + 2L)

• segmental...

- bronchioles

• increase in total cross section, and

eventually surface area for gas exchange

(2,5 cm2 → > 106 cm2)

Respiratory bronchiole

Alveolar sac

Tracheobronchial tree = trachea + bronchi

http://medicalpicturesinfo.com/wp-content/uploads/2011/09/bronchial-tree-4.jpg

Page 6: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Tracheobronchial tree - structure

⚫mucosa (innermost layer)

- epithelial cells with cilia

- goblet cells – produce mucus

⚫submucosa – slime glands

⚫smooth muscle

⚫cartilage

- ring- in bigger and medial bronchi

- fixate wall - prevents from collapse

- bronchioles

- lack cartilage

- in bronchoconstriction may cause major resistance to air flow

- the wall of bronchioles is formed especially smooth muscle

Page 7: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Airway smooth muscle

Facts:

• found in the trachea and along the bronchial tree (till terminal bronchioles)

• critically important in regulating bronchomotor tone of the airways

• secretes cytokines, chemokines and extracellular matrix proteins

• may serve as a potential new target for the treatment of chronic lung diseases

Regulation of the smooth muscles in the respiratory passageways

1/ nervous

2/ humoral (paracrine)

Page 8: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Regulation of the smooth muscles in the respiratory passageways

Autonomic nervous system (involuntary)

Parasympathetic nervous system – n. vagus (acetylcholine) – action already in rest

Effects:

- maintenance of basal tone of smooth muscles in airways

- bronchoconstriction (contraction of the smooth muscle)

- increased resistance to airflow

- increased mucous secretion

Sympathetic nervous system (noradrenaline) – no significant

- Adrenal medulla (adrenaline – beta receptors)

Effects:

- cause relaxation of the smooth muscle - dilation of the bronchi

- easier air flow (e.g. in stress, physical activity)

Local factors with bronchoconstricting effect

- histamine (released in allergic reactions)

- irritants in the air, cigarette smoke

Page 9: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Function of the conducting zone

- conduction and conditioning of the air - no gas diffusion between respiratory passageways and blood

• Warming to the body temperature (mainly in paranasal sinuses)- prevents cooling of body center

• Wetting (humidification, moisturizing)

- adding water vapor (diffusion of water through the mucosa)

- 100 % humidity

- prevents drying up of mucosa

- preserving integrity and function of cilia

- important for gas exchange in alveoli

• Filtering/ cleaning

out foreign material (dust, bacteria, etc.)

– by mucociliary transport

- mucosa covered by mucus - retain foreign material

- cilia of the mucosal epithelial cells beat with motion toward pharynx

- when mucus reaches pharynx - may be eliminated from the body

Page 10: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

• nasal cavity

- efficient cleaning of the air by cilia

- efficient warming of the air (mainly in paranasal

sinuses)

• oral cavity

- also allows the breathing

- mostly in case of insufficient ventilation

through nasal cavity (e.g. edema of nasal

mucosa)

- no cilia – insufficient cleaning

- the air bypasses paranasal sinuses –

insufficient heating - irritation

http://t3.gstatic.com/images?q=tbn:ANd9GcQMmvwvKmgcUatUj

Q8A9dGvJPUIUAHutka6iCUs7P7PeXt7KagMsA

Page 11: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Protective mechanisms in the respiratory passageways

• inspired air – contains dust particles, microbes...

• risk – for the respiratory system and the body

• elimination by different protective mechanisms

– reflex

– nonreflex

Reflex mechanisms

• changes in breathing patterns, apnoic reflex, laryngoconstriction,

bronchoconstriction, the cough reflex, the sneeze reflex

Nonreflex mechanisms

• physical (filtration, humidification, warming, local immune mechanisms, mucocilliary

transport, surfactant, oxidative-antioxidant system, system of proteases and

antiproteases

Page 12: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

The cough reflex, the sneeze reflex

• very forceful expiration – to clear the foreign matter out of the respiratory passageways

• stimulus – mechanical, chemical irritation of mucosa

– larynx, trachea, bronchi - cough

– nose - sneezing

• afferent fibres (n. vagus - cough, n. trigeminus – sneeze)

• reflex centre – medulla oblongata

• effector organs – muscles of respiration

Page 13: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Coughing and sneezing reflex involve a series of steps:

1. Inspiratory phase

– deep initial inspiration (2,5 l of air) – decrease in intrapleural and intrapulmonal

pressure

2. Expiratory phase

a/ compression

• epiglottis closes, vocal cords shut

• forceful contraction of expiratory muscles + accessory expiratory muscles

• the pressure in the lungs rises rapidly (to +27 kPa)

b/ expulsion

• vocal cords and the epiglottis suddenly open

• air explodes out under high pressure in the lungs

• the rapidly moving air - carries away the foreign matter

- velocity 150-280m/s (12 l/s)

- cough – through the mouth

- sneezing - through the nose

Page 14: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Production:

- in goblet cells in mucosa and submucosal glands

- 100 ml /24 h (85% are reabsorbed, 15% excreted)

Functions:

▪ mechanical barrier

▪ sticky – can trap the particles, microbes

▪ dilution of toxic substances

▪ optimal environment for cilia

▪ contribution for warming and wetting of the air

▪ contains immunoglobulin A (Ig A) - mucosal immunity

Sticky external layer

▪ thick mucus floats on the surface of the cilia

Watery internal layer

▪ periciliary fluid layer

http://www.ersnet.org/learning_resources_player/breathe/6_4/

8/10.-Review-pathophysiology-web-images/figure-3.jpg

Mucus in the respiratory passageways

Page 15: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Ciliary activity in the respiratory passageways

Mucociliary transport

cilia of the mucosal epithelial cells (50-300/cell)

beating causes the coat of mucus to flow slowly, at a velocity of a few millimeters per minute - mucus with the trapped particles moves in oral direction - when mucus reaches pharynx, may be spitted out

Optimal for ciliary activity:

- humidity >85%; temperature 18-40°C; pH 7-8

Decrease in ciliary activity:

- temperature in airways

- humidity in airways

- irritants – e.g. cigarette smoke

(initial increase, then decrease)

http://www.ersnet.org/learning_resources_player/breathe/6_4/

8/10.-Review-pathophysiology-web-images/figure-3.jpg

http://t0.gstatic.com/images?q=tbn:ANd9GcQkTr4lb97Y_yFl0PM

IE48XKCk_gmj65n5GoA6O-Qojmyd1Ew3_

Page 16: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Mechanical filtration depends on the size of particles

> 10 μm trapping by cilia, nasal cavity, pharynx

1 - 10 μm lower parts of respiratory passageways

0,5 - 1 μm can pass to respiratory bronchioles and alveoli –removal by phagocytosis

< 0,5 μm are not trapped, are expired back to the atmosphere

Page 17: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

MECHANISM OF INSPIRATION AND EXPIRATION (VENTILATION)

Page 18: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

- a cyclic, automatic process

1. inspiration

• air moves from the atmosphere into the lungs

• tidal volume - the volume air inspired in quiet

breathing VT – 500 ml

2. expiration

• the same volume air moves from the lungs into the

atmosphere

- external signs of breathing – movements of the chest and

abdomen

Inspiration and expiration

- the air flow into and out of the lungs is passive

- the main driving force for the air flow is the pressure

differences between the lungs and the atmosphere

Ventilationexchange of respiratory gasses between atmosphere and alveoli

Page 19: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Atmospheric pressureatmosphere

• the atmosphere (mass of air) exerts pressure

- depends on height column, height above see level

- at seal level approx. 100 kPa (1 atm, 760 mm Hg)

• the atmospheric pressure is lower in higher altitudes

- lower density of the air

- thinner layer of the atmosphere

• in physiology pressures in the body

are related the atmospheric pressure

e.g. if pressure in the lungs= 0,1 kPa,

it means, it is by +0,1 kPa higher than

atmospheric pressure

https://i.ytimg.com/vi/O37XuRkS5UE/hqdefault.jpg

Page 20: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

• lungs – lined with a thin membrane

pleura visceralis („sticks“ to the lungs)

• the internal side of the chest is lined with

pleura parietalis („sticks“ to the chest wall)

• between both membranes is a thin space

(intra)pleural space

• the space is filled with small volume of fluid

Pleura, intrapleural space

Page 21: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

The chest and lungs are elastic structures

lungs - exert an elastic recoil directed inwards

thorax - exerts an elastic recoil directed outwards

due to elastic recoil of the lungs and the

chest the pressure in intrapleural space

is lower than the pressure in

atmosphere (= it is subatmospheric)

by – 0,5 to –1,0 kPa in quiet breathing

The negative intrapleural pressure

prevents the lung to collapse

- it holds („pulls“) the lungs against the chest

wall

acts in inspiration and expiration

- lungs follow the chest movements intrapleural space –

negative pressure

Page 22: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Intrapulmonary (alveolar) pressure

- pressure inside the lungs (i.e. in the alveoli)

- when no air flows into/out of the respiratory passageways, the pressures in all

parts of the respiratory tree are equal to the atmospheric pressure

Page 23: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Physical laws in respiration and ventilation

• if two containers filled with air that differ in pressure are

connected, the air moves from the container with higher

pressure into the container with lower pressure

• pressure and volume of air within a closed system is

constant

– i.e. if the volume increases, the pressure

decreases and vice versaV

p

V

p

P1 p2

P1 > p2

Boyle's law

Page 24: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

1. Contraction of the inspiratory muscles =

an active process

A. diaphragm - the main inspiratory

muscle

B. external intercostal muscles

- pull ribs up and out - cause further increase in chest volume

abdominal vs. costal breathing

C. accessory inspiratory muscles – active in forceful breathing

(m. sternocleidomastoideus, mm. scaleni, mm serrati ant.)

Expiration Inspiration

Mechanism of inspiration

2. increase in chest volume

- by 0.5 L in quiet breathing

- diaphragm contraction (approx. 75% of chest expansion) in quiet breathing

- by contraction it descends by 1-1,5 cm / chest volume + 250 - 350 cm3

- forceful breathing - stronger contraction - it descends by 6 -10 cm, chest volume+ 2-3000 cm3

Page 25: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

3. increase in chest volume

- the interpleural negativity „pulls“

parietal pleura outwards

- decrease in intrapleural pressure – becomes more negative

4. lungs expand - decrease in intrapulmonary pressure

– becomes lower than atmospheric

5. the air moves

- from the place with higher pressure (atmosphere)

- to the place with lower pressure (lung)

- until the pressures get equal (= end of inspiration)

Before inspiration inspiration

Page 26: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Mechanism of expiration

• a quiet expiration is passive

(i.e. it does not require

muscle contraction)

1. inspiratory muscles are relaxed

- the diaphragm moves upwards, ribs move downwards

(because of their elastic recoil)

2. chest size decreases

3. pressure in intrapleural space gets increased (less negative)

4. intrapulmonary pressure exceeds atmospheric pressure

5. air moves

- from the place with higher pressure (lung)

- to place with lower pressure (atmosphere)

- expiration is terminated when the pressures in lungs/atmosphere are equal

expiration

Page 27: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Forceful expiration

• active process = requires muscle contraction

Expiratory muscles1. internal intercostal muscles

- move ribs downwards

- further decrease in thoracic volume

2. accessory expiratory muscles – abdominal muscles, chest muscles

expiration

Page 28: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Recapitulation

- characterize mechanism of inspiration in 6 steps

1. contraction of the inspiratory muscles

- diaphragm, external intercostal muscles

2. increase in chest volume

3. decrease of intrapleural pressure - becomes more negative

4. increase of lung volume

5. decrease in intrapulmonary pressure

6. the air moves - from the place with higher pressure (atmosphere) - to the place with lower pressure (lung) - until the pressures get equal (end of inspiration)

Page 29: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

- after expiration / prior to next inspiration

- all the respiratory muscles are relaxed

- the pressure of air in the lungs = atmospheric pressure

Relaxation position of the chest

- increase volume of the air - active process

- decrease volume (expiration) - active process

- starting position for breathing – the least work of

breathing muscles

- in the lung is volume equal to functional residual

capacity (FRC = ERV+RV)

Page 30: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Non-relaxation positions

1. inspiratory positions

- during inspiration, when inspiratory muscles

are contracted

2. expiratory positions

- during expiration, when expiratory muscles

are contracted

- inspiratory and expiratory position are a

result of respiratory muscle activity

(contraction)

Page 31: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

• Inspiration

- starting from relaxation position is active (quiet respiration)

- activity = contraction of inspiratory muscles

• Expiration

- above relaxation position is passive (quiet respiration)

- relaxation of inspiratory muscles

• Expiration

- starting from relaxation position is active (forced expiration)

- activity = contraction of expiratory muscles

• Inspiration

- up to relaxation position is passive (forced breathing)

- relaxation of expiratory muscles

FRC

Relaxation position of the chest

- respiratory muscles (inspiratory and expiratory) are relaxed

- pressure of the air in the lungs = atmospheric pressure

- volume in the lungs = functional residual capacity (FRC)

Page 32: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Pneumothorax

• „a hole“ in the pleura

– due to injury of chest wall, lung disease, etc.

• the intrapleural cavity communicates with the atmosphere

• air enters the intrapleural space

• an increase of the intrapleural pressure

• lack of underpressure, that prevents the collapse of lungs – the lung collapses

• decreased effectiveness of breathing – the lung fails to expand

Page 33: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Pressures in the respiratory system

Intrapleural pressure – quiet breathing

• beginning of inspiration: - 0,5 kPa

• beginning of expiration: - 1,0 kPa

Intrapleural pressure - forceful breathing

• end of inspiration – more negative values

• end of expiration – may be a positive

beginning beginning

of inspiration of expiration

0

-1

0

0,5

0

Intrapulmonary (alveolar) pressure

• inspiration – negative values

a) at the beginning of inspiration – chest expands, decrease of the intrapulmonary pressure

b) later during inspiration - air moves into the lungs – pressure progressively increases (from negative values to zero value)

• expiration – positive values

c ) at the beginning of expiration – chest volume reduces, increase in the intrapulmonary pressure

d) later during expiration - air moves out of lungs – progressive decrease pressure (from positive values to zero value)

Volume of air in the lungs

- increase during inspiration, decrease during expiration

inspiration exspiration

ab

c

d

Page 34: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

LUNG VOLUMES AND CAPACITIES

Page 35: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

- the most common pulmonary function test

- the patient is breathing into a spirometer - he follows the doctor´s instructions how to

breathe: quiet breathing, maximum inspiration, hold the breath, ....

- a record is obtained and evaluated (manually or by a computer)

The functional lung examination (spirometry)

Page 36: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Pulmonary volumes

• tidal volume (TV, VT) - 500 ml–volume of normal inspiration (or expiration)

• expiratory reserve volume (ERV) - 1000 ml– largest additional volume that can be forcefully

exhaled after tidal expiration

• inspiratory reserve volume (IRV) - 2500 ml– largest volume that can be forcefully inspired over

normal inspiration

• residual volume (RV) 1000 - 2000 ml– the volume of air remaining in the lungs after the

most forceful expiration

- collapse volume CV 500 -1000 ml- minimal volume MV 500 -1000 ml

VC

IRV

ERV

VT

Page 37: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

IRV

IC

VT VC TLC

ERV

FRC

RV CV

MV

inspiratory capacity IC = VT + IRVexpiratory capacity EC = VT +ERVvital capacity

VC = VT + ERV + IRV = 4000 ml- maximum volume that can be expired after max. inspiration

VT = 15% VCIRV = 60% VCERV = 25% VC

total lung capacity TLC = VC+ RV - maximal volume of the air in the lungs

functional residual capacity FRC=RV + ERV- the volume in the lungs in relaxation position of the chest- at the after quiet expiration / before next inspiration

Lung capacities

Pulmonary volumes and capacities depend on body size

- greater in large and athletic people than in small and asthenic people

- about 20 to 25 % lower in females than in males

Page 38: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

VENTILATION AND ITS CHANGES

Page 39: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Minute lung ventilation V

• tidal volume (VT) 500 ml

– volume of inspired/expired air in quiet breathing

• respiratory rate - frequency of breathing (f)

– number of inspirations in quiet breathing (or expirations)

– usually expressed per minute: 10 – 18/min

(VT)

(f)

the volume of air moved into (or out of) the lungs per minute

in quiet breathing 5 – 9 l/ min

.

Vmin = f x VT

Page 40: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Maximum ventilation (Vmax) – the ventilated volume of air when an individual is

breathing as deeply and as quickly as possible (by maximum forceful respiratory effort)

• e.g. in physical activity

Vent max = frequency max x Volume max

Average values

- max frequency: 40 – 50/min.

- max volume: approx. 4500 ml

- respiratory rate

- (can increase by 30 times)

quiet

forceful

frequencymax

volumemax

.

Page 41: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

2. alveolar dead space

- involves alveoli where no gas exchange takes place

- in a healthy human:

- all alveoli serve for gas exchange

- alveolar dead space = 0

- in people with a lung disease - alveoli are malfunctioning

- alveolar dead space > 0 (problem in diffusion or perfusion of alveoli)

- parts of respiratory passageways where no significant gas exchange occurs

between lungs and blood

- the volume of the air in the dead space - VD

1. anatomical dead space – approx. 150 ml

= conductive part of airways

Total (physiological) dead space = anatomical dead space + alveolar dead space

Dead space

Page 42: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

• volume of air that reaches alveoli per minute (and serves for the gas exchange

between blood and alveoli)

• it can be calculated as:

alveolar ventilation = alveolar volume x frequency of breathing

= (tidal volume – dead space) x frequency of breathing

Example

tidal volume VT = 500 ml

frequency of breathing f = 12/min

dead space VD = 150 ml

minute ventilation Vmin = VT x f = 500 x 12 = 6000 ml/min

alveolar ventilation VA min = (500 – 150) x 12 = 4200 ml/min

1800 ml/min – remain in dead space

Alveolar ventilation (VA)

Page 43: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

- more air is supplied for gas exchange if the inspiratory volume is higher

(increase is less pronounced if the breathing rate gets higher)

VT /ml frequency min. ventilation/ml VD-dead space/ml alveolar ventilation/ml

500 12 6000 150x12=1800 350x12 = 4200

Ventilation can be increased by an increase of

- the inspiratory volume (deeper breathing)

- frequency of breathing (faster breathing)

- both frequency and volume

Question: Does it matter whether there is an

increase in frequency or inspiratory volume?

– alveolar ventilation depends on frequency of breathing and tidal volume

VT /ml frequency min. ventilation/ml VD-dead space/ml Alveolar ventilation/ml

1000 12 12 000 150 x 12=1800 10 200

500 24 12 000 150 x 24=3600 8 400

Page 44: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

• eupnea

- easy, free respiration, as is observed normally under resting conditions

- normal frequency 12-18/ min

- normal tidal volume 500 ml

Changes:

1. frequency of breathing

• tachypnea – increased frequency of breathing, rapid breathing

• bradypnea – decreased frequency of breathing, slow breathing

2. volume of an inspiration

• hyperpnea – an increase of tidal volume, deep breathing

• hypopnea – a decrease of tidal volume, shallow breathing

Ventilation and its changes

Page 45: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Hypoventilation

- lower ventilation that does not meet the metabolic needs

- CO2 production is higher than its elimination

- CO2 content in blood is increased – hypercapnia (pCO2 > 6,5 kPa)

- respiratory acidosis may occur

- in blood excess of acids

- pH of blood is lower than 7,36

Hyperventilation

- higher ventilation that exceeds the metabolic requirements

- CO2 is removed by lungs at higher than normal rates

- decrease of CO2 in blood – hypocapnia (pCO2 < 5 kPa)

- may result in respiratory alkalosis

- in blood excess of bases

- pH of blood exceeds 7,44

Page 46: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

• forced expiratory volume (FEV)

- maximal forced expiration after a maximal inspiration

(= forced expiration of vital capacity)

- normal duration: max 3 s

• forced expiratory volume per 1s (FEV 1)

- the volume expired in the first second of maximal expiration after a maximal inspiration

- normal value: 80 - 85% of VC

- FEV1 is the most frequently used index for assessing airway obstruction,

bronchoconstriction or bronchodilation

e.g. in asthma the FEV1 is lowered

Page 47: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

DIFFUSION OF GASES FROM ALVEOLI INTO BLOOD

Page 48: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Blood supply of the respiratory system

- function - pulmonary circulation

- nutrition - from systemic circulation

1. The pulmonary circulation

– right ventricle

– pulmonary artery

– alveolar capillary network

– pulmonary vein

– left atrium

• carries blood for oxygenation

= perfusion of alveoli

• rich capillary network surrounding alveoli – serves blood oxygenation

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Pulmonary circulation

Distribution of blood – not equal

1. influence of hydrostatic pressure– in vertical position - difference between the highest and the lowest

point 30 cm → corresponds to 23 mmHg

– apical parts - BP lower about 15 mmHg than in heart level

– heart level - BP lower about 8 mmHg than in lung bases

2. alveolar pressure– the highest in apical parts - higher than BP → blood flow during

systole only

– heart level - lower (+ higher hydrostatic pressure) - higher blood flow

– base of lungs - the lowest - lower than BP (systolic and diastolic) - all the capillaries are open

Ventilation-perfusion ratio• ideal = 1 (ventilation = perfusion), 0.8 acceptable

Page 50: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Blood supply of the respiratory system

2. The bronchial circulation

• a. bronchialis (branch of aorta) – carries oxygenated blood

• provides oxygen and nutrients to the respiratory passageways and lungs

Page 51: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

- the atmosphere exerts atmospheric pressure- pressure of individual gasses is proportional to their content (%)

Dalton's lawpartial pressure of a gas

= atmospheric pressure x percent of the gas

e.g. if the atmospheric pressure is 100 kPa

O2 content in atmosphere 21% partial pressure of O2 = 100 x 0,21=21 (kPa)

CO2 content in atmosphere 0,04 % partial pressure of CO2=100 x 0,0004=0,04 (kPa)

Partial pressures of the respiratory gases

N2 O2

Composition of atmosphere (inspired air):

N2 78 %

O2 21 %

CO2 0,04 %

H2O vapour 0,5% (non constant component)

atmosphere

CO2

Page 52: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Importance?

• physically dissolved respiratory gases in the blood exert partial pressure

Diffusion - in partial pressure gradient (pO2 and pCO2)

https://www.boundless.com/biology/textbooks/boundless-biology-textbook/the-respiratory-system-39/gas-exchange-across-respiratory-surfaces-220/basic-principles-of-gas-exchange-833-12078/

Page 53: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Composition of alveolar air

inspired air (= atmospheric) → alveoli

But, alveolar air does not have the same concentrations of gases as atmospheric air.

1. the inspired air is mixed with the air from previous expiration = the alveolar air is only partially replaced by atmospheric air with each breath

2. in alveoli - oxygen is constantly diffusing into the blood from the alveolar air + carbon dioxide is constantly diffusing from the blood into the alveoli

3. dry atmospheric air that enters the respiratory passages is humidified even before it reaches the alveoli

Page 54: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Composition of the expired air

alveoli → expired air

But, the composition is not equal:

• the expired air is mixed with the air from previous inspiration

• is changed during expiration

from: Guyton textbook of medical physiology

Page 55: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Atmospheric air

O2 - 21%

CO2 - 0.04%

Alveolus

O2 - 14% 13.3kPa

CO2 - 5.6% 5.3 kPa

Expiration

O2 - 16.3%

CO2 - 3.8%

venous blood in pulmonary artery

O2 - 5.3kPa

CO2 - 6.1 kPa

arterial blood in pulmonary veins

O2 - 12.6 kPa

CO2 - 5.3 kPa

Page 56: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Diffusion of gasses – depends on

1. the pressure gradient of the respiratory gasses (difference of partial pressures in the

blood and alveoli)

– O2: 13,3 – 5,3 =8 (kPa)

– CO2: 6,1 – 5,3 = 0,8 (kPa)

2. thickness of the respiratory

(alveolocapillary) membrane

(0,6 – 0,8 mm)

1. alveolar epithelium (+ surfactant)

2. basement membrane

3. capillary endothelial membrane

http://www.hakeem-sy.com/main/files/Respiratory-membrane--colored2_0.jpg

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Diffusion of gasses – depends on

3. diffusion area = the surface of the respiratory membrane (adults – 70 m2)

– decrease to 1/3 – gas exchange is impaired in rest

– exercise – even a small decrease can be detrimental

4. diffusion coefficient – depends on solubility and molecular weight of gas

– CO2 diffuses about 20 times as rapidly as O2

The respiratory membrane’s diffusing capacity

- is the volume of a gas that will diffuse through the membrane each minute for a

partial pressure difference of 1 mmHg (0,133 kPa)

= the ability of the respiratory membrane to exchange a gas between the alveoli

and the pulmonary blood

- it is affected by all factors mentioned above

- diffusing capacity for CO2 is 20x higher than for O2 (21 ml, 400 ml at rest)

Page 58: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Alveolar surface tensionSurfactant

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Alveoli - water / air interface

• inside - air

• outside – interstitial fluid and blood

• the water molecules on the surface of the water have a

strong attraction for one another (drop of water)

• as a result, the water surface tends to contract

• surface tension - force caused by water molecules on

air/water interface

• due to surface tension alveoli tend to collapse and to

force air out

http://www.sciencehq.com/chemistry/surface-tension.html

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Inspiration

• diameter of alveoli increases

Expiration

• diameter of alveoli decreases

i.e.

• Increased tendency of alveoli to collapse

• in case of a collapse a higher breathing effort

would be needed to expand the alveoli

Law of Laplace-the tendency of alveoli to collapse is

- directly related to the surface tension- inversely related to the alveolar diameter

-i.e.- objects with high surface tension and small diameter tend to collapse

P =____2T

r

P – collapsing pressure of alveolusT – surface tensionr – diameter of alveoli

http://clinicalgate.com/surfactant-agents/

Page 61: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

• a substance that covers alveoli in thin monolayer

• reduces surface tension

• prevents collapse of alveoli

• produced and re-uptaken by type II pneumocytes

• a complex mixture of lipids and protein

(mainly dipalmitoylphosphatidylcholine)

Surfactant

http://casopis.vesmir.cz/files/obr/nazev/1996_630_03/type/html

Page 62: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Inspiration

• diameter of alveoli increases

• molecules of surfactant get more apart

• surface tension increases

Expiration

• diameter of alveoli increases

• molecules of surfactant get closer to

each other

• surface tension decreases

- decreased diameter of the alveoli (expiration)

- more molecules of surfactant / surface area

- more powerful effect of surfactant,

- i.e. lower surface tension,

- i.e. lower tendency to collapse

Page 63: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Effects of surfactant

1. alveoli do not collapse in expiration

2. this reduces the effort required by the respiratory muscles to expand the lungs

3. smaller alveoli do not empty into larger one

Page 64: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Expansion of lungs at birth

• at birth – alveoli are kept collapsed and are filled by the amniotic fluid

• the first breath of a newborn: 3-7 kPa of negative inspiratory pressure (in normal breathing:

-1,0 kPa) is required to open the alveoli and inflate the

• the surfactant becomes spread in alveoli after the 1st breath

• once the alveoli are open, further respiration is effected with relatively weak changes in

intrapleural pressure (normal values)

Respiratory distress syndrome (RDS)

• a condition when lungs of a newborn baby tend to collapse after each expiration

• extreme effort is required for inspiration

• often due to insufficient surfactant production

• mostly a problem of pre-term babies

- production of surfactant starts in last 1-3 months of gestation

- if there is risk of preterm birth, the mother is treated with corticoids that trigger production of

surfactant

Page 65: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Lung compliance

• the extent to which the lungs will expand for each

unit increase in pressure

= how easy it is to inflate the lungs

• normal values + 0,1 kPa → + 200 ml

http://web.carteret.edu/keoughp/LFreshwater/CPAP/Ventilation/ventilation_class_notes.htm

Page 66: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Lung compliance

• depends on:

– elasticity of lung tissue (the ability of the lung to recoil after it has been inflated) –

inverse relation

• normal lungs: balance between compliance and elasticity

– higher – e.g. in emphysema – loss of alveoli

(loss of tissue) - results in difficulty to resume the shape of the lung during

expiration

– lowered – e.g. in fibrosis – stiffness of the lung - results in difficulty to expand

the lung during inspiration

http://web.carteret.edu/keoughp/LFreshwater/CPAP/Ventilation/ventilation_class_notes.htm

Page 67: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Static compliance

• the curve of relaxation pressures

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Dynamic compliance

Page 69: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

TRANSPORT OF O2 IN THE BLOOD

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1/ Physically dissolved O2

• the amount depends on the partial pressure of O2 in lungs

• 3 ml /l of blood – under normal pressure conditions

(more in hyperbaric chambers)– Henry's law - the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid

• it exerts the partial pressure of O2 in blood

2/ Chemically bound O2

• bound to haemoglobin (oxygenated Hb) – attached to Fe2+

• fully saturated 1 g hemoglobin – carries 1,34 mL O2 (Hüfner number)

• oxygen-carrying capacity (ml O2/l blood) = Hüfner number x Hb concentration (g/l)

Oxygen haemoglobin saturation = % of oxygenated Hb from total Hb

Normal values

1. arterial blood 97-100% (95%)

2. venous blood 75%

Page 71: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

▪ amount (%) of oxygen attached to hemoglobin

(saturation of Hb) depends on the partial

pressure of oxygen

Oxygen – hemoglobin

association-dissociation curve

(O2 equilibrium curve)

▪ relates oxygen partial pressure in blood and

hemoglobin saturation

▪ the higher pO2, the more O2 is bound to Hb

▪ the curve has sigmoidal shape

▪ at the beginning –slow increase (the first

molecule of O2 binds with difficulties, later

change in spatial conformation of Hb - easier

combination)

▪ then sharp increase - i.e. in rather low pO2 is

blood relatively well saturated with O2

Oxygen equilibrium curve

Page 72: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

- flat in higher pO2, i.e. rather high saturation within a broad range of pressures

Normal values

▪ arterial blood (A)

▪ pO2 12-13,3 kPa (90-100 mm Hg)

▪ saturation 95% (100%)

▪ venous blood (V)

▪ pO2 5,3 kPa (40 mm Hg)

▪ saturation 75%

▪ arteriovenous (AV) difference – ca.20%

▪ during physical activity▪ increase in AV difference – up to 50%

▪ high altitudes

▪ low pO2

▪ 6 000 m: 4,5 kPa = 34 mm Hg

▪ therefore lower Hb saturation

▪ as a compensation the Er count is rising

http://www.physiologyweb.com/figures/physiology_graph_sLCVoxW1Ww7uMYapMyDLnHYZN5gCKV8v_oxyhemoglobin_dissociation_curve.html

Page 73: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Factors that affect combination of O2 and Hb

i.e. affect the affinity of Hb to O2

i.e. affect the oxygen equilibrium curve:

1. pCO2

2. pH

3. temperature

4. content of 2,3 biphosphoglycerate in Ery(2,3-BPG – product of Ery metabolism)

Oxygen equilibrium curve

effect of pH changes

Affinity of Hb to O2 is decreased

=O2 is more easily released from the bound to Hb

pCO2*

pH

temperature

2,3 DPG

= shift to right and down (e.g. in tissues)

Affinity of Hb to O2 is increased

= O2 is released from bound with Hb less easily

pCO2

pH

temperature

2,3 DPG

= shift to left and up (e.g. in the lungs)

* Bohr effect: increasing concentration of CO2 reduces the oxygen affinity of Hb

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Page 75: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

TRANSPORT OF CO2 IN THE BLOOD

Page 76: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

CO2 - main product of metabolism (98%)

- diffuses from tissues into blood, then transported as:

1. Physically dissolved CO2

- arterial blood 30 ml, venous 35 ml/L (5 %)

2. Chemically bound (15-20 %)

- to hemoglobin – carbaminohemoglobin

- to plasma proteins - carbaminoproteins

- CO2 bound to hemoglobin – decreases the affinity to O2 (Bohr effect)

- and vice versa – Haldane effect

- lungs: more O2 lowers the affinity for CO2 (which is released)

- tissues - CO2 produced in tissues binds to hemoglobin – decreases affinity

for O2 (released from hemoglobin)

Page 77: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

3. Bicarbonate ions (75-80 %)

- after diffusion into erythrocytes CO2 reacts with water

CO2 + H2O → H2CO3 → H+

+ HCO3-

(catalysed by bicarbonate dehydratase)

- H+

is bound by Hb (Hb buffer)

- HCO3-

diffuses into plasma (and functions as a part of bicarbonate buffer)

(and Cl -from plasma enters erythrocytes, this ion change is referred to as = Hamburger effect)

- in lung the reactions occurs in reverse order

Page 78: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

The CO2 equilibrium curve

• shows the dependence of total blood CO2 in

all forms and pCO2

- the higher the blood partial pressure of CO2,

the more CO2 is transported

• CO2 is in an inverse association with pO2:

• less O2 allows more CO2 to load (in tissues)

Normal values of pCO2

normocapnia - arterial blood – 5,3 kPa (40 mm Hg)

- venous blood – 6,1 kPa (45 mm Hg)

hypercapnia – increase of pCO2

hypocapnia – decrease of pCO2

hyperventilation - excessive ventilation causing of pCO2 and of pO2

hypoventilation - excessive ventilation causing of pCO2 and of pO2

- binding of O2 to hemoglobin tends to displace CO2 from the blood into alveoli

(Haldane effect)

- more O2 shifts the curve downwards and to the right

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REGULATION OF BREATHING

= REGULATION OF VENTILATION

Page 80: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

➢ Ultimate goal of respiration

– to maintain proper concentrations of oxygen, carbon dioxide, and hydrogen ions in the tissue

• adequate ventilation in minimal possible energy consumption

+ ventilation must be adjusted to perfussion

➢ Modulated parameters:

mechanics of breathing + aerodynamics

➢ Components of regulation:

➢ frequency and depth of breathing, reflexes, voluntaryventilation

➢ final efectors: respiratory muscles

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Regulation of respiration – the respiratory centre

medulla oblongata and pons – the respiratory center

reciprocal inhibition

expiratory neurons

(ventral respiratory group)

1. inhibit inspiratory neurons

2. cause active expiration

inspiratory neurons

(dorsal and ventral respiratory group)

- their stimulation causes inspiration

- generator of respiratory activity

pneumotaxic centre

-inhibits the apneustic centre (switches-off inspiration)

- affects duration of the inspiration

apneustic centre – stimulates inspiratory neurons

- bursts of action potentials in the respiratory centre

- travel to the respiratory muscles and cause their contraction

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Activity of respiratory centre is influenced by

pneumotaxic centre

apneustic centre

respiratory centre

expiratory neuronsinspiratory neurons

cortex (voluntary control of breathing)

subcortical structures (limbic system -

emotions, hypothalamus - temperature)

receptors in respiratory

passageways

(mechano, thermo, chemo)

peripheral and central

chemoreceptors

other

receptors

spinal

cord

respiratory

muscleslung stretch

receptors

muscle spindles

Page 83: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Chemical regulation of respiration

• active already under conditions of normal pO2 a pCO2 (generate action potentials)

• hypoxia and hypercapnia increase stimulation of the receptors that subsequently

stimulate inspiration centre

(via vagus and glossopharyngeus nerves)

• more pronounced stimulation if both hypoxia and hypercapnia occurs

Peripheral chemoreceptors= small islets of sensory cells in

• aorta – glomus aorticum (aortal bodies)• a. carotis – glomus caroticum (carotid bodies)

- well perfused, sensitive to pO2 (! the only O2

sensing locality) and pCO2

Page 84: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

K-channels sensitive to O2

- In the presence of O2 –channels openned –hyperpolarisation

- ↓ in O2 – channels closed –stop of K+ outflow -depolarization

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Central chemoreceptors

• ventral part of medulla oblongata

• sensitive to changes of H+ concentration

in cerebrospinal fluid

• H+ from blood cannot pass BBB

• CO2 diffuses from blood to cerebrospinal fluid freely and reacts with water

CO2 + H2O → H2CO3 → H+

+ HCO3-

• central chemoreceptors

– indirect and delayed effect (after 20-30 s)

– more powerful than peripheral chemoreceptors (80% of response)

• in very high concentrations of CO2 in inspired air, CO2 has inhibitory effect –decrease of ventilation – death may occur

Page 86: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Stretch receptors in the lungs

• mechanoreceptors – sensitive to stretching, speed of air, etc.

The Hering Breuer reflexes

• Inflation reflex

– passive inflation of air into the lungs – inhibits ventilation

– a reflex triggered to prevent overinflation of the lungs

– inflation stimulates the lung – inflation receptors

– their activity increases (more frequent action potentials that travel via n. vagus to the inspiratory neurons in respiratory center)

– if lung inflation is large - the inspiratory neurons are inhibited (reflex)

– inspiratory muscles relax - expiration starts

• Deflation reflex

– passive deflation of air from the lungs – stimulates inspiration

Page 87: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Voluntary regulation of respiration

• frequency and depth of breathing – can be voluntarily regulated

(action potential travels by tr. corticospinalis, involuntary breathing – tr.

bulbospinalis)

• voluntary apnoea – is eventually broken by autonomous regulatory

mechanism, that stimulate inspiration (chemoreceptors)

• breaking point

– hypoxia pO2 9,3 kPa (in arterial blood)

– hypercapnia pCO2 6,6 kPa (in arterial blood)

Central hypoventilation syndrome = Ondine´s curse

-congenital (acquired) respiratory disorder of automatic breathing

-patient can breathe only voluntarily

-problems during sleep – tracheotomy, mechanical ventilation

Page 88: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Respiration in high altitudes

• high altitudes

• aviation

Page 89: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

• with increasing altitude

– atmospheric pressure decreases (not %O2)

– significantly decreases pO2

(atmosph., alveoli, blood)

altitude

(m)

atm. pressure

(mm Hg)

pO2 saturation

(art. blood)

0 760 159 97%

3 300 524 110 90%

6 600 349 73 73%

9 900 225 47 24%

13 200 141 29

16 600 87 18

Page 90: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Acute hypoxia (mountain sickness)

- mainly in not acclimatized people

- 2500 m – first symptoms (10-25% people)

- deeper breathing

- tachycardia

- 3000 - 4000 m (4500 - 50-85%)

- hypocapnia, alcalosis due to hyperventilation

- mental and physical fatigue

- headache, nausea

- euphoria, decreased judgement, memory

- impaired sensory perception

- impaired discrete motor movements

- pulmonary oedema

- 5 500 m – cramps

- 7 000 m – coma, death

Page 91: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Acclimatization to low p02 (after 2-3 weeks)

• increased lung ventilation

– pO2 – stimulates the peripheral chemoreceeptors

– increase of ventilation

– subsequently pCO2 – respiratory alkalosis

– subsequently – an increase in bicarbonate excretion by kidney

– balance of pH reestablished

• increased erythrocyte count

– haemoglobin – increase to 200 g/l

– increased total blood volume by 20-30 %

(thus also the ability to transport O2)

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• increased erythrocyte count

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The other compensatory mechanisms

1. increase of 2,3 DPG in erythrocytes

– decrease of Hb affinity to oxygen

2. increase in diffusion capacity of the lungs (approx. 3x)

– increased blood flow through capillaries

– expansion of the capillaries

– due to increased inspiratory volume – alveoli expand more in inspiration

– result: larger surface area for gas exchange

3. improved blood flow in peripheral tissues

4. growth of increased numbers of systemic circulatory capillaries

– in the non-pulmonary tissues – angiogenesis

– mainly in active tissues (muscle)

5. cellular acclimatization

• better ability to utilize O2 despite decreased pO2

• the count of mitochondria grows

• increases concentration of enzymes for oxidative reactions

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RESPIRATION UNDER WATER

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Low depths• usage of snorkel - tube maximally 35 cm long, inner diameter

up to 2 cm (smaller diameter - increase in resistance to airflow → increases the work of breathing)

• increase of VD

Deep diving

1. Increased pressure acts on the chest

2. Compression of inspired gases

3. Effect of high partial pressures of individual gasses on the body

4. Decompression sickness

Page 96: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

1. Increased pressure acts on the chest

• atmospheric pressure (0 m) 760 mm Hg ( cca 100 kPa)

• column of seawater 10 m thick

– exerts hydrostatic pressure + 760 mm Hg (+ 100 kPa)

-descend beneath the sea - the pressure around considerably increases

-to keep the lungs from collapsing - air must be supplied at very high pressure to keep them inflated

Page 97: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

2. Compression of inspired gases

• Boyle´s law: pressure x volume of gasses = constant

• if the pressure increases, the volume decreases

• inspired air is denser

• higher density of the inspired air – higher resistance in airways – high

effort in breathing

• compression of the atmospheric air is inappropriate for breathing - we

need another mixture of gases

Page 98: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

3. Effect of high partial pressures of individual gasses on the body

Nitrogen

• under normal atmospheric pressure – no effects on the human body (about 1 L is dissolved in the body)

• under high pressure – narcotic effect (at 40 m approx. in 1 h)

– similar to the effects of alcohol

– loss of judgement

• 50-60 m: tiredness

• 60-80 m: impaired motor abilities

• more than 80 m: significant deficit of mental and physical abilities

• mechanism of the narcotic effect of nitrogen

– nitrogen is dissolved in fat (membranes, nerves)

– causes abnormal ion conductivity

– decrease in nerve excitability

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Oxygen• major increase in the content of physically dissolved O2 in blood

• tissues are exposed to extremely high pO2

• oxygen „intoxication“ – nausea

– muscle twitching

– abnormalities of vision, disorientation

– seizures, coma (in 30-60 min)

faster in physical activity

• mechanism of the adverse oxygen effects

– increased production of free oxygen radicals (superoxide, hydroxyl)

– increased oxidation of membrane lipids

– oxidation of intracellular enzymes – metabolic abnormalities

Page 100: Physiology of respiration - zona.fmed.uniba.sk€¦ · Physiology of respiration Respiration – principal and vital function of the respiratory system • external respiration –exchange

Carbon dioxide

• diving in depth does not increase pCO2 the in alveoli

• if CO2 is expired into water – no problems occur

• closed system (re-breathing apparatus)

– progressive increase in CO2 content of the inspired air

– at the beginning – stimulatory effect – increased ventilation

– later – suppressed ventilation

– lethargy, narcosis, loss of consciousness

• mechanism of the carbon dioxide effect

– pCO2 over 80 mm Hg – supression of the respiratory centre

– respiratory acidosis – malfunction of the enzymes

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4. Decompression sickness

• if a diver has been beneath the sea long enough - large amounts of nitrogen (mainly,

but not exclusively) are dissolved in the body water and in the fat

• when the diver suddenly comes back to the surface of the sea, significant quantities of

nitrogen bubbles can develop in the body (inside the cells, in extracellular space)

• can damage in almost any area of the body

• first, only the smallest vessels are blocked by

minute bubbles

• but as the bubbles coalesce, progressively larger

vessels are affected

• Boyle’s law - increase in volume of the air in

alveoli - rupture of the lungs - gas embolism

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• symptoms

– pain in the joints – arms, legs

– nausea, paralysis, loss of consciousness

– embolia of a.pulmonalis: lung oedema, dyspnoea, death

-e.g. Buhlmann tables ZH-L12 -depth 36 m, duration of diving 30 min - decompression9 m – 2 min6m – 5 min3 m – 15 min

Decompression tables

Tank decompression

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• tanks with compressed air or breathing mixture

– first stage valve – gas of reduced pressure leaves to

the mask

– demand valve – the demanded volume is released

into the mask

• exhalation into the sea

Helium-Oxygen Mixtures in Deep Dives

-helium replaces nitrogen

-lower narcotic effect

-lower solubility in tissues

-lower density – lower resistance in respiratory passageways

-low O2 content (1%)

-suffcient to supply tissues

-prevents seisures

SCUBA diving

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Other functions of the respiratory system

1. Vocalization - larynx = „voice box“

– air moving across vocal cords createsvibrations - speech, laughing, shouting (communication, emotions)

2. Protective function

• prevents foreign material (microbes, dustparticles, etc.) to enter the body through mucosal lining of the respiratory tract

• (e.g. by the ciliary activity, immune cells and molecules)

http://choirly.com/wp-content/uploads/2012/03/vocal-folds.jpg

http://media.gettyimages.com/photos/vocal-cords-the-intensity-of-

voice-sound-depends-on-the-pressure-of-picture-id541323641

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3. Maintenance of the acid-base balance • i.e. maintenance of constant pH 7,4 in the body

• by the rate of CO2 removal from the body via the expired air

• (acid base balance is maintained also by the kidney and blood buffer systems)

4. Water Balance• the inhaled air is saturated with water; the water is lost on exhalation

• a minor pathway of water loss in humans

5. Heat Balance• respiration - minor pathway of heat loss in humans

http://i.cbc.ca/1.1549934.1418313236!/httpImage/image.jpg_gen/derivatives/16x9_1180/hi-cold-

breath-03881746.jpg

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Disorders of the respiratory system

- results of functional lung examination help in diagnosis of:

1. Restrictive lung diseases

• increased lung stiffness

• causing incomplete lung expansion

• volumes are lower

• e.g., fibrosis, alveolar damage, pleural effusion

2. Obstructive lung disorders

• diseases of the lung where the bronchial tubes become narrowed

• making it hard to move air in and especially out of the lung

• prolonged expiration, lower ERV

• normal lung capacity

• e.g. asthma attacks, emphysema, bronchitis