The respiratory system - uniba.sk...The respiratory system Practical 1 Objectives Respiration, ventilation Intrapleural and intrapulmonary pressure Mechanism of inspiration and expiration

The respiratory system

Practical 1

Objectives

Respiration, ventilation

Intrapleural and intrapulmonary pressure

Mechanism of inspiration and expiration

Composition of the atmosphere and the expired air

Practical tasks

1. Hering´s model of the respiratory system

2. Paralellogram

3. Measurement of the vital capacity

4. Analysis of respiratory gases in exhaled air

5. Measurement of the expiratory peak flow with a peak

flow meter Vitalograph

© Katarína Babinská MD, PhD, MSc, 2017

Respiration – vital function

Respiration - exchange of the respiratory gasses

- the principal function of the respiratory system

⚫ supplying of O2 from atmospheric air for metabolism

⚫ removing excess CO2 (metabolic end-product) from the body

external respiration: exchange of gases between atmosphere and alveoli

internal respiration: exchange of gases between blood and cells of the body

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

atmosphere cells

- a rhythmic, automatic process (breathing cycle)

• inspiration

• air moves from the atmosphere into the lungs

• tidal volume VT – 500 ml (quiet breathing)

• expiration

• the same volume 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 driven by the pressure differences

between the lungs and the atmosphere

Ventilation (Breathing)

© Katarína Babinská, MD, PhD. MSc., 2010

Atmospheric pressureatmosphere

the atmosphere (mass of air) exerts pressure

- 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 atmosperic 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

• lungs – lined with a thin membrane

pleura visceralis

• the internal side of the chest is lined with

pleura parietalis

• between both membranes is a thin space

- (intra)pleural space

• the space is filled with small volume of liquid

that surrounds the lungs


Pleura, (intra)pleural space

Intrapleural pressure - the pressure(of the liquid) in intrapleural space

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 pressure

prevents the lung to collapse

is effective in inspiration and expiration

intrapleural space –

negative pressure


visceral

pleura

parietal

pleura

Intrapulmonary (alveolar) pressure

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

- when the glottis is open and no air flows into/out of the respiratory

passageways, the pressures in all parts of the respiratory tree are equal to

the atmospheric pressure


Physical laws in respiration

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

Dalton's law

Forceful breathing

- e.g. in stress, physical activity

Quiet breathing

- in rest

1. Contraction of the inspiratory

muscles

= an active process

A. diaphragm – the main inspiratory muscle

- quiet breathing – by contraction it descends by 1-1,5 cm

- in forceful breathing – by a stronger contraction it descends by 6 -10 cm,

B. external intercostal muscles

- pull ribs up and out

- cause further increase in chest volume

C. accessory inspiratory muscles – active in forceful breathing

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

Before the inspiration Inspiration

Mechanism of inspiration


2. increase in chest volume

- by 0,5 L in quiet breathing,

(forceful breathing by 2-3 L)

3. decrease of intrapleural pressure

- becomes more negative

- parietal pleura follows the chest

movement, thus volume of pleural cavity , intrapleural pressure

4. decrease in intrapulmonary pressure

- before inspiration: pressure in lungs = pressure in atmosphere

- the increased negativity of intrapleural space

„pulls the lungs outwards“ therefore, lung expand

- during lung expansion – alveolar pressure becomes 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


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. intrapleural pressure increases (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


Expiration

• in forceful breathing – active

(requires muscle contraction)

• involves:

Expiratory muscles- contraction

1. internal intercostal muscles

- move ribs downwards

- further decrease in thoracic volume

2. accessory expiratory muscles – abdominal muscles

expiration


intrapleural space –

negative pressure

after exspiration / prior to next inspiration

- two recoil forces are in equilibrium( )

= relaxation position of the chest

- position whan the respiratory muscles

(inspiratory and expiratory) are relaxed

- optimum starting position for breathing –

least work of respiratory muscles

Inspiration

- starting from relaxation position is active

- activity=contraction of inspiratory muscles

Expiration

- above relaxation position is passive (quiet expiration)

- 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

relaxation

position –

respiratory

muscles are

relaxed

Non-relaxation positions

1. inspiratory position

- during inspiration, when inspiratory

muscles are contracted

2. expiratory position

- during forceful expiration when

expiratory muscles are contracted

- inspiratory and expiratory position are

a result of respiratory muscle activity

(contraction)

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 ofthe intrapulmonary pressure

b) later during inspiration - air moves into the lungs – pressureprogressively 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 – progressivedecrease pressure (from positive values to zero value)

Volume of air in the lungs

- increase during inspiration, decrease during expiration

inspiration exspiration

ab

c

d

Inspiration

- starting from relaxation position is active

- activity=contraction of inspiratory muscles

Expiration

- above relaxation position is passive (quiet expiration)

- 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

relaxation

position

Relaxation position of the chest

- respiratory muscles (inspiratory and expiratory) are relaxed

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

Task 1. The Hering´s model of respiratory system

Hering´s model

a glass bell represents the chest, the bottom is made of rubber

and it imitates the diaphragm

shows the function of diaphragm in breathing

Principle

pull down or push up the bottom of

Hering´s model, observe and

explain changes in pleural space,

lung and vena cava


Procedure

Diaphragm – pulling down („inspiration“)

volume of the thoracic cavity is increasing

pressure in the pleural space is decreasing

pressure in alveoli (lung) is decreasing from atmospheric level

air moves from the atmosphere into the lungs

v. cava expands

Diaphragm – pushing up („expiration“)

volume of the thoracic cavity is decreasing

pressure in the pleural space is increasing

pressure in alveoli is increasing – exceeds the atmospheric

pressure

air is moving from the lungs into the atmosphere

blood flow in v. cava is decreased


Valsalva manoeuvre

a forcible expiration against closed airways (nose, mouth)

a major increase in pleural pressure (that may get even positive)

it helps to normalize the middle ear pressure

it is used in some clinical examinations

Műller´s manoeuvre

after a forced expiration an attempt of deep inspiration with closed

airways (nose, mouth)

a major decrease in pleural pressure

the manoeuvre is used in some clinical examinations of respiratory tract

Result and conclusion: describe the observation


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

Task 2. Parallelogram – a model of intercostal muscles

Principle

imitate the contraction of mm. intercostales interni and externi

and observe movements of the ribs

sternum

ribs

backbone

miemii


Procedure

Modelling the inspiratory movement

inspiration - contraction of m. intercostales externi

contract the rubber that is directed obliquely downward and medially

immitate both quiet and forceful inpiration

Modelling the expiratory movement

immitate both A/ quiet and B/ forceful expiration

⚫ A/ relaxation of the inspiratory muscles

⚫ B/ contraction of the m. intercostales interni (they are directed obliquely

downward and laterally)

Result and conclusion: describe the observation


Task 3. Measurement of the vital capacity


VC

vital capacity (VC)

- The volume of maximum forceful expiration that follows previous maximum inspiration

Procedure

close the nose with a clamp

insert a disinfected mouthpiece into the rubber tube

make maximum inspiration

make maximum expiration – exhale into the

spirometer

a spirometer – a metal jar with a smaller jar inside

the internal jar is pushed up by the expired air

read the volume of the expired air on the scale

repeat the measurement of VC 3 times

calculate the average of your measurements

1000

2000


Procedure

make the BTPS correction

VC BTPS= VC x BTPS factor (find in tables)

BTPS correction = recalculation for standard body conditions

⚫ temperature – 37 °C

⚫ barometric pressure – 101.3 kPa

⚫ water vapour saturation – 6.3 kPa

Calculate the normal value of vital capacity: VCphys

Men: VCphys = 5,76 x H – 0,026 x A - 4.34

Women: VCphys = 4,43 x H – 0,026 x A - 2.89

H = height in m A = age in years

is your VC BTPS in the range of 90 – 110 % of the VC phys?

% VC = VC(BTPS) x 100/VCphys


Respiratory passageways

A/ Conducting zone

upper respiratory tract (passageways)

⚫ nasal cavity, nasopharynx, larynx

lower respiratory tract

⚫ trachea, bronchi, bronchioles (most)

B/ Respiratory zone (gas exchange)

lower respiratory tract

⚫ respiratory bronchioles

⚫ alveolar ducts

⚫ alveolar saccules

⚫ alveoli

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 (e.g. in pneumonia, fibrosis)

- parts of respiratory passageways where no significant

gas exchange occurs between lungs and blood

1. anatomical dead space – approx 150 ml

= conductive part of airways

- function: the inspired air is heated, cleaned, moisturized

Physiological dead space = anatomical dead space + alveolar dead space

Dead space (VD)

- alveolar dead space

- pneumonia, x- ray exam

- lungs are blocked with

fluid and bacteria

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

partial 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 atmosph. 0,04 % partial pressure of CO2=100 x 0,0004=0,04 (kPa)

- gasses dissolved in fluids also exert partial pressures

Partial pressures of O2, CO2

- diffusion O2 and CO2 from lungs into blood is based on differences in pO2, pCO2

Composition of atmosphere (inspired air):

N2 78 %

O2 21 %

CO2 0,04 %

H2O vapour 0,5% (non constant component)

N2 O2

atmosphere

CO2

inspiration(atmospheric air)

O2 21%

CO2 0,04%

expiration

O2 16,3%

CO2 3,8%

alveoli*

O2 14% 13,3 kPa

CO2 5,6% 5,3 kPa

pO2 5,3 kPa

pCO2 6,1 kPa

pO2 12,6 kPa

pCO2 5,3 kPa

the inspired air is mixed with the air

from previous expiration

the expired air is mixed with the air

from previous inspiration

* in alveoli O2 is

instantly diffusing into

blood and CO2 from

blood, therefore their

% differ from % in

inspired and expired

air

rection of

blood flow

Task: Analysis of the respiratory gases

gas analyzer SPIROLYT is used

the analyzer continuously measures and records atmospheric

⚫ concentration of O2

⚫ concentration of CO2

since composition of atmosphere is constant straight (zero) lines are

recorded on a sheet of paper (blue for CO2, red for O2 )

Task: Into a sampler (balloon) collect a sample of expired air from

the beginning of expiration

the end of expiration

and analyze the O2 and CO2 content

O2CO2

Analysis of the expired air:

attach the sampler to the SPIROLYT analyzer

observe the blue and red lines

if the blue and red lines move upwards = a change in O2 a CO2 is detected

proceed with the measurement until a „new“ straight line is recorded again

distance between lines = difference in O2 a CO2 % between the sample and

atmosphere

read the results by using a ruler (blue for CO2, red O2 )

DO2DCO2

Result: calculate the % O2 and CO2 in the sample

%O2 = decrease in O2 in the sample in contrast to atmospheric air

O2 in expired air = O2 in atmospheric air - DO2

% CO2 = increase in CO2 in the sample in contrast to atmospheric air

CO2 in expired air = CO2 in atmospheric air + DCO2

Conclusion: is the result normal? Explain

DO2DCO2

Task: Measurement of the expiratory peak

flow with a peak flow meter

Forced expiratory volume (FEV) measures how much air a person can exhale

during a forced breath. The amount of air exhaled may be measured during the

first (FEV1), second (FEV2), and/or third seconds (FEV3) of the forced breath.

- FEV1 normal value: 80 - 85% of VC

- FEV 3: normal value 97-100 % of VC

The peak air flow

It measures the fastest rate of air (airflow) that a person can blow out of lungs.

(airflow in litres per minute - L/min).

Procedure

Put the marker to zero.

Take a deep breath.

Seal your lips around the

mouthpiece.

Blow as hard and as fast as you

can into the device.

Note the reading.

Repeat three times.

The 'best of the three' is the

reading to record on the chart.

Normal peak flow

readings vary,

depending on

⚫ Age

⚫ Body size

⚫ Gender

The range of

normal peak flow

readings is

published on a

chart

Measurement of peak flow

- often used in asthma

- regular readings can be used to help

assess how well treatment is working.

- readings improve if narrowed airways

open up with treatment.

Air flow in the respiratory passageways

air flow through the respiratory passageways depends on their diameter

Normal breathing

Inspiration - bronchi dilated and prolonged „easier air flow

Expiration - bronchi narrower and shorter „more difficult“

expiration normally longer 2:1

in disease (e.g. asthma, bronchitis, etc.)

the air flow may be limited by

⚫ Bronchocinstriction (contraction of the

smooth muscle in the wall of bronchi –

mainly smaller bronchi and bronchioles)

⚫ Inflammed and swollen mucosa

⚫ Presence of mucus

Documents

The respiratory system - uniba.sk...The respiratory system Practical 1 Objectives Respiration, ventilation Intrapleural and intrapulmonary pressure Mechanism of inspiration and expiration