The respiratory system

Transcription

1 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

2 Respiration vital function

3 Respiration - exchange of the respiratory gasses - the principal function of the respiratory system supplying of O 2 from atmospheric air for metabolism removing excess CO 2 (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 O 2 / production of CO 2 in the cell metabolism atmosphere cells

4 Breathing - a rhythmic, automatic process (breathing cycle) inspiration air moves from the atmosphere into the lungs tidal volume V T 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 Katarína Babinská, MD, PhD. MSc., 2010

5 Atmospheric pressure atmosphere 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, ite means, it is by +0,1 kpa higher than atmospheric pressure

6 Pleura, (intra)pleural space 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 Katarína Babinská, MD, PhD. MSc., 2010

7 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 0,25 to 1,1 kpa in quiet breathing The negative pressure prevents the lung to collapse intrapleural space negative pressure is effective in inspiration and expiration Katarína Babinská, MD, PhD. MSc., 2010

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

9 Physical laws in respiration Dalton's law 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 P 1 p 2 P 1 > p 2 Boyle's law pressure and volume of air within a closed system is constant i.e. if the volume increases, the pressure decreases and vice versa V p V p

10 Quiet breathing - in rest Forceful breathing - in stress, physical activity

11 Mechanism of inspiration 1. Contraction of the inspiratory muscles = an active process Before the inspiration Inspiration 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.) Katarína Babinská, MD, PhD. MSc., 2010

12 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 - the negativity pulls the lungs outwards therefore, lung expand Before inspiration inspiration 4. decrease in intrapulmonary pressure - before inspiration: pressure in lung = pressure in atmosphere - during lung expansion 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) Katarína Babinská, MD, PhD. MSc., 2010

13 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 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 - expiration is terminated when the pressures in lungs/atmosphere are equal Katarína Babinská, MD, PhD. MSc., 2010

14 Expiration in forceful breathing active (requires muscle contraction) expiration involves: Expiratory muscles- contraction 1. internal intercostal muscles - move ribs downwards - further decrease in thoracic volume 2. accessory expiratory muscles abdominal muscles Katarína Babinská, MD, PhD. MSc., 2010

15 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 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) beginning of inspiration b a beginning of expiration d c 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) 0,5 inspiration exspiration Volume of air in the lungs - increase during inspiration, decrease during expiration 0

16 relaxation position respiratory muscles are relaxed 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

17 Intrapleural pressure the pressure(of the liquid) in intrapleural space lungs - exert an elastic recoil directed inwards thorax - exerts an elastic recoil directed outwards 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 intrapleural space negative pressure

18 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)

19 Relaxation position of the chest - respiratory muscles (inspiratory and expiratory) are relaxed -volume in the lungs = functional residual capacity (FRC=ERV+RV) relaxation position 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

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

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

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

23 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

24 Task 2. Parallelogram a model of intercostal muscles Principle imitate the contraction of mm. intercostales interni and externi and observe movements of the ribs ribs sternum mii mie backbone Katarína Babinská, MD, PhD. MSc., 2010

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

26 vital capacity (VC) Task 3. Measurement of the vital capacity - The volume of maximum forceful expiration that follows previous maximum inspiration VC Katarína Babinská, MD, PhD. MSc., 2010

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

28 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 kpa water vapour saturation 6.3 kpa Calculate the normal value of vital capacity: VC phys Men: VC phys = 5,76 x H 0,026 x A Women: VC phys = 4,43 x H 0,026 x A H = height in m A = age in years is your VC BTPS in the range of % of the VC phys? % VC = VC (BTPS) x 100/VC phys Katarína Babinská, MD, PhD. MSc., 2010

29 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

30 Dead space (V D ) - 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 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 - alveolar dead space - pneumonia, x- ray exam - lungs are blocked with fluid and bacteria - in people with a lung disease - alveoli are malfunctioning - alveolar dead space > 0 (e.g. in pneumonia, fibrosis) Physiological dead space = anatomical dead space + alveolar dead space

31 Partial pressures of O 2, CO 2 atmosphere CO 2 Composition of atmosphere (inspired air): N 2 78 % O 2 21 % CO 2 0,04 % H 2 O vapour 0,5% (non constant component) N 2 O 2 - 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 O 2 content in atmosphere 21% partial pressure of O 2 = 100 x 0,21=21 (kpa) CO 2 content in atmosph. 0,04 % - gasses dissolved in fluids also exert partial pressures partial pressure of CO 2 =100 x 0,0004=0,04 (kpa) - diffusion O 2 and CO 2 from lungs into blood is based on differences in po 2, pco 2

32 inspiration (atmospheric air) O 2 21% CO 2 0,04% the inspired air is mixed with the air from previous expiration expiration O 2 16,3% CO 2 3,8% the expired air is mixed with the air from previous inspiration po 2 5,3 kpa pco 2 6,1 kpa po 2 12,6 kpa pco 2 5,3 kpa rection of blood flow alveoli* O 2 14% 13,3 kpa CO 2 5,6% 5,3 kpa * in alveoli O 2 is instantly diffusing into blood and CO 2 from blood, therefore their % differ from % in inspired and expired air

33 Task: Analysis of the respiratory gases

34 Task: Into a sampler (balloon) collect a sample of expired air from the beginning of expiration the end of expiration and analyze the O 2 and CO 2 content gas analyzer SPIROLYT is used the analyzer continuously measures and records atmospheric concentration of O 2 concentration of CO 2 since composition of atmosphere is constant straight (zero) lines are recorded on a sheet of paper (blue for CO 2, red for O 2 ) CO 2 O 2

35 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 O 2 a CO 2 is detected proceed with the measurement until a new straight line is recorded again distance between lines = difference in O 2 a CO 2 % between the sample and atmosphere read the results by using a ruler (blue for CO 2, red O 2 ) DCO 2 DO 2

36 Result: calculate the % O 2 and CO 2 in the sample %O 2 = decrease in O 2 in the sample in contrast to atmospheric air O 2 in expired air = O 2 in atmospheric air - DO 2 % CO 2 = increase in CO 2 in the sample in contrast to atmospheric air CO 2 in expired air = CO 2 in atmospheric air + DCO 2 Conclusion: is the result normal? Explain DCO 2 DO 2

37 Task: Measurement of the expiratory peak flow with a peak flow meter

38 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 % 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).

39 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.

40 Normal peak flow readings vary, depending on Age Body size Gender The range of normal peak flow readings is published on a chart

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42 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.

43 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