RESPIRATORY FUNCTIONS
MECHANICS OF  RESPIRATORY  SYSTEM
GAS TRANSPORT
Author of presentation:
 doc.MUDr. Milena Šimurdová, CSc.
RESPIRATORY SYSTEM

 STEPS IN THE DELIVERY OF  O2    TO THE CELLS
airways
alveoli
alveolar-capillary m.
capillary
UTILIZATION OF  O2  BY MITOCHONDRIA
TRANSPORT OF O2  IN THE BLOOD
DIFFUSION OF O2  ACROSS  ALVEOLAR-CAPILLARY MEMBRANE
DIFFUSION OF O2                          FROM CAPILLARY TO THE CELLS
1
VENTILATION             OF THE LUNGS
INTERNAL RESPIRATION
CO2 OUTPUT  ~250 ml / min
 O2  UPTAKE  ~300 ml / min
AT REST

AIR PASSAGES
ANATOMICAL DEAD SPACE –CONDUCTING ZONE
NASAL PASSAGES
PHARYNX
LARYNX
TRACHEA
BRONCHI
BRONCHIOLES
TERMINAL BRONCHIOLES
2
RESPIRATORY ZONE
(GAS EXCHANGE)
Total alveolar area ~100 m2
Other physiological functions:
   air is warmed, cleaned and takes up water vapour
    respiratory reflex responses to the irritants
    speech and singing (function of larynx)

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CAST OF HUMAN AIR PASSAGES
TRACHEA
BRONCHI
BRONCHIOLES
TERMINAL BRONCHIOLES
3
AERODYNAMIC RESISTENCE

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ciliated cylindrical epithelium
lamina propria
visceral               pleura
smooth muscle cells
cartilage
blood vessels
gland
goblet cell
mucus
4
AUTONOMIC INNERVATION        of smooth muscle cells
Muscarinic receptors: Acetylcholine activates bronchoconstriction
b-adrenergic receptors: Noradrenaline activates bronchodilatation
BRONCHUS
Æ < 1 mm
TERMINAL BRONCHIOLE

f = 12/min
VT = VA + VD
VD   part of tidal volume remaining  in the dead space ~ 150 ml
5
4.2 l/min
6 l/min
ALVEOLAR VENTILATION
  VA
·
 = VA x f
1.8 l/min
DEAD SPACE VENTILATION
 VD
·
= VD x f
PULMONARY MINUTE VENTILATION
   V
∙
= VT x f
VT   tidal volume  ~ 500 ml
VA   part of tidal volume entering alveoli  ~ 350 ml

6
IN HEALTHY INDIVIDUALS
both  spaces are practically identical
 DEAD SPACE
TOTAL GAS VOLUME NOT EQUILIBRATED WITH BLOOD (without exchange of gasses)
ANATOMICAL dead space  -  volume of  air passages
FUNCTIONAL (total) dead space
ANATOMICAL dead space + total VOLUME of ALVEOLI without functional capillary bed

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SPIROMETRY
water seal
subject
inspiration
expiration
inverted bell
7
(measurements of lung volumes, capacities, functional investigations, …)

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LUNG VOLUMES
TIDAL VOLUME VT
EXPIRATORY                   RESERVE VOLUME  ERV
~1.7
8
maximal inspiratory level
RESIDUAL VOLUME  RV
  ~1.3
maximal expiratory level
end of quiet expiration
DILUTION METHOD  He
INSPIRATORY             RESERVE VOLUME  IRV
~2.5
[l ]
end of quiet inspiration
He
reservoir (Vr)
RV
ci
3  Calculation of residual volume RV from the initial and final He concentrations in reservoir
(ci , cf).
He
reservoir (V)
RV
cf
 Þ Equilibration of the air in the residual volume and reservoir
Principle of  method:  1 Maximal expiration, 2 Repeated inspiration from and expiration into a
reservoir (known volume Vr) with inert gas He (known concentration ci)

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maximal expiratory level
maximal inspiratory level
VC - the largest amount of air that can be expired after  maximal
            inspiration
VC
VITAL CAPACITY   =  VT + IRV + ERV
~ 4.7 l
VC
9
TLC
TOTAL LUNG CAPACITY = VC + RV
~ 6.0 l
TLC
~1.2 l
RV
FUNCTIONAL RESIDUAL CAPACITY
<3.0 l
end of quiet expiration
INSPIRATORY  CAPACITY
>3.0 l