Respiratory Physiology - introduction

Daniel Hodyc Department of Physiology UK 2.LF

Respiratory Physiology

1. Pulmonary Ventilation 2. Mechanics of Breathing 3. Ventilation/perfusion ratio, regulation 4. Regulation of Breathing

Gas transport in lungs

1. Pulmonary ventilation

transport of gases to alveoli

2. Pulmonary diffusion

factors determining gas transport across the membrane

3. Perfusion 4. Ventilation/perfusion ratio

Pulmonary ventilation

1. Partial pressure 2. Lung volumes and capacities 3. Alveolar ventilation 4. Anatomical and functional death space, effective ventilation

Partial pressure of the gas

- in determined by its concentration in the mixture and by the overall pressure of the gas mixture

P atm O 2 = P atm * FO 2

P atm O 2 = 740 torr * 0,21 - in the liquid - partial pressure of the gas component, which is balanced with the liquid

Lung volumes and capacities

tidal volume expiratory reserve volume inspiratory reserve volume residual volume

Lung volumes and capacities

Spirometer - measurement of lung volumes - measurement of the oxygen consumption

Measurement of residual volume and FRC

- helium equilibration method C 1 * V 1

Uneven ventilation

C 2 * (V 1 + V 2 )

Inaccurate measurement

Measurement of functional residual capacity

- pletysmograph P 1 * V 1 P 2 * V 2

Boyl´s law: P * V = const

P 1 * V 1 = P 1 ´ * (V 1 - dV) P 2 * V 2 = P 2 ´ * (

V 2

+ dV)

V 2 = FRC

Air composition in respiratory system

Alveolar ventilation ventilation of anatomic dead space 0 2 C0 2

inspiration expiration

Alveolar ventilation

Relationship between tidal volume, frequency and effective ventilation

Minute ventilation ml/min Tidal volume ml 8000 8000 8000 250 500 1000

Frekvency c/s

Alveolar Ventilation ml/min Ventilation Anat. dead space ml/min

Effective ventilation % 32 16 8

3200 5600 6800 4800 2400 1200

40 70 85

Why not to breathe with minimal frequency?

Work of breathing

Physiologic dead space

ventilated but not perfused alveoli V T

Bohr equation

V D V T = P aCO2 P aCO2 P ECO2 ventilation of anatomic dead space V A ventilation of physiologic dead space V Aeff P E CO 2 P A CO 2 P a CO 2

Uneven ventilation The worst ventilation - apical parts

Summary

- lung volumes measurable by spirometer (VT,IRV,ERV) - RV, FRC - measurable by He, plethysmograph - anatomic dead space - effective ventilation and respiratory frequency, work of breathing - physiologic dead space,

Thank you for your attention

Pictures and schemes – J.B.West - Respiratory Physiology, LWW - Guyton, Hall - Textbook of Medical Physiology, 11th