Respiratory Physiology

- introduction

Daniel HodycDepartment of Physiology

UK 2.LF

1. Pulmonary Ventilation

2. Mechanics of Breathing

3. Ventilation/perfusion ratio, regulation

4. Regulation of Breathing

Respiratory Physiology

1. Pulmonary ventilation- transport of gases to alveoli

2. Pulmonary diffusionfactors determining gas transport

across the membrane

3. Perfusion

4. Ventilation/perfusion ratio

Gas transport in lungs

1. Partial pressure

2. Lung volumes and capacities

3. Alveolar ventilation

4. Anatomical and functional death space, effective ventilation

Pulmonary ventilation

Partial pressure of the gas

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

PatmO2 = Patm * FO2

PatmO2 = 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

inspiratory reserve volume

expiratory 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

Uneven ventilation Inaccurate measurement

C1 * V1 C2 * (V1 + V2)

Measurement of functional residual capacity

- pletysmograph

Boyl´s law: P * V = const

P1* V1 = P1´* (V1 - dV)

P2* V2 = P2´* (V2 + dV)

V2 = FRC

P1* V1

P2* V2

Air composition in respiratory system

Alveolar ventilation

02

C02

ventilation of anatomic dead space

inspiration expiration

Alveolar ventilation

Relationship between tidal volume, frequency and

effective ventilationMinute

ventilation

ml/min

Tidalvolume

ml

Frekvency

c/s

AlveolarVentilatio

n ml/min

Ventilation

Anat. deadspaceml/min

Effectiveventilatio

n%

8000 250 32 3200 4800 40

8000 500 16 5600 2400 70

8000 1000 8 6800 1200 85

Why not to breathe with minimal frequency?

Work of breathing

Measurement of anatomic dead space

Fowler´smethod

- insp - 100% 02

- exp - nitrogen concentrationmeasurement

VD

Physiologic dead spaceventilated but not perfused alveoli

PECO2 PACO2 PaCO2

VT

VA

VAeff

ventilation of anatomic dead space

ventilation of physiologic dead space

VD

VT

=PaCO2 PECO2

PaCO2

- Bohr equation

Uneven ventilation

The worst ventilation - apical parts

- 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,

Summary

Thank you

for your

attention

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

11th