Transcript Physiology of Respiration Part IV Prof. Dušan M. Mitrović, MD, Ph.D

Physiology of Respiration
Part IV
Prof. Dušan M. Mitrović, M.D., Ph.D
Blood flow and Metabolism
How the pulmonary Circulation
Removes Gas From the Lung
and Alters Some Metabolites
Systemic and Pulmonary Circulation
Pressures Around Pulmonary Blood Vessels
Note: around alveaolar vessels pressure is alveolar
The pressure difference between the isside and outside
of the capillaries is called transmural pressure
Many alveoli and an extra-alveolar vessel with its perivascular sheet
Pulmonary Vascular Resistance
Vascular resistance =
input pressure – output pressure
blood flow
Fall in pulmonary vascular resistance as
the pulmonary arterial or venous pressure
is raised.
There are two mechanisms for the decrease in pulmonary vascular
resistance that occurs as vascular pressures are raised
opening previously
closed vessels
increase in caliber
of vessels
Effects of lung volume on pulmonary vascular resistance
when the transmural pressure of capillaries is held constant
At low lung volumes, resistance is high because the extraalveolar vessels become narrow.
At high volumes, the capillaries are stretched, and their caliber is reduced.
Assesment of the pulmonary blood flow
Measurements of capillary blood flow by recording
nitrous oxide uptake in body plethysmograph
Distribution of Blood Flow
Measurement of the distribution of blood flow
in the upright human lung with radioactive xenon
Disolved xenon is envolved into alveolar gas from pulmonaru capilaries
Regional perfusion and gravity
PPA blood pressure in the pulmonary artery
PPV blood pressure in pulmonary vein
Ppc pericapillary pressure
PL,is interstitial pressure in the lung tissue
Qc capillary blood flow
The Starling resistors
Rubber tube
When chamber pressure exceeds downstream pressure (A), flow is independent of
downstream pressure.
When downstream pressure exceeds chamber pressure (B), flow is idetermined by
The upstream-downstream pressure difference.
Regional capillary blood volume
Active control of circulation
Hypoxic pulmonary vasoconstriction
Water Balance in the Lung
Lymph and fluid movement in the lung
Metabolic Function of the Lung
Peptides
Angiotenzin I
Bradykinin
Converted to angiotensin II by ACE
Up to 80% inactivated
Amines
Serotonin
Noradrenalin
Almost completely removed
Up to 30% removed
Arachidonic acid metabolites
Prostaglandin E2 and E2a
Almost completely removed
Leukotriens
Almost completely removed
Two pathways of arachidonic acid metabolism
Membrane-bound phospholipid
Phospholipase A2
Arachidonic acid
Lipoxygenase
Leukotriens
Cyclooxygenase
Prostaglandins,
Tromboxane A2