Historical Background and Book Contents
5
Italian physician Caesalpinus apparently identified the pulmonary
circulation and its two types of blood vessels: vena cava and pulmonary
vein and pulmonary artery and aorta. Hooke (1635-1703;of Hooke’s law
of elasticity), an assistant of the English chemist Boyle (1627-1692; of
Boyle’s law of gases), recognized that respiration was necessary. But it
was the English physiologist Lower (163 1-1691) who continued the
investigation to
show the importance of ventilation-perfusion, i.e.
exchange of gases between the lung and blood. Gas transport in blood
was reported by Magnus in 1837. He demonstrated that there was
greater oxygen content in arterial blood and greater carbon dioxide
content in the venous blood. Other formed elements, such as hemoglobin
were discovered by Funke in 1851 and has been shown as an oxygen
transporter. Neural effect was shown by Haldane, that carbon dioxide
is
a
normal physiologic stimulus for the respiratory centers. The Haldane
effect is now well appreciated in respiratory function.
Lack
of
instrumentation, the measurements of the magnitudes of
blood pressure and flow took considerably longer than the interpretation
of the circulatory function. Hales in 1733 had incidentally already
registered the magnitude of the blood pressure level about which blood
oscillates. His initial measurement of blood pressure with
a
glass tube in
a hare has been well illustrated in many publications.
Thus, the
magnitude of the mean arterial pressure and the amplitude of oscillation,
or pulse pressure, were already known at that time. Hales’ measurements
however, did not induce recognition of the great importance of blood
pressure magnitude for many decades. We now know that the increased
magnitudes of mean blood pressure and pulse pressure are major
contributors to hypertension and many forms of cardiovascular diseases.
The shape of the pressure pulse became known only in the 19th
century when Ludwig came up with the kymograph which inscribed
blood pressure waveforms. His instrument provided information within
a single beat which was a truly a technological advance. Its accuracy
was not comparable to present day instrument, although not an issue at
the time. Blood pressure recording with the sphygmographs by Marey
and his contemporary Mahomed has led to the clinical assessment of
arterial diseases, such as hypertension. Incidentally, Chaveau and Marey
(1
863)
also recorded cardiac chamber pressures.
Both, shortly later,
measured blood flow with an instrument they developed, now known as
the bristle flowmeter.
