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BM 2251-BIO MEDICAL BM 2251-BIO MEDICAL INSTRUMENTATION INSTRUMENTATION

G.THIYAGARAJAN G.THIYAGARAJAN BM17-LecturerBM17-Lecturer Department of Biomedical Department of Biomedical

EngineeringEngineering

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Cell Structure Cell Structure & Function& Function

http://koning.ecsu.ctstateu.edu/cell/cell.html

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Cell TheoryCell Theory

All living things are made up of cells. All living things are made up of cells. Cells are the smallest working units Cells are the smallest working units

of all living things. of all living things. All cells come from preexisting cells All cells come from preexisting cells

through cell division. through cell division.

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Definition of CellDefinition of Cell

A cell is the smallest unit that A cell is the smallest unit that is capable of performing life is capable of performing life

functions. functions.

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Examples of CellsExamples of CellsAmoeba Proteus

Plant Stem

Red Blood Cell

Nerve Cell

Bacteria

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Two Types of CellsTwo Types of Cells

ProkaryoticProkaryoticEukaryoticEukaryotic

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ProkaryoticProkaryotic

Do not have Do not have structures structures surrounded by surrounded by membranesmembranes

Few internal Few internal structuresstructures

One-celled One-celled organisms, organisms, Bacteria Bacteria

http://library.thinkquest.org/C004535/prokaryotic_cells.html

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EukaryoticEukaryotic Contain Contain organellesorganelles surrounded by membranes surrounded by membranes Most living organismsMost living organisms

Plant Animal

http://library.thinkquest.org/C004535/eukaryotic_cells.html

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““Typical” Animal CellTypical” Animal Cell

http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif

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““Typical” Plant CellTypical” Plant Cell

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Membrane is a collage of proteins & Membrane is a collage of proteins & other molecules embedded in the fluid other molecules embedded in the fluid

matrix of the lipid bilayermatrix of the lipid bilayerExtracellular fluid

Cholesterol

Cytoplasm

Glycolipid

Transmembraneproteins

Filaments ofcytoskeleton

Peripheralprotein

Glycoprotein

Phospholipids

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Many Functions of Membrane Many Functions of Membrane ProteinsProteins

Outside

Plasmamembrane

InsideTransporter Cell surface

receptorEnzymeactivity

Cell surface identity marker

Attachment to thecytoskeleton

Cell adhesion

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Movement across Movement across the Cell the Cell

Membrane Membrane

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DiffusionDiffusion

2nd Law of Thermodynamics2nd Law of Thermodynamics governs biological systemsgoverns biological systems universe tends towards disorder (entropy)universe tends towards disorder (entropy)

DiffusionDiffusion movement from movement from highhigh lowlow concentration concentration

DiffusionDiffusion movement from movement from highhigh lowlow concentration concentration

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DiffusionDiffusion Move from Move from HIGHHIGH to to LOWLOW concentration concentration

““passive transport”passive transport” no energy neededno energy needed

diffusion osmosis

movement of water

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Diffusion across cell Diffusion across cell membranemembrane Cell membrane is the boundary Cell membrane is the boundary

between inside & outside…between inside & outside… separates cell from its environment separates cell from its environment

INfoodcarbohydratessugars, proteinsamino acidslipidssalts, O2, H2O

OUTwasteammoniasaltsCO2

H2O products

cell needs materials in & products or waste out

IN

OUT

Can it be an impenetrable boundary? NO!

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Diffusion through phospholipid Diffusion through phospholipid bilayerbilayer What molecules can get through directly?What molecules can get through directly?

fats & other lipidsfats & other lipids

inside cell

outside cell

lipid

salt

aa H2Osugar

NH3

What molecules What molecules can can NOTNOT get get through directly?through directly?

polar moleculespolar molecules HH22OO

ionsions salts, ammoniasalts, ammonia

large moleculeslarge molecules starches, proteinsstarches, proteins

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Channels through cell Channels through cell membranemembrane Membrane becomes Membrane becomes semi-semi-

permeablepermeable with protein channels with protein channels specific channels allow specific specific channels allow specific

material across cell membranematerial across cell membrane

inside cell

outside cell

sugaraaH2O

saltNH3

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Facilitated DiffusionFacilitated Diffusion Diffusion through protein channelsDiffusion through protein channels

channels move specific molecules across channels move specific molecules across cell membranecell membrane

no energy neededno energy needed

“The Bouncer”“The Bouncer”

open channel = fast transport

facilitated = with help

high

low

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Active TransportActive Transport

“The Doorman”“The Doorman”

conformational change

Cells may need to move molecules Cells may need to move molecules againstagainst concentration gradientconcentration gradient shape change transports solute from shape change transports solute from

one side of membrane to other one side of membrane to other protein “pump”protein “pump” ““costs” energy = costs” energy = ATPATP

ATP

low

high

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Active transportActive transport Many models & mechanismsMany models & mechanisms

ATP ATP

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Getting through cell Getting through cell membranemembrane Passive TransportPassive Transport

Simple diffusionSimple diffusion diffusion of nonpolar, hydrophobic moleculesdiffusion of nonpolar, hydrophobic molecules

lipidslipids high high low concentration gradient low concentration gradient

Facilitated transportFacilitated transport diffusion of polar, hydrophilic moleculesdiffusion of polar, hydrophilic molecules through a through a protein channelprotein channel

high high low concentration gradient low concentration gradient

Active transportActive transport diffusion diffusion againstagainst concentration gradient concentration gradient

low low high high uses a uses a protein pumpprotein pump requires requires ATPATP

ATP

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Transport summaryTransport summarysimplediffusion

facilitateddiffusion

activetransport

ATP

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How about large molecules?How about large molecules? Moving large molecules into & out of Moving large molecules into & out of

cellcell through vesicles & vacuolesthrough vesicles & vacuoles endocytosisendocytosis

phagocytosisphagocytosis = “cellular eating” = “cellular eating” pinocytosispinocytosis = “cellular drinking” = “cellular drinking”

exocytosisexocytosis

exocytosis

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Endocytosis Endocytosis

phagocytosis

pinocytosis

receptor-mediated endocytosis

fuse with lysosome for digestion

non-specificprocess

triggered bymolecular signal

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The Special Case of The Special Case of WaterWater

Movement of water Movement of water across across

the cell membranethe cell membrane

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Osmosis is diffusion of waterOsmosis is diffusion of water

Water is very important to life, Water is very important to life, so we talk about water separatelyso we talk about water separately

Diffusion of water from Diffusion of water from high concentrationhigh concentration of of waterwater to to low concentrationlow concentration of of waterwater across a across a

semi-permeable semi-permeable membranemembrane

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Concentration of waterConcentration of water Direction of osmosis is determined by Direction of osmosis is determined by

comparing total solute concentrationscomparing total solute concentrations HypertonicHypertonic - more solute, less water - more solute, less water HypotonicHypotonic - less solute, more water - less solute, more water IsotonicIsotonic - equal solute, equal water - equal solute, equal water

hypotonic hypertonic

water

net movement of water

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Managing water balanceManaging water balance

Cell survival depends on balancing Cell survival depends on balancing water uptake & losswater uptake & loss

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Managing water balanceManaging water balance IsotonicIsotonic

animal cell immersed in animal cell immersed in mild saltmild salt solution solution exampleexample::

blood cells in blood plasmablood cells in blood plasma problemproblem: none: none

no no netnet movement movement of water of water flows across membrane flows across membrane

equally, in both directionsequally, in both directions volume of cell is stablevolume of cell is stable

balanced

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Managing water balanceManaging water balance HypotonicHypotonic

a cell in a cell in fresh waterfresh water exampleexample: : ParameciumParamecium problemproblem: : gains watergains water, ,

swells & can burstswells & can burst water continually enters water continually enters

ParameciumParamecium cell cell

solutionsolution: : contractile vacuolecontractile vacuole pumps water out of cellpumps water out of cell ATPATP

plant cellsplant cells turgidturgid

freshwater

ATP

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Water regulationWater regulation

Contractile vacuole in Contractile vacuole in ParameciumParamecium

ATP

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Managing water balanceManaging water balance HypertonicHypertonic

a cell in a cell in salt watersalt water exampleexample: : shellfishshellfish problemproblem: : lose water & dielose water & die solutionsolution: take up water or : take up water or

pump out saltpump out salt plant cellsplant cells

plasmolysisplasmolysis = wilt= wilt

saltwater

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Action and resting – Action and resting – Potential propagation of Potential propagation of

action potentialaction potential An An action potentialaction potential (also known as a (also known as a nerve nerve

impulseimpulse or a or a spikespike) is a self-regenerating wave ) is a self-regenerating wave of electrochemical activity that allows excitable of electrochemical activity that allows excitable cells (such as muscle and nerve cells) to carry a cells (such as muscle and nerve cells) to carry a signal over a distance. It is the primary electrical signal over a distance. It is the primary electrical signal generated by nerve cells, and arises from signal generated by nerve cells, and arises from changes in the permeability of the nerve cell's changes in the permeability of the nerve cell's axonal membranes to specific ions. Action axonal membranes to specific ions. Action potentials are pulse-like waves of voltage that potentials are pulse-like waves of voltage that travel along several types of cell membranestravel along several types of cell membranes

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Relatively static Relatively static membrane potential membrane potential of quiescent cells is called of quiescent cells is called resting resting membrane potentialmembrane potential (or resting (or resting voltage), as opposed to the specific voltage), as opposed to the specific dynamic electrochemical dynamic electrochemical phenomenona called action potential phenomenona called action potential and graded membran potential.and graded membran potential.

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Electrode –Electrolyte InterfaceElectrode –Electrolyte Interface

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Half-Cell Potentials Half-Cell Potentials

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Silver –SilverChloride Silver –SilverChloride

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Ionic ActivityIonic ActivityRelative half-Cell PotentialsRelative half-Cell Potentials

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Electrode Behavior Electrode Behavior

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Frequency Dependency Frequency Dependency

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Electrode Electrode Skin InterfaceSkin Interface

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The electric ModelThe electric Model

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Motion Artifacts Motion Artifacts

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Biopotential ElectrodesBiopotential Electrodes

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Biopotential electrodes Biopotential electrodes

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Suction Electrode Suction Electrode

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Floating Electrodes Floating Electrodes

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Flexible Electrodes Flexible Electrodes

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Internal Electrodes Internal Electrodes

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Electrode Arrays Electrode Arrays

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Saturated Calomel Saturated Calomel ElectrodeElectrode

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MicroelectrodesMicroelectrodes

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Microelectrodes Microelectrodes

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AmplifierAmplifier

An An amplifieramplifier or simply or simply ampamp, is any , is any device that changes, usually increases, device that changes, usually increases, the amplitude of a signal. The "signal" is the amplitude of a signal. The "signal" is usually voltage or current. The usually voltage or current. The relationship of the input to the output of relationship of the input to the output of an amplifier — usually expressed as a an amplifier — usually expressed as a function of the input frequency — is function of the input frequency — is called the transfer function of the called the transfer function of the amplifier, and the magnitude of the amplifier, and the magnitude of the transfer function is termed the gain.transfer function is termed the gain.

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PreamplifiersPreamplifiers

A A preamplifierpreamplifier (preamp), or (preamp), or control control ampamp in some parts of the world, is an in some parts of the world, is an electronic amplifier which precedes electronic amplifier which precedes another amplifier to prepare an electronic another amplifier to prepare an electronic signal for further amplification or signal for further amplification or processing. The preamplifier circuitry processing. The preamplifier circuitry may or may not be housed as a separate may or may not be housed as a separate component.component.

In general, the function of a preamp is to In general, the function of a preamp is to amplify a low-level signal to line-levelamplify a low-level signal to line-level

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Preamplifiers may be:Preamplifiers may be: incorporated into the housing or chassis incorporated into the housing or chassis

of the amplifier they feed of the amplifier they feed in a separate housing in a separate housing mounted within or near the signal mounted within or near the signal

source, such as a turntable, microphone source, such as a turntable, microphone or musical instrument.or musical instrument.

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Differential Amplifiers

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Differential amplifier is a type of electronic amplifier that multiplies the difference between two inputs by some constant factor (the differential gain). Many electronic devices use differential amplifiers internally. Given two inputs and , a practical differential amplifier gives an output Vout:

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Chopper Amplifiers

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In this type of amplifier the positive rectangular DC pulses arrive at the input of the amplifier circuit at capacitor C1.

These pulses arrive at the base of Q1 as narrow spikes,

which momentarily turn Q1 on. This in turn momentarily

turns Q2 on, which allows current to flow through the

primary of transformer T1. Now the primary of transformer

T1 is really an L-C tank circuit. (Remember that the primary

winding of the transformer is actually a big inductor.) When this tank circuit is hit by a pulse, it will produce a cycle or two of pure sine wave. When hit, in other words, the tank circuit will ring like a bell.

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The amplifier circuit is the clapper that rings the bell. Notice the secondary of T1 is center tapped to —60 Vp. The secondary of

T1 sees a pure AC sine wave, and to this AC signal, the —60 Vp

appears as a ground. This means that for the positive half-cycle of the sine wave, Q3 would see a positive pulse, and Q4 would

see a negative pulse. Both power transistors are NPN transistors, so a positive bias is needed at the base to cause them to conduct. As both bases are grounded , Q4 would go into conduction

because its emitter is lower than its base, giving it a forward base-emitter bias. The output of the tapped control winding would then be a sine wave. It should be noticed that the tapped control winding has +60 Vp on it, and the secondary of T1 has

—60 Vp on it. This means that the output of the tapped control winding is going to be a 120-Vp sine wave.

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Isolation Amplifier

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Isolation amplifiers provide electrical isolation and an electrical safety barrier. They protect data acquisition components from common mode voltages, which are potential differences between instrument ground and signal ground. Instruments without an isolation barrier that are applied in the presence of a common mode voltage allow ground currents to circulate, leading in the best case to a noisy representation of the signal under investigation. In the worst case, assuming that the magnitude of common mode voltage and/or current is sufficient, instrument destruction is likely.

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This action serves to protect the amplifier and the instrument connected to it, while still allowing a reasonably accurate measurement.

These amplifiers are also useful when you need to amplify low-level signals in multi-channel applications. They can also eliminate measurement errors caused by ground loops. Amplifiers with internal transformers reduce circuit costs by eliminating the need for additional isolated power supply. We usually use them as analogue interfaces between systems with separated grounds.

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Biosensing PrinciplesBiosensing Principles ElectrochemicalElectrochemical

PotentiometricPotentiometric AmperometricAmperometric FET basedFET based ConductometricConductometric

OpticalOptical PiezoelectricPiezoelectric

ThermalThermal

=> Neurochemical sensor for Dopamine, Nitric Oxide, etc.

=> Pulse oximeter=> Accelerometer,

microphone=> Implanted rectal

probe, pacemaker

Chemical binding changes the resonance property such as frequency

Absorption, fiber optic transmission

Thermal/temperature response to chemical reaction

Chemical Sensing

Direct electrochemical transduction

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Biosensing PrinciplesBiosensing Principles

Holly Grail…da Vinci Code of sensing…Glucose sensor

-> Know every thing there is to know…research “

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Electrochemical SensorsElectrochemical Sensors

Potentiometric : These involve the measurement of the emf (potential) of a cell at zero current. The emf is proportional to the logarithm of the concentration of the substance being determined.Amperometric : An increasing (decreasing) potential is applied to the cell until oxidation (reduction) of the substance to be analyzed occurs and there is a sharp rise (fall) in the current to give a peak current. The height of the peak current is directly proportional to the concentration of the electroactive material. If the appropriate oxidation (reduction) potential is known, one may step the potential directly to that value and observe the current.Conductometric. Most reactions involve a change in the composition of the solution. This will normally result in a change in the electrical conductivity of the solution, which can be measured electrically.

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Blood Gas MeasurementBlood Gas Measurement

Fast and accurate measurements of the blood levels of the partial pressures of oxygen (pO2), carbon dioxide (pCO2) as well as the concentration of hydrogen ions (pH) are vital in diagnosis.

Oxygen is measured indirectly as a percentage of Haemoglobin which is combined with oxygen (sO2)

sOH bO

H b2

21 0 0

pO2 can also provide the above value using the oxyhaemoglobin dissociation curve but is a poor estimate.

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pH electrodepH electrode

Governing equation is the Nernst Equation E

R T

nF

H

HHi

ln 0

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pCOpCO22 Electrode Electrode

The measurement of pCO2 is based on its linear relationship with pH over the range of 10 to 90 mm Hg.

H O C O H C O H H C O2 2 2 3 3

The dissociation constant is given by

kH H C O

a pC O

3

2

Taking logarithms

pH = log[HCO3-] – log k – log a – log pCO2

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pOpO22 electrode electrode

The pO2 electrode consists of a platinum cathode and a Ag/AgCl reference electrode.

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Optical BiosensorsOptical Biosensors

Sensing Principle

They link changes in light intensity to changes in mass or concentration, hence, fluorescent or colorimetric molecules must be present.

Various principles and methods are used :

Optical fibres, surface plasmon resonance,Absorbance, Luminescence

LED

Photodetector

Finger

IR light

Wavelength

600 – 900 nm

Absorption oxyhemoglobin

deoxyhemoglobin

Infrared Spectroscopy

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Fiber Optic BiosensorFiber Optic Biosensor

BalloonThermistor

Light transmitter Receiver/

reflected light

Intraventricular

Fiber optic catheter

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Absorption/FluorescenceAbsorption/Fluorescence

Different dyes show peaks of different values at different concentrations when the absorbance or excitation is plotted against wavelength.

Phenol Red is a pH sensitive reversible dye whose relative absorbance (indicated by ratio of green and red light transmitted) is used to measure pH.

HPTS is an irreversible fluorescent dye used to measure pH.

Similarly, there are fluorescent dyes which can be used to measure O2 and CO2 levels.

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Pulse OximetryPulse Oximetry

Two wavelengths of monochromatic light -- red (660 nm) and infrared (940 nm) -- are used to gauge the presence of oxygenated and reduced hemoglobin in blood. With each pulse beat the device interprets the ratio of the pulse-added red absorbance to the pulse-added infrared absorbance. The calculation requires previously determined calibration curves that relate transcutaneous light absorption to sO2.

The pulse oximeter is a spectrophotometric device that detects and calculates the differential absorption of light by oxygenated and reduced hemoglobin to get sO2. A light source and a photodetector are contained within an ear or finger probe for easy application.

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Glucose SensorsGlucose SensorsEnzymatic Approach

G lu e O G lucon icA cid H OG lu eO xidaseco s co s 2 2 2

Makes use of catalytic (enzymatic) oxidation of glucose

The setup contains an enzyme electrode and an oxygen electrode and the difference in the readings indicates the glucose level.

The enzyme electrode has glucose oxidase immobilized on a membrane or a gel matrix.

Platinum electrode

Plastic membraneGlucose

O2

Gluconic acid

Silver anode

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Glucose SensorGlucose SensorAffinity Approach

This approach is based on the immobilized competitive binding of a particular metabolite (glucose) and its associated fluorescent label with receptor sites specific to the metabolite (glucose) and the labeled ligand. This change in light intensity is then picked up.

3 mm

0.3 mm

Hollow dialysis fiber

Immobilized Con A

Excitatation

Emission

Optical Fiber

Glucose

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Measurement of blood pressure

Blood pressure (BP) is the pressure (force per unit area) exerted by circulating blood on the walls of blood vessels, and constitutes one of the principal Vital signs. The pressure of the circulating blood decreases as it moves away from the heart through arteries and capillaries, and toward the heart through veins. When unqualified, the term blood pressure usually refers to brachial arterial pressure: that is, in the major blood vessel of the upper left or right arm that takes blood away from the heart. Blood pressure may, however, sometimes be measured at other sites in the body, for instance at the ankle. The ratio of the blood pressure measured in the main artery at the ankle to the brachial blood pressure gives the Ankle Brachial Pressure Index (ABPI).

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Arterial pressure is most commonly measured via a sphygmomanometer, which historically used the height of a column of mercury to reflect the circulating pressure (see Noninvasive measurement). Today blood pressure values are still reported in millimetres of mercury (mmHg), though aneroid and electronic devices do not use mercury.

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For each heartbeat, blood pressure varies between systolic and diastolic pressures. Systolic pressure is peak pressure in the arteries, which occurs near the end of the cardiac cycle when the ventricles are contracting. Diastolic pressure is minimum pressure in the arteries, which occurs near the beginning of the cardiac cycle when the ventricles are filled with blood. An example of normal measured values for a resting, healthy adult human is 115 mmHg systolic and 75 mmHg diastolic (written as 115/75 mmHg, and spoken (in the US) as "one fifteen over seventy-five"). Pulse pressure is the difference between systolic and diastolic pressures.

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Systolic and diastolic arterial blood pressures are not static but undergo natural variations from one heartbeat to another and throughout the day (in a circadian rhythm). They also change in response to stress, nutritional factors, drugs, disease, exercise, and momentarily from standing up. Sometimes the variations are large. Hypertension refers to arterial pressure being abnormally high, as opposed to hypotension, when it is abnormally low. Along with body temperature, blood pressure measurements are the most commonly measured physiological parameters.

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Arterial pressures can be measured invasively (by penetrating the skin and measuring inside the blood vessels) or non-invasively. The former is usually restricted to a hospital setting.

The predominantly used unit for blood pressure measurement is mmHg (millimeter of mercury). For example, normal pressure can be stated as 120 over 80, where 120 is the systolic reading and 80 is the diastolic.

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Auscultatory method aneroid sphygmomanometer with stethoscope

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Mercury manometer

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Digital BP measurement equipment

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The auscultatory method uses a stethoscope and a sphygmomanometer. This comprises an inflatable (Riva-Rocci) cuff placed around the upper arm at roughly the same vertical height as the heart, attached to a mercury or aneroid manometer. The mercury manometer, considered to be the gold standard for arterial pressure measurement measures the height of a column of mercury, giving an absolute result without need for calibration, and consequently not subject to the errors and drift of calibration which affect other methods. The use of mercury manometers is often required in clinical trials and for the clinical measurement of hypertension in high risk patients, such as pregnant women

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Classification of blood pressure for adults

Category systolic, mmHg diastolic, mmHg

Hypotension < 90 or < 60   

Normal  90 – 119 and 60 – 79   

Prehypertension 120 – 139 or 80 – 89

Stage 1 Hypertension 140 – 159 or 90 – 99

Stage 2 Hypertension ≥ 160 or ≥ 100 

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Placement of Blood Pressure Cuff

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Cardiac output

Cardiac output (Q) is the volume of blood being pumped by the heart, in particular by a ventricle in a minute. This is measured in dm3 min-1 (1 dm3 equals 1000 cm3 or 1 litre). An average cardiac output would be 5L.min-1 for a human male and 4.5L.min-1 for a female Measuring Cardiac Output

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Cardiac output

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Q can be calculated from these measurements:

VO2 consumption per minute using a spirometer (with the

subject re-breathing air) and a CO2 absorber.

the oxygen content of blood taken from the pulmonary artery (representing mixed venous blood) .the oxygen content of blood from a cannula in a peripheral artery (representing arterial blood).

From these values, we know that:VO2 = (Q x CA) - (Q x CV)where

CA = Oxygen content of arterial blood

CV = Oxygen content of venous blood.

This allows us to sayQ = (VO2/[CA - CV])*100

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Cardiac rate

Heart rate (HR) is a measure of the number of heart beats per minute (bpm). The average resting human heart rate is about 70 bpm. Heart rate varies significantly between individuals based on fitness, age and genetics. Endurance athletes often have very low resting heart rates. Heart rate can be measured by monitoring one's pulse. Pulse measurement can be achieved using specialized medical devices, or by merely pressing one's fingers against an artery (typically on the wrist or the neck; note that this can be dangerous if done incorrectly or for too long).

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Heart sound

The heart sounds are the noises (sound) generated by the beating heart and the resultant flow of blood through it, specifically the turbulence created when the heart valves snap shut. This is also called a heartbeat. In cardiac auscultation, an examiner uses a stethoscope to listen for these sounds, which provide important information about the condition of the heart.

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In healthy adults, there are two normal heart sounds often described as a lub and a dub (or dup), that occur in sequence with each heart beat. These are the first heart sound (S1) and

second heart sound (S2), produced by the closing of the

tricuspid + mitral valves and aortic + pulmonic valves, respectively. In addition to these normal sounds, a variety of other sounds may be present including heart murmurs, adventitious sounds, and gallop rhythms S3 and S4.

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Heart murmurs are generated by turbulent flow of blood, which may occur inside or outside the heart. Murmurs may be physiological (benign) or pathological (abnormal). Abnormal murmurs can be caused by stenosis restricting the opening of a heart valve, resulting in turbulence as blood flows through it. Abnormal murmurs may also occur with valvular insufficiency (or regurgitation), which allows backflow of blood when the incompetent valve closes with only partial effectiveness. Different murmurs are audible in different parts of the cardiac cycle, depending on the cause of the murmur

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Respiratory rate

Respiratory rate (RR) (aka respiration rate, pulmonary ventilation rate or ventilation rate) is the number of breaths a living being, such as a human, takes within a certain amount of time (frequently given in breaths per minute).

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The human respiration rate is usually measured when a person is at rest and simply involves counting the number of breaths for one minute by counting how many times the chest rises. Respiration rates may increase with fever, illness, OR other medical conditions. When checking respiration, it is important to also note whether a person has any difficulty breathing.

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General Control of Breathing

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Breathing is controlled by the medulla of the brainstem. It repeatedly triggers contraction of the diaphragm initiating inspiration. The rate of breathing changes with activity level in response to carbon dioxide levels, and to a lesser extent, oxygen levels, in the blood. Carbon dioxide lowers the pH of the blood.

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Average respiratory rates, by age:

Newborns: Average 44 breaths per minute Infants: 20–40 breaths per minute Preschool children: 20–30 breaths per minute Older children: 16–25 breaths per minute Adults: 12–20 breaths per minute Adults during strenuous exercise 35–45 breaths per minute Athletes' peak 60–70 breaths per minute

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Gas volume – Flow rate of Co2, o2 in

exhaust air

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Respiration refers to the mechanisms for obtaining oxygen from the air and delivering it to the tissues, while eliminating carbon dioxide from the body. It is related to cellular respiration, the biochemical processes that consume this oxygen and generate the carbon dioxide in the course of making adenosine triphosphate (ATP). Respiration in the former sense involves four processes: (1) breathing, or ventilation of the lungs (2) gas exchange between air and blood in the lungs (3) gas transport in the blood and (4) gas exchange between the blood and target tissues.

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Gas Transport

Blood leaving the lungs is therefore relatively high in O2

(oxygen in its diatomic form) and low in CO2. It travels via the

pulmonary veins to the left side of the heart, which pumps it out into the systemic circulation. This division of the circulatory system delivers it to every organ of the body.

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Systemic Gas Exchange

When the blood reaches the systemic blood capillaries, gases undergo processes that are essentially the reverse of what occurs in the pulmonary alveoli. The blood unloads O2, which

diffuses into the tissue fluid and thus reaches the cells around the blood capillaries. At the same time, the CO2 generated by

the metabolism of those cells diffuses into the blood to be carried away to the lungs for disposal.

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Blood typically contains 95 mmHg O2 upon arrival at the

systemic capillaries and 40 mmHg O2 upon leaving.

Conversely, the blood has 40 mmHg of CO2 on arrival at the

systemic capillaries and typically 46 mmHg CO2 when it

leaves. The blood does not, however, unload the same amount of O2 to all tissues or pick up the same amount of CO2. The

more active a tissue is, the warmer it is, the lower its O2 level

is, and the lower its pH is (because it generates more CO2 and

CO2 reduces the pH of body fluids). Heat, low O2, low pH, and

other factors enhance O2 unloading and CO2 loading, so tissues

that need the most oxygen and waste removal get more than less active tissues do. The biochemistry of hemoglobin is mainly responsible for this elegant adjustment of gas exchange to the individual needs of different tissues

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PH of blood

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GSR measurements

Galvanic skin response (GSR), also known as electrodermal response (EDR), psychogalvanic reflex (PGR), or skin conductance response (SCR), is a method of measuring the electrical resistance of the skin. There has been a long history of electrodermal activity research, most of it dealing with spontaneous fluctuations.

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One branch of GSR explanation interprets GSR as an image of activity in certain parts of the body. The mapping of skin areas to internal organs is usually based on acupuncture pointsA Galvanic Skin Response 60 second sample signal. The signal was acquired in the middle and ringer fingers. The source file was processed with scipy and exported with matplolib. The sampling rate was 256 Hz.

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The device measures electrical conductivity between 2 points, much like an ohmmeter. The two paths for current are along the surface of the skin and through the body. Active measuring involves sending a small amount of current through the body. Due to the sensitivity of the human body to electrical shock, sometimes more passive methods are used to determine the conductivity of the skin. When correctly calibrated, the GSR can measure these subtle differences.

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Measurement of Measurement of Flow & Volume of BloodFlow & Volume of Blood

A measurement of paramount importance: concentration of OA measurement of paramount importance: concentration of O22 and other and other nutrients in cells nutrients in cells Very difficult to measure Very difficult to measure Second-class measurement: blood flow and changes in blood volume Second-class measurement: blood flow and changes in blood volume

correlate well with concentrationcorrelate well with concentration Third-class measurement: blood pressure Third-class measurement: blood pressure correlates well with blood correlates well with blood

flowflow Fourth class measurement: ECG Fourth class measurement: ECG correlates adequately with blood correlates adequately with blood

pressurepressure How to make blood flow / volume measurements? Standard flow meters, How to make blood flow / volume measurements? Standard flow meters,

such as turbine flow meters, obviously cannot be used!such as turbine flow meters, obviously cannot be used! Indicator-dilution method: cont./rapid injection, dye dilution, Indicator-dilution method: cont./rapid injection, dye dilution,

thermodilutionthermodilution Electromagnetic flowmetersElectromagnetic flowmeters Ultrasonic flowmeters / Doppler flowmetersUltrasonic flowmeters / Doppler flowmeters Plethysmography: Chamber / electric impedance / Plethysmography: Chamber / electric impedance /

photoplethysmographyphotoplethysmography

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Indicator Dilution with Indicator Dilution with Continuous InjectionContinuous Injection

Measures flow / cardiac output averaged over several heart beatsMeasures flow / cardiac output averaged over several heart beats

Fick’s technique: the amount of a substance (OFick’s technique: the amount of a substance (O22) taken up by an organ ) taken up by an organ / whole body per unit time is equal to the arterial level of O/ whole body per unit time is equal to the arterial level of O22 minus the minus the venous level of Ovenous level of O22 times the blood flow times the blood flow

va CC

dtdmC

dtdm

dt

dVF

Blood flow, liters/min(cardiac output)

Consumption of O2 (mL/min)

Arterial and venousconcentration of O2 (mL/L of blood)

dtdV

dtdmC

Change in [] due to continuously added indicator m to volume V

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Fick’s techniqueFick’s technique

How is dm/dt (OHow is dm/dt (O22 consumption) measured? consumption) measured? Where and how would we measure CWhere and how would we measure Caa and C and Cvv? ?

(Exercise)(Exercise)

minL/5mL/L140L/mL190

minmL/250

][O][O

min)(mL/O

22

2

va

nconsumptioOutputCardiac

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Indicator Dilution with Indicator Dilution with Rapid InjectionRapid Injection

A known amount of a substance, such as a dye or radioactive A known amount of a substance, such as a dye or radioactive isotope, is injected into the venous blood and the arterial isotope, is injected into the venous blood and the arterial concentration of the indicator is measured through a serious of concentration of the indicator is measured through a serious of measurements until the indicator has completely passed through measurements until the indicator has completely passed through given volume.given volume.

The cardiac output (blood flow) is amount of indicator injected, The cardiac output (blood flow) is amount of indicator injected, divided by average concentration in arterial blood.divided by average concentration in arterial blood.

t

dttC

mF

0

)(

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Indicator – Dilution CurveIndicator – Dilution Curve

After the bolus is injected at time A, there is a transportation delay before the After the bolus is injected at time A, there is a transportation delay before the concentration begins rising at time B. After the peak is passed, the curve enters an concentration begins rising at time B. After the peak is passed, the curve enters an exponential decay region between C and D, which would continue decaying alone the exponential decay region between C and D, which would continue decaying alone the dotted curve to tdotted curve to t11 if there were no recirculation. However, recirculation causes a second if there were no recirculation. However, recirculation causes a second

peak at E before the indicator becomes thoroughly mixed in the blood at F. The dashed peak at E before the indicator becomes thoroughly mixed in the blood at F. The dashed curve indicates the rapid recirculation that occurs when there is a hole between the left curve indicates the rapid recirculation that occurs when there is a hole between the left and right sides of the heart.and right sides of the heart.

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An ExampleAn Example

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Dye DilutionDye Dilution

In dye-dilution, a commonly used dye is In dye-dilution, a commonly used dye is indocyanine green indocyanine green (cardiogreen), which satisfies the following(cardiogreen), which satisfies the following InertInert SafeSafe Measurable though spectrometryMeasurable though spectrometry EconomicalEconomical Absorption peak is 805 nm, a wavelength at which absorption Absorption peak is 805 nm, a wavelength at which absorption

of blood is independent of oxygenationof blood is independent of oxygenation 50%of the dye is excreted by the kidneys in 10 minutes, so 50%of the dye is excreted by the kidneys in 10 minutes, so

repeat measurements is possiblerepeat measurements is possible

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ThermodilutionThermodilution

The indicator is The indicator is cold – salinecold – saline, injected into the right atrium using , injected into the right atrium using a cathetera catheter

Temperature change in the blood is measured in the pulmonary Temperature change in the blood is measured in the pulmonary artery using a thermistorartery using a thermistor

The temperature change is inversely proportional to the amount of The temperature change is inversely proportional to the amount of blood flowing through the pulmonary arteryblood flowing through the pulmonary artery

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Measuring Cardiac OutputMeasuring Cardiac Output

Several methods of measuring cardiac output In the Fick method, the indicator is OSeveral methods of measuring cardiac output In the Fick method, the indicator is O 22; consumption is measured by a ; consumption is measured by a

spirometer. The arterial-venous concentration difference is measure by drawing simples through catheters placed in an spirometer. The arterial-venous concentration difference is measure by drawing simples through catheters placed in an artery and in the pulmonary artery. In the dye-dilution method, dye is injected into the pulmonary artery and samples are artery and in the pulmonary artery. In the dye-dilution method, dye is injected into the pulmonary artery and samples are taken from an artery. In the thermodilution method, cold saline is injected into the right atrium and temperature is taken from an artery. In the thermodilution method, cold saline is injected into the right atrium and temperature is measured in the pulmonary artery.measured in the pulmonary artery.

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Electromagnetic Electromagnetic FlowmetersFlowmeters Based on Faraday’s law of induction that a conductor that moves Based on Faraday’s law of induction that a conductor that moves

through a uniform magnetic field, or a stationary conductor placed through a uniform magnetic field, or a stationary conductor placed in a varying magnetic field generates in a varying magnetic field generates emfemf on the conductor: on the conductor:

When blood flows in the When blood flows in the vessel with velocity vessel with velocity uu and passes through the and passes through the magnetic field magnetic field BB, the , the induced emf induced emf ee measured measured at the electrodes is.at the electrodes is.

L

de0

LBu

For uniform B and uniform velocity profile u, the induced emf is e=BLu. Flow can be obtained by multiplying the blood velocity u with the vessel cross section A.

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ElectromagneticElectromagneticFlowmeter ProbesFlowmeter Probes

• Comes in 1 mm increments for 1 ~ 24 mm diameter blood vessels

• Individual probes cost $500 each

• Made to fit snuggly to the vessel during diastole

• Only used with arteries, not veins,

as collapsed veins during diastole lose contact with the electrodes

• Needless to say, this is an INVASIVE measurement!!!

• A major advantage is that it can measure instantaneous blood flow, not just average flow

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Ultrasonic FlowmetersUltrasonic Flowmeters

Based on the principle of measuring the time it takes for an Based on the principle of measuring the time it takes for an acoustic wave launched from a transducer to bounce off red blood acoustic wave launched from a transducer to bounce off red blood cells and reflect back to the receiver.cells and reflect back to the receiver.

All UT transducers, whether used for flowmeter or other All UT transducers, whether used for flowmeter or other applications, invariably consists of a piezoelectric material, which applications, invariably consists of a piezoelectric material, which generates an acoustic (mechanical) wave when excited by an generates an acoustic (mechanical) wave when excited by an electrical force (the converse is also true)electrical force (the converse is also true)

UT transducers are typically used with a gel that fills the air gaps UT transducers are typically used with a gel that fills the air gaps between the transducer and the object examinedbetween the transducer and the object examined

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Near / Far FieldsNear / Far Fields Due to finite diameters, UT transducers produce Due to finite diameters, UT transducers produce

diffraction patterns, just like an aperture does in optics.diffraction patterns, just like an aperture does in optics. This creates near and far fields of the UT transducer, in This creates near and far fields of the UT transducer, in

which the acoustic wave exhibit different propertieswhich the acoustic wave exhibit different properties The near field extends about The near field extends about ddnfnf=D=D22/4/4λλ, where , where DD is is

the transducer diameter and the transducer diameter and λλ is the wavelength. is the wavelength. During this region, the beam is mostly cylindrical During this region, the beam is mostly cylindrical (with little spreading), however with nonuniform (with little spreading), however with nonuniform intensity.intensity.

In the far field, the beam diverges with an angle In the far field, the beam diverges with an angle sinsinθθ=1.2 =1.2 λλ/D, /D, but the intensity uniformly attenuates but the intensity uniformly attenuates proportional to the square of the distance from the proportional to the square of the distance from the transducertransducer

Higher frequencies and larger transducers should be used for nearfield operation. Typical operating frequency is 2 ~ 10 MHz.

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UT FlowmetersUT Flowmeters

Zero-crossingdetector / LPF

Determine direction

High acoustic impedance material

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Transit time flowmetersTransit time flowmetersEffective velocity of sound in blood: velocity of sound (c) + velocity of flow of blood averaged along the path of the ultrasound (û)

û=1.33ū for laminar flow, û=1.07ū for turbulent flowū: velocity of blood averaged over the cross sectional area, this is differentthan û because the UT path is along a single line not over an averaged of cross sectional area

Transit time in up/down stream direction:

Difference between upstream and downstream directions

cosˆvelocityconduction

distance

uc

Dt

2222

cosˆ2

)cosˆ(

cosˆ2

c

uD

uc

uDt

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Transit Time Transit Time FlowmetersFlowmeters

The quantity ∆T is typically very small and very difficult to measure, particularly in the presence of noise. Therefore phase detection techniques are usually employed rather then measuring actual timing.

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Doppler Doppler FlowmetersFlowmeters

The Doppler effect describes the change in the frequency of a The Doppler effect describes the change in the frequency of a received signal , with respect to that of the transmitted signal, received signal , with respect to that of the transmitted signal, when it is bounced off of a moving object.when it is bounced off of a moving object. Doppler frequency shiftDoppler frequency shift

c

uff od

cos2

Speed of sound in blood(~1500 m/s)

Angle between UT beamand flow of blood

Speed of blood flow(~150 cm/s)

Source signal frequency

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Doppler Doppler FlowmetersFlowmeters

c

ufF s )cos(cos

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Problems Associated withProblems Associated withDoppler FlowmetersDoppler Flowmeters

There are two major issues with Doppler flowmetersThere are two major issues with Doppler flowmeters Unlike what the equations may suggest, obtaining direction Unlike what the equations may suggest, obtaining direction

information is not easy due to very small changes in frequency information is not easy due to very small changes in frequency shift that when not in baseband, removing the carrier signal shift that when not in baseband, removing the carrier signal without affecting the shift frequency becomes very difficultwithout affecting the shift frequency becomes very difficult

Also unlike what the equation may suggest, the Doppler shift is Also unlike what the equation may suggest, the Doppler shift is not a single frequency, but rather a band of frequencies not a single frequency, but rather a band of frequencies becausebecause

Not all cells are moving at the same velocity (velocity profile Not all cells are moving at the same velocity (velocity profile is not uniform)is not uniform)

A cell remains within the UT beam for a very short period of A cell remains within the UT beam for a very short period of time; the obtained signal needs to be gated, creating side time; the obtained signal needs to be gated, creating side lobes in the frequency shiftlobes in the frequency shift

Acoustic energy traveling within the beam, but at an angle Acoustic energy traveling within the beam, but at an angle from the bam axis create an effective ∆from the bam axis create an effective ∆θθ, causing variations , causing variations in Doppler shiftin Doppler shift

Tumbling and collision of cells cause various Doppler shiftsTumbling and collision of cells cause various Doppler shifts

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Directional DopplerDirectional Doppler

Directional Doppler borrows the Directional Doppler borrows the quadrature phase quadrature phase detectordetector technique from radar in determining the speed technique from radar in determining the speed and direction of an aircraft.and direction of an aircraft.

Two carrier signals at 90º phase shift are used instead of a Two carrier signals at 90º phase shift are used instead of a single carrier. The +/- phase difference between these single carrier. The +/- phase difference between these carriers after the signal is bounced off of the blood cells carriers after the signal is bounced off of the blood cells indicate the direction, whereas the change in frequency indicate the direction, whereas the change in frequency indicate the flowrateindicate the flowrate

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Directional DopplerDirectional Doppler

(a) Quadrature-phase detector. Sine and cosine signals at (a) Quadrature-phase detector. Sine and cosine signals at the carrier frequency are summed with the RF output the carrier frequency are summed with the RF output before detection. The output C from the cosine channel before detection. The output C from the cosine channel then leads (or lags) the output S from the sine channel if then leads (or lags) the output S from the sine channel if the flow is away from (or toward) the transducer. (b) the flow is away from (or toward) the transducer. (b) Logic circuits route one-shot pulses through the top (or Logic circuits route one-shot pulses through the top (or bottom) AND gate when the flow is away from (or bottom) AND gate when the flow is away from (or toward) the transducer. The differential amplifier toward) the transducer. The differential amplifier provides bi-directional output pulses that are then provides bi-directional output pulses that are then filtered.filtered.

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How are Blood Cells usually counted?

1) Usually by two well established methods: Microscopy and

Coulter counting. 2) Microscopy is more labor intensive but

is better at identifying different types of similar cells. 3) The Coulter Counting method lends

itself to automation as well as being paired up with flow

cytometry.

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Coulter Counter

1. Coulter Counter, though well grounded in the hematology

field, has some issues: It requires the use of saline as diluent It clogs

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SPOS

2 The SPOS method is a technique 2. particle counting with a

size range that allows the counting of the various blood cells,

but because it is an optically based technique: It does not require the use of saline The optical flow cell is not prone to clogging It can be paired with dilution systems It has a broader size range that can extend its use

beyond counting blood cells

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Cont..Cont..

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An SPOS result for a blood cell fraction

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Autodilution

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Cont. . Cont. .

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Using a Counting Chamber:Using a Counting Chamber:

For microbiology, cell culture, and many For microbiology, cell culture, and many applications that require use of suspensions of cells applications that require use of suspensions of cells it is necessary to determine cell concentration. One it is necessary to determine cell concentration. One can often determine cell density of a suspension can often determine cell density of a suspension spectrophotometrically, however that form of spectrophotometrically, however that form of determination does not allow an assessment of cell determination does not allow an assessment of cell viability, nor can one distinguish cell types.viability, nor can one distinguish cell types.

A device used for determining the number of cells A device used for determining the number of cells per unit volume of a suspension is called a counting per unit volume of a suspension is called a counting chamber. The most widely used type of chamber is chamber. The most widely used type of chamber is called a hemocytometer, since it was originally called a hemocytometer, since it was originally designed for performing blood cell counts. designed for performing blood cell counts.

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ArrangmentArrangment