2. Biological signals & measurements Flashcards
Plasma osmolarity formula
what is it & define
Normal rang
2(Na+K) + Gluc + Urea
Measure solute concentration, numbe osmole solute/ L solution
285-295
ffected by temperature and pressur
Osmolality
Measure cocentration per Kg
independent of temperature and pressure
Osmolar gap
Measured serum osmolaLity − calculated osmolaRity
Raised
excess alcohols, lipids and proteins in blood.
Osmometers use
Colligative properties - depression freezing point / vapour pressure
Anion Gap calculation
(Na + K) - (Cl + bic)
Causes High AG
Ketoacid overproduction (diabetes, alcohol, starvation)
Lactic acid overproduction
Inability to excrete acids (sulfate and phosphate) secondary to acute kidney injury
Poisoning with salicylates, ethylene glycol, methanol, paraldehyde and propyl alcohol.
Dehydration
ECG
Standard speed & corresponds
standard calibration
PR
Q
QT
S-T
during the isoelectric phase between the S and T waves, the intracellular potential in ventricular muscle cells is
25mm/sec
1mm correspond 0.04s
0.1mV = 1mm
.12-.2s P wave to the start of the QRS complex
0.12 seconds.
The Q-T interval is measured from the start of the QRS complex to the end of the T wave.
It approximates to the ventricular refractory period and is normally 0.42 seconds.
S-T segment is measured from the end of the QRS complex to the start of the T wave.
Positive w/ regards to interstitial
Higher frequency response limit in ECG
Low pass - high freq filter set 40 /100/150hz accurate assess ST QRS morph Tacht
High pass filter
Low freq - set 0.05Hz
Low limit
Improves assess P T ST segmend
ecg electrodes
how is there accuracy reduced
inproved
signal arrives = current
cause chem change surface - inaccuracies second altered impedance
inaccuracy resting skin - impedence vartion - moisture
potential generation
Inaccuracy reduced - silver electrode contact cl ion in gel solution
large electrode surface area reduces inaccuracy
highest acoustic impedance between
boundary fat and bone
whats acoustic impedance
resistance to US beam occur tissue
spread sound wave density tissue
Electrical potential gen
Pacemaker - pulse duration
1ms deliver potent 4v
Nerve stimulator where are electrodes
neg electrode - over nerve
pos electrode more proximal
Dose of Nerve stimulator
60mA - nerve stim - supra-max stim (10% > threshold)
DBS
Two burst sep .75s
each burst - three .2ms stimuli - sep 20ms (50hz)
TOF
4 square wave lasting .2ms
rate 2hz
advantage of low frequency filter
low frequency = high pass filter
signal above threshold allowed pass
set .5hz
stable baseline reducin resp and body movement artefacts
also enhance rep p and t wave morphology - allow anal st seg
Greatest attenuation difference
water .0002
lung 40
1mmHg = how many cm h2o
1.4cm h20
1cm h2o = how many mmhg
.76mmHg
Oscilloscope -
what useful for
Cathode ray tube
Useful for high freq signal
Can be used to monitor ABP from transducer
may be used to plot flow volume loops
has an advantage over the galvanometer - negligible inertia
electron beam from hot cathode
Phase of a sine wave
refers to different angles wave cross lines
describe degrees
Large amplitude light
= bright light
Hertz is unit for
cycle per second
derive si frequncy
Wavelength sine wave
distance between two corresponding point in cycles
amplitude of wave
Distance horizontal line to peak of wave
Bandwith of an amplifier
Range frequency - constant
enables rejection of some interference
ra
Differential amplifer
gain amplifeier
Work Common mode rejection
only difference in signal recorded not signal common both
1
used eeg
gain amplifer measure on log scale
it is - ratio output voltage to input volt
measure bel
TEG normal
R 20-30 (reaction time) start test fibrin form
K time 8-15mm clot kinietc begin clot until apmlit reach 20mm
A 30-47 angle = Line r value + 1 K
MA 50-60- agreatest amplitude measure clot stenth
Clot lysis index - amplit 30m % MA
TEG hypofibr
R low normal
K high
MA - low
A angle low
Poor plt fxn
R low
K low
MA low
A angle low near normla
Basic blood gas analsyer
Clark electrode + Severnighaus + pH
Clark - Oxygen tension
What does fuel cell measure
oxygen tension on anaes machine
Normal qt interval
.35-.43s
Lead 1 2 3
1 right => left arm
2 right arm => left leg
3 Left arm => left leg
Second heart sound heard where
what else happens at this wave
end of t wave
aortic pressure highest immed before t wave
If poorly compliant aline
aline
high systolic
low diastolic
if overcompliant
damped
sb= under
diastolic overread
ph 7.6 H ion
<30
aprox 13000 mmol h ion made day
Cathode clark
ph electrode ref
clarke
plat
ref mercury
Drift occurs
what are the types
whne over a period displayed value differes from true value
offset drfit occurs - dispayed value varies constant from true value
correct singe point calib
gradient - varies true diff amt at dif times
less rapidly
but 2 point calibration required
What uses EEG
BIS
Auditory evoked potential
Compressed spectral array
EEG waves
range 1-100uv
4 waves
a- normal parieto occip at rest
depressesd GA
B frontal
decrease with age
highest freq
(d y a B) low to high
Delta - children + sleep
Y sometimes abnormal
Ultrasound dopler effect
sound move closer velocity
wavelegnth
pitch
can we hear us
Sound move towards observer - velocity unchanged
- wavelength and freq vary inverseley
wavelength decreases, frequency increase
sound higher pitched
US - very high freq low singal wave too high for human ear
