ELFH exam course section questions Flashcards
How will the deflection appear on an ecg if the impulse is travelling away from the electrode?
negative deflection
(positive for towards)
what is the lead position for the chest leads on an ECG?
V1 = 4th intercostal right of sternum
V2 = 4th intercostal left of sternum
V4 = 5th intercostal mid clav line
V6 = 5th intercostal mid axillary line
V3 and V5 inbetween
what are the 3 lead types on an ECG?
limb leads - bipolar = lead 1 , 2, 3
limb leads - augmented/ unipolar = aVF, aVL, aVR
chest leads = precordal - view in horizontal plane
what is the normal cardiac axis?
-30 degrees to + 90 degrees
what is left axis deviation and right axis deviation as an angle?
>
- 90= RAD
-30 = LAD
what is the standard calibration for an ecg?
1mV / cm
25mm/s
what is seen in ecg for posterior ischaemia?
ST depression V1-V4
R>S in V1 and V2
upright T in V1 and V2
how is CM5 electrodes set up ? what is this mostly for?
red = manubrum
yellow = V5 position
green = neutral = anywhere but usually left clavicle
good for viewing left ventricle and diagnosing ischaemia
CM5 = clavicle manubrum V5
how is PR interval measured?
start of P to start of QRS
should be <0.2ms (5 small squares)
what are the 2 most common valvular lesions?
Mitral regurgitation
aortic stenosis
what happens to EDV and ESV in mitral regurgitation?
eventually dilation of heart and both of these volumes are increased
what murmur is heart in mitral regurgitation?
pan systolic
max at apex of heart
3rd heart sound sometimes
what ecg changes are seen in mitral regurgitation?
p mitrale
AF
LVH
how should you tailor your anaesthetic for mitral regurgitation?
Avoid bradycardia - increases the time for regurgitation
minimize vasoconstriction - to achieve good forward flow, a dilated peripheral circulation is required
Avoid a large increase in preload, because this can decompensate the heart
MR likes ‘Fast and Loose!’
how is compliance of heart affected in aortic stenosis? what else happens
narrowered valve, increased LV pressure, LVH
hypertrophy reduces compliance
this limits passive filling of the heart
now atrial systole has more significance
Myocardial O2 consumption increased
reduces blood flow through the coronary arteries because transmitted LV diastolic pressure acts as a Starling resistor and reduces the coronary perfusion gradient. The subendocardium is particularly vulnerable to ischaemia
what murmur is heard in aortic stenosis?
harsh ejection systolic
what are the ecg changes associated with LVH?
The voltage criteria are met if an R wave in either lead V5 or V6 exceeds 25 mm or if the sum of the tallest R wave (in V5 or V6) with the deepest S wave (in V1 or V2) exceed 35 mm
Left axis deviation
T wave inversion (in V5 or V6) with or without ST depression indicates a ‘strain’ pattern
prolonged QRS is another feature
what is the area of a normal aortic valve?
2.5 to 3.5 cm3
how can aortic stenosis be graded?
clinical severity
ECHO
- cross sectional area
- gradient
how is severe and critical aortic stenoiss classified ?
severe = gradient >40mmHg , aortic area <1cm3
critical = gradient >80mmHg, aortic area <0.5cm3
valve area is a more useful indicator, gradient may not always be high.
how would you manage someone anaesthetically with aortic stenosis?
slow and tight
slow HR - less demand ,tachycardia will reduce diastolic time and coronary flow.
preserve SVR - to preserve gradient for coronary filling (the inflow pressure for coronary perfusion in diastole is the aortic diastolic pressure). also maintains preload.
when are J waves on an ecg seen?
hypothermia
hypercalcaemia
massive head injury and sub-arachnoid haemorrhage.
what degrees are lead 1, 2, 3 on the axis?
Lead II is at 60°, Lead I is termed 0° and Lead III at +120°.
what is the regurgitant fraction in mitral regurgitation?
the ratio of the flow that leaves the left ventricle and enters the left atrium versus that which enters the aorta.
A ratio of 0.3 indicates mild regurgitation and 0.6 indicates severe pathology.
describe what happens from sitting to standing…
gravity - sudden pooling of blood in capacitance vessels
drop of preload,
drop in SV
CO and BP fall
detected by barorecptors - increase in sympathetic tone
vasoconstriction, increase HR, increase conttractility
what are the classes of haemorrhage?
class I to IV
class I = 15% blood loss. not many clinical signs - anxiety maybe
class II = 15 to 30%. tachycardia, tachypnoea, urine output <0.5ml/kg/hr. narrow pulse pressure
class III = 30-40% = same as above but more marked. now drop in BP , may get confusion etc
class IV >40%
weak pulse, anuria, reduced consciousness
how does the body respond to blood loss?
vasoconstriction e.g. to kidney and guts
sympathetic stimulation to aid this and improve CO
fluid translocation from interstitium = 0.25ml/kg/min (due to drop in hydrostatic pressure via starling)
RAAS - due to reduced renal perfusion
↑angiotensin II (potent vasoconstrictor)
↑aldosterone (renal retention of Na)
Anti-diuretic hormone (ADH) - thirst, water conservation and vasoconstriction
later
- EPO and reticulocytosis
- plasma protein synthesis
how much of normal saline stays intravascular?
750 mls traverse into the ISF
250 mls remain in IVF.
how much 5% glucose goes into the intravascular compartment?
2/3 enters the intracellular fluid compartment
1/3 remains in the extra cellular compartment, of which
ISF (75%)
IVF (25%)
what is valsalva?
forced expiration against closed glottis
increases intrathoracic pressure by 40mmHg
illustrates autonomic control of both HR and BP
what are the phases of valsalva?
phase 1
Squeeze on intra-pulmonary vessels
Return of more blood to left atrium
Increased preload results in increased SV
Direct transmission of intra-thoracic pressure onto aorta
phase 2
Continued strain leads to:
Impaired return of blood entering thorax
Reduced CO and BP
Baroreceptors sense reduced BP
Sympathetic compensation increases HR and peripheral vasoconstriction
(overall fall in BP, compensated for by rise in HR)
phase 3
Release of strain leads to:
Loss of squeeze on intra-pulmonary vessels. This temporarily reduces return of blood to heart, BP falls further
Too brief an interval for HR changes
phase 4:
Venous return to left atrium normalizes
CO now delivered onto a highly vasoconstricted peripheral circulation (from Phase II)
Overshoot of BP sensed by carotid sinus baroreceptors
Reflex vagal slowing of heart rate
look up graph - valsalva phases for HR and BP
what are the uses of valsalva?
test autonomic function
hear murmurs
stop SVT
unblock ears
what is the valsalva ratio?
max HR in phase 2 / max HR in phase 4
(can also use RR interval rather than HR)
A ratio of >1.5 indicates competent functioning of the autonomic cardiac control.
what would you expect age to do to the valsalva ratio?
reduced
age blunts baroreceptor response.
what would an alpha and beta blocker do to the phases of valsalva?
alpha blocker - in phase 2, there will be less compensation of vasoconstriction by the baroreceptor reflex. hence HR will have to compensate more = this leads to increased HR in phase 2. in phase 4 because of the lag time, there will be an increased over shoot in BP (due to increase in HR)
B blocker - less HR response in phase 2 so lower HR. hence in phase 4, the BP overshoot will be less because less effected by HR and lag.
how much fluid translocates from interstial fluid to IVF in shock?
0.25ml/kg/min
what are sympathetic pre and post ganglionic fibres?
pre - myelinated B fibres, short, release Ach (nACh)
post - unmyelinated , long, release NA
what receptors and NT do blood vessels within skeletal muscle recieve?
typically have post-ganglionic sympathetic cholinergic transmission (on to muscarinic receptors)
what do renal vessels sympathetic fibres release
and some renal vessels have dopaminergic transmission (D1 receptors).
how can valsalva be used for diagnosis of HOCM?
Almost all cardiac murmurs decrease in intensity during a Valsalva manoeuvre;
apart from the murmurs associated with mitral valve prolapse and hypertrophic cardiomyopathy.
what happens to blood volume in lungs and liver from lying to standing?
DROPS
The lungs and liver both act as reservoirs of circulating volume. When a change in posture or haemorrhage occurs then sympathetic stimulation triggers venoconstriction which mobilizes blood in these areas into the effective circulating volume
Venoconstriction not vasoconstriction
where are volureceptors located?
Volureceptors are located in the right atrium and great veins.
what is the threshold for osmoreceptor activation?
1-2 %
does a transfusion of 1L 0.9% saline trigger volureceptor activation?
no, they are only triggered by 8-10% change
0.9% saline add 250ml which is not enough
when is aortic blood flow lowest in cardiac cycle?
early diastole
when is aortic pressure highest?
mid systole
how much does atrial contraction contribute to ventricular filling
normal HR - 20%
tachycardia - 40%
how does the QRS relate to systole?
The QRS complex occurs immediately before isovolumetric contraction.
how to baroreceptors respond to low BP
reduced discharge
(increased discharge when stretched)
what pancreatic hormone is increased in acute haemorrhage?
glucagon
- increases with sympathetic output
how much does PVR fall at birth in a fetus?
by more than 80%
how long for the ductus arteriosus to close?
48 hours
(similarly FO takes atleast 48 hrs)
how does arteriolar and venous constriction affect starling forces?
arteriolar vasoconstriction - less flow through capillary bed , less fluid into interstitial space
venous = back flow so increases fluid out
what does the a wave correspond to on JVP? what causes an increase and decrease in this?
atrial contaction
increase = cannon a = tricispid stenosis, complete HB or junctional rhythms
reduced in AF
what change does tricuspid regurgitation cause on JVP?
v wave is larger
v wave is caused by atrial filling during ventricular systole.
how does perfusion of right and left coronary artery differ?
Unlike the left ventricle, the right ventricle receives most perfusion during systole due to its lower wall pressures.
which major organ has a high A-v O2 difference / O2 extraction?
cardiac
what is the preferential route from right to left ventricle for wave of depolarisation to take?
bachmanns bundle
a.k.a anterior interatrial band.
how does hypovolaemia affect valsalva?
reduced arterial presure in phase 2 is more exagerated
how is valsalva different in those with neuropathy?
less HR drop in phase 4
e.g. 20% of diabetic s
how does valsalva affect murmur of AS?
most murmurs decrease in intensity with valsalva
except MR and HOCM - increase
what is the max wavelength absorbed by oxy and deoxy Hb?
oxy = 940nm
deoxy = 660nm
what sats does methamohaemaglobin and carboxyHb read?
methaemo = 85%
carboxy = high sats
can fetal Hb alter saturation accuracy of pulse oximeter?
no
how much is the pulsatile component of the waveform in pulse oximetry?
2 %
what is the functional saturation?
Functional saturation is the ratio of O2HB to (O2Hb + reduced Hb)
includes other Hbs
in pulse oximetry what do motion artifacts do?
increase high ac to dc signal ratio
Motion will produce an increase in a.c. components however this is noise and therefore the signal to noise ratio will be lower
can external lighting effect the accuracy of pulse oximetry?
Yes
although partly accounted for by only including pulsatile portion
which O2 analysing electrode requires a battery?
CLARK
‘fuel already has fuel’
what is an example of a polarographic electrode?
clark
what gas can affect accuracy of the fuel cell?
N20
which has faster response time - polarographic or paramagnetic
paramagnetic
what type of analyser is used in most blood gas analaysers for oxygen?
polarographic - clark
how does a co-oximeter work?
A CO-oximeter measures the concentrations of different haemoglobins and calculates the oxygen saturation from the relevant percentages
INDIRECT.
what is measured DIRECTLY by blood gas analyser?
H+
PaO2
these in turn can give
pH
CO2 - sauvinghaus
without temp compensation in a blood gas machine what will hypothermic patients read as their PaO2?
high PaO2 reading
in hypothermic patient - they will be able to carry more O2 for a specific partial pressure OR at a specific O2 their PP will be lower.
hence now heat the sample, more O2 will leave - higher Pp
how do air bubbles in a blood gas affect PaCO2?
lowers it
air will have less CO2
what happens if the blood is left at room temperature before a blood gas analysis?
cells metabolise O2 - lowers PaO2
increased CO2 –> lowers pH
what happens if heparin is left in sample before blood gas analysis?
lower pH - heparin is acidic
for oxygen analysis in a blood gas analyser, what is the electrodes and solution normally consist of?
anode is typically silver
cathode platinum
electrolyte solution is a potassium chloride solution
this is a clark electrode - seen in blood gas analysers
(A fuel cell contain a lead anode and gold mesh cathode - not usually in a blood gas analyser)
what is faster the clark or fuel cells?
Clark - polarographic
(think clark is battery driven so likely to be faster)
what is the main method for analysing anaesthetic gases? what other methods are there?
Infrared Absorption Spectrophotometry.
others - Photoacoustic spectrometry, Raman scattering, mass spectrometry and UV absorption
which gases have absorption spectrum similar to CO2 and can interfere with infrared absorption spectrophotometry ?
Water vapour, sevoflurane and nitrous oxide
= collision broadening
what wavelength of Infrared is used for CO2 absorption spectrophotometry?
4.3um
what is the isobestic point?
point of equal absorption of both OxyHb and deoxyHb = 805nm
and 580nm
what are refractometers?
typically used to measure vapour concentrations in gas mixtures by measuring the bending of light waves due to the change in gas composition.
They are used to calibrate vaporisers and measure vapour concentration INDIRECTLY
they themselves require calibration against known concs
define base excess
The base excess is the amount of strong acid required to return the pH of 1 litre of blood to 7.40 at a PCO2 of 5.3 kPa and 37°C
what is the range of wavelengths for visible light?
400 (blue) -700 (red) nanometers
what is the absorption spectra for most volatiles in infrared absorption spectroscopy?
volatile agents peaks close to 3.3 micrometres
(CO2 = 4.3um)
what is collision broadening?
when other gases are present, the collisions between gases alter the energy / wavelength each gas can absorb at that moment in time hence rather than a sharp absorption at one particular wavelength, there is a broader range.
e.g. CO2 alone - 4.3um
when in a mix with sevo, water and nitrous these gases also absorb some of this wavelenth and collide with CO2 so it absorbs other wavelengths
Collision broadening widens the range of wavelengths absorbed by CO2
what pressure does a mass spectrometer work at?
vacuum
how many electromagnetics in a mass spectrometer?
4
how are ions accelarated in mas spectrometry?
by the cathode plate
how are natural resonance and mass related?
natural resonance is inversely proportional to square root of mass
define fouriers transformation?
Fourier Transformation is a mathematical operation that deconstructs a complex signal (wave) into its constituent frequencies (vectors)
does blinding of a study reduce confounding variables?
no reduces bias
what can a control group recieve?
placebo
standard treatment
historical treatment
what is meant by intention to treat?
Intention to treat analyses data based on the initial treatment intended, rather than the treatment eventually given (eg if a patient dropped out of a study).
what is the relative and absolute risk reduction?
incidence of an event before and after
absolute risk reduction = after - before
relative risk reduction = ARR / before
e.g. sore throat incidence is reduced from 20% to 15% in group given a treatemtn
RRR = 5%
ARR = 5/20= 25%
can the power of a study depend on the statistical test used?
yes
can be used for both parametric and non-parametric
for normal distributed data what statisitical tests are used?
normally parametric
(can also use non-parametric)
for non-normal can only use non-parametric
what measure of central tendency is used in non normal distribution data?
MEDIAN
how is central tendancy measured in categorical data?
mode
what does a correlation coefficient of near 1 mean? i.e. r=1
association between 2 variables
it DOES NOT mean if one rises, the other rises
can correlation coefficient be used for both parameteric and non-parametric?
yes
what is the difference betweeen odds ratio and risk ratio?
Odds ratio is a ratio of two odds, while risk ratio is a ratio of two probabilities.
e.g.
risk ratio = probabilty of outcome in test group / probability of outcome in control group
odds ratio = odds of it occuring in test/ odds of it occuring in control
risk ratios are more intuitive
both measures of association
what is the formula for standard error of mean?
Standard error of the mean is the Standard Deviation divided by the square root of (n - 1)
is spearmans rank a parametric test?
no
what is eulers number?
base of natural logarithm
2.718
what type of graph would denitrogenation during induction give if plotted with time?
negative exponential i.e. wash out
if plot log N2 against time = straight line
name of graph for 1/x
rectangular hyperbola
what is the difference between the rectangular hyperbola and negative exponential?
The similarity between the two curves is that they both asymptote the x-axis. The difference is that the exponential curve meets the y-axis and the hyperbolic curve asymptotes the y-axis.
define time constant Tau..
It is the time required for a process to complete if it continued at its initial rate of fall, i.e. it is the tangent to the graph at time = 0
The time taken for the magnitude of the variable to fall to 37% of its initial value
or
The time to fall to 1/e or 1/eth of its original value.
how much of the process is complete in one time constant?
he process is 63% complete in one τ.
fallen to 37%
how much of a process is complete after 2 and 3 time constants?
86% after 2
95% after 3
can the Vd of a drug be greater than volume of the body?
yes - theoretical value
how is loading dose calculated with Vd?
loading dose = steady state conc x Vd
divide this by Bio availability for oral drugs.
oxygen can be toxic. how long before FiO2 of 1 will cause pulmonary changes?
12 hours
(for 0.8 FiO2 = 24hrs, 0.6 = 36 hrs)
it is toxic in dose dependant and time dependant effect
in hyperbaric conditions this is quicker e.g. at 2atm takes 6 hrs
what are the pulmonary complications of hyperoxia?
infiltration of inflammatory cells
atelectasis
ARDS like picture
later - fibrosis
how does high FiO2 promote atelectasis?
absorption atelectasis
secretions and blocked airway - promotes absorption of gas behind this without new ventilation
atelectasis reduces the FRC
what effect does O2 toxicity have in neonates?
Retinopathy of prematurity
Necrotising enterocolitis
Bronchopulmonary dysplasia
Intracranial haemorrhage
what are the neurological effects of hyperbaric O2?
At 2 atmospheres; paraesthesia, nausea, facial twitching, myopia, olfactory and gustatory disturbances
Above 2-3 atmospheres; convulsions may predominate
can convulsions happen from normobaric O2 therapy?
no
only at hyperbaric
when is FiO2 harmful i.e. what level?
anything more than 0.5
what 2 main pathology can HYPERbaric O2 therapy lead to?
pulmonary oedema - smith effect
convulsions - bert effect
what are the main factors that determine uptake of inhalation anaesthetic?
Alveolar fractional concentration
Blood:gas coefficient
Cardiac output
Alveolar:venous gradient
and conc/second gas effect
how is alveolar fraction of inhalation agent increased?
increase Fi Agent
increase ventilation rate
what other agent can cause concentration/ second gas effect?
Xenon
needs to be a non-potent agent used in high volumes
how does ventilation affect the second gas effect?
increases it
increases the alveolar conc and hence diffusion
how many isomers of GABA receptor are there?
over 30 -
responsible for the different effects of benzos e.g. a1 sedation, a2 anxiolysis, a3 muscle relaxation
what are the receptors subunits of GABA?
2a , 2b , g
what activates the NMDA receptor?
Glutamate and glycine are the natural co-ligands that bind to the receptor to open a central Ca2+ conducting pore.
ketamine, N20 and xenon all non-competitive antagonists
alcohol also effects NMDA - causes tolerance and withdrawal
what type of receptor is NMDA?
ionotrophic
what type of receptor is GABA B
metabotrophic
where are glycine receptors found?
brain stem
spinal cord
what is the equation for MAP?
MAP = SVR x CO
what does increasing after load do to the frank starling curve?
reduced peak and to the right
why can some ionotropic drugs e.g. B2 agonists cause drop in BP?
also affect peripheral B2
vasodilation
what are the effects of adrenaline pharmacodynamically?
A low-dose infusion has inotropic β effects
increasing dose increases α action
Diastolic blood pressure can fall due to β2-linked peripheral vasodilatation
what is the effect of dobutamine as a CVS drug?
Mainly stimulates β1-receptors with some β2- and α1-receptor action
Decreases left ventricular end diastolic pressure (LVEDP) via its action on peripheral β2-receptors (vasodilation)
B2 vasodilation also reduces preload
what is the action of isophrenaline
Is a potent β1- and β2-receptor agonist – increasing cardiac output but afterload/systemic vascular resistance can drop due to peripheral β2 action
what does aminophylline do to cardiac output?
increases
name some phosphodiesterase inhibitors…
enoximone and milrinone - cardioselective used as ionotropes
aminophylline / theophylline - non selective (has some cardio effects)
what is levosimendan?
Levosimendan increases myocyte sensitivity to Ca2+ by binding to troponin C.
used in severe acute HF
also causes peripheral vasodilation
what does digoxin do to intracellular calcium?
increases it.
blocks Na/K ATPase
hence less sodium out of cell
therefore less Ca/Na exchanger activity - which normally takes Ca out.
what receptors can be used by vasopressors
A1 adreno
vasopresin
what is action of noradrenaline?
predominantly a1
some b1
hence increases BP
Has a minor inotropic action which is offset by a baroreceptor reflex vagal response to the increased blood pressure
how can ephedrine be given?
orally or IV
does ephedrine cross the placenta?
yes
how do phenylephrine and metaraminol work?
a1 agonist
reflex brady
what receptor does vasopressin work on to exert vasopressor effects? what type of receptor is this?
V1 - Gq
which drug is dobutamine structurally similar too?
Dobutamine is structurally similar to isoprenaline
which ventricle is more sensitive to microshock from current?
right ventricle
what does the microshock induce in heart?
VF - no other arrythmias
what wires does the electricity in an operating theatre have?
line neutral and earth wires
not live
only a single phase is supplied to operating room
how can wires be protected from electrostatic interference?
The wires must be encased in a conductive NOT insulating layer
increasing distances - double the distance, will halve the interference
using lower frequency current - high frequencies, more interference
can screened leads protect from electromagnetic interference?
no
what is the difference between electrostatic and electromagnetic interference?
electromagnetic comes from magnet inducing current
electrostatic comes from imbalnces in charge
how is electromagnetic inference affected by distance betwen leads?
Magnetic field strength varies as the reciprocal of the separation SQUARED
what must the resistance of earth connection be?
less than 0.1 ohm
what must leakage of earth current be less than?
0.5mA
what earth is equiptment in hospitals connected too?
earth connection is the LOCAL earth and is NOT connected at or to the substation
what is an earth surge test in electricity?
Earth surge test requires that the local earth can carry a current of 25A for 5 seconds
2.5V
what is the star point in electricity?
the earth connection at the electrical substation
what is the difference between cutting and coagulation mode in diathermy?
cutting
- continuous
- high freq (400KHz)
- lower voltage (400 - 1K volts)
- higher power (>100Wats)
coag
- interrupted
- low freq (250kHz) , high voltage (9KV)
- lower power (<100watts)
blended - both
what frequency current does diathermy use?
v high frequency
up to 1 MHz
how does remi potency compare to fentanyl
similar
how much more potent is fentanyl than morphine?
100x
what is more lipid soluble - pethidine or alfentanil?
alfentanil
route for tramadol?
Oral
IV
what is main effect of tramadol?
5HT3/NA reuptake block
then u receptor
then anatagonist at Ach
morphine metabolism involves glucoronidation, what other pathways?
oxidation
demethylation
methylation
NOT Acetylation
is clonidine good orally?
yes - 100% BO
how is paracetamol converted to NAPQI?
oxidation
what filters are used in ECG monitoring and diagnostic mode?
monitoring mode =
high pass filter = 0.5Hz (allows signals higher than this)
low pass filter = 40Hz
diagnostic = 0.05 to 100Hz
what is main cause of pollution in paeds anaesthesia?
type of breathing circuit used
(the gas induction too but only for short time, a jackson rees modification of tee piece is open ended)
which blood gas analysers use voltmeter vs ammeter?
CO2/ pH = volt
oxygen e.g. clark and fuel - amp
How does mapelson F produce PEEP?
open ended bag , anaesthetist can close and open
NO APL valve
pin index systems…
O2 2,5
air 1,5
N20 3, 5
CO2 1,6
entanox 7
what does salbutamol do to lactate levels?
increase
i.e. after acute asthma treatment - hypoK and lactaemia
describe the cormak and lehane view..
Grade I – full view of the glottis.
Grade IIa – partial view of the glottis
grade 2b - only arytenoids.
Grade III – epiglottis only visible.
Grade IV – neither epiglottis nor glottis visible.
how does co-oximetry work?
takes blood sample
uses spectrophotometry to look at oxyHb, DeoxyHb, carboxyHb, methamoglobin
not in real time
not affected by skin colour (unlike pulse oximetry)
what is meant by the sensitivity of a pacemaker and the stimulation threshold?
Sensitivity is the minimum required myocardial voltage to be detected as a p wave.
The minimum output required to consistently capture a heart beat is known as the stimulation threshold.
what is the bainbridge reflex?
increase HR in response to atrial stretch
what is anrep efect?
increased contractility in response to afterload
what is the absolute humidty at 20, 37 degrees and 34 degrees
20 =17g/m3
37 = 44g/m3
34 = upper airways = 34g/m3
why is theatres kept at 50-60% humidity?
reduces heat loss via vapourisation
reduces risk of sparks from build up of static charge
higher values uncomfortable for staff
state methods of humification from least to most efficient?
Cold water bath
HME
Hot water bath
Bernoulli (gas driven) nebulizer
Ultrasonic nebulizer
what humidity can soda lime achieve?
29mg/L
form of passive humification
how many ports does HME filter have i.e. connections?
2 - 1x 15mm, 1x 22mm
+ sampling port for gas monitoring
what type of material does HME filter contain?
hygroscopic - absorbs moisture
how much does a HME increase resistance by?
0.1 to 2cmH20
