EET286 – Fall 2015 follow-up
• Four types of clinical equipment
• Power Connectors
• NFPA99 Chassis Leakage (touch) Current
• Human Heart & Cardiac Cycle
• Wiggers diagram
• Pressure Conversions
• Common Electronic Component Abbreviations
• Quiz #2 recap
• Quiz #3 recap
2015-12-10
Four types of clinical equipment
Monitoring:
Detects and displays physiologic data for the purposes of clinical observation.
Diagnostic:
Detects, displays, and records physiologic data in order to confirm or rule out a
disorder or disease.
Therapeutic:
Applies treatment in the form of energy or medication in order to treat a
disorder or disease.
Assistive:
Used as an accessory to facilitate a medical or surgical procedure.
Power Connectors
plug: male connector, furthest away from power source
outlet or receptacle: female connector providing power
NEMA: (U.S.) National Electrical Manufacturers Association
IEC: International Electrotechnical Commission
NEMA wire colors:
Hot – Black
Neutral – White
Ground – Green
IEC wire colors:
Hot – Brown
Neutral – Blue
Ground Green/Yellow
Screw colors on some connectors:
Hot – Gold
Neutral – Silver
Ground – Green
HOT (L1)
Neutral (L2)
Ground (earth)
NEMA colors: Black
White
Green
IEC colors:
Brown
Blue
Green/Yellow
connectors:
Gold
Silver
Green
NFPA99 Chassis Leakage (touch) Current
• 1999 edition
• 2005 edition
• 2012 edition
• 2015 edition
10.2.6* Touch Current – Portable Equipment. The touch current for cordconnected equipment shall not exceed 500 uA with normal polarity and
the ground wire disconnected (if a ground wire is provided).
Pressure Conversions
PSI
KiloPascal
cm of H2O
mm of Hg
atmosphere
millibar
1
6.89
70.3
51.7
0.068
68.9
1 KiloPascal =
0.145
1
10.19
7.5
0.0098
10
1 cm of H2O =
0.014
0.1
1
0.735
0.00097
1
1 mm of Hg =
0.019
0.133
1.36
1
0.0013
1.33
1 atmosphere =
14.7
101
1033
760
1
1013
0.0147
0.1
1.02
0.75
0.0009
1
1 PSI =
1 millibar =
Most useful conversions in bold
Manometers, two styles;
Pressure measured as a column of mercury:
•
•
•
•
closed end (contains vacuum)
measures atmospheric pressure
760 mmHg ‘normal’
higher atmospheric pressure =
higher number
• (pressure in outer space vacuum
would be 0 mmHg)
• open end (contains ambient
air pressure)
• measures applied pressure
• 0 mmHg is ‘unpressurized’ state
• higher applied pressure =
higher number
Common Electronic Component Abbreviations
(silk screened on circuit boards and printed on schematics)
B
BR
BT
C
CB
CR
CT
D
F
IC
J
K
L
LED
M
Q
R
S
SW
T
T
TP
U
VR
XTAL
battery
bridge rectifier
battery
capacitor
circuit breaker
diode
center tap of transformer
diode
fuse
integrated circuit (chip)
jack or jumper
relay
coil or inductor
light emitting diode
motor
transistor
resistor
switch
switch
terminal
transformer
test point
integrated circuit (chip)
voltage regulator
crystal
(rev 2015-12-01)
technical term is "reference designators"
|---- 10 mm (1 milliVolt) -----------|
|---- 25 mm (1 Second) ----------------------------------------------------------------------------------|
ECG trace and display
Calibration (y axis):
10 mm = 1 mV
Speed (x axis):
25mm = 1 Second
Pacemaker Modes:
Asynchronous: provides pulses at a fixed rate
Demand (or ‘Synchronous’): provides pulses when the heart fails to beat
Rate-Modulated: provides pulses based on the
heart’s current activity
Defibs for Cardioversion
• The use of a small energy pulse from a defibrillator to convert an
non-lethal arrhythmia (eg atrial flutter) to a normal sinus rhythm
• Delivers a pulse about 30ms after the peak of the R-wave,
synchronized by the defibrillator
• Modern units can discriminate the R-wave from the T-wave or noise
spikes
Timing of cardioversion pulse
Do NOT cardiovert across the T-wave !
Linear power supply
(2)
(3)
(4)
(5)
1)
2)
3)
4)
5)
Line in (not shown here)
Transform (only the output is shown here)
Rectify (usually a 4-diode bridge)
Filter (usually a big cap & a small cap)
Regulate (often with 78xx & 79xx ICs on heat sinks)
from Electrical Safety presentation (class 6) CORRECTED:
(per NFPA-99, 2012 edition)
Resistance of Ground wire of power cord: 500 milliOhms (500mΩ or .5Ω)
Leakage current at the chassis: NC (normal condition) 100 microAmps (100 μA)
SFC (Single Fault Condition, e.g. open ground) 500 microAmps (500 μA)
Leakage current for any one patient contact lead to ground:
10 μA with ground closed, 50 μA with ground open.
Leakage current for each patient contact lead to any other lead:
10 μA with ground closed, 50 μA with ground open.
Leakage current for patient leads exposed to line voltage: 50 μA
Leakage current:
or “distributed capacitance”
Leakage current is both capacitive, caused by intrinsic
capacitance between conductors; and resistive, caused
by imperfect insulation.
Where does the leakage current go?
Open ground !
Where does the leakage current go now?
Test device measuring
chassis leakage current:
“Applied Part” of medical equipment
as defined by the IEC standard 60601-1:
Type B: Applied parts that are generally not conductive and can be
immediately released from the patient. May be grounded.
eg: Non-invasive BP monitors [think: Body]
Type BF: Devices that have direct contact with the patient, or parts that
have long term contact with the patient.
eg: ECG monitors
[think: Body, Floating (ground)]
Type CF: Applied parts that have direct contact with the heart.
eg: Invasive pressure monitors, defib paddles
[think: Cardiac Floating (ground)]
ONE of these ratings should be present on a medical device
If ‘Defib Proof’, ONE of these
Troubleshooting invasive BP lines:
Almost
ideal
Air bubbles
in the line
Line is
partially occluded
Damping in any oscillating system:
Damping is an effect on any oscillating system that reduces
or restricts its oscillations. In a mechanical system, damping is
produced by drag in the system. In a fluid system, damping is
caused by viscosity. In an electronic system, damping is caused
by impedance.
Undamped:
The system oscillates at its natural resonant frequency.
Critically damped:
When disturbed, the system returns to equilibrium quickly, without oscillation.
Overdamped:
When disturbed, the system returns to equilibrium without oscillating.
Underdamped:
When disturbed, the system oscillates, but the amplitude decreases to zero.
Swan-Ganz catheter (in ‘right’ heart)
Starts here
Ends up ‘wedged’ here or here
Swan-Ganz Catheter –
From the Right Atrium through the Right Ventricle, into the Pulmonary Artery
Pressure waveforms during insertion of
the Swan-Ganz catheter:
Most used:
Manual determination of NIBP blood pressure :
NIBP Blood pressure determination by oscillometry
i.e. the automated electronic method:
Pressure pulsations during oscillometry:
non-invasive blood pressure monitor
Quiz #3 recap
R
#1: Intra-aortic balloon pump (IABP) is inserted
into descending AORTA (output of LEFT heart)
L
(from body)
#3: IABP is typically used for 1-2 days
(TO body)
(to lung)
(from lung)
(from body)
(to lung)
(from lung)
#6: Capnography is measurement of CO2.
Measured by how much IR (infrared) light is
absorbed by the gas sample.
Question #7:
Deep breath
(or sigh)
normal breathing
exhaling as much as you can
this much air always stays in your lungs
note: TLC is often shown as 6 liters, which is normal for a 75 kg (165 #) person.
80 ml per kg of body weight (as shown here) is more accurate.
Question #14:
Flow-Volume Loop
exhale
inhale
PEFR: Peak Expiratory Flow Rate:
measures how fast a person can
exhale (breathe out).
PIFR: Peak Inspiratory Flow Rate
note: Residual Volume is shown on the right side
(still part of Total Lung Capacity – 6 liters)
(time is shown as a counter-clockwise loop):
FVC: Functional Vital Capacity (same as VC)
Pressure-Volume-Flow
Diagrams
(X axis for these is time)
Respiratory Gasses
• Inspired (inhaled) air:
• Expired (exhaled) air:
N2 79%
N2 79%
O2 21%
O2 16%
CO2 5%
Blood Components
• Hemoglobin (hb without attached O2)
this ratio gives SpO2 in Pulse Oximetry
• Oxyhemoglobin (hb with attached O2)
• Carboxyhemoglobin (hb with attached CO, Carbon Monoxide) gives inaccurate
SpO2
• Methemoglobin (pron: MET-hemoglobin) cannot bind to O2 and gives inaccurate SpO2