EET286 – Fall 2015 follow-up 2015-12-10

• 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

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 cord- connected equipment shall not exceed 500 uA with normal polarity and

the ground wire disconnected (if a ground wire is provided).

PSI KiloPascal cm of H2O mm of Hg atmosphere millibar

1 PSI = 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

1 millibar = 0.0147 0.1 1.02 0.75 0.0009 1

Pressure Conversions

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

ECG trace and display

Calibration (y axis):10 mm = 1 mV

Speed (x axis):25mm = 1 Second

|---- 25 mm (1 Second) ----------------------------------------------------------------------------------|

|---

- 10

mm

(1 m

illiV

olt)

----

----

---|

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 !

1) Line in (not shown here)2) Transform (only the output is shown here)3) Rectify (usually a 4-diode bridge)4) Filter (usually a big cap & a small cap)5) Regulate (often with 78xx & 79xx ICs on heat sinks)

Linear power supply(2) (3) (4) (5)

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

or “distributed capacitance”

Leakage current:

Leakage current is both capacitive, caused by intrinsiccapacitance between conductors; and resistive, causedby imperfect insulation.

Where does the leakage current go?

Open ground !

Where does the leakage current go now?

Test device measuringchassis leakage current:

“Applied Part” of medical equipmentas 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

Almostideal

Line is partially occluded

Air bubblesin the line

Troubleshooting invasive BP lines:

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 ofthe Swan-Ganz catheter:

Most used:

Manual determination of NIBP blood pressure :

NIBP Blood pressure determination by oscillometryi.e. the automated electronic method:

Pressure pulsations during oscillometry:

non-invasive blood pressure monitor

Quiz #3 recap

LR#1: Intra-aortic balloon pump (IABP) is inserted into descending AORTA (output of LEFT heart)

#3: IABP is typically used for 1-2 days

#6: Capnography is measurement of CO2.

Measured by how much IR (infrared) light is absorbed by the gas sample.

(to lung)

(from lung) (from lung)

(from body)

(to lung)

(from body)(TO body)

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 (time is shown as a counter-clockwise loop):

PEFR: Peak Expiratory Flow Rate:measures how fast a person can exhale (breathe out).PIFR: Peak Inspiratory Flow Rate FVC: Functional Vital Capacity (same as VC)

Pressure-Volume-FlowDiagrams

(X axis for these is time)

inhale

exhale

note

: Res

idua

l Vol

ume

is s

how

n on

the

right

sid

e(s

till p

art o

f Tot

al L

ung

Capa

city

– 6

lite

rs)

Respiratory Gasses • Inspired (inhaled) air: N2 79% O2 21%

• Expired (exhaled) air: N2 79% O2 16%CO2 5%

Blood Components

• Hemoglobin (hb without attached O2)

• 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

this ratio gives SpO2 in Pulse Oximetry