CET NHA Certified EKG Technician - Set 3 - Part 3

Correct Answer: Twenty-five millimeters per second

The standard EKG paper speed is twenty-five millimeters per second, which makes one small box equal to four hundredths of a second and one large box equal to two tenths of a second. The standard allows consistent measurement. Option a is incorrect because ten millimeters per second is far slower than the standard and would compress every waveform horizontally. No standard EKG protocol uses ten millimeters per second as the default recording speed. Option b is incorrect because fifteen millimeters per second is not a standard rate used in routine EKG recording. The recognized non-standard speeds are twelve point five and fifty, not fifteen, millimeters per second. Option c is incorrect because fifty millimeters per second is the double-speed setting used occasionally to spread out closely spaced complexes for waveform detail. Double speed is not the routine recording standard.

Correct Answer: Ten millimeters tall on the paper

At standard gain, one millivolt produces a deflection ten millimeters tall on the EKG paper. This is the basis for the standardization mark that should appear at the beginning of every recording. Option b is incorrect because five millimeters represents half-standard gain, which is used when amplitudes run off the paper such as in left ventricular hypertrophy. Half gain is a setting adjustment, not the standard. Option c is incorrect because twenty millimeters represents double-standard gain, used when amplitudes are very small and need amplification. Double gain is also an adjustment rather than the standard sensitivity. Option d is incorrect because two millimeters does not correspond to any standard gain setting on EKG machines. The recognized settings are five, ten, and twenty millimeters per millivolt, not two.

Correct Answer: The machine is at half-standard gain

A five-millimeter standardization mark indicates the machine is set to half-standard gain, used to keep large amplitude signals from running off the paper. Amplitude measurements on a half-gain tracing must be doubled for the true value. Option a is incorrect because standard gain produces a ten-millimeter standardization mark, not a five-millimeter mark. The shorter mark signals an adjustment away from the standard setting. Option b is incorrect because paper speed changes affect horizontal scaling, while the standardization mark height is determined by gain. Doubled paper speed does not produce a half-height calibration mark. Option d is incorrect because the half-gain tracing is valid for interpretation as long as the reader notes the gain setting and doubles measured amplitudes. Half gain is a deliberate adjustment, not a recording error.

Correct Answer: About zero point zero six to zero point ten seconds

A normal adult QRS duration falls between about zero point zero six and zero point ten seconds, with values above zero point twelve seconds considered wide. Wide QRS suggests delayed or altered conduction below the AV node. Option a is incorrect because less than zero point zero four seconds describes a single small box on the EKG, which is too narrow to capture a normal QRS complex. Such a short interval does not match adult QRS duration. Option b is incorrect because zero point twelve to zero point twenty seconds is the normal range of the PR interval rather than the QRS duration. The PR interval covers atrial depolarization plus AV node delay, not ventricular depolarization. Option c is incorrect because zero point twenty to zero point thirty seconds is too long for a normal QRS and would meet wide-complex criteria. Such durations occur in bundle branch blocks and ventricular rhythms, not in normal conduction.

Correct Answer: Zero point twelve to zero point twenty seconds

The normal adult PR interval is zero point twelve to zero point twenty seconds, equivalent to three to five small boxes on the EKG. Values outside this range suggest preexcitation or first-degree AV block. Option b is incorrect because less than zero point ten seconds is shorter than the normal range and may indicate preexcitation syndromes like Wolff-Parkinson-White. Such short intervals fall below the normal floor of zero point twelve. Option c is incorrect because zero point twenty to zero point forty seconds exceeds the upper limit of the normal range. Values above zero point twenty seconds meet the criteria for first-degree AV block rather than a normal PR interval. Option d is incorrect because greater than zero point forty seconds is well beyond any normal range and would represent significant conduction delay. Such intervals are abnormal and clearly meet block criteria rather than normal values.

Correct Answer: The gridded thermal-coated side up

Thermal paper has a heat-sensitive coating on one side, typically the gridded side, which must face the heated stylus to produce a visible tracing. Loading the paper upside down results in blank or partially printed recordings. Option a is incorrect because thermal paper is not symmetrical and has a clear difference between the coated and uncoated sides. Each side produces a different result, so orientation matters during paper loading. Option b is incorrect because the blank uncoated side facing the stylus produces no visible tracing because the heat has no chemistry to react with. A blank tracing is exactly what this loading error produces in practice. Option d is incorrect because the colored back side has no thermal coating and does not produce a tracing when heated. Pointing the back side at the stylus is just another way of describing the same loading error.

Correct Answer: A disconnected electrode or broken lead wire

A single flat lead on a tracing where other leads look normal almost always points to a disconnected electrode or a broken lead wire rather than a clinical finding. The technician should inspect and rerecord. Option a is incorrect because cardiac asystole would produce a flat line on every lead rather than just one. A single-lead flat line in an otherwise normal tracing cannot represent global electrical silence. Option c is incorrect because doubled paper speed affects horizontal spacing of waveforms across all leads, not the amplitude of a single lead. A speed change would not produce a flat line on one lead alone. Option d is incorrect because gain set too low would reduce amplitude on every lead, not flatten just one. Gain effects are systemic across the tracing rather than confined to a single lead.

Correct Answer: Wipe leads with facility-approved disinfectant

Wiping leads with a facility-approved disinfectant balances effective surface decontamination with safety for the rubber and plastic components. The technician should follow the manufacturer's instructions for use and the required wet contact time on the label. Option a is incorrect because submerging leads in bleach is destructive to most cable assemblies and is not how reusable EKG leads should be processed. Immersion can damage internal wiring and connectors permanently. Option b is incorrect because spraying cleaner directly onto a machine screen risks fluid entering the electronics and damaging the device. Cleaning agents should be applied to a wipe first, then to the surface. Option c is incorrect because skipping cleaning between patients allows organisms to transfer on the leads even when no soil is visible. Visible appearance is not a reliable indicator of microbial contamination on shared equipment.

Correct Answer: Hang or coil loosely without sharp bends

Hanging lead wires or coiling them loosely without sharp bends preserves internal conductor integrity and prolongs lifespan. Tight coils and kinks can damage the internal wiring and cause intermittent signal loss during use. Option b is incorrect because tightly coiling and taping lead wires creates sharp bends that stress and eventually break the internal conductors. Tidy appearance does not justify equipment damage. Option c is incorrect because knotting leads concentrates mechanical stress at the knot point and damages the internal wires. Knots also need to be untangled before each use, which slows setup and frustrates staff. Option d is incorrect because wrapping leads tightly around the cable trunk creates the same kind of stress that damages internal conductors over time. The trunk is a storage convenience that does not call for tight wrapping of leads.

Correct Answer: Sixty hertz line frequency

The AC interference filter on U.S. EKG machines is typically set to sixty hertz to match the local power line frequency. This setting reduces the regular sine-wave artifact that nearby electrical equipment can introduce into the tracing. Option a is incorrect because twenty-five hertz is not a line frequency used in the United States or other major systems. AC line frequencies are standardized internationally at fifty or sixty hertz, not twenty-five. Option b is incorrect because fifty hertz is the line frequency used in many countries outside the United States, particularly in Europe. U.S. machines are set to sixty hertz to match domestic electrical infrastructure. Option d is incorrect because one hundred hertz is not a line frequency used in standard power distribution systems. Setting the filter to a non-matching frequency would fail to remove the actual sixty hertz interference present in the room.