Patient Calculations Flashcards

1
Q

Describe the structure of an ECG

A

P wave
QRS spike
T wave

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2
Q

What does each part of an ECG correspond to?

A

P wave - Atrial depolarisation
QRS spike - Ventricular depolarisation
T wave - Ventricular repolarisation

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3
Q

Why does an ECG only reflect the electrical activity of contractile tissue?

A

Due to the constant action potentials of conductive tissue, the electrical activity of these structures (e.g. SAN, AVN) cannot be detected

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4
Q

What is the significance of the R-R and P-Q intervals?

A

R-R is used to measure heart rate

P-Q is used to ensure the heart follows a normal excitation cycle

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5
Q

What would represent atrial fibrillation on an ECG?

A

Absence of P wave

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6
Q

What would represent 1°, 2° and 3° heart block on an ECG?

A

1° - Extended P-Q interval
2° - Missed beats
3° - No P wave due to AVN being pacemaker

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7
Q

What would differentiate between a STEMI and NSTEMI on an ECG?

A

ST elevation, caused by ischaemic tissue in a STEMI

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8
Q

What would suggest that a patient has Wolff-Parkinson-White on an ECG?

A

Short P-Q interval due to external conduction pathways

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9
Q

What are the two ways of measuring ventilation?

A

Minute ventilation: Tidal vol. x Resp. rate
Alveolar ventilation: (Tidal vol. - Dead space) x Resp. rate

Both in (ml/min)

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10
Q

What is the approximate volume of anatomical dead space?

A

150ml

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11
Q

How can airway obstruction be identified?

A

FEV1/FVC less than 80%

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12
Q

Define compliance and give the equation for it

A

Ease of expansion of the lungs depending on the volume and pressure

Cl = Change in vol./Change in pressure

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13
Q

Describe the observations of normal, high and low compliance

A

Normal: Increase in TP causes increase in vol.
High: Small increase in TP cause large increase in volume
Low: Large increase in TP causes small increase in volume

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14
Q

What conditions can cause high or low lung compliance?

A
  • High: Emphysema

- Low: Oedema, Fibrosis, Pneumonia

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15
Q

How is change in TP measured?

A

TP(end) - TP(start)

[Palv - Pip]end - [Palv - Pip]start

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16
Q

What is renal clearance?

A

Volume of plasma completely cleared of a substance with unit time

17
Q

What is the equation of renal clearance?

A

Cx = [Ux]V/[Px]

[Ux] = conc. in urine
[Px] = conc. in plasma
V = rate of urine production (vol/time)
18
Q

How is the proportion of drug to ionised drug worked out?

A

pH = pKa + log[A-]/[HA]