Patient Calculations Flashcards
Describe the structure of an ECG
P wave
QRS spike
T wave
What does each part of an ECG correspond to?
P wave - Atrial depolarisation
QRS spike - Ventricular depolarisation
T wave - Ventricular repolarisation
Why does an ECG only reflect the electrical activity of contractile tissue?
Due to the constant action potentials of conductive tissue, the electrical activity of these structures (e.g. SAN, AVN) cannot be detected
What is the significance of the R-R and P-Q intervals?
R-R is used to measure heart rate
P-Q is used to ensure the heart follows a normal excitation cycle
What would represent atrial fibrillation on an ECG?
Absence of P wave
What would represent 1°, 2° and 3° heart block on an ECG?
1° - Extended P-Q interval
2° - Missed beats
3° - No P wave due to AVN being pacemaker
What would differentiate between a STEMI and NSTEMI on an ECG?
ST elevation, caused by ischaemic tissue in a STEMI
What would suggest that a patient has Wolff-Parkinson-White on an ECG?
Short P-Q interval due to external conduction pathways
What are the two ways of measuring ventilation?
Minute ventilation: Tidal vol. x Resp. rate
Alveolar ventilation: (Tidal vol. - Dead space) x Resp. rate
Both in (ml/min)
What is the approximate volume of anatomical dead space?
150ml
How can airway obstruction be identified?
FEV1/FVC less than 80%
Define compliance and give the equation for it
Ease of expansion of the lungs depending on the volume and pressure
Cl = Change in vol./Change in pressure
Describe the observations of normal, high and low compliance
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
What conditions can cause high or low lung compliance?
- High: Emphysema
- Low: Oedema, Fibrosis, Pneumonia
How is change in TP measured?
TP(end) - TP(start)
[Palv - Pip]end - [Palv - Pip]start