The following page identifies the most common paramedical science and scientific laws used in the practice of paramedicine. Although many of the names of these laws are rapidly forgoton after sitting one’s final paramedic exam, the laws themselves, and the relationship of the laws to a patient’s condition and pathophysiology is required on a daily basis.
For a fixed amount of an ideal gas kept at a fixed temperature, P [pressure] and V [volume] are inversely proportional (while one increases, the other decreases).
Basically when talking about a gas pressure and volume are inversely proportional. Increase the pressure equals a decrease in volume. Increase the volume, decrease the pressure on the gas.
For a practical paramedical example:
This means that if a SCUBA diver holds his/her breath at a depth of 10 metres of water (which doubles the pressure exerted on the air in the lungs) the volume of the air in his lungs will be half that at which it would be at the surface. This becomes important, because if the diver was have taken a deep breath and filled his lungs with air at a depth of 10metres, and then held his breath as he returned to the surface – the volume of air would have doubled as the pressure halved, and because he lungs cannot hold this much air, something would have burst.
At a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressureof that gas in equilibrium with that liquid.
Basically, the amount of gas disolved in a liquid (ie: oxygen in the alvioli) is equal to the partial pressure (percentage) of that gas.
For a practical paramedical example:
This basically means that if a patient is receiving normal air, which has 21% oxygen into his lungs the partial patial pressure of oxygen which is being diffused across the alvioli is only 21% of the overall partial pressure. Now, however, if you change this equation to 100% oxygen, the full partial pressure of oxygen can be exerted to difuse across the alvioli. This is why we treat patients with shortness of breath with high concentration oxygen.
The total pressure exerted by a mixture of gas is equal to the sum of the partial pressures of each individual component in a gas mixture. (P1+P2+P3) equals the pressure of the combined mixture.
Therefore if the partial pressure of oxygen in air equal 5, and nitrogen equals 85 and Co2 equal 5 – the total pressure of air equals 95.
For a practical paramedic example:
The concentration of dissolved gas depends on the partial pressure of the gas. The partial pressure controls the number of gas molecule collisions with the surface of the solution. If the partial pressure is doubled the number of collisions with the surface will double. The increased number of collisions produce more dissolved gas. Therefore, if the patient receives a higher level concentration of oxgyen, therefore increasing the partial pressure of oxygen concentration, there will be a geater amount of oxygen that can diffuse across the alvioli membranes.
The pressure that one component of a mixture of gas would exert if it were alone
KE = ½ MV2
This means that Kenetic Energy (K/E) equals one half times the mass time the velocity squared.
In a practical paramedic sense: this means that a patient who weighs 80kgs (Mass in Kg) is travelling at 3 metres per second on a bycycle (Velocity is metres per second) hits a brick wall – this patient will have to disperse a total of 80kg x 3 squared x ½ = 360 joules of kinetic energy.
This can become important as a paramedic when you consider that man on a bycycle with an overal KE of 360joules collides head on with a car which has an overall KE of 12000 joules which must also be dispersed to make the car stop – you can understand how injured the patient on ht bycycle will be. Admitedly, you could also just look at your patient to realise that he’s been hit by a much bigger object.
The greater the blood volume (BV) entering the heart during diastole, the greater the BV ejected during the systolic contraction of the heart.
Identifies significant indication of raised ICP, often a late sign. Includes: Respiratory changes/ Irregularities, Widened Pulse Pressure, and Bradycardia.
Kehr’s sign is the presense of shoulder tip pain associated with abdominal pain and often relates to refered pain from organ injury or damage within the abdomen.
Cardiac Output can be calculated with formula: CO= HR (heart rate) x SV (stroke volume).
Pulse pressure can be calculated by measuring the Systolic BP – the Diastolic BP.
Mean Arterial Pressure
The MAP represents the average pressure within the arterial system. MAP can be calculated by the formula: MAP = Diastolic BP + 1/3rd Pulse Pressure.