Pressure

Pressure

DEFINE PRESSURE
1. Pressure is an effect when force is applied to any given area
  1. Small area = greater pressure Larger area = less pressure
    1. Pressure = Force/Area
      1. Force= mass x acceleration
    2. Needle has greater force than finger
HOW DO WE MESSURE PRESSURE
1. Pascals Pa or Kilopascals kPA
  1. Notmal air pressure = 101.3kPA Blood gas - 13.3kPA
  2. Blood gases: partial pressure of o2 (Po2) =13.3kPA
2. Brritish units = Pounds/square inch (psi)
  1. Gas cylinders in operating theatres
3. Atmospheric pressure
  1. Messured in Millimetres of mecury
    1. 1Atm = 760mmHg
MEASURING PREESURE IN BODY
1. Blood pressure
  1. Pressure that blood exerts on the wall, measure at teh brachial artery
  2. Systolic blood pressure – first korotkoff sound, when heart is contracting (90-140mm HG)
  3. Diastolic – fifth korotkoff sounds, when heart is relaxing (70-90mmHG)
2. Manometers- Some have water and saline
  1. Cm water and Cm saline - used to record contiuies blood pressure without cuff
Describe and apply the properties of pressure and static liquids
1. Pressure is dependent on the DEPTH of Liquid GREATEST DEPTH =Highest flow rate
2. Pressure is dependant on the DENSITY = GREATEST DENSITY = highest pressure
3. PASCALS LAW
  1. Pressure is exerted equally in all directions in a static liquid - THINK BABY IN BELLY AND FALL
BOYLES LAW
1. When pressure INCREASES volume DECREASE When pressure DECREASE volume INCREASE(ballon)
  1. ACTIVE = INSPIRATION Diaphrgm contract, Quiet
  2. Passive = EXPIRATION, Elastic recoil, Forced
Respirators
1. Negative pressure "iron lung"
  1. Alters pressure in chamber - Polio
2. Postive pressure
  1. Oxygen pushes - apnoea, life support
Daltons law
1. P(total) = p1+p2+p3...
2. Air mixture of N2, 02, co2, h20
Henry's law
1. The amount of a gas that will dissolve in a given type and volume of liquid at a constant temperature is directly proportional to the partial pressure of the gas and it’s solubility constant
  1. CO 2 & O 2 transported in solution • ↑ partial pressure → ↑ gas dissolved
  2. ↑ PO 2 → O 2 binds to haemoglobin
  3. ↑ PCO 2 → O 2 2 binds to haemoglobin → CO is dissolved and transported as bicarbonate ion • H 2 O + CO 2 2 ↔ H 2 CO 3 ↔ H + + HCO 3 -
2. Hypoxemia • ↓PO in arterial blood • Causes: 2 • High altitude • Respiratory failure • Emphysema • Lung disease (COPD) • Acute asthma
Pulmonary respiration
1. Movement of air inside and outside lungs
Internal and External respiration
1. internal -
  1. Internal respiration occurs in the metabolizing tissues, where oxygen diffuses out of the blood and carbon dioxide diffuses out of the cells.
2. external
  1. occurs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses into the alveolar air.

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