Pressure

Pressure

1. DEFINE PRESSURE

   • Pressure is an effect when force is applied to any given area
     • Small area = greater pressure Larger area = less pressure
       • Pressure = Force/Area
         • Force= mass x acceleration
       • Needle has greater force than finger

2. HOW DO WE MESSURE PRESSURE

   • Pascals Pa or Kilopascals kPA
     • Notmal air pressure = 101.3kPA Blood gas - 13.3kPA
     • Blood gases: partial pressure of o2 (Po2) =13.3kPA
   • Brritish units = Pounds/square inch (psi)
     • Gas cylinders in operating theatres
   • Atmospheric pressure
     • Messured in Millimetres of mecury
       • 1Atm = 760mmHg

3. MEASURING PREESURE IN BODY

   • Blood pressure
     • Pressure that blood exerts on the wall, measure at teh brachial artery
     • Systolic blood pressure – first korotkoff sound, when heart is contracting (90-140mm HG)
     • Diastolic – fifth korotkoff sounds, when heart is relaxing (70-90mmHG)
   • Manometers- Some have water and saline
     • Cm water and Cm saline - used to record contiuies blood pressure without cuff

4. Describe and apply the properties of pressure and static liquids

   • Pressure is dependent on the DEPTH of Liquid GREATEST DEPTH =Highest flow rate
   • Pressure is dependant on the DENSITY = GREATEST DENSITY = highest pressure
   • PASCALS LAW
     • Pressure is exerted equally in all directions in a static liquid - THINK BABY IN BELLY AND FALL

5. BOYLES LAW

   • When pressure INCREASES volume DECREASE When pressure DECREASE volume INCREASE(ballon)
     • ACTIVE = INSPIRATION Diaphrgm contract, Quiet
     • Passive = EXPIRATION, Elastic recoil, Forced

6. Respirators

   • Negative pressure "iron lung"
     • Alters pressure in chamber - Polio
   • Postive pressure
     • Oxygen pushes - apnoea, life support

7. Daltons law

   • P(total) = p1+p2+p3...
   • Air mixture of N2, 02, co2, h20

8. Henry's law

   • 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
     • CO 2 & O 2 transported in solution • ↑ partial pressure → ↑ gas dissolved
     • ↑ PO 2 → O 2 binds to haemoglobin
     • ↑ 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 -
   • Hypoxemia • ↓PO in arterial blood • Causes: 2 • High altitude • Respiratory failure • Emphysema • Lung disease (COPD) • Acute asthma

9. Pulmonary respiration

   • Movement of air inside and outside lungs

10. Internal and External respiration

    • internal -
      • Internal respiration occurs in the metabolizing tissues, where oxygen diffuses out of the blood and carbon dioxide diffuses out of the cells.
    • external
      • occurs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses into the alveolar air.