SUCTION UNITS • Purpose: A suction/pressure unit can provide controlled pressure, vacuum, or both. They can be portable or fixed • Suction Units Uses • High volume • Saliva evacuators in dental • Surgery and ER for drainage of wounds and massive bleeding • On "crash carts" for quick aspiration during emergencies
SUCTION UNITS • Low volume • ENT-for minor surgery, ear irrigation, etc • Wards-thermatic units for slow drainage • Various lab and dental equipment; cell counters, vacuum mixer investor, porcelain furnace • Pressure Units Uses • Automatic BP cuffs • Nebulizers and portable ventilators • Impedance audiometers and tympanographs • Automated lab equipment to operate valves, pistons, etc
SUCTION UNITS • Types of Suction/Pressure Units • Piston • Operates on principle of moving piston inside a cylinder • Valves (either cam operated or reed) control direction of air flow • Vary greatly in size • Can achieve extremely high volume and pressures • Usually require maintenance of oil level-although some are "oil less"
SUCTION UNITS • Oscillating pumps • A rapidly oscillating rubber diaphragm replaces the moving piston • Small versions (aquarium pump style) are found in some cell counters • Larger versions are seen in dental lab • Can obtain fairly good vacuum and pressure • Virtually maintenance free Does require periodic replacement of diaphragm
SUCTION UNITS • Rotary vane • Uses an eccentric rotor within a cylinder • Movable vanes keep tight seal • Air intake provides vacuum • Exhaust side supplies pressure • Can obtain very high vacuum • Very common throughout hospital (portable pressure/suction units) • Require periodic maintenance of oil level and cleaning of vanes
SUCTION UNITS • Thermotic (Intermittent) • Uses principle of Charles's Law • Gas expands when heated • The gas contracts when cooled • Valves control direction of air flow • Used for vacuum applications only • Vacuum produced is cyclic-intermittent • Extremely low vacuum and volume • No moving parts and maintenance free
SUCTION UNITS • Measurement • Vacuum • mmHg (millimeters of Mercury) • inches of Hg (Hg = Mercury) • cm of Hg (cm = centimeters) • inches of water • cm of water
SUCTION UNITS • Pressure • lb/sq in (pounds per square inch) • Kg/sq cm (kilograms per square centimeter) • mmHg • inches of Hg • Flow rate • cu ft/min • liters/min • liters/hr • Conversions - units of measurements within each category can be converted