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Ventilator

Ventilator. Ventilator. Gas Supply. 1 bar = 100 kPa = 14.5 psi 100% Oxygen Medical Air (21% Oxygen and 79% Nitrogen) Either Wall or Bottled Gas Air can be from a compressor Colour Coded. Wall Gas. Wall gas = pressure of 350-400kPa Colour Coded Indexed. Bottled Gas.

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Ventilator

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  1. Ventilator

  2. Ventilator

  3. Gas Supply • 1 bar = 100 kPa = 14.5 psi • 100% Oxygen • Medical Air (21% Oxygen and 79% Nitrogen) • Either Wall or Bottled Gas • Air can be from a compressor • Colour Coded

  4. Wall Gas • Wall gas = pressure of 350-400kPa • Colour Coded • Indexed

  5. Bottled Gas • Gas Bottles 15MPa but has a regulator that reduces it to 350-400kPa • Pin indexed

  6. Ventilator

  7. Compressor • Used if Medical Air is not available • If oxygen is not available in an emergency then the compressor can be used to supplement BOTH gases • Usually seated underneath the ventilator • Suggested to have if the wall gas or bottled gas is not reliable

  8. Filters • Gas Supplies not always clean • Filters to protect the equipment as well as the patient • Water can also be present and so a water trap is also useful • Water traps must be emptied!!!!!

  9. Filters • Filters and water traps on the inlet • Filters in the patient circuit • Bacterial filters to prevent infection to patients

  10. Ventilator

  11. Pressure Regulators • From 350-400 kPa to 110-170-kPa (depending on the ventilator) • Need to be calibrated if they are prone to drifting

  12. Ventilator

  13. Gas Mixing and Flow Control • Solenoids control flow and mix of gases • Proportional • Changing current = changing flow • Solenoids work in unison to control flow

  14. Ventilator

  15. Gas Mixing and Flow Control • Control: • tidal volumes • Patient flow rates • Respiratory rates • I:E ratios and oxygen flow • Gases are either mixed in tubing or a separate chamber • Most ventilators have a separate chamber for the gas to be inspired. • Used for mixing gas as well as reserve chamber for gas to be inspired

  16. Ventilator

  17. Oxygen Measurement and Sensors • Measured by oxygen sensors • Not controlled by the sensors • Especially important if delivering oxygen to neonates

  18. Oxygen Sensors • Sensors known as Clark Type Sensors • Organic material covering an electrolyte and 2 metal electrodes • Oxygen diffuses through the membrane and is reduced, this creates a current which is measured

  19. Oxygen Measurement and Sensors • Life span of 1-2 years depending on use • Sensor is in line with the inspired gas

  20. Oxygen Measurement • When calibrated it is taken out of line and 100% oxygen and 21% oxygen are passed over the cell to compare with the expected voltages • If the voltage is different to the expected value to ventilator will alarm and the sensor must be changed

  21. Retinopathy of Prematurity • Small birth weight babies can develop the condition • The Retina of the eye becomes detached when the blood vessels do not form properly • Can be due to high concentrations of oxygen when first born

  22. Retinopathy of Prematurity • The oxygen levels of these babies must be closely checked • Most effective way to tell is by using the percent of oxygen saturation in blood (SpO2) • If infant is at 100% saturation then the percentage of oxygen in the inspired gas is reduced • Once infants are older then not a danger • Adults have no difficulty as the retina is firmly attached

  23. Ventilator

  24. Flow Sensors • Used to detect the flow rate to the patient • Differential Pressure flowmeter • Metal Gauze plate to reduce flow • Causes a pressure difference proportional to flow rate • Pressure measured and used to determine flow

  25. Flow Sensors • Hot Wire Anemometer • Thin Platinum wire that is heated to constant temp • Fixed resistance • As gas is passed over wire it cools down, increasing the resistance. Current is increased to the wire to maintain temp • The extra current is proportional to the flow

  26. Flow Sensors • This determines flow but not direction • If 2 wires are in parallel then direction can be found • One wire will cool before the other

  27. Flow Sensors • Flow is obstructed • When air passed through tubing opens the flap • Changed the pressure on the strain gage • Increase in flow is a reduction in resistance

  28. Flow Sensors • Within the patient circuit so must be cleaned after each use • Can become brittle and break • Can be changed while the vent is in use (but alarm will be triggered) • Solenoids control the flow not the sensor so only an alarm will sound

  29. High Frequency Ventilation • Initial inflation of the lungs • Hold lungs open • Circulates the gas around the lungs • Still has a flow rate similar to normal ventilation • Frequency from 3 - 15Hz depending on the patient • Reduces the strain on the lungs • Keeps lungs inflated, increases the compliance • Quicker recovery time • Sometimes used on adult patients with damaged lungs

  30. Ventilator

  31. Power Supplies • Mains power is regulated and reduced into set voltages • ±5 Volts • ± 12 Volts • ± 24 Volts • Loss of power Alarm for most ventilators • Battery power that is charging when on mains power and in use when power failure

  32. CPU

  33. CPU • Controls regulation of all parameters • Checks alarm conditions • Keeps a record of all errors • Attached to the user interface (controls) • Calibrated Flow Sensor and Oxygen Sensor • Can interface with other equipment • Monitor • Nurse Call Alarm • Checks for leaks in the system

  34. Ventilator

  35. Exhalation System • Controls: • Timing of breaths • Volume of the air delivered to the patient • During inhalation the exhalation valve closes to stop the flow of gas out of the system and into the patient this inflates the patient’s lungs • During exhalation the valve is opened to allow gas from the patient out through the expired limb • Usually removable to allow for cleaning • Usually heated to stop condensation

  36. PEEP System • Positive End Expired Pressure • Keeps lungs slightly inflated • Reduces damage to lungs • Maintained by closing the expiratory valve

  37. Humidification • Normally inspired air is warmed and humidified by the mouth and nose and then passed into the lungs • Dry air can damage the lungs and cool air can reduce the patient’s temperature • Heated humidifier is used to substitute the normal pathway • Patient is usually intubated via the nose or mouth

  38. Humidification • A heated humidifier is a hot plate with a water reservoir • Water is heated and the gas is passes over it • The gas becomes warm and moist and then enters that patient’s lungs • The patient circuit is usually heated to reduce the amount of condensation or “rain-out”

  39. Breathing Circuit • Inspiratory tubing • Humidifier • Heated wire • Y-piece – connects inspiratory to expiratory • Expiratory tubing – not heated • Water trap

  40. Expired Air • Once the air has been expired by the patient: • No longer heated • Water trap to remove moisture • Enters expiratory block • heated to stop rain out • Filtered to stop infection from getting into the unit as well as contaminating the environment • Either enters room air or is scavenged

  41. Connection to Patient • Endotracheal tubing • Connects patient to ventilator • Inserted into nose or mouth and into the trachea • Balloon at the end that is inflated

  42. Intubation • Process of inserting the tubing into the patient’s airway

  43. Intubation • Once inserted, a balloon is inflated to create a seal

  44. Safety Valve System • Provides a path to atmosphere for patient to breathe • If there is a power failure • Also limits the maximum pressure in the system • Spring keeps the safety valve closed normally • During power failure safety valve is released • Patient can breathe without restriction

  45. Clinical Terms • PEEP = Positive End Expiratory Pressure • Pressure remaining in the circuit at the end of expiration • PIP = Peak Inspiratory Pressure • Maximum pressure of inspiration • FiO2 = Fractional Inspired Oxygen • Displayed as a percentage • TE = Expiratory Time • I/E Ratio = ratio of time for inspiration and expiration • MAP = Mean Airway Pressure • The average pressure that the circuit has

  46. Modes of Ventilation • CPAP = Continuous Positive Airway Pressure • For patients that can initiate their own breathing but cannot supply enough oxygen for breathing • Similar to PEEP • Positive pressure keeps alveoli open • Easier to breathe • Constant flow of gas

  47. Modes of Ventilation • IMV = Intermittent Mandatory Ventilation • CMV = Continuous Mandatory Ventilation • Breath rate, pressure and volume of breaths set by user • Vent increases the pressure in the circuit to push air into the lungs • Pressure reduce for expiration

  48. Modes of Ventilation • SIMV = Synchronised Intermittent Mandatory Ventilation • Vent detects the patient trying to breathe and delivers a gas to them • Used if trying to wean the patient off the ventilator • For patients that still require a little bit of ventilation • IPPV = Intermittent Positive Pressure Ventilation • Similar to IMV and CMV but patient can take their own breaths (do not have to fight the ventilator)

  49. Neonatal Settings • HFV = High Frequency Ventilation • HFO = High Frequency Oscillation • Premature babies have fragile lungs • Have not matured • Easily damaged • Use HFV instead of traditional ventilation • Lungs inflated • Small, high frequency pressure changes • Circulates the air in lungs • Does not open and close them • Better for the lungs • Frequency 5 -20 hertz

  50. Neonatal Flow = 6 litres/min TI = 0.5 seconds TE = 0.5 seconds BPM = 60 PEEP = 5 cm H2O Tidal Volume = 50 mL/kg Adults Flow = 30-50 L/min TI = 2.5 seconds TE = 2.5 seconds BPM = 12 PEEP = 5 cm H2O Tidal Volume = 600-1200mL Typical Settings

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