Mechanical Ventilation (PDF)

Mechanical ventilation, Anesthesia machine & Anesthesia gases (O2, N2O) supply  Normal breathing (spontaneous) Normally spontaneous breathingis a negative pressure ventilation. – It occurs as a result of creating a negative chest pressure ‫ونتيجة‬ which is created...

Mechanical ventilation, Anesthesia machine & Anesthesia gases (O2, N2O) supply  Normal breathing (spontaneous) Normally spontaneous breathingis a negative pressure ventilation. – It occurs as a result of creating a negative chest pressure ‫ونتيجة‬ which is created through the expansion of the diaphragm, as a result, the inspiratory air is sucked to the lungs..  Positive pressure ventilation 1. Mouth to Mouth Ventilation Positive pressure ventilation could be created by mouth to mouth ventilation or when using bag-valve- mask ventilation external air, is pushed to the lungs Can be used in apnea (stop breathing), as an example.  Positive pressure ventilation 2. Hand controlled BVM (Bag-Valve-Mask )ventilation Ambu-bag- ventilator (Bag-Valve-Mask BVM), can provide positive pressure mask ventilation.  Positive pressure ventilation 3. Hand controlled BV-ETT ventilation Ambu bag can provide positive pressure ventilation also through an endotracheal tube Positive Pressure Ventilation 4. Mechanical ventilation  Mechanical Negative pressure ventilation Iron Lung ventilator in 1927 / Drinker discovered the negative pressure ventilator. It consist of Iron box with two vacuum cleaners which create rhythmic negative pressure in the chest to inflate the lungs with air (inspiration), as in the natural breating, consequently followed by expiration. Ventilation is accomplished without ET tube or tracheostomy The iron lung exerted a push-pull motion on the chest Ventilator bulky & expensive Mode of ventilation is cumbersome The Iron Lung have reached its peak in 1950 during a polio epidemic which has swept through Europe  Positive Pressure Ambu bag ventilation History Positive Pressure Mechanical Ventilation (through Ambu bag) gained momentum during the polio epidemic in Scandinavia and in the USA in early 1950s 1400 studies, decreased mortality from 80% to 25%→ led to the use of Positive Pressure Ventilation. At present; positive-pressure ventilation is applied through mouth to mouth, AMBU bag or mechanical ventilation.  Present Positive Pressure Ventilation Mechanical ventilation Positive pressure mechanical ventilation started to widespread in large scale in 1960s Today, mechanical ventilation it is the second most frequent performed therapeutic intervention after treatment of cardiac arrhythmia in the operating room & ICUs  Principle of Mechanical Ventilators Mechanical ventilator is a machine, that provides → a controlled flow of O2, N2O & air supplied from cylinders or wall outlets (central); …→and creates Positive Pressure Ventilation ……the so called Intermittent Positive Pressure Ventilation (IPPV),to the patient In the OR  Anesthesia Mechanical Ventilators Operating principals IPPV by adults is controlled by mainly four parameters; 1.Tidal volume→ 8-10 ml/kg 2.Respiratory rate 12- 15/m 3.I:E ratio, 1:2 4.FIO2 Varies generally from 0.21 to 1.0  21% - 100%  The anesthesia machine & Gases supply The anesthesia machine is designed to provide an accurate, continuous supply of oxygen and nitrous oxide to the patient. Anesthesia machines usually incorporate a ventilator, vaporizers, humidifiers, CO2 absorbers & other functions. Modern anesthetic machine have several features to ensure patient safety, which include monitors to monitor the patient's heart rate, ECG, blood pressure and oxygen saturation. All aesthesia machines are connected to central piped hospital oxygen, and nitrous oxide, back-up cylinders.  Central gas supply source Ceiling-mounted gas pipes used for delivery of anesthetic gases: oxygen (green), nitrous oxide (blue), air (yellow), vacuum (white).  Central gas supply source, O2, N2O O2, N2O The hospital central medical gas pipeline source is the primary source for the anesthesia gas machine. Oxygen is produced by fractional distillation of liquid air. It is stored as a liquid in a large flasks. Safety systems send oxygen to the hospital pipeline at approximately 50 *psig; which is therefore the "normal working pressure" of the anesthesia gas machine. Nitrous oxide is stored as a liquid, in large tanks (745 psig- H tank) connected to a manifold which regulates the pipeline pressure to approximately 50 *psig. *Psig pounds per square inch gauge  Cylinders gas supply source (type E, G, or H). E cylinders (those commonly attached to the back of the anesthesia machine) contain 625 L of oxygen, G cylinder contain when full 5,300 L H cylinders contain when full 6,900 L The World Health Organization specifies that white, is the color of oxygen cylinders.  Reserve gas cylinders Reserve gas cylinders (back up cylinders) of oxygen, air, and nitrous oxide attached to the back of the machine. In situations where central pipeline gases are interrupted, back up gases from cylinders are connected automatically.