1. Mechanical Ventilation
Ventilators

2. Origins of mechanical ventilation
Negative-pressure ventilators (“iron lungs”)
Non-invasive ventilation first used in Boston Children’s Hospital in 1928
Used extensively during polio outbreaks in 1940s – 1950s
Positive-pressure ventilators
Invasive ventilation first used at Massachusetts General Hospital in 1955
Now the modern standard of mechanical ventilation

3. Negative pressure

4. Negative pressure ventilator
The person using the iron lung is placed into the central chamber, a cylindrical steel drum.
A door allowing the head and neck to remain free is then closed, forming a sealed, air-tight compartment enclosing the rest of the person's body.
Pumps that control airflow periodically decrease and increase the air pressure within the chamber, and particularly, on the chest.
When the pressure is below that within the lungs, the lungs expand and atmospheric pressure pushes air from outside the chamber in via the person's nose and airways to keep the lungs filled;
when the pressure goes above that within the lungs, the reverse occurs, and air is expelled. In this manner, the iron lung mimics the physiological action of breathing: by periodically altering intrathoracic pressure, it causes air to flow in and out of the lungs. The iron lung is a form of non-invasive therapy.

5. Types of Ventilators (Positive)
Pressure-cycled modes
Pressure Support Ventilation (PSV)
CPAP (Continuous positive airway pressure)
BiPAP (Bi-level positive airway pressure)
Volume-cycled modes
Control mode
Assist mode
Assist/Control mode
Intermittent Mandatory Ventilation (IMV)
Synchronous Intermittent Mandatory Ventilation (SIMV)

7. CPAP
Continuous positive airway pressure (CPAP) is the use of continuous positive pressure to maintain a continuous level of positive airway pressure.
A continuous level of elevated pressure is provided through the patient circuit to maintain adequate oxygenation, decrease the work of breathing, and decrease the work of the heart (such as in left-sided heart failure CHF)

9. BiPAP
BiPAP
It delivers a preset inspiratory positive airway pressure (IPAP)
and expiratory positive airway pressure (EPAP). 
Use
Bi-level positive airway pressure is used when positive airway
pressure is needed with the addition of pressure support. Common
situations where positive airway pressure is indicated is any disease
where taking a breath is difficult.
This includes pneumonia, chronic obstructive pulmonary
disease and asthma .

10. Assist/Control Mode – Volume Cycled modes
Patient receives a set number of breaths and cannot breathe between ventilator breaths
Assist Mode
Patient initiates all breaths, but ventilator cycles in at initiation to give a preset tidal volume
Patient controls rate but always receives a full machine breath
Assist/Control Mode
Assist mode unless patient’s respiratory rate falls below preset value.
Ventilator then switches to control mode

11. IMV and SIMV Intermittent Mandatory Ventilation (IMV)
Pt receives a set number of ventilator breaths
Patient can initiate own (spontaneous) breaths
spontaneous breaths are not supported by machine with fixed TV
Ventilator always delivers breath, even if pt exhaling
Synchronous Intermittent Mandatory Ventilation (SIMV)
Most commonly used mode
Spontaneous breaths and mandatory breaths
If pt has respiratory drive, the mandatory breaths are synchronized with the pt’s inspiratory effort

13. Indications for intubation
Criteria
Clinical deterioration
Tachypnea: RR >35
Hypoxia: PaO2<60mm Hg
Hypercapnea: PaCO2 > 55mm Hg
Minute voluntary ventilation( MVV)<10 L/min
Tidal volume(TV) <5-10 ml/kg
Negative inspiratory force < 25cm H2O (how strong the pt can suck in)

15. Initial ventilatory settings
Fractional inspired oxygen concentration (FiO2 ) = 50%
Positive end expiratory pressure (PEEP) = 5cm H2O
Respiratory rate (RR) = 12 – 15 breaths/min
Tidal volume (VT ) = 10 – 12 ml/kg
Pressure Support = 10 cm H2O

16. Indications for extubation
Clinical parameters
Resolution/Stabilization of disease process
Hemodynamically stable
Intact cough/gag reflex
Spontaneous respirations
Acceptable vent settings
FiO2< 50%, PEEP < 8, PaO2 > 75mm Hg, PH > 7.25

17. Weaning General approaches SIMV Weaning
Pressure Support Ventilation (PSV) Weaning
Spontaneous breathing trials