By: Dr.behzad barekatain,MD Assistant professor of pediatrics Neonatologist Isfahan university of medical scienses

Mechanical ventilation can be achieved through the use of intermittent negative- pressure or positive-pressure devices. Negative-pressure ventilators are mainly of historical interest. Negative pressure respirators can provide assisted ventilation without the need for endotracheal intubation; thus trauma to the airway is avoided and the risk of infection is reduced. They can also provide effective continuous negative pressure.‘ The only commercially available equipment for newborns, the Isolette Respirator (Airshields, Inc., Hatboro,PA, USA), is no longer manufactured. In the early 1990s, this form of ventilation experienced a minor resurgence of interest because. The Isolette Respirator has not been proven effective in the ventilation of VLBW infants, who represent the largest group of the NICU population.

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 The era of intensive care medicine began with positive-pressure ventilation The iron lung created negative pressure in abdomen as well as the chest, decreasing cardiac output. Iron lung polio ward at Rancho Los Amigos Hospital in 1953.

Draeger Medical designed “Draeger Pulmoter ”

FLOWMETER O2 SENSOR bLENDER O2AIR Humidifier Warmer Pressur control To patient Flow or pressur sensore pop off Expiratory limb

Adjustable Dual Flow System  Base Flow (4-6 minute ventilation)  Controls flow for spontaneous effort  Inspiratory Flow (2-3 base flow)  Adjusts flow for delivery of pressure  Effects Rise Time

Goals of Mechanical Ventilation.Achieve and maintain adequate pulmonary gas exchange.Minimize the risk of lung injury.Reduce patient work of breathing.Optimize patient comfort

Two groups of ventilation: Conventional: deliver physiologic tidal volume High-frequency: deliver tidal volume less than physiologic dead space Classification of conventional ven: Volume-target ventilator Pressure-target ventilator

CONTROL (fixed)VARIABLE (Modalities) Volume: in volume-controlled ventilator Pressure:in pressure-preset ventilator PHASE (changeable)VARIABLE (Modes) Triggering اغازگر :شروع دم را کنترل میکند *.time triggering>>>>>in IMV mode (ALS,IVH).patient triggering>>>>in SIMV OR A/C mode(sensor) Limiting & controlling * محدود کننده فاکتورهای تنفسی یا حداکثر مجاز :وقتی ونتیلاتور به حداکثر مجاز آن متغییر برسد دریچه های تخلیه را باز میکند. Cycling* پایان دم را کنترل میکند.felow-cycled.Time-cycled.Pressure-cycled

Classification (the Basic Questions) A. Trigger mechanism  What causes the breath to begin? B. Limit variable  What regulates gas flow during the breath? C. Cycle mechanism  What causes the breath to end? A BC

Cycling Vs. Limiting Cycled Pressur e Time Limited Pressur e

Flow Peak Flow (100%) Time 10% leak Set (max) Tinsp. Tinsp. (eff.) Flow Cycled Ventilation

Mechanical Ventilation Modalities Pressure-targeted Volume-targeted

Pressure-targeted Modalities Pressure-support ventilation (PSV) Pressure-control ventilation (PCV) PCV-AC PCV-SIMV PCV-IMV Pressure-limit ventilation (PLV)

Pressure-targeted modalities are characterized by limiting the amount of pressure that can be delivered during inspiration. The clinician sets the maximum pressure and the ventilator does not exceed this level. The volume of gas delivered to the baby varies according to lung compliance and the degree of synchronization between the baby and the ventilator. If compliance is low, less volume is delivered than if compliance is high. In IMV, tidal volume fluctuates depending on whether the baby is breathing with the ventilator or against it.

Volume Pressure Volume Pressure

Figure 3

Volume-targeted Volume control ventilation Volume control A/C Volume control SIMV Volume control IMV

Mechanical Ventilation Modes

Hybrid ventilation Volume guarantee Pressure-regulated volume control(PRVC) (PLV+VCV) Volume assured pressure support(VAPS) (PSV+VCV) Volume support ventilation (PSV+PRVC) Pressure augmentation

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