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 ofinterest because.

The Isolette Respirator has not been proven effective in the ventilation of VLBWinfants, who represent the largest group of the NICU population.

Origins of mechanical ventilationOrigins 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

popoff

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 ventilatorPHASE (changeable)VARIABLE (Modes) Triggering میکند : کنترل را دم شروع * اغازگر

.time triggering>>>>>in IMV mode (ALS,IVH) .patient triggering>>>>in SIMV OR A/C mode(sensor) Limiting & controlling* : وقتی مجاز حداکثر یا تنفسی فاکتورهای کننده محدود

میکند باز را تخلیه های دریچه برسد متغییر آن مجاز حداکثر به .ونتیالتور Cycling* میکند کنترل را دم پایان

.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

B C

Cycling Vs. Limiting

Cycled

Pressure

Time Time

Limited

Pressure

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 ventilationVolume control A/CVolume control SIMVVolume control IMV

Mechanical Ventilation Modes

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

Thanks