Basics of Mechanical Ventilation

Origins of mechanical ventilationOrigins of mechanical ventilation

•Negative-pressure ventilators (“iron lungs”)• first used in Boston Children’s

Hospital in 1928

•Used extensively during polio outbreaks in 1940s – 1950s

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.

Era of intensive care begun with this

Positive-pressure ventilators Invasive ventilation first used at

Massachusetts General Hospital in 1955Now the modern standard of

mechanical ventilation

OutlineOutline

•Modes•Ventilator Settings•Indications to intubate•Indications to extubate•Trouble shooting

Pressure ventilation vs. volume Pressure ventilation vs. volume ventilationventilation

Pressure-cycled modes: -deliver a fixed pressure at variable volume

Volume-cycled modes: -deliver a fixed volume at variable pressure

Ventilator settings

1. Ventilator mode

2. Respiratory rate

3. Tidal volume or pressure settings

4. Inspiratory flow

5. I:E ratio

6. PEEP

7. FiO2

8. Inspiratory trigger

CMV

CMV

CMV

CMV

CMV

CMV

CMV-Volume

Volume

Tidal Volume

CMV-P

A/CV

SIMV

Pressure Support Ventilation (PSV)Pressure Support Ventilation (PSV)Patient determines RR, VE, inspiratory time – a purely spontaneous mode

CPAP and BiPAPCPAP and BiPAPCPAP is essentially constant PEEP; BiPAP is CPAP plus PS

•ParametersCPAP – PEEP set at 5-10 cm H2OBiPAP – CPAP with Pressure Support (5-20 cm H2O)

Shown to reduce need for intubation and mortality

Respiratory Rate

10-12/Min – Adult

20+_ 3 - Child

30- 40 - New born

Increase –

Hypoxia

Hypercapnoea / Resp.Acidosis

Decrease

Hypocapnoea

Resp.Alkalosis

Asthma / COPD

Respiratory Rate

DHIDHI

Hey not

always the

same buddy

Tidal Volume or Pressure setting

Optimum volume/pressure to achieve good ventilation and oxygenation without producing alveolar overdistention

Max = 6-8 cc/kg

Inspiratory Trigger

Normally set automatically

2 modes:

Airway pressureFlow triggering

I:E Ratio

Normaly 1:2

Asthma/COPD 1:3, 1:4, …

Severe hypoxia

ARDS/ALI

Pul.Edema1:1 , 2:1

FIO2

Goal – to achive PaO2 > 60mmHg or a sat >90%

Start at 100% aim 40%

Vent settings to improve Vent settings to improve <oxygenation><oxygenation>

•FIO2

•Simplest maneuver to quickly increase PaO2

•Long-term toxicity at >60%• Free radical damage

•Inadequate oxygenation despite 100% FiO2 usually due to pulmonary shunting•Collapse – Atelectasis•Pus-filled alveoli – Pneumonia•Water/Protein – ARDS•Water – CHF•Blood - Hemorrhage

PEEP and FiO2 are adjusted in tandem

Positive End-expiratory Pressure (PEEP)

What is PEEP?

Positive pressure measured at the end of expiration.

What is the goal of PEEP? Improve oxygenation Recruit lung in ARDS Prevent collapse of alveoli Diminish the work of breathing

PEEP- Indications.

If a PaO2 of 60 mmHg cannot be achieved with a FiO2 of 60%

If the initial shunt estimation is greater than 25%

Pulmonary edema

ARDS/ALI

Atelectosis

PEEP

What are the secondary effec`ts of PEEP?BarotraumaDiminish cardiac outputRegional hypoperfusionAugmentation of I.C.P.?Paradoxal hypoxemiaHypercapnoea and respiratory acidosis

PEEP

Contraindication:BarotraumaAirway traumaHemodynamic instability I.C.P.?Bronchospasm?

Collapse/ atelectosis/ ARDS

Increases Surface area for gas exchangeOpens the collapsed lung

Collapsed alveoli

After PEEP

PEEP

Pulmonary edema

Translocation of fluid to peribroncheal region – helps in oxygenation

PEEP

Trouble Shooting

DOPE

D- Disposition of ETT

O- Obstruction / kinking

P- Pneumothorax

E- Equipment failure

Need for tracheostomyNeed for tracheostomyProlonged intubation may injure airway and cause airway edema

1 - Vocal cords. 2 - Thyroid cartilage. 3 - Cricoid cartilage. 4 - Tracheal cartilage. 5 - Balloon cuff.

Over viewType of patient Tidal Volume RR PEEP FIO2 Ins. Flow I:E Note Note

Normal 8 cc/kg 10 to 12 0 to 5 100%. 60 l/min 1:2.

ARDS 6 cc/kg 10 to 12 5 to 15 100%. 60 l/min 2:1 0r as needed

COPD 6 cc/kg 10 to 12 5 to 10 100%. 100 to 120 1:3 to 1:4 PH>7.2PCO2 <80 mmhgTrigger to consider

Trauma 8 cc/kg 10 to 12 0. 100%. 60 l/min 1:2.

Pediatric 8-10 cc/kg Varies age 3 to 5 100%. 60 l/min 1:2. Trigger to consider