Dr Chaitanya VemuriInt.Med M.D Trainee

The choice of ventilator settings – guided by clearly defined therapeutic end points.

In most of cases : primary goal is to correct abnormalities of arterial blood gas tensions

Accomplished by adjusting minute volume - to correct

hypercapnea oxygen supplementation – to correct

hypoxemia

Choice of inspired gas composition

Means to ensure the machine’s sensing of patient’s demand

Definition of machine’s mechanical output

Confirm indication for mechanical ventilation

Invasive / Non invasive Check Connections & Circuit Self test Select mode Set variables Alarm settings Connect to patient Monitor and reassess

Patient not breathing Patient breathing but not enough Patient breathing enough, but pt

hypoxemic / hypercapneic Patient breathing with normal gas

exchange, but working hard Airway protection

LABORATORY CRITERIA

CLINICAL CRITERIA

OTHER CRITERIA

Blood gases : PaO2 < 55 mm Hg PaCo2 > 50 mm Hg pH < 7.32

PFT : Vital Capacity < 10 ml/Kg -ve inspiratory force <25cm H20 FEV 1 < 10 mL/Kg

Apnea / Hypopnea Respiratory distress with altered

mentation Clinically apparent increasing work of

breathing unrelieved by other interventions

Need for airway protection

Controlled hyperventilation ( eg head injury )

Severe circulatory shock

THERE IS NO ABSOLUTE CONTRAINDICATION FOR MECHANICAL VENTILATION

To check : - leak - compliance - resistance of circuit - sensors Needs to be done : - before connecting to

patient - once in 2 weeks - whenever circuit is changed

Depends on : Patients requirement User comfort Availability

For PO2 : adjust FiO2, PEEP

For PCo2 : adjust TV , RR

Tailored to need of the patient

SIMV / A/C – versatile modes for initial settings

In pts with good resp drive & mild – mod resp failure – PSV

Initial TV : 5 – 8 ml/Kg of ideal bd wt Lowest values are recommended in

presence of Obstructive airway ds & ARDS

Goal : to adjust TV so that plateau pressures are less than 35 cm H20

8 – 12 breaths per minute : pts not requiring hyperventilation for treatment of toxic/metabolic acidosis or intracranial injury

Initial rate may be low ( 5 – 6 breaths per min ) in asthmatic pts where permissive hypercapnic technique is used

Lowest FiO2 that produces an Sp02 > 90 % PaO2 > 60 mm Hg is recommended

Normal I:E ratio to start is 1:2

Reduced to 1:4 or 1:5 in presence of obstructive airway disease in order to air trapping

Inverse I:E – in ARDS

60 L/min is typically used

Increased to 100 L/min : to deliver TVs quickly and allow for prolonged expiration in presence of obstructive airway ds

Titrated according to PEEP and BP High PEEP ( > 10 H20 ) – pneumonia, ards PEEP – reduces risk of atelectasis - increase no of open alveoli ( decrease V/Q mismatch ) - in CHF : decrease venous return Physiological PEEP ( 3-5 cm H20 ) : to

prevent decrease in FRC in normal lungs

Set at -1 to -2 cm H20

NEWER VENTILATORS SENSE INSPIRATORY FLOW

and thereby reduce work of breathing associated with ventilator triggering

Mode : Complete / Partial . VCV/PCV Rate : titrate to Pco2 Tidal Volume : 5 – 8 ml / Kg Flow rate & Pattern : 4 – 8 times Minute

Ventilation I:E = 1:2 to 1:4 FiO2 : titrate to O2 Saturation / Pa O2 PEEP : titrate to PaO2 & BP Trigger : Adjust to synchronize

Fixed alarms : disconnection o2 sensor

Set alarms : volume pressure rate apnea

Patient Monitor : pulse , bp , rr, spO2 Ventilator Abg Volume Pressure Rate Patient comfort / synchrony

For Paralysed pts : CMV or A/C mode

For Non paralysed pts : SIMV mode

Pts with normal resp effort mild resp failure : PSV mode

Hypoxia corrected by High FiO2

Increase Expiratory Flow Time to max : to prevent increase intrinsicPEEP

RR : 6 -8 breaths / min ( permissive hypercapnia )

I : E : increased 1:2

A/C mode Tidal Volume : 6 ml/Kg PEEP : 5 Ventilatory rate : 12 titrated to maintain Ph > 7.25

Respond well to positive pressure ventilation (opens alveoli, reduces preload)

Many benefit from trial of noninvasive CPAP / BiPAP

Intubated pts usually manage to oxygenate well

But PEEP can be increased to improve oxygenation and reduce preload