1

OXYGEN THERAPY

& ARTIFICIAL

VENTILATION

Department of

Anaesthesiology & Intensive Medicine

Šafárik University Faculty of Medicine, Košice

MUDr. Jozef Firment, PhD.

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REASONS OF HYPOXEMIA

IN POSTOPERATIVE PERIOD

• FiO2 decrease?

• V/Q disturbances – the most frequent

• Lung shunts – secretions, atelectases

• Hypoventilation – anesthesia efects

• Difussion disturbances – interstitial lung

oedema

• Hypoxia from difusion N2O 40 x > N2

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PREDISPOSITION FACTORS

FOR RETENTION OF SECRETIONS

• Surgery site (thoracic, epigastrium >

hypogastrium)

• Preexist respiratory disease (infection,

hypersecretion)

• Smoking

• Obesity (FRC, WOB)

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BRONCHIAL SECRETIONS

RETENTION IN POSTOPERATIVE

PERIOD

• Expectoration insufficiency (painful wound,

sedation, muscle weakness K+, P)

• bronchial ciliary activity (dry inspir. gases,

anesthetics)

• Antisialogic medicaments (premedication)

• Infection (washing mechanisms failure)

= atelectases, WOB, hypoxemia,

global respir. insuficiency

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CONSEQUENCES OF

SECRETION RETENTION • Atelectasis:

during 24 h post surgery, fever 38-39oC,

tachycardia, tachypnoe, cough, cyanosis?, x-

ray - spot obscuration

• Bronchopneumonia:

Unusual lobar, elder pats., slower onset than

in atelectatic cause, fever, tachypnoe, x-ray –

more dense obscuration, especially basally

6 Duggan M., Kavanagh BP: Pulmonary Atelectasis. A Pathogenic Perioperative Entity.

Anesthesiology 2005; 102:838–54

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Duggan M., Kavanagh BP: Pulmonary Atelectasis. A Pathogenic Perioperative Entity. Anesthesiology 2005; 102:838–54

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LABORATORY

INVESTIGATIONS

• paO2, pcO2, pvO2 (ABR + pO2)

• possible mistakes and artefacts

steady state, taking of blood samples,

storage, laboratory

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CHANGES OF FRC AND PaO2

IN POSTOPERATIVE TIME

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POOSTOPERATIVE

PNEUMONIA TREATMENT

• ATB according to sputum cultivation

• Oxygen FiO2 0,3-0,4 according to ABB

• Artif. ventilat., non-responders to O2 and

activation of auxiliary respiratory

muscles, paO2, paCO2

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GAS

EXCHANGE

DURING HYPO-

VENTILATION

Aitkenhead

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WE

ST‘S

LU

NG

ZO

NE

S

Soni-O

HM

ED

A F

irm

ent

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VENTILATORY MECHANICS

Evita 2 dura Dräger 1999

ARTIFICIAL BREATHING ATELECTASES

zone > ventilation

zone > perfusion

SPONTANEOUS BREATHING

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SITUATIONS FOR LONGER OXYGEN

THERAPY DURING

POSTOPERATIVE PERIOD

• Hypotension

• IHD

• C.O.

• Anaemia

• Obesity

• Shivering

• Hypothermia

• Hyperthermia

• Lung oedema

• Airway

obstruction

• After large

procedures

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OXYGEN CASCADE

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OXYGEN THERAPY

• Every pt. 10 min after general

anaesthesia should obtain 100% oxygen

• Cave:

Recovery room

Postoperative dpt., ICU...

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HYPERBAROXIA

http://www.hyperbarickecentrum.sk/podstata.html

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HYPERBAROXIA

1. Air or Gas Embolism

2. Carbon Monoxide Poisoning

3. Clostridal Myositis and Myonecrosis (Gas Gangrene)

4. Crush Injury, Compartment Sy, & Acute Traumatic Ischemias

5. Decompression Sickness

6. Enhancement of Healing in Selected Problem Wounds

7. Exceptional Blood Loss (Anemia)

8. Intracranial Abscess

9. Necrotizing Soft Tissue Infections

10. Osteomyelitis (Refractory)

11. Delayed Radiation Injury (Soft Tissue and Bony Necrosis)

12. Skin Grafts & Flaps (Compromised)

13. Thermal Burns

http://www.uhms.org/Indications/indications.htm, http://www.oxynet.org/

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EQUIPMENT FOR OXYGEN

THERAPY

Spont inspiration - Peak Inspiratory Flow = 20 - 30 l/min

• Nasal sonds

• Oxygen „eye-glasses“

• Face mask

• Venturi mask 4l 28%, 8l 40%, 15l 60%)

• CPAP 10 cmH20

• Artifitial ventilation

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VENTI MASK

Cam

pbell

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Campbell O2 FiO2 VT x f

l/min %

adult: 13 85-100 1000 x 15

- “ - 4 >40 dtto

child 5 85-100 300 x 20

- “ - 2 >40 dtto

Inflow O2 10 - 13 l/min

SELF-EXPANDING BAG

WITH O2

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NECESSITY OF FiO2 CONTROL

• Normaly inspiratory force is regulated

by PaCO2 level (5,3 kPa)

• Patients regulated insiratory force by

paO2 (chronic bronchitis), 1-2 l/min O2,, 28% O2

• ARDS: paO2/FiO2 = shunt amount

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RE

SP

ON

SE

Pa

O2

TO

OX

YG

EN

AD

MIN

IST

RA

TIO

N norma = 3 - 8%

13,3

24

PO

SIT

ION

OF

A. &

V.

PO

INT

S IN

VA

RIO

US

pH

A

itkenhead

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Regulation of inspiratory

force by PaO2 decrease

In higher FiO2 threat

respiratory depresion

POSITION OF A. & V. POINTS

(PAT’S WITH CHRON. RESPIR. DISEASE)

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BYPASS OF NASAL CAVITY Water vapour content r.h. 100% in 37oC = 44 mg/l

V = 10 l/min 0,4 ml H2O/min, i.e. 24 ml H2O/hod

600 ml/24 hod

+ hyperventilation !

+ fever !

Inspiration of dry air =

= losses 700-1000 ml/day

Aim: humidification to 100% r.h.

warming 37oC

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CONSEQUENCES OF INSUFFICIENT

HUMIDIFICATION OF INSPIRATORY

GASES

• Losses of clear water from airway

• Concentration of secretions in airway

– failureof mucociliary transport

– airway obstruction

– development of atelektases

– airway infection

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AIMS OF VENTILATORY

SUPPORT

• Bypassing of critical time during illness.

• Achievement of acceptible oxygenation

and ventilation paremeters.

• Elimination of side effects of artifitial

ventilation.

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PHYSIOLOGICAL AIMS

1. Alveolar ventilation, paCO2, pH,

2. Oxygention support, paO2 above 8 kPa,

SaO2 above 90%, CaO2. Transport blood

capacity for oxygen (HB x SaO2 x C.O.)

3. Increase of lung volume (FRC) - PEEP

(against athelectases, improving of

oxygenation, ARDS, postoperative cases)

4. Decreasing work of respiratory muscles.

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CLINICAL AIMS 1. Treatment and reverse of hypoxaemia

2. Treatment of acute respiratory acidosis

3. Solution od respiratory distress

4. Prophylaxy and treatment of atelectases

5. Help for respiratopry muscle weakness

6. Permision of pts. sedation / relaxtion

7. Systemic and / or myocardial decreasing of oxygen consumption (cardiogenic shock, ARDS)

8. Decreasing of ICP through paCO2.

9. Thoracic wall stabilisation (flail chest)

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INDICATIONS FOR

ARTIFICIAL VENTILATION • Mechanics: f above 35/min, VC below 15

ml/kg, Insp.neg pressure below 25 cmH20.

• Oxygenation: paO2 below 70 mmHg at FiO2 0,4 by mask, AaDO2 above 350 mmHg at FiO2 1,0 or Qs/Qt above 20% (paO2/FiO2 below 200)

• Ventilation: Apnoe, paCO2 above 55 mmHg (except pat with chron. hyperkapnia), Vd/Vt above 0,60.

• Crucial are clinical findings!

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PHYSIOLOGICAL AND

PATHOPHYSIOLOGICAL PRINCIPLES

OF ARTIFITIAL VENTILATION

• Airway securing during ventilation

• Apparatuses and equipment used

during ventilation

• Tactics of ventilation, ventilatory modes

• Monitoring of ventilation

• Complications of ventilation

• Weaning from ventilator

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SOME PARAMETERS USED AS

INDICATORS OF ARTIFICIAL

VENTILATION

Parameter Physiologic

al values

Indications

for artificial

support

Vital capacity (ml/kg)

VD/VT

Inspiratory force (cmH2O)

Lung shunt (%) (Qs/Qt)

paO2 (kPa) (at FiO2 = 0,21)

p(A – a)DO2 (kPa) (at FiO2 = 0,21)

paO2/FiO2 (kPa)

paO2/FiO2 (mmHg)

paCO2 (kPa)

pH

Respiratory frequency

60 – 70

0,3

– (80 – 100)

5

13

1,3 – 4

> 40

> 300

5,3

7,35 – 7,45

12 – 18

10 – 15

0,6

< – 20

> 15

< 6,6

> 350

< 40

< 300

7,3 – 8

< 7,25

> 35 – 40

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AYRE T-PIECE

FGF < 2 x MV

Face mask Tube - orotracheal

- nasotracheal

- tracheostomy

22/15 mm

22 mm (20 cm 80ml)

Atmosphere Inlet O2

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• I:E Peak Flow %Ti

• Pause (%) Tip (s) from total respir. cycle

(S)CMV, Assist Control

37 Oh -

Firm

ent

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BLOOD GASES INFLUENCE BY

ARTIFICIAL VENTILATION

paCO2

• alveolar

ventilation

(VT, f, Pinsp ...)

paO2

• FiO2

• mean Paw

(PEEP,

I:E Peak Flow %Ti,

Pause (%) Tip (s) )