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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
• FiO 2 decrease?
• V/Q disturbances – the most frequent
• Lung shunts – secretions, atelectases
• Hypoventilation – anesthesia efects
• Difussion disturbances – interstitial lung
oedema
• Hypoxia from difusion N 2 O 40 x > N 2
2

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
4

CONSEQUENCES OF
SECRETION RETENTION
• Atelectasis:
during 24 h post surgery, fever 38-39 o C,
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
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Duggan M., Kavanagh BP: Pulmonary Atelectasis. A Pathogenic Perioperative Entity.
Anesthesiology 2005; 102:838–54
6

Duggan M., Kavanagh BP: Pulmonary
Atelectasis. A Pathogenic Perioperative
Entity. Anesthesiology 2005; 102:838–54
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LABORATORY
INVESTIGATIONS
• p a O 2 , p c O 2 , p v O 2 (ABR + pO 2 )
• possible mistakes and artefacts
steady state, taking of blood samples,
storage, laboratory
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CHANGES OF FRC AND PaO 2
IN POSTOPERATIVE TIME
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POOSTOPERATIVE
PNEUMONIA TREATMENT
• ATB according to sputum cultivation
• Oxygen FiO 2 0,3-0,4 according to ABB
• Artif. ventilat., non-responders to O 2 and
activation of auxiliary respiratory
muscles, p a O 2 , p a CO 2
10

Aitkenhead
GAS
EXCHANGE
DURING
HYPO-
VENTILATION
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12
WEST‘S LUNG ZONES
Soni-OHMEDA Firment

VENTILATORY MECHANICS
SPONTANEOUS BREATHING
zone > ventilation
zone > perfusion
ARTIFICIAL BREATHING
ATELECTASES
Evita 2 dura Dräger 1999
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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 cmH 2 0
• Artifitial ventilation
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Campbell
VENTI MASK
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Campbell
O 2 FiO 2 V T x f
l/min %
adult: 13 85-100 1000 x 15
- “ - 4 >40 dtto
child 5 85-100 300 x 20
- “ - 2 >40 dtto
SELF-EXPANDING BAG
WITH O 2
Inflow O 2
10 - 13 l/min
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NECESSITY OF FiO 2 CONTROL
• Normaly inspiratory force is regulated
by PaCO 2 level (5,3 kPa)
• Patients regulated insiratory force by
paO 2 (chronic bronchitis), 1-2 l/min O 2 , ,
28% O 2
• ARDS: paO 2 /FiO 2 = shunt amount
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norma = 3 - 8%
TO OXYGEN ADMINISTRATION
13,3
RESPONSE PaO 2
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POSITION OF A. & V.
POINTS IN VARIOUS pH
Aitkenhead
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POSITION OF A. & V. POINTS
(PAT’S WITH CHRON. RESPIR. DISEASE)
Regulation of inspiratory
force by PaO 2 decrease
In higher FiO 2 threat
respiratory depresion
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BYPASS OF NASAL CAVITY
Water vapour content r.h. 100% in 37 o C = 44 mg/l
V = 10 l/min 0,4 ml H 2 O/min, i.e. 24 ml H 2 O/hod
600 ml/24 hod
+ hyperventilation !
+ fever !
Inspiration of dry air =
= losses 700-1000 ml/day
Aim: humidification to 100% r.h.
warming
37 o C
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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
27

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, paCO 2 , pH,
2. Oxygention support, paO 2 above 8 kPa,
SaO 2 above 90%, CaO 2 . Transport blood
capacity for oxygen (HB x SaO 2 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 paCO 2 .
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 cmH 2 0.
• Oxygenation: paO 2 below 70 mmHg at FiO 2
0,4 by mask, AaDO 2 above 350 mmHg at
FiO 2 1,0 or Qs/Qt above 20% (paO 2 /FiO 2
below 200)
• Ventilation: Apnoe, paCO 2 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
Parameter
VENTILATION
Physiologic
al values
Indications
for artificial
support
Vital capacity (ml/kg)
V D
/V T
Inspiratory force (cmH 2
O)
Lung shunt (%) (Q s
/Q t
)
paO 2
(kPa) (at FiO 2
= 0,21)
p(A – a)DO 2
(kPa) (at FiO 2
= 0,21)
paO 2
/FiO 2
(kPa)
paO 2
/FiO 2
(mmHg)
paCO 2
(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
Inlet O 2
FGF < 2 x MV
22 mm (20 cm 80ml)
Atmosphere
22/15 mm
Face mask Tube - orotracheal
- nasotracheal
- tracheostomy
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(S)CMV, Assist Control
• I:E Peak Flow %Ti
• Pause (%) Tip (s) from total respir. cycle
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37
Oh - Firment

BLOOD GASES INFLUENCE BY
ARTIFICIAL VENTILATION
p a CO 2
• alveolar
ventilation
(VT, f, P insp ...)
• FiO 2
p a O 2
• mean P aw
(PEEP,
I:E Peak Flow %Ti,
Pause (%) Tip (s) )
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