 Introduction
 Physiological Aspects
 Monitoring Requirements
Page  2
Thoracic anesthesia is challenging
Patient
Page  4
Procedure
 “V" - ventilation - the air which reaches the lungs
 "Q" - perfusion - the blood which reaches the lungs
 Normal V is 4 L of air per minute.
 Normal Q is 5L of blood per minute.
 So Normal V/Q ratio is 4/5 or 0.8.
 When the V/Q is higher than 0.8, it means ventilation exceeds
perfusion.
 When the V/Q is < 0.8, there is a VQ mismatch caused by
poor ventilation
Page  6
 An area with no ventilation (and thus a V/Q of zero) is termed
"shunt."
 An area with no perfusion (and thus a V/Q of infinity) is
termed “dead space”
Page  7
 A change in volume
divided by a change in
transpulmonary
pressure.
 (CL = ΔV / ΔPL)
 A typical value of
compliance is 200
ml/cm H20
Page  8
Alter the normal pulmonary ventilation/perfusion
relationships accentuated by
Induction of anesthesia Initiation of mech.ventilation
Opening the chest
Page  10
Surgical retractions
Perfusion
Ventilation
Page  11
Pulmonary blood flow distribution relative to the
alveolar pressure
The dependent lung is better
Ventilated than the
Nondependent lung,
˙V/˙ Q still is well matched.
Patient awake spontaneously breathing
Page  12
Page  13
Page  14
Page  15
The principle physiologic change of OLV is the
redistribution of lung perfusion between the
ventilated (dependent) and blocked (nondependent)
lung
Many factors contribute to the lung perfusion, the
major determinants of them are hypoxic pulmonary
vasoconstriction, HPV and gravity.
Page  16
HPV is a widely conserved, homeostatic, vasomotor
response of precapillary smooth muscle in the PAs to
alveolar hypoxia. HPV mediates ˙V/˙Q matching and, by
reducing shunt fraction, optimizes systemic pO2.
Page  17
Reduces the surface area available for gas exchange
Reduced arterial oxygen tension
Maintaining oxygenation
and
elimination of carbon dioxide
is the greatest challenge
Page  18
Page  19
Use of Monitoring to Detect and Diagnose
Intraoperative Events
 Respiration
 Oxygenation
 Ventilation
 Cardiovascular function
Page  20
Pattern,
respiratory rate
• Apnea, respiratory difficulty,
rales
Auscultation
• Wheezing, rhonchi, apnea,
compliance
Airway
pressure
• Obstruction, pneumothorax,
bronchospasm,secretions
Page  21
FiO2 analyzer
Pulse oximetry
Arterial blood
gas
Page  22
• Inadvertent hypoxia
• Hypoxia, integrity of pulse
• Acidosis (metabolic, respiratory)
Capnography
•
•
•
•
Bronchospasm
Hypoventilation and apnea
Confirm endotracheal intubation
Return of spontaneous ventilation during controlled
ventilation
Page  23
Electrocardiography
Arrhythmia, ischemia
Intraarterial catheter
Hypotension or hypertension
Arterial compression
Page  24
Pulmonary artery catheter
Pulmonary hypertension, filling pressures, assess
cardiac performance
SvO2
Adequacy of cardiac output
Page  25
Transesophageal Echocardiography
Ischemia, volume status, right ventricular
dysfunction
Page  26
Failure to check the equipment properly
before induction of anesthesia is
responsible for 22% of the
critical incidents that occur during anesthesia
Page  27
Tier I
Page  28
Patient
Procedure
Healthy patients
no special intraopertive conditions
Sick patients
special intraopertive conditions
Gas
exchange
Airway
mechanics
Endotracheal
tube position
PA
pressures
Cardiovascular status
Color of
tissues and
shed blood
Spo2, PETCO2
Feel of the
breathing bag,
stethoscope,
PIP, PETCO2
EBBS
Ballotable
balloon in
SSN, FOB
after
placed in LDP
Not measured
NIBP, pulse
oximeter
waveform,
ECG, PETco2
esophageal
stethoscope,
± CVP, ±
invasive
arterial
pressure
monitoring
Page  29
Page  30
Tier II
Page  31
Patient
Procedure
Healthy patients
no special intraopertive conditions
Sick patients
special intraopertive conditions
Tier II
Page  32
Patient
Procedure
Healthy patients
no special intraopertive conditions
Sick patients
special intraopertive conditions
Gas
exchange
Airway
mechanics
As above plus
frequent ABG
studies
As above plus
spirometry.
Individual and
whole-lung
compliance
Page  33
Endotracheal
tube position
PA
pressures
FOB to verify
Measure Ppa
tube position
if lobectomy or
while in supine lung resection
position, as
well as in the
LDP
Cardiovascular status
As above, plus
invasive
arterial
pressure
monitoring, +
CVP, + PA
catheter (if
poor EF, PA,
HTN), ± TEE
 Spirometry is a non-invasive monitor device which measures
volume, pressure and flow in the airway.
 These measurements may be used to construct :
 a pressure-volume curve (PV) and
 a flow-volume curve (FV).
 The constructed curves will give important information about
the peri-operative respiratory function.
Page  34
Tier III
Page  35
Patient
Procedure
Healthy patients
no special intraopertive conditions
Sick patients
special intraopertive conditions
Gas
exchange
Airway
mechanics
As above plus As above plus
Qs/Qt, VD/Vt
airway
frequent VBGs resistance
Page  36
Endotracheal
tube position
PA
pressures
As above plus
frequent
rechecks
to verify
position
Measure PA
,Q , PVR ,
SVR, Dao2 –
Dvo2
Cardiovascular status
As above plus
PA , TEE
Page  37
Measured values:
 CVP: 1-6 mm Hg (reflects right atrial pressure).
 PAP: Systolic 15-30mm Hg, Diastolic 6-12mm Hg.
 PCWP: 6 - 12mm Hg. Estimates left atrial heart pressure and
left ventricular end diastolic pressure.
 CO: 3.5 - 7.5 L/min
 Sv02: (70 - 75%). Drawn from the end of the pulmonary
artery catheter. Used to calculate how well oxygen is
extracted by the tissues.
Page  38
Page  39
 the LDP is important with regard to pulmonary artery catheter
monitoring in three situations.
 The catheter is in the nondependent collapsed lung, the
measured cardiac output and mixed venous blood (pvo2)
may be decreased.
 When the nondependent lung is ventilated with PEEP and the
catheter is in the nondependent lung, Ppaw may not equal
Pla.
 When the catheter is in the dependent lung, Ppaw will be a
faithful index of Pla, even if PEEP is used
Page  40
Monitors are useful adjuncts, But they alone
cannot replace
Careful observation by Anaesthesiologist.
Page  41