Transcript Status epilepticus

Oxygenation & Ventilation
Monitoring
Point of Discussion
• Variable and fixed performance Oxygen
devices
• Pulse oximetry
• A-a gradient
• Ventilation equation
• Capnography
• Arterial and venous blood gases
THE OXYGENATION VITAL
SIGN
O2-Hg Dissociation Curve
100%
Hb Saturation (%)
90%
60
90
PaO2 (mm Hg)
600
Oxygen Saturation Monitoring
by Pulse Oximetry
Oxygen Saturation Monitoring by
Pulse Oximetry
Patient Environments
• Ambient Light
– Any external light exposure to capillary bed where sampling is
occurring may result in an erroneous reading
• Excessive Motion
– Always compare the palpable pulse rate with the pulse rate
indicated on the pulse oximetry
• Fingernail polish and false nails
– Most commonly use nails and fingernail polish will not affect pulse
oximetry accuracy
– Some shades of blue, black and green may affect accuracy
(remove with acetone pad)
• Skin pigmentation
– Apply sensor to the fingertips of darkly pigmented patients
Conditions Affecting Accuracy
• Patient conditions
– Carboxyhemoglobin
• Erroneously high reading may present
– Methaemoglobin
– Anemia
• Values as low as 5 g/dl may result in 100% SpO2
– Hypovolemia/Hypotension:
• May not have adequate perfusion to be detected by oximetry
– Hypothermia:
• peripheral vasoconstriction may prevent oximetry detection
Nasal Cannula: Variable Flow
Simple Face Mask: Variable Flow
Venturi Mask: Fixed Flow
blue = 24%; yellow = 28%; white = 31%;
green = 35%; pink = 40%; orange = 50%
Venturi Effect
The pressure at "1" is higher than at "2" because the
fluid speed at "1" is lower than at "2".
Venturi Effect
35-45 L/min
4-15 L/min
A flow of air through a venturi meter, showing the
columns connected in a U-shape (a manometer) and
partially filled with water. The meter is "read" as a
differential pressure head in cm or inches of water.
Variable Performance Device:
Nonrebreather Mask
100
Fractional inspired oxygen concentration %
90
5 L.min-1
80
10 L.min-1
70
20 L.min-1
60
30 L.min-1
50
40
30
20
10
0
5
15
55
25
45
65
35
Peak inspiratory flow (liters/minute)
75
85
Continuous Airway Pressure: CPAP
Alveolar-arterial Oxygen Gradient
PAO2= (Patm-PH2O) FiO2- PACO2/0.8
19
760
47
0.21
40
Alveolar Arterial O2 Gradient
Po2
Po2
A-a Gradient
initial
Alveolar Gas
Initial
Thickness
Capillary Blood
Alveolar Arterial O2 Gradient
FIO2= 21%
PAO2= 100
FIO2= 50%
PAO2= 331
FIO2= 100%
PAO2= 663
Alveolar Gas
5
Thickness
PaO2= 95
O2 Sat= 99%
PaO2= 326
O2 Sat= 100%
PaO2= 657
O2 Sat= 100%
Capillary Blood
Alveolar Arterial O2 Gradient
FIO2= 50%
FIO2= 100%
PAO2= 331
PAO2= 663
Alveolar Gas
200
Thickness
PaO2= 131
O2 Sat= 100%
PaO2= 463
O2 Sat= 100%
Capillary Blood
THE VENTILATION VITAL
SIGN
PaCO3 Equation
Low Production
High Production
•
•
•
•
•
•
•
•
•
•
Hypothermia
Hyporthyroidism
Underfeeding
Neuromuscular blockade
High fatty acid substrate
PaCO2=
Cell
Metabolism
.
VCO2
VE * (1- VD/VT)
Respiratory
Rate
Tidal
Volume
Sepsis/inflammation
Hyperthermia
Hyperthyroidism
High carbohydrates
Seizure and agitation
VDequip
HME
VDanat
VDA
PEEP
Low BP
Dead Space
VDA
ETT
VDequip
Airways
VDanat
Semi-Quantitative Capnometry
• Relies on pH change
• Paper changes color
– Purple to Brown to Yellow
Hypercapnia
↑VCO2
↑PaCO=2 ----------------------↔VA = VE – VD
Increased CO2 production but not able to hyperventilate:
Fever
Sepsis
Hyperthyroidism
Overfeeding with carbohydrates
Agitation
Hypercapnia
↔VCO2
↑PaCO=2 ----------------------↓VA = ↓VE – VD
Decreased Alveolar Ventilation due to
Decreased Minute Ventilation (VE= ↓VT X ↓RR)
Sedative drug overdose
Respiratory muscle paralysis
Central hypoventilation
Hypercapnia
↔VCO2
↑PaCO=2 ----------------------↓VA = VE – ↑VD
Decreased Alveolar Ventilation due to Increased
Dead Space Ventilation (VD= Dead Space Volume X
RR)
Pulmonary embolism
High PEEP
Pulmonary hypertension
Chronic obstructive pulmonary disease
Hypocapnia
↓VCO2
↓PaCO=2 ----------------------↔VA = VE – VD
Decreased CO2 production but same minute ventilation:
Hypothermia
Paralysis
Hypothyroidism
Underfeeding with carbohydrates
Sedation
Hypocapnia
↔VCO2
↓PaCO=2 ----------------------↑VA = ↑VE – VD
Increased Alveolar Ventilation due to Increased
Minute Ventilation (VE= ↑ VT X ↑ RR)
CNS stimulants
Agitation
Central hyperventilation
Eucapnia
↑VCO2
↔PaCO=2 ----------------------↑VA = ↑VE – VD
Increased CO2 production and Increased
Alveolar Ventilation:
Fever and sepsis
Hyperthyroidism
Agitation
Eucapnia
↓VCO2
↔PaCO=2 ----------------------↓VA = ↓VE – VD
Decreased CO2 production and decreased
Alveolar Ventilation
Hypothermia
Hypothyroidism
PCO2 vs. Alveolar Ventilation
The relationship is shown for
metabolic carbon dioxide
production rates of 200 ml/min
and 300 ml/min (curved lines). A
fixed decrease in alveolar
ventilation (x-axis) in the
hypercapnic patient will result in a
greater rise in PaCO2 (y-axis)
than the same VA change when
PaCO2 is low or normal.
This graph also shows that if
alveolar ventilation is fixed, an
increase in carbon dioxide
production will result in an
increase in PaCO2.
PaCO2 and Alveolar Ventilation:
Test Your Understanding
What is the PaCO2 of a patient with respiratory rate
24/min, tidal volume 300 ml, dead space volume 150
ml, CO2 production 300 ml/min? The patient shows
some evidence of respiratory distress.
PaCO
=
2=71.9
PaCO
VCO
VCO
=259
X .863
VCO
X
0.863
2=300
2
2
----------------------2
VA = VE – VD
VE
(7.2)
–VD
VD(150
(3.6)X 24)
VA = VA
VE =
(300X24)
VA
= –3.6
PaCO2 and Alveolar Ventilation:
Test Your Understanding
What is the PaCO2 of a patient with respiratory rate
10/min, tidal volume 600 ml, dead space volume 150
ml, CO2 production 200 ml/min? The patient shows
some evidence of respiratory distress
VCO2 X 0.863
PaCO=2 ----------------------VA = VE – VD
PaCO2 and Alveolar Ventilation:
Test Your Understanding
A man with severe chronic obstructive pulmonary disease
exercises on a treadmill at 3 miles/hr. His rate of CO2
production increases by 50% but he is unable to augment
alveolar ventilation. If his resting PaCO2 is 40 mm Hg and
resting VCO2 is 200 ml/min, what will be his exercise PaCO2?
↑300
200 X
0.863
VCO
X0.863
0.863
2X
=
----------------------PaCO
PaCO
PaCO
=59.9
=40
2
22
VA
VA==4.32
VE –L/min
VD
Effective Ventilation
VDA
ETT
VDequip
Airways
VDanat
VT= 500
RR= 10
VDequip= 50
VDanat= 125
VDA= 25
VTe= 300
VT= 250
RR= 20
VDequip= 50
VDanat= 125
VDA= 25
VTe= 50
VE= 5 L/min
NORMAL CAPNOGRAM
Phase I: anatomical dead space
mm Hg
70
60
50
Phase II : alveolar gas begins to
mix with the dead space gas
Phase I Phase II
Phase III
Phase III: elimination
of CO2 from the
alveoli
40
Phase IV
PetCO2
30
20
10
0
Time
Expiratory Phase
Inspiratory Phase
NORMAL Waveform
• Square box waveform
• ETCO2 35-45 mm Hg
• Management: Monitor Patient
mm Hg
70
60
50
40
30
20
10
0
Time
Sudden  in ETCO2 to 0
mm Hg
70
• Loss of waveform
• Loss of ETCO2 reading
• Dislodged tube
• ET obstruction
• Management: Replace ETT
60
50
40
30
20
10
0
Time
Esophageal Intubation
• Absence of waveform
• Absence of ETCO2
• Management: Re-Intubate
mm Hg
70
60
50
40
30
20
10
0
Time
CPR
mm Hg
• Square box waveform
• ETCO2 15-20 mm Hg with adequate CPR
• ETCO2 falls bellow 10 mm Hg
• Management: Change Rescuers
70
60
50
40
30
20
10
0
Time
Return of Spontaneous Circulation
• During CPR sudden increase of ETCO2 above
10-15 mm Hg
• Management: Check for pulse
mm Hg
70
60
50
40
30
20
10
0
Time
Gradual Decrease in ETCO2
• Hyperventilation
• Decreasing temp
• Gradual  in volume
mm Hg
70
60
50
40
30
20
10
0
Time
Hyperventilation
mm Hg
• Shortened waveform
• ETCO2 < 35 mm Hg
• Management: If conscious gives biofeedback. If ventilating
slow ventilations
70
60
50
40
30
20
10
0
Time
Gradual Increase in ETCO2
• Fever
• Hypoventilation
mm Hg
70
60
50
40
30
20
10
0
Time
Hypoventilation
• Prolonged waveform
• ETCO2 >45 mm Hg
• Management: Assist ventilations
mm Hg
70
60
50
40
30
20
10
0
Time
Rising Baseline
• Patient is re-breathing CO2
• Management: Check equipment for adequate oxygen flow
• If patient is intubated allow more time to exhale
mm Hg
70
60
50
40
30
20
10
0
Time
Curare Cleft
•
mm Hg
70
•
•
Curare Cleft is when a neuromuscular blockade
wears off
The patient takes small breaths that causes the cleft
Management: Consider neuromuscular blockade
re-administration
60
50
40
30
20
10
0
Time
Breathing around ETT
mm Hg
• Angled, sloping down stroke on the waveform
• In adults may mean ruptured cuff or tube too small
• Management: Assess patient, Oxygenate, ventilate and
possible re-intubation
70
60
50
40
30
20
10
0
Time
Obstructive Airway
mm Hg
• Shark fin waveform
• With or without prolonged expiratory phase
• Can be seen before actual attack
• Indicative of Bronchospasm( asthma, COPD, allergic reaction)
70
60
50
40
30
20
10
0
Time
BLOOD GASES
Acidemia or Alkalemia
Is there
Is the PaCO2
Is the HCO3-
It is
Acidaemia
High
Normal/high
Respiratory
acidosis
Acidaemia
Low
Low
Metabolic
acidosis
Alkalaemia
Low
Normal/low
Respiratory
alkalosis
Alkalaemia
High
High
Metabolic
alkalosis
Respiratory process: acute
or chronic ?
• Respiratory Acidosis Acute :
 pH= 0.08x(PaCO2-40)/10
• Respiratory Acidosis Chronic :
 pH= 0.03x(PaCO2-40)/10
• Respiratory Alkalosis Acute :
 pH= 0.08 x (40-PaCO2)/10
• Respiratory Alkalosis Chronic :
 pH= 0.03 x (40-PaCO2)/10
Metabolic acidosis
• Anion gap vs. Nongap acidosis
• Anion gap (AG) = Na-Cl-HCO3
Adequate degree of compensation?
Primary
problem
Compensation
Metabolic Acidosis
Respiratory alkalosis
Metabolic Alkalosis
Respiratory acidosis
Respiratory Acidosis Acute
Metabolic Alkalosis
Respiratory Acidosis
Chronic
Metabolic Alkalosis
Respiratory Alkalosis Acute
Metabolic Acidosis
Respiratory Alkalosis
Chronic
Metabolic Acidosis
For every  in
Expected 
1
↓ HCO3
PaCO2
↓ 1.2
1
↑ HCO3
PaCO2
↑ 0.6
1
↑ PaCO2
HCO3
↑ 0.1
1
↑ PaCO2
HCO3
↑ 0.4
1
↓ PaCO2
HCO3
↓ 0.2
1
↓ PaCO2
HCO3
↓ 0.4
Adequate degree of compensation
for Metabolic Acidosis ?
• Calculated PaCO2=(1.5 x HCO3) +8±2
• Measured PaCO2>Calculated PaCO2 then
concomitant respiratory acidosis
• Measured PaCO2<Calculated PaCO2 then
concomitant respiratory alkalosis
Delta Delta  
•  HCO3 = Normal HCO3- Measured
HCO3
•  AG= Measured AG-Normal AG
•  HCO3 >  AG: associated metabolic
alkalosis
•  HCO3 <  AG: associated nongap
metabolic acidosis
ABG Problems:
• 7.2/26/85/95% on RA





145
100
16
4.0
12
1.0
Metabolic acidosis
145-(100-12)=AG =33
Expected PaCO2 1.5x12 +8 ±2=26±2
appropriate
 AG= 21 >  HCO3= 12
Concomitant metabolic alkalosis
ABG Problems
• 7.1/35/60/90% on RA







135
106
16
4.2
10
1.0
Metabolic acidosis
135-106-10 = AG 19
Expected PaCO2 1.5 x 10 +8 ±2=23±2 Measured
>calculated
Concomitant respiratory acidosis
 AG= 7 <  HCO3= 14
Concomitant nongap metabolic acidosis
Next calculate UAG
7.0
100
90
6
9
12
15
18
HCO3-(mmol/l)
21
24
27
30
80
7.1
33
70
36
39
42
45
48
51
57
63
69
74
H+ (nmol/l)
60
50
40
N
30
7.2
7.3
7.4
7.5
7.6
7.7
7.8
8.0
20
10
8.5
0
PCO2 (kPa)
THANK YOU
Ventilator Course in Sudan: December 15-16, 2011