Upload
sama
View
2.293
Download
3
Tags:
Embed Size (px)
Citation preview
10/2/2012 1
ACUTE RESPIRATORY FAILURE
Ihab B Abdalrahman, MBBS, MD, ABIM, SSBB Ihab Tarawa Consultant of Acute Care Medicine, Soba University Hospital
10/2/2012 Ihab Tarawa 2
BASIC RESPIRATORY PHYSIOLOGY
Respiratory system made ridiculously easy
It is as simple as moving the air in and out.
Allowing gas exchange.
10/2/2012 Ihab Tarawa 3
O2 CO2
10/2/2012 Ihab Tarawa 4
1,2,3
Bottom line of the respiratory system is to
Let oxygen in,
And carbon dioxide out.
10/2/2012 Ihab Tarawa 5
Definitions
acute respiratory failure occurs when:
pulmonary system is no longer able to meet the metabolic demands of the body
hypoxaemic respiratory failure:
PaO2 8 kPa when breathing room air
hypercapnic respiratory failure:
PaCO2 6.7 kPa
10/2/2012 Ihab Tarawa 6
Oxygen in Depends on Ventilation
PAO2
Perfusion
Ventilation-perfusion matching
Diffusing capacity
10/2/2012 Ihab Tarawa 7
PAO2
The alveolar pressure is equal to the sum of the partial pressures of the gases within the alveolus.
The partial pressure of each gas is proportional to the concentration of the gas.
10/2/2012 Ihab Tarawa 8
2A2A2A2A NPOHPCOPOPpressure Alveolar
Nitrogen
Water vapour
Carbon dioxide
Oxygen
10/2/2012 Ihab Tarawa 9
Nitrogen
Water vapour
Carbon dioxide
Oxygen
2A2A2A2A NPOHPCOPOPpressure Alveolar
10/2/2012 Ihab Tarawa 10
Nitrogen
Water vapour
Carbon dioxide
Oxygen
2A2A2A2A NPOHPCOPOPpressure Alveolar
10/2/2012 Ihab Tarawa 11
Oxygen in
Depends on PAO2
FIO2
Alveolar pressure
PACO2
Ventilation
Ventilation-perfusion matching
Perfusion
Diffusing capacity
10/2/2012 Ihab Tarawa 12
Ventilation-perfusion matching
10/2/2012 Ihab Tarawa 13
Carbon dioxide out
Largely dependent on alveolar ventilation
Anatomical dead space constant but physiological dead space depends on ventilation-perfusion matching
10/2/2012 Ihab Tarawa 14
)V-(V xRR nventilatio Alveolar DT
Carbon dioxide out
Respiratory rate
Tidal volume
Ventilation-perfusion matching
10/2/2012 Ihab Tarawa 15
10/2/2012 Ihab Tarawa 16
PATHOPHYSIOLOGY
PAO2=14.74 kPa PACO2=5 kPa
75% 100%
Normal
ventilation &
perfusion
10/2/2012 Ihab Tarawa 17
Pathophysiology
Low inspired Po2
Although, in theory, acute respiratory failure may result from a low inspired PO2 this is rarely a problem in Intensive Care except in locations at high altitude.
10/2/2012 Ihab Tarawa 18
Pathophysiology
Low inspired oxygen concentration
Hypoventilation
10/2/2012 Ihab Tarawa 19
Nitrogen
Water vapour
Carbon dioxide
Oxygen
2A2A2A2A NPOHPCOPOPpressure Alveolar
10/2/2012 Ihab Tarawa 20
PAO2=9.74 kPa PACO2=10 kPa
75% 92%
Hypoventilation
10/2/2012 Ihab Tarawa 21
Brainstem
Spinal cord
Nerve root Airway
Nerve
Neuromuscular junction
Respiratory muscle
Lung
Pleura
Chest wall
Sites at which disease may cause hypoventilation 10/2/2012 Ihab Tarawa 22
Brainstem
Spinal cord
Nerve root Airway
Nerve
Neuromuscular junction
Respiratory muscle
Lung
Pleura
Chest wall
Sites at which disease may cause hypoventilation 10/2/2012 Ihab Tarawa 23
Pathophysiology
Low inspired oxygen concentration
Hypoventilation
Shunting
Dead space ventilation
Diffusion abnormality
10/2/2012 Ihab Tarawa 24
Shunt
10/2/2012 Ihab Tarawa 25
75% 75%
100% 75%
87.5%
oxygen therapy
has relatively
little effect on
hypoxia due to
shunting.
10/2/2012 Ihab Tarawa 26
75% 75%
100% 75%
90%
hypoxic vasoconstriction
↓perfusion to non-ventilated alveoli
↑perfusion to ventilated alveoli,
↓ magnitude of the shunt
↑and increasing the arterial saturation
10/2/2012 Ihab Tarawa 27
Shunting
Intra-pulmonary Pneumonia
Pulmonary oedema
Atelectasis
Collapse
Pulmonary haemorrhage or contusion
Intra-cardiac Any cause of right to left shunt eg Fallot’s, Eisenmenger,
Pulmonary hypertension with patent foramen ovale
10/2/2012 Ihab Tarawa 28
Pathophysiology
Low inspired oxygen concentration
Hypoventilation
Shunting
Dead space ventilation
Diffusion abnormality
10/2/2012 Ihab Tarawa 29
Dead space ventilated but not perfused
10/2/2012 Ihab Tarawa 30
Pathophysiology
Low inspired oxygen concentration
Hypoventilation
Shunting
Dead space ventilation
Diffusion abnormality
10/2/2012 Ihab Tarawa 31
10/2/2012 Ihab Tarawa 32
Diffusion abnormalities.
These can result from a failure of diffusion across the alveolar membrane
or a reduction in the number of alveoli resulting in a reduction in the alveolar surface area.
Causes include ARDS and fibrotic lung disease
10/2/2012 Ihab Tarawa 33
10/2/2012 Ihab Tarawa 34
RESPIRATORY MONITORING
Clinical
Respiratory compensation
Sympathetic stimulation
Tissue hypoxia
Haemoglobin desaturation
10/2/2012 Ihab Tarawa 35
Bottom line of the respiratory system is to let oxygen in and CO2 out.
Some sensors will go off
Hypoxia
Acidosis
10/2/2012 Ihab Tarawa 36
10/2/2012 Ihab Tarawa 37
Clinical
Respiratory compensation Tachypnoea
Accessory muscles
Recession
Nasal flaring
10/2/2012 Ihab Tarawa 38
Clinical
Sympathetic stimulation
10/2/2012 Ihab Tarawa 39
Clinical
Sympathetic stimulation
HR
BP (early)
sweating
10/2/2012 Ihab Tarawa 40
Point of making a difference
Coming for help
Or coming with a coffin
10/2/2012 Ihab Tarawa 41
Clinical
Tissue hypoxia
Altered mental state
HR and BP (late)
10/2/2012 Ihab Tarawa 42
Clinical
Haemoglobin desaturation
cyanosis
10/2/2012 Ihab Tarawa 43
If we wait for the patient to become cyanosed
10/2/2012 Ihab Tarawa 44
PaO2 (kPa)
Hb s
atu
rati
on (
%)
8
90
Pulse oximetry, notice the sigmoid curve
10/2/2012 Ihab Tarawa 45
The oxygen content of blood is mainly dependent on:
the haemoglobin saturation,
with the a very small contribution from dissolved oxygen.
10/2/2012 Ihab Tarawa 46
Oxygen delivery
10/2/2012 Ihab Tarawa 47
222
2 2
PaO0.0031.37Hbsaturation O content O
10contentOoutput CardiacdeliveryO
Monitoring
10/2/2012 Ihab Tarawa 48
123
80 40
87% HR=95
10/2/2012 Ihab Tarawa 49
Sources of error
Poor peripheral perfusion
Poorly adherent/positioned probe
False nails or nail varnish
Lipaemia
Bright ambient light
Excessive motion
Carboxyhaemoglobin or methaemoglobin
10/2/2012 Ihab Tarawa 50
Thing to remember
Saturation is not a measure of
ventilation
10/2/2012 Ihab Tarawa 51
Summary
worry if RR > 30/min (or < 8/min) unable to speak 1/2 sentence without pausing agitated, confused or comatose cyanosed or SpO2 < 90% deteriorating despite therapy
remember normal SpO2 does not mean severe ventilatory problems are not
present
10/2/2012 Ihab Tarawa 52
10/2/2012 Ihab Tarawa 53
TREATMENT
Treatment
Treat the cause Supportive treatment
Oxygen therapy
CPAP
Mechanical ventilation
10/2/2012 Ihab Tarawa 54
Oxygen therapy
Fixed performance devices
Variable performance devices
10/2/2012 Ihab Tarawa 55
Nasal canula
Simpler mask
Other
10/2/2012 Ihab Tarawa 56
Other devices
Reservoir face mask
Bag valve resuscitator
10/2/2012 Ihab Tarawa 57
CPAP
reduces shunt by recruiting partially collapsed alveoli
10/2/2012 Ihab Tarawa 58
10/2/2012 Ihab Tarawa 59
Pressure
Volu
me
Lung compliance and FRC
reduces work of breathing
10/2/2012 Ihab Tarawa 60
Mechanical ventilation
Decision to ventilate
Complex
Multifactorial
No simple rules
10/2/2012 Ihab Tarawa 61
Ventilate?
Severity of respiratory failure
10/2/2012 Ihab Tarawa 62
Ventilate?
Severity of respiratory failure
Cardiopulmonary reserve
10/2/2012 Ihab Tarawa 63
Ventilate?
Severity of respiratory failure
Cardiopulmonary reserve
Adequacy of compensation
Ventilatory requirement
10/2/2012 Ihab Tarawa 64
Ventilate?
Severity of respiratory failure
Cardiopulmonary reserve
Adequacy of compensation
Ventilatory requirement
Expected speed of response
Underlying disease
Treatment already given
10/2/2012 Ihab Tarawa 65
Ventilate?
Severity of respiratory failure
Cardiopulmonary reserve
Adequacy of compensation Ventilatory requirement
Expected speed of response Underlying disease
Treatment already given
Risks of mechanical ventilation
10/2/2012 Ihab Tarawa 66
Ventilate?
Severity of respiratory failure
Cardiopulmonary reserve
Adequacy of compensation Ventilatory requirement
Expected speed of response Underlying disease
Treatment already given
Risks of mechanical ventilation
Non-respiratory indication for intubation
10/2/2012 Ihab Tarawa 67
Ventilate?
43 year old male
Community acquired pneumonia
Day 1 of antibiotics
PaO2 8 kPa (60 mmHg), PaCO2 4 kPa (30 mmHg), pH 7.15 on 15 l/min O2 via reservoir facemask
Respiratory rate 35/min
Agitated
10/2/2012 Ihab Tarawa 68
Yes
43 year old male
Community acquired pneumonia
Day 1 of antibiotics
PaO2 8 kPa (60 mmHg), PaCO2 4 kPa (30 mmHg), pH 7.15 on 15 l/min O2 via reservoir facemask
Respiratory rate 35/min
Agitated
10/2/2012 Ihab Tarawa 69
Yes
43 year old male
Community acquired pneumonia
Day 1 of antibiotics
PaO2 8 kPa (60 mmHg), PaCO2 4 kPa (30 mmHg), pH 7.15 on 15 l/min O2 via reservoir facemask
Respiratory rate 35/min
Agitated
10/2/2012 Ihab Tarawa 70
O2
O2
Yes
43 year old male
Community acquired pneumonia
Day 1 of antibiotics
PaO2 8 kPa (60 mmHg), PaCO2 4 kPa (30 mmHg), pH 7.15 on 15 l/min O2 via reservoir facemask
Respiratory rate 35/min
Agitated
10/2/2012 Ihab Tarawa 71
Yes
43 year old male
Community acquired pneumonia
Day 1 of antibiotics
PaO2 8 kPa (60 mmHg), PaCO2 4 kPa (30 mmHg), pH 7.15 on 15 l/min O2 via reservoir facemask
Respiratory rate 35/min
Agitated
10/2/2012 Ihab Tarawa 72
Yes
43 year old male
Community acquired pneumonia
Day 1 of antibiotics
PaO2 8 kPa (60 mmHg), PaCO2 4 kPa (30 mmHg), pH 7.15 on 15 l/min O2 via reservoir facemask
Respiratory rate 35/min
Agitated
10/2/2012 Ihab Tarawa 73
Ventilate?
24 year old woman
Presents to A&E with acute asthma SOB for 2 days
Salbutamol inhaler, no steroids
PFR 60 L/min, HR 105/min
pH 7.25 PaCO2 6.8 kPa (51 mmHg), PaO2 42 kPa (315 mmHg) on FiO2 0.6
RR 35/min
Alert
10/2/2012 Ihab Tarawa 74
No
24 year old woman
Presents to A&E with acute asthma SOB for 2 days
Salbutamol inhaler, no steroids
PFR 60 L/min, HR 105/min
pH 7.25 PaCO2 6.8 kPa (51 mmHg), PaO2 42 kPa (315 mmHg) on FiO2 0.6
RR 35/min
Alert
10/2/2012 Ihab Tarawa 75
No
24 year old woman
Presents to A&E with acute asthma SOB for 2 days
Salbutamol inhaler, no steroids
PFR 60 L/min, HR 105/min
pH 7.25 PaCO2 6.8 kPa (51 mmHg), PaO2 42 kPa (315 mmHg) on FiO2 0.6
RR 35/min
Alert
10/2/2012 Ihab Tarawa 76
No
24 year old woman
Presents to A&E with acute asthma SOB for 2 days
Salbutamol inhaler, no steroids
PFR 60 L/min, HR 105/min
pH 7.25 PaCO2 6.8 kPa (51 mmHg), PaO2 42 kPa (315 mmHg) on FiO2 0.6
RR 35/min
Alert
10/2/2012 Ihab Tarawa 77
No
24 year old woman
Presents to A&E with acute asthma SOB for 2 days
Salbutamol inhaler, no steroids
PFR 60 L/min, HR 105/min
pH 7.25 PaCO2 6.8 kPa (51 mmHg), PaO2 42 kPa (315 mmHg) on FiO2 0.6
RR 35/min
Alert
10/2/2012 Ihab Tarawa 78
No
24 year old woman
Presents to A&E with acute asthma SOB for 2 days
Salbutamol inhaler, no steroids
PFR 60 L/min, HR 105/min
pH 7.25 PaCO2 6.8 kPa (51 mmHg), PaO2 42 kPa (315 mmHg) on FiO2 0.6
RR 35/min
Alert
10/2/2012 Ihab Tarawa 79
No
24 year old woman
Presents to A&E with acute asthma SOB for 2 days
Salbutamol inhaler, no steroids
PFR 60 L/min, HR 105/min
pH 7.25 PaCO2 6.8 kPa (51 mmHg), PaO2 42 kPa (315 mmHg) on FiO2 0.6
RR 35/min
Alert
10/2/2012 Ihab Tarawa 80
Pathway
Airway patent
Secure airway
Patient breathing
Ventilat
Is he hypoxic
10/2/2012 Ihab Tarawa 81
Hypoxic
Yes No
Acidosis
Shock
PE
Asthma
Pumonary edema
Anxiety
10/2/2012 Ihab Tarawa 82
Hypoxic
Pco2
High /normal Low Pco2
pneumonia
ARDS
Pulmonary edema
Aspiration
PE
pneumothorax
10/2/2012 Ihab Tarawa 83
Hypoxic
Pco2
High /normal
Normal A-a gradient
Breathing hard
Asthma
COPD
PE
Breathing normally
CND
Drugs
High A-a gradient
Fatigue from hypoxia
Acute on chronic
Low Pco2
10/2/2012 Ihab Tarawa 84
10/2/2012 Ihab Tarawa 85
10/2/2012 Ihab Tarawa 86
QUESTIONS?