Download RESPIRATORY FAILURE I

DR. M. A. Sofi MD; FRCP; FRCPEdin; FRCSEdin
Al Maarefa College of Science & Technology
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Definition
Respiration is gas exchange between the
organism and its environment. Function of
respiratory system is to transfer O2 from
atmosphere to blood and remove CO2 from blood.

Clinically
Respiratory failure is defined as PaO2 <60 mmHg
while breathing air, or a PaCO2 >50 mmHg.
 Results
from inadequate gas exchange
◦ Insufficient O2 transferred to the blood
 Hypoxemia
◦ Inadequate CO2 removal
 Hypercapnia
Causes of respiratory failure
Nervous system failure
(Type II)
 Central hypoventilation
 Neuropathies
 GBS
 ALS
II. Muscle (pump) failure
(Type II)
 Muscular Dystrophies
 Myopathies
I.
NMJ transmission
failure (Type II)
III. Myasthenia Gravis
III.
Airway failure (Type II)
 Obstruction
 Dysfunction
IV.
Causes of respiratory failure
Chest wall or pleural
space failure (Type II)
V.
VII.
Pulmonary unit failure
(Type I)
 Kyphoscoliosis
 Collapse
 Morbid obesity
 Flooding:
 Pneumothorax
 Edema
 Hydrothorax
 Blood
 Pus
 Hemothorax
Pulmonary vasculature
failure (Type I)
 Pulmonary embolism
 Pulmonary Hypertension
 Aspiration
 Fibrosis
VI.
Airway failure (Type II)
 Obstruction
 Dysfunction
VIII.
Respiratory failure is Classifieds into type I or type II relates
to the absence or presence of hypercapnia respectively.
Type 1 respiratory failure is defined as hypoxemia
without hypercapnia, and indeed the PaCO2 may be normal or low. It
is typically caused by a ventilation/perfusion (V/Q) mismatch; the
volume of air flowing in and out of the lungs is not matched with the
flow of blood to the lungs. The basic defect in Type 1 respiratory
failure is failure of oxygenation characterized by:
PaCO2
decreased (< 60 mmHg
(8.0 kPa))
normal or decreased
(<50 mmHg (6.7 kPa))
PA-aO2
increased
PaO2
Type I Failure
1.
2.
3.
Low ambient oxygen: (high
altitude).
Ventilation-perfusion
mismatch: pulmonary
embolism.
Alveolar hypoventilation
(decreased minute volume
due to reduced respiratory
muscle activity, e.g. in acute
neuromuscular disease
(this form can also cause type
2 respiratory failure if
severe).
Diffusion problem (oxygen
cannot enter the capillaries
due to parenchymal disease,
e.g.
4.
•
•
Pneumonia
ARDS
Shunt (oxygenated blood mixes
with non-oxygenated blood
from the venous system,
e.g.
•
(right-to-left shunt).
Type 2
Hypoxemia (PaO2 <8kPa) with hypercapnia (PaCO2 >6.0kPa).
The basic defect in type 2 respiratory failure is characterized by:
PaO2
PaCO2
PA-aO2
pH
decreased (< 60 mmHg
(8.0 kPa))
increased (> 50 mmHg
(6.7 kPa))
normal
decreased
Type 2 respiratory failure is caused by:
• Inadequate alveolar ventilation; both oxygen and carbon
dioxide are affected.
• Defined as the build up of carbon dioxide levels (PaCO2) that
has been generated by the body but cannot be eliminated.
Type 2 respiratory failure is caused by:
A. Increased airways resistance (chronic obstructive pulmonary
disease, asthma, suffocation).
B. Reduced breathing effort (drug effects, brain stem lesion,
extreme obesity).
C. A decrease in the area of the lung available for gas exchange
(such as in chronic bronchitis).
D. Neuromuscular problems (Guillain-Barré syndrome, myasthenia
gravis, motor neurone disease).
E. Deformed (kyphoscoliosis), rigid (ankylosing spondylitis), or flail
chest.
Type I Respiratory failure
 Pneumonia
 Cardiogenic pulmonary edema
 Pulmonary edema due to
inceased hydrostatic
pressure.
 Non-cardiogenic pulmonary
edema
 Pulmonary edema due to
increased permeability
 Acute lung injury
 Acute respiratory distress
syndrome
Type I Respiratory failure
 Pulmonary embolism (See
also type IV respiratory
failure)

Atelectasis (See also type III
respiratory failure)

Pulmonary fibrosis
Type II Respiratory Failure
Type II Respiratory Failure
 Central hypoventilation
 Neuromuscular
Asthma
 Chronic Obstructive
Pulmonary Disease

 Hypoxemia and
hypercapnia
often occur together
& chest
wall disorders Causes:
Myopathies
Neuropathies
Myasthenia gravis
Kyphoscoliosis
 Obesity
Hypoventilation
Syndrome
Etiology and Pathophysiology: causes
Type III Respiratory
failure:
Inadequate post-operative
analgesia, upper
abdominal incision
 Obesity, Ascitis
 Pre-operative tobacco
smoking
 Excessive airway secretion

Type IV Respiratory
failure:
 Cardiogenic
shock
 Septic shock
 Hypovolemic shock
ACUTE RESPIRATORY FAILURE
Adult Respiratory Distress
Syndrome
Pulmonary Edema
Diagnostic Considerations



Respiratory failure is a common and a
life-threatening condition that
demands prompt diagnosis and
assessment and appropriate
management.
Failure to visualize an obvious
abnormality on chest radiographs in
hypoxemic respiratory failure
suggests the possibility of right-to-left
shunting.
The vast majority of patients in acute
respiratory failure due to cardiogenic
pulmonary edema respond to
measures to reduce preload and
afterload.

Those with acute respiratory distress
syndrome (ARDS) require early elective
intubation because the duration of
respiratory failure is longer.

Hypercapnic respiratory failure occurs
secondary to a variety of causes:

Increased respiratory muscle load.

Impaired neuromuscular function.

Decreased respiratory drive caused
by central nervous system (CNS)
depression.
Differential Diagnoses
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Acute Respiratory Distress Syndrome
Sleep Apnea
Asthma
Atelectasis
Cardiogenic Shock
Cardiomyopathy, Dilated
Cardiomyopathy, Hypertrophic
Cor Pulmonale
Diaphragmatic Paralysis
Emphysema
Myocardial Infarction
Pneumonia, Aspiration/Bacterial/Viral
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Pneumothorax
Pulmonary Edema
Cardiogenic Shock
Pulmonary Edema, Neurogenic
Pulmonary Embolism
Pulmonary Fibrosis, Idiopathic
Pulmonary Fibrosis, Interstitial
Primary Pulmonary Hypertension
Secondary Pulmonary Hypertension
Respiratory Acidosis
Restrictive Lung Disease
Shock, Distributive
Ventilation, Mechanical
Ventilation, Noninvasive
Hypoxemia may cause death in RF
 Primary objective is to reverse and prevent
hypoxemia
 Secondary objective is to control PaCO2 and
respiratory acidosis
 Treatment of underlying disease
 Patient’s CNS and CVS must be monitored and
treated
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