10. Respiratory insufficiency
The condition in which the lungs can not take in
sufficient oxygen or expel sufficient carbon
dioxide to meet the needs of the cells of the
body..
11. Respiratory failure
Respiratory failure is a syndrome in which the respiratory
system fails in one or both of its gas exchange functions:
oxygenation and carbon dioxide elimination.
12. In practice :
respiratory failure defiend as Pao2 value less
than 60 mm Hg or PaCO2 value more than
50 mm Hg.
13. classification
(1)according to PaCO2
■ hypoxemic (Group Ⅰ) respiratory failure
PaO2 of less than 60 mm Hg with a normal or low PaCO2.
Cause of: Edema, Vascular disease, Chest Wall.
■ hypercapnic (Group Ⅱ ) respiratory failure
PaO2 low 60 mm Hg and PaCO2 of more than 50 mm Hg.
Cause of: Airway obstruction, Neuromuscular disease.
14. (2)according to pathogenic mechanism
■ ventilatory disorders
1-obstructive ventilatory disorders
asthma, emphysema, chronic bronchitis, and bronchiectasis
2-restrictive ventilatory disorders
deformity of thorax , fracture of several ribs, tension pneumothorax
diffuse interstitial fibrosis
■ gas exchange disorders
1-diffusion disorders
2-ventilation-perfusion mismatching
15. (3)according to primary site
■ central respiratory failure
■ peripheral respiratory failure
airway obstruction between the glottis and the carina
■Obstruction is located in the
airway outside the thorax:
inspiratory dysnea
■Obstruction is located in the
airway inside the thorax:
expiratory dysnea
expire inspire
16. ■ peripheral respiratory failure
Peripheral airway obstruction may be caused by: specific
chemical mediators (such as histamine, leukotrienes,
prostaglandins ), other substances released during inflammatory
and allergic responses
(4)according to duration
■ acute respiratory failure minute to hours
■ chronic respiratory failure several dayes or longer
19. HYPOXIC RESPIRATORY FAILURE (TYPE 1)
Most common form of respiratory failure
Lung disease is severe to interfere with pulmonary O2
exchange, but over all ventilation is maintained
21. V/Q mismatch
Normal ventilation of alveoli is
comparable to amount of
perfusion
Normal V/Q ratio is 0.8 (more
perfusion than ventilation)
V/Q Mismatch :
Inadequate ventilation
Poor perfusion
VA Q VA/ Q
Top 1.2L/min 0.4L/min 3.0
Middle 1.8L/min 2.0L/min 0.9
Bottom 2.1L/min 3.4L/min 0.6
23. Shunt An extreme V/Q mismatch
((Perfusion without ventilation))
Shunting is the most common cause for hypoxaemic respiratory failure
in ICU patients.
The deoxygenated blood bypasses the ventilated alveoli and mixes with
oxygenated blood → hypoxemia
Persistent of hypoxemia despite 100% O2 inhalation
Hypercapnia occur when shunt is excessive > 60%
24. Causes
I- Anatomic shunt
Blood passes through parts of respiratory system that
receives no ventilation
II- Intracardiac
Right to left shunt
Fallot’s tetralogy
Eisenmenger’s syndrome
III- IntraPulmonary
A/V malformation
Pneumonia
Pulmonary edema
Atelectasis/collapse
Pulmonary Hge
Pulmonary contusion
25. Diffusion limitation
Distance between alveoli and pulmonary capillary is
one- two cells thick
With diffusion abnormalities:
there is an increased distance
between alveoli and pulmonary capillary.
causes
A.R.D.S
Sever emphysema
Recurrent pulmonary emboli
Pulmonary fibrosis
26. Alveolar hypoventilation
Is a generalized decrease in ventilation of lungs
and resultant buildup of CO2
Causes
Restrictive lung disease
CNS disease
Chest wall dysfunction
Neuromuscular disease
27. Hypercapnic Respiratory Failure (Type II)
This occurs in patients with chronic CO2 retention who worsen and have
rising CO2 and low pH.
Mechanism: respiratory muscle fatigue
30. Effects of respiratory failure
1- Acid-base disturbances & disorders of electrolyte balance
2- Alteration of the respiratory system
peripheral chemoreceptor
■ PaO2↓ <60mmHg respiratory center(+) respiratory movement↑
<30mmHg respiratory center (-) respiratory movement ↓
■ PaCO2↑ central chemoreceptor
<80mmHg respiratory center (+) respiratory movement↑
>80mmHg respiratory center (-) respiratory movement ↓
31. 3. Alteration of the cardiovascular system
■ compensatory reaction
PaO2<60 mmHg,PaCO2 increase cardiovascular center(+)
increase in cardiac output : increase in stroke volume and heart rate
redistribution of blood flow
■ injurious changes
PaO2< 40 mmHg,PaCO2> 80 mmHg cardiovascular center(-)
rate slow, decreased blood pressure
cardiac output decrease
pulmonary hypertension
32. 4. Alteration of the nervous system
(1) Hypoxia: the nervous system is very sensible to oxygen lack.
< 40~50 mmHg, serious but reversible deterioration in cerebral function
( orientation, arithmetic tasks, memory) occurs, and restlessness and
confusion are common.
< 30 mmHg, loss of consciousness results.
< 20 mmHg, irreversible damage of neural cells.
(2) Hypercapnia: CO2 nacosis.
condition of confusion, tremors, convulsions, and possible coma that
may occur if blood levels of carbon dioxide increase to 80mm Hg or higher
33. 5. Alteration of the renal function
6. Alteration of the digestive system
36. Clinical diagnosis
Respiratory compensation
Tachypnoea RR > 35 Breath /min
Accessory muscl
Retraction intercostal ms
Nasal flaring
Sympathetic stimulation
HR
BP Tissue hypoxia
sweating
Altered mental state
Haemoglobin desaturation HR and BP (late)
Low spo2
Cyanosis (late)
37. Causes of error Pulse oximetry
Poor peripheral perfusion
Dark skin
False nails or nail PAINTING
Bright ambient light
Poorly adherent probe
Excessive motion
Carboxyhaemoglobin or
methaemoglobin
38. ASSESSMENT OF PATIENT
1-Careful history
2-Physical Examination
3-Investigations
I- ABG analysis :
PaO2
PaCO2
pH
Alveolar-Arterial PO2 Gradient
P(A-a)02 = (PiO2 - PaCO2) – PaO2
R
39. where PiO2 = partial pressure of inspired air, R = 0.8
i.e, at sea level, breathing air;
PAO2 = 20 - PaCO2/0.8
A-a Gradient = 20 - PaCO2/0.8 -PaO2
Normal P(A-a)O2 gradient: 5-10 mm of Hg
A sensitive indicator of disturbance of gas exchange.
Useful in differentiating extrapulmonary and pulmonary causes of
resp. failure.
41. Management of Respiratory Failure Principles
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
42. Management
Correction of hypoxemia
Supplemental O2 therapy essential
Titration based on SaO2, PaO2 levels and PaCO2
Goal is to prevent tissue hypoxia
Tissue hypoxia occurs (normal Hb & C.O.)
- venous PaO2 < 20 mmHg or SaO2 < 40%
- arterial PaO2 < 38 mmHg or SaO2 < 70%
Increase arterial PaO2 > 60 mmHg(SaO2 > 90%) or venous SaO2 > 60%
Correction of hypercapnia
Control the underlying cause
Controlled O2 supply
1 -3 lit/min, titrate according O2 saturation
O2 supply to keep the O2 saturation >90% but
<93 to avoid inducing hypercapnia
45. Drug Therapy
Relief of bronchospasm
Bronchodilators
Reduction of airway inflammation
Corticosteroids
Reduction of pulmonary congestion
IV diuretics
Treatment of pulmonary infections
IV antibiotics
Nutritional Therapy
Maintain protein and energy stores
Enteral or parenteral nutrition Supplements
46. Noninvasive Ventilatory support (IPPV)
BiPAP CPAP
Mild to moderate RF
NIPPV INDICATED In
Acute exacerbation of COPD WITH
Respiratory acidosis pH 7.25 Or less
Cardiogenic pulmonary edema
Asthma
Type II R.F secondary to chest wall deformity
or neuro muscular diseases
Weaning off mechanical ventilation
47. Benefits NIPPV
of
Improved alveolar ventilation
Reduced work of breathing
Rest of the respiratory musculature
Increased intrathoracic pressure
decreases preload and
afterload
48. should not be considered for NPPV?
Contraindications
Cardiac or respiratory arrest
Nonrespiratory organ failure
Hemodynamic instability
Severe encephalopathy
Severe UGI bleed
Facial or neurosurgery, trauma
Upper airway obstruction
Inability to cooperate or protect airway
High risk for aspiration
49. Mechanical ventilation
Indications
PaO2< 55 mm Hg or PaCO2 > 60 mm Hg
despite 100% oxygen therapy.
Deteriorating respiratory status despite
oxygen and Nebulization therapy
Anxious, with deteriorating mental status.
Respiratory fatigue: for relief of metabolic
stress of the work of breathing
50. Mechanical Ventilation: Strategies
1-SIMV, A/C with PEEP
PEEP (positive End-Expiratory pressure)
Increase intrathoracic pressure
Keeps the alveoli open
Decrease shunting
Improve gas exchange
51. 2-High frequency ventilation (HFV)
Very small tidal volumes are used
(<1ml/kg), very rapid rates and lower mean
airway pressures are used
3-Lung Recruitment
To open the collapsed alveoli
A sustained inflation of the lungs to higher
airway pressure and volumes
4-Permissive Hypercapnia
Allows the PaCO2 to rise into the 60-70 mm of
Hg range, as long as the patient is adequately
oxygenated (SaO2> 92%), and able to tolerate
the acidosis.
This strategy is used to limit the amount of
barotrauma and volutrauma to the patient
52. 5-Prone positioning
Improve oxygenation in about 2/3 of all
treated patients
No improvement on survival, time on
ventilation, or time in ICU
Might be useful to treat refractory
hypoxemia
Routine use is not recommended
53. Respiratory failure common in old age due to
↓ Ventilatory capacity
Alveolar dilation
Larger air spaces
Loss of surface area
Diminished elastic recoil
Decreased respiratory muscle strength
↓ Chest wall compliance