Acute respiratory failure is defined by the sudden onset of severe impairment of pulmonary gas exchange Characterized by the inability of the lungs to meet the body’s metabolic needs for the transport of oxygen (O2) into the blood and/or removal of carbon dioxide (CO2) from the blood. Respiratory failure results from inadequate gas exchange by the respiratory system - Meaning that the arterial oxygen, carbon dioxide or both cannot be kept at normal levels.

1. Respiratory Failure
(Insufficiency)
W. P. Rivindu H. Wickramanayake
Group no. 04a
5th Year 2nd Semester – 2019 November
Tbilisi State Medical University, Georgia

2. ● Acute respiratory failure is defined by the sudden
onset of severe impairment of pulmonary gas
exchange
● Characterized by the inability of the lungs to meet
the body’s metabolic needs for the transport of
oxygen (O2) into the blood and/or removal of
carbon dioxide (CO2) from the blood.
● Respiratory failure results from inadequate gas
exchange by the respiratory system
- Meaning that the arterial oxygen, carbon dioxide or
both cannot be kept at normal levels.
● A drop in the O2 carried in blood - Hypoxemia.
● A rise in arterial CO2 levels - Hypercapnia.

3. Components of the
Respiratory System
● Central nervous system
● Diaphragm and other respiratory muscles
● Upper and lower respiratory tract, Lungs
● Gas exchange in the alveoli
● Cardiac output
● Concentration of hemoglobin
● Impairment of each component can cause
respiratory failure

4. Respiratory Control
● Established by the coordination of three groups of
neurons in the medulla oblongata:
1. Dorsal respiratory center - controls inspiration,
2. Ventral respiratory group - controls expiration,
3. Pneumotaxic center - controls rate & depth of breathing.
● In addition to neurons in the brainstem, a peripheral
chemoreceptor system is located outside the brain in the
form of: A) Carotid bodies
B) Aortic bodies
- They detect subtle changes in PaO2.

5. Gas Exchange
● Neural impulses from CNS traverse the spinal cord &
motor neurons, reaching & activating the diaphragm and
other respiratory muscles.
● Contraction of the respiratory muscles creates negative
pleural pressure by expanding the chest cavity and
pushing the abdominal contents down.
● The negative pressure created in the thorax during
inspiration leads to sub-atmospheric pressure in the
alveoli, creating a gradient for the flow of inspired air
toward the alveoli.
● Oxygen-rich inspired air allows the diffusion of O2 from
the alveoli to the blood through the alveolar capillary
membrane, where deoxygenated hemoglobin becomes
saturated with O2 and forms Oxyhemoglobin.

6. Oxygen Consumption(QO2)
● O2 is consumed by all human tissues
● (QO2) is dependent on gas exchange in the lungs.
● The average O2 uptake of an adult is approx. 250 mL/min
Oxygen Transport
● Most (~98.5%) O2 is carried to peripheral tissues via oxyhemoglobin
● The remainder is transported as O2 dissolved in the fluid phase of blood.
● The total transport of O2 by the arterial system is termed oxygen delivery
(DO2) and is normally severalfold higher than the O2 demand of the
peripheral tissues.
Oxygen Distribution
● DO2 is dependent on cardiac output and arterial oxygen content
● (CaO2), a value determined by the concentration of hemoglobin (Hgb)
● And oxygen saturation (SaO2) The adequate perfusion of capillaries in the
peripheral tissues allows for the liberation of O2 from oxyhemoglobin.

7. Classically described as one of Two types:
● Type 1 classic hypoxemic RF
- Low level of O2 in blood(hypoxemia)
- PaO2 < 60mmHg
- with either a normal or low level of CO2(PaCO2)
- Caused by ventilation/perfusion(V/Q) mismatch
● Type 2 Hypoxemia (PaO2 <8kPa) with hypercapnia
(PaCO2 >6.0kPa)
- RF is caused by inadequate alveolar ventilation;
both oxygen and carbon dioxide are affected

8. Primary abnormality could be:
1) Inadequately oxygenated alveoli
- Due to low FiO2 and/or alveolar collapse and/or
the presence of alveoli filled with fluid, cells, debris,
or blood)
2) Compromised transition of oxygen from the alveoli
to the blood
- Due to interstitial processes or pulmonary
vascular disease
3) Compromised ability of the blood to become
oxygenated
- Due to obstructed blood flow, shunting, low Hgb
concentration, or the presence of dysfunctional Hgb).

9. Type II or “Hypercapnic” RF
● Type II ARF (PaCO2 > 45 mm Hg) represents the
failure of the lungs to remove a sufficient amount of
CO2
● Characterized by decreased alveolar minute
ventilation.
● An increase in PaCO2 leads to hypoxemia because CO2
displaces O2 and effectively reduces the alveolar partial
pressure of oxygen (PAO2)
● Hypoxemia in type II ARF is easily corrected with
supplemental oxygen.
● Frequently due to acute or chronic neuromuscular
dysfunction or the inability of the airways or lungs to
ensure adequate ventilation and CO2 exchange.

10. Type III or “Perioperative” RF
● Type III RF is synonymous with perioperative RF and is related
to atelectasis of the lung.
● Often a consequence of abnormal abdominal and chest wall
mechanics in the setting of surgery or trauma, especially with
intrapleural or subdiaphragmatic pathologies.
● The patient usually splints the chest to limit involuntary
movement of the injured region.
Type IV or “High-demand” RF
● Related to an inability (normal or relatively normal lungs) to
keep up with increased ventilatory demands associated with
systemic hyper metabolism (e.g., secondary to sepsis).
● Respiratory muscle fatigue can lead to a requirement for
mechanical ventilation (MV) to support adequate minute
ventilation.

11. ● Pneumonia infection
● Pancreatitis (inflammation of the pancreas)
● Severe trauma
● Sepsis
● Severe brain injuries
● Lung injuries caused by inhalation of smoke or
chemical products
● Drug or alcohol abuse
● Chemical inhalation- toxic chemicals, smoke, fumes
Underlying health problem such as:

12. Diagnosis
● Obtaining a history
● Detailed examination of the upper airway and chest,
neurologic, cardiovascular, abdominal, skin, and
musculoskeletal system
- to narrow the differential diagnosis.
● Chest X-Ray, CT
● Echocardiography in patients with systemic disease and
shock to evaluate cardiac function
● Rapid Ultrasound for Shock and Hypotension
● Laryngoscopy or bronchoscopy
● Arterial Blood Gas(ABG) test
- to determine the chronicity and severity of the RF
● CBC, Basic metabolic profile, Cardiac enzymes,
● Microbiological evaluation

13. Management
● Usually requires admission to the ICU, for adequate support and
monitoring
● Stabilization of the patient’s ventilatory and hemodynamic status
● Correction of the pathophysiologic process underlying the respiratory
failure.
● ABC” approach- airway, breathing, and circulation, is a basic tenet in
the management of ARF.
● Antibiotics and source control for the management of infections
● Cardiac or inotropic medications,
● Revascularization,
● Air or fluid evacuation
● Anticoagulation or Thrombolysis medications and interventions
required to treat the underlying etiology of ARF.
● Prior to the comprehensive diagnostic work-up, it is important to
remember that a diagnostic procedure should not be a reason for
delayed intervention in cases of severe ARF.

14. The Success of the Management
● Multiple ABGs - to ensure both oxygenation and
ventilation are maintained within desired limits.
● General recommended goal of PaO2 >88%.
● pH and PaCO2 values reflect the adequacy of MV
● Purpose of Mechanical ventilation
- To improve oxygenation and ventilation while
correcting respiratory acidosis and hypoxemia
- Meeting metabolic demands
- Resting respiratory muscles
- Optimizing cardiac function and blood
circulation.

15. General Indications for Intubation
& Mechanical Ventilation
● Cardio-respiratory arrest or impending arrest
● Respiratory distress/tachypnea with increased
ventilatory demand and breathing
● Effort leading to respiratory muscle fatigue
● Severe hypercapnic respiratory failure
● Intermittent positive pressure ventilation (NIPPV)
or failure of NIPPV
● Severe refractory hypoxemia with failure of
noninvasive oxygen delivery devices
● Severe refractory metabolic acid-base disorder

16. ● Inability to protect the airway
● Inability to clear secretions
● Need for therapeutic hyperventilation or
hypoventilation
● Upper airway obstruction with poor airway
patency
● Decreased respiratory drive with bradypnea
● Coma with Glasgow Coma Scale score of <8
● Severe trauma
● Surgery requiring general anesthesia

17. Conclusion
● ARF is one of the most common conditions
encountered in the ICU and is associated with
significant morbidity and mortality
● Clinical presentation (acute or acute on chronic)
is essential for the management of these patients
● The management of ARF is to focus on the
“ABC” approach
● Finally, therapies need to be directed at both the
ARF itself as well as the underlying condition in
order to optimize patient outcomes.