RESPIRATORY FAILURE

RESPIRATORY FAILURE

الدكتور خلدون ذنون- كلية طب نينوى- المرحلة الرابعة

Objectives

The student should be able to understand the following:
1. Definition of respiratory failure and how to read blood gas analysis.
2. The types of respiratory failure, acute and chronic, type 1 and type 11.
3. Main causes of each type.
4. Main line of management of each type.
5. Indications of O2 therapy.
6. Concentration of O2 used.
7. Methods of O2 administration.
8. Home O2 therapy.
9. Types of ventilation and its indications.
10. Use of sedation in respiratory failure and ventilation.

Definition: pulmonary gas exchange fails to maintain normal oxygen and CO2 level.

Type 1 respiratory failure: acute and chronic
PaO2<8kpa (60 mmHg) PaCO2 normal or < 6.6kpa (50 mmHg)
A. Causes of Acute RF1
Acute asthma
pulmonary embolism
pulmonary oedema
ARDS
Pneumothorax
Pneumonia
Lobar collapse


Management
High concentration O2 >40-60% (humidified O2)by oronasal mask,children need O2 tents.
Close monitoring, initial arterial blood gases & repeated within
20 min.to asses response to therapy i.e increase PaO2.
Treatment of underlying disorder.
Mechanical ventilation for severely ill patients e.g multilobar pneumonia & those with no response to medical therapy.


Opiates is indicated in: acute LV failure, massive pulmonary embolism, pleural pain due to pulmonary infarction & pneumonia, never use it in asthma or COPD except with assisted mechanical
ventilation.

B. Chronic RF 1 Causes

Emphysema
Lung fibrosis
Lymphangitis carcinomatosa
Right to Left shunt e.g cardiac defects
Brain stem lesion

Therapy

Treatment of underlying cause.
Controlled long term 02 therapy.


Type 11 respiratory failure: acute and chronic
PaO2 <8kpa PaCO2 >6.6kpa
A.Acute (asphyxia)
Causes
Acute severe asthma
Acute exacerbation of COPD
Acute epiglottits
Inhaled foreign body(FB)
Respiratory muscle paralysis
Flial chest injury
Narcotics
Primary alveolar hypoventilation
Narcotics

Management

Rapid reversal of precipitating event e.g laryngeal FB removal,
tracheostomy, rib fixation in flial chest injury, reversal of narcotic
poisoning, treatment of acute severe asthma.
Controlled low concentration O2.
Non-invasive ventilation
Intubation & mechanical ventilation.


B. Chronic type 11 RF
CO2 retention & acidosis corrected by renal conservation of HCO3`to retain normal PH.
Causes:
COPD
Kyphoscoliosis
Ankylosing spondylitis
Sleep apnea
Myopathies and muscular dystrophy

Acute on chronic type 11 RF

Pulmonary insult e.g acute exacerbation of COPD, precipitate
episode of acute on chronic type 11 RF, which lead to further
increase in PaCO2 & acidosis resulting in drowsiness &coma.
Patient may look little distressed despite severe hypoxia &
hypercapnea.

Causes

Retention of secretion
Infection
Bronchospasm
pulmonary embolism
Heart failure
Chest trauma
Pneumothorax
CNS depression e.g narcotics


Management
Patient evaluation e.g conscious level, cough reflex, sign of CO2
retention, airway obstruction, RV failure, functional status.
Blood gases & chest X-ray.
Asses precipitating factors & decision on mechanical ventilation.
Maintenance of patent airway.
Frequent physiotherapy and pharyngeal suction.
Nebulized bronchodilator.
Chest tube for pneumothorax, local anesthesia for chest trauma.
Controlled O2 24-28% , use Venturi mask. It is not necessary to achieve normal O2 value, even small increase is greatly beneficial.
Achieve safe PaO2 >7kpa without increasing PaCO2.
If controlled O2 therapy causes increase PaCO2 & decreased PH resort to invasive or non-invasive ventilation.
Doxapram: given i.v if ventilatory support is not available or not tolerated &in respiratory depression due to sedatives &anesthesia. It is of limited benefit.
Antibiotics for infection.
Diuretics for heart failure.

OXYGEN THERAPY

Leads to increase in Fi02 (inspired 02 concentration).
Overcomes reduced Pa02 in the blood.
O2 dissolved in plasma, and thus increase quantity of 02 carried in plasma even when HB is fully saturated.


Adverse effects
1. 100% O2 is irritant & toxic if given for more than few hours.
2. Retrolental fibroplasias & blindness in premature infants.
3. Pulmonary toxicity(pul.edema) in adults if high conc.>24 hour.

Administration of 02

1. High conc. for short period e.g 60% high- flow mask, humidified, useful
in acute type 1 RF e.g pneumonia, asthma.
2. Low conc. O2 24-28% controlled-flow mask, used in type 11 RF.
1-2 liter/min. nasal double canulae, allow patient to eat & undergo
physiotherapy, no need for humidification.
3. Used at hospitals, ambulance, and at home.

Home ventilation for chronic respiratory failure

It is indicated if PaO2 <7.3kpa & FEV1 <1.5L.
Via cylinders, O2 concentrator, low-concentration mask or nasal canulae.
Non-invasive ventilation NIV can be used at home, given overnight is
often sufficient to restore daytime PCO2 to normal that relieves
fatigue and headache.
Daytime NIV can be used in advanced muscle disease.


Types of ventilation
Mechanical ventilation (invasive ventilation): indicated to treat respiratory failure that fails to respond to optimal medical therapy and in comatosed patient with respiratory failure. Done through tracheostomy or endotracheal tube.
Example: Intermittent positive pressure ventilation (IPPV): Full
sedation is needed.

Non-invasive ventilation

It is a form of ventilator support in which positive pressure is
delivered via the patients upper airway using face or nasal mask or
similar device. Avoiding tracheostomy, endotracheal intubation, and
sedation.
Example: Nasal positive pressure ventilation (NPPV), Continuous positive airway pressure (CPAP), Bi-level positive airway pressure (BiPAP)
Indications:
Chronic respiratory failure due to: COPD, Kyphoscoliosis, neuromuscular disease, and Central alveolar hypoventilation, sleep apnea.
Acute on chronic respiratory failure e.g acute excacerbation of COPD.
Weaning from mechanical ventilation.










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