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Respiratory failure causes, types, diagnosis and treatment

This article is to discuss Respiratory failure regarding its Definition,Types , causes, clinical picture and methods of treatment.

Definition of Respiratory failure

It is a decline in the respiratory performance leading to hypoxia ± hypercapnea with the following arterial blood gases :
Respiratory failure causes

Provided with normal atmospheric O2 tension and absence of A- V shunts.
So respiratory failure is mainly a laboratory diagnosis.

Types of respiratory failure

Type I : Hypoxic normocapnic or hypocapnic as CO2 may be washed due to hyperventilation, it is mainly diffusion defect.
Causes
Respiratory failureAcute
- Acute pulmonary edema - ARDS
- Pneumonia
- Pulmonary embolism.

Chronic
- Pure emphysema
- Interstitial Pulmonary fibrosis-Lymphangitis carcinomatosa.

Type II: Hypoxic hypercapnic

It is mainly due to ventilation defect so :  Low O2 and  High CO2
Causes:
Acute
• Respiratory muscle paralysis (see neurological causes of hypoventilation)

Acute severe asthma.
Chronic
• Obstructive hypoventilation. e.g. COPO
• Restrictive hypoventilation e.g. pulmonary fibrosis and kyphoscoliosis.

Patient with chronic bronchitis + emphysema will suffer from ventilation +diffusion defect + perfusion defect --> Hypoxia and Hypercapnia (type II respiratory failure).

Clinical Picture

(1) Features of hypoxia.
• Acute     :  Central cyanosis, tachypnea, tachycardia, convulsions and impaired consciousness.
• Chronic  :  Central cyanosis, clubbing, P++, cor pulmonale, polycythaemia,fatigue and drowziness.

(2) Features of hypercapnea.
Acute      :   Confusion then coma,
Chronic   :  Headache, drowsiness, hypersomnia (C02 narcosis), flabbing tremors, +++ ICT with papilloedema.

(3) Features of the cause.

Treatment of respiratory failure:

1- Treatment of the cause and precipitating factor e.g antibiotics, bronchodilators, steroids.

2- O2 therapy according to the type :

Type I 
There is Hypoxia with No Hypercapnia i.e CO2 retention is not a risk.
• So we can give O2 with high concentration
• Treatment of the cause
• Mechanical ventilation If necessary in acute cases and controlled long term O2 therapy in chronic cases.

Type II
There is Hypoxia + Hypercapnia , So ++  C02 --> decreases sensitivity of respiratory center to Co2, So
hypoxia --> stimulate peripheral chemoreceptors --> stimulation of breathing (Hypoxic drive) so correction of hypoxia
leads to depression of respiratory center .

• So in ttt of type II give low flow O2 to preserve the hypoxic drive.
• Mechanical ventilation if necessary in acute or chronic cases.
• Also we can use doxapram as a respiratory stimulant.
• Controlled long term O2 therapy in chronic cases.
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Tamer Mobarak

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