Respiratory failure

1) Department of Internal Medicine, Athena Villa dei Pini Clinic, Piedimonte Matese (CE);

2) Division of Internal Medicine, A.G.P. Piedimonte Matese (CE)

Breathing: How it happens

Breathing is the result of a chain of events that originates from the rhythmic activity of the respiratory centers located at the level of the fourth ventricle, in response to information from central and peripheral chemoreceptors;

the whole of these efferent signals generated at central level (brainstem), is transmitted to the respiratory muscles through the pyramidal ways, determining the movement of the thoracic cage, consequently of the lungs.
The purpose of respiration is to provide an adequate supply of oxygen to the tissues, while at the same time ensuring an "effective elimination of carbon dioxide deriving from the energy production processes that take place at the cellular level, through the combustion of energy substrates (carbohydrates, fats. and proteins) in the presence of oxygen.
The respiratory and cardiovascular systems both contribute to achieving this goal. The respiratory system guarantees the gaseous exchanges between the ambient air and the blood through a gas exchanger (the lung, the airways and the pulmonary vessels), and allows an adequate exchange of air through a mechanical or ventilatory pump (respiratory centers, respiratory muscles, chest wall).

What is Respiratory Failure?

Respiratory insufficiency can result from the compromise of one or both of these elements; therefore it represents that pathological condition in which the respiratory system is no longer able to carry out the function of transporting oxygen, in adequate quantities in the arterial blood, and removal of a corresponding amount of carbon dioxide from the venous blood.

Considering the final result at the cellular level, specifically at the mitochondrial level, respiratory failure can be defined as a disturbance of cellular metabolism secondary to reduced oxygen supply to the tissues, due to the alteration of one or more stages of the respiratory process: ventilation, gas exchange intrapulmonary, gas transport, tissue gas exchanges.
From the pathophysiological point of view, the IR (acronym for respiratory insufficiency) can be divided into:

• Respiratory insufficiency (type 1), mainly characterized by hypoxemia (PaO2 <55-60 mmHg in ambient air) secondary to alteration of the Ventilation / Perfusion ratio, alveolar-capillary diffusion or the formation of shunts.
• Respiratory insufficiency (type 2), predominantly hypoxemic / hypercapnic (PaCO2> 45 mmHg), secondary to CNS, thoracic cage or respiratory muscle pathologies, resulting in alveolar hypoventilation.

Symptoms

For further information: Symptoms Respiratory failure

The main physical signs of ventilatory fatigue are vigorous use of accessory ventilator muscles, tachypnea, tachycardia, decreased respiratory volume, irregular or gasping breathing, and paradoxical movement of the abdomen. Some alteration of the state of consciousness is typical, and confusion is common.

Chronic respiratory failure (CRI) determines a progressively worsening state of disability, which limits the subjects' working capacity and, in the long term, the development of a normal relationship life. The socio-economic implications of this chronic suffering are enormous - both in terms of social security costs (loss of working days, early retirement, etc.), and in terms of pharmaceutical healthcare costs or hospitalization (continuous use of drugs, recurrent hospitalizations with prolonged hospitalization) - and are accompanied by a progressive deterioration in the quality of life of the sick.

Respiratory failure:

• PaO2 <60 mmHg and / or
• PaCO2> 45 mmHg

Respiratory insufficiency

Without hypercapnia

With hypercapnia

Type I.

• Wet lung (EPA, ARDS / ALI)
• Pneumonia
• Acute asthma
• BPCO
• Pulmonary embolism

Type II

• BPCO
• Severe asthma
• Chest deformities
• Neuromuscular disorders
• Drug abuse
• Type I + ventilatory pump deficit

Intrapulmonary Shunt Mismatch V / Q

Alveolar hypoventilation

1. Administer oxygen to correct hypoxia: SpO2 target> 90%, using mask with Venturi system or masks with reservoir;
2. Evaluate possible use of CPAP, especially if the patient remains hypoxic or if he is forced to administer FiO2> 50%;
3. Maintain adequate cardiac output and ensure the transport of oxygen to the tissues;
4. Treatment of the underlying disease;
5. Prevention of preventable complications

1. Administer oxygen to correct hypoxia, using a mask with Venturi system, with lower FiO2, SpO2 target> 88%. Remember that oxygen is a drug (always indicate the type and liters of oxygen);
2. Evaluate the possible use of NIV to correct both acidosis and / or hypercapnia and any resistant hypoxia by applying PEEP;
3. Maintain adequate cardiac output and ensure the transport of oxygen to the tissues;
4. Treatment of the underlying disease.

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