Summary :

Technological and cultural advances, and improvement in care which have taken place over the last 5 years have enabled practitioners to review the possible applications of mechanical breathing assistance, broadening its indications for use, improving its applicability and shortening time of application. The aim of artificial ventilation is not only to support deficient vital function and maintain an adequate gas exchange but essentially to resolve the lung pathology, indirectly aid the resolution of collateral pathologies and stall its progression before a need for highly invasive treatment arises or it evolves towards difficult to treat forms (ARDS). The prevalence and severity of childhood asthma have increased substantially in recent years. Despite continued research and the development of new pharmacological agents, it is one of the leading causes for emergency care requirements; one of the leading causes for missed school, and a cause for considerable morbidity, disability, and occasional mortality at all ages.

Applying mechanical ventilatory support, the advantages of which are both generally recognized and accepted, the undesirable side-effects and damage which may ensue must be borne in mind (barotrauma, volutrauma, atelectrauma, biotrauma) and whatever possible must be done to prevent their appearance. It is no longer possible to speak of unspecified respiratory support being given to a patient presenting respiratory failure; the support provided must take into account the patient's age (e.g. bronchiolitis is characteristic of infants and small children), the severity of the pathology, the patients basic clinical condition (e.g. neuromuscular pathology) and the degree of severity of the pathology when ventilatory support is begun (e.g. precocious or delayed approach).

Mechanical ventilation using positive pressure can need airway invasion using an endotracheal tube or, as is being more frequently seen, non-invasion of airways can be performed (use of facial and nasal masks). Spontaneous breathing can be supported (CPAP, Pressure or Volume Support Ventilation) or ventilation can be totally or partially controlled (Volume and Pressure Controlled Ventilation, Synchronized Intermittent Mandatory Ventilation). Each model has precise indications which allow better application on the one hand, while on the other avoid side effects.

Introduction:

By respiratory failure we mean inability of patient to effect adequate gas exchange following loss of ventilating areas, or inability to introduce air and eliminate it from the lungs, leading to necessity to favor gas exchange artificially.

The main issues concerning mechanical ventilation are: when to start, what type to use and how to apply it (1-4).

When?
The following are required to define when to begin treatment:

• Assessment of work of breathing and energy consumption necessary to obtain gas exchange
  
  
• Child's residual compensation capacity
  
  
• Forecast lung pathology evolution (e.g. aspiration syndrome vs. chemical pneumonia (Figure 1), chest trauma vs. ARDS, apnea in premature babies vs. severe hypo-ventilation and hypoxia, etc.).

Figure 1A - Aspiration syndrome. Immediate intubation and broncho-suctioning, followed by ventilation with elevated PEEP levels in order to maintain bronchioles and alveoli continuously open, allows the removal of aspirated material, which could avoid evolution to chemical pneumonia and ARDS.

Figure 1B - Aspiration syndrome. Same case as figure 1A, 48 hours after intubation, bronchoalveolar lavage with surfactant and mechanical ventilation with 15 cm H2O of PEEP.






Hemo-gas-analysis (HGA) alone cannot justify mechanical ventilation because in certain clinical situations its deterioration occurs in advanced lung pathology, therefore requiring more invasive methodologies, which are subject to greater risk of complications.

Cyanosis is a late sign usually indicating severe or long-standing hypoxemia.