The non-invasive mechanical ventilation: the experience of the department of Internal Medicine and Critical Area of the Polyclinic Hospital of Modena

Acute respiratory failure (ARF) is a deficiency of the respiratory system that causes an alteration of normal levels of oxygen and/or carbon dioxide in the blood. ARF may be due to alterations in gaseous diffusion in alveolar-capillary level (type “1” acute respiratory failure), or to alterations in the functioning of the respiratory pump (type “2” acute respiratory failure) or to an association of the above causes. ARF specific etiological treatment must be associated to oxygen administration, through ventilation, which may be spontaneous or mechanical (non-invasive or invasive). The actual study describes experience about non-invasive mechanical ventilation in the department of Internal Medicine and Critical Area of the Polyclinic Hospital of Modena, from 2010 to 2014, examining clinical parameters and outcomes. Respiratory failure is a condition in which the respiratory system is not able to adequately carry out its gas exchange functions, such as oxygenation of the arterial blood and/or elimination of carbon dioxide from the venous blood. Conventionally, (1),(2),(3) respiratory failure is defined in case of: Partial pressure of arterial oxygen (PaO2) <60 mmHg; Partial pressure of carbon dioxide in the arterial blood (PCO2)> 45 mmHg; Association of both previous. You can distinguish two types of acute respiratory failure(4)(ARF): ARF type “1”, with gas exchange impairment and hypoxemia (associated with hypo/normocapnia). The pathophysiological mechanism behind is an important intrapulmonary shunt with changes in ventilation/perfusion ratio. Generally diseases responsible for this condition are acute pulmonary edema, ARDS, severe pneumonia and pulmonary embolism. ARF type “2”, with hypoventilation and hypercapnia. It is caused by a reduction of the ventilation volume/minute or by an increase of physiologic dead space. Among the most common diseases there are neuromuscular diseases, myopathies, chronic obstructive pulmonary disease (COPD), bronchial asthma and restrictive lung disease. The two types of respiratory failure are closely connected and can evolve into one another. The ARF therapy can be divided into: Etiological therapy: it is directed to the treatment of the specific cause that induced ARF, it can be delivered with inotropic agents, antibiotics, bronchodilators, steroids etc. Supportive therapy (or symptomatic): aimed at correcting hypoxemia and respiratory acidosis, is indicated in all respiratory insufficiencies and it is based on the administration of O2 and postural therapy. Ventilation can be spontaneous (delivered by low or high flow systems) or mechanical. Mechanical ventilation is classifiable under invasive ventilation (IMV) or non-invasive (NIV). The IMV provides the invasion of the patient’s airways to put them in communication with the respiratory system. It can be through tracheal intubation or tracheotomy and it’s a relevant method adopted by resuscitation intensive departments and partly by respiratory diseases departments. The NIV despite is a method that requires training and experience to be used optimally, it has the advantage to be used in emergency medicine departments and in other departments from specialists who are not resuscitators or pulmonologists. Moreover, compared to the IMV, the NIV offers the following advantages: reduction in the respiratory work, absence of complications related to prosthesis, possibility of avoiding sedation required for the IMV, conservation of laryngeal functions and cost reduction.(5) The NIV techniques most used in emergency medicine departments are CPAP (Continuous positive airway pressure) and BiPAP (or BiLevel - BiLevel positive airway pressure) CPAP provides a predetermined positive pressure, greater than atmospheric, which is maintained constant throughout the respiratory cycle, and it improves oxygenation by increasing the functional residual capacity, favouring the recruitment and the patency of the alveoli excluded from the ventilation and improving the relationship between ventilation and perfusion. The main indications for CPAP are acute cardiogenic pulmonary edema (ACPE), hypoxic and not hypercapnic ARF, obstructive sleep apnea syndrome (OSAS); atelectasis. (8),(9),(10) BiPAP provides two different levels of positive pressure, which are an inspiratory positive airway pressure (IPAP) and an expiratory positive airway pressure (EPAP). BiPAP facilitates the removal of air exhaled and prevents cases of re-breathing of CO2. It also reduces the patient's work of breathing. The main indications to BiPAP are hypercapnic ARF, chronic obstructive pulmonary disease (COPD) exacerbation, pneumonia, neuromuscular disorders, dysfunction of the respiratory center (sedation/intoxication), shock (cardiovascular/septic). (11), (12)