Artificial Ventilation Of The Lung:

Mohamed Goda Khedr

Mechanical ventilation has been used as a supportive therapy inessential care of critically ill patients, since the incepts of mechanicalventilation there has been considerable progresses in the modes ofventilation that has been identified with the development of critical careunits more than any other technological advance.While factors to the decision to initiate therapy are relativelyuniform, the specific modes to be chosen vary, depending on the nature ofthe patients problem, local practice and physician perception. The recentaddition of new modes emphasize the ongoing quest for improvingpatient’s outcome through applied physiology. Indications of artificialventilation include respiratory failure in the form of hypoxemia and orhypercarbia. In addition, mechanical ventilation is often initiated orcontinued as mean of physiologic support in critically ill patients forexample in case of cardiovascular collapse, sepsis or multiple organfailure.Since potential damage to lung tissue and cardiovascularembarrassment were known to result from conventional modes ofventilation. New modes of ventilation were designed to assure adequateventilation in different situation with minimal complications. Each ofthese modes has a specific advantage they include:a- Synchronized intermittent ventilation (SIMV): it include a continuousflow system that allows the patient to spontaneously breath betweenthe positive-pressure breaths.b- Pressure support (PS): this spontaneous mode is used alone or incombination with SIMV as a mode of weaning.c- High frequency ventilation (HFV): that can be useful in certainsituations as example difficult airway management, proceduresinvolving upper airway. Adult and infant respiratory distresssyndrome.d- Inverse-ratio ventilation: the lower peak airway pressure in this modemay reduce the risk of barotrauma. Inverse I : E ration achieves betteroxygenation. This mode is preferred in ARDS and pulmonary edema.e- Airway pressure-released ventilation: which is a form of pressurepresent ventilation in which the lung is allowed to deflate to ambientpressure passively, as APRV maintains an increased FRC throughoutmost of ventilatory cycle arterial oxygenation is better maintained.f- Differential lung ventilation: that have revolutionized the approach, tomechanical ventilatory support, to patient with asymmetrical lunginjury,g- Non-invasive positive airway pressure: has been designed to providepartial non-invasive pressure support. It can be defined s pressurecontrolled ventilation, in a system allowing unrestricted spontaneousbreathing at any moment of the ventilatory cycle.h- Positive and expiratory pressure (PEEP): that can be used duringcontrolled or spontaneous ventilation, increases the functional residualcapacity till the upper border of alveolar expansion is reached.Continuous positive airway pressure (CPAP) refers to application ofpositive airway pressure throughout the entire respiratory cycle,during spontaneous ventilation. In can be also used with modes suchas IMV/SIMV. Positive airway pressure is beneficial because arterialoxygenation is improved with a reduction in oxygen requirements.Complications are undesirable consequences of therapy directlyleading to increased morbidity and mortality, first complications oftracheal intubation second complications of mechanical ventilation itself.Knowledge about new modes of ventilation allow utilization of theproper mode in the proper situation and so minimizing complicationsresulting from artificial ventilation.