mechanical ventilation, the use of an apparatus designed to intermittently or continuously assist or control pulmonary ventilation. The use of a mechanical ventilator is indicated as a supportive measure in patients affected by respiratory paralysis and in those with ventilatory failure manifested by either alveolar hypoventilation, hypoxemia, or both. ▪ METHOD: Many types of ventilators are available. There are two major groups of ventilators: (1) those that generate negative pressure on the exterior surface of the chest, and (2) those that provide intrathoracic positive pressure. ▪ INTERVENTIONS: Regardless of the model and capabilities of the mechanical ventilator being used in the treatment of a patient with inadequate ventilation, there are certain general principles that are basic to the competent care of the patient. It is essential that all those who accept responsibility for the care of the patient be fully aware of the physiologic effects of mechanical ventilation, particularly in regard to the relationship between the distribution of inspired air in the lung and the status of the blood gases and pH. A second consideration in patient care and assessment of the effects of mechanical ventilation is that of its influence on circulation. An increase in intrathoracic pressure can interfere with the flow of blood through the great vessels and chambers of the heart. The effect can be a pooling of blood in the veins and capillaries of the abdominal organs and a resultant peripheral vascular collapse. Frequent determinations of pulse rate and blood pressure are necessary to detect early development of this complication and ensure prompt treatment. A third consideration is that of the effects of mechanical ventilation on the body fluid–antidiuretic hormone balance. Careful monitoring of the patient’s fluid status is required. Finally, a thorough knowledge of the apparatus being used for mechanical ventilation is vital to competent care of the patient. No one should attempt to give patient care without prior instruction in the purpose of the machine and the physiologic and physical principles upon which it operates. Patients and/or families who are discharged with a ventilator should also have this knowledge of operation. ▪ OUTCOME CRITERIA: Weaning from a ventilator is begun when the clinical evaluation of the patient indicates that full ventilatory support is no longer needed.
