Basic Types of Ventilators

Written by docteam Sunday, 27 February 2011 06:45

There are three basic types of ventilators. They are negative pressure, positive pressure, and high frequency.  Negative Pressure Ventilators (NPV) are rarely used. NPV produce negative pressure around the thorax and abdomen, lowering the alveolar pressure and producing inspiratory air flow. In home treatment of patients. NPV are occasionally used with neuromuscular or musculoskeletal disorders or severe chronic obstructive lung disease who are not candidates for intubation.

Positive Pressure Ventilators (PPV) cause inspiratory air flow by raising airway pressure. PPV are divided into three categories: pressure cycled, volume cycled, and time cycled (depending on the mechanisms that terminate inspiration). The patient's inspiratory effort trigger pressure-cycled ventilators to deliver air until a specific preset airway pressure is reached. Volume-cycled ventilators are designed to deliver a set volume of gas. Expiration follows passively. Air is delivered by time-cycled ventilators for a preset period. Consequently, they deliver a consistent tidal volume in spite of changes in the airway resistance or the lung compliance

High Frequency Ventilators (HFV) include :

• high-frequency positive pressure ventilation (HFPPV) uses a respiratory frequency of 40 to 100 breaths/min, and tidal volumes approaching the calculated dead space volume, achieving minute ventilation of about 30 L/min
• high-frequency jet ventilation (HFJV) uses a respiratory frequency between 100 and 300 breaths/min, and tidal volume less than dead space. Minute ventilation is usually greater than 20 L/min but is difficult to quantitate exactly
• high-frequency oscillation (HFO) uses a respiratory frequency of 300 to 3000 breaths/min, and tidal volumes of 10 to 100 mL