PT - JOURNAL ARTICLE
AU - Mireles-Cabodevila, Eduardo
AU - Chatburn, Robert L
TI - Mid-Frequency Ventilation: Unconventional Use of Conventional Mechanical Ventilation as a Lung-Protection Strategy
DP - 2008 Dec 01
TA - Respiratory Care
PG - 1669--1677
VI - 53
IP - 12
4099 - http://rc.rcjournal.com/content/53/12/1669.short
4100 - http://rc.rcjournal.com/content/53/12/1669.full
AB - BACKGROUND: Studies have found that increasing the respiratory frequency during mechanical ventilation does not always improve alveolar minute ventilation and may cause air-trapping. OBJECTIVE: To investigate the theoretical and practical basis of higher-than-normal ventilation frequencies. METHODS: We used an interactive mathematical model of ventilator output during pressure-control ventilation to predict the frequency at which alveolar ventilation is maximized with the lowest tidal volume (VT) for a given pressure. We then tested our predicted optimum frequencies and VT values with various lung compliances and higher-than-normal frequencies, with a lung simulator and 5 mechanical ventilators (DrĂ¤ger Evita XL, Hamilton Galileo, Puritan Bennett 840, Siemens Servo 300 and Servo-i). RESULTS: Compliances between 10 mL/cm H2O and 42 mL/cm H2O yielded VT between 4.1 mL/kg (optimum frequency 75 cycles/min) and 6.0 mL/kg (optimum frequency 27 cycles/min). The intrinsic positive end-expiratory pressure at the optimum frequency was always less than 2 cm H2O. All the ventilators except the Hamilton Galileo had an optimum frequency near 50 cycles/min, whereas the predicted optimum frequency was 60 cycles/min. CONCLUSIONS: With these ventilators and pressure-control ventilation, alveolar minute ventilation can be optimized with higher-than-normal frequency and lower VT than is commonly used in patients with acute respiratory distress syndrome. We call this strategy mid-frequency ventilation.