Intermittent high frequency ventilation: a new mode to measure changes in lung volume and alveolar gas concentration, enhance CO2 elimination and reduce intrapulmonary pressures.
A new method of artificial ventilation, intermittent high frequency ventilation (IHFV), is described in which high frequency ventilation (HFV) is intermittently interrupted so that short periods of ventilation and pauses in ventilation occur in sequence several times a minute. During the pauses in ventilation the increase in lung volume, which occurs during the short periods of HFV, is either exhaled completely or to a predetermined level which prevents sustained hyperinflation of the lungs but allows the maintenance of PEEP if required. The volume of gas expired during the ventilation pauses, i.e. gas retained during the periods of HFV, is measured. When this trapped gas is exhaled completely, the mean airway and compliance pressures are reduced by up to 50% compared to continuous HFV at the same frequency, inspiration:expiration (I:E) ratio and low tidal volume (VT). The alveolar CO2 concentration was measured in gas expired towards the end of the pauses in ventilation. CO2 elimination was improved, especially at high frequencies of ventilation, which allowed a further reduction in inflation pressures while maintaining a constant PaCO2.
Chakrabarti
M K
MK
Department of Anaesthetics, Royal Postgraduate Medical School, Hammersmith Hospital, London, UK.
Swenzen
G O
GO
Whitwam
J G
JG
D000818:Animals; D004285:Dogs; D006612:High-Frequency Ventilation / Q000379:methods*; D008170:Lung Compliance; D008176:Lung Volume Measurements; D011312:Pressure; D011659:Pulmonary Gas Exchange