Effect of lung mechanics on mechanically assisted flows and volumes.
OBJECTIVE
To correlate the air flows generated by mechanical insufflation-exsufflation as a function of pressure delivery in a lung model at two pulmonary compliance and three airway resistance settings.


METHODS
With each combination of pulmonary compliances of 25 and 50 ml/cm H2O and airway resistances of 6, 11, and 17 cm H2O/liter/sec, ten cycles of mechanical insufflation-exsufflation were applied using pressure deliveries of 40 to -40, 50 to -50, 60 to -60, and 70 to -70 cm H2O. The resulting peak exsufflation flows and volumes were recorded.


RESULTS
In a multivariate analysis, the pulmonary compliance, airway resistance, and pressure delivery were all found to significantly affect exsufflation flows and volumes such that a decreased pulmonary compliance or an increased airway resistance produced a decrease in exsufflation flow and volume, whereas an increased pressure delivery produced greater exsufflation flow and volume.


CONCLUSIONS
Although mechanical insufflation-exsufflation pressures of 40 to -40 cm H2O are generally adequate for most patients with normal lung compliance and airway resistance, higher settings are often required when compliance decreases, by obesity or scoliosis, and possibly when airway resistance is increased.
Unidad de Rehabilitación y Ventilación, Servicio de Neumología, Hospital Clínico Universitario, Universitat de València, Valencia, Spain.
Jesús
J
Sancho
Emilio
E
Servera
Julio
J
Marín
Pedro
P
Vergara
F Javier
FJ
Belda
John R
JR
Bach
D000403:Airway Resistance; D006801:Humans; D007327:Insufflation / Q000295:instrumentation / Q000379:methods; D008168:Lung / Q000503:physiopathology; D008171:Lung Diseases / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D008954:Models, Biological; D008961:Models, Structural; D015999:Multivariate Analysis; D011175:Positive-Pressure Respiration; D012123:Pulmonary Ventilation; D012121:Respiration, Artificial / Q000009:adverse effects / Q000379:methods / Q000592:standards; D015656:Respiratory Mechanics; D012122:Ventilators, Mechanical / Q000009:adverse effects / Q000592:standards