The Journal of Thoracic and Cardiovascular Surgery, Vol 77, 175-182, Copyright © 1979 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Predicting the need for prolonged ventilatory support in adult cardiac patients
RM Peters, JE Brimm and JR Utley
Forty-nine cardiac surgical patients had ventilatory function tests and
measurements of maximum inspiratory (MIP) and maximum expiratory (MEP)
pressures preoperatively. The differences between the values of various
function tests were compared for patients requiring less than 24 hours of
ventilator support and those requiring more than 24 hours. There was a
significant difference in the mean values for the two groups in vital
capacity (VC) first-second forced expired volume (FEV) midexpiratory flow
between 50 and 75 (MMEF 50--75) and 75--85 percent of expired volume (MMEF
75--85), and MEP. The standard deviations of each of the variables were so
large that the clinical usefulness was limited. However, when discriminant
analysis was used for more than one variable, the combination of MMEF
75--85 and MEP predicted success or failure to wean in 24 hours correctly
in 90 percent of instances. On the basis of these simple tests, patients
predicted to succeed should be weaned from ventilator support on recovery
from anesthesia. Those predicted to fail should be placed on intermittent
mandatory ventilation (IMV) and should be weaned following a planned,
logical process.
