[Ventilation in anesthesia: a retrospective study.].
OBJECTIVE
Lung mechanics impairment, Functional Residual Capacity decrease and atelectasis have been described during general anesthesia. This study aimed at retrospectively evaluating ventilation standards in place at the Central Institute, Hospital das Clinicas, Medical School, University of São Paulo (HCFMUSP).


METHODS
Data on 240 patients under general anesthesia, neuromuscular block and mechanical ventilation were recorded. Ventilation standards - tidal volume in ml (VT), respiratory rate per minute, airway pressure in cmH2O, fresh gas flow in L.min-1, SpO2 and P ET CO2 - were recorded, as well as gender, age, weight and height. Body mass index (BMI) was calculated and patients were distributed in four groups: BMI < 20; 20-25; 25-30 and > 30 kg/m(2).


RESULTS
There has been a linear correlation between tidal volume (VT) and weight (r=0.640), and BMI (r=0.467). VT by body mass (ml.kg-1) has shown to be inversely related to BMI: BMI < 20 with 10.74 +/- 1.39; BMI 20-25 with 9.67 +/- 1.08; BMI 25-30 to 8.54 +/- 1.09; BMI > 30 to 7.86 +/- 1.26 (p < 0.001, ANOVA). There have been no differences among groups in respiratory rate. During data collection, males (n = 123) and females (n = 117) had similar SpO2 and P ET CO2, as well as BMI. Positive end-expiratory pressure (PEEP) was installed in 78 procedures (33%).


CONCLUSIONS
These descriptive data allow us to state that mechanical ventilation standards in anesthesia at HCFMUSP use a tidal volume close to 9 ml.kg-1 and a respiratory rate of 10 incursions per minute. PEEP is not widely applied, but when installed it is approximately 4 cmH2O. Weight and BMI had a positive correlation with VT, and VT/weight (ml.kg-1) ratio was inversely related to BMI.
Vieira
Joaquim Edson
JE
Depto Clínica Médica, ICHC, Faculdade de Medicina, USP.
Silva
Basílio Afonso Ribeiro
BA
Garcia Júnior
Daniel
D