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Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094

Abstract

BENSENOR, Fábio Ely Martins  and  AULER JUNIOR, José Otávio Costa. PETCO2 and SpO2 allow adequate ventilatory adjustment in morbidly obese patients. Rev. Bras. Anestesiol. [online]. 2004, vol.54, n.4, pp. 542-552. ISSN 0034-7094.  http://dx.doi.org/10.1590/S0034-70942004000400010.

BACKGROUND AND OBJECTIVES: Ventilation strategies for anesthesia in morbidly obese patients have been investigated, but an agreement has not been achieved yet. This study aimed at clinically evaluating ventilation adjustments based on oximetry and capnography readings in these patients during anesthesia. METHODS: Consent was obtained from the Institutional Ethics Committee and from patients. Smokers and respiratory or cardiac disease patients were excluded. Eleven patients with Body Mass Index (BMI) of 59.2 ± 8.3 undergoing gastroplasty under general anesthesia were studied (Group O), with a control group (NO) composed of 8 non-obese patients (BMI 20.2 ± 3.9) submitted to gastrectomy. Ventilator was adjusted to keep PETCO2 below 40 mmHg and SpO2 above 95%. PEEP was not used. Through a CO2SMO Plus respiratory monitor, airway, alveolar and physiologic dead spaces (respectively VD aw, VD phy and VD alv), as well as alveolar tidal volume (TV alv) were measured. Arterial and central venous blood samples were used to calculate PaO2/FIO2 and VD phy/TV relationships. Data were compared and evaluated by ANOVA (p < 0.05). RESULTS: Tidal volume was 4.2 ± 0.4 mL.kg-1 in Group O and 7.9 ± 2.3 mL.kg-1 in Group NO for measured weight, and 11.5 ± 1.8 mL.kg-1 in Group O and 6.6 ± 1.1 mL.kg-1 in Group NO for ideal weight. PaO2 was lower and TV alv was higher in Group O (p < 0.008 and 0.0001, respectively). No difference was found in PaCO2, VD phy, VD alv and VD aw. CONCLUSIONS: SpO2 and PETCO2 seem to assure adequate ventilation, which can be achieved in morbidly obese patients with tidal volumes adjusted to ideal weight.

Keywords : DISEASES [morbid obesity]; VENTILATION [controlled mechanical].

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