The influence of obesity and underweightness on respiratory function of geriatric patients undergoing surgery.

We investigated the influence of obesity and underweightness on the respiratory function of 228 patients over 65 ys. old undergoing elective surgery. The parameters we studied were preoperative Pa(O)(2) (Pa(O)(2)-pre), Pa(O)(2) under general anesthesia (Pa(O)(2)-op) and preoperative spirometric values including data from flow-volume curves and closing volumes. Triceps skinfold thickness (TSF), body mass index (BMI), Broca's index (BI) and Onodera's prognostic nutritional index (PNI) were measured or calculated. Respiratory parameters were compared between 3 groups; overweight (BMI >23), normal weight (BMI 20-22), underweight (BMI <19). Single and multiple correlations were analyzed between 3 nutritional parameters (BMI, TSF, PNI) and respiratory values. As a result, Pa(O)(2)-pre and Pa(O)(2)-op in overweight group were lower than those in the other groups. None of other parameters showed significant differences between the 3 groups. In multiple regression analysis, BMI correlated with Pa(O)(2)-pre (r = -0.24), Pa(O)(2)-op (r = -0.43), %VC (r = 0.18), peak flow rate (PFR, r = 0.17) and V(50)/HT (r = 0.18). TSF correlated with Pa(O)(2)-pre (r = -0.22), %MVV (r = -0.28) and RV/TLC (r = 0.28). PNI correlated with PFR (r = 0.23). We concluded that overweightness has greater influence on respiratory function of elderly patients than underweightness and that arterial blood gas analysis is essential in preoperative assessment of obese geriatric patients.