Preoperative changes of forced vital capacity due to body position do not correlate with postoperative respiratory function in obese subjects.
BACKGROUND
Obese patients are at risk of developing postoperative pulmonary complications. We hypothesized that preoperative changes in dynamic spirometry due to body posture would correlate with the drop of forced vital capacity (FVC) measured early after surgery.


METHODS
Thirty consecutive morbidly obese patients undergoing gastric banding were investigated. All subjects were studied the day before surgery (T0) and on postoperative day one (T1). Forced Vital Capacity (FVC) was measured, together with heart rate, mean arterial pressure and respiratory rate. At T0 measurements were taken in a random fashion with subjects in upright and in supine position. Subjects were then investigated after surgery in the supine position (T1). Postoperative pain was assessed at T1 using visual analogue scale. Intraoperative variables were also collected.


RESULTS
Body Mass Index (BMI) of the investigated subjects was 43.9 ± 5.7 Kg/m2 (range 33.8-60); their age was 40 ± 8 years. All dynamic spirometric data decreased significantly from upright to supine position (P<0.05) and after surgery from 3.07 L (2.77-3.71) to 1.50 (1.15-2.12) (FVC T0 supine vs. T1, P<0.05). Changes of FVC due to body position did not correlate with changes of FVC occurring after surgery (R2=0.105, P=0.081). When subjects were stratified by the median postoperative drop of FVC (45.74%), preoperative (anthropometric and spirometric data), intraoperative (ventilatory settings and hemodynamics) and postoperative (FVC and pain) parameters were similar between groups. The duration of pneumoperitoneum was correlated with the drop of FVC (R2=0.551, P<0.05).


CONCLUSIONS
The derangement of FVC that occurs in obese subjects after gastric banding is not predictable before surgery from anthropometric or spirometric data. The duration of pneumoperitoneum significantly contributes to postoperative impairment of respiratory function.
Dipartimento di Anestesia Rianimazione (Intensiva e Subintensiva) e Terapia del dolore, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milano, Italy. franco.valenza@unimi.it
F
F
Valenza
S
S
Froio
S
S
Coppola
F
F
Vagginelli
A
A
Tiby
M C
MC
Marenghi
E
E
Mozzi
G C
GC
Roviaro
L
L
Gattinoni
D000328:Adult; D050110:Bariatric Surgery / Q000379:methods*; D005260:Female; D006801:Humans; D010535:Laparoscopy; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology* / Q000601:surgery*; D056888:Patient Positioning; D011028:Pneumoperitoneum, Artificial; D011237:Predictive Value of Tests; D057234:Preoperative Period; D012129:Respiratory Function Tests; D016683:Supine Position / Q000502:physiology; D014797:Vital Capacity / Q000502:physiology*; D055815:Young Adult