Effects of the beach chair position, positive end-expiratory pressure, and pneumoperitoneum on respiratory function in morbidly obese patients during anesthesia and paralysis.
BACKGROUND
The authors studied the effects of the beach chair (BC) position, 10 cm H2O positive end-expiratory pressure (PEEP), and pneumoperitoneum on respiratory function in morbidly obese patients undergoing laparoscopic gastric banding.


METHODS
The authors studied 20 patients (body mass index 42 +/- 5 kg/m2) during the supine and BC positions, before and after pneumoperitoneum was instituted (13.6 +/- 1.2 mmHg). PEEP was applied during each combination of position and pneumoperitoneum. The authors measured elastance (E,rs) of the respiratory system, end-expiratory lung volume (helium technique), and arterial oxygen tension. Pressure-volume curves were also taken (occlusion technique). Patients were paralyzed during total intravenous anesthesia. Tidal volume (10.5 +/- 1 ml/kg ideal body weight) and respiratory rate (11 +/- 1 breaths/min) were kept constant throughout.


RESULTS
In the supine position, respiratory function was abnormal: E,rs was 21.71 +/- 5.26 cm H2O/l, and end-expiratory lung volume was 0.46 +/- 0.1 l. Both the BC position and PEEP improved E,rs (P < 0.01). End-expiratory lung volume almost doubled (0.83 +/- 0.3 and 0.85 +/- 0.3 l, BC and PEEP, respectively; P < 0.01 vs. supine zero end-expiratory pressure), with no evidence of lung recruitment (0.04 +/- 0.1 l in the supine and 0.07 +/- 0.2 in the BC position). PEEP was associated with higher airway pressures than the BC position (22.1 +/- 2.01 vs. 13.8 +/- 1.8 cm H2O; P < 0.01). Pneumoperitoneum further worsened E,rs (31.59 +/- 6.73; P < 0.01) and end-expiratory lung volume (0.35 +/- 0.1 l; P < 0.01). Changes of lung volume correlated with changes of oxygenation (linear regression, R2 = 0.524, P < 0.001) so that during pneumoperitoneum, only the combination of the BC position and PEEP improved oxygenation.


CONCLUSIONS
The BC position and PEEP counteracted the major derangements of respiratory function produced by anesthesia and paralysis. During pneumoperitoneum, only the combination of the two maneuvers improved oxygenation.
Valenza
Franco
F
Istituto di Anestesia e Rianimazione, Fondazione Ospedale Maggiore, Mangiagalli e Regina Elena-IRCCS, Milan, Italy. franco.valenza@unimi.it
Vagginelli
Federica
F
Tiby
Alberto
A
Francesconi
Silvia
S
Ronzoni
Giulio
G
Guglielmi
Massimiliano
M
Zappa
Marco
M
Lattuada
Ezio
E
Gattinoni
Luciano
L
D000328:Adult; D000771:Anesthesia, Intravenous; D001784:Blood Gas Analysis; D001794:Blood Pressure; D015992:Body Mass Index; D005260:Female; D015391:Gastroplasty / Q000379:methods; D006339:Heart Rate; D006801:Humans; D010535:Laparoscopy; D008176:Lung Volume Measurements; D008297:Male; D009767:Obesity, Morbid / Q000503:physiopathology / Q000601:surgery*; D010100:Oxygen / Q000097:blood; D010243:Paralysis / Q000139:chemically induced*; D011028:Pneumoperitoneum, Artificial / Q000379:methods / Q000706:statistics & numerical data*; D011175:Positive-Pressure Respiration / Q000379:methods / Q000706:statistics & numerical data*; D011187:Posture; D012119:Respiration; D016683:Supine Position; D013990:Tidal Volume
D010100:Oxygen