RESPIRATORY SYSTEM MECHANICS IN THE EARLY PHASE OF ACUTE RESPIRATORY-FAILURE DUE TO SEVERE KYPHOSCOLIOSIS

Objective: To evaluate respiratory mechanics in the early phase of dec ompensation in a group of seven patients with severe kyphoscoliosis (K S) (Cobb angle > 90 degrees) requiring mechanical ventilatory support. Design: Prospective clinical study with a control group. Setting: Gen eral intensive care unit at University of Rome ''La Sapienza'' Patient s: Seven consecutive patients affected by severe KS in the early phase of acute decompensation and a control group of six ASA (American Soci ety of Anesthesiology) 1 subjects who were mechanically ventilated dur ing minor surgery. Measurements and results: Respiratory mechanics wer e evaluated during constant flow-controlled mechanical ventilation at zero end-expiratory pressure with the end-inspiratory and end-expirato ry occlusion technique. In five patients who showed increased ohmic re sistance (RRSmin), we evaluated the possibility of reversing this incr ease with a charge dose of 6 mg/kg doxophylline i. v. In four KS patie nts, in whom a reliable esophageal pressure was confirmed by a positiv e occlusion test, we separated respiratory system data into lung and c hest wall component. All KS patients showed reduced values of respirat ory compliance (CRS) and increased respiratory resistance (RRS). The a verage basal values of CRS were 36 +/- 10 vs 58 +/- 8.5 cmH(2)O in con trol patients; RRSmax was 20 +/- 3.1 vs. 4.5 +/- 1.2 cmH(2)O/l per s; RRSmin 6.2 +/- 1.2 vs. 2 +/- 0.5 cmH(2)O/l per s: Delta RRS 14 +/- 2.6 cmH(2)O vs 2.4 +/- 0.7 cmH(2)O/l per s. All KS patients showed low va lues of intrinsic positive end-expiratory pressure (PEEPi) (1.8 +/- 1. 5 cmH(2)O). Separation of lung and chest-wall mechanics, performed onl y in four patients, showed a reduction in both lung (66.7 +/- 7.2 ml/c mH(2)O) and chest wall values (84 +/- 8.2 ml/cmH(2)O), while both Rmax (L) and Rmax(CW) were increased (16.6 +/- 2 and 2.8 +/- 0.4 cmH(2)O/l per s, respectively). Infusion of doxophylline did not significantly c hange respiratory mechanics when evaluated 15, 30, and 45 min after th e infusion. Conclusions: During acute decompensation, both lung and ch est-wall compliance are severely reduced in KS patients: conversely, a nd, contrary to that in patients with chronic obstructive pulmonary di sease, increases in airway resistance and PEEPi seem to play only a se condary role.