Em. Tschernko et al., CHANGES IN VENTILATORY MECHANICS AND DIAPHRAGMATIC FUNCTION AFTER LUNG-VOLUME REDUCTION SURGERY IN PATIENTS WITH COPD, Thorax, 52(6), 1997, pp. 545-550
Background - Lung volume reduction (LVR) has recently been used to tre
at severe emphysema. About 25% of the volume of each lung is removed w
ith this method. Little is known about the mechanism of functional imp
rovement so a study was undertaken to investigate the changes in venti
latory mechanics and diaphragmatic function in eight patients after LV
R. Methods - Measurements of work of breathing (WOE), intrinsic positi
ve end expiratory pressure (PEEPi), dynamic compliance (Cdyn), and art
erial carbon dioxide tension (Paco(2)) were performed on the day befor
e surgery and daily for seven days after surgery, as well as one, thre
e, and six months after surgery. All measurements were performed on sp
ontaneously breathing patients, simultaneously assessing oesophageal p
ressure via an oesophageal balloon catheter and air flow via a tightly
adjusted mask. Diaphragmatic function was evaluated by measuring oeso
phageal and transdiaphragmatic pressure (Pdi) preoperatively and at on
e, three, and six months postoperatively. Results - Mean forced expira
tory volume in one second (FEV1) was 23 (3.6)% predicted, and all pati
ents were oxygen dependent before the operation. One day after LVR the
mean decrease in WOE was 0.93 (95% confidence interval (CI) 0.46 to 1
.40) joule/1, the mean decrease in PEEPi was 0.61 (95% CI 0.35 to 0.87
) kPa, and the mean increase in Cdyn was 182.5 (95% CI 80.0 to 284.2)
ml/kPa. Similar changes were found seven days and six months after sur
gery. Pace, was higher on the day after the operation but was signific
antly reduced six months later. Pdi was increased three and six months
after surgery. Conclusions - Ventilatory mechanics improved immediate
ly after LVR, probably by decompression of lung tissue and relief of t
horacic distension. An improvement in diaphragmatic function three and
six months postoperatively also contributes to improved respiratory f
unction after LVR.