Lung reduction surgery in severe COPD decreases central drive and ventilatory response to CO2.
OBJECTIVE
Lung volume reduction surgery (LVRS) improves ventilatory function in selected patients with severe COPD. The reasons for the observed benefits include the following: increased elastic recoil, improved airflow, and lesser dynamic hyperinflation and decreased lung volumes. We reasoned that these changes could also alter respiratory drive.


METHODS
Respiratory central drive was prospectively assessed using the mouth occlusion pressure (P0.1), and the P0.1 response to increasing CO2 (P0.1/PETCO2 [end-tidal CO2 pressure]), in eight sequential patients before and 3 to 5 months after LVRS. Results were compared with those from 13 control subjects.


RESULTS
LVRS decreased total lung capacity from 7.44+/-1.8 L to 5.92+/-1.3 L (p<0.05) and residual volume from 4.97+/-1.5 L to 3.56+/-1.1 L (p<0.05). It also significantly improved FEV1 from 0.85+/-0.26 L to 0.99+/-0.26 L (p<0.05). Baseline P0.1 (3.4+/-1.8 vs 1.4+/-0.4 cm H2O, p<0.01) and P0.1/PETCO2 (0.24+/-0.07 vs 0.11+/-0.04 cm H2O/mm Hg, p<0.05) were higher in patients than in control subjects. After LVRS, P0.1 decreased from 3.4+/-1.8 to 1.3+/-0.75 cm H2O (p<0.01) and P0.1/PETCO2 from 0.24+/-0.07 to 0.16+/-0.06 cm H2O/mm Hg (p<0.05). These postoperative values were similar to those of control subjects. There were no correlations between changes in the factors known to influence central drive (PaO2, PaCO2, age, weight, height, FVC, and FEV1) and changes in P0.1.


CONCLUSIONS
We conclude that decreased ventilatory drive should be added to the list of benefits of LVRS, and may help explain the symptomatic improvement reported by many patients after this surgery.
Celli
B R
BR
Division of Pulmonary/Critical Care and Cardiovascular Surgery, St. Elizabeth's Medical Center, Tufts University, Boston, MA 02135, USA. bcelli@semc.org
Montes de Oca
M
M
Mendez
R
R
Stetz
J
J
D000367:Age Factors; D000368:Aged; D001827:Body Height; D001835:Body Weight; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000494:pharmacology*; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008170:Lung Compliance / Q000502:physiology; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D009055:Mouth / Q000502:physiology; D010100:Oxygen / Q000097:blood; D011013:Pneumonectomy; D011312:Pressure; D011446:Prospective Studies; D011656:Pulmonary Emphysema / Q000601:surgery*; D012123:Pulmonary Ventilation / Q000502:physiology; D012115:Residual Volume / Q000502:physiology; D012119:Respiration / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*; D013990:Tidal Volume / Q000502:physiology; D014109:Total Lung Capacity / Q000502:physiology; D014797:Vital Capacity / Q000502:physiology
D002245:Carbon Dioxide; D010100:Oxygen