Effects of lung volume reduction surgery on gas exchange and breathing pattern during maximum exercise.
BACKGROUND
The National Emphysema Treatment Trial studied lung volume reduction surgery (LVRS) for its effects on gas exchange, breathing pattern, and dyspnea during exercise in severe emphysema.


METHODS
Exercise testing was performed at baseline, and 6, 12, and 24 months. Minute ventilation (Ve), tidal volume (Vt), carbon dioxide output (Vco(2)), dyspnea rating, and workload were recorded at rest, 3 min of unloaded pedaling, and maximum exercise. Pao(2), Paco(2), pH, fraction of expired carbon dioxide, and bicarbonate were also collected in some subjects at these time points and each minute of testing. There were 1,218 patients enrolled in the study (mean [+/- SD] age, 66.6 +/- 6.1 years; mean, 61%; mean FEV(1), 0.77 +/- 0.24 L), with 238 patients participating in this substudy (mean age, 66.1 +/- 6.8 years; mean, 67%; mean FEV(1), 0.78 +/- 0.25 L).


RESULTS
At 6 months, LVRS patients had higher maximum Ve (32.8 vs 29.6 L/min, respectively; p = 0.001), Vco(2), (0.923 vs 0.820 L/min, respectively; p = 0.0003), Vt (1.18 vs 1.07 L, respectively; p = 0.001), heart rate (124 vs 121 beats/min, respectively; p = 0.02), and workload (49.3 vs 45.1 W, respectively; p = 0.04), but less breathlessness (as measured by Borg dyspnea scale score) [4.4 vs 5.2, respectively; p = 0.0001] and exercise ventilatory limitation (49.5% vs 71.9%, respectively; p = 0.001) than medical patients. LVRS patients with upper-lobe emphysema showed a downward shift in Paco(2) vs Vco(2) (p = 0.001). During exercise, LVRS patients breathed slower and deeper at 6 months (p = 0.01) and 12 months (p = 0.006), with reduced dead space at 6 months (p = 0.007) and 24 months (p = 0.006). Twelve months after patients underwent LVRS, dyspnea was less in patients with upper-lobe emphysema (p = 0.001) and non-upper-lobe emphysema (p = 0.007).


CONCLUSIONS
During exercise following LVRS, patients with severe emphysema improve carbon dioxide elimination and dead space, breathe slower and deeper, and report less dyspnea.
Criner
Gerard J
GJ
Temple University, Philadelphia, PA. Electronic address: crinerg@tuhs.temple.edu.
Belt
Patricia
P
Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
Sternberg
Alice L
AL
Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
Mosenifar
Zab
Z
Cedars-Sinai Medical Center, Los Angeles, CA.
Make
Barry J
BJ
National Jewish Medical and Research Center, Denver, CO.
Utz
James P
JP
Mayo Clinic, Rochester, MN.
Sciurba
Frank
F
University of Pittsburgh, Pittsburgh, PA.
D000368:Aged; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011013:Pneumonectomy; D011184:Postoperative Period; D011656:Pulmonary Emphysema / Q000503:physiopathology* / Q000601:surgery*; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012126:Respiratory Dead Space; D015656:Respiratory Mechanics; D012143:Respiratory Physiological Phenomena; D013990:Tidal Volume; D014939:Work of Breathing / Q000502:physiology; D016526:Workload