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University of Ancona Ancona, Italy
Correspondence to: Alessandro Brunelli, MD, Via S Margherita 23, Ancona 60129, Italy; e-mail: alexit_2000{at}yahoo.com
To the Editor:
We read with great interest the article of Miyoshi et al (August 2000)1 on the early postoperative exercise capacity of 16 patients who had undergone to standard posterolateral thoracotomy and lung resection.
In one of their analyses, they compared the patients (31.3% of
those in their series) who did not reach the empirical anaerobic
threshold expressed by the venous blood lactate level of 2.2 mmol/L
(La-2.2) during oxygen uptake
(
O2) with those who reached
the threshold during the first postoperative cycle ergometer exercise
test (mean [± SD], 9 ± 2 postoperative days). Miyoshi et al
found that the circulatory and ventilatory parameters were larger in
patients with La-2.2 than in those without, and that both heart rate
and respiratory reserves were smaller in the patients with La-2.2 than
in those without. They concluded that pain from the surgical wound in
the chest could be the most important limiting factor for patients
without La-2.2 in the early postoperative period, even though
subjective factors were not obtained in their study.
We performed a similar prospective study on 122 patients who were
enrolled in our study from December 1999 through February 2001 and had
undergone muscle-sparing thoracotomies and lung resections
(segmentectomy/wedge resection, 15 patients; lobectomy, 88 patients;
pneumonectomy, 19 patients) for lung carcinoma. Our exercise
methodology consisted of a maximal symptom-limited, stair-climbing test
that was administered at the time of the patient’s discharge from the
hospital (mean, 8.2 ± 3.3 postoperative days). In our study, 24
patients (19.7% of our series) did not reach the empirical anaerobic
threshold of La-2.2 O2.
However, no significant differences were detected between this group of
patients and the others who reached the La-2.2
O2, in terms of calculated
work, maximal O2
(O2max; expressed as
milliliters per minute, milliliters per minute per kilogram, or as the
percentage of the predicted value),
O2max/body surface area ratio,
and O2 pulse.2
Moreover, hemodynamic
variables (ie, cardiac output, cardiac index, oxygen
delivery, extraction ratio, and heart rate reserve), which were
calculated by the Fick method, did not result in significant
differences between the two groups of patients.
The only parameter that was significantly reduced in the group without La-2.2 vs the group with La-2.2 was the number of steps climbed (mean, 77.2 ± 30.8 vs 101.6 ± 33.2, respectively; p = 0.001 [Student’s t test]).
We performed also a subjective analysis concerning the main symptoms that limited the patients’ exercise, and we found no difference between the two groups of patients. In particular, only three patients in the group without La-2.2 stopped exercising because of chest pain at the surgical wound. Dyspnea was the predominant symptom, followed by leg pain and physical exhaustion, in both groups of patients.
Contrary to what was reported by Miyoshi et al,1 we believe that in the early postoperative period the chest pain from thoracotomy is not the most important limiting factor for the patients who do not reach the empirical anaerobic threshold. However, differences in the type of thoracotomy incision and in the methodology of the exercise test have to be taken into account.
Since there was no difference in the values of ergometric variables between the two groups of patients in our series, a low level of arterial blood lactates at peak exercise in some patients may be explained by a previously reported intersubject variability of the anaerobic threshold value3 or may simply reflect the better fitness of some individuals for endurance (aerobic) exercise.4
References
Dokkyo University School of Medicine Tochigi, Japan
Correspondence to: Shinichiro Miyoshi, MD, 880 Kitakobayashi, Mibu, Tochigi, 321-0293, Japan;
To the Editor:
We thank Dr. Brunelli and his colleagues for their interest in our article (August 2000).1 They performed a similar prospective study on lung cancer patients in the early postoperative period (mean [± SD] postoperative days, 8.2 ± 3.3), using a stair-climbing test. Although they observed patients without a venous blood lactate level of 2.2 mmol/L (La-2.2) [24 subjects; 19.7% of their series], as we did, there was no difference in the values of ergometric variables between patients with and without La-2.2. These findings were different from our results.
As has been pointed out, there were two major differences
between our study and that of Brunelli et al. We employed a standard
posterolateral thoracotomy in all patients studied, while Brunelli et
al performed a muscle-sparing thoracotomy in their patients. This
variation may produce differences in postoperative chest pain and
compliance of the chest wall, especially in the early postoperative
period. Patients are likely to be able to attain a larger maximum
oxygen uptake (O2max) if they do not feel chest pain
during exercise. The differences between these thoracotomy approaches
were not detected by pulmonary function testing.2
A
cardiopulmonary exercise test is a loading test for both cardiovascular
and respiratory systems, and may be more sensitive when evaluating the
differences between these thoracotomy approaches.
The other difference between the two studies is the methodology used
for the exercise test. We utilized an incremental exercise test, which
was designed to obtain an anaerobic threshold as well as
O2max. A stair-climbing test is considered to be
constant work under great stress and is not meant for detecting the
anaerobic threshold. Although it is simple and useful for clinical
use,3
a stair-climbing test has limitations when
investigating the mechanism behind the results.
References
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