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Eur J Cardiothorac Surg 2003;24:145-148
© 2003 Elsevier Science NL
Unit of Thoracic Surgery, Department of Respiratory Diseases, ‘Umberto I’ Hospital, Ancona, Italy
Received 12 December 2002; received in revised form 8 March 2003; accepted 17 March 2003.
* Corresponding author. Via S. Margherita 23, 60129 Ancona, Italy. Tel.: +39-071-59-644-39; fax: +39-071-596-4433
e-mail: alexit_2000{at}yahoo.com
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Abstract |
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 Top Abstract 1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
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Key Words: Exercise test • Stair-climbing test • Oxygen desaturation • Lung resection • Lung cancer
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1. Introduction |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
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The objective of this study was to identify the predictors of postoperative exercise oxygen desaturation (EOD) following lobectomy or pneumonectomy for lung cancer, in order to select those patients to be submitted to postoperative maximal exercise test for assessment of their oxygen saturation status.
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2. Patients and methods |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
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The following spirometric variables were considered for the present study: forced expiratory volume in 1 s (FEV1); forced vital capacity (FVC); carbon monoxide lung diffusion (DLCO); FEV1/FVC ratio; predicted postoperative FEV1 (ppoFEV1) calculated by the formula (preoperative FEV1/number of preoperative functioning segments)xnumber of postoperative functioning segments; predicted postoperative DLCO (ppoDLCO) calculated by the formula (preoperative DLCO/number of preoperative functioning segments)xnumber of postoperative functioning segments. All the spirometric data, with the exception of FEV1/FVC ratio, were expressed as percentage of predicted value for age, sex, and height. Pulmonary function tests were performed according to the American Thoracic Society criteria. DLCO was measured using the single-breath method.
The estimate of the number of functioning segments was made by using computed tomographic (CT) scan and bronchoscopy findings. In patients with a calculated ppoFEV1 less than 50% of predicted and in all pneumonectomy candidates, a quantitative perfusion lung scan was performed [2]. The simple calculation of ppoFEV1 was shown to be as reliable as lung perfusion scan [2]. The percentage of functional lung tissue removed during operation (Func loss%) was calculated by means of CT scan, bronchoscopy, and when performed, quantitative lung perfusion scan [3]. The following conditions were indicative of a concomitant cardiac disease: previous cardiac surgery, previous myocardial infarction, history of coronary artery disease, current treatment for arrhythmia, cardiac failure, or hypertension.
All the patients with a concomitant cardiac disease underwent an extensive cardiac evaluation before the exercise test and they were allowed to perform stair climbing only when deemed in a hemodynamically stable state.
Patients with and without postoperative EOD were compared by means of the Student's t test (for the numerical variables) and the Chi-square test (for the categorical variables). Significant variables at univariate analysis were then used as predictors in a stepwise logistic regression analysis (dependent variable: presence of postoperative EOD).
All tests were two-tailed, with a significance level of 0.05. Statistical analysis was performed by using the statistical software Statview 5.0 (SAS Inc., Cary, NC, USA).
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3. Results |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
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In those patients who did not have postoperative EOD, 124 of 192 (64.6%) stopped their postoperative exercise test for limiting dyspnea, 30 for leg pain, 29 for exhaustion, and 9 for other reasons. The rate of dyspnea as a limiting symptom was significantly higher in patients with postoperative EOD compared with those without it (Chi-square test=17.7; P<0.0001). The results of the comparison between patients with and without postoperative EOD are shown in Table 1. In particular, compared with the patients without postoperative EOD, the patients with postoperative EOD had a lower FEV1 (P=0.001), FVC (P=0.009), FEV1/FVC ratio (P=0.04), ppoFEV1 (P=0.0007), and ppoDLCO (P=0.04). They also showed a greater reduction in oxygen saturation during preoperative exercise (P<0.0001). Moreover, patients who were submitted to pneumonectomy desaturated more frequently than those submitted to lobectomy (P=0.04).
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The logistic regression analysis showed that a reduction in oxygen saturation during the preoperative exercise was the only significant predictor of postoperative EOD (regression coefficient: 0.22; P=0.0004).
Among the patients who experienced a preoperative reduction in oxygen saturation, the ratio of postoperative/preoperative percent reduction in oxygen saturation between rest and peak exercise (delta satO2 ratio) was calculated. Three groups were derived: group A, patients with a delta satO2 ratio
1; group B, patients with a delta satO2 ratio greater than 1 but lower than 3; group C, patients with a delta satO2 ratio
3. The three groups were compared in terms of reduction of total steps climbed between preoperative and postoperative stair-climbing test, by means of the analysis of variance (ANOVA) test. Groups A, B, and C showed a progressively greater reduction in steps climbed between preoperative and postoperative exercise test (32.9, 47.6 and 50.4, for group A, B and C, respectively). The difference between groups A and B (P=0.009), and that between groups A and C (P=0.01) was statistically significant.
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4. Discussion |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
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Supplemental oxygen in patients with lung disease and exercise hypoxemia has been shown to improve exercise tolerance and breathlessness [7–13], and the American Thoracic Society has endorsed its use in these patients. Even though no similar data are available in the literature concerning patients submitted to lung resection for lung cancer, it is reasonable assuming that, also in these patients, the correction of hypoxemia during exercise might lead to a more effective rehabilitation by permitting a greater degree of training than would otherwise be possible [14]. Moreover, oxygen dependence is perceived by patients as one of the most feared outcome after lung resection [15]. Hence, predicting such complication may also be useful for counseling surgical candidates.
The need of oxygen supplementation may go undetected without an exercise test, which will disclose the oxygen desaturation and the exertional dyspnea.
Thus, the objective of this study was to identify preoperatively the predictors of postoperative EOD below 90%. Patients at increased risk should all be submitted to a postoperative exercise test before discharge from the hospital to confirm or rule out EOD. We chose the stair-climbing test as a form of maximal exercise test, inasmuch as it is safe, economical, and widely applicable. Since stair climbing is a more stressful exercise than cycle or treadmill [16–18], it is a valid tool for detecting abnormalities in the oxygen transport system.
Oxygen saturation during the test was monitored by means of a portable pulse oximeter. This technique has been shown to accurately estimate changes in arterial saturation between rest and exercise [19].
Oxygen desaturation during exercise may be explained by one or a combination of the following factors: alveolar ventilation does not rise relatively as much as VO2; the cardiac output response to exercise may be subnormal (for coexisting ischemic heart disease or pulmonary hypertension), such that the mixed venous oxygen tension is very low, and, in the presence of ventilation/perfusion inequality, this will depress the arterial oxygen tension; exercise could lead to ventilation/perfusion mismatching (most probably due to the temporary accumulation of interstitial fluid in the lungs for an increased hydrostatic vascular pressure in both pulmonary artery and vein) [20].
In 55 of our patients (in all pneumonectomy candidates and in those patients with a ppoFEV1<50%), a lung perfusion scan was performed. In these patients, the percentage of perfused lung tissue removed during operation did not differ between those who had postoperative EOD and those who did not (29.3 versus 28.5%, respectively; P=0.8).
Some spirometric parameters (FEV1, FVC, FEV1/FVC ratio, ppoFEV1, and ppoDLCO) and the type of operation performed (pneumonectomy) resulted significantly associated with postoperative EOD at univariate analysis, showing that the ventilatory impairment due to obstructive lung disease, the diffusion limitation and the extent of the resection may all increase the risk to develop this complication. However, a fall in oxygen saturation during the preoperative exercise remained the only independent significant predictor of postoperative EOD below 90% after the effect of the other variables was controlled in a logistic regression analysis. The reduction of oxygen saturation during the preoperative stair-climbing test should be interpreted as a marker of some deficit in the oxygen transport system (mainly for ventilatory and cardiovascular reasons) that will be further exacerbated by the surgical stress.
In conclusion, we think that all the patients who showed a reduction in oxygen saturation during the preoperative exercise test should also perform a postoperative exercise test before discharge. Should EOD be confirmed, intermittent home oxygen therapy during physical rehabilitation and strenuous daily activities should be prescribed in order to improve the quality of life and facilitate recovery. These patients need to be frequently re-evaluated in order to verify improvements in their oxygen saturation status and for possible oxygen therapy discontinuation.
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References |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionReferences |
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This article has been cited by other articles:
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  A. Brunelli, M. Refai, F. Xiume, M. Salati, R. Marasco, V. Sciarra, L. Socci, and A. Sabbatini Oxygen desaturation during maximal stair-climbing test and postoperative complications after major lung resections Eur. J. Cardiothorac. Surg., January 1, 2008; 33(1): 77 - 82. [Abstract] [Full Text] [PDF]
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