Original article
General thoracic
Minute Ventilation-to-Carbon Dioxide Output (V˙e/V˙co2) Slope Is the Strongest Predictor of Respiratory Complications and Death After Pulmonary Resection

Presented at the Poster Session of the Forty-eighth Annual Meeting of The Society of Thoracic Surgeons, Fort Lauderdale, FL, Jan 28–Feb 1, 2012.
https://doi.org/10.1016/j.athoracsur.2012.03.022Get rights and content

Background

This study assessed whether the minute ventilation-to-carbon dioxide output (V˙e/V˙co2) slope, a measure of ventilatory efficiency routinely measured during cardiopulmonary exercise testing (CPET), is an independent predictor of respiratory complications after major lung resections.

Methods

Prospective observational analysis was performed on 225 consecutive candidates after lobectomy (197 patients) or pneumonectomy (28 patients) from 2008 to 2010. Inoperability criteria were peak oxygen consumption (V˙o2) of less than 10 mL/kg/min in association with predicted postoperative forced expiratory volume in 1 second of less than 30% and diffusion capacity of the lung for carbon monoxide of less than 30%. All patients performed a symptom-limited CPET on cycle ergometer. Respiratory complications (30 days or in-hospital) were prospectively recorded: pneumonia, atelectasis requiring bronchoscopy, respiratory failure on mechanical ventilation exceeding 48 hours, adult respiratory distress syndrome, pulmonary edema, and pulmonary embolism. Univariable and multivariable regression analyses were used to identify independent predictors of respiratory complications.

Results

Cardiopulmonary morbidity and mortality rates were 23% (51 patients) and 2.2% (5 patients). The 25 patients with respiratory complications had a significantly higher V˙e/V˙co2 slope than those without complications (34.8 vs 30.9, p = 0.001). Peak V˙o2 was not associated with respiratory complications. Logistic regression and bootstrap analyses showed that, after adjusting for other baseline and perioperative variables, the strongest predictor of respiratory complications was V˙e/V˙co2 slope (regression coefficient, 0.09; bootstrap frequency, 89%; p = 0.004). Patients with a V˙e/V˙co2 slope exceeding 35 had a higher incidence of respiratory complications (22% vs 7.6%, p = 0.004) and mortality (7.2% vs. 0.6%, p = 0.01).

Conclusions

V˙e/V˙co2 slope is a better predictor of respiratory complications than peak V˙o2. This inexpensive and operator-independent variable should be considered in the clinical practice to refine operability selection criteria.

Section snippets

Patients and Methods

This was a prospective observational study of 225 consecutive candidates for lobectomy (197 patients) or pneumonectomy (28 patients) at our institution from 2008 to 2010. The study was approved by the local Institutional Review Board, and all patients gave their consent to participate in the institutional prospective database and use of their data for research and clinical purposes.

Patients were operated on by board-certified thoracic surgeons through a muscle-sparing, nerve-sparing lateral

Results

The characteristics of the study patients are reported in Table 1. The overall cardiopulmonary morbidity and mortality rates were 23% (51 cases) and 2.2% (5 cases). RCs were present in 25 patients (11%) and had a significantly higher V˙e/V˙co2 slope compared with those without complications (34.8 vs 30.9, p = 0.001). The 5 patients who died had a higher value of V˙e/V˙co2 slope than survivors (36.3 vs 31.2, p = 0.07). Unlike patients with RCs, patients with cardiac complications (mainly atrial

Comment

The CPET is increasingly used for stratifying the risk of lung resection candidates. A peak V˙o2 below 10 mL/kg/min or 35% predicted value has been indicated as a prohibitive threshold for major anatomic resection [1]. Although peakV˙o2 is certainly the most widely used variable, CPET provides several other direct or indirect indicators that change in response to incremental workloads. This not only allows assessment of over-all cardiopulmonary reserves, but also, in case of a limitation of

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