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Anesth Analg 1999;88:28-33
© 1999 International Anesthesia Research Society

CARDIOVASCULAR ANESTHESIA

Lung Volume Reduction Surgery: Preoperative Functional Predictors for Postoperative Outcome

Edda M. Tschernko, MD*,{dagger}, Meinhard Kritzinger, MD{dagger}, Eva M. Gruber, MD{dagger}, Ursula Jantsch-Watzinger, MD{dagger}, Oliver Jandrasits, MD{dagger}, Peter Mares, MD{dagger}, Wilfried Wisser, MD{ddagger}, Walter Klepetko, MD{ddagger}, and Wolfram Haider, MD{dagger}

Departments of *Clinical Pharmacology, {dagger}Cardiothoracic Anesthesia & Critical Care Medicine, and {ddagger}Cardiothoracic Surgery, University of Vienna, Vienna, Austria

Address correspondence and reprint requests to Edda M. Tschernko, MD, Department of Cardiothoracic Anesthesia & Intensive Care, Vienna General Hospital, University of Vienna, A-1090 Vienna, Austria. Address e-mail to Edda.Tschernko{at}univie.ac.at


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 References
 
Approximately 20% of patients undergoing lung volume reduction surgery (LVRS) exhibit no functional improvement postoperatively. Therefore, we examined whether variables characterizing ventilatory mechanics before LVRS could serve as predictors for outcome. In 32 patients undergoing LVRS, lung function, dyspnea score, and ventilatory mechanics were assessed preoperatively and 3 mo after LVRS. Ventilatory mechanics were characterized by total resistive work of breathing (WOB), mean airway resistance (Rawm), and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn). Calculations of WOB, Rawm, and PEEPi,dyn were made from measurements of airflow, volume, and esophageal pressure. Preoperative PEEPi,dyn correlated well with the increase in forced expiratory volume percent predicted (r = 0.75; P < 0.0001) and the decrease in dyspnea score (r = -0.74; P < 0.0001) after LVRS. Rawm and WOB showed inferior correlation compared with PEEPi,dyn. The examination of distinct threshold values for WOB, Rawm, and PEEPi,dyn with respect to predicting improvement resulted in a sensitivity of 93% and specificity of 88% for a cutoff point of preoperative PEEPi,dyn >=5 cm H2O. Preoperative PEEPi,dyn correlated well with improvement in forced expiratory volume and dyspnea score after LVRS. Thus, preoperative assessment of PEEPi,dyn could improve risk to benefit stratification before LVRS.

Implications: We examined the preoperative ventilatory mechanics of patients with emphysema undergoing lung volume reduction surgery with respect to their value in predicting outcome. Preoperative intrinsic positive end-expiratory pressure correlated well with the increase in forced expiratory volume in 1 s after surgery. Thus, this variable seems promising for improved patient selection.


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 References
 
Lung volume reduction surgery (LVRS) is a new and promising treatment for severe emphysema (1–3). However, approximately 20% of patients do not show objective and subjective improvement after LVRS (2). Accordingly, it is important to develop variables that can identify patients who will or will not exhibit significant improvement with surgery. This seems especially important because LVRS is associated with a mortality of approximately 4% (2,3). There is still a lack of objective preoperative variables predicting postoperative outcome. Therefore, definition and validation of reliable variables for improved preoperative risk to benefit assessment and, consequently, improved patient selection, remains an important objective.

Ventilatory mechanics are severely impaired in patients suffering from emphysema (4,5), and LVRS leads to a significant improvement in many patients (6–8). Variables characterizing ventilatory mechanics, such as mean airway resistance (Rawm), total resistive work of breathing (WOB), and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn) relate to pathophysiological changes in patients suffering from emphysema (9). Therefore, these variables are likely to serve as functional predictors for outcome.

To define objective variables predicting outcome after LVRS, we assessed the utility of WOB, Rawm, and PEEPi,dyn, which were measured in 32 consecutive patients undergoing LVRS at our institution. Variables characterizing outcome were: (a) forced expiratory volume in 1 s (FEV1) 3 mo postoperatively and (b) dyspnea score 3 mo after LVRS. FEV1 was chosen to represent outcome because it correlates well with mortality in patients with end-stage emphysema (10). Dyspnea score was chosen to describe outcome because severe dyspnea leads to exercise limitation and impaired quality of life (11,12) and is therefore an important variable from the patient's point of view.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 References
 
Thirty-two consecutive patients undergoing LVRS (Table 1) were examined. The study was approved by the local review board, and all patients gave written, informed consent before LVRS. Significant functional limitations despite dedicated medical therapy were the basis for patient selection. Preoperative assessment included patient history, physical examination, standard pulmonary function testing, whole body plethysmography, arterial blood gas analysis, high-resolution computer tomography, quantitative nuclear lung perfusion/ventilation scan, and catheterization of the right heart. Severe general disease, ventilation/perfusion mismatch, and a mean pulmonary artery pressure >40 mm Hg at rest were regarded as exclusion criteria for LVRS. In addition, patients with bullous emphysema, i.e., air-filled space larger than one third of the hemithorax, were excluded from the study. The first 15 patients undergoing LVRS at our institution were also excluded from the study because it is likely that their results were influenced by the learning curves of the physicians. Of the 32 patients, 28 were treated topically and/or systemically with glucocorticoids. Baseline patient data are shown in Table 1.


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  		Table 1. Patient Baseline Data
 
Surgery was performed on both lungs using a video-endoscopic approach. The goal was to remove 20%–30% of the volume of each lung, concentrating on the most severely diseased portions of the lung. In patients who displayed a relatively homogeneous morphological distribution of the emphysematous process, portions of all lobes were excised.

Ventilatory mechanics were assessed 5–10 days before surgery and 3 mo (range 84–97 days) after LVRS. Ventilatory mechanics were assessed with the patient in an upright sitting position, and all patients breathed room air. Airflow ({image}) was measured by a flow sensor (Varflex Bicore CP-100 cardiopulmonary monitor; Bicore Monitoring Systems INC., Irvine, CA) connected to a tightly adjusted face mask. The fit of the face mask was evaluated by comparing inspiratory and expiratory tidal volumes (VT). A difference of <5% was regarded as sufficiently tight. VT was obtained by integration of the flow signal. Airway pressure (Paw) was measured through a catheter attached to the flow sensor, and the esophageal pressure (Pes) was measured by a nasogastric tube incorporating an esophageal balloon (13). The correct position of the balloon catheter was verified using the occlusion test (14). During the occlusion test, the subject performs maximal inspiratory efforts against the closed airway. In all patients, the ratio of {Delta}Pes/{Delta}Paw was close to unity, which indicates that the measurements of <Pes were a satisfactory index of the change in pleural surface pressure. The esophageal balloon and the flow sensor were connected to a portable monitor (Bicore CP-100 cardiopulmonary monitor) that provided a real-time display of {image}, volume (V), Paw, and Pes tracings. The accuracy of the measurements provided by this monitoring system has been found to be satisfactory (13). Additionally, the accuracy of measurements and calculations using the design of the present study has been evaluated in a previous study and has been found to be satisfactory (15).

Minute ventilation ({image}E) and breathing pattern, i.e., VT, respiratory frequency (f), the duration of inspiration (TI) and expiration (TE), and the duty cycle (inspiratory time divided by the time of the total breathing cycle = TI/TTOT) were analyzed based on the flow signal. Total resistive WOB values were provided directly by the monitor, which calculated the area under the Pes versus lung volume curve (16).

Chest wall compliance was not included in our WOB calculations because the patients breathed spontaneously during the entire measuring period.

PEEPi,dyn was measured, whereby PEEPi,dyn is equal to the absolute change in Pes from the onset of inspiratory effort to the onset of inspiratory {image} (17). During resting conditions, WOB, PEEPi,dyn, and Rawm were calculated from 39 breaths after excluding values that deviated from the mean by more than two standard deviations. These extreme values were most likely artifacts caused by coughing or swallowing.

The Baseline Dyspnea Index was used to evaluate dyspnea (18). This score was chosen for the evaluation of dyspnea because subjective, individual impairment is questioned, as is the magnitude of task and effort, which is differs among individuals. Dyspnea score was assessed preoperatively and 3 mo after surgery. For adequate comparison of improvement in dyspnea score, the preoperatively determined score was regarded as 100%, and the value determined 3 mo after surgery was compared with this 100% (normalized dyspnea score).

Spirometry and whole body plethysmography were performed in all patients preoperatively and 3 mo postoperatively, and the values compared with the reference value given by the European Community for Steel and Coal (19).

Statistical analysis was performed by using paired Student's t-tests. Preoperative spirometric values and mechanics were compared with values derived 3 mo after surgery and are expressed as mean ± SEM if not otherwise noted. P < 0.05 was considered the level of significance.

For all further calculations, preoperative values of FEV1 percent (%) predicted were regarded as 100%, and FEV1 % predicted 3 mo after surgery was expressed as a percentage of the preoperative value (normalized FEV1 % predicted). This approach was chosen to generate a comparable situation among patients because absolute changes in FEV1 in liters are difficult to interpret when they are not correlated with the age, gender, body weight, and height of a patient. Furthermore, an increase in FEV1 expressed in liters does not express the magnitude of improvement in relation to the preoperative situation.

To evaluate the accuracy of predicting outcome for different threshold values of a specific ventilatory parameter (viz.: PEEPi,dyn, WOB, Rawm), we defined a good result as a gain in normalized FEV1 % predicted of >=40% 3 mo after surgery. Preoperative values of PEEPi,dyn >=3, 4, 5, 6, and 7 cm H2O, preoperative Rawm >=10, 15, and 20 cm H2O · L-1 · s-1, and preoperative WOB >=1.25, 1.50, 1.75, and 2.00 J/L were then retrospectively tested in relation to postoperative improvement of normalized FEV1 % predicted and normalized dyspnea score.

Standard formulas were used to calculate the sensitivity (true positive/[true positives + false negatives]), specificity (true negatives/[true negatives + false positives]), positive predictive value (true positives/[true positives + false positives]), and negative predictive value (true negatives/[true negatives + false negatives]) of each index.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 References
 
Preoperatively ventilatory mechanics of all 32 patients enrolled in the study could be measured successfully, and none of the single measurements required more than 30 min. No complications associated with the measurements (swallowing of the esophageal balloon) were observed during or after all 62 measurements, which were performed in the course of the study.

Of the 32 patients, 30 were extubated within 24 h of surgery; none required reintubation. One patient could not be weaned and underwent successful lung transplantation 15 days after LVRS. The preoperative values for this patient were: 18.9% (0.89 L) FEV1 % predicted, 1.5 cm H2O PEEPi,dyn, 1.78 J/L WOB, and 10.8 cm H2O · L-1 · s-1 Rawm. Another patient remained extubated for 48 h but required mechanical ventilation on the third postoperative day because of the development of bilateral, panlobular pneumonia, resulting in adult respiratory distress syndrome. This patient died on the 10th postoperative day. The preoperative values for this patient were: 26.6% (1.09 L) FEV1 % predicted, 2.8 cm H2O PEEPi,dyn, 1.51 J/L WOB, and 8.7 cm H2O · L-1 · s-1 Rawm. The data presented were derived from the remaining 30 patients.

Preoperative FEV1 was 0.75 ± 0.04 L versus 1.18 ± 0.12 L (P < 0.005) 3 mo after LVRS. FEV1 % predicted showed comparable values: 25.4% ± 1.4% preoperatively versus 38.5% ± 4.2% (P < 0.005) 3 mo after LVRS. Of the 30 patients, 14 improved >40% in FEV1 % predicted after LVRS, whereas 2 of the 30 patients had worse FEV1 % predicted after the surgical procedure.

WOB decreased significantly (P < 0.005) after the surgical procedure (1.65 ± 0.10 vs 0.93 ± 0.08 J/L). Preoperative WOB per liter showed a correlation coefficient of r = 0.56 (P < 0.002) when correlated with normalized FEV1 % predicted 3 mo after LVRS (Fig. 1). The correlation coefficient of linear regression was r = -0.57 (P < 0.002) when correlating preoperative WOB with decrease in normalized dyspnea score (Fig. 1). Thereafter, cutoff points of 1.25, 1.50, 1.75, and 2 J/L were tested with respect to their accuracy in predicting a good surgical result, defined as an increase in FEV1 % predicted >=40%. Sensitivity, specificity, positive predictive value, and negative predictive value of the distinct cutoff points are shown in Table 2.



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  		Figure 1. Left, Circles represent single data pairs of patients. The x-value is preoperative total resistive work of breathing (WOB) and the y-value is normalized forced expiratory volume in 1 s percent predicted (FEV1 %) 3 mo after lung volume reduction surgery (LVRS). The horizontal dotted line represents an increase in normalized FEV1 % predicted of 40%. Circles above this line represent patients with an increase in FEV1 % predicted >40%, and circles below the horizontal dotted line represent patients with an increase in FEV1 % predicted <40%. The vertical dotted line separates patients with preoperative WOB <1.75 J/L from patients with preoperative WOB >1.75 J/L. Thus, the plot is divided into four parts containing the false-negative cases (left upper part), the true-positive cases (right upper part), the true-negative cases (left lower part), and the false-positive cases (right lower part) for a threshold value of WOB >= 1.75 J/L. The straight solid line represents the line of linear regression, r is the correlation coefficient, and P is the level of significance of the correlation. Right, Circles represent single data pairs of patients. The horizontal dotted line represents a decrease in dyspnea score of 40%. Circles above this line represent patients with a decrease in dyspnea score <40%, and circles below the horizontal dotted line represent patients with a decrease in dyspnea score >40%. The vertical dotted line separates patients with preoperative WOB <1.75 J/L from patients with preoperative WOB >1.75 J/L. Thus, the plot is divided into four parts containing the true-negative cases (left upper part), the false-positive cases (right upper part), the false-negative cases (left lower part), and the true-positive cases (right lower part) for a threshold value of WOB >= 1.75 J/L. The straight solid line represents the line of linear regression, r is the correlation coefficient, and P is the level of significance of the correlation.

 

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  		Table 2. Accuracy of Threshold Values in Predicting Outcome
 
A significant (P < 0.005) decrease in Rawm (17.3 ± 1.7 vs 9.7 ± 1.4 cm H2O · L-1 · s-1) was noted 3 mo after LVRS. Preoperative Rawm showed a correlation coefficient of r = 0.48 (P < 0.01) when correlated with normalized FEV1 % predicted (Fig. 2) and a correlation coefficient of r = -0.38 (P < 0.05) when correlated with the decrease in normalized dyspnea score 3 mo after surgery (Fig. 2). Rawm >=10 cm H2O · L-1 · s-1 was better in predicting outcome than Rawm >=15 and 20 cm H2O · L-1 · s-1 (Table 2).



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  		Figure 2. Left, Circles represent single data pairs of patients. Rawm = preoperative mean airway resistance, FEV1 % = forced expiratory volume in 1 s. The horizontal dotted line represents an increase in normalized FEV1 % predicted of 40% after lung volume reduction surgery (LVRS). Circles above this line represent patients with an increase >40%, and circles below this horizontal dotted line represent patients with an increase <40%. The vertical dotted line separates patients with preoperative Rawm <10 cm H2O · L-1 · s-1 from patients with preoperative Rawm >10 cm H2O · L-1 · s-1. Thus, the plot is divided into four parts containing the false-negative cases (left upper part), the true-positive cases (right upper part), the true-negative cases (left lower part), and the false-positive cases (right lower part) for a threshold value of Rawm >=10 cm H2O · L-1 · s-1. The straight solid line represents the line of linear regression, r is the correlation coefficient, and P is the level of significance. Right, Circles represent single data pairs of patients. The horizontal dotted line represents a decrease of dyspnea score of 40% after LVRS. Circles above this line represent patients with a decrease <40%, and circles below this horizontal dotted line represent patients with a decrease >40%. The vertical dotted line separates patients with preoperative Rawm <10 cm H2O · L-1 · s-1 from patients with preoperative Rawm >10 cm H2O · L-1 · s-1. Thus, the plot is divided into four parts containing the true-negative cases (left upper part), the false-positive cases (right upper part), the false-negative cases (left lower part), and the true-positive cases (right lower part) for a threshold value of Rawm >=10 cm H2O · L-1 · s-1. The straight solid line represents the line of linear regression, r is the correlation coefficient, and P is the level of significance.

 
Preoperative PEEPi,dyn was 6.3 ± 0.9 cm H2O, which decreased to 1.9 ± 0.3 cm H2O (P < 0.001) 3 mo after surgery. Single-patient data of changes in PEEPi,dyn are displayed in Figure 3. Correlation of preoperative PEEPi,dyn with normalized FEV1 % predicted 3 mo after LVRS showed a correlation coefficient of r = 0.75 (P < 0.0001) (Fig. 4). The correlation of preoperative PEEPi,dyn with normalized dyspnea score 3 mo after surgery resulted in a correlation coefficient of r = -0.74 (P < 0.0001) (Fig. 4). When testing different values of preoperative PEEPi,dyn as possible predictors for outcome, PEEPi,dyn >=5 cm H2O showed the best results, predicting outcome accurately in 27 of 30 patients. A threshold value of PEEPi,dyn >=5 cm H2O showed a sensitivity of 93%, a specificity of 88%, a positive predictive value of 87%, and a negative predictive value of 93% (Table 2).



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  		Figure 3. Shown are individual changes in dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn). On the y-axis single patient data of PEEPi,dyn are displayed. Each symbol represents an individual patient, and data pairs (preoperative value and postoperative value) are connected with a line. Mean PEEPi,dyn decreased significantly after surgery. *P < 0.001.

 


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  		Figure 4. Left, Circles represent single data pairs of patients. PEEPi,dyn = preoperative dynamic intrinsic end-expiratory pressure, FEV1 % = normalized forced expiratory volume in 1 s percent predicted. The horizontal dotted line represents an increase in FEV1 % predicted of 40% after lung volume reduction surgery (LVRS). Circles above this line represent patients with an increase in FEV1 % >40%, and circles below this horizontal dotted line represent patients with an increase in FEV1 % <40%. The vertical dotted line separates patients with preoperative PEEPi,dyn <5 cm H2O from patients with preoperative PEEPi,dyn >5 cm H2O. Thus, the plot is divided into four parts containing the false-negative cases (left upper part), the true-positive cases (right upper part), the true-negative cases (left lower part), and the false-positive cases (right lower part) for a threshold value of PEEPi,dyn >=5 cm H2O. The straight solid line represents the line of linear regression, r is the correlation coefficient, and P is the level of significance. Right, Circles represent single data pairs of patients. The horizontal dotted line represents a decrease of dyspnea score of 40% after LVRS. Circles above this line represent patients with a decrease <40%, and circles below this horizontal dotted line represent patients with a decrease >40%. The vertical dotted line separates patients with preoperative PEEPi,dyn <5 cm H2O from patients with preoperative PEEPi,dyn >5 cm H2O. Thus, the plot is divided into four parts containing the true-negative cases (left upper part), the false-positive cases (right upper part), the false-negative cases (left lower part), and the true-positive cases (right lower part) for a threshold value of PEEPi,dyn >=5 cm H2O. The straight solid line represents the line of linear regression, r is the correlation coefficient, and P is the level of significance.

 
Values characterizing breathing pattern, such as {image}E, f, and the duty cycle, were unchanged after LVRS. {image}E was 8.4 ± 0.7 L/min preoperatively versus 9.6 ± 1.0 L/min 3 mo after surgery, and f was 19.7 ± 1.2 breaths/min preoperatively versus 19.9 ± 1.0 breaths/min 3 mo postoperatively. Breathing pattern was assessed together with ventilatory mechanics (WOB, Rawm, PEEPi,dyn).


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
References
 
This study was performed to examine whether preoperative functional variables characterizing ventilatory mechanics could serve as predictors for outcome after LVRS. Three months after surgery, FEV1 was significantly increased; WOB, Rawm, and PEEPi,dyn were significantly decreased. A threshold value for preoperative PEEPi,dyn >=5 cm H2O resulted in the best combination of sensitivity (93%) and specificity (88%) of all examined threshold values when a good functional result was defined as an increase in normalized FEV1 % predicted >=40%.

A variable serving as preoperative predictor for outcome in daily clinical routine must meet several demands. The measurement of the variable must be safe, of considerably short duration, and accurate. In our study, we assessed ventilatory mechanics by using the Bicore CP-100 pulmonary monitor. No adverse events associated with the measurements were observed. Thus, we conclude that the measuring technique is safe. Furthermore, a maximum of 30 min was required for the setup and calibration of the equipment and the measurement. This seems to be reasonably time efficient and, thus, practical in daily clinical routine. Additionally, in a prestudy evaluation, we found the measurements and calculations of the device to be accurate (15).

A good surgical result was defined as an increase in FEV1 % predicted >=40%. This increase is more than twofold the effect of the conventional bronchodilator therapy (20). This very demanding definition was used to account for the mortality of approximately 4% associated with LVRS (3).

Preoperative WOB did not correlate well with the increase in normalized FEV1 % predicted (Fig. 1) or decrease in normalized dyspnea score 3 mo after LVRS (Fig. 1). Additionally, preoperative WOB was inferior in predicting outcome compared with preoperative PEEPi,dyn (Table 2).

WOB is significantly increased in many diseases of the lungs and the thorax and is therefore not specific for emphysema (16). LVRS candidates often suffer additionally from interstitial fibrotic scarring and long-term inflammation of the airways (21), which also leads to increased WOB but cannot be improved by LVRS. We assume that this is why preoperative WOB could not sufficiently predict outcome.

Our results demonstrated good correlation between preoperative PEEPi,dyn and the increase in normalized FEV1 % predicted and normalized dyspnea score 3 mo after surgery. PEEPi,dyn >=5 cm H2O was a threshold value predicting an increase in FEV1 % predicted >=40% with a sensitivity of 93% and a specificity of 88%.

When PEEPi,dyn is measured at comparable breathing pattern (22), which was the case in our patients, its magnitude is determined by (a) the magnitude of expiratory flow limitation and, thus, the magnitude of expiratory airway resistance (23); (b) the magnitude of reduction in elastic recoil of the lungs (23); and (c) the activity of expiratory muscles (24). Rawm has been shown to be significantly reduced after LVRS, probably by decompression of healthy lung tissue after removal of hyperinflated, destroyed tissue (8). Additionally, Scruiba et al. (6) found significantly improved elastic recoil after LVRS, and Benditt et al. (25) showed significant reduction of expiratory muscle activity during rest and exercise after LVRS. PEEPi,dyn is determined by the most important pathophysiological variables characterizing emphysema. All these variables undergo specific changes after LVRS (6,8,25). Thus, it is not surprising that the magnitude of preoperative PEEPi,dyn correlated well with the postoperative improvement in FEV1 (Fig. 4) and dyspnea score (Fig. 4).

When retrospectively evaluating specific threshold values of preoperative PEEPi,dyn as cutoff points for predicting outcome, we found a positive predictive value of 87% and a negative predictive value of 93% for preoperative PEEPi,dyn >=5 cm H2O. Nevertheless, it is necessary to undertake a further prospective study, to examine preoperative PEEPi,dyn >=5 cm H2O as a predictive parameter in a validation set of patients with emphysema undergoing LVRS to confirm these results.

The correlation of preoperative Rawm with postoperative increase in normalized FEV1 % predicted (Fig. 2) and decrease in dyspnea score was poor. Additionally, preoperative Rawm was inferior compared with preoperative PEEPi,dyn in predicting postoperative improvement (Table 2).

Ingenito et al. (26) showed in 29 subjects that inspiratory airway resistance correlated (r = -0.63) with a poor surgical result after LVRS. In contrast, patients presenting for LVRS with high expiratory airway resistance were likely to benefit from surgery. We evaluated the mean of inspiratory airway resistance and expiratory airway resistance in our patients. Therefore, we cannot rule out that pure inspiratory or pure expiratory airway resistance could serve more sufficiently as a predictor of outcome after LVRS than Rawm. However, the correlation coefficient determined for inspiratory airway resistance by Ingenito et al. (26) was r = -0.63, whereas the correlation coefficient for PEEPi,dyn in our study was r = 0.75. Because PEEPi,dyn is partially determined by expiratory flow resistance, our finding of the good predictive value of preoperative PEEPi,dyn is in line with the findings of Ingenito et al. (26).

In summary, our findings indicate that the magnitude of preoperative PEEPi,dyn is a good predictor for postoperative outcome after LVRS. From the observations made in 30 patients undergoing LVRS, we propose using a preoperative PEEPi,dyn >=5 cm H2O as a predictor for outcome. PEEPi,dyn >=5 cm H2O was associated with a high sensitivity and specificity in predicting an increase in normalized FEV1 % predicted >=40%, which represents more than twice the improvement expected from conventional bronchodilator therapy. Additionally, the measurement of PEEPi,dyn can be easily introduced into clinical routine. Nevertheless, a further prospective evaluation of the distinct cutoff points is necessary to confirm or adjust the presented results.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 

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Accepted for publication October 8, 1998.




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Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press