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GENERAL ARTICLES

Right- and Left-Sided Mallinckrodt Double-Lumen Tubes Have Identical Clinical Performance

From the Harvard Medical School, Department of Anesthesia and Critical Care, Massachusetts General Hospital, Boston, Massachusetts.

Address correspondence and reprint requests to Warren S. Sandberg, MD, PhD, Department of Anesthesia and Critical Care, Massachusetts General Hospital, 55 Fruit St., Jackson 4, Boston, MA 02114. Address e-mail to wsandberg{at}partners.org.

	Abstract

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BACKGROUND: Left-sided double-lumen tubes are perceived to be safer than right-sided tubes, because they may be less prone to malposition. If this is true, then the incidence and severity of hypoxemia, hypercapnea, and high airway pressures should be higher for right-sided tubes during thoracic surgery than for left-sided tubes.

METHODS: We retrospectively reviewed thoracic surgical anesthetics between April 15, 2003, and December 31, 2004, using an automated anesthesia information management system. The system automatically records pulse oximetry, end-tidal carbon dioxide, and peak inspiratory pressure data every 30 s. Side of surgery and double-lumen tube placement are also documented. We compared the frequency of right- and left-sided Mallinckrodt tube use by thoracic anesthesiologists. Next, we examined the incidence, duration, and severity of hypoxemia (Spo₂ <90%), hypercapnea (Etco₂ >45 mm Hg) and high airway pressures (peak inspiratory pressure >35 cm H₂O) for lung and chest wall surgery patients. Group counts and means were compared by standard statistical methods.

RESULTS: Right- (n = 241) and left- (n = 450) sided tubes were almost exclusively used on the side contralateral to surgery. There were no differences in the incidence or duration of hypoxemia, hypercarbia, or high airway pressures. There was a small but significant increase in Etco₂ for patients having left lung ventilation.

CONCLUSIONS: The supposition that left-sided double-lumen tubes are safer than right-sided tubes when intraoperative hypoxemia, hypercapnea, and high airway pressures are used as criteria for safety is not supported by our data comparing the two types of tubes from one manufacturer.

	Introduction

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Double-lumen tubes (DLTs) are often used to achieve lung isolation for a variety of procedures, particularly during thoracic surgery. Placement and maintenance of DLTs is a part of the subspecialty education in thoracic anesthesiology because it requires special skills such as fiberoptic bronchoscopy.1

Left-sided DLTs are perceived to be safer than right-sided DLTs (Fig. 1), because they may be less prone to malpositions during one-lung ventilation (OLV).2 Although studies with small groups of patients have indicated that right-sided DLTs can be used without an increased risk of right upper lobe collapse, these same studies have also suggested that right-sided DLTs might be associated with more frequent malpositions.1,3,4 These considerations have led some authors to prefer left-sided DLTs almost exclusively.5 However, other work has shown that right- and left-sided DLTs perform with similar complication rates.6

View larger version (61K): [in this window] [in a new window]   Figure 1. Examples of the various endobronchial cuff designs developed to achieve effective right-lung ventilation that includes the right upper lobe for right-sided double-lumen tubes. From left to right, the manufacturers are: Portex, Mallinckrodt (used in this study) and Sheridan. Each design considers that, in the typical adult, the right upper lobe bronchus arises within a few millimeters of the carina.

In fact, it might appear to be more difficult to maintain the proper location of a right-sided DLT simply based on anatomic considerations, because the orifice of the right upper lobe bronchus attaches to the right mainstem bronchus at a level that is within a few millimeters of the carina. Thus, to establish reliable OLV and at the same time achieve adequate right upper lobe ventilation, specialized endobronchial cuff designs have been used by the manufacturers of right-sided DLTs. Examples of such designs are shown in Figure 1. Each of these cuff designs has its own relative merits, but in each case, optimal lung isolation and right upper lobe ventilation depends on maintenance of the tube at an optimal insertion depth whose range is only a few millimeters, while at the same time avoiding tube rotation. In contrast, left-sided DLTs can have their endobronchial cuffs placed in the relatively long left mainstem bronchus that terminates with a simple bifurcation, making these tubes relatively insensitive to translation or rotation.

Thus, it would seem simpler, and perhaps more prudent, to favor the use of left-sided DLTs whenever possible. However, not all patients can have a left endobronchial intubation.7 Even when left endobronchial intubation is possible, it may not be desirable from a surgical perspective. Furthermore, even left-sided DLTs have significant differences in cuff geometry both among vendors and even among examples of the same tube from the same vendor.8 Thus, there remains a place for right-sided DLTs, and anesthesiologists must be familiar with their use and performance characteristics.

At our institution, we achieve OLV with a Mallinckrodt DLT placed to the side opposite the surgery. We therefore hypothesized that, if right-sided DLTs are more prone to clinically significant malposition in broad use, the incidence and severity of hypoxemia, hypercapnea, and high airway pressures would be higher in a large group of patients receiving OLV via right-sided tubes during thoracic surgery than in a similar group receiving OLV via left-sided tubes. We reasoned that evidence of performance differences in hypoxemia, hypercapnea, and high airway pressures would be present in the anesthesia record, anticipating that departures from desirable norms would be captured by monitors and automatically stored by our computerized anesthesia information management system (AIMS), even if anesthesiologists quickly corrected the problem giving the out-of-norm value. We tested our hypothesis by retrospectively examining the performance characteristics of a large number of endotracheal DLTs used by a group of anesthesia providers who regularly place both right- and left-sided DLTs, that is, frequent users of DLTs.

	METHODS

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This study was approved by the Massachusetts General Hospital Human Research Committee (Massachusetts General Hospital, Boston, MA). We conducted a retrospective review of all patients who underwent DLT placement by our thoracic anesthesia service between April 15, 2003, and December 31, 2004. We restricted the study to those patients having chest wall or lung surgery, as described below.

DLTs were placed by residents working under the medical supervision of thoracic specialty attending anesthesiologists. We provide a supervision ratio of one attending anesthesiologist for two thoracic surgical operating rooms (ORs). Thus, although the attending anesthesiologist is immediately available, they are not continuously in the OR with a single resident. Accordingly, our practice is to encourage the independent, active management of DLTs by residents, including frequent bronchoscopic examinations and adjustments to tube position as needed—either with or without direct supervision by the attending anesthesiologist. Our standard practice is to confirm proper endobronchial placement immediately after intubation by physical examination and fiberoptic bronchoscopy. Proper endobronchial intubation, DLT insertion depth, and engagement of the right upper lobe mainstem bronchus (where applicable) are reconfirmed by fiberoptic bronchoscopy after moving the patient to the lateral decubitus position.

The specific ventilatory management strategy was neither controlled for nor recorded in this study. At the time of the study, the anesthesia machines in our thoracic ORs were equipped only with volume-cycled ventilators. The general strategy used by our thoracic anesthesia service was to use volume-cycled ventilation, with the inspiratory flow rate, set tidal volume, and I:E ratio selected to achieve adequate ventilation with peak inspiratory pressures (PIP) less than 22 cm H₂O (a number widely believed to minimize the chance of barotrauma). Finally, the use of continuous positive airway pressure to the nondependent lung or the use of positive end-expiratory pressure was rare, comprising <5% of cases, but neither intervention was routinely noted in our AIMS.

We tabulated the incidence of epidural analgesia. Although the management of the catheter was not standardized, it is our institutional custom to use concentrated local anesthetic (2% lidocaine or 0.5% bupivacaine, both with epinephrine) in epidurals placed for thoracic surgery. The infusions are started at the beginning of the surgery.

All anesthetics were documented using an automated AIMS, which was fully implemented in our ORs. The AIMS contains a computer database of every anesthetic administered since the inception of the system at our institution and automatically records oxygen saturation (Spo₂), end-tidal (Etco₂), and PIP every 30 s for each case. DLT placement is documented via menu choices that force the user to record left- versus right-sided tube use. Side of surgery was also obtained for the purposes of our study. The study population included all surgical patients in the OR whose data were recorded using the AIMS database and who received right- or left-sided endobronchial intubation by our thoracic anesthesia service. The data extracted from the AIMS included the case date and ID (a unique number assigned to each case), hospital assigned medical record number, patient age, sex and ASA physical status classification, OR number, surgical procedure performed, identity of the attending anesthesiologist, DLT side and size, all text comments pertaining to airway management, presence or absence of an epidural catheter, and finally Spo₂, ETco₂, and airway pressure data for the entire duration of the case.

Case ID data were recorded to ensure that each case identified was unique. Case ID and medical record numbers were stripped from the data once a unique set of cases was obtained. However, date and case description information were retained. The case descriptions were used to select only those cases in which a DLT was used to achieve lung isolation for lung parenchymal, pleural, or chest wall surgery. Lung transplants, bilateral thoractomies, and tracheal surgery cases were excluded.

The AIMS used by our hospital stores information in a relational database accessible via structured query language. To obtain the data required for this study, a query was developed to examine the physiologic and airway monitoring data in each thoracic anesthesia case where a DLT comment was recorded. The physiologic and airway data were examined from the timestamp entry of any comment pertaining to DLT placement to the timestamp associated with any of the following comments: reinstitution of bilateral ventilation, end of surgery, or extubation. If none of these comments was present in the AIMS, we examined the data until the patient departed the OR.

We estimated the fraction of DLT cases captured by our query by selecting a uniform sample of days from the AIMS DLT results. We then manually searched the OR schedule and medical records for these days for any additional DLT cases not flagged by triggering comments in the AIMS data. We also performed a manual comparison of the data extracted by our query with the anesthesia records from 5% of the cases randomly selected from the study group to ensure the accuracy of our data.

The identities of individual anesthesia providers were not recorded in the final dataset. Instead, DLTs placed in the ORs used by the thoracic anesthesia service were deemed to have been managed by a thoracic anesthesiologist for the purpose of case finding. Review of the cases before the final analysis revealed that 97% of the DLTs in the dataset were placed under the supervision of a member of our thoracic anesthesia service. We then stripped the identities of individual providers from the data.

Once the AIMS data query had been performed, we compared the frequency of right- and left-sided DLT use by our thoracic anesthesiologists. Next, we examined the physiologic data to determine the incidence, duration, and severity of episodes of hypoxemia (Spo₂ <90%), hypercapnea (Etco₂ >45 mm Hg), and high airway pressures (PIP >35 cm H₂O) for lung and chest wall surgery patients receiving OLV via right- versus left-sided DLTs. For an episode of hypoxemia, hypercapnea or high airway pressure to be included in our tabulation, it needed to last a minimum of 180 s (3 min). These criteria were chosen in advance of performing the data queries.

The data were tabulated in Microsoft Excel (Redmond, WA), and statistical analysis was performed using the JMP statistical software package (Cary, NC). All comparisons of DLT performance were planned in advance. We compared continuous data using Student’s t-test. Categorical data were compared using ² tests. In all tests of significance, a P value of <0.05 was considered to be significant.

	RESULTS

Top Abstract Introduction METHODS RESULTS DISCUSSION REFERENCES

 
We found 691 cases having OLV for chest wall or lung surgery and for which there was a comment pertaining to DLT placement that would have flagged the case for inclusion in our dataset. Manual validation of the AIMS structured query language search result indicated that our search routine captured 94% of DLT placements on the thoracic anesthesia service, so the sample is likely to be representative of overall performance among frequent DLT users.

Table 1 shows the summary demographic data for our patients, divided by whether a right- or left-sided DLT was used. The two groups are comparable with respect to sex ratio, age, and ASA physical status classification. Table 2 shows the procedural characteristics for patients receiving right- and left-sided DLTs. The groups are comparable with respect to procedure length, the use of epidural analgesia, and the ratio of minimally invasive to open thoracotomy procedures. Compared with the number of thoracotomies on each side, there were relatively more left than right pneumonectomies. The size of the Mallinckrodt DLT used was recorded in 590 of the 691 cases (79%) and these data are shown in Table 3. The distributions of sizes used for right versus left DLTs are not statistically significantly different from each other.

Data collection for Spo₂, Etco₂, and airway pressures ran from the timestamp entry of any comment pertaining to DLT placement to the timestamp associated with any of the following stopping conditions: reinstitution of bilateral ventilation (62% of cases), end of surgery (21% of cases), extubation (1% of cases), or until the patient departed the OR (16% of cases).

Table 4 shows our results for Mallinckrodt DLT performance under everyday usage conditions by a teaching thoracic anesthesia service. Right- and left-sided tubes were almost exclusively used on the side contralateral to the surgical site with ipsilateral placement, occurring in only 40 of 691 instances (or <6% of all cases). In our sample, right-sided surgery (422 cases) occurred much more often than left-sided surgery (269 cases) at a rate which is consistent with the uneven distribution of lung cancers that favors right-sided lesions.9

There were no statistically significant differences in the incidence or duration of hypoxemia (Spo₂ <90%), hypercapnea (Etco₂ >45 mm Hg), or high airway pressures (PIP >35 cm H₂O) between left- and right-sided DLTs. There was a small but statistically significant increase in Etco₂ for patients having left lung ventilation.

	DISCUSSION

Top Abstract Introduction METHODS RESULTS DISCUSSION REFERENCES

 
We used an AIMS database to perform a retrospective study comparing the intraoperative performance of right- and left-sided Mallinckrodt DLTs in the hands of resident/attending thoracic anesthesiologist teams during lung isolation. The routine use of right-sided DLTs has been discouraged for a variety of reasons, including their apparently lower "margin of safety,"2 and the perception that they are difficult to place and maintain, requiring personnel with specialized skills, such as advanced bronchoscopy.10 We note here that the typical coverage ratio of attending staff to residents in our study was 1:2, meaning that the right-sided DLT was "maintained" by a resident who shared the expert (i.e., attending) resource with another OR.

Given the ongoing reluctance to use right-sided DLTs in much of the anesthesia community, our finding that the oxygenation, ventilation, and airway pressure performance of right- and left-sided DLTs is indistinguishable under routine practice conditions in a large cohort provides useful new information supporting the routine use of right-sided tubes. However, this study was unable to evaluate intraoperative problems related to either initial difficulty of positioning right-sided DLTs or the subsequent need for repositioning, compared with left-sided DLTs. In our experience though, the initial positioning only takes an extra minute with the bronchoscope, consistent with published studies,4 and intraoperative malpositions are rare, as the right-sided tube is almost always contralateral to the side of surgery and thus protected from accidental dislodgement.

Our study also does have the limitation of being retrospective. This limits our ability to control for potential differences in the way patients were managed depending on the tube type (such as differences in ventilatory and anesthetic management), or to ensure that the patient groups and the distribution of the types of surgeries were matched between the right- and left-sided DLT groups. All of these factors that could not be controlled because of the retrospective nature of the study are potential sources of bias that could have influenced our results. In the following paragraphs, we will attempt to address these considerations.

The use of a dedicated team of thoracic anesthesiologists engendered a consistent pattern of anesthetic management. Decisions about ventilation and anesthesia were made without reference to the type of DLT in use. As described in the Methods section, we used volume cycled ventilation with an elastic limit for PIP. Positive end-expiratory pressure and continuous positive airway pressure were used only rarely. Most importantly, there is a consistent practice of "intubate the bronchus opposite the site of surgery," as demonstrated in Table 4. Choice of tube size was apparently unaffected by whether a right- or left-sided DLT was used, as the distributions of sizes used were indistinguishable (Table 3).

We have included information about patient characteristics, analgesic strategies, and the distribution of surgical procedures to demonstrate the similarity of the right- and left-sided DLT groups. Patient characteristics in Table 1 indicate that the two groups were comparable on the axes for which we have information. Surgical and analgesic characteristics presented in Table 2 again indicate that the right- and left-sided DLT groups were indistinguishable on the basis of the available data. Epidural catheters were placed in 65% of the cases included in our study (left-sided DLTs 63% of the time and right-sided DLTs 68% of the time, although this difference was not statistically significant).

Our results indicate that we missed some cases in which a DLT was used, but for which no DLT comment was made in the chart, and this could represent a source of bias. However, if one assumes that the absence of such documentation occurs with the same frequency for both right and left-sided DLTs, then our data are a representative sample of all DLT placements for chest wall and lung surgery.

A final criticism of retrospective studies is the strong possibility of selection bias influencing the result. We attempted to protect against this bias by including all cases that met our predetermined inclusion criteria of all DLT placements for lung parenchymal, pleural, or chest wall surgery. There is also a possibility that preconceptions will influence the way cases are identified and the way data are handled, but here the use of automatic data collection with an AIMS helps protect against such bias. We used an automatic query of the entire cohort of patients to obtain the performance data, rather than a manual case-finding strategy, which again protects against selection bias. Furthermore, the data are derived from routine clinical practice, giving our result real-world validity by eliminating potential biases introduced by observation.

We believe that our data are robust and accurate, as the primary data were collected automatically and completely by the AIMS. Multiple prior investigations indicate that automated records have less missing data and are better reflections of monitor output than hand-written records.11–15 This is particularly true during busy periods, such as would be the case if the anesthesiologists were attending to a problem with the DLT. AIMS also record artifacts, but any errors due to artifact would be uniformly distributed between right and left-sided DLT cases.

Our study can also be criticized for not having recorded the identities of the anesthesiologists, so that DLT performance differences could definitely be ascribed to individual thoracic anesthesia specialists. However, our department uses a delineated team system, and the thoracic anesthesia service covers its ORs with attending thoracic subspecialist anesthesiologists. Personnel substitutions of nonthoracic anesthesiologists are rarely, if ever, made on this service, and this was reflected in our finding that 97% of the DLT placements in our study were medically supervised by a thoracic anesthesiologist.

Overall, we did not detect any differences in the performance of right- versus left-sided Mallinckrodt DLTs. One could ask "what are the smallest performance differences that could be detected given the sample sizes and variabilities for the various comparisons shown in Table 4?" Given the variability in the data and our sample sizes, we would have been able to detect 3.5 min differences in the mean duration of desaturation, hypercarbia, or high airway pressures, a 2% difference in the depth of desaturation, and a 1 cm H₂O difference in peak airway pressures, with β = 0.8 and = 0.05. Thus, there is sufficient power in our samples to detect small performance differences. The small, but statistically significant, difference detected in Etco₂ with left-lung ventilation was most likely a reflection of the impact of a smaller lung volume on gas exchange mechanics.

In conclusion, the supposition that left-sided DLTs are safer than right-sided DLTs when intraoperative hypoxemia, hypercapnea, and high airway pressures are used as criteria and when these tubes are used by frequent users is not supported by our data.

	Footnotes

 
Accepted for publication February 1, 2008.

	REFERENCES

Top Abstract Introduction METHODS RESULTS DISCUSSION REFERENCES

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ehrenfeld, J. M. Articles by Sandberg, W. S. Search for Related Content PubMed PubMed Citation Articles by Ehrenfeld, J. M. Articles by Sandberg, W. S.