Introduction
Recent advances in the treatment of lung cancer include detection of early stage, small-sized lung cancers combined with minimally invasive and lung function-sparing surgery. Of note, the outcomes of segmentectomy have been reported to be comparable with those of lobectomy [1, 2]. For successful segmentectomy, the ability to identify boundaries between the resected segment and others is crucial. However, there are many variations of intersegmental vessels, and the boundaries are not clear; therefore, a simple trace of the intersegmental vessels is not possible.
As a result, various techniques for identification have been reported including labeling the target segment with a dye via the pulmonary artery, bronchus, or peripheral vein, or inflating the segment with oxygen or air into the bronchus via the surgical field or fiberoptic bronchoscope (FOB) using a high frequency jet ventilator [3–12]. However, many of these techniques contain problems or difficulties including the potential for an air embolism and requiring a darkened environment.
Recently, Oizumi et al. reported the use of multi-detector computed tomography (CT) for segmentectomy [12]. This resulted in successful identification in 98% of the patients scheduled for segmentectomy. However, this method requires time for a knot to be produced in the operative field, as well as facilities that have high-resolution CT. By using a manual jet ventilator (MJV), we were able to insufflate the target lung segment with oxygen, thereby allowing for simpler, safer, and clearer identification of boundaries.
Aim
In this study, we retrospectively investigated the efficacy of this novel technique for detection of an intra-segmental border during surgery.
Material and methods
Patients scheduled for lung segmentectomy or subsegmentectomy using MJV (MCS-3, NIPPON MEGACARE CORPORATION, Tokyo, Japan) for identification of the intersegmental plane in our hospital were enrolled between January 1, 2013 and December 31, 2017. We excluded cases where identification by MJV was not necessary. We identified patients’ characteristics including age, gender, height, body weight, and resected segments, availability of clear resection planes acquisition, and complications associated with MJV via patient medical records. We examined the relationship between success rate and patients’ characteristics or resected segments.
Manual jet ventilator
The procedure for detecting the border between segments using MJV was as follows. We inserted the FOB into the bronchus of the lung segment to be resected from a double lumen tracheal tube (Broncho-Cath, Covidien Japan). Next, we inserted and fitted the tip of the MJV into the FOB air supply port, and the pressure was set at 0.14–0.21 MPa, with manual insufflation using oxygen into the resected segment while checking the expansion of the segment from the surgical field by the endoscopic image. Once we identified a clear intersegmental plane (Photo 1), the FOB was removed and the surgeon proceeded with the surgery.
Questionnaire for surgeons
A subjective questionnaire was given to the 12 experienced surgeons who performed all of the procedures to compare the lung segment identification by MJV with other identification methods. The questionnaire included items related to clarity, simplicity, safety, shorter identification time, and shorter resection time. Each item was evaluated as very effective, effective, somewhat effective, or invalid.
Results
Pulmonary segmentectomy was identified in 199 cases. Eighteen cases were excluded because we could not determine whether MJV was performed. In 10 cases, identification by MJV was no longer needed because of bronchial obstruction by the tumor or changes to the surgical procedures. Finally, 171 cases were analyzed (Figure 1). Table I lists the characteristics of the 171 patients (mean ± SD). The success rates of identification for males and females were 85% and 93%, respectively (p = 0.09), and there were no statistically significant differences in identification of the pulmonary intersegmental plane during segmentectomy with respect to patient characteristics.
Table I
Patient characteristics (n = 171)
Table II and Figure 2 show segments or subsegments scheduled for resection (right upper lobes, 35; right lower lobes, 48; left upper lobes, 53; left lower lobes, 35 cases); these included 15 subsegment cases. Clear planes were obtained in 152 (89%) cases by MJV. In 19 cases, the resection borders could not be clearly identified in the following segments: right upper lobes in 10 cases (S1: 3, S2: 4, S1 + S2: 1, S1a + S2: 1, S1b + S2: 1), right lower lobe in 2 cases (S7, S9 + S10), left upper lobe in 4 cases (S1 + 2: 1, S3: 1, S1 + 2 + S3: 2), and left lower lobes in 3 cases (S6, S8 + S9 + S10, S9 + S10) (Table III, Figure 2). Successful identification was significantly lower in the right upper lobe (p = 0.0028). There were no complications associated with MJV.
Table II
Area scheduled for resection (n = 171)
Table III
Unclear identification cases (19/171)
Our subjective questionnaire was answered by 12 experienced surgeons who performed these procedures. All 12 responded that MJV was “very effective” or “effective” with respect to clarity, safety, shorter identification time, and shorter resection time. Furthermore, 11 surgeons answered “very effective” or “effective” with regard to simplicity, and 1 surgeon replied “somewhat effective.” None of the surgeons answered “invalid” for any items (Figure 3).
Discussion
The findings of this retrospective study revealed that a clear boundary was obtained in 89% of the patients who underwent MJV for planned pulmonary segmentectomy, whereas exact boundaries could not be identified in 11% of the cases. We also found that identification of the right upper lobes was difficult for segmentectomy. Additionally, surgeons preferred MJV via questionnaire (clarity, simplicity, safety, identification time, and resection time). These results suggest that MJV could be a safe and convenient procedure to identify the pulmonary intersegmental plane for segmentectomy.
There are many methods available for identification of lung segments. Sakamoto et al. used the temperature differences between the segments following ligation of the intersegmental vessels [3]; however, this technique has limitations as it is difficult to identify internal boundaries of the lung because only the external lung surface is examined using this method, making it difficult to determine in smaller incisions. Techniques using dyes such as methylene blue or indocyanine green have also been reported [4–7]. This method requires a dye to be injected directly into the resected bronchi [4, 5] or directly into the bronchial artery of the diseased segment to identify the target segments. Alternatively, the dye can be injected into the peripheral vein following ligation of the resected bronchial artery to identify the intended segments [6].
Zhang et al. reported that methylene blue is safer than indocyanine green because it results in a lower risk of liver damage and anaphylaxis and because the artery is softer and easier to pierce than the bronchus [4]; however, the procedure for dye injection is difficult as dye is injected directly into the surgical field over 1–2 min. Furthermore, this may change the volume of the segment and the dye may not spread consistently and evenly. Intravascular dye injection is easy to administer and results in small changes in the lung volume, and various studies have also reported the use of fluorescence [6, 7]; however, these methods require a dark operation room for the use of an infrared thoracoscopy system, and the observable time is only 160–270 s. Furthermore, if any dye leaks into other areas by accident, the identification process becomes difficult, which can result in a reported identification rate of 84.6% [6].
Oxygen or air can be used to directly identify target segments. This method can be used to identify deflated or inflated segments, and revisions to the surgical procedure can be performed by suction. Oxygen can be introduced via two methods: via a cannulation into the segmental bronchi directly from the surgery field, or insertion via the FOB into the bronchus from a double lumen tracheal tube. However, oxygen may be accidentally injected intravenously, resulting in an air embolism. Therefore, introducing oxygen directly using the FOB is safer.
Previous studies have reported the inflation of the lung using an FOB as well as the use of a high frequency jet ventilator (HFV) [8, 9]. Low flow oxygen rates (approximately 1–3 l/min) resulted in leaks from the gap of the FOB, and the segment failed to expand sufficiently. However, it is difficult to administer oxygen at a high flow rate due to sudden bolus changes. Similarly, HFV has been reported to cause sudden expansion of the segment by blowing air with HFV after insertion of an FOB, allowing for fine tuning of the pressures [9]. An HFV starting at a low pressure before the FOB insertion and followed by a gradual rise in pressure after reaching the target segment makes it difficult to fine tune the timing and duration of the oxygen supply.
Our technique uses MJV through the FOB to directly inflate the resected lung to identify the lung intersegmental plane. MJV is smaller than HFV, and it can be easily moved because it can be carried on the fiber light source device. Additionally, MJV can be used to easily adjust the inflation time as well as the amount of aeration in real time. Furthermore, a previous study reported that Kohn’s pores, which are traffic branches between alveoli, are closed between segments, preventing inflation of the next segment [10]. We were able to obtain clear intersegmental planes by MJV in 152 of 171 cases (89%), and the success rate was higher than those of previous studies that used a dye [6].
Finally, segmentectomy was possible in all 19 cases with unclear planes owing to a combination of identification methods by following vessels and using MJV. No complications were documented from MJV or FOB, such as bronchial damage, baro-trauma, or air embolism. Additionally, subjectively, all of our surgeons felt that MJV was safer, quicker, faster, and easier to help identify surgical margins, allowing for quicker identification of segmental planes, although other identifying methods were not used in our institute
There were some limitations to our study due to its retrospective nature. First, clear identification could not be achieved via MJV in 19 cases. Furthermore, 10 of these 19 cases were segments of the right upper lobe, and the success rate of identification was significantly low. These results may be due to the difficulty in induction of the FOB to the right upper lobe, especially, when the angle of the branch of the right upper lobe becomes steeper, the patient’s height is higher and the distance from the hilum to the branch of the right upper lobe is longer. In addition, it might be more difficult to insert the FOB due to the surgical procedure as the surgeon may shift, constrict, and rotate the bronchi during the operation.
