Killian’s descriptions regarding bronchoscopic examination of the proximal airways were critical in providing inspiration to his coworkers Von Eiken, Brunings, Seiffert, and Albrecht who worked on further development of the rigid bronchoscope. Storz and Wolf became the two pivotal companies that introduced newer technologies and newer versions of the rigid bronchoscope. On the other hand, the development of rigid bronchoscopy in the United States was brought about by Chevalier Jackson with his instrument maker, George Pilling. The next task at hand was the development of telescopic optics for bronchoscopy. This was accomplished by E. Broyles, who had trained under the mentorship of Dr. Jackson (1940). He then also went on to introduce the optical forceps in 1948 followed by fiber illumination techniques in 1962. The use of rigid bronchoscopy had declined since creation of the flexible bronchoscope until special tools for stent placement and neodymium-doped yttrium aluminum garnet (Nd:YAG) laser application was invented by J.-F. Dumon. The use of rigid bronchoscopy has since regained prominence, particularly for advanced therapeutic bronchoscopy [8].

The potential of fiber-optic imaging in bronchoscopy was first recognized by Shigeto Ikeda (1962), a thoracic surgeon at the National Cancer Center in Japan (Fig. 39.6). He approached the Machida Corporation to develop a flexible bronchoscope with a diameter of less than 6 mm. In 1964, the prototype device was developed, which since then has undergone numerous revisions. In 1966, the first useful device was presented at Copenhagen in 1966. This device comprising over 15,000 glass fibers was the first modern-day fiber-optic bronchoscope [9].

After the optical technology was incorporated, the next round of modifications involved the adoption of a working channel. This Machida flexible bronchoscope became available in 1968, which is known as the year of the “second revolution” in bronchoscopy. Researchers further revised the bronchoscope to make it more maneuverable at the tip that allows U-turn angulation for entry into the upper lobes. Olympus first came out with its model in 1970 with better imaging capabilities as well as ease of handling [9].

The first video bronchoscope developed by Asahi Pentax Corporation (1967) also involved significant contributions from Shigeto Ikeda [9]. Today, video bronchoscopy is an integral part of the practice of chest medicine as most ailments of the airways can be diagnosed, palliated, or sometimes cured by use of the flexible bronchoscope. Although removal of foreign bodies from the endobronchial tree was the initial application for the rigid bronchoscope, currently the majority of foreign bodies, even in the pediatric age group, are successfully removed with the flexible bronchoscope in a relatively noninvasive fashion [10].

Howard Anderson recognized the potential of accessing and sampling the lung parenchyma through the bronchoscope for histological analysis. After gaining some animal data with initial experiments, they reported their experience in obtaining bronchoscopic biopsies using a flexible forceps in 13 patients [11]. A subsequent larger series was published by Anderson and Fontana reporting data on 450 patients [12]. All biopsies performed by Anderson and colleagues were done using a flexible forceps passed through a rigid bronchoscope. These forceps were 60 cm in length and 7F in circumference. They also explained how they would engage a tiny peripheral bronchial carina with moderate pressure to obtain a small biopsy of the lung without causing a pneumothorax from pleural rupture. The rate of pneumothorax was 19% in the first 150 patients and 11% in the next 300 patients [12]. Though this technique of lung biopsy was developed and utilized through the rigid bronchoscope, it is now standard of care to use a flexible bronchoscope for this sampling procedure. Transbronchial lung biopsies are standard of care in the diagnostic work-up of a variety of lung diseases and are an inherent part of caring for lung transplant recipients [13, 14].

The idea of transbronchial needle aspiration (TBNA) through the rigid bronchoscope was first proposed by Eduardo Schieppati (1958). He proposed that this technique can be accomplished by passing a needle through a rigid bronchoscope to puncture the main carina and sample mediastinal lymph nodes [15]. This concept was furthered by the work of Oho and colleagues [16]. The first report of sampling paratracheal tumors and masses was published in 1978 by Ko-Pen Wang (Fig. 39.8) [17]. He successfully accomplished this technique via flexible bronchoscopy. He then further refined the technique by introducing a needle for histological specimen collection to help in diagnosing benign pathologies [18, 19]. Conventional TBNA (C-TBNA) which was commonly used in the 1980s and 1990s has paved the way for the development of endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) which uses ultrasound technology via a probe at the apex of the scope to perform TBNA under direct visualization with ultrasonic images.

The technique of delivering laser light with a wavelength of 1064 nm via a flexible quartz filament was reported by Lucien Toty and colleagues in 1981. They first reported the use of this Nd:YAG laser in the airways through a rigid bronchoscope [20]. This laser beam had the potential to coagulate or vaporize endobronchial lesions and abnormalities. The technique of using laser photo resection in patients with either malignant or benign lesions of the airway was further refined by J.-F. Dumon who also played a vital role in developing the techniques of airway stenting. He is considered the father of interventional pulmonology, and he propagated the use of endobronchial use of laser to bronchoscopists worldwide.

The year 1994 saw a newer mode of electrosurgical, noncontact, thermal ablation technique by using ionized argon gas (argon plasma). This pioneering modality was introduced by Grund and colleagues [21]. With this technique, 102 patients were treated endoscopically in 189 sessions with APC in the upper and lower gastrointestinal tract as well as in the respiratory system. Lesions treated were mainly malignant and benign tumors, diffuse hemorrhages of various origins and sites, tissue overgrowth after stent implantation, tissue remnants after endoscopic resections, and the conditioning of fistulas prior to fibrin sealing. APC was easy and effective in all cases via flexible bronchoscopy with minimal technical or other complications over standard electrocoagulation. Endobronchial APC currently offers the simplicity and low cost of an electrocoagulator with the noncontact approach of an Nd:YAG laser. The noncontact feature of APC allows rapid coagulation with minimal manipulation and mechanical trauma to the target tissue [22].

The very first stent implantation was accomplished by Trendelenburg and Bond for the treatment of central airway strictures [23, 24]. This technique has made rapid progress since 1965.

Montgomery designed the first T-tube with an external side limb made of silicone for tracheal stenosis [25]. J.-F. Dumon achieved a major breakthrough in airway stenting when he introduced a dedicated tracheobronchial prosthesis. This stent has a unique external surface with studs to preserve mucociliary action [26]. Since most pulmonologists in the United States are not trained in rigid bronchoscopy for stent placement, the utility of such stents has been limited. On the other hand, flexible bronchoscopy to place metallic stents is relatively easy but results in a significant amount of granulation tissue. This tissue reaction makes removal of these stents very challenging including possibility of airway laceration. Thus, their role is limited mainly to malignant processes, and they are the treatment of choice for bronchial dehiscence, especially after lung transplantation [27]. The ideal stent is one that is “easy to insert and remove, can be customized to fit the dimensions and shape of a stricture, reestablishes luminal patency by resisting compressive forces but is sufficiently elastic to conform to airway contours without causing ischemia or erosion into adjacent structures, is not prone to migration, biocompatible, nonirritating, and does not precipitate infection, promote granulation tissue, nor interferes with airway ciliary action necessary to clear secretions, and that is affordable” [28].

That ideal stent does not yet exist [28]. At present, highly specialized technology including three-dimensional printing with advanced radiographics is being employed to device stents specific for each patient’s individual airway anatomy [29].

Since 1986 when the first lung transplant was performed, about 50,000 transplants have been performed in the United States for end-stage lung diseases. The most common complications post-lung transplant are infection and rejection. Both these broad diagnostic categories cannot be narrowed upon without flexible bronchoscopy. Hence, the success of lung transplantation, however, cannot be imagined without the use of the flexible bronchoscope. This argument is supported by the study by Trulock and colleagues where they found a surprisingly high incidence of acute rejection in asymptomatic lung transplant recipients undergoing transbronchial biopsy [30]. The sensitivity of transbronchial lung biopsy was estimated at 72% for the diagnosis of acute rejection and 91% for the diagnosis of cytomegalovirus pneumonia. Surveillance bronchoscopy is performed in the first year after transplant in many lung transplant programs because the incidence of acute rejection resulting in graft dysfunction is highest in this period. Some others perform flexible bronchoscopy with transbronchial biopsies only when clinically indicated (i.e., drop in lung function or new radiographic abnormalities). Nevertheless, both approaches aim to detect subclinical, clinical acute cellular rejection and antibody-mediated rejection. Flexible bronchoscopy is also crucial in the diagnosis and management of airway complications after lung transplantation [31].

C-TBNA demonstrated the ability to access and sample mediastinal lymph nodes. However, the anatomy of the bronchial tree and associated vasculature makes direct visualization of structures quiet important, especially in the paratracheal regions and the hila. Ultrasound technology has made it possible to noninvasively assess most regions of the body. This concept led investigators to pursue real-time target visualization at the time of sampling. It was the pioneering work of Heinrich Becker that brought to fore the immense potential of applying ultrasound technology to the endobronchial region. This led to the development of EBUS of endobronchial ultrasound to guide sampling of mediastinal lymph nodes and parenchymal lesions [32]. Hurter and Hanrath first reported the usefulness of radial probe EBUS (RP-EBUS) in 74 patients with central lesions and 26 patients with parenchymal lesions in consecutive procedures [33]. Although RP-EBUS continues to play a pivotal role in the diagnosis of peripheral pulmonary lesions, a major limitation of RP-EBUS, however, is that after localizing the lesion, sampling is still performed in a blind fashion. Investigators have however worked on other technologies to localize pulmonary masses and use real-time sampling in addition to RP-EBUS. This limitation has paved the way for the development of the convex probe EBUS [34].

Convex probe ultrasound was developed as an attempt to utilize real-time ultrasound technology to sample mediastinal lymph nodes and lung lesions. The distal end of the EBUS bronchoscope has a larger diameter than a flexible bronchoscope, with an angulated forward view at a 30 degree inclination (Fig. 39.10). This is necessary for imaging the lymph nodes and lung lesions and anchoring the scope to the airway while the needle comes out of a slightly proximal opening. The field of bronchoscopy imported the concept of linear probe ultrasound endoscopes from gastroenterology, after they were developed to sample paraesophageal lesions under real-time guidance. Pedersen and colleagues first described the usefulness of linear EBUS in sampling mediastinal lesions in 1996 [35]. Kazuhiro Yasufuku and colleagues (Fig. 39.11) first demonstrated the high diagnostic yield of the convex probe EBUS (CP-EBUS) in sampling mediastinal lesions [36]. Both studies reported a sensitivity of 96% and specificity of 100% for distinguishing between malignant and nonmalignant lesions [37]. Currently, CP-EBUS has become standard of care for diagnosis and staging of lung cancer as well as the diagnostic work-up of sarcoidosis and interstitial lung diseases [38, 39]. As shown in the granuloma trial, CP-EBUS-TBNA alone has been shown to have a high diagnostic yield for sarcoidosis. The yield is even higher when transbronchial lung biopsies are performed to complement it [40]. Thus, CP-EBUS has almost replaced surgical mediastinoscopy with a less invasive option.