Tracheal Axis Research Articles

Perpendicular implantation of porcine trachea extracellular matrix for enhanced xenogeneic scaffold surface epithelialization in a canine model.

The availability of clinically applied medical materials in thoracic surgery remains insufficient, especially materials for treating tracheal defects. Herein, the potential of porcine extracellular matrix (P-ECM) as a new airway reconstruction material was explored by xenotransplanting it into a canine trachea. P-ECM was first transplanted into the buttocks of Narc Beagle dogs (n = 3) and its overall immuno-induced effects were evaluated. Subsequently, nine dogs underwent surgery to create a tracheal defect that was 1 × 2 cm. In group A, the P-ECM was implanted parallel to the tracheal axis (n = 3), whereas in group B the P-ECM was implanted perpendicular to the tracheal axis (n = 6). The grafts were periodically observed by bronchoscopy and evaluated postoperatively at 1 and 3 months through macroscopic and microscopic examinations. Immunosuppressants were not administered. Statistical evaluation was performed for Bronchoscopic stenosis rate, graft epithelialization rate, shrinkage rate and ECM live-implantation rate. No sign of P-ECM rejection was observed after its implantation in the buttocks. Bronchoscopic findings showed no improvement concerning stenosis in group A until 3 months after surgery; epithelialization of the graft site was not evident, and the ECM site appeared scarred and faded. In contrast, stenosis gradually improved in group B, with continuous epithelium within the host tissues and P-ECM. Histologically, the graft site contracted longitudinally and no epithelialization was observed in group A, whereas full epithelialization was observed on the P-ECM in group B. No sign of cartilage regeneration was confirmed in both groups. No statistically significant differences were found in bronchoscopic stenosis rate, shrinkage rate and ECM live-implantation rate, but graft epithelialization rate showed a statistically significant difference (G-A; sporadic (25%) 3, vs. G-B; full covered (100%) 3; p = 0.047). P-ECM can support full re-epithelialization without chondrocyte regeneration, with perpendicular implantation facilitating epithelialization of the ECM. Our results showed that our decellularized tracheal matrix holds clinical potential as a biological xenogeneic material for airway defect repair.

A quantitative interspecies comparison of the respiratory mucociliary clearance mechanism

Collectively coordinated ciliary activity propels the airway mucus, which lines the luminal surface of the vertebrate respiratory system, in cranial direction. Our contemporary understanding on how the quantitative characteristics of the metachronal wave field determines the resulting mucociliary transport is still limited, partly due to the sparse availability of quantitative observational data. We employed high-speed video reflection microscopy to image and quantitatively characterize the metachronal wave field as well as the mucociliary transport in excised bovine, porcine, ovine, lapine, turkey and ostrich samples. Image processing techniques were used to determine the ciliary beating frequency (CBF), the velocity and wavelength of the metachronal wave and the mucociliary transport velocity. The transport direction was found to strongly correlate with the mean wave propagation direction in all six species. The CBF yielded similar values (10–15 Hz) for all six species. Birds were found to exhibit higher transport speeds (130–260 upmum/s) than mammals (20–80 upmum/s). While the average transport direction significantly deviates from the tracheal long axis in mammals, no significant deviation was found in birds. The metachronal waves were found to propagate at about 4–8 times the speed of mucociliary transport in mammals, whereas in birds they propagate at about the transport speed. The mucociliary transport in birds is fast and roughly follows the TLA, whereas the transport is slower and proceeds along a left-handed spiral in mammals. The longer wavelengths and the lower ratio between the metachronal wave speed and the mucociliary transport speed provide evidence that the mucociliary clearance mechanism operates differently in birds than in mammals.

A Fatal Arterio-Tracheal Fistula Post-Tracheostomy: A Case Report in a Sub-Saharan Setting

Fatal bleeding in patients with tracheostomy is an uncommon incident, in the order of 0.1% to 1% of cases. It is secondary in 70% of cases to the innominate artery fistula in the tracheal lumen. The fistula is generally created after the necrosis of tracheal rings. The incriminated factors are the type of cannula used, the site of tracheal opening below the 3rd tracheal ring, tracheal infections and the proximity of the innominate artery to the tracheal axis. The outcome of this incident is fatal in most cases. We report the case of a 59-year-old patient with a tracheostomy on the 11th day of his admission to intensive care for severe head trauma secondary to a road accident. On the 22nd day of his admission, the occurrence of a cataclysmic and fatal haemorrhage through the tracheostomy tube evoked an arterio-tracheal fistula of the innominate artery.

Comparative Evaluation of Macintosh and Airtraq Laryngoscopes for Laryngeal View during Endotracheal Intubation: A Study Protocol

Background: Intubating trachea is a routine procedure for anaesthesiologists, but during surgeries, protecting the airway remains a challenge. Intubation failure in anaesthetic and emergency cases remains a big cause of mortality and morbidity. The Macintosh laryngoscope remains most widely used of various inventions and numerous advancements in the airway used for endotracheal intubation. Airtraq laryngoscope is a novel video laryngoscope which aids the procedure for intubation of patients with difficult or normal airways. Airtraq blade curvature and the precise internal arrangement of the optical components are made in such a way that enables visualization of the glottic field with minimal manipulation of the pharyngeal, oral and tracheal axis. This study aims to compare Airtraq and Macintosh Laryngoscope for Laryngeal view.
 Methods: This will be a prospective comparative randomised study that will include total 80 patients. Patients posted for surgery under general anaesthesia will be randomized into two groups (i.e. 40 in each groups): Group M-E patients will be intubated with Macintosh Endotracheal Intubation whereas Group A-E patients will be intubated with Airtraq Endotracheal Intubation. Patients will be evaluated for Ease of intubation, duration of induction, successful number of attempts and hemodynamic parameters. Data will be compiled and analysed with appropriate statistical programme.
 Expected Results: Significant results are expected to support that, Airtraq can be secured easily and with lesser number of attempts compared to Macintosh and duration of insertion is less.
 Conclusion: Intubation with Airtraq is easier in relation to intubation ease and duration compared to Macintosh with less post-operative complications.

A Standardised Approach to the Biomechanical Evaluation of Tracheal Grafts.

The ideal tracheal substitute must have biomechanical properties comparable to the native trachea, but currently there is no standardised approach to evaluating these properties. Here we propose a novel method for evaluating and comparing the properties of tracheal substitutes, thus systematising both measurement and data curation. This system was tested by comparing native rabbit tracheas to frozen and decellularised specimens and determining the histological characteristics of those specimens. We performed radial compression tests on the anteroposterior tracheal axis and longitudinal axial tensile tests with the specimens anastomosed to the jaw connected to a measuring system. All calculations and results were adjusted according to tracheal size, always using variables relative to the tracheal dimensions, thus permitting comparison of different sized organs. The biomechanical properties of the decellularised specimens were only slightly reduced compared to controls and significant in regard to the maximum stress withstood in the longitudinal axis (−0.246 MPa CI [−0.248, −0.145] MPa) and the energy stored per volume unit (−0.124 mJ·mm−3 CI [−0.195, −0.055] mJ·mm−3). The proposed method is suitable for the systematic characterisation of the biomechanical properties of different tracheal substitutes, regardless of the size or nature of the substitute, thus allowing for direct comparisons.

A Novel Classification of Parathyroid Glands and Their Preservation in Thyroidectomy

Introduction: Hypoparathyroidism is the most frequent complication after thyroidectomy and is caused by inadvertent gland injury, removal, or devascularization. To preserve the parathyroid effectively, we recorded the parathyroid glands based on their anatomic characteristics.1–2 To avoid hypoparathyroidism, the parathyroid glands should be identified and preserved in situ.3 In a few unusual circumstances, devascularized glands that cannot be preserved should be transplanted during surgery.4 However, various locations and blood vessels make the preservation of parathyroid glands difficult. Materials and Methods: Parathyroid glands were classified into three types, considering their blood supply and location.5 Type A: The unattached type, that is, the secure or thymus type—the parathyroid glands are located outside the thyroid gland and have an independent blood supply. They are mostly safe unless patients undergo central compartment neck dissection. Type B: The half-attached type B1. The parathyroid glands are located on the surface of the thyroid gland and have a clear blood supply. These vessels are independent of the thyroid gland, and it is easy to preserve the blood vessels of the parathyroid gland during thyroidectomy. B2. The parathyroid glands are situated on the surface of the thyroid. The blood supply of the parathyroid gland is partially from the thyroid gland or its communicating branches. When separated from the thyroid gland, the parathyroid glands change in color from light red to dark red, for which, decompression should be performed by making an incision. B3. The parathyroid glands are located on the surface of the thyroid and are often found on the lateral thyroid lobe, which is far from the tracheal axis. The blood supply is partially from the vessels supplying the thyroid gland, and these vessels are hard to preserve. However, there is an opportunity to try to preserve them as type B2. If the separation is ineffective, these glands will be considered type C and need to be transplanted. Type C: The completely attached type—the parathyroid glands are embedded within the thyroid and receive their blood supply directly from the thyroid gland. Therefore, it is difficult to preserve them in situ during total thyroidectomy. Results: All of parathyroid glands were confirmed histologically by frozen sections. Conclusions: Parathyroid glands can be classified into three types based on their locations and blood supply. The difficulty of preserving each type of parathyroid gland differed. Surgeons should use different surgical techniques to treat each type. Acknowledgments: This work was supported from the key program of health and family planning commission of Hubei province (Grant No. WJ2015MA003) and the young thyroid doctors' research projects supported by International Medical Foundation of China in 2015 (Grant No. 2016026). No competing financial interests exist. Runtime of video: 3 mins 39 secs

Airtraq(®) versus Macintosh laryngoscope: A comparative study in tracheal intubation.

Background:The curved laryngoscope blade described by Macintosh in 1943 remains the most widely used device to facilitate tracheal intubation. The Airtraq® (Prodol Meditec S.A, Vizcaya, Spain) is a new, single use, indirect laryngoscope introduced into clinical practice in 2005. It has wan exaggerated blade curvature with internal arrangement of optical lenses and a mechanism to prevent fogging of the distal lens. A high quality view of the glottis is provided without the need to align the oral, pharyngeal and tracheal axis. We evaluated Airtraq and Macintosh laryngoscopes for success rate of tracheal intubation, overall duration of successful intubation, optimization maneuvers, POGO (percentage of glottic opening) score, and ease of intubation.Materials and Methods:Patients were randomly allocated by computer-generated random table to one of the two groups, comprising 40 patients each, group I (Airtraq) and group II (Macintosh). After induction of general anesthesia, tracheal intubation was attempted with the Airtraq or the Macintosh laryngoscope as per group. Primary end points were overall success rate of tracheal intubation, overall duration of successful tracheal intubation, optimization maneuvers, POGO score and ease of intubation between the two groups.Results:We observed that Airtraq was better than the Macintosh laryngoscope as duration of successful intubation was shorter in Airtraq 18.15 seconds (±2.74) and in the Macintosh laryngoscope it was 32.72 seconds (±8.31) P < 0.001. POGO was also better in the Airtraq group 100% grade 1 versus 67.5% in the Macintosh group, P < 0.001. Ease of intubation was also better in the Airtraq group. It was easy in 97.5% versus 42.5% in the Macintosh group, P < 0.001.Conclusion:Both Airtraq and Macintosh laryngoscopes are equally effective in tracheal intubation in normal airways. Duration of successful tracheal intubation was shorter in the Airtraq group which was statistically significant.

Angiosarcoma of the thyroid in an old man

Background The angiosarcoma of the thyroid gland is a primary malignant highly aggressive tumor. It is classified as a malignant vascular thyroid lesion of mesenchymal origin. In addition to the neck and head, the majority of angiosarcomas also originate from the skin and soft tissues, or limbs of patients with lymphedema. Angiosarcoma of the thyroid is rare and the greatest incidence is witnessed near the Alps. It constitutes only 2-10% of malignant thyroid tumors in Switzerland, Austria and Northern Italy. The prevalence in the Alpine regions can be due probably to iodine deficiency with a long history of endemic goiter. It strikes in old age. There are cases in which the tumor occurs without a history of goiter, and it the occurrence is very unusual in non-alpine areas, so it seemed interesting to present a case involving this type. Due to the increase of the thyroid volume, often occurring in a short time, dyspnea is a frequent symptom, associated with deviation of the tracheal axis. From the macroscopic point of view, this tumor typically appears to be with big dimensions, with large areas of necrosis and hemorrhage. Microscopically, freely anastomosed channels are often associated with a papillary configuration having a pattern of predominant intraluminal growth; the nuclei of the epithelioid endothelial cells are large, vesicular, smooth-contoured, with a large basophilic or amphophylic nucleolus connected by chromatin strands to the nuclear membrane. Typical and atypical mitosis were found in large numbers; the growth pattern is usually highly invasive and tumor necrosis is very strong. Of fundamental importance is the peculiarity that tumor cells express vascular markers such as Factor VIII, CD 31 and CD 34. The distinction between angiosarcoma and anaplastic sarcomatoid carcinoma is difficult and the same expression of the angiosarcoma has been subject to dispute. Clinical history: most of these tumors appear as a poorly encapsulated and infiltrating mass, which tends to grow in the absence of pain. Local recurrence, even after complete excision, and metastasis are common. After diagnosis, patients often die quickly. This type of cancer typically metastasizes in the first instance at the level of regional lymph nodes and lung, in the late stages in the bone marrow. Multimodal treatment, a widely accepted approach, envisages surgery, radiotherapy and chemotherapy. The study was inspired by the observation of a case of thyroid hemangiosarcoma in a 71-year-old man with a history of goiter for twenty years, who decided to undergo an operation for the worsening of the dyspnea.

Airway Scope Versus Macintosh Laryngoscope in Patients With Simulated Limitation of Neck Movements

Tracheal intubation in patients with suspected neck injuries should achieve two contradicting goals-sufficient laryngeal exposure and the least cervical spine movement. Because the former involves displacements of the cervical vertebrae, intubation under immobilization is widely performed today to prevent exacerbation of spinal code injuries. The unique curving blade of the Airway Scope (AWS) is designed to fit the oropharyngeal anatomy. A camera at the tip of the blade displays the view of the larynx, but unlike the direct laryngoscope, it needs no line-of-sight of the oral, pharyngeal, and tracheal axis. Our purpose is to determine whether AWS could be a suitable airway device for the intubation of patients with potential neck injury. Thirty-six patients scheduled for surgery were randomly assigned to undergo intubation using either AWS or Macintosh laryngoscope (MLS). After general anesthetic induction, the patient's head was set in a neutral position, and an appropriately sized semi-rigid neck collar was placed. Measurements include intubation time, number of attempts, success rate, Cormack-Lehane classification, airway optimization maneuver, Intubation Difficulty Scale scores, and complications. Intubation time proved no statistical significance (mean ± SD, AWS, 62.9 seconds ± 26.0 seconds, MLS, 55.6 seconds ± 26.0 seconds; p = 0.42). AWS scored less in Cormack-Lehane classification (median [range], AWS I [I-I], MLS IIIa [I-IIIb]; p < 0.0001), required fewer additional airway optimization maneuvers (p = 0.0003), and scored less in Intubation Difficulty Scale scores (AWS 0 [0-1], MLS 2 [0-5]; p < 0.0001). In neck-immobilized patients using semi-rigid cervical collars, AWS improves laryngeal exposure and facilitates tracheal intubation. AWS may be a suitable intubation device for trauma patients.

The GlideScope for tracheal intubation in patients with grade IV modified Cormack and Lehane

The GlideScope for tracheal intubation in patients with grade IV modified Cormack and Lehane

Airway Scope and Macintosh Laryngoscope for Tracheal Intubation in Patients Lying on the Ground

Direct laryngoscopy of a patient lying on the ground is difficult because the intubator's head is far above the head of the patient, making alignment of the intubator's visual axis with the patient's tracheal axis difficult. The Airway Scope is a laryngoscope designed to facilitate tracheal intubation without requiring alignment of the oral, pharyngeal, and tracheal axes. We thus tested the hypothesis that intubation with the Airway Scope is faster than with the Macintosh laryngoscope in subjects lying on the ground. Adult surgical patients were enrolled. After anesthesia induction, direct laryngoscopy was performed and airway characteristics noted. Patients were randomly assigned to tracheal intubation by either the Airway Scope (n = 50) or the Macintosh laryngoscope (n = 50). The intubator performed tracheal intubation from a table positioned at the same height as that of the operating table, thus simulating intubating on the ground. An unblinded observer recorded overall intubation success rate, time required for intubation, the number of attempts required for successful intubation, and airway complications related to intubation. Of these, the primary end point was time required for intubation. Overall intubation success rates were 98% with the Airway Scope and 100% with the Macintosh laryngoscope. Intubation was 17 s faster with the Airway Scope (mean, 18 (SD, 4) seconds) versus the Macintosh laryngoscope (35 (16) seconds). The number of intubation attempts was similar with each device. The incidences of airway complications were similar, with no hypoxia (Spo(2) <95%) occurring in either group. Both the Airway Scope and the Macintosh laryngoscope offer high success rates in adequately prepared paralyzed patients lying supine at ground level in the hands of a skilled practitioner. However, the Airway Scope facilitated faster tracheal intubation.

Sequential rotation to insert a left double-lumen endotracheal tube using the GlideScope®

To the Editor: The GlideScope videolaryngoscope (GVL) (Verathon, Bothell, WA, USA) allows the glottic opening to be visualized easily. However, it poses difficulties when double-lumen endotracheal tubes (DLT) are advanced into the trachea. This suggests that the traditional method of advancing the DLT may be insufficient if used with the GVL. A combination of several factors can decrease the operator’s ability to manipulate this tube proficiently, including the complex shape of the DLT, the angulation of the GVL blade, and the indirect viewing of the airway. A main feature of the DLT is the presence of a concave distal and a concave proximal curvature. Under direct laryngoscopy, the conventional method of insertion entails advancing the tube with the distal curvature directed anteriorly. Once the bronchial tip passes the vocal cords, the DLT is rotated 90 counter clockwise, a rotation that facilitates the alignment of the bronchial tip with the left main bronchus. With the GVL, advancement of a single-lumen tube through the glottis may be difficult or impossible, because it tends to advance anteriorly and thus nearly perpendicular to the axis of the trachea. This difficulty can also arise during an attempt to advance a DLT with the GVL, because the distal concave curvature directs the tip of the bronchial lumen more anteriorly. Prior to its insertion, we pre-curve the distal 10-12 cm of the DLT approximately 60 using the specific DLT malleable stylet (Mallinckrodt, Mansfield, MA, USA) through the bronchial lumen (Figure 1A). After we obtain the glottic view with the GVL, our first goal is to advance the tube until the tip of the bronchial lumen reaches the vocal cords, allowing the tube to engage into the glottis (Figure 1B). Next, we gently remove the stylet, which increases both flexibility and maneuvrability to the DLT and then we perform the initial 180 rotation. This manoeuvre aligns the axis of the bronchial lumen with the patient’s tracheal axis, facilitating the insertion of the bronchial cuff past the vocal cords (Figure 1C). Once this is accomplished, we then use the tracheal tip as the reference mark to align the tube with the left main bronchus, which usually requires an additional 90 clockwise rotation. Finally, we advance the DLT until the proper depth of insertion is reached. Contrary to the conventional method of inserting the DLT where only its alignment with the main bronchus is considered, when using the GVL, the absent line-of-sight must be taken into account during the procedure. Therefore, we suggest aligning the DLT with the trachea first— not with the bronchus—to guarantee the insertion of the bronchial cuff into the trachea. While this is accomplished with the first rotation, the second rotation helps to align the bronchial tip with the axis of the bronchus and to move the tip away from the posterior wall of the trachea while advancing the tube until final depth. So far, we have successfully used this DLT sequential rotation in a dozen patients without complications. The GVL was used in two patients after a failed intubation with the conventional laryngoscope, and it was used in the remaining patients as a primary airway device after suspecting a potentially difficult direct laryngoscopy. All the intubations were accomplished on first attempt. Electronic supplementary material The online version of this article (doi:10.1007/s12630-009-9243-2) contains supplementary material, which is available to authorized users.

Dosisreduzierte 16-Schicht-Multidetektor-Spiralcomputertomographie bei Säuglingen und Kleinkindern mit bronchoskopischem Verdacht auf vaskulär bedingte Trachealstenosen - erste klinische Ergebnisse

To evaluate the diagnostic accuracy of contrast-enhanced dose-reduced 16-slice multidetector-row CT (MDCT) in newborns and infants with fiberoptic bronchoscopically suspected vascular-induced tracheal stenosis. 12 children (4 days to 3 years, 1.2 - 13.5 kg body weight) were examined using i. v. contrast-enhanced 16-slice MDCT (SOMATOM Sensation 16, Forchheim, Germany) without breath-hold and under sedation (11/12). All MDCTs were performed with a dose reduction. The beam collimation was 16 x 0.75 mm, except in the case of one child. MPRs along the tracheal axis in the x-, y- and z-directions and volume-rendering-reconstructions (VRTs) were calculated based on a secondary raw data set in addition to conventional axial slices. 2 radiologists used a three-point grade scale to evaluate the image quality, motion, and contrast media artifacts as well as the usefulness of the 2D- and 3D-reconstructions for determining the diagnosis. Statistical analysis was performed on the basis of a Kappa test. In all cases the cause of the fiberoptic bronchoscopically suspected tracheal stenosis was revealed: compression due to the brachiocephalic trunk (n = 7), double aortic arch (n = 2), lusorian artery (n = 1), vascular compression of the left main bronchus (n = 2). In 3 patients further thoracic anomalies, such as tracheobronchial (n = 2), and vascular (n = 2) and vertebral (n = 1) anomalies were found. The attenuation in the anomalous vessels was 307 +/- 140 HU. The image noise was 9.8 +/- 1.9 HU. The mean dose reduction was 82.7 +/- 3.2 % compared to a standard adult thoracic CT. All examinations were rated as diagnostically good (median 1, range 1, k = 1). 3D images did not show any stair artifacts (median 2, range 1 - 2, k = 1). The image noise was minor to moderate and hardly any motion artifacts were seen (median 1, range 1 - 2, k = 0.8). Contrast media artifacts were rated zero to minor (median 1.5, range 1 - 2, k = 0.676). MPRs (median 1, range 1, k = 1) and VRTs (median 1, range 1, k = 1) were found to be useful for diagnosis. Subsequent vascular surgery was performed on 8 patients. Contrast-enhanced dose-reduced 16-slice MDCT is effective for demonstrating the cause of fiberoptic bronchoscopically suspected vascular-induced tracheal stenosis even in very small and severely ill children despite the small contrast media amount and free breathing.

A computational study of glottal obliquity

Glottal motion is not always symmetric during phonation. The cycle phase of one vocal fold may differ from that of the other, creating a dynamic glottal center line oblique to the tracheal center line. This condition is called ‘‘obliquity’’ of the glottis. Intraglottal pressures for a range of obliquity angles were obtained using a finite difference computational technique for steady flow in static geometries. As an example, for a uniform glottal duct, obliquity of 20 deg (one side convergent, the other divergent), subglottal pressure of 7.8 cm H2O, and glottal diameter of 0.032 cm: (1) air pressures were significantly different between the two glottal walls (as large as approximately 24 pressures measured perpendicular to the tracheal axis, but less if measured perpendicular to the glottal duct, (2) pressure values were different in amount and even polarity from that expected for a uniform glottis with zero obliquity, and (3) there were significant pressure differences at glottal exit between the two sides. Aerodynamic equations for glottal flow need to be modified to account for obliquity. The computational pressure profiles will be compared to empirical results using a Plexiglas model (M5) of the larynx. [Work supported by NIH grant 1R01DC03577-01A1.]

Postintubation tracheoesophageal fistula: Surgical treatment of three cases

J Thorac Cardiovasc Surg 1998;116:518-9

Airway Management and Rigid Spine Syndrome

Airway Management and Rigid Spine Syndrome

A Modification of Retrograde Wire-Guided, Fiberoptic-Assisted Endotracheal Intubation in a Patient with Ankylosing Spondylitis

A Modification of Retrograde Wire-Guided, Fiberoptic-Assisted Endotracheal Intubation in a Patient with Ankylosing Spondylitis

Tensile stiffness of ovine tracheal wall

The epithelial folding that occurs during bronchoconstriction requires that the pressure on the muscle side of the folding membrane be greater than that on the lumen side. The pressure required for a given level of folding depends on the elastic properties of the tissue and on the geometry of the folding. To quantify the elastic properties, uniaxial tensile stiffness of the tracheal inner wall of nine sheep was measured in two directions: parallel to the tracheal axis and circumferentially. The tissue showed anisotropic behavior, being approximately three times stiffer longitudinally than circumferentially. Histological examination showed that collagen in the lamina propria was randomly arranged, whereas there were straight elastin fibers aligned with the tracheal axis. This observation could explain the observed elastic anisotropy. Mechanical removal of the epithelium had no effect on tensile stiffness. It was also found that the tissue was under tension in situ. When a strip was excised, its length decreased by > or = 30%. After allowing for the systematic errors inherent in this experiment, the in situ circumferential tensile stiffness is estimated to be > or = 20 kPa. If the equivalent tissue in the bronchioles has the same tensile stiffness as that in the trachea, the forces required to fold the membrane are significant at small transbronchial pressure differences and increase in the presence of membrane thickening such as that seen in asthma.

Effect of entrainment time on pulmonary deposition of cigarette smoke in dogs.

Chronic inhalation of tobacco smoke can produce a nonuniform pattern of lung disease, with apical (nondependent) areas affected more often and more severely than other lung regions. This localized tissue damage might be the result of uneven deposition of inhaled smoke aerosol. There is some evidence to suggest that the way in which an aerosol is inhaled can influence its deposition in the lung. This study sought to determine the effects of entrainment timing on the deposition of tobacco smoke in the lung. Anesthetized mechanically ventilated dogs (n = 14) inhaled 35-ml boluses of 14C-labeled mainstream cigarette smoke once per minute in either a supine or erect posture. Boluses were entrained at the start of inspiration (group 1) or at midinspiration (group 2). Lungs were removed, sectioned, and assayed for 14C. Group 1 lungs experienced deposition in regions distant from the tracheal axis, with peripheral lung units averaging twice the deposition of 14C as central units. Group 2 lungs had a more uniform 14C distribution pattern. Early smoke entrainment favored peripheral deposition. One explanation for this finding is that peripheral lung units may have shorter time constants, thus filling sooner and more completely than those located centrally.

Laryngotracheobronchial Foreign Bodies

A retrospective review was conducted on 46 cases of foreign body aspiration seen during 1 Muharram 1401H (8 November 1980) to 30 Dhu Al-Hijjah 1408H (12 August 1988) at the King Fahad Hofuf Hospita...