Supplemental oxygen requirement after tonsillectomy in children >3 years of age.

INTRODUCTION: The indications for postoperative admission after tonsillectomy in children >3 years of age are less well defined than for children <3 years old, and typically include severe obstructive sleep apnea (OSA), obesity, comorbidities, or behavioral factors. Inpatient care after tonsillectomy typically consists of respiratory monitoring and support, as respiratory compromise is the most common complication after pediatric tonsillectomy. We aim to evaluate risk factors associated with postoperative oxygen supplementation and to identify high risk populations within the admitted population who use additional resources or require additional interventions. METHODS: Retrospective chart review of patients between the ages of 3 and 18 years old who underwent tonsillectomy by four surgeons at a tertiary care children's hospital was performed. Data including demographics, comorbidities, surgical intervention, pre- and postoperative AHI, admission, postoperative oxygen requirement, and postoperative complications was collected and analyzed. RESULTS: There were 401 patients included in the analysis. Of the patients in this study, 65.59% were male, 43.39% were Latino, and 53.87% were ages 3 to 7. Of the 397 patients with a record for supplemental oxygen, 36 (9.07%) received supplemental oxygen. The LASSO regression odds ratios (OR) found to be important for modeling supplemental oxygen use (in decreasing order of magnitude) are BMI ≥35 (OR = 2.30), pre-op AHI >30 (OR = 2.28), gastrointestinal comorbidities (OR = 2.20), musculoskeletal comorbidities (OR = 1.91), cardiac comorbidities (OR = 1.20), pulmonary comorbidities (OR = 1.14), and BMI 30 to <35 (OR = 1.07). Female gender was found to be negatively associated with risk of supplemental oxygen use (OR = 0.84). Age, race, AHI ≥15-30, neurologic comorbidities, syndromic patients, admission reason, and undergoing other procedures concomitantly were not found to be associated with increased postoperative oxygen requirement. CONCLUSION: BMI ≥30, pre-op AHI >30, male gender, and gastrointestinal, musculoskeletal, cardiac, and pulmonary comorbidities are all associated with postoperative supplemental oxygen use. Age, race, AHI ≥15-30, neurologic comorbidities, syndromic patients, admission reason, and undergoing other procedures concomitantly were not found to be associated with increased postoperative oxygen requirement.

Long-range optical coherence tomography of pediatric airway during drug induced sleep endoscopy: A preliminary report.

OBJECTIVE: Drug induced sleep endoscopy (DISE) is often performed for pediatric obstructive sleep apnea (OSA) when initial diagnostic studies do not provide adequate information for therapy. However, DISE scoring is subjective and with limitations. This proof-of-concept study demonstrates the use of a novel long-range optical coherence tomography (LR-OCT) system during DISE of two pediatric patients. METHODS: LR-OCT was used to visualize the airway of pediatric patients during DISE. At the conclusion of DISE, the OCT probe was guided in the airway under endoscopic visual guidance, and cross-sectional images were acquired at the four VOTE locations. Data processing involved image resizing and alignment, followed by rendering of three-dimensional (3D) volumetric models of the airways. RESULTS: Two patients were included in this study. Patient one had 18.4%, 20.9%, 72.3%, and 97.3% maximal obstruction at velum, oropharynx, tongue base, and epiglottis, while patient two had 40.2%, 41.4%, 8.0%, and 17.5% maximal obstruction at these regions, respectively. Three-dimensional reconstructions of patients' airways were also constructed from the OCT images. CONCLUSION: This proof-of-concept study demonstrates the successful evaluation of pediatric airway during DISE using LR-OCT, which accurately identified sites and degrees of obstruction with respective 3D airway reconstruction.

Influenza vaccine format mediates distinct cellular and antibody responses in human immune organoids.

Highly effective vaccines elicit specific, robust, and durable adaptive immune responses. To advance informed vaccine design, it is critical that we understand the cellular dynamics underlying responses to different antigen formats. Here, we sought to understand how antigen-specific B and T cells were activated and participated in adaptive immune responses within the mucosal site. Using a human tonsil organoid model, we tracked the differentiation and kinetics of the adaptive immune response to influenza vaccine and virus modalities. Each antigen format elicited distinct B and T cell responses, including differences in their magnitude, diversity, phenotype, function, and breadth. These differences culminated in substantial changes in the corresponding antibody response. A major source of antigen format-related variability was the ability to recruit naive vs. memory B and T cells to the response. These findings have important implications for vaccine design and the generation of protective immune responses in the upper respiratory tract.

Invasive Mycobacterium abscessus Outbreak at a Pediatric Dental Clinic.

BACKGROUND: Mycobacterium species, specifically M. abscessus and M. chelonae (MABs), are known to contaminate water systems and are uncommon causes of health care-associated infection, but morbidity can be significant and treatment complex. METHODS: Odontogenic MAB infections occurred in patients following pulpotomy procedures at dental clinic A from 1 January to 6 September 2016. We identified confirmed and probable cases using culture data, imaging, pathology results, and surgical findings. Epidemiologic and clinical data including demographics, symptoms, laboratory findings, treatment regimens, and outcomes were extracted. RESULTS: Of 1082 at-risk patients, 71 case patients (22 confirmed; 49 probable) were identified. Median age was 6 years. Median symptom onset was 85 days postpulpotomy. Pain and/or swelling on admission occurred in 79%. On imaging, 49 of 70 had abnormalities of the mandible or maxilla, 13 of 70 had lymphadenopathy, and 19 of 68 had pulmonary nodules. Seventy were hospitalized (average of 8.5 days). Intravenous antibiotics were administered to 32 cases for a median length of 137 days. Clofazimine was administered to 29 patients as part of their multidrug regimen. Antibiotic treatment was associated with many adverse effects. Treated children showed evidence of jaw healing with resolved/improving pulmonary nodules at 1-year follow-up. CONCLUSIONS: This is the largest outbreak of invasive MAB infections associated with a pediatric dental practice. While infections were indolent, patients suffered medical and surgical consequences of treatment, including permanent tooth loss. Identification of this outbreak led to a change in water standards for pediatric dental procedures in California. Enhanced national dental water quality standards are needed to prevent future outbreaks.

Persistence of choking injuries in children.

BACKGROUND: Choking injuries are a significant cause of morbidity and mortality in children and represent a significant public health concern. Evaluating trends and the impact of interventions are essential to highlight whether progress has been made and to target public health efforts. OBJECTIVE: To investigate how rates of nonfatal and fatal choking injuries have changed before and after 2010 when policy recommendations were made by the American Academy of Pediatrics. METHODS: A descriptive study investigating unintentional nonfatal and fatal choking injuries in children aged 0-19 years using national data from 2001 to 2016 through the Centers for Disease Control and Prevention's WISQARS™ and WONDER databases, focusing on the 6 years prior and 6 years after release of the AAP's recommendations. The data was categorized by age, gender, year, and race/ethnicity for descriptive and statistical analyses. RESULTS: From 2001 to 2016, there were a total of 305,814 nonfatal injuries and 2347 choking deaths in children from 0 to 19 years. Children under five years of age accounted for 73% of nonfatal injuries and 75% of choking fatalities. There was a statistically significant increase in the nonfatal injuries rate when comparing 2005-2010 and 2011-2016 (19/100,000 versus 26/100,000, respectively). There was a decrease in the choking fatalities rate in all children (0.18/100,000 versus 0.16/100,000, respectively) but no change in fatalities rate for children under five. White and Black children experience nonfatal choking injuries at a higher rate than Hispanics. Black children had highest rates of choking fatalities over Hispanic, White, Asian, and Alaskan or American Indian ethnicities. The lowest rates of death occurred in Asians. CONCLUSIONS: Overall rate of nonfatal choking injuries increased, while rate of choking fatalities in children decreased after 2010. However, the choking fatalities rate in 0-4 years olds, the highest risk group, did not change. Racial gaps exist with highest rates of injury in Black children. We must continue to educate and raise awareness of choking injuries, with targeted efforts to address racial disparities.

Advanced practice providers and children's hospital-based pediatric otolarynology practices.

INTRODUCTION: Advanced practice providers (APPs), including nurse practitioners and physician assistants, have been deployed in children's hospital-based academic pediatric otolaryngology practices for many years. However, this relationship in terms of prevalence, roles, financial consequences and satisfaction has not been examined. The objective of this study is to explore how APPs impact healthcare delivery in this setting. METHODS: Pediatric otolaryngology chiefs of all academic children's hospitals in the US were electronically surveyed about the ways APPs intersected clinically and financially in their respective practice. RESULTS: A total of 29 of 36 children's hospital-based pediatric otolaryngology practices completed the survey, of which 26 practices (90%) utilized APP. There were large variances within the APP practice cohort in faculty size (mean/median/range = 9.4/8.5/3-29); annual patient visits (mean/median = 18,373/17,600); number of practice site (mean/median/range = 4.3/4/2-9) and number of outpatient APP (mean/median/range = 6.3/5/1-30). No factors (faculty size, annual visits and number of practice sites) differentiated between the APP and non-APP practices. Among APP practices, significant correlation (p<.00001) was observed between size of APP cohort to faculty size and annual visits. 69% of the practices did not differentiate job functions of nurse practitioners and physician assistants. 85% of the practices utilized APPs in all practice sites and 19% utilized APPs in the operating room. 77% of APPs billed independently and 46% had on-site supervision. The most prevalent APP salary bracket based on 0-5, 6-10 and > 11 years of tenure were $76-100K (65%), $100-150K (77%) and $100-150K (86%), respectively. In 46% of the practices, APPs were able to generate enough revenue to cover more than 75% of their salary and 23% of practices generated a profit. 81% of the chiefs ranked the effectiveness of APPs as high (4 and 5) on a 5-point Likert scale. DISCUSSION: The majority of academic pediatric otolaryngology practices employed APPs. Despite the diversity seen in practice complexity, APP functionality and financial impact, most found the APP model to be beneficial in improving patient care, patient access and faculty productivity.

Dynamic programming and automated segmentation of optical coherence tomography images of the neonatal subglottis: enabling efficient diagnostics to manage subglottic stenosis.

Subglottic stenosis (SGS) is a challenging disease to diagnose in neonates. Long-range optical coherence tomography (OCT) is an optical imaging modality that has been described to image the subglottis in intubated neonates. A major challenge associated with OCT imaging is the lack of an automated method for image analysis and micrometry of large volumes of data that are acquired with each airway scan (1 to 2 Gb). We developed a tissue segmentation algorithm that identifies, measures, and conducts image analysis on tissue layers within the mucosa and submucosa and compared these automated tissue measurements with manual tracings. We noted small but statistically significant differences in thickness measurements of the mucosa and submucosa layers in the larynx (p < 0.001), subglottis (p = 0.015), and trachea (p = 0.012). The automated algorithm was also shown to be over 8 times faster than the manual approach. Moderate Pearson correlations were found between different tissue texture parameters and the patient's gestational age at birth, age in days, duration of intubation, and differences with age (mean age 17 days). Automated OCT data analysis is necessary in the diagnosis and monitoring of SGS, as it can provide vital information about the airway in real time and aid clinicians in making management decisions for intubated neonates.

Diagnosis of subglottic stenosis in a rabbit model using long-range optical coherence tomography.

OBJECTIVES/HYPOTHESIS: Current imaging modalities lack the necessary resolution to diagnose subglottic stenosis. The aim of this study was to use optical coherence tomography (OCT) to evaluate nascent subglottic mucosal injury and characterize mucosal thickness and structural changes using texture analysis in a simulated intubation rabbit model. STUDY DESIGN: Prospective animal study in rabbits. METHODS: Three-centimeter-long sections of endotracheal tubes (ETT) were endoscopically placed in the subglottis and proximal trachea of New Zealand White rabbits (n = 10) and secured via suture. OCT imaging and conventional endoscopic video was performed just prior to ETT segment placement (day 0), immediately after tube removal (day 7), and 1 week later (day 14). OCT images were analyzed for airway wall thickness and textural properties. RESULTS: Endoscopy and histology of intubated rabbits showed a range of normal to edematous tissue, which correlated with OCT images. The mean airway mucosal wall thickness measured using OCT was 336.4 µm (day 0), 391.3 µm (day 7), and 420.4 µm (day 14), with significant differences between day 0 and day 14 (P = .002). Significance was found for correlation and homogeneity texture features across all time points (P < .05). CONCLUSIONS: OCT is a minimally invasive endoscopic imaging modality capable of monitoring progression of subglottic mucosal injury. This study is the first to evaluate mucosal injury during simulated intubation using serial OCT imaging and texture analysis. OCT and texture analysis have the potential for early detection of subglottic mucosal injury, which could lead to better management of the neonatal airway and limit the progression to stenosis. LEVEL OF EVIDENCE: NA Laryngoscope, 127:64-69, 2017.

Increased immediate postoperative hemorrhage in older and obese children after outpatient tonsillectomy.

INTRODUCTION: Postoperative hemorrhage is one of the serious complications of adenotonsillar surgery. This study seeks to investigate the relationship between post-tonsillectomy/adenotonsillectomy hemorrhage in the pediatric population and obesity, obstructive sleep apnea (OSA), adenotonsillar hypertrophy (ATH), chronic tonsillitis (CT), and peritonsillar abscess (PTA) in the immediate post-operative setting. METHODS: The California Ambulatory Surgery Data for the years 2005-2011 were reviewed. The records of patients aged less than 18 years undergoing tonsillectomy (T) or adenotonsillectomy (AT) were extracted using relevant ICD-9 diagnosis codes. The association between hemorrhage and obesity, OSA, AH, CT, PTA, and patients' demographics among surgeries performed in the outpatient setting was evaluated. RESULTS: A total of 138,998 procedures, 22,478 Ts and 116,520 ATs, were performed during 2005-2011, of which 3.0% were performed on obese children. Hemorrhage occurred in 156 cases (0.1%), and was associated with an age from 9 to 18 years (p=0.01), and obesity (p=0.02). There was no association between hemorrhage and gender (p=0.8), OSA (p=0.6), ATH (p=0.5), CT (p=0.35), PTA (p=0.47), or T versus AT (p=0.3). Multivariate analysis revealed that hemorrhage was about 2.3 times more likely to occur in obese children (odds ratio [OR]=2.3; 95% Confidence Interval: 1.1-5.1; p=0.03). CONCLUSIONS: Obesity and older age are associated with an increased risk of immediate post-operative hemorrhage following tonsillectomy with or without adenoidectomy in the outpatient setting. Gender, OSA, ATH, CT, PTA, and T versus AT did not alter the risk of post-operative hemorrhage.

Long-Range Optical Coherence Tomography of the Neonatal Upper Airway for Early Diagnosis of Intubation-related Subglottic Injury.

RATIONALE: Subglottic edema and acquired subglottic stenosis are potentially airway-compromising sequelae in neonates following endotracheal intubation. At present, no imaging modality is capable of in vivo diagnosis of subepithelial airway wall pathology as signs of intubation-related injury. OBJECTIVES: To use Fourier domain long-range optical coherence tomography (LR-OCT) to acquire micrometer-resolution images of the airway wall of intubated neonates in a neonatal intensive care unit setting and to analyze images for histopathology and airway wall thickness. METHODS: LR-OCT of the neonatal laryngotracheal airway was performed a total of 94 times on 72 subjects (age, 1-175 d; total intubation, 1-104 d). LR-OCT images of the airway wall were analyzed in MATLAB. Medical records were reviewed retrospectively for extubation outcome. MEASUREMENTS AND MAIN RESULTS: Backward stepwise regression analysis demonstrated a statistically significant association between log(duration of intubation) and both laryngeal (P < 0.001; multiple r(2) = 0.44) and subglottic (P < 0.001; multiple r(2) = 0.55) airway wall thickness. Subjects with positive histopathology on LR-OCT images had a higher likelihood of extubation failure (odds ratio, 5.9; P = 0.007). Longer intubation time was found to be significantly associated with extubation failure. CONCLUSIONS: LR-OCT allows for high-resolution evaluation and measurement of the airway wall in intubated neonates. Our data demonstrate a positive correlation between laryngeal and subglottic wall thickness and duration of intubation, suggestive of progressive soft tissue injury. LR-OCT may ultimately aid in the early diagnosis of postintubation subglottic injury and help reduce the incidences of failed extubation caused by subglottic edema or acquired subglottic stenosis in neonates. Clinical trial registered with www.clinicaltrials.gov (NCT 00544427).

Intraoperative long range optical coherence tomography as a novel method of imaging the pediatric upper airway before and after adenotonsillectomy.

BACKGROUND/OBJECTIVES: While upper airway obstruction is a common problem in the pediatric population, the first-line treatment, adenotonsillectomy, fails in up to 20% of patients. The decision to proceed to surgery is often made without quantitative anatomic guidance. We evaluated the use of a novel technique, long-range optical coherence tomography (LR-OCT), to image the upper airway of children under general anesthesia immediately before and after tonsillectomy and/or adenoidectomy. We investigated the feasibility of LR-OCT to identify both normal anatomy and sites of airway narrowing and to quantitatively compare airway lumen size in the oropharyngeal and nasopharyngeal regions pre- and post-operatively. METHODS: 46 children were imaged intraoperatively with a custom-designed LR-OCT system, both before and after adenotonsillectomy. These axial LR-OCT images were both rendered into 3D airway models for qualitative analysis and manually segmented for quantitative comparison of cross-sectional area. RESULTS: LR-OCT images demonstrated normal anatomic structures (base of tongue, epiglottis) as well as regions of airway narrowing. Volumetric rendering of pre- and post-operative images clearly showed regions of airway collapse and post-surgical improvement in airway patency. Quantitative analysis of cross-sectional images showed an average change of 70.52mm(2) (standard deviation 47.87mm(2)) in the oropharynx after tonsillectomy and 105.58mm(2) (standard deviation 60.62mm(2)) in the nasopharynx after adenoidectomy. CONCLUSIONS: LR-OCT is an emerging technology that rapidly generates 3D images of the pediatric upper airway in a feasible manner. This is the first step toward development of an office-based system to image awake pediatric subjects and thus better identify loci of airway obstruction prior to surgery.

Long-range Fourier domain optical coherence tomography of the pediatric subglottis.

BACKGROUND: Acquired subglottic stenosis (SGS) most commonly results from prolonged endotracheal intubation and is a diagnostic challenge in the intubated child. At present, no imaging modality allows for in vivo characterization of subglottic microanatomy to identify early signs of acquired SGS while the child remains intubated. Fourier domain optical coherence tomography (FD-OCT) is a minimally invasive, light-based imaging modality which provides high resolution, three dimensional (3D) cross-sectional images of biological tissue. We used long-range FD-OCT to image the subglottis in intubated pediatric patients undergoing minor head and neck surgical procedures in the operating room. METHODS: A long-range FD-OCT system and rotary optical probes (1.2mm and 0.7mm outer diameters) were constructed. Forty-six pediatric patients (ages 2-16 years) undergoing minor upper airway surgery (e.g., tonsillectomy and adenoidectomy) were selected for intraoperative, trans-endotracheal tube FD-OCT of the subglottis. Images were analyzed for anatomical landmarks and subepithelial histology. Volumetric image sets were rendered into virtual 3D airway models in Mimics software. RESULTS: FD-OCT was performed on 46 patients (ages 2-16 years) with no complications. Gross airway contour was visible on all 46 data sets. Twenty (43%) high-quality data sets clearly demonstrated airway anatomy (e.g., tracheal rings, cricoid and vocal folds) and layered microanatomy of the mucosa (e.g., epithelium, basement membrane and lamina propria). The remaining 26 data sets were discarded due to artifact, high signal-to-noise ratio or missing data. 3D airway models were allowed for user-controlled manipulation and multiplanar airway slicing (e.g., sagittal, coronal) for visualization of OCT data at multiple anatomic levels simultaneously. CONCLUSIONS: Long-range FD-OCT produces high-resolution, 3D volumetric images of the pediatric subglottis. This technology offers a safe and practical means for in vivo evaluation of lower airway microanatomy in intubated pediatric patients. Ultimately, FD-OCT may be applied to serial monitoring of the neonatal subglottis in long-term intubated infants at risk for acquired SGS.

Real-time subglottic stenosis imaging using optical coherence tomography in the rabbit.

IMPORTANCE: Subglottic stenosis (SGS) is a severe, acquired, potentially life-threatening disease that can be caused by endotracheal tube intubation. Newborns and neonates are particularly susceptible to SGS owing to the small caliber of their airway. OBJECTIVE: To demonstrate optical coherence tomography (OCT) capabilities in detecting injury and scar formation using a rabbit model. Optical coherence tomography may provide a noninvasive, bedside or intensive care unit modality for the identification of early airway trauma with the intention of preventing progression to SGS and can image the upper airway through an existing endotracheal tube coupled with a small fiber-optic probe. DESIGN: Rabbits underwent suspension laryngoscopy with induction of of SGS via epithelial injury. This model was used to test and develop our advanced, high-speed, high-resolution OCT imaging system using a 3-dimensional microelectromechanical systems-based scanning device integrated with a fiber-optic probe to acquire high-resolution anatomic images of the subglottic epithelium and lamina propria. SETTING: All experiments were performed at the Beckman Laser Institute animal operating room. INTERVENTION OR EXPOSURE: Optical coherence tomography and endoscopy was performed with suspension laryngoscopy at 6 different time intervals and compared with conventional digital endoscopic images and histologic sections. Fifteen rabbits were killed at 3, 7, 14, 21, and 42 days after the induction of SGS. The laryngotracheal complexes were serially sectioned for histologic analysis. MAIN OUTCOME AND MEASURE: Histologic sections, endoscopic images, and OCT images were compared with one another to determine if OCT could accurately delineate the degree of SGS achieved. RESULTS: The rabbit model was able to reliably and reproducibly achieve grade I SGS. The real-time OCT imaging system was able to (1) identify multiple structures in the airway; (2) delineate different tissue planes, such as the epithelium, basement membrane, lamina propria, and cartilage; and (3) detect changes in each tissue plane produced by trauma. Optical coherence tomography was also able demonstrate a clear picture of airway injury that correlated with the endoscopic and histologic images. With subjective review, 3 patients had high correlation between OCT and histologic images, 10 demonstrated some correlation with histologic images, and 2 showed little to no correlation with histologic images. CONCLUSIONS AND RELEVANCE: Optical coherence tomography, coupled with a fiber-optic probe, identifies subglottic scarring and can detect tissue changes in the rabbit airway to a depth of 1 mm. This technology brings us 1 step closer to minimally invasive subglottic airway monitoring in the intubated neonate, with the ultimate goal of preventing SGS and better managing the airway.

Optical coherence tomography of the newborn airway.

OBJECTIVES: Acquired subglottic stenosis in a newborn is often associated with prolonged endotracheal intubation. This condition is generally diagnosed during operative endoscopy after airway injury has occurred. Unfortunately, endoscopy is unable to characterize the submucosal changes observed in such airway injuries. Other modalities, such as magnetic resonance imaging, computed tomography, and ultrasound, do not possess the necessary level of resolution to differentiate scar, neocartilage, and edema. Optical coherence tomography (OCT) is an imaging modality that produces high-resolution, cross-sectional images of living tissue (8 to 20 microm). We examined the ability of this noninvasive technique to characterize the newborn airway in a prospective clinical trial. METHODS: Twelve newborn patients who required ventilatory support underwent OCT airway imaging. Comparative analysis of intubated and non-intubated states was performed. RESULTS: Imaging of the supraglottis, glottis, subglottis, and trachea was performed in 12 patients, revealing unique tissue characteristics as related to turbidity, signal backscattering, and architecture. Multiple structures were identified, including the vocal folds, cricoid cartilage, tracheal rings, ducts, glands, and vessels. CONCLUSIONS: Optical coherence tomography clearly identifies in vivo tissue layers and regional architecture while offering detailed information concerning tissue microstructures. The diagnostic potential of this technology makes OCT a promising modality in the study and surveillance of the neonatal airway.

Interaction between carbon and nitrogen metabolism during akinete development in the cyanobacterium Anabaena torulosa.

Nutrient enrichment with a nitrogen (as nitrate) or carbon (as fructose) source to unaerated diazo and photoautorophic cultures of the cyanobacterium Anabaena torulosa induced early development of akinetes with high frequency. When cultures under any mode of nutrition were aerated, akinetes were not differentiated. Unaerated cultures with nitrate nitrogen or fructose exhibited higher respiratory rates and nitrogen assimilation compared to aerated cultures. This was evidenced by increased respiratory O2 uptake and high activities of pyruvate kinase, malate dehydrogenase (NAD+), nitrogenase and nitrate reductase signifying that akinete forming unaerated cultures exhibited high carbon dissimilation and nitrogen assimilation resulting in high nitrogenous build up in the cells. Aerated, non-akinete cultures, on the other hand, were associated with low respiratory O2 uptake, low pyruvate kinase and malate dehydrogenase (NAD+) activities, suggesting that carbon dissimilation was not favoured either in presence of nitrate or fructose. Moreover, higher activity of NADP+ linked malate dehydrogenase and lower nitrate reductase activity in aerated cultures led to a high carbon and low nitrogen content of the cells resulting in high cellular C:N ratio. The results suggest that interaction between carbon and nitrogen metabolism regulates akinete development in A. torulosa.

Imaging of the pediatric airway using optical coherence tomography.

OBJECTIVES: Optical coherence tomography (OCT) is an imaging modality that uses a broadband light source to produce high-resolution cross-sectional images in living tissue (8-20 microm). A prospective study of normal, benign, and pathologic tissues in the pediatric airway was conducted to assess the utility of OCT technology in characterizing the microanatomy of the pediatric upper aerodigestive tract in vivo. STUDY DESIGN: Prospective clinical trial. MATERIALS AND METHODS: Fifteen patients from 1 to 17 years of age underwent surgical endoscopy and OCT for various airway disorders. OCT imaging was performed at a frame rate of 1 Hz using a 1.3-microm broadband light source to produce images 1.6 x 6 mm in vertical and horizontal dimensions. The epithelium, lamina propria, and unique tissue microstructures were visualized and then measured using digital micrometry. Direct comparison of OCT images with endoscopic photography was performed. RESULTS: Systematic imaging of the oral cavity, oropharynx, hypopharynx, and larynx was performed in all 15 patients. Normal microstructures identified included papillae, ducts, glands, and vessels, whereas pathologic conditions included distinct zones of mature scar, granulation tissue, edema, ulceration, and papillomatosis. Endoscopic photographs were well correlated with OCT images. CONCLUSIONS: OCT is capable of obtaining high-resolution microanatomy images of pediatric airway in vivo tissue. OCT clearly identifies the epithelium and lamina propria while providing detailed structural information on normal and diseased tissues. OCT is a promising emerging imaging modality for use in current pediatric patient populations.

Characterization of submucosal lesions using optical coherence tomography in the rabbit subglottis.

OBJECTIVE: To evaluate the efficacy of optical coherence tomography in differentiating between several simulated subglottic lesions, using an ex vivo rabbit laryngotracheal model. DESIGN: Laryngotracheal complexes were harvested from euthanized rabbits and divided into the following 4 groups: (1) control, (2) submucosal collagen injection (simulating scar formation), (3) dehydration and rehydration (simulating edema), and (4) repeated intubation trauma. The subglottic region was imaged using optical coherence tomography. Images were later correlated with conventional histologic findings. RESULTS: The epithelium, basement membrane, lamina propria, perichondrium, and cartilage (cricoid and tracheal) were clearly imaged. In group 2, an increase in the thickness of the lamina propria was observed, in addition to a characteristic optical pattern of the injected collagen. Dehydration (in group 3) produced a visible reduction in the thickness of the lamina propria, while rehydration of the same specimen with distilled water revealed a significant increase in submucosal swelling. Repeated intubation (in group 4) resulted in tissue edema that was seen as wavy heterogeneous thickening of the lamina propria. Edema produced by repeated intubation or distilled water immersion was easily differentiated from native and collagen-injected tissues. CONCLUSION: Optical coherence tomography successfully identifies the microstructure layers of the subglottis and can differentiate between edema and increased collagen deposition in the rabbit model.

Lasers in pediatric airway surgery: current and future clinical applications.

BACKGROUND AND OBJECTIVES: The smaller anatomy and limited access to instrumentation pose a challenge to the pediatric airway surgeon. The enhanced precision and ability to photocoagulate tissue while operating with the laser enhances the surgeon's ability to successfully treat unique pediatric conditions. STUDY DESIGN/MATERIALS AND METHODS: A comprehensive literature review was performed using the Medline (1995-2004) database. RESULTS: Due to its shallow tissue penetration and thermal effect, the carbon dioxide (CO2) laser is generally considered the laser of choice for pediatric airway applications. The potential for increased scarring and damage to underlying tissue caused by the greater penetration depth and thermal effect of the Nd:YAG and potassium-titanyl-phosphate (KTP) lasers preclude their widespread use in this population. CONCLUSIONS: In this review, we will discuss the clinical applications of lasers in pediatric airway surgery, the current state of the art, where the current technology is deficient, and the potential applications of novel laser systems.

Nutrient stress causes akinete differentiation in cyanobacterium Anabaena torulosa with concomitant increase in nitrogen reserve substances.

Addition of nitrogen source (nitrate), carbon sources (acetate, citrate and fructose), depletion of nutrients (phosphate-free nitrate medium), dilution of medium (2, 4 and 8 times diluted nitrate medium) under unaerated conditions induced akinete differentiation in Anabaena torulosa. Aerated cultures under the same conditions did not differentiate akinetes. The amounts of reserve metabolites--glycogen and cyanophycin (multi-L-arginyl-poly-L-aspartic acid) granule polypeptide (CGP)--were determined in unaerated and aerated cultures, and at different stages of growth and akinete differentiation. The addition of nitrate, acetate, citrate and fructose under unaerated conditions resulted in the accumulation of glycogen and CGP in higher amounts after 4 d (akinete initiation); the CGP content further changed at mature free akinetes phase. Higher accumulation of reserve products was also observed under nutrient deficiency (phosphate-depleted or diluted media) after 4 d of cultivation. Under aerated conditions reserve product accumulation was considerably lower. Thus a low accumulation of reserve products in aerated cultures showed that aeration probably somehow relieves the organism from a nutritional stress.