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Of the 300 billion capillaries in the human lung, a small fraction meet normal oxygen requirements at rest, with the remainder forming a large reserve. The maximum oxygen demands of the acute stress response require that the reserve capillaries are rapidly recruited. To remain primed for emergencies, the normal cardiac output must be parceled throughout the capillary bed to maintain low opening pressures. The flowdistributing system requires complex switching. Because the pulmonary microcirculation contains contractile machinery, one hypothesis posits an active switching system. The opposing hypothesis is based on passive switching that requires no regulation. Both hypotheses were tested ex vivo in canine lung lobes. The lobes were perfused first with autologous blood, and capillary switching patterns were recorded by videomicroscopy. Next, the vasculature of the lobes was saline flushed, fixed by glutaraldehyde perfusion, flushed again, and then reperfused with the original, unfixed blood. Flow patterns through the same capillaries were recorded again. The 16-min-long videos were divided into 4-s increments. Each capillary segment was recorded as being perfused if at least one red blood cell crossed the entire segment. Otherwise it was recorded as unperfused. These binary measurements were made manually for each segment during every 4 s throughout the 16-min recordings of the fresh and fixed capillaries (>60,000 measurements). Unexpectedly, the switching patterns did not change after fixation. We conclude that the pulmonary capillaries can remain primed for emergencies without requiring regulation: no detectors, no feedback loops, and no effectors—a rare system in biology. NEW & NOTEWORTHY The fluctuating flow patterns of red blood cells within the pulmonary capillary networks have been assumed to be actively controlled within the pulmonary microcirculation. Here we show that the capillary flow switching patterns in the same network are the same whether the lungs are fresh or fixed. This unexpected observation can be successfully explained by a new model of pulmonary capillary flow based on chaos theory and fractal mathematics. [ABSTRACT FROM AUTHOR]

Objectives: Deficient cochlear nerves (CN) have been associated with poor cochlear implant performance. Normative data on CN diameter based on radiographic imaging have not been published. The objectives of this study were to determine if CN diameter could be reproducibly measured on parasagittal constructive interference in steady state (CISS)-sequence magnetic resonance imaging (MRI) and to establish a normative range for CN diameter. Study Design: Retrospective review of MRI images by two independent blinded observers. Methods: Thirty patients (45 ears) with a CISS-sequence MRI done for auditory complaints in patients with normal hearing in one ear were included. CN diameters were measured in a parasagittal plane just medial to the internal auditory canal (IAC) fundus by two independent observers. Cross-sectional areas were calculated and interobserver agreement was evaluated. Results: The CN was identified in 100% of studied ears. In 93%, the diameters were able to be measured by both observers. In 7% of ears, the cochlear nerve was unable to be measured secondary to the proximity of the CN to IAC wall. The CN vertical diameter (1.4 mm ± 0.21 mm), horizontal diameter (1.0 mm ± 0.15 mm), and cross-sectional area (1.1 mm ± 0.26 mm2) were normally distributed. There was good interobserver correlation for each measure. Conclusions: CN diameter can be reliably measured at the IAC fundus. This study establishes normative radiographic data for the CN diameter. These data may be used to evaluate the cause and treatment prognosis in patients with sensorineural hearing loss. Laryngoscope, 2009 [ABSTRACT FROM AUTHOR]

Pulmonary capillary perfusion within a single alveolar wall continually switches among segments, even when large-vessel hemodynamics are constant. The mechanism is unknown. We hypothesize that the continually varying size of plasma gaps between individual red blood cells affects the likelihood of capillary segment closure and the probability of cells changing directions at the next capillary junction. We assumed that an increase in hematocrit would decrease the average distance between red blood cells, thereby decreasing the switching at each capillary junction. To test this idea, we observed 26 individual alveolar capillary networks by using videomicroscopy of excised canine lung lobes that were perfused first at normal hematocrit (31–43%) and then at increased hematocrit (51–62%). The number of switches decreased by 38% during increased hematocrit (P < 0.01). These results support the idea that a substantial part of flow switching among pulmonary capillaries is caused by the particulate nature of blood passing through a complex network of tubes with continuously varying hematocrit. [ABSTRACT FROM AUTHOR]

Studies heterogeneous capillary recruitment among adjoining alveoli. Gradual homogeneous recruitment; Increase of microvascular pressure.

Objectives: Fourth branchial cleft anomalies are rare and can present in a variety of ways in the head and neck. Limited data exists on the treatment of complex recurrent fistulas. We present a unique case utilizing a pedicled submental flap in the management of a persistent fourth branchial anomaly and discuss the use of pedicled flaps in the pediatric population. Study Design: Retrospective chart review. Methods: Patient data were collected from a tertiary care pediatric hospital medical record. Results: An 8 year old patient presented to our institution with a history of recurrent left neck infections and multiple failed incision and drainage procedures. Aggressive surgical options failed. She eventually underwent a complete resection of the fistula with partial pharyngectomy, left selective neck dissection, and two layered closure of the pharyngotomy defect with an oversewn pedicled submental island flap. The surgery was uneventful and the patient is without evidence of recurrence 7 months postoperatively. Conclusions: Treatment options for fourth branchial anomalies include incision and drainage, endoscopic cauterization via direct laryngoscopy or open neck surgery with complete sinus tract excision and thyroidectomy. Persistent disease requires aggressive management with partial pharyngectomy with/without the use of additional soft tissue for coverage. For significant pharyngeal defects, submental pedicled flaps can be utilized in repair and closure. To our knowledge this is the first reported case of a pedicled submental flap for closure of a pharyngotomy defect in the pediatric population. The use of the submental flap in this group is feasible, with few to no complications, and offers very acceptable cosmesis. [ABSTRACT FROM AUTHOR]

Educational Objective: At the conclusion of this presentation, the participants should be able to discuss the differential diagnosis of a pars squamosa temporal bone mass, discuss unusual locations in which cholesteatoma may appear, and explain the need for long term followup in canal wall down mastoidectomy patients. Objectives: To present a case of an acquired cholesteatoma presenting as a large lateral pars squamosa temporal bone mass and review the literature on cholesteatoma presenting in unusual locations. Study Design: Case report and review of the literature. Methods: While congenital cholesteatomas have been reported to arise in atypical locations such as the maxillary sinus and occipitoparietotemporal junction, there have been very few reports of acquired cholesteatomas arising in unusual locations. A 16 year old female with an acquired cholesteatoma presenting as a large lateral squamous temporal bone mass with intracranial extension nine years after canal wall down (CWD) mastoidectomy and six years after revision surgery is presented. Her management and followup are discussed and a review of the literature for atypical locations of cholesteatoma is presented. Results: Review of the English literature revealed only a single case of acquired cholesteatoma within the squamous temporal bone. Our patient underwent successful excision of the mass through a lateral approach, confirming the diagnosis. Conclusions: Acquired cholesteatoma typically arises in the middle ear and mastoid. Rarely, it can present in atypical locations. The consequences of undiagnosed, untreated cholesteatoma can be significant. This case highlights the need for routine long term surveillance in children with CWD mastoidectomy cavities. [ABSTRACT FROM AUTHOR]

Educational Objective: At the conclusion of this presentation, the participants should be able to discuss the management of persistent pediatric parotid masses and explain the role of surgery as a diagnostic and therapeutic tool for these lesions. Objectives: To present case vignettes of unusual parotid pathologies and discuss management paradigms in the context of these lesions. Study Design: Retrospective case series. Methods: Five consecutive patients over the past 18 months undergoing parotidectomy for a parotid neoplasm, each with an unusual pathology, were reviewed. Results: Ages ranged from 17 months to 16 years. All presented with a remarkably similar clinical course, consisting of a mostly painless, persistent parotid mass for more than 3 months. Most (4/5 patients) had been treated with antibiotics prior to otolaryngology consultation. Fine needle aspiration (FNA) was performed on 3 patients and was diagnostic in one. Complete excision was performed in each child through a parotidectomy approach (3 total, 2 lateral lobe). The final pathology consisted of metastatic neuroblastoma (17 mos. old), undifferentiated primitive sarcoma (22 mos. old), mucoepidermoid carcinoma (11 years old), nodular fasciitis (12 years old), and hyperplastic lymph node (16 years old). The patient with neuroblastoma died. Conclusions: The differential diagnosis for a persistent pediatric parotid mass is expansive. In most cases it is impossible to discern the pathology, or rule out malignancy, based upon the clinical course, imaging, or FNA results. Excisional surgical management remains the gold standard diagnostic and therapeutic tool for most patients. Our anecdotal case series highlights the importance of having a low threshold for parotidectomy in these children. [ABSTRACT FROM AUTHOR]

Objectives: To determine the incidence and to describe wound complications and associated risk factors of pediatric tracheotomy., Design: Retrospective case series., Setting: Freestanding tertiary care academic pediatric hospital., Patients: Sixty-five consecutive children undergoing tracheotomy over 15 months., Main Outcome Measures: Postoperative wound complications objectively and independently documented by an advanced practice nurse specializing in tracheotomy care. Secondary outcome measures included comorbidities, mortality rates, and wound status after subsequent examinations and management., Results: The mean (SEM) patient age at tracheotomy was 45 (8.7) months (median age, 9.1 months). The most common indication for tracheotomy was pulmonary disease (36.9%), followed by neurologic impairment and laryngeal abnormalities. There were 19 patients (29%) with and 46 patients (71%) without wound complications. There were no significant differences between the 2 groups in age (P = .68) or weight (P = .55); however, infants younger than 12 months had an increased complication rate (39% vs. 17%, P = .04). The type of tracheotomy tube was predictive of postoperative wound complications (P = .02). All patients with wounds received aggressive local wound care. Five of 13 patients had complete resolution of stomal wounds, whereas 8 patients had persistent wound issues. There were 5 non-wound-related mortalities., Conclusions: With attempts to classify tracheotomy wound breakdowns as reportable events, including never events, increasing emphasis is being placed on posttracheotomy care. This study demonstrates that wound breakdown in pediatric tracheotomy patients is common. These complications can be mitigated, although not prevented completely, with aggressive wound surveillance and specialized wound care.

Objective: To determine polysomnographic (PSG) variables that may potentially predict adverse respiratory events after pediatric adenotonsillectomy., Design: Retrospective, case-control study., Setting: Free-standing academic tertiary-care pediatric hospital., Patients: The study included 1131 patients undergoing adenotonsillectomy by 2 attending surgeons. There were no exclusion criteria., Main Outcome Measures: Variables from preoperative PSGs were analyzed to determine predictors of postoperative respiratory complications. Logistic regression analysis was performed., Results: A total of 151 patients (13.4%) underwent preoperative PSG. Twenty-three of these patients (15.2%) had adverse respiratory events. The primary adverse event was desaturation requiring supplemental oxygen therapy, with 1 case of postobstructive pulmonary edema. Patients with adverse events had a significantly higher apnea-hypopnea index) (31.8 vs 14.1; P = .001), higher hypopnea index (22.6 vs 8.9; P = .004), higher body mass index (z score, 1.43 vs 0.70; P = .02), and lower nadir oxygen saturation (72% vs 84%; P <.001). Patients with adverse events had a prolonged hospital course (odds ratio, 32.1; 95% confidence interval, 7.8-131.4). There were no differences in age or other PSG variables. There were no intubations or mortalities., Conclusions: Polysomnography may be used to predict which patients are at higher risk for adverse respiratory events after adenotonsillectomy. Such knowledge is valuable for planning optimal postoperative management and intraoperative anesthesia. Predictors of increased respiratory complications include apnea-hypopnea index, hypopnea index, body mass index, and nadir oxygen saturation.

Objectives: Microbial biofilms have been associated with poor outcomes with a variety of biomedical implants; however, this relationship has not been established with ossicular chain reconstruction prostheses (ORPs). The purpose of this study was to determine if biofilms are present on ORPs in patients undergoing revision ossicular chain reconstruction and if their presence correlates with middle ear scarring or hearing outcomes., Study Design: Prospective and blinded., Setting: Tertiary referral center., Patients: Patients undergoing revision ossicular chain reconstruction with previous ORP placement were enrolled. INTERVENTION/MAIN OUTCOME MEASURE: Ossicular chain reconstruction prostheses associated with poor hearing and residual or recurrent disease were cultured and examined using scanning electron microscopy. Audiometric thresholds and middle ear scarring scores were recorded., Results: Twelve patients were included in the study. Of the prostheses, 25% were culture positive, and 67% had microscopic evidence of biofilm. No difference was found between the middle ear scarring scores (p = 0.31) and hearing outcomes (p = 0.11) of biofilm and nonbiofilm prostheses. There was no correlation between middle ear scarring and degree of conductive hearing loss (R2 = 0.04; p = 0.54)., Conclusion: Biofilms are commonly found on ORPs at the time of revision ossicular chain reconstruction. The interaction between biofilms and the host environment is complex. Many factors besides biofilms may impact middle ear scarring and hearing.

Pulmonary capillary perfusion within a single alveolar wall continually switches among segments, even when large-vessel hemodynamics are constant. The mechanism is unknown. We hypothesize that the continually varying size of plasma gaps between individual red blood cells affects the likelihood of capillary segment closure and the probability of cells changing directions at the next capillary junction. We assumed that an increase in hematocrit would decrease the average distance between red blood cells, thereby decreasing the switching at each capillary junction. To test this idea, we observed 26 individual alveolar capillary networks by using videomicroscopy of excised canine lung lobes that were perfused first at normal hematocrit (31-43%) and then at increased hematocrit (51-62%). The number of switches decreased by 38% during increased hematocrit (P < 0.01). These results support the idea that a substantial part of flow switching among pulmonary capillaries is caused by the particulate nature of blood passing through a complex network of tubes with continuously varying hematocrit.