Physiological responses and perceived comfort to high-flow nasal cannula therapy in awake adults: effects of flow magnitude and temperature.

Clinical use of heated, high-flow nasal cannula (HFNC) for noninvasive respiratory support is increasing and may have a therapeutic role in stabilizing the upper airway in obstructive sleep apnea (OSA). However, physiological mechanisms by which HFNC therapy may improve upper airway function and effects of different temperature modes are unclear. Accordingly, this study aimed to determine effects of incremental flows and temperature modes (heated and nonheated) of HFNC on upper airway muscle activity (genioglossus), pharyngeal airway pressure, breathing parameters, and perceived comfort. Six participants (2 females, aged 35 ± 14 yr) were studied during wakefulness in the supine position and received HFNC at variable flows (0-60 L/min) during heated (37°C) and nonheated (21°C) modes. Breathing parameters via calibrated Respitrace inductance bands (chest and abdomen), upper airway pressures via airway transducers, and genioglossus muscle activity via intramuscular bipolar fine wire electrodes were measured. Comfort levels during HFNC were quantified using a visual analog scale. Increasing HFNC flows did not increase genioglossus muscle activation despite increased negative epiglottic pressure swings (P = 0.009). HFNC provided ∼7 cmH2O positive airway pressure at 60 L/min in nonheated and heated modes. In addition, increasing the magnitude of HFNC flow reduced breathing frequency (P = 0.045), increased expiratory time (P = 0.040), increased peak inspiratory flow (P = 0.002), and increased discomfort (P = 0.004). Greater discomfort occurred at higher flows in the nonheated versus the heated mode (P = 0.034). These findings provide novel insight into key physiological changes that occur with HFNC for respiratory support and indicate that the primary mechanism for improved upper airway stability is positive airway pressure, not increased pharyngeal muscle activity.NEW & NOTEWORTHY This study evaluated upper airway muscle function, breathing, and comfort across different HFNC flows and temperatures. There were no increases in genioglossus muscle activity at higher flows despite greater negative epiglottic pressure swings. Increasing negative pressure swings was associated with increasing discomfort in the nonheated mode. HFNC was associated with ∼7 cmH2O increase in positive airway pressure, which may be the primary mechanism for upper airway stability with HFNC rather than increases in pharyngeal muscle activity.

Sternohyoid and diaphragm muscle form and function during postnatal development in the rat.

NEW FINDINGS: What is the central question of this study? Co-ordinated activity of the thoracic pump and pharyngeal dilator muscles is critical for maintaining airway calibre and respiratory homeostasis. Whilst postnatal maturation of the diaphragm has been well characterized, surprisingly little is known about the developmental programme in the airway dilator muscles. What is the main finding and its importance? Developmental increases in force-generating capacity and fatigue in the sternohyoid and diaphragm muscles are attributed to a maturational shift in muscle myosin heavy chain phenotype. This maturation is accelerated in the sternohyoid muscle relative to the diaphragm and may have implications for the control of airway calibre in vivo. The striated muscles of breathing, including the thoracic pump and pharyngeal dilator muscles, play a critical role in maintaining respiratory homeostasis. Whilst postnatal maturation of the diaphragm has been well characterized, surprisingly little is known about the developmental programme in airway dilator muscles given that co-ordinated activity of both sets of muscles is needed for the maintenance of airway calibre and effective pulmonary ventilation. The form and function of sternohyoid and diaphragm muscles from Wistar rat pups [postnatal day (PD) 10, 20 and 30] was determined. Isometric contractile and endurance properties were examined in tissue baths containing Krebs solution at 35°C. Myosin heavy chain (MHC) isoform composition was determined using immunofluorescence. Muscle oxidative and glycolytic capacity was assessed by measuring the activities of succinate dehydrogenase and glycerol-3-phosphate dehydrogenase using semi-quantitative histochemistry. Sternohyoid and diaphragm peak isometric force and fatigue increased significantly with postnatal maturation. Developmental myosin disappeared by PD20, whereas MHC2B areal density increased significantly from PD10 to PD30, emerging earlier and to a much greater extent in the sternohyoid muscle. The numerical density of fibres expressing MHC2X and MHC2B increased significantly during development in the sternohyoid. Diaphragm succinate dehydrogenase activity and sternohyoid glycerol-3-phosphate dehydrogenase activity increased significantly with age. Developmental increases in force-generating capacity and fatigue in the sternohyoid and diaphragm muscles are attributed to a postnatal shift in muscle MHC phenotype. The accelerated maturation of the sternohyoid muscle relative to the diaphragm may have implications for the control of airway calibre in vivo.

Chronic hypoxia increases rat diaphragm muscle endurance and sodium-potassium ATPase pump content.

The effects of chronic hypoxia (CH) on respiratory muscle are poorly understood. The aim of the present study was to examine the effects of CH on respiratory muscle structure and function, and to determine whether nitric oxide is implicated in respiratory muscle adaptation to CH. Male Wistar rats were exposed to CH for 1-6 weeks. Sternohyoid and diaphragm muscle contractile properties, muscle fibre type and size, the density of fibres expressing sarco/endoplasmic reticulum calcium-ATPase (SERCA) 2 and sodium-potassium ATPase (Na+,K+-ATPase) pump content were determined. Muscle succinate dehydrogenase (SDH) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) dehydrogenase activities were also assessed. Acute and chronic blockade of nitric oxide synthase (NOS) was employed to determine whether or not NO is critically involved in functional remodelling in CH muscles. CH improved diaphragm, but not sternohyoid, fatigue tolerance in a time-dependent fashion. This adaptation was not attributable to increased SDH or NADPH dehydrogenase activities. The areal density of muscle fibres and relative area of fibres expressing SERCA2 were unchanged. Na+,K+-ATPase pump content was significantly increased in CH diaphragm. Chronic NOS inhibition decreased diaphragm Na+,K+-ATPase pump content and prevented CH-induced increase in muscle endurance. This study provides novel insight into the mechanisms involved in CH-induced muscle plasticity. The results may be of relevance to respiratory disorders characterised by CH, such as chronic obstructive pulmonary disease.

Comparison of ex situ and in situ bioremediation of unsaturated soils contaminated by petroleum.

The most feasible bioremediation technologies of unsaturated soils contaminated by Petroleum are (1) the on-site controlled remediation of the excavated contaminated plume in the contained system; and (2) the in situ sub-surface, highly controlled process in which nutrients and microbes or air are injected into the plume volume via a grid of wells and reversing the direction of the pumping. The detailed results of ex situ (controlled aerobic bioremediation) of ten sites with differing petroleum contamination and four in situ cases are reported and compared. It is concluded, that bioremediation of petroleum contaminated soil is an effective, safe and economically feasible remediation technique for the remediation of such contaminated sites, contingent on the providing of the site-specific appropriate conditions. However, the biodegradation rate of the NAPL is more variable in the in situ than in the ex situ aerobic process, correlating best in the latter with the molecular weight of the petroleum contaminants.

Primary lymphoma of the internal auditory canal. Case report and review of the literature.

We report a rare case of a primary intracranial B cell lymphoma originating in the internal auditory canal. The clinical manifestations were indistinguishable from those of other, more common tumors of the same region. We achieved total gross tumor removal with preservation of the facial nerve. A detailed histologic examination and a systemic workup confirmed the primary nature of this tumor. To our knowledge, this is the second case reported in the literature of a primary malignant lymphoma originating in the internal auditory canal. This is the first instance that includes immunohistochemical and cytometric studies of fresh tissue. We discuss the management of primary lymphomas of the central nervous system, with special emphasis on their association with acquired immunodeficiency syndrome and other immune system diseases. Awareness of primary central nervous system lymphomas is important, since a greater occurrence of these rare tumors in the cerebellopontine angle is probable in the future.

Reclassification of aggressive adenomatous mastoid neoplasms as endolymphatic sac tumors.

The emerging concept that aggressive adenomatous tumors of the temporal bone arise from the endolymphatic sac and constitute a distinct clinicopathologic entity merits wider recognition. These tumors share a common clinical pattern and exhibit consistent imaging and histopathologic features. Endolymphatic sac tumors (ELSTs) have been mistaken for other neoplasms such as paragangliomas, adenomatous tumors of mixed histology, ceruminomas, and choroid plexus papillomas. A review of the literature shows similarities among case studies of these aggressive adenomatous lesions. An analysis of the data supports the endolymphatic sac as an origin for these tumors. This report also presents an additional case of a less differentiated variant of this rare but important clinicopathologic entity.

Endolymphatic sac tumors: radiologic appearance.

PURPOSE: To evaluate the radiologic appearance of endolymphatic sac tumors (ELSTs). MATERIALS AND METHODS: Four patients with ELST underwent computed tomography (CT), and two of the four also underwent magnetic resonance (MR) imaging. Their radiologic studies were reviewed for characteristic findings of ELST. RESULTS: Retrolabyrinthine bone destruction was centered at the external aperture of the vestibular aqueduct in all four patients. CT showed irregular bone margins and prominent intratumoral bone in all four patients. At MR imaging, one tumor was almost homogeneous and isointense to gray matter with T1 weighting, and the other was heterogeneous and contained hyper-, hypo-, and isointense foci with T1 and T2 weighting. CONCLUSION: These radiologic changes may help distinguish ELSTs from other tumors of the temporal bone and posterior fossa.

Fractal analysis of size effects and surface morphology effects in catalysis and electrocatalysis.

Fractal geometry tools are used in order to analyze several related problems in surface science, catalysis, and electrocatalysis. The effects of complex morphologies of adsorbents, catalysts, and electrodes on various molecular processes with these materials are determined both theoretically and experimentally. It is shown that fractal geometry provides a convenient and natural tool for the elucidation of geometry-performance relations in heterogeneous chemistry. Issues covered are particle size effects in physisorption and chemisorption; morphology effects on a variety of catalytic processes with unsupported catalysts (including coal liquefaction, alkene polymerizations, oxidations, dehydrogenations, and esterifications); surface accessibility effects on molecular interactions in an Eley-Rideal mechanism; surface patterning effects on concentration profiles near the surface; and electrode-morphology effects on a variety of electrochemical and electrocatalytic processes. The domains of applicability of the fractal approach to these problems is discussed.

Intratemporal facial nerve hemangiomas.

Facial nerve hemangiomas are benign vascular tumors that arise within the temporal bone and have a histologic appearance similar to both cavernous hemangiomas and vascular malformations. In contrast to facial nerve schwannomas, these are extraneural tumors that cause symptoms by compression and tend to produce deficits when very small in size. We report our experience at the House Ear Clinic with 34 patients having these nonglomus intratemporal vascular tumors. Hemangiomas arising in the internal auditory canal tend to produce a progressive sensorineural hearing loss and are demonstrated with magnetic resonance imaging (MRI), whereas those at the geniculate ganglion are usually first seen with facial nerve symptoms and may require high-resolution computerized tomography (CT) for detection. Facial electromyography is helpful in establishing the diagnosis. Because of their extraneural nature, early diagnosis can permit removal of the tumor with preservation of facial nerves in some patients.

Adenomatous tumors of the middle ear and mastoid.

Adenomatous tumors of the middle ear and mastoid have been called adenoma or adenocarcinoma. The clinical and pathologic distinction between the two has been difficult. The resultant pathologic ambiguity makes it difficult to decide whether conservative or radical management is appropriate. The Otologic Medical Group's (OMG) experience with glandular tumors of the middle ear and mastoid over the past 27 years was reviewed. Thirteen cases were found and analyzed with respect to signs and symptoms at presentation. Extensive histopathologic review with light and electron microscopy was performed on tumor specimens. Two distinctive histopathologic and clinical patterns were identified. The mixed type of tumor was always confined to the middle ear and mastoid, was commonly misdiagnosed as chronic otitis media, and rarely demonstrated otic capsule or facial nerve involvement. The papillary pattern always had extension to the petrous apex and frequently involved the middle and/or posterior cranial fossa. Papillary tumors were more frequent in females and usually involved the facial nerve. On the basis of the findings in this review as well as information from the literature, we have come to the following conclusions: 1. The correct general pathologic heading be Adenomatous Tumors of the Middle ear and Mastoid with each tumor then being subclassified into Mixed or Papillary tumor and adenocarcinoma when warranted by histology. 2. There is a high rate of local recurrence. 3. Long-term follow-up (at least 10 years) for all adenomatous tumors is necessary. 4. Primary surgical treatment is required.

Intratemporal vascular tumors: detection with CT and MR imaging.

The diagnostic contributions of computed tomography (CT) and magnetic resonance (MR) imaging were compared in 12 patients with benign intratemporal vascular tumors (hemangioma or vascular malformation). The tumors included six in the internal acoustic canal and six in the geniculate ganglion region. Clinical and histologic correlations were made. Two of the six patients with tumors in the internal acoustic canal underwent CT, and both required gas cisternography to show the tumor. Five patients in that group underwent MR imaging, and all five studies showed the tumor. All six patients with geniculate ganglion tumors underwent CT. Results in one study were questionable, and five showed the tumor. Five patients in this group underwent MR imaging, but the MR findings were positive in only two cases. MR imaging should therefore be performed before CT in the evaluation of facial nerve dysfunction, as it demonstrated all tumors in the internal acoustic canal and some in the geniculate ganglion region. If MR findings are negative, CT should then be performed to rule out a possible geniculate ganglion lesion.

Intratemporal vascular tumors: evaluation with CT.

Eleven patients each with a benign intratemporal vascular tumor (hemangioma or vascular malformation) were assessed with computed tomography (CT). Clinical, surgical, and histologic correlations were also available. On CT scans, most of the 11 tumors were smaller than 10 mm. Four occurred in or around the internal acoustic canal, six at the geniculate ganglion, and one at the posterior genu. The involved bone margins were often unsharp, and "honeycomb" bone or intratumoral bone spicules were sometimes present. Intratemporal vascular tumors cause profound nerve deficits despite their small size and must be resected early to salvage nerve function.

Flocculation effects on bound water in sludges as measured by nuclear magnetic resonance spectroscopy.

Nuclear magnetic resonance relaxation times (T(1) and T(2)) were measured for flocculated and unflocculated samples of activated sludge. The weight of water and solids in the sludge samples was found and related to T(1) to find the relative percentage of bound water. The results suggest that the amount of bound water increases as the samples become more unflocculated. The values of T(1) and T(2) also indicate that unflocculated individual particles are characterized by loose packing of shorter molecules and that the addition of larger molecules may induce flocculation.

A mixed carcinoid tumour of the middle ear.

Carcinoid tumours belong to the rarest neoplasms of the middle ear. Murphy et al. (1980) described an interesting carcinoid tumour of the middle ear displaying adenomatous features. The histological similarity of carcinoid tumours to adenomatous tumours of the middle ear has also been noted by Fayemi and Toker (1975). We describe a similar case which caused certain diagnostic difficulties. Light microscopy on frozen sections favoured the diagnosis of a low-grade adenocarcinoma but electron microscopy has revealed the presence of many intracellular membrane-bound neurosecretory granules and the diagnosis was revised to that of a mixed carcinoid tumour.

Salivary gland choristoma of the middle ear.

Salivary gland choristoma (ectopic salivary gland tissue) is an unusual condition that occurs in various locations within the middle ear. It is a distinct histopathologic entity that should be differentiated from other epithelial lesions of the middle ear. Since the lesion commonly involves the facial nerve, its recognition is particularly critical to avoid unnecessary severing of the nerve.

Management of intratemporal vascular tumors.

Vascular tumors (vascular malformations and hemangiomas) of the temporal bone are uncommon, and guidelines for their management have not been published. In an effort to develop an approach to their management, the present study examined the pathological, clinical, and surgical experience with ten of these lesions treated at the Otologic Medical Group, Inc., and St. Vincent Medical Center in Los Angeles from 1960 to 1980. Intratemporal vascular tumors occurred most frequently at two sites, the internal auditory canal and the geniculate ganglion. Histological features and clinical behavior did not correlate. Both vascular malformations and hemangiomata invaded the facial nerve. Surgical excision in these cases required severence and repair of the involved facial nerve. Complete surgical excision is the treatment of choice of vascular lesions of the temporal bone.