Pitot-tube flowmeter for quantification of airflow during sleep

The gold-standard pneumotachograph is not routinely used to quantify airflow during overnight polysomnography due to the size, weight, bulkiness and discomfort of the equipment that must be worn. To overcome these deficiencies that have precluded the use of a pneumotachograph in routine sleep studies, our group developed a lightweight, low dead space 'pitot flowmeter' (based on pitot-tube principle) for use during sleep. We aimed to examine the characteristics and validate the flowmeter for quantifying airflow and detecting hypopneas during polysomnography by performing a head-to-head comparison with a pneumotachograph. Four experimental paradigms were utilized to determine the technical performance characteristics and the clinical usefulness of the pitot flowmeter in a head-to-head comparison with a pneumotachograph. In each study (1-4), the pitot flowmeter was connected in series with a pneumotachograph under either static flow (flow generator inline or on a face model) or dynamic flow (subject breathing via a polyester face model or on a nasal mask) conditions. The technical characteristics of the pitot flowmeter showed that, (1) the airflow resistance ranged from 0.065 ± 0.002 to 0.279 ± 0.004 cm H(2)O L(-1) s(-1) over the airflow rates of 10 to 50 L min(-1). (2) On the polyester face model there was a linear relationship between airflow as measured by the pitot flowmeter output voltage and the calibrated pneumotachograph signal a (β(1) = 1.08 V L(-1) s(-1); β(0) = 2.45 V). The clinically relevant performance characteristics (hypopnea detection) showed that (3) when the pitot flowmeter was connected via a mask to the human face model, both the sensitivity and specificity for detecting a 50% decrease in peak-to-peak airflow amplitude was 99.2%. When tested in sleeping human subjects, (4) the pitot flowmeter signal displayed 94.5% sensitivity and 91.5% specificity for the detection of 50% peak-to-peak reductions in pneumotachograph-measured airflow. Our data validate the pitot flowmeter for quantification of airflow and detecting breathing reduction during polysomnographic sleep studies. We speculate that quantifying airflow during sleep can differentiate phenotypic traits related to sleep disordered breathing.     

Fever management practices of neuroscience nurses: national and regional perspectives.

Neuroscience patients with fever may have worse outcomes than those who are afebrile. However, neuroscience nurses who encounter this common problem face a translational gap between patient-outcomes research and bedside practice because there is no current evidence-based standard of care for fever management of the neurologically vulnerable patient. The aim of this study was to determine if there are trends in national practices for fever and hyperthermia management of the neurologically vulnerable patient. A 15-item mailed questionnaire was used to determine national and regional trends in fever and hyperthermia management and decision making by neuroscience nurses. Members of the American Association of Neuroscience Nurses were surveyed (N = 1,225) and returned 328 usable surveys. Fewer than 20% of respondents reported having an explicit fever management protocol in place for neurologic patients, and 12.5% reported having a nonspecific patient protocol available for fever management. Several clear and consistent patterns in interventions for fever and hyperthermia management were seen nationally, including acetaminophen administration at a dose of 650 mg every 4 hours, ice packs, water cooling blankets, and tepid bathing. However, regional differences were seen in intervention choices and initial temperature to treat.     

Intracranial pressure waveform analysis: clinical and research implications.

Assessment of intracranial adaptive capacity is vital in critically ill individuals with acute brain injury because there is the potential that nursing care activities and environmental stimuli to result in clinically significant increases in intracranial pressure (ICP) in a subset of individuals with decreased intracranial adaptive capacity. ICP waveform analysis provides information about intracranial dynamics that can help identify individuals who have decreased adaptive capacity and are at risk for increases in ICP and decreases in cerebral perfusion pressure, which may contribute to secondary brain injury and have a negative impact on neurologic outcome. The ability to identify high-risk individuals allows nurses to initiate interventions targeted at decreasing adaptive demand or increasing adaptive capacity in these individuals. Changes in the ICP waveform occur under various physiologic and pathophysiologic conditions and may provide valuable information about intracranial adaptive capacity. Simple visual assessment of the ICP waveform for increased amplitude and P2 elevation is clinically relevant and has been found to provide a rough indicator of decreased adaptive capacity. Advanced ICP waveform analysis techniques warrant further study as a means of dynamically assessing intracranial adaptive capacity.     

Is there a sex difference in the course following traumatic brain injury?

Traumatic brain injury (TBI) is a significant cause of death and disability in the United States. Sex has not been thoroughly examined as a factor that may influence outcome following TBI. Clinical studies involving humans that have focused on sex and TBI outcome have yielded inconclusive results, yet sex-related physiologic differences have been demonstrated in animal studies. The purpose of this study is to examine the interaction of sex and age in relation to outcome at 3 and 6 months postinjury in a population of individuals with TBI. The sample includes 157 subjects (124 males, 33 females), 16 to 89 years of age, admitted to a level 1 trauma center following TBI. Physiologic data and information about injury severity and clinical course were gathered during hospitalization. Outcome was assessed at 3 and 6 months postinjury using the Extended Glasgow Outcome Scale (GOSE) and Functional Status Examination (FSE). In this sample, there was a significant relationship between sex and age with respect to functional outcome at 6 months following TBI, controlling for initial injury severity. Females age 30 years or older had significantly poorer outcome as measured by the GOSE (P = 0.031) and the FSE (P = 0.037) than either males or younger females. There was also a very different rate of recovery, with women age 30 years and older, on average, showing no improvement between 3 and 6 months postinjury. Further study is needed to elucidate the reasons why sex may affect outcome following TBI.     

A mutation in the canine BHD gene is associated with hereditary multifocal renal cystadenocarcinoma and nodular dermatofibrosis in the German Shepherd dog

Hereditary multifocal renal cystadenocarcinoma and nodular dermatofibrosis (RCND) is a naturally occurring canine kidney cancer syndrome that was originally described in German Shepherd dogs. The disease is characterized by bilateral, multifocal tumors in the kidneys, uterine leiomyomas and nodules in the skin consisting of dense collagen fibers. We previously mapped RCND to canine chromosome 5 (CFA5) with a highly significant LOD score of 16.7 (theta=0.016). We have since narrowed the RCND interval following selection and RH mapping of canine genes from the 1.3 x canine genome sequence. These sequences also allowed for the isolation of gene-associated BACs and the characterization of new microsatellite markers. Ordering of newly defined markers and genes with regard to recombinants localizes RCND to a small chromosomal region that overlaps the human Birt-Hogg-Dubé locus, suggesting the same gene may be responsible for both the dog and the phenotypically similar human disease. We herein describe a disease-associated mutation in exon 7 of canine BHD that leads to the mutation of a highly conserved amino acid of the encoded protein. The absence of recombinants between the disease locus and the mutation in US and Norwegian dogs separated by several generations is consistent with this mutation being the disease-causing mutation. Strong evidence is provided that the RCND mutation may have a homozygous lethal effect (P<0.01).     

Residual debris as a potential cause of postphacoemulsification endophthalmitis

AIM: To examine residual debris within sterilised instruments prior to cataract surgery. METHODS: (i) Flushings from 32 sets of phacoemulsification instruments, sterilised according to hospital routine protocols, were taken preoperatively and analysed by scanning electron microscopy (SEM). (ii) A total of 16 sets of flushings from a different institute were collected-with separation of samples collected from phacoemulsification and those from irrigation-aspiration (IA) instruments-and analysed in the same way. (iii) A total of 15 sets of flushings were collected from instruments where an automated flushing system was used prior to sterilisation. RESULTS: (i)In the first study, 62% were clean, 16% were moderately contaminated and 22% were severely contaminated. Various contaminants were identified including lens capsule and cells, man-made fibres, squamous cells, bacteria, fungal elements, diatoms, red blood cells and proteinaceous material. (ii) In the second study, the results were similar and contamination of both phacoemulsification and IA instruments was shown. (iii) The third study showed that although a decrease in contamination followed automated flushing, contamination was not completely eliminated. CONCLUSIONS: Although all equipment had been sterilised, pyrogenic material was still present. These findings emphasise the importance of meticulous cleaning of all surgical equipment in which biological debris can remain.     

Amnionless function is required for cubilin brush-border expression and intrinsic factor-cobalamin (vitamin B12) absorption in vivo

Amnionless (AMN) and cubilin gene products appear to be essential functional subunits of an endocytic receptor called cubam. Mutation of either gene causes autosomal recessive Imerslund-Gr?sbeck syndrome (I-GS, OMIM no. 261100) in humans, a disorder characterized by selective intestinal malabsorption of cobalamin (vitamin B12) and urinary loss of several specific low-molecular-weight proteins. Vital insight into the molecular pathology of I-GS has been obtained from studies of dogs with a similar syndrome. In this work, we show that I-GS segregates in a large canine kindred due to an in-frame deletion of 33 nucleotides in exon 10 of AMN. In a second, unrelated I-GS kindred, affected dogs exhibit a homozygous substitution in the AMN translation initiation codon. Studies in vivo demonstrated that both mutations abrogate AMN expression and block cubilin processing and targeting to the apical membrane. The essential features of AMN dysfunction observed in vivo are recapitulated in a heterologous cell-transfection system, thus validating the system for analysis of AMN-cubilin interactions. Characterization of canine AMN mutations that cause I-GS establishes the canine model as an ortholog of the human disorder well suited to studies of AMN function and coevolution with cubilin.