Nasal Pressure Changes Research Articles

Comparing thoracic and intra-nasal pressure transients to monitor active odor sampling during odor-guided decision making in the mouse

BackgroundRecording of physiological parameters in behaving mice has seen an immense increase over recent years driven by, for example, increased miniaturization of recording devices. One parameter particularly important for odorant-driven behaviors is the breathing frequency, since the latter dictates the rate of odorant delivery to the nasal cavity and the olfactory receptor neurons located therein. New methodTypically, breathing patterns are monitored by either measuring the breathing-induced temperature or pressure changes in the nasal cavity. Both require the implantation of a nasal cannula and tethering of the mouse to either a cable or tubing. To avoid these limitations we used an implanted pressure sensor which reads the thoracic pressure and transmits the data telemetrically, thus making it suitable for experiments which require a freely moving animal. ResultsMice performed a Go/NoGo odorant-driven behavioral task with the implanted pressure sensor, which proved to work reliably to allow recording of breathing signals over several weeks from a given animal. Comparison to existing method(s)We simultaneously recorded the thoracic and nasal pressure changes and found that measuring the thoracic pressure change yielded similar results compared to measurements of nasal pressure changes. ConclusionTelemetrically recorded breathing signals are a feasible method to monitor odorant-guided behavioral changes in breathing rates. Its advantages are most significant when recording from a freely moving animal over several weeks. The advantages and disadvantages of different methods to record breathing patterns are discussed.

Complications associated with implant migration into the maxillary sinus cavity

Migration of dental implants into the maxillary sinus is an uncommon, but increasingly reported complication. Implant migration may result from initial lack of primary stability, intrasinusal and nasal pressure changes, autoimmune reaction to the implant or incorrect distribution of occlusal forces. This retrospective study aims at analyzing the factors that may influence implant migration into the maxillary sinus cavity. Fourteen patients presenting a total 15 implants that migrated into the maxillary sinus were recruited. Diagnosis of this complication was based on imaging techniques, such as cone beam computerized tomography scan and panoramic radiography. Clinical data were recorded in all cases and processed for statistical analysis. ABH was below 6 mm in the majority of cases. However, almost 50% of the patients did not receive any site preparation treatment prior to implant insertion. Five patients (33.3%) were treated by osteotome techniques, but only one of them had bone grafting. Therefore, 73.3% of sites did not receive any biomaterial to increase available bone height. The most common complication-associated factors found on this study were related to implant design (cylindrical), implant dimension (diameter), implant restoration/rehabilitation method (partial removable denture), site-specific anatomy (initial residual bone height between 5 and 6.9 mm), demographics (age), and biomaterials. Patient selection and proper treatment planning, as well as the application of the appropriate sinus augmentation technique, are critical aspects that should be controlled to minimize the risk of implant migration into the maxillary sinus cavity.

Sniffing enables communication and environmental control for the severely disabled

Paradoxically, improvements in emergency medicine have increased survival albeit with severe disability ranging from quadriplegia to "locked-in syndrome." Locked-in syndrome is characterized by intact cognition yet complete paralysis, and hence these individuals are "locked-in" their own body, at best able to communicate using eye blinks alone. Sniffing is a precise sensory-motor acquisition entailing changes in nasal pressure. The fine control of sniffing depends on positioning the soft palate, which is innervated by multiple cranial nerves. This innervation pattern led us to hypothesize that sniffing may remain conserved following severe injury. To test this, we developed a device that measures nasal pressure and converts it into electrical signals. The device enabled sniffs to control an actuator with speed similar to that of a hand using a mouse or joystick. Functional magnetic resonance imaging of device usage revealed a widely distributed neural network, allowing for increased conservation following injury. Also, device usage shared neural substrates with language production, rendering sniffs a promising bypass mode of communication. Indeed, sniffing allowed completely paralyzed locked-in participants to write text and quadriplegic participants to write text and drive an electric wheelchair. We conclude that redirection of sniff motor programs toward alternative functions allows sniffing to provide a control interface that is fast, accurate, robust, and highly conserved following severe injury.

Effect of end-expiratory lung volume on upper airway collapsibility in sleeping men and women.

The relationship between changes in absolute end-expiratory lung volume (EELV) and collapsibility has not been rigorously quantified. We hypothesized that pharyngeal collapsibility varies inversely with absolute lung volume in sleeping humans during 1) conventional and 2) isovolume measurements of passive critical pressure (Pcrit). Eighteen healthy subjects (11 male, 7 female) slept in a negative pressure ventilator for measurements of pharyngeal collapsibility (Pcrit) during non-rapid eye movement sleep. EELV was 1) allowed to vary with changes in nasal pressure for conventional Pcrit measurements and 2) controlled by maintaining a fixed pressure difference across the respiratory system (P(RS)) from the nose to the body surface for isovolume Pcrit measurements at elevated EELV (P(RS) = +10 cmH(2)O), reduced EELV (P(RS) = -5 cmH(2)O), and functional residual capacity (FRC; P(RS) = 0 cmH(2)O). In each condition, the absolute EELV was determined and the corresponding Pcrit was derived from upper airway pressure-flow relationships. In the entire group, Pcrit varied inversely with EELV (P < 0.001). Pcrit decreased as EELV increased from the conventional to the FRC isovolume condition by -3.5 ± 1.0 cmH(2)O/l (P < 0.003). Subjects with a conventional Pcrit below -2 cmH(2)O exhibited greater reductions in EELV and correspondingly greater decreases in the FRC isovolume compared with the conventional Pcrit (P < 0.001). The overall response, ΔPcrit/ΔEELV, was -2.0 ± 0.2 cmH(2)O/l (P < 0.001) and did not differ between men and women (P = 0.16). Nevertheless, men and women differed significantly in FRC (2.63 ± 0.16 vs. 1.88 ± 0.13 liters, P <0.05) and FRC isovolume Pcrit (-2.3 ± 0.8 vs. -7.2 ± 1.2 cmH(2)O, P < 0.05), implying that the men had larger lungs and more collapsible airways than the women. The ΔPcrit/ΔEELV response was independent of sex, conventional Pcrit, body mass index, and neck, waist, and hip circumferences. We conclude that Pcrit varies inversely with absolute EELV, which may lead to 1) an underestimation of the magnitude of quantitative differences in Pcrit across the spectrum from health (negative Pcrit) to disease (positive Pcrit) and 2) increases in sleep apnea susceptibility in obesity.

Das Flussolfaktometer nach Kobal im klinischen Einsatz für die subjektive und objektivierende Olfaktometrie

Is the flow-olfactometer OM2S suitable for subjective and objectifying screening of olfactory function, additional to its use for chemosensory evoked potentials? 53 normosmics were challenged prenasally and synchronously with inspiration by two short weak, moderate and strong hydrogen sulfide (H (2)S)- and phenylethyl alcohol (PEA)-stimuli. The subject pressed a button if there was an olfactory perception. The respiratory nasal pressure changes were recorded continuously via a differential pressure transducer. The alterations of breathing pattern during olfactory stimulation were calculated using a custom made LabView software. The interstimulus interval was at least 3 minutes, the respiration had to be regular. The detection-rate (79 - 98 %) was dependent on quality of odor and its concentration during stimulation. H (2)S-stimuli were detected more frequently than PEA-stimuli. The frequency of detection with simultaneous alteration of breathing pattern was independent of quality of odor and strength of odor concentration. 64 % of the subjects detected both weak H (2)S as well as changed synchronously their first poststimulatory breath. The H (2)S-detection threshold was estimated both by subjective data and by data of olfactory evoked respiration changes. The flow-olfactometer by Kobal is very well suitable for subjective and respiration-olfactometry, too.

A model of a snorer's upper airway

In snorers, the physiologic decrease of postural muscle tone during sleep results in increased collapsibility of the upper airway. Measurement of nasal pressure changes with prongs is increasingly used to monitor flow kinetics through a collapsing upper airway. This report presents a mathematical model to predict nasal flow profile from three critical components that control upper airway patency during sleep. The model includes the respiratory pump drive, the stiffness of the pharyngeal soft tissues, and the dynamic support of the muscles surrounding the upper airway. Depending on these three components, the proposed model is able to reproduce the characteristic changes in flow profile that are clinically observed in snorers and non-snorers during sleep.

Effect of positive nasal pressure on upper airway pressure-flow relationships.

To determine the influence of changes in nasal pressure (Pn) on airflow mechanics in the upper airway, we examined the effect of elevations in Pn on upper airway resistance and critical pressure (Pcrit) during stage I/II sleep in six patients with obstructive sleep apnea. When Pn was elevated above a Pcrit, periodic occlusions of the upper airway were eliminated and inspiratory airflow limitation was demonstrated by the finding that inspiratory airflow (VI) became maximal (VImax) and independent of fluctuations in hypopharyngeal pressure (Php) when Php fell below a specific Php (Php'). As Pn was elevated, VI vs. Php demonstrated 1) marked decreases in early and late inspiratory resistances from 75.9 +/- 34.7 and 54.6 +/- 19.0 to 8.0 +/- 1.7 and 7.6 +/- 1.6 cmH2O.l-1.s (P less than 0.05), respectively, and 2) increases in early and late inspiratory Php' to levels that exceeded Pcrit by 3.0 +/- 0.6 and 3.1 +/- 0.7 cmH2O, respectively, at the highest level of Pn applied (P less than 0.01). This latter finding suggests that elevations in Pn result in increases in Pcrit. We suggest that elevations in Pn produce distinct alterations in upper airway resistance and collapsibility, which may influence oppositely the level of airflow through the upper airway during sleep.

Nasal pressure changes during swallowing. A combined cineradiographic and manometric study.

From the Division of Diagnostic Radiology and Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, N. Y. *From the Division of Diagnostic Radiology and Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, N. Y.; Associate Professor of Medicine