What is the best way of delivering virtual nature for improving mood? An experimental comparison of high definition TV, 360° video, and computer generated virtual reality.

Exposure to 'real' nature can increase positive affect and decrease negative affect, but direct access is not always possible, e.g. for people in health/care settings who often experience chronic boredom. In these settings 'virtual' forms of nature may also have mood-related benefits (e.g. reducing boredom) but it has been difficult to separate effects of nature content from those of delivery mode. The present laboratory-based study explored whether exposure to three different delivery modes of virtual nature could reduce negative affect (including boredom) and/or increase positive affect. Adult volunteer participants (n = 96) took part in a boredom induction task (to simulate the emotional state of many people in health/care settings) before being randomly assigned to view/interact with a virtual underwater coral reef in one of three experimental conditions: (a) 2D video viewed on a high-definition TV screen; (b) 3600 video VR (360-VR) viewed via a head mounted display (HMD); or (c) interactive computer-generated VR (CG-VR), also viewed via a HMD and interacted with using a hand-held controller. Visual and auditory content was closely matched across conditions with help from the BBC's Blue Planet II series team. Supporting predictions, virtual exposure to a coral reef reduced boredom and negative affect and increased positive affect and nature connectedness. Although reductions in boredom and negative affect were similar across all three conditions, CG-VR was associated with significantly greater improvements in positive affect than TV, which were mediated by greater experienced presence and increases in nature connectedness. Results improve our understanding of the importance of virtual nature delivery mode and will inform studies in real care settings.

Regional chest wall impedance during nonrespiratory maneuvers.

To assess changes in total and regional chest wall properties during nonrespiratory maneuvers, we measured electromyographic activity of various chest wall muscles, esophageal pressure, and rib cage and abdominal surface displacements in six subjects before and during various static tasks. Subjects were seated at functional residual capacity, and quasi-sinusoidal forcing at the mouth (0.4 Hz, 500 ml) was imposed during the maneuver in the absence of active breathing. Magnitude of total chest wall impedance (magnitude of Zw) increased with effort during all maneuvers; changes in phase were small. Maneuvers involving primarily muscles of the neck and rib cage--holding a 10-kg weight, 10 kg of isometric tension between the arms, and isometric neck flexion--roughly doubled the magnitude of rib cage impedance (magnitude of Zrc) and, to a lesser degree, increased magnitude of diaphragm-abdomen impedance (magnitude of Zd-a). Unilateral and bilateral leg lifts, in addition to increasing magnitude of Zd-a, increased magnitude of Zrc. Passive 90 degrees rotation of the torso caused approximately 25% increases in magnitude of Zrc and magnitude of Zd-a; if the rotation was actively maintained by the trunk muscles, both regional impedances increased over 100%. Increases in magnitude of regional impedance were correlated to increases in regional electromyographic activity; changes in phase were small. Passive restriction of rib cage displacement by strapping increased magnitude of Zrc and magnitude of Zw but not magnitude of Zd-a, whereas abdominal strapping increased magnitude of Zd-a but did not affect magnitude of Zrc or magnitude of Zw.(ABSTRACT TRUNCATED AT 250 WORDS)

Tetrodotoxin infusion: nonventilatory effects and role in toxicity models.

OBJECTIVES: To determine the cardiovascular, autonomic, and neuromuscular effects of an IV infusion of tetrodotoxin (TTX) when ventilation is supported. METHODS: TTX was infused in 18 anesthetized beagles during conventional mechanical ventilation. TTX infusion continued at a rate of 9.3 micrograms/kg/hr until apnea occurred with 1 minute of ventilator disconnection. Measurements included intravascular pressures, heart rate (HR), cardiac output, blood gases, displacements of the rib cage and abdomen, O2 delivery, and responses to train-of-four and tetanic peripheral nerve stimulation. Results are expressed as mean +/- SD. RESULTS: During TTX infusion, all the dogs had discoordinate movements of the rib cage, abdomen, and limbs. Vomiting, urination, defecation, and increased salivation occurred. Nicotinic and muscarinic effects, neuromuscular blockade, and cardiovascular depression were produced by TTX. Apnea occurred in 72.0 +/- 17.0 minutes when a total of 119.0 +/- 17.4 micrograms of TTX was infused. At apnea, decreases in arterial pressure, cardiac index, HR, O2 delivery, and systemic vascular resistance occurred, while pulmonary artery pressure and pulmonary vascular resistance increased. Loss of response to tetanic stimulation was closely correlated with the dose of TTX that produced apnea. CONCLUSION: The clinical symptoms and signs of TTX poisoning are similar to those of anticholinesterase poisons, and TTX dosing as described by this model may serve as a surrogate for organophosphorus poisoning. The model may be useful to determine optimum therapies for TTX poisoning and, since TTX prevents sodium influx into cells, to investigate enhanced survival in animals suffering from ischemia.

Molar growth yields as evidence for oxidative phosphorylation in Streptococcus faecalis strain 10Cl.

During the aerobic growth of Streptococcus faecalis strain 10C1, with limiting levels of glucose as the substrate, a molar growth yield (Y) of 58.2 g (dry weight) per mole of glucose was obtained. Under these conditions of growth, glucose was dissimilated primarily to acetate and CO(2). The incorporation of (14)C-glucose into cell material was no greater under aerobic conditions than during anaerobic growth. Assuming an adenosine triphosphate coefficient of 10.5, the aerobic Y cannot be explained solely on the basis of substrate phosphorylation and would appear to substantiate previous enzymatic evidence for oxidative phosphorylation in this cytochromeless species. With mannitol as the substrate, an aerobic Y of 64.6 was obtained. Extracts of mannitol-grown cells contained a nicotinamide adenine dinucleotide (NAD)-linked mannitol-1-phosphate (M-1-P) dehydrogenase. The difference in aerobic Y values with mannitol and glucose as substrates would indicate that the in vivo P/O ratio from the oxidation of reduced NAD generated by the oxidation of M-1-P approximates 0.6. The Y values with pyruvate and glycerol as substrates under aerobic conditions were 15.5 and 24.7, respectively.

Efficacy of several modes of continuous-flow insufflation for resuscitation of a canine model of acute respiratory arrest.

STUDY OBJECTIVE: To test the efficacy of several modes of continuous-flow insufflation on the maintenance of physiologic parameters in a model of respiratory arrest, and the effect of these modes on neurologic outcome. METHODS: Anesthetized dogs were slowly infused with tetrodotoxin over 75 minutes to the point of respiratory arrest. We used two different modes of continuous-flow insufflation: endobronchial insufflation (EI) of air 3 cm distal to the carina (.25 or 1.0 L.kg-1.min-1); and tracheal insufflation of oxygen (TRIO) 1 cm proximal to the carina (.08 or .2 L.kg-1.min-1). RESULTS: EI at either flow rate provided ventilation sufficient to allow the dogs to recover effective spontaneous breathing and be removed from ventilation after 4 hours. By this time, almost all cardiovascular variables and blood gas values were normal. TRIO at .2 L.kg-1.min-1 also resulted in successful recovery, although Pa02, as well as systemic and pulmonary arterial pressures and vascular resistances, remained increased at the end of the 4-hour period. TRIO at the low flow rate, however, resulted in deterioration of blood gas values and systemic arterial pressure; dogs required conventional mechanical ventilation after 45 minutes of low-flow TRIO. CONCLUSION: EI can be used to maintain oxygenation in acute respiratory arrest when conventional techniques are not feasible; TRIO at .2 L.kg-1.min-1 is also effective.

Effects of analysis method and forcing waveform on measurement of respiratory mechanics.

The respiratory system has been shown to exhibit nonlinear mechanical properties in the frequency (f) range of normal breathing, manifested by tidal volume (Vt) dependence. Calculations of respiratory system resistance (R) and elastance (E) from pressure-flow measurements during external forcing at a given f may be ambiguous, especially if non-sinusoidal forcing waveforms are used. We evaluated the degree to which R and E depended upon: (1) analysis method (Fourier transform, multiple regression and pressure-volume loop analysis) and; (2) shape of the forcing waveform (sinusoidal, quasi-sinusoidal and step). We measured pressure and flow at the mouth of 5 healthy, awake subjects, relaxed at functional residual capacity, during forcing with the three different waveforms in the normal range of f (0.2-0.6 Hz) and Vt (250-750 ml). During sinusoidal forcing, E and R were not affected by analysis method (P greater than 0.2). With Fourier transform and multiple regression, E was not affected by waveform shape (P greater than 0.05); with loop analysis, E was slightly (less than 10%) higher during quasi-sinusoidal and step forcing than during the sine (P less than 0.05). R was least affected by waveform shape with Fourier transform. We conclude that, in the f and Vt range of normal breathing: (1) respiratory system impedance is 'quasi-linear,' i.e. despite dependencies of R and E on Vt, non-linearities are not large enough to restrict interpretation of R and E at a given f and Vt; (2) it may be possible to measure R and E using non-sinusoidal forcing waveforms available on most clinical ventilators, incurring only modest error.