Exhaled air dispersion and removal is influenced by isolation room size and ventilation settings during oxygen delivery via nasal cannula

Background and objective: We compared the exhaled air dispersion distances during oxygen delivery via nasal cannula to a human‐patient simulator (HPS) in two different isolation rooms. Methods: Airflow was marked with intrapulmonary smoke for visualization. Oxygen flow was gradually increased from 1 to 5 L/min, with the HPS sitting at 45°. The leakage jet plume was revealed by laser light‐sheet and images captured by high‐definition video. Smoke concentration in the plume was estimated from the light scattered by smoke particles. The experiments were conducted at a double‐door, negative pressure isolation room with a dimension of 4.1 × 5.1 × 2.6 m, pressure of ?7.4 Pa and 16 air exchanges/h (ACH) (room A). Results were compared with experiments repeated in a smaller isolation room with a dimension of 2.7 × 4.2 × 2.4 m, pressure of ?5 Pa and 12 ACH (room B). Results: Room A: an exhalation jet spread almost horizontally outward from the nostrils of the HPS to 0.66 m and 1 m towards the end of bed when oxygen flow was increased from 1 to 5 L/min respectively. Room B: there was interaction between the downward ceiling ventilation current and the exhaled air from the HPS, leading to deflection of exhaled smoke towards the head of the HPS at an oxygen flow rate of 1 L/min. As oxygen flow was increased gradually to 5 L/min, more room contamination with smoke was noted. Conclusions: Substantial exposure to exhaled air occurs within 1 m towards the end of the bed from patients receiving oxygen via nasal cannula. Room dimension and air exchange rate are important factors in preventing contamination in isolation rooms.     

带管导光在硅油注入手术中的应用

目的 观察和评估带管导光在硅油／液体交换硅油注入术临床效果。方法 对35例（35只眼）在行硅油／液体交换硅油注入时，应用带抽吸管导光行导光和抽吸操作，将其尾部软管与玻切机的抽吸管道相连，抽吸玻璃体腔液体，同时助手借助硅油助推器经20G静脉穿刺套管将硅油逐渐注入玻璃体腔内。结果 35眼实施硅油注入手术，减少了硅油注入时的阻力，具有注入过程顺畅便捷，油／液交换彻底，眼内压可控性好。木中出现医源性视网膜裂孔2例，眼内压过高1例，无晶状体损伤、眼内出血、脉络膜脱离等并发症。结论 带管导光及静脉穿刺套管在硅油注入中应用安全，有效，并发症少。     

The effect of draw-up volume on the accuracy of electrolyte measurements from neonatal arterial lines

OBJECTIVES: Contamination by infusate of blood samples withdrawn from arterial lines has been recognized but not well documented for neonates. The aim of this study was to investigate, using in vitro and in vivo studies, the effects of different draw-up volumes (withdrawn from the line prior to the sample being taken) on the concentration of sodium. METHODS: In-vitro study: The tip of an umbilical artery catheter (dead space 0.6 mL), infused with half normal saline containing 1 unit/mL of heparin was placed in a beaker of normal saline. The line was flushed with 1 mL of this infusate just before each sample was taken. Volumes from 0.5 mL to 2.0 mL of infusate/normal saline were withdrawn in 0.1 mL increments from a three-way tap and discarded. A sample was then taken from the line into a blood gas syringe for analysis of the sodium concentration by the 860 Blood Gas Analyzer (Chiron Diagnostics, Bayer, Scoresby). Control samples were taken from the beaker. In-vivo study: A 22 gauge intravenous catheter was inserted into a vein of an adult male volunteer. The dead space was also 0.6 mL. The line was flushed with 5 mL of half-normal saline immediately before sampling. Draw-up volumes of 0.6, 0.9, 1.3, and 1.6 mL were withdrawn and discarded. 10 mL was used as a control. A 0.5-mL blood sample was then taken and the electrolyte concentrations analysed immediately. RESULTS: In-vitro: A minimum draw-up volume of 1.3 mL was required before the sodium concentration was not significantly different from the control samples. In-vivo: A minimum draw-up volume of 1.6 mL was required before the sodium concentration was not significantly different from the control samples. There were similar trends in the effect of draw-up volume for glucose, calcium, potassium, chloride and lactate. CONCLUSION:: A minimum volume of 1.6 mL should be withdrawn from neonatal arterial lines (dead space 0.6 mL) before taking blood for analysis.     

Pulsatile release of catecholamines in the hypothalamus of conscious rats

Summary To investigate the patterns of catecholamine release in the brain, the hypothalamus of conscious, freely moving rats was superfused through a push-pull cannula with artificial cerebrospinal fluid and the catecholamines dopamine, noradrenaline and adrenaline were determined in the superfusate radioenzymatically. Superfusate was continuously collected in time periods of 20 min for at least 20h. Dopamine, noradrenaline and adrenaline release rates fluctuated according to an ultradian rhythm with a frequency of 1 cycle/92 min (dopamine and noradrenaline) or 99 min (adrenaline). Additionally, the three catecholamines were released according to an ultradian rhythm with the following frequencies: noradrenaline and adrenaline 1 cycle/ 12 h, dopamine 1 cycle/8 h. The release rates of dopamine and adrenaline were similar during light and dark periods, while the release rate of noradrenaline in the dark period was slightly lower than that during the light period. It is concluded that in the hypothalamus of the conscious rat the release rates of dopamine, noradrenaline and adrenaline fluctuate according to two ultradian rhythms with different frequencies.This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds zur Förderung der wissenschaftlichen ForschungParts of this work have been presented at the 29th Spring Meeting of the German Society of Pharmacology and Toxicology, 1988 and at the 12th Annual Meeting of the European Neuroscience Association, 1989Correspondence to H. Prast at the above address     

Failure of isoprenaline and beta-receptor blocking drugs to modify depressor response and bradycardia induced by electrical stimulation of the anterior hypothalamus of cats

Summary The role of the hypothalamic betaadrenoceptors in the depressor response and bradycardia induced by stimulation of the anterior hypothalamus was studied in cats. In chloralose and urethane anaesthetized cats the anterior hypothalamus was superfused with artifical cerebrospinal fluid through a push-pull cannula. Electrical stimulation of the anterior hypothalamus with the tip of the cannula elicited a fall of systemic blood pressure and a decrease in heart rate. Superfusion of the anterior hypothalamus with isoprenaline did not change the depressor response and bradycardia induced by electrical stimulation of the anterior hypothalamus. Superfusion with atenolol or butoxamine also failed to modify the responses. Superfusion with (±)-propranolol significantly suppressed the responses. However, superfusion with (+)-propranolol suppressed the responses to the same extent. The resting systemic blood pressure and heart rate were not significantly changed by superfusion of the hypothalamus with these drugs. These results suggest that beta-adrenoceptors of the anterior hypothalamus are not involved in the depressor response and bradycardia elicited by hypothalamic stimulation.This work was supported by the Deutsche Forschungsgemeinschaft     

Glass-plastic push-pull cannula system for regional perfusion of sites in the brain

A new non-metallic push-pull cannula device is described for the localized perfusion of brain sites in the rat or other animal. Comprised entirely of glass and plastic materials, the cannula is intended for usage in an experiment in which the presence in tissue of metal tubing for delivery of perfusate is methodologically inappropriate. The main features of the cannula include its light weight, a Delrin pedestal base, a micro-glass guide tube, a polyethylene stylet, plastic spacers for adjustment of depth of perfusion, a protective cap for the chronic maintenance of the preparation, low cost and re-usability. The push-pull cannula is of concentric design and is fashioned from glass capillary and polyethylene tubing which are bonded at their common junctions by an epoxy cement. During a push-pull perfusion a special perfusion cap is used not only to hold the cannula firmly in place but also to protect the glass components from external damage. To further coincide with the metal-free requirements of the preparation, bone screws of nylon are used during the surgical implantation of the pedestal base. A prototype experiment illustrating its use in an unrestrained animal also is presented. The special applications for this cannula system are discussed which include its usage in experiments in either the anesthetized or unanesthetized rat exposed to microwave radiation where the presence of metal in the field would result in unwanted 'hot spots' in the cerebral tissue.     

A chronically implantable arterial catheter for use in unrestrained small animals

An easily constructed arterial catheter was designed for use in experiments requiring serial blood sampling from conscious, free-moving animals (Fischer 344 rat). It can be implanted chronically, at least several days before use, into the femoral artery, without interference of movement or damage by the animal. The catheter assembly is worn subdermally until the distal portion is exteriorized for blood sampling. The proximal tip of the catheter is occluded with a removable plug before implantation, thereby eliminating the necessity of daily flushing prior to use. The catheter has been used extensively in studies of the blood-brain barrier involving the bolus injection of [14C]sucrose into the jugular vein of conscious, unrestrained rats. Tracer concentration in plasma and whole blood was subsequently determined from arterial blood samples collected serially over a 20-min period following injection of the tracer.     

Culdoscopy using an optical cannula

OBJECTIVE: To describe a technique for inserting an endoscope through the posterior vaginal fornix under direct vision using an optical cannula.DESIGN: Prospective case study.SETTING: University Department of Obstetrics & Gynecology.PATIENT(S): Patients with infertility referred for investigation in secondary care.INTERVENTION(S): Insertion of culdoscope using an optical cannula.MAIN OUTCOME MEASURE(S): Successful introduction of the culdoscope.RESULT(S): Sixteen of 20 patients had successful introduction of the optical cannula. There were no reported complications.CONCLUSION(S): Insertion of a culdoscope into the cul-de-sac can be done under visual control and this may reduce the risks of complications associated with blind insertion using a modified Veress needle.     

儿童经鼻高流量氧疗呼吸支持早期失败的高危因素分析

目的 探讨急性呼吸功能不全患儿经鼻高流量氧疗（HFNC）早期失败的高危因素。方法 回顾性分析2018年1~6月入住儿童重症监护室的123例行HFNC呼吸支持的急性呼吸功能不全患儿的临床资料。将住院期间无需升级呼吸支持方式，且成功撤离HFNC的患儿归为HFNC成功组（69例）；其余患儿在住院期间需升级呼吸支持方式（54例），其中使用HFNC 48 h内升级呼吸支持方式的患儿归为HFNC早期失败组（46例）。采用多因素logistic回归分析评估分析HFNC早期失败的危险因素。结果 HFNC早期失败组罹患休克、脓毒症、颅内高压综合征或多器官功能障碍综合征的比例显著高于HFNC成功组（P < 0.05）。早期失败组实施呼吸支持前的格拉斯哥昏迷评分、pH值、氧合指数均显著低于HFNC成功组（P < 0.05），而小儿死亡风险评分（PRISM评分）、PaCO₂/PaO₂比值显著高于HFNC成功组（P < 0.05）。多因素logistic回归分析显示，PRISM评分 > 4.5分和PaCO₂/PaO₂比值 > 0.64是HFNC早期失败的独立危险因素（OR分别为5.535、9.089，P < 0.05）。结论 PRISM评分 > 4.5分或PaCO₂/PaO₂比值 > 0.64的急性呼吸功能不全患儿行HFNC早期失败的风险较高。     

DIFFERENTIAL BLOCKING EFFECTS OF TETRODOTOXIN ON DOUBLE-PEAKED VASOCONSTRICTOR RESPONSES TO PERIARTERIAL NERVE STIMULATION IN CANINE ISOLATED, PERFUSED SPLENIC ARTERY

1. In the present study, we investigated the effects of progressive inhibition of neuronal sodium channels by increasing concentrations of tetrodotoxin (TTX; 1-30 nmol/L) on the double-peaked vasoconstrictor responses to electrical periarterial nerve stimulation in the canine isolated and perfused splenic artery. 2. Double-peaked vasoconstrictions (biphasic vasoconstrictor responses) were consistently observed in following electrical stimulation with 30 s trains of pulses at 1-10 Hz. At low frequencies of stimulation (1-3 Hz), a submaximal concentration of 3 nmol/L TTX had no effect on the first phase of the contractile response, but almost completely inhibited the second-phase response. At high frequencies (6-10 Hz), the two vasoconstrictor phases were almost equally inhibited by 50% by 3 nmol/L TTX. A three-fold increase in the concentration of TTX used (10 nmol/L) abolished the second-phase vasoconstriction at all stimulation frequencies tested, whereas this concentration of TTX failed to block the first-phase response. Further increasing the concentration of TTX to 30 nmol/L completely blocked the remaining first-phase response. 3. Treatment with 0.1 mumol/L prazosin did not modify the first-phase response to any of the stimulation frequencies in the presence of 3 nmol/L TTX. Moreover, 0.1 mumol/L prazosin had no affect on the second-phase response at low frequencies (1-3 Hz), while at high frequencies (6-10 Hz) it slightly, but significantly inhibited the second-phase response. The vasoconstrictor responses that persisted after 3 nmol/L TTX and 0.1 mumol/L prazosin were completely suppressed by subsequent application of 1 mumol/L alpha, beta-methylene ATP at all stimulation frequencies (1-10 Hz). 4. In conclusion, progressive inhibition of sodium channels by increasing the concentration of TTX may exert a more preferential inhibition on adrenergic rather than purinergic components, suggesting that TTX-sensitive sodium channels may have a more important role in determining the adrenergic rather than purinergic transmission of sympathetic nerves.