Effectiveness of a novel semi-closed barrier device with a personalized exhaust in cough aerosol simulation according to particle counts and visualization of particles.

Oxygen therapy is an essential treatment for patients with coronavirus disease 2019, although there is a risk of aerosolization of additional viral droplets occurring during this treatment that poses a danger to healthcare professionals. High-flow oxygen through nasal cannula (HFNC) is a vital treatment bridging low-flow oxygen therapy with tracheal intubation. Although many barrier devices (including devices without negative pressure in the barrier) have been reported in the literature, few barrier devices are suitable for HFNC and aerosol infection control procedures during HFNC have not yet been established. Hence, we built a single cough simulator model to examine the effectiveness of three protective measures (a semi-closed barrier device, a personalized exhaust, and surgical masks) administered in isolation as well as in combination using particle counter measurements and laser sheet visualization. We found that the addition of a personalized exhaust to a semi-closed barrier device reduced aerosol leakage during HFNC without negative pressure. This novel combination may thus reduce aerosol exposure during oxygen therapy, enhance the protection of healthcare workers, and likely reduce nosocomial infection risk.

Variations in respiratory excretion of carbon dioxide can be used to calculate pulmonary blood flow.

BACKGROUND: A non-invasive means of measuring pulmonary blood flow (PBF) would have numerous benefits in medicine. Traditionally, respiratory-based methods require breathing maneuvers, partial rebreathing, or foreign gas mixing because exhaled CO2 volume on a per-breath basis does not accurately represent alveolar exchange of CO2. We hypothesized that if the dilutional effect of the functional residual capacity was accounted for, the relationship between the calculated volume of CO2 removed per breath and the alveolar partial pressure of CO2 would be reversely linear. METHODS: A computer model was developed that uses variable tidal breathing to calculate CO2 removal per breath at the level of the alveoli. We iterated estimates for functional residual capacity to create the best linear fit of alveolar CO2 pressure and CO2 elimination for 10 minutes of breathing and incorporated the volume of CO2 elimination into the Fick equation to calculate PBF. RESULTS: The relationship between alveolar pressure of CO2 and CO2 elimination produced an R(2) = 0.83. The optimal functional residual capacity differed from the "actual" capacity by 0.25 L (8.3%). The repeatability coefficient leveled at 0.09 at 10 breaths and the difference between the PBF calculated by the model and the preset blood flow was 0.62 ± 0.53 L/minute. CONCLUSIONS: With variations in tidal breathing, a linear relationship exists between alveolar CO2 pressure and CO2 elimination. Existing technology may be used to calculate CO2 elimination during quiet breathing and might therefore be used to accurately calculate PBF in humans with healthy lungs.

A short period of fasting before surgery conserves basal metabolism and suppresses catabolism according to indirect calorimetry performed under general anesthesia.

It is recommended that the period of fasting before elective surgery should be shortened to facilitate a rapid recovery by preventing catabolism. We examined the effects of a short period of fasting on metabolism by performing indirect calorimetry (IC) under general anesthesia. A prospective observational study involving 26 consecutive patients who underwent elective surgery and whose metabolism was evaluated using IC during anesthesia was conducted. The patients were divided into two groups, those who fasted for <8 h (group S) and those who fasted for >10 h (group L). Oxygen consumption, the volume of carbon dioxide emissions (VCO2), the respiratory quotient (RQ), resting energy expenditure (REE), and basal energy expenditure (BEE) were compared. The REE, VCO2, and RQ of group L (17.7 ± 2.3 kcal/kg/day, 118.5 ± 20.8 ml/min, and 0.71 ± 0.12, respectively) were significantly lower than those of group S (19.7 ± 2.3 kcal/kg/day, 143.6 ± 30.9 ml/min, and 0.81 ± 0.09, respectively) (P < 0.05). In group L, the relationship between REE and BEE was weaker (r(2) = 0.501) and the BEE-REE slope was less steep (REE = 0.419BEE + 509.477) than those seen in group S (r(2) = 0.749 and REE = 1.113BEE - 376.111, respectively). Our findings suggest that a short period of fasting (<8 h) before surgery is more strongly associated with the conservation of basal metabolism.

Spinal cord stimulation for a woman with complex regional pain syndrome who wished to get pregnant.

A woman with complex regional pain syndrome (CRPS) in the right lower extremity who wished to discontinue medications to get pregnant underwent implantation of a spinal cord stimulation system (SCS). An electrode lead was placed at Th(10-11) in the epidural space, accessed via the L(2-3) interspace with a paramedian approach, and a pulse generator was implanted in the left buttock. She kept the SCS on 24 h a day. After she had experienced several chemical abortions, finally she got pregnant via artificial insemination. She had an uneventful delivery of a healthy baby by cesarean resection under spinal anesthesia. In a patient with CRPS who has an implanted SCS system and wishes to get pregnant, the electrode lead into the low thoracic epidural space should be accessed via the high lumbar intervertebral space in consideration of a future requirement for spinal or epidural anesthesia for cesarean section. The generator should be placed in the buttock to prevent impairment of the SCS system being caused by the enlarged abdomen during pregnancy. Although we were apprehensive of adverse effects owing to the electromagnetic field force and change of blood flow in the pelvic viscera, our patient had a successful delivery. SCS is a favorable option for patients with CRPS who wish to get pregnant.

A new enteral diet, MHN-02, which contains abundant antioxidants and whey peptide, protects against carbon tetrachloride-induced hepatitis.

BACKGROUND: Inflammatory or oxidative stress is related to various diseases, including not only inflammatory diseases, but also diabetes, cancer, and atherosclerosis. The aim of this study was to evaluate the anti-inflammatory effects of a new enteral diet, MHN-02, which contains abundant antioxidants and whey peptide. The study also investigated the ability of MHN-02 to attenuate lethality, liver injury, the production of inflammatory cytokines, and the production of oxidized products using a carbon tetrachloride-induced rat model of severe fulminant hepatitis. METHODS: Male Sprague-Dawley rats were fed either a control diet or the MHN-02 diet for 14 days and injected with 2 mL/kg of carbon tetrachloride. Survival of rats was monitored from day 0 to day 3. To evaluate liver injury, inflammation, and oxidative stress, blood and liver samples were collected, and aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, interleukin 6, tumor necrosis factor-α, and superoxide dismutase activity as a free radical scavenger were measured. A portion of the liver was evaluated histologically. RESULTS: The survival rates of rats receiving the MHN-02 diet and the control diet were 90% and 55%, respectively. In the MHN-02 diet group, levels of serum liver enzymes and serum cytokines were significantly lower than in the control group. Superoxide dismutase activity in the MHN-02 diet was significantly higher in the MHN-02 group. Pathological lesions were significantly larger in the control group. CONCLUSION: Supplementation of enteral diets containing whey peptide and antioxidants may protect against severe hepatitis.

Severe hyponatremia occurring after surgical stress in a patient with mitochondrial disease.

A 53-year-old man with mitochondrial disease underwent gastrectomy because of gastric cancer. Three days after the surgery, he developed severe hyponatremia (Na, 106 mmol l(-1)) together with hypovolemic shock and lactic acidosis. Despite the hyponatremia, his urine sodium concentration was high, suggesting renal salt wasting. Although mitochondrial diseases are not common and hyponatremia in patients with these diseases is not well known, clinicians should pay close attention to serum sodium levels and maintain them properly.

A novel skin-traction method is effective for real-time ultrasound-guided internal jugular vein catheterization in infants and neonates weighing less than 5 kilograms.

BACKGROUND: Internal jugular vein (IJV) catheterization in pediatric patients is sometimes difficult because of the small sizes of veins and their collapse during catheterization. To facilitate IJV catheterization, we developed a novel skin-traction method (STM), in which the point of puncture of the skin over the IJV is stretched upward with tape during catheterization. In this study, we examined whether the STM increases the cross-sectional area of the vein and thus facilitates catheterization. METHODS: This was a prospective study conducted from December 2006 to June 2008. We enrolled 28 consecutive infants and neonates weighing <5 kg who underwent surgery for congenital heart disease. The patients were randomly assigned to a group in which STM was performed (STM group) or a group in which it was not performed (non-STM group). The cross-sectional area and diameter of the right IJV in the flat position and 10 degrees Trendelenburg position with and without applying STM were measured. We determined time from first skin puncture to the following: (a) first blood back flow, (b) insertion of guidewire, and (c) insertion of catheter. Number of punctures, success rate, complications, and degree of IJV collapse during advancement of the needle (estimated as decrease of anteroposterior diameter during advancement of the needle compared with the diameter before advancement) were also examined. RESULTS: STM significantly increased the cross-sectional area and the anteroposterior diameter of the IJV in both positions. The time required to insert the catheter was significantly shorter in the STM group, probably mainly due to a shorter guidewire insertion time. The degree of IJV collapse during advancement of the needle was much lower in the STM group. CONCLUSIONS: STM facilitates IJV catheterization in infants and neonates weighing <5 kg by enlarging the IJV and preventing vein collapse.

Skin-traction method prevents the collapse of the internal jugular vein caused by an ultrasound probe in real-time ultrasound-assisted guidance.

PURPOSE: Real-time ultrasound-assisted guidance for catheterization of the internal jugular vein (IJV) is known to be useful, especially for a small-sized vein, which is difficult to catheterize. However, one of the problems with real-time ultrasound-assisted guidance is that the ultrasound probe itself can collapse the vein. We have developed a novel "skintraction method (STM)", in which the puncture point of the skin over the IJV is stretched upwards with several pieces of surgical tape in the cephalad and caudal directions with the aim being to facilitate catheterization of the IJV. We examined whether this method increased the compressive force required to collapse the IJV. METHODS: In ten volunteers, the compressive force required to collapse the right IJV, and the cross-sectional area and anteroposterior and transverse diameters of the IJV were measured with ultrasound imaging in the supine position (SP) with or without the STM or in the Trendelenburg position of 10 degrees head-down (TP) without the STM. RESULTS: The compressive force to required to collapse the vein was increased significantly with the STM, while the crosssectional area and anteroposterior diameter of the vein in the SP with STM were similar to those in the TP without the STM. CONCLUSION: With the STM, not only the cross-sectional area but also the compressive force required to collapse the IJV increased. Thus, the STM may facilitate real-time ultrasoundassisted guidance for catheterization of the IJV by maintaining the cross-sectional area of the vein during the guidance.

A simple, lightweight CPAP-delivery device, composed of a three-way stopcock, for the nondependent lung.

PURPOSE: We aimed to introduce a simple, lightweight continuous positive airway pressure (CPAP)-delivery device for the nondependent lung during one-lung ventilation, to investigate how the type of three-way stopcocks, and the compliance and resistance of a test lung affect the relationship between the oxygen flow rate and CPAP level produced, and to examine how the device works in a clinical setting. METHODS: In the test lung study, the bronchial blocker of a Univent tube was connected to a test lung. The effects of oxygen-flow rate, types of three-way stopcocks, and compliance and resistance of the test lung on the CPAP levels were studied. In the clinical study, the lightweight device was used to treat hypoxia in seven patients during one-lung ventilation with the bronchial blocker. RESULTS: In the test lung study, the CPAP level produced by the device was proportional to the oxygen-flow rate, dependent on the type of three-way stopcock used, and independent of the compliance or resistance of the test lung. There was no discrepancy between the plateau pressures of the test lung and the monitoring port of an additional stopcock at any degree of compliance or resistance of the test lung at any oxygen-flow rate. Therefore, the relationship between the oxygen-flow rate and CPAP level can be ensured in advance before application to the lung, with an additional three-way stopcock of which the distal end is occluded. In the clinical study, peripheral oxygen sataration Sp(O2) improved while the CPAP level ranged from 2.8 to 5.4 cmH2O. CONCLUSION: The lightweight CPAP delivery-device can provide variable CPAP levels by adjusting the oxygen-flow rate without real-time monitoring of the pressure.

The skin-traction method increases the cross-sectional area of the internal jugular vein by increasing its anteroposterior diameter.

PURPOSE: We developed a novel "skin-traction method" in which the puncture point of the skin over the internal jugular vein (IJV) is stretched upward with several pieces of surgical tape in the cephalad and caudad directions to facilitate cannulation of the IJV. We investigated whether this method increases the cross-sectional area of the IJV. METHODS: In 11 healthy volunteers, the cross-sectional area, anteroposterior diameter, and transverse diameter of the right IJV (RIJV) were recorded by ultrasound echo at head tilts of +10 degrees , +5 degrees , 0 degrees , -5 degrees , and -10 degrees with and without the skin-traction method. RESULTS: The skin-traction method significantly increased the cross-sectional areas of the RIJV at head tilts of +10 degrees , +5 degrees , and 0 degrees . In the flat position, the skin-traction method increased the cross-sectional area of the RIJV from 1.21 +/- 0.44 cm(2) to 1.75 +/- 0.60 cm(2) (44.6% increase), which is almost the same as that in the Trendelenburg position without this method (1.60 +/- 0.54 cm(2) at -5 degrees and 1.83 +/- 0.56 cm(2) at -10 degrees ). The anteroposterior diameter of the RIJV was significantly increased in all positions with this method, although the transverse diameter was not. CONCLUSION: This method significantly increased the cross-sectional area of the RIJV by increasing the anteroposterior diameter of the RIJV. Even in the flat position, this method was almost as efficacious as the Trendelenburg position. This method thus appears to facilitate IJV cannulation.

Modified oxygen mask to induce target levels of hyperoxia and hypercarbia during radiotherapy: a more effective alternative to carbogen.

PURPOSE: Carbogen has long been under investigation as an adjuvant to radiotherapy of tumors. A major factor confounding its evaluation is its inconsistency in raising blood partial pressure of CO(2) (pCO(2)). We investigated whether a new partial rebreathing method would provide better control of pCO(2) than carbogen. METHODS AND MATERIALS: We compared the efficacy of each method in 10 healthy volunteers. Volunteers breathed 1.5, 3 and 5% carbogen in 5-min stages via the usual non-rebreathing circuit. All the volunteers then breathed 100% O(2) through a commercial sequential gas delivery (SGD) circuit modified by attaching a reservoir to its exhalation port. Hypercarbia was induced by step reductions in oxygen flow to the SGD circuit. We monitored minute ventilation and end-tidal pCO(2) (ETpCO(2)) as a surrogate for its arterial value. RESULTS: Inhalation of 1.5 and 3% carbogen did not increase ETpCO(2) from baseline (40 +/- 1.5 mmHg); 5% carbogen increased ETpCO(2) to 45 +/- 1.6 mmHg (p < 0.001). With the SGD circuit, reducing O(2) flow to 4.3 +/- 0.7 l/min increased ETpCO(2) in all subjects from 41 +/- 2.0 mmHg (baseline) to 46 +/- 2.1 mmHg (p < 0.001). Voluntary hyperventilation reduced ETpCO(2) with 5% carbogen but not with SGD (p = 0.379). CONCLUSIONS: We confirm previous observations that carbogen inhalation does not result in a predictable rise in ETpCO(2) and suggest that a precise and stable target ETpCO(2) can instead be induced by simply controlling O(2) flow into a modified SGD circuit. We hoped that the reliable control of pCO(2) will enable studies that address first, the efficacy of raising ETpCO(2) on specific tumor blood flow, and eventually, its benefit as an adjuvant to radiotherapy.

Cardiac output increases the rate of carbon monoxide elimination in hyperpneic but not normally ventilated dogs.

PURPOSE: The very high solubility of carbon monoxide (CO) in blood suggests that its elimination depends predominantly on ventilation and not perfusion. Nevertheless, hyperventilation is not used for CO elimination because of the adverse effects of hypocapnia. With isocapnic hyperpnea (IH), ventilation can be increased considerably without hypocapnia. This raises the issue of whether CO elimination is limited by perfusion during IH. We studied the effect of increasing cardiac output on t1/2, the half-time of decline of blood carboxyhemoglobin concentration ([COHb]), during normal ventilation (NV) and during IH. METHODS: After ethics approval was received, 13 pentobarbital-anesthetized ventilated dogs were exposed to CO to increase their [COHb]. They were then ventilated with NV or IH. At each level of ventilation, dogs were randomly assigned to treatment with dobutamine (to increase cardiac output) or to no dobutamine treatment. After the return of [COHb] to control levels, each dog was re-exposed to CO and treated with the same ventilatory mode, but the alternative inotropic treatment. RESULTS: Gas exchange, [COHb], and hemodynamic measures were recorded during the study. Cardiac index values in the IH group were 4.1 +/- 0.5 and 8.2 +/- 1.2 l.min(-1).m(-2) without and with dobutamine infusion, respectively. Dobutamine infusion was associated with a reduction in t1/2 from 20.3 +/- 3.6 to 16.9 +/- 2.4 min (P = 0.005) in the IH group, but no change in the NV group. CONCLUSION: These findings suggest that CO elimination during IH treatment is limited at least partly by pulmonary blood flow and may therefore be further augmented by increasing cardiac output.

Modified N95 mask delivers high inspired oxygen concentrations while effectively filtering aerosolized microparticles.

STUDY OBJECTIVE: In a pandemic, hypoxic patients will require an effective oxygen (O2) delivery mask that protects them from inhaling aerosolized particles produced by others, as well as protecting the health care provider from exposure from the patient. We modified an existing N95 mask to optimize O2 supplementation while maintaining respiratory isolation. METHODS: An N95 mask was modified to deliver O2 by inserting a plastic manifold consisting of a 1-way inspiratory valve, an O2 inlet and a gas reservoir. In a prospective repeated-measures study, we studied 10 healthy volunteers in each of 3 phases, investigating (1) the fractional inspiratory concentrations of O2 (F(I)O2) delivered by the N95 O2 mask, the Hi-Ox80 O2 mask, and the nonrebreathing mask during resting ventilation and hyperventilation, each at 3 O2 flow rates; (2) the ability of the N95 mask, the N95 O2 mask, and the nonrebreathing mask to filter microparticles from ambient air; and (3) to contain microparticles generated inside the mask. RESULTS: The F(I)O2s (median [range]) delivered by the Hi-Ox80 O2 mask, the N95 O2 mask, and the nonrebreathing mask during resting ventilation, at 8 L/minute O2 flow, were 0.90 (0.79 to 0.96), 0.68 (0.60 to 0.85), and 0.59 (0.52 to 0.68), respectively. During hyperventilation, the FiO2s of all 3 masks were clinically equivalent. The N95 O2 mask, but not the nonrebreathing mask, provided the same efficiency of filtration of internal and external particles as the original N95, regardless of O2 flow into the mask. CONCLUSION: An N95 mask can be modified to administer a clinically equivalent FiO2 to a nonrebreathing mask while maintaining its filtration and isolation capabilities.

Anesthetic and airway management of general anesthesia in a patient with Meckel-Gruber syndrome.

Meckel-Gruber syndrome, characterized by occipital encephalocele, microcephaly, polydactyly, cleft lip or palate, mandibular micrognathism, and anatomical abnormality of the larynx and tongue, along with other associated malformations, is in the list of diseases associated with difficult airway. However, there has been no report on the management of general anesthesia and airway management for such patients. A 2-year-old girl with Meckel-Gruber syndrome was scheduled for cardioplasty and gastrostomy for gastroesophageal reflux under general anesthesia. Preoperative examination revealed obesity, microgenia, dysspondylism, proteinuria, hypoplastic kidneys, and stenosis of the anal canal. Although we anticipated some difficulty with the intubation and prepared several alternative methods for intubation, such as a bronchofiberscope and a laryngeal mask airway, tracheal intubation was completed without difficulty using conventional laryngoscopy after inhalational induction with sevoflurane. Because most patients with this syndrome die before and shortly after delivery, those who survive to some age might have less severe deformities.

The changes in pulmonary capillary blood flow and anatomical dead space during pulmonary resection under one-lung ventilation.

Pulmonary capillary blood flow (PCBF), anatomical dead space (VDaw) and SpO2 were measured and recorded continuously using NICO (Novametrix Medical Systems Inc, USA) in 2 cases during pulmonary resection under one-lung ventilation (OLV). A pulmonary artery catheter was inserted and continuous CO (CCO) was also measured in case 2. In both cases PCBF decreased by half when one lung was blocked. CCO was unchanged before and after one lung blockade in case 2. During OLV, SpO2, which had initially decreased, gradually increased along with a very slow increase in PCBF. The decreased PCBF obtained with NICO represents the pulmonary blood flow of the ventilated (non-blocked) lung. The gradual increase in PCBF with NICO during OLV may express the compensatory effects of hypoxic pulmonary vasoconstriction. By measuring VDaw before, during and after one-lung ventilation, we were able to calculate the bronchial volume of the non-ventilated lung and that of the resected lung.

Dispersal of respiratory droplets with open vs closed oxygen delivery masks: implications for the transmission of severe acute respiratory syndrome.

Nosocomial transmission of droplet-borne respiratory infections such as severe acute respiratory syndrome (SARS) may be influenced by the choice of oxygen face mask. A subject inhaled saline mist and exhaled through three oxygen masks to illustrate the pattern of dispersal of pulmonary gas. In two commonly used masks, exhaled gas formed a plume emanating from the side vents, while a third mask with a valved manifold, which was modified by adding a respiratory filter, retained the droplets. Maintaining respiratory isolation during the administration of oxygen may reduce the risk of the nosocomial transmission of respiratory infections such as SARS.

Calculation of O2 consumption during low-flow anesthesia from tidal gas concentrations, flowmeter, and minute ventilation.

We present the principles of a new method to calculate O2 consumption (V*O2) during low-flow anesthesia with a circle circuit when the source gas flows, end-tidal O2 concentrations and patient inspired minute ventilation are known. This method was tested in a model with simulated O2 uptake and CO2 production. The difference between calculated V*O2 and simulated V*O2 was 0.01 +/- 0.02 L/min. A similar approach can be used to calculate uptake of inhaled anesthetics. At present, with this method, the limiting factor in precision of measurement of V*O2 and uptake of anesthetic is the precision of measurement of gas flow and gas concentration (especially O2 concentration in end-tidal gas, FETO2) available in clinical anesthetic units.