Comparison of cuffed and uncuffed endotracheal tubes in young children during general anesthesia

BACKGROUND: Uncuffed endotracheal tubes are routinely used in young children. This study tests a formula for selecting appropriately sized cuffed endotracheal tubes and compares the use of cuffed versus uncuffed endotracheal tubes for patients whose lungs are mechanically ventilated during anesthesia. METHODS: Full-term newborns and children (n = 488) through 8 yr of age who required general anesthesia and tracheal intubation were assigned randomly to receive either a cuffed tube sized by a new formula [size(mm internal diameter) = (age/4) + 3], or an uncuffed tube sized by the modified Cole's formula [size(mm internal diameter) = (age/4) + 4]. The number of intubations required to achieve an appropriately sized tube, the need to use more than 21.min-1 fresh gas flow, the concentration of nitrous oxide in the operating room, and the incidence of croup were compared. RESULTS: Cuffed tubes selected by our formula were appropriate for 99% of patients. Uncuffed tubes selected by Cole's formula were appropriate for 77% of patients (P < 0.001). The lungs of patients with cuffed tubes were adequately ventilated with 2 1.min-1 fresh gas flow, whereas 11% of those with uncuffed tubes needed greater fresh gas flow (P < 0.001). Ambient nitrous oxide concentration exceeded 25 parts per million in 37% of cases with uncuffed tubes and in 0% of cases with cuffed tubes (P < 0.001). Three patients in each group were treated for croup symptoms (1.2% cuffed; 1.3% uncuffed). CONCLUSIONS: Our formula for cuffed tube selection is appropriate for young children. Advantages of cuffed endotracheal tubes include avoidance of repeated laryngoscopy, use of low fresh gas flow, and reduction of the concentration of anesthetics detectable in the operating room. We conclude that cuffed endotracheal tubes may be used routinely during controlled ventilation in full-term newborns and children during anesthesia.     

Circadian rhythm in toxic effects of cystemustine in mice: relevance for chronomodulated delivery

We present a 76-year-old male patient with adhesive-type cholesteatoma and with metal foreign bodies which were shown to be located in the bony eustachian tube by computed tomography. He sustained a burn injury of the left tympanic membrane when he was struck by a bomb 52 years ago, during World War II. The cannonball fragments that entered the tympanic cavity were apparently transported to and stuck in the eustachian tube isthmus by mucociliary action after spontaneous closure of the tympanic membrane perforation. Persistent tubal obstruction due to the impacted foreign bodies and surrounding granulation tissue seems to have caused chronic adhesive otitis, leading to cholesteatoma which developed in the attic and mastoid antrum. No foreign bodies became visible after cholesteatoma removal by an intact canal wall technique in conjunction with anterior tympanotomy for wide exposure of the supratubal recess and the tympanic osteum of the eustachian tube. Therefore, anterior tympanotomy was further extended anteriorly to open the enlarged bony eustachian tube, allowing visualization and safe removal of two cannonball-fragments firmly impacted within it. We call this surgical approach to the bony eustachian tube "extended anterior tympanotomy". The transmastoidal accessibility of the bony eustachian tube produced by this technique should be assessed by preoperative computed tomography.     

Historic development and medical use of nasopharyngeal radium irradiation treatments

Nasopharyngeal radium irradiation was a medical treatment that replaced eustachian tube inflation and was itself replaced by tympanotomy tubes. Research and development began in 1924 when Samuel J. Crowe was awarded funds to develop an otologic research laboratory. He observed that recurring adenoids and serous otitis were associated with childhood deafness. In collaboration with Curtis Burnam, he developed a nasopharyngeal radon applicator in the 1930s. This was modified in the 1940s to a nasopharyngeal radium applicator, which had a much longer half-life and did not need treatment lengths recalculated twice each day. Numerous reports on the clinical use of nasopharyngeal radium irradiation in the United States were published. Papers have cautioned against possible dangers of nasopharyngeal radium irradiation, but there have been no substantiated reports. This report ends with three concluding suggestions for research.     

Fetal growth in the baboon during the second half of pregnancy

PURPOSE: The purpose of this study was to determine the prevalence of feeding tube placement errors in children. DESIGN AND METHODS: The hospital records of 201 children having both an enteral tube and at least one radiograph showing tube placement were retrospectively reviewed. Chart review was also used to determine the risk factors associated with these errors. Tube placement error was defined as tube tip or orifices in the esophagus or intestine (if the tube was supposed to be in the stomach) or tip or orifices in the esophagus or stomach (if the tube was supposed to be in the intestine.) RESULTS: On the first day, a radiograph documenting tube placement showed that 32 of the 201 children (15.9%) had tube placement errors. Overall, 53 tube placement errors were evident during the 385 observation days on which radiographs were obtained (13.8%). Of the 201 children, 42 (20.9%) had experienced tube placement errors at some time during the period reviewed. Over all radiograph days, activity level was independently related to radiographic tube placement (p = < 0.02), with more errors among active children. Also, classification regression tree analysis showed that age, level of consciousness (alert or comatose versus semicomatose), abdominal distention, vomiting, and orogastric tubes were associated with more tube placement errors. NURSING IMPLICATIONS: Nurses need to be especially careful in assessing tube placement if the pediatric client has one or more of the identified risk factors. Health care providers need to carefully weigh the benefits and risks of feeding by nasal or oral enteral tubes versus the benefits and risks of feeding by endoscopically or surgically placed enteral tubes.     

Dextromethorphan O-demethylation polymorphism in Jordanians

Routine transpyloric placement of feeding tubes reduces aspiration in intensive care unit patients. Spontaneous passage eliminates the need for radiologic or endoscopic intervention. It is unclear whether the addition of a weight to the end of the tube or the use of the prokinetic agent metoclopramide in the conventional dose (10 mg) improves spontaneous transpyloric placement. In a randomized, prospective trial, 39 intensive care unit patients (age > 2 years) had a total of 50 nasoenteral tubes placed after intravenous metoclopramide (20 mg in adults, 0.2 mg/kg in children). The tubes were 8 French in diameter with either a weighted end or an unweighted bullet tip. Tip position was confirmed radiographically within 4 hours after blinded placement and at 1 and 2 days if spontaneous passage had not occurred. At 4 hours, 36% of the weighted tubes and 84% of the unweighted tubes (p < .002) had passed through the pylorus. At 1 day, 48% of the weighted tubes and 86% of the unweighted tubes (p < .007) had achieved transpyloric position. At 2 days, 56% and 92% of the weighted and unweighted tubes, respectively, had passed through the pylorus (p < .009, chi 2). The occurrence of transpyloric passage and the rapidity at which it occurred was significantly greater for the unweighted tube during all time periods. A poststudy trial was conducted to evaluate the effect of the normal dose of metoclopramide (10 mg in adults and 0.1 mg/kg in children) and the transpyloric passage of the unweighted feeding tube. Twenty-five patients received 10 mg of metoclopramide before the insertion of the unweighted tube.(ABSTRACT TRUNCATED AT 250 WORDS)     

Advantage of rubber over plastic endotracheal tubes for rapid extubation in a laser fire

The occurrence of airway fires during laser airway surgery necessitates the use of special techniques to improve patient safety. For example, it is recommended that the endotracheal tube cuff be inflated with saline. However, in the event of an endotracheal tube fire, the tube must be quickly removed. This study was designed to determine the time necessary for red rubber (RR) or polyvinylchloride (PVC) endotracheal tubes to be removed from a model airway after inflating the cuffs with saline. A model larynx and trachea was suspended vertically. It was intubated with either 7.0 RR or PVC endotracheal tubes. Six milliliters of saline was used to inflate the endotracheal tube cuffs. After inflation, a clamp was used to occlude the pilot tube on the RR endotracheal tubes. A 4-lb weight was then suspended from the endotracheal tube. The time to spontaneous extubation of the model trachea after unclamping the pilot tubes on 12 RR endotracheal tubes was determined. For the PVC endotracheal tubes, the times to spontaneous extubation using the 4-lb weight were determined in 12 endotracheal tubes after cutting the pilot tube and in 12 by maximum aspiration of the saline from the endotracheal tube cuff with a 10-ml syringe. A time of 0.94 +/- 0.10 sec (mean +/- SD) was required for spontaneous extubation of the RR endotracheal tubes after unclamping the pilot tube. For the PVC endotracheal tubes, extubation occurred 3.28 +/- 1.08 and 1.81 +/- 0.60 sec after cutting the pilot tube or deflating the cuff with a syringe, respectively. The mean times for each of the 3 groups were significantly different (p < 0.05) from each other as determined by the ANOVA. This study shows that if PVC endotracheal tubes are used, deflation of the saline-filled cuff by aspiration with a 10-ml syringe is faster than cutting the pilot tube. Unclamping the pilot tube on the RR endotracheal tubes resulted in the fastest time to endotracheal extubation.     

Brainstem auditory evoked potentials in young children before and after tympanostomy tube placement

To evaluate the effect of tympanostomy tube placement upon the hearing function of infants and young children, brainstem auditory evoked potentials (BAEP) were recorded in a group of young children (mean age 22 mos) receiving this treatment for otitis media with effusion (OME). For comparison, a group of healthy infants with normal behavioral audiometry were also tested with BAEP. Hearing loss was estimated for each ear using peak V latency-intensity curves. To evaluate the immediate effect of tube placement, 98 ears in 52 children were tested immediately before and after tube insertion. The 63 ears with effusion had prolonged peak latencies that decreased significantly (P < 0.001) immediately after tube placement and a mean hearing loss estimate of 22 dB that improved significantly (P < 0.0001) to 11 dB immediately after tube insertion. The 35 ears without effusion at myringotomy had a mean hearing loss estimate of 8 dB that did not change significantly after tube insertion. To evaluate the short-term effect of tube presence, 39 ears in 25 children were tested 3 weeks to 18 months after tube insertion. The 28 ears with dry tubes had a mean hearing loss estimate of 3 dB, and the 11 ears with otorrhea had a mean hearing loss estimate of 31 dB. The magnitude of mean hearing loss estimates in these young children with OME and the improvement in hearing function with tube placement is similar to that reported in older children studied with BAEP and audiometry. The study groups with a history of otitis media that had resolved by the time of testing had isolated prolongation of mean III-V interpeak latencies compared to normals (P < 0.01). These studies show that BAEP techniques are useful in estimating hearing loss in children with OME who are difficult to test by behavioral audiometry and show changes in rostral brainstem transmission in very young children with a history of OME.     

Investigation on the Hydroforming Characteristics of Double‐layered Tubes

Double‐layered tubes consist of an inner tube and an outer tube. Both are similar in material, contact closely and deform simultaneously when subjected to external force. Hydroforming assembly technology has several advantages in the manufacturing of double‐layered tubes. In this study, the hydroforming characteristics of double‐layered tube are investigated. Free bulging tests are performed to produce formability diagrams of double‐layered tubes at various forming pressures and feeding amounts. In addition, the hexagonal‐shape hydroforming test is performed to estimate the dimensional accuracy of double‐layered tubes through the corner filling ratio and the gap between the inner and outer tubes. Besides experimental analyses, an analytical model that can predict internal pressure for the hydroforming of double‐layered tubes is proposed and experimentally validated in this study.     

Feeding tubes for tube feeding

Several techniques are available for the provision of enteral nutritional support. Nasal tubes, gastrostomy tubes and jejunostomy tubes can be distinguised. Nasal tubes are used for short-term support, gastrostomy tubes (preferably via a percutaneous endoscopic gastrostomy) for long-term support (over 4 to 6 weeks), while (needle catheter) jejunostomy tubes are most often used to provide early enteral nutrition immediately after operations on the proximal gastrointestinal tract. The most frequent complications are: with the nasal tube dislodging, clogging and aspiration, with the gastrostomy tube peristomal infection and with the jejunostomy tube, obstruction. It should further be noted that the quantity of enteral nutrition prescribed and that actually administered may differ substantially so that patients with a feeding device may even become malnourished. With proper patient selection and secure control of the energy balance, feeding tubes are simple (temporary) devices that improve the patient's health and quality of life.     

Women are at greater risk than men for malpositioning of the endotracheal tube after emergent intubation

OBJECTIVES: To investigate the occurrence of endotracheal tube malpositioning after emergent intubation in critically ill adults and to determine the need for a routine postintubation chest radiography to assess endotracheal tube position. DESIGN: Prospective study. SETTING: All adult critical care and acute care units of a 560-bed university teaching hospital. PATIENTS: Study of 297 consecutive intubations (185 intubations in males and 112 intubations in females) in 238 adult patients. METHODS: Emergent endotracheal intubations were performed by resident physicians with supervision from an intensive care unit (ICU) or anesthesia attending physician or an anesthesia resident. After intubation, proper positioning of the endotracheal tube was verified by the intubating physician using clinical criteria, including auscultation of bilateral breath sounds, symmetric chest expansion, and palpation of the endotracheal tube cuff in the suprasternal notch. The endotracheal tube position relative to the lower anterior incisors or alveolar ridge was recorded using the centimeter markings printed on the endotracheal tube. A chest radiograph was obtained after intubation to verify endotracheal tube position. Appropriate endotracheal tube position on chest radiograph was defined as between > 2 and < or = 6 cm above the carina. MEASUREMENTS AND MAIN RESULTS: Of the 297 intubations, 26 were excluded from analysis because a chest radiograph was not obtained or the patient was not of normal stature. For the remaining 271 intubations, 42 (15.5%) endotracheal tubes were inappropriately placed, according to the radiographic assessment. The percentage of malpositioned endotracheal tubes was significantly higher in women than in men (61.9% vs. 38.1%, respectively; chi-square: p < .001). Thirty-three (78.6%) of 42 malpositioned endotracheal tubes were placed < 2 cm from the carina, with the highest occurrence (24/33) of proximal malposition occurring in women. Positioning of endotracheal tubes using the centimeter markings printed on the tube referenced to the lower incisors did not accurately identify malposition as documented by chest radiograph. CONCLUSIONS: Emergent endotracheal intubations result in a significant occurrence of malpositioned endotracheal tubes that are undetected by clinical evaluation. Malpositioning is not detected by routine clinical assessment, but only by chest radiograph. Women are at greater risk than men for endotracheal tube malpositioning after emergent intubation; in women, the endotracheal tube is more likely to be positioned too close to the carina. A chest radiograph for confirmation of endotracheal tube position after emergent intubation should remain the standard of practice.     

Airway resistance and work of breathing in tracheostomy tubes

Recommendations for sizing of tracheostomy tubes are generally based on anatomic considerations with the largest fitting tube most commonly placed. Once in the tracheostomy site, the tube assumes the new role of the upper airway. Consideration of the airway resistance of each tracheostomy tube and change in work of breathing are important in maintaining the respiratory system homeostasis. The airflow dynamics of neonatal, pediatric, and adult tracheostomy tubes were studied. Flow rates were plotted against change in pressure for inspiratory and expiratory flows and resistances for each tube were calculated. The expiratory resistances were larger for the neonatal tubes and pediatric tubes 0 and 00, while inspiratory resistances were the limiting factor in the adult tubes and the larger pediatric tubes. Comparison of calculated resistances of the tracheostomy tubes was made with known physiologic airway resistances. Adult tubes 8 and 10 most closely simulated the upper airway resistance of adults and neonatal tube 0 appeared most appropriate for the newborn. Work of breathing was determined for each tracheostomy tube. Increasing tube diameter as well as decreasing tidal volume and respiratory rate decreased the amount of work required to maintain a given flow.     

Experiences with polyethylene ventilation tubes in children with recurrent middle ear inflammation (author's transl)

Middle-ear ventilation tubes (of the Sheehy modification) were placed in 401 ears of 209 children under 16 years of age as treatment for recurrent middle-ear infection. The same procedure was later required in 26% of the cases studied because of further recurrence of middle-ear infection. In four per cent of all patients studied, the ventilating tube failed to cure middle ear disease in spite of controlled concomitant antibacterial therapy. In these cases, an early extrusion of the tube was commonly found. Among all patients, the tube was spontaneously extruded in 76 per cent of the ears, whereas the intubation time was longer than half a year in 53 per cent of the cases. No complications from insertion of the ventilation tubes was seen in the present series of patients. The tympanic membrane was found to be normal in 71 per cent of all cases when follow-up examination was obtained three months after completion in intubation. However, a permanent tympanic membrane perforation was found in five ears (1% of patients). The present study has confirmed the usefulness of middle-ear ventilation tubes, particularly in patients with recurrent middle-ear infections.     

Relationships between otitis media sequelae and age

OBJECTIVES: To explore relationships between age and sequelae in two groups of children treated with tympanostomy tubes for chronic otitis media with effusion (OME). STUDY DESIGN: Cross-sectional study of sequelae among children, adolescents, and adults at 4 years and 9 to 23 years after tympanostomy tube treatment. METHODS: Group I was examined with otomicroscopy, tympanometry, and audiometry two to four times a year as part of a prospective study, and they were evaluated 4 years after initial tube treatment for this study. Group II received tubes while participating in a chronic OME study, but participants were not followed prospectively after treatment. Nine to 23 years after tube treatment, they were examined with otomicroscopy, tympanometry, and hearing screening. RESULTS: Among the 5- to 28- year-old subjects, cholesteatoma (< or = 1%) and perforation (< or = 2%) were rare. In Group I, tympanosclerosis increased with age (P < .01), and OME (flat tympanograms) decreased with age in Group II (P < .01). The older cohort was more likely to have severe retractions (18% vs. 4%, P = .02), hearing loss (21% vs. 10%, P < .01), and severe atrophy (24% vs. 0%, P < .01) than the younger cohort, but they were less likely to have flat tympanograms (2% vs. 12%, P < .01). CONCLUSIONS: Although OME became less prevalent with age, important sequelae (severe atrophy, severe tympanic membrane retraction, hearing loss, cholesteatoma, and chronic perforation) may develop in children with chronic OME as they become adolescents and young adults. Long-term prospective studies are important in defining the progression of sequelae in these children.     

Examining the safety of nasogastric tube placement after endoscopic sinus surgery

Several cases of intracranial injury during the placement of nasogastric tubes have been reported, usually in the setting of anterior skull base fractures. The fovea ethmoidalis and sphenoid sinus are often exposed after endoscopic sinus surgery, so that these structures are potentially placed in the line of contact during nasogastric tube placement. In order to evaluate the ability of the fovea ethmoidalis and roof of the sphenoid sinus to withstand penetration from possible contact during nasogastric tube placement, 12 fresh cadaver heads were studied. After complete endoscopic ethmoidectomy and wide sphenoidotomy, standard 18F and 16F nasogastric tubes were inserted to produce deliberate direct contact with both the fovea ethmoidalis and the sphenoid sinus roof. No penetrations of the fovea occurred in 20 specimen sides with the 18F tube; penetration did occur with the 16F tube in 1 of 13 sides (7.7%). With respect to the sphenoid sinus, no intracranial penetrations occurred in 16 and 11 sides for the 18F and 16F tubes, respectively. The sphenoid sinus was easily entered even in the presence of an intact middle turbinate. These data suggest that although intracranial penetration during nasogastric intubation after endoscopic sinus surgery is an unlikely event, there is a non-negligible risk of such injury. Nasogastric intubation should be performed with caution in patients with a history of sinus surgery.     

Nonradiographic assessment of enteral feeding tube position

OBJECTIVE: To determine whether a clinical, nonradiographic criterion can be used to predict when the tip of a blindly placed feeding tube is in the small intestine. DESIGN: Prospective sample. SETTING: Pediatric intensive care unit at a tertiary care children's hospital. PATIENTS: Critically ill children requiring transpyloric feeding. INTERVENTIONS: The small bowel was intubated, using a blind, bedside transpyloric feeding tube placement protocol. The feeding tube was considered to be in the small bowel when <2 mL of a 10- mL aliquot of insufflated air could be aspirated from the feeding tube. This clinical criterion was confirmed with an abdominal radiograph. MEASUREMENTS AND MAIN RESULTS: Patient age ranged from 1 month to 19 yrs (median 6 months). Weight ranged from 2.2 to 60 kg (median 4.9). Median time to feeding tube placement was 10 mins (range 5 to 60). Eighty-nine percent of the patients were mechanically ventilated, while 28% of these patients were pharmacologically paralyzed. Seventy-five feeding tubes were inserted. There were no known complications. Ninety-nine (74/75) percent of the feeding tubes were positioned in the small bowel. The inability to aspirate insufflated air correctly predicted small bowel intubation with 99% certainty (Sequential Probability Ratio Test, p = .05 and power = .80). This test incorrectly predicted the position of only one feeding tube, the 26th, which was in the stomach. Of the 74 feeding tubes positioned in the small bowel, 13 feeding tubes were in the duodenum and 61 were in the jejunum. CONCLUSIONS: The inability to aspirate insufflated air confirms the transpyloric position of a feeding tube. Other clinical criteria did not successfully predict small bowel intubation. Use of this single test may obviate confirmatory abdominal radiographs in carefully selected patients and may lead to more cost-effective and timely initiation of enteral feedings.     

Diimidazo[1,2-c:4'',5''-e]pyrimidines: adenosine agonist activity demonstrated by microphysiometry

Vertigo and dizziness are not common in childhood, but are probably present more often than was formerly thought. These symptoms caused mainly by o700is media and middle ear effusion, two of the most common diseases in children, have been neglected for a long time, both in the literature and in practice, until recently. The purpose of this study was to determine objectively the incidence of balance-related symptoms in children with long-lasting middle ear effusion and to discover whether these symptoms resolve after the insertion of ventilation tubes. One hundred thirty-six children, ages 4 to 9 years, were given electronystagmographic tests and the Bruininks-Oseretsky tests for motor proficiency before and after tube ventilation of the middle ear. The results were compared with those in 74 healthy children with no history of middle ear diseases. Pathologic findings were found in 58% of the children with chronic middle ear effusion, as compared with only 4% of the control group. The symptoms and signs of balance disturbances resolved in 96% of the children after ventilation tube insertion. The results of this study indicate that balance-related symptoms often encountered in young children may result from chronic middle ear effusion and that these symptoms will resolve after evacuation of the effusion and ventilation of the middle ear.     

Computation of diametral deformation of irradiated Zr-2.5 Nb pressure tubes from RAPS-2

The pressure tubes in Pressurised Heavy Water Reactors (PHWRs) are subjected to high stresses, temperatures and fast neutron fluxes which cause changes in dimensions and material properties. To ensure the safe, reliable and economic performance of the reactor, it is important that these changes are known and that the rate of change can be predicted and demonstrated to remain within the design basis. The diametral expansion of pressure tubes due to irradiation creep and growth is an important property that may limit the useful life of the tube. A semiempirical predictive model has been developed to calculate the irradiation creep (diametral) and irradiation growth (diametral) contributions and total diametral change in irradiated pressure tubes. The model can account for variations arising from tube orientation. The sixteen numbers of Zr-2.5Nb pressure tubes (PTs) of RAPS-2 selected had undergone 7.15 Effective Full Power Years (EFPY) of reactor operation. The diametral changes at discrete locations along the length of the pressure tubes are estimated by using the model developed. The maximum of (along the tube length) measured internal diameter data of those fifteen pressure tubes have been compared with those obtained from the model.     

粉末冶金旋压无缝钨管的组织性能及使用情况

用粉末冶金法制坯,以旋压法加工无缝钨管为试样,测定了加工过程中硬度、密度和组织变化,测定了钨管的再结晶温度,并描述了钨管的实际使用情况。不同变形率下钨管的组织是:11%变形率时还有未变形的组织;66%变形率时能看到细长的烧结孔洞;77%变形率时晶粒已破碎,烧结孔洞全部消失。用于钨铼热电偶标定炉的高精度无缝薄壁钨管结果是:φ40×0.25×540mm者,在中心位置100mm范围内,1200℃、1400℃和1600℃的轴向温差分别为±1℃、±6℃和±7℃;φ30×0.25×286mm者,等温区允许误差在1377±12℃,该区长度为120mm。     

Genetic hearing loss with preauricular sinus and branchiogenic fistula

A mother and her two children had hearing loss associated with bilateral preauricular sinus and branchiogenic fistula. All six cochleas studied showed two turns rather than 2 1/2 turns. Complete studies including audiometry, tympanotomy findings, and temporal bone polytomography of these anomalies are reported. Similar cases reported in the English literature are reviewed. It seems that all previous cases may have had an abnormal cochlea as was seen in these cases.     

Flexural Behavior of Hybrid FRP-Concrete-Steel Double-Skin Tubular Members

This paper presents the results of an experimental study on the flexural behavior of a new type of hybrid FRP-concrete-steel member as well as results from a corresponding theoretical model based on the plane section assumption and the fiber element approach. This new type of hybrid member is in the form of a double-skin tube, composed of a steel inner tube and an FRP outer tube with a concrete infill between the two tubes, and may be employed as columns or beams. The parameters examined in this study include the section configuration, the concrete strength, and the thicknesses of the steel tube and the FRP tube, respectively. The results presented in this paper show that these hybrid beams have a very ductile response because the compressive concrete is confined by the FRP tube and the steel tube provides ductile longitudinal reinforcement. The beams' flexural response, including the flexural stiffness, ultimate load, and cracking, can be substantially improved by shifting the inner steel tube toward the tension zone or by providing FRP bars as additional longitudinal reinforcement. The predictions from the theoretical model are in reasonably close agreement with the test results. Differences between the test and predicted results arise from factors not considered in the theoretical model, including the existence of a strain gradient in the confined concrete, concentrations of cracks and the slips between the concrete and the two tubes; these are issues to be accounted for in the development of a more accurate model in the future.