Simulation of the Velocity and Temperature Distribution of Inhalation Thermal Injury in a Human Upper Airway Model by Application of Computational Fluid Dynamics.

Inhalation injury is an important cause of death after thermal burns. This study was designed to simulate the velocity and temperature distribution of inhalation thermal injury in the upper airway in humans using computational fluid dynamics. Cervical computed tomography images of three Chinese adults were imported to Mimics software to produce three-dimensional models. After grids were established and boundary conditions were defined, the simulation time was set at 1 minute and the gas temperature was set to 80 to 320°C using ANSYS software (ANSYS, Canonsburg, PA) to simulate the velocity and temperature distribution of inhalation thermal injury. Cross-sections were cut at 2-mm intervals, and maximum airway temperature and velocity were recorded for each cross-section. The maximum velocity peaked in the lower part of the nasal cavity and then decreased with air flow. The velocities in the epiglottis and glottis were higher than those in the surrounding areas. Further, the maximum airway temperature decreased from the nasal cavity to the trachea. Computational fluid dynamics technology can be used to simulate the velocity and temperature distribution of inhaled heated air.

Firework injuries at a major trauma and burn center: A five-year prospective study.

BACKGROUND AND OBJECTIVE: In China, fireworks are an integral part of the celebration of the annual Spring Festival, but the number of injuries associated with their private use seen in emergency rooms increases dramatically. To raise awareness and help guide future prevention practices in this city, we investigated the epidemiology of firework-related injuries presented at our trauma and burn center in Beijing during the Spring Festivals of 2007-2011. METHODS: Patients were interviewed using a pre-coded questionnaire to elicit information regarding age, gender, causes, injured body part, type of injury, diagnosis, and disposition. RESULT: From 2007 to 2011, during the Spring Festivals 734 patients with fire-work related injuries were seen at our trauma and burn center in Beijing, the median patients of the five year were 140(136-150). The mean age of the patients was 26±15.3 years (range, 1-95 years). Of the 734 patients, the highest proportion of injuries were the 5-14 year-old age group The majority of the patients were male (87.9%), the overall male:female ratio was 7.41:1, and males were predominant in all age groups. For all 5 years, the incidence of firework-related injuries during the Spring Festival Holidays peaked specifically on the first, fifth, and last days, respectively. Injuries were mainly due to improper handling (415/610, 68.0%) or setting off illegal fireworks (195/610, 32.0%). The most frequently injured body parts were the hands and fingers (32.0%), head or face except eyes (28.3%), and trunk (22.4%). Burns were the most common type of injury (65.7%), most of the burned patients (437/453) were between 1% and 10%, and the most common region burned were hands and fingers (218/754). Contusions or lacerations were the second common type of injury (34.3%). Most of the patients (642, 87.5%) were treated and released, while 37 (5%) were treated and transferred, and 55 (7.5%) were admitted for advanced treatment. CONCLUSION: The private use of fireworks during the Spring Festival Holidays is associated with a considerable number of injuries to various parts of the body. We can minimize the number and severity of accidents by raising awareness of safety practices, encouraging professional displays only and motivating manufacturers to adhere to strict quality control.

Circulational heat dissipation of upper airway: Canine model of inhalational thermal injury.

BACKGROUND: The upper airway has powerful heat-absorbing ability, in which the blood circulation may play an important role. OBJECTIVE: This study aimed to explore the circulational heat-dissipating ability, and to investigate the contribution of blood circulation to the heat-absorbing ability of upper airway. METHODS: 18 adult, male Beagle dogs were divided into three groups to inhale thermal dry air of 70-80°C, 150-160°C or 310-320°C for 20min. Blood temperatures and blood flow rates of bilateral common jugular veins (CJVs) were measured. Dogs' breathing rates and air temperatures in middle trachea were also measured. According to the formula "Q=c·m·ΔT", the heat dissipated by blood (Q-blood) and the heat release by air (Q-air) were calculated out. The contribution of circulational heat dissipation to the heat-absorbing ability of upper airway was defined as "C-blood". RESULTS: The blood temperature rise of CJV was 2.24±0.60°C. The blood flow rate of CJV was 44.5±5.9ml/min. The air temperature in middle trachea was 63.5±18.9°C. The mean breathing rate was 51.8±7.5/min. The calculated "Q-blood" and "Q-air" were 13197.3±4408.6J and 33540.2±24578.7J, and the "C-blood" was 55.2±25.0% (21.7-88.8%). CONCLUSION: Circulational heat dissipation plays an important role in the heat-absorbing process of upper airway when inhaled air is less than 160°C. However, for air higher than 160°C, some other mechanism might be dominant in the upper airway's heat-absorbing ability.

Repairing proximal and middle lower-leg wounds with retrograde sartorius myocutaneous flap pedicled by perforating branches of medial inferior genicular artery or posterior tibial artery.

BACKGROUND AND OBJECTIVES: The blood supply of the lower one-third of the sartorius muscle is mainly provided by the descending genicular artery (saphenous artery). The terminal branches of the saphenous artery, together with the perforators of the posterior tibial artery and medial inferior genicular artery, form a stable and rich anastomotic network in the genus inferior medialis. Based on this anatomy, we designed a retrograde sartorius myocutaneous flap to repair wounds in the proximal and middle thirds of the lower leg. METHODS: A sartorius myocutaneous flap with the posterior tibial (or medial inferior genicular) artery perforators as the pedicle was designed. The flap was based on a retrograde flow route: medial inferior genicular and posterior tibial artery perforators, the vascular network at the inferomedial knee, the saphenous artery, saphenous artery perforators, to the sartorius muscle. With this design, the flap can be transferred to the middle and proximal tibia. Between January 2007 and June 2010, 12 patients with middle/proximal lower-leg wounds were successfully treated with this method. RESULTS: Ten of 12 myocutaneous flaps survived with primary healing of wounds. Two cases developed a small degree of distal superficial skin necrosis but with normal muscular blood supply and healed after conservative treatment. CONCLUSION: Retrograde sartorius myocutaneous pedicle flaps from the perforating branches of the medial inferior genicular artery or posterior tibial artery have advantages in terms of reliable blood supply, ease of operation and minimal amount of damage, and can be used to repair proximal and middle lower-leg wounds. They are especially applicable when lower-leg flaps are unavailable due to poor soft-tissue conditions following trauma or multiple operations. However, the safety flap size needs to be determined in future studies.

[Repair of circumferential wound in the wrist region due to high-voltage electrical burn using combined abdominal axial pattern flaps].

OBJECTIVE: To explore the method for repairing circumferential wound in the wrist region due to high-voltage electrical burn. METHODS: Six patients with circumferential wound in the wrist region after high-voltage electrical burn were admitted to our hospital from January 2009 to December 2011. After debridement, wounds in the wrist were repaired with combined abdominal axial pattern flaps. The wound of wrist on the flexor aspect was repaired with paraumbilical flap carrying a portion of rectus abdominis that filled the wound cavity of the wrist on the flexor aspect. The wound of wrist on the dorsal aspect was repaired with lower abdominal flap. Pedicle division was performed 4 - 5 weeks post surgery. Some donor sites were sutured directly, and the others were closed by skin grafting after the suture of anterior sheath. RESULTS: Three flaps survived. Liquefaction necrosis of tissue was observed under two flaps, and they were healed after debridement. Radial artery embolism of wrist occurred in one flap when pedicle division was performed 5 weeks post surgery, and it was healed by a transplantation of a segment of the great saphenous vein to reconstruct radial artery right after debridement. Patients were followed up for 6 - 12 months, and satisfactory appearance and function of the flaps were observed. CONCLUSIONS: It is a feasible option to repair circumferential wound in the wrist region due to high-voltage electrical burn by using paraumbilical flap carrying a portion of rectus abdominis muscle combined with lower abdominal flap.

Temperature distribution in the upper airway after inhalation injury.

OBJECTIVE: The aim of the study was to establish an animal model of laryngeal burn and to investigate the temperature distribution of heated air in the upper airway. METHODS: The animal model was established by inhalation of dry heated air at 80, 160 and 320 °C in 18 healthy, male, adult hybrid dogs. Time for inducing injury was set at 20 min. The distribution of temperatures after heated-air inhalation was examined at different locations including the epiglottis, laryngeal vestibule, vocal folds and trachea. RESULTS: The temperatures of the heated air decreased to 47.1, 118.4 and 193.8 °C at the laryngeal vestibule and to 39.3, 56.6 and 137.9 °C at the lower margin of vocal folds in the 80, 160 and 320 °C groups, respectively. CONCLUSION: Due to its special anatomy and functions, the larynx has different responses to dry heated air at different temperatures. The air temperature decreases markedly when the air arrives at the larynx. By contrast, the larynx has a low capacity for blocking high-temperature air and retaining heat. As a result, high-temperature air often causes more severe injury to the larynx and the lower airway.

Large-area burns with pandrug-resistant Pseudomonas aeruginosa infection and respiratory failure.

BACKGROUND: Infection due to pandrug-resistant Pseudomonas aeruginosa (PDRPA) has become a challenge in clinical practice. The aim of this research was to summarize the treatment of large-area burns (60% - 80%) with PDRPA infection and respiratory failure in our hospital over the last two years, and to explore a feasible treatment protocol for such patients. METHODS: We retrospectively analyzed the treatment of five patients with large-area burns accompanied by PDRPA infection and respiratory failure transferred to our hospital from burn units in hospitals in other Chinese cities from January 2008 to February 2010. Before PDRPA infection occurred, all five patients had open wounds with large areas of granulation because of the failure of surgery and dissolving of scar tissue; they had also undergone long-term administration of carbapenems. This therapy included ventilatory support, rigorous repair of wounds, and combined antibiotic therapy targeted at drug-resistance mechanisms, including carbapenems, ciprofloxacin, macrolide antibiotics and ß-lactamase inhibitors. RESULTS: Four patients recovered from burns and one died after therapy. CONCLUSIONS: First, compromised immunity caused by delayed healing of burn wounds in patients with large-area burns and long-term administration of carbapenems may be the important factors in the initiation and progression of PDRPA infection. Second, if targeted at drug-resistance mechanisms, combined antibiotic therapy using carbapenems, ciprofloxacin, macrolide antibiotics and ß-lactamase inhibitors could effectively control PDRPA infection. Third, although patients with large-area burns suffered respiratory failure and had high risks from anesthesia and surgery, only aggressive skin grafting with ventilatory support could control the infection and save lives. Patients may not be able to tolerate a long surgical procedure, so the duration of surgery should be minimized, and the frequency of surgery increased.

Evaluation of the cytotoxicity of cell free dermal substitutes using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide method.

BACKGROUND: The cytotoxicity of dermal substitutes may be increased by the very processes used to deplete the cells. The present research aimed to investigate the method for monitoring the cytotoxicity of cell-free dermal substitutes using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method. METHODS: The cytotoxicity of four dermal substitutes was evaluated using the MTT method according to the standards set by the Chinese State Food and Drug Administration (SFDA). Swine acellular dermal matrix (SADM) and goat acellular dermal matrix (GADM) were produced using a repeated freeze-thaw method. Human dermal matrix glutaraldehyde composite (HADM-G) and SADM cross-linked with glutaraldehyde (SADM-G) were produced using conventional methods. RESULTS: The cytotoxicity of all dermal substitutes ranged from Grade 0 to Grade 1, meeting the standards of the Chinese FDA. The OD(490) of both SADM and GADM was higher than that of either HADM-G or SADM-G (P < 0.05). CONCLUSION: Dermal substitutes produced by the freeze-thaw method are less cytotoxic than those produced using conventional methods.

[Quantification of type I and III collagen content in normal human skin in different age groups].

OBJECTIVE: To quantify the content of type I, III collagen and their ratio in normal human skin of different age, and to explore the regulation of changes. METHODS: The normal human skin specimens were obtained from 6 spontaneously aborted fetus and 56 burn patients of different ages, including infants (newborn -3 years), pre-school group ( > 3, < or =7 years), adolescent group ( >7, < or = 18 years), youth and middle age group ( > 18, < or = 50 years), and elderly group ( > 50 years), were studied. The total collagen content were determined by hydroxyproline method. The contents of type I, Ill collagen and their ratio were examined by immunohistochemistry. RESULTS: The total collagen content decreased along with increase in age, and it was highest in fetus [(543 +/- 13) microg/g]. The ratio between type I and Ill collagen increased along with increase in age. The content of type III collagen was highest in fetus [(278 +/- 7) microg/g], and it decreased along with increase in age. The content of type I collagen content was [(265 +/- 7) microg/g] in fetus, and it was increased slightly in infant and pre-school groups, then decreased along with advance in age. CONCLUSION: Decomposition of type III collagen in normal human skin may exceed its synthesis after birth immediately, leading to its reduction. Synthesis of type I collagen in normal human skin is dominant before 8 years old, and it shows an opposite tendency afterwards.