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PubMed2005

EEG patterns associated with nitrogen narcosis (breathing air at 9 ATA).

INTRODUCTION: The narcotic effect of nitrogen impairs diver performance and limits dive profiles, especially for deep dives using compressed air. It would be helpful to establish measurable correlates of nitrogen narcosis. METHODS: The authors observed the electroencephalogram (EEG) of 10 subjects, ages 22-27 yr, who breathed air during a 3-min compression to a simulated depth of 80 msw (9 ATA). The EEG from a 19-electrode cap was recorded for 20 min while the subject reclined on a cot with eyes closed, first at 1 ATA before the dive and again at 9 ATA. Signals were analyzed using Fast Fourier Transform and brain mapping for frequency domains 0-4 Hz, 4-7 Hz, 7-12 Hz, and 12-15 Hz. Student's paired t-test and correlation tests were used to compare results for the two conditions. RESULTS: Two EEG patterns were observed. The first was an increase in delta and theta activity in all cortical regions that appeared in the first 2 min at depth and was related to exposure time. The second was an increase in delta and theta activity and shifting of alpha activity to the frontal regions at minute 6 of breathing air at 9 ATA and was related to the narcotic effects of nitrogen. DISCUSSION: If confirmed by studies with larger case series, this EEG pattern could be used to identify nitrogen narcosis for various gas mixtures and prevent the dangerous impact of nitrogen on diver performance.

Adult↗
PubMed1993

Subcutaneous emphysema and pneumomediastinum following dental extraction.

A case of acute subcutaneous emphysema of the lateral region of the neck is described. The patient, a 26-year-old woman, also had radiologic evidence of pneumomediastinum. She completely recovered in a few days under prophylactic antibiotherapy. In this case, subcutaneous and mediastinal emphysema was most probably due to the introduction of air into the soft tissue during dental surgery using compressed air equipment.

Adult↗
PubMed1999

In vivo effect of a self-etching primer on dentin.

PURPOSE: To determine the ultrastructural aspects of the dentin collagen area in the cavity preparation floor produced in vivo after phosphoric acid acid-etching or after using Clearfil Liner Bond 2 self-etching primer (LB2 Primer). MATERIALS AND METHODS: Twenty-four non-carious third molars scheduled for extraction from young adult patients (16-30 years old) were used. Conventional Class I cavities (+/- 2 mm deep) were prepared on the occlusal surfaces of all teeth using a cylindrical diamond bur on a high-speed handpiece with copious water spray. To avoid dehydration of the dentin, the smear layer-covered dentin was briefly air-dried for 2 seconds. Cavities were assigned at random to the following groups: Group A: Dentin etched for 15 seconds with 34% phosphoric acid, rinsed for 20 seconds and then briefly air-dried for 2 seconds with oil-free compressed air leaving the surfaces slightly moist. Group B: LB2 Primer was applied to the cavity surfaces for 30 seconds and then briefly air-dried to remove the solvent. Group C: The untreated dentin smear layer was used as a control. In all three groups, the cavities were filled incrementally with a resin-based composite (APX), light curing every increment for 40 seconds. After 30 minutes, the teeth were extracted atraumatically and the samples immediately prepared for evaluation with the transmission electron microscope. RESULTS: The use of a self-etching primer did not produce significant morphological changes in the moist dentin substrate. Adverse morphological conditions where observed when there was an excess water on the dentin surface. Phosphoric acid altered the collagen more severely than the self-etching primer.

Acid Etching, Dental↗
PubMed1990

Scalp cooling by cold air for the prevention of chemotherapy-induced alopecia.

A new system is described for cooling the scalp with cold air in order to prevent chemotherapy-induced alopecia. Compressed air was cooled by means of a vortex tube built into a hair-drier cap. This system reduced the blood flow in the scalp to 35%, the surface temperature to 14.2 degrees C and the intradermal temperature at hair follicle level to 29.2 degrees C. The low temperature could be kept constant for at least one hour of cooling. By means of comparison, with cryogel packs the lowest epidermal temperature attained was 17.9 degrees C; moreover, once this was reached after 10 min, it rapidly rose again to 20.6 degrees C after 40 min. Forty-eight patients receiving cytostatic treatment for breast cancer were subjected to scalp cooling with the cold air system, starting 15 min before chemotherapy and lasting for 90 min. With the system set at an air temperature of -12 degrees C, the treatment was well tolerated. Of the 13 patients treated with 40 mg/m2 doxorubicin in combination with other cytostatics, 6 had hair loss less than WHO grade 3, in contrast to 1 of 4 patients given cryogel packs. However, patients treated with epirubicin at 75 mg/m2 all showed grade 3 hair loss in spite of air cooling. In view of the possibility of achieving and maintaining low scalp temperatures, the cold air system is to be preferred to cryogel packs. Whether better clinical results may be obtained with cooling for longer periods and/or to lower temperatures remains to be determined.

Alopecia↗
PubMed1986

[Postoperative tension pneumocephalus--report of 3 cases].

Three cases of tension pneumocephalus are reported and pathogenesis, clinical features and management of this complication is discussed. Case 1: A 12-year-old female underwent a craniotomy for a suprasellar tumor following V-P shunting. At that time, Mayfield's pin fixing head holder was used and a CSF leak from a puncture wound caused by the head holder was noted postoperatively. Although she showed uneventful recovery from the anesthesia, several hours after surgery, she developed general convulsions and deteriorated. CT scan revealed a huge bifrontal accumulation of air compressing the entire brain postero-caudally. No active measures were taken to treat the intracranial air and a follow-up CT scan revealed a hemorrhagic infarction in the right occipital lobe possibly caused by transtentorial herniation. The patient remained in a vegetative state until her death three years later. Case 2: A 55-year-old man had a pansinectomy for sinusitis. Seven days later he developed CSF rhinorrhea and a severe headache. A CT scan revealed air in the subarachnoid space as well as in the ventricles. After repeated spinal taps, he became stuporous. An emergency repair of the CSF leak was performed. Intraoperatively, the accumulation of air was noted in the subarachnoid space under extreme tension. He made a full recovery. Case 3: A 69-year-old woman underwent a neck clipping for a ruptured anterior communicating aneurysm 2 days after the onset. Shortly before the craniotomy, a continuous spinal drainage system was installed. Postoperatively she did not recover from the anesthesia and a CT scan showed an accumulation of air in the bifrontal subdural space compressing the brain posteriorly.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1982

Subcutaneous and retropharyngeal emphysema following dental restoration: an uncommon complication.

A case of subcutaneous and retropharyngeal emphysema following a dental restoration is presented. The patient complained of swelling, tenderness, and a "crackling feeling" of her right face and neck, as well as pain in the back of her throat. Radiographs confirmed the diagnosis of interstitial air emphysema. The etiology of this unusual complication was the compressed air used in modern dental drills and syringes. Treatment consists of reassurance, observation, and prophylactic antibiotics. [Bavinger JV: Subcutaneous and retropharyngeal emphysema following dental restoration.

Dental Restoration, Permanent↗
PubMed2005

Remote atmospheric breakdown for standoff detection by using an intense short laser pulse.

A remote atmospheric breakdown is a very rich source of UV and broadband visible light that could provide an early warning of the presence of chemical-biological warfare agents at extended standoff distances. A negatively chirped laser pulse propagating in air compresses in time and focuses transversely, which results in a rapid laser intensity increase and ionization near the focal region that can be located kilometers away from the laser system. Proof-of-principle laboratory experiments are performed on the generation of remote atmospheric breakdown and the spectroscopic detection of mock biological warfare agents. We have generated third harmonics at 267 nm and UV broadband radiation in air from the compression and focusing of femtosecond laser pulses. Fluorescence emission from albumin aerosols as they were illuminated by the femtosecond laser pulse has been observed.

Journal Article↗
PubMed1981

Use of air entrainment masks during eye surgery.

Plastic drapes over the patient's face during eye surgery are necessary to maintain a sterile surgical field. We found that providing the patient with adequate inspiratory gas under these surgical drapes was a problem. We now use air entrainment oxygen masks to provide this surgical patient with a high flow gas source, nearer to peak inspiratory flows than the previously used nasal cannula. The mask is powered with compressed air or, if necessary, compressed oxygen. This practice has helped eliminate restlessness, smothering sensations, coughing, and sudden movements, which can result in disastrous complications during ophthalmic microsurgical procedures. Respiratory therapists can play a key role in explaining and adapting this system for eye surgery.

Anesthesia, Local↗
PubMed1999

Analysis of a simple biodegradation process for the removal of volatile organic chemicals from wastewater based on a gas stripping principle.

A simple biodegradation system consisting of an air stripping tank and a bioreactor was proposed for the treatment of volatile organic chemicals in wastewater. Toluene was used as a model of volatile organic chemicals. An aqueous solution of toluene and a basic mineral medium were placed in the air stripping tank and bioreactor, respectively. Toluene was stripped by supplying compressed air into the stripping tank through a sparger, and the stripped toluene was degraded by Pseudomonas putida mt-2 (ATCC 33015) in the bioreactor under aerobic conditions. The effect of the air stripping rate on bacterial growth was examined. A quantitative relationship was found between the air flow rate in the air stripping tank (Qa) and the stripping rate constant. During cultivation, the bacterial cells grew by utilizing toluene as the sole carbon source, and reached their maximum cell concentration (Xm) at the stationary phase. Xm showed a gradual decrease with increase in Qa from 1.8 to 7.2 l/h, indicating a decrease in the rate of toluene degradation with increasing Qa. The Xm at Qa=1.8 l/h was the highest among the experiments under different values of Qa, which was almost twice that at Qa=7.2 l/h. Mathematical analysis taking the growth kinetics and mass transfer of toluene into consideration satisfactorily explained the system performance.

Journal Article↗
PubMedDate not supplied

Effect of saliva contamination on the bond of dentin to resin-modified glass-ionomer cement.

This in vitro study compared the shear bond strength of a resin-modified glass-ionomer restorative material (Fuji II LC) bonded to saliva-contaminated dentin versus non-contaminated dentin. Seventy-five extracted human molar teeth were randomly divided into five groups of 15 samples each. The dentin was treated with 10% polyacrylic acid for 20 seconds, rinsed, and dried. The acid-treated dentin surfaces in Groups 1-4 were contaminated with saliva. In Group 1, the saliva was air thinned. In Groups 2-4, saliva was dried completely with compressed air. The saliva-contaminated dentin in Group 3 was rinsed and dried. The saliva-contaminated dentin in Group 4 was rinsed, dried, treated with 10% polyacrylic acid, and dried. Specimens in Group 5 received no contamination. The resin-modified glass-ionomer cement restorative material was mixed and applied to the dentin surfaces. Following placement of the restorative material and 7 days of storage, the specimens were thermo-cycled 300 times. Using the Instron Universal Testing Machine, a shear force was applied to the restorative material. Shear bond strength values were compared among the groups using a one-way ANOVA and Student-Neuman-Keuls Multiple Range Test (alpha = 0.05). The non-contaminated specimens (Group 5) were significantly stronger than the contaminated specimens (Groups 1-4). There were no significant differences in bond strength among the groups containing contaminated specimens. Salivary contamination occurring after dentin etching significantly reduced the bond strength of the resin-modified glass-ionomer restorative material to dentin. Neither rinsing nor rinsing and re-etching resulted in bond strengths as great as to non-contaminated dentin.

Analysis of Variance↗
PubMed1982

Can pulmonary barotrauma cause cerebral air embolism in a non-diver?

It is generally assumed that only the diver exiting a compressed air environment is at risk for the complications of systemic air embolism following pulmonary barotrauma. We present a case of sudden death following a swimming pool dive, with evidence supporting a diagnosis of fatal systemic air embolism.

Adult↗
PubMed2001

Chronic tobacco smoke exposure increases cough to capsaicin in awake guinea pigs.

Chronic exposure to irritants such as tobacco smoke (TS) can induce spontaneous and enhanced irritant-induced coughing, especially in asthma. To determine if the mechanism of enhanced coughing involves activation of capsaicin-sensitive sensory receptors (C-fibers), we exposed both non-sensitized (NS) and ovalbumin-sensitized guinea pigs to TS (5 mg/L air, 30 min exposure, and 7 days/week). Similar groups were exposed to compressed air. After 90 days of exposure, we challenged the airways with capsaicin, bradykinin, histamine and methacholine. Capsaicin induced coughing as well as bronchoconstriction in guinea pigs exposed to TS. In ovalbumin (OA) guinea pigs coughing and bronchoconstriction were enhanced. Tachykinin receptor antagonists attenuated coughing to both capsaicin and acute TS challenge. Bradykinin also induced coughing and bronchoconstriction in guinea pigs exposed to TS. There was no statistical separation between the two TS groups however. Histamine and methacholine induced similar bronchoconstriction but fewer coughs in all four experimental groups. In conclusion, chronic TS exposure induced coughing to capsaicin and bradykinin challenge. The effect of capsaicin was further enhanced in OA guinea pigs. Enhanced coughing induced by TS exposure likely involves activation of capsaicin-sensitive sensory C-fibers and neuropeptide release with possible subsequent activation of rapidly-adapting receptors.

Aerosols↗
PubMedDate not supplied

Microleakage of compomer restorations in primary teeth after preparation with bur or air abrasion.

This study compared the degree of marginal leakage of a compomer in Class V cavities of human primary molars prepared by a conventional dental bur and air abrasion with or without acid etching. Fifty-six non-carious extracted primary molars were randomly divided into four groups (n=14) to be prepared by four techniques: Group-1: Bur followed by acid etching: Class V cavity preparations were placed on the buccal surfaces of each tooth using a high-speed handpiece. The preparations were 1.5-mm deep, 3-mm long and 2-mm wide, with the occlusal margin in enamel and the cervical margin extending 0.5 mm below the cementoenamel junction. The preparations were acid etched with 37% phosphoric acid starting at the enamel margins for 30 seconds and rinsed with water for 20 seconds. The preparations were then restored with Compoglass F. 2-Group 2: Bur: The preparations and the treatment procedures were the same as in Group 1, with the exception of 37% phosphoric acid application. Group 3: Air abrasion followed by acid etching: Class V cavity preparations were placed on the buccal surfaces of each tooth using a handpiece of an air-abrasive system (PrepStart, Danville Engineering). The system was supplied with dry compressed air at 80 psi. In all tests, the air-abrasion system was operated with an 80 degrees-angle handpiece tip and 50-mm aluminum oxide particles. A tip with a 0.38-mm inner diameter was used at a 2-mm distance. The treatment procedures were the same as in Groups 1 and 2. Group 4: Air abrasion: The preparations and treatment procedures were the same as in Group 3, with the exception of 37% phosphoric acid. After finishing the restorations, the teeth were stored in distilled water at 37 degrees C for 24 hours. The samples were thermocycled for 500 cycles between 5 degrees C and 55 degrees C with a dwell time of 30 seconds. The samples were then immersed in 0.5 percent basic fuchsin dye for 24 hours at 37 degrees C. The surface-adhered dye was then rinsed in tap water and the teeth were embedded in a chemically-activated acrylic resin and bisected longitudinally in a mesiodistal direction with a low speed diamond disk. Each section was examined under a stereomicroscope (Nikon, Tokyo, Japan) at 20x magnification. The data were analyzed statistically by Kruskal-Wallis analysis of variance to determine any statistical significant differences in microleakage scores among the groups at a p-value of 0.05. Also, the enamel versus cementum-dentin microleakage scores of each group were compared using z-test at the 0.05 significance level. There was no statistically significant difference among the groups (p>0.05), but a statistical difference between enamel and cementum-dentin surfaces was evaluated (p<0.05).

Acid Etching, Dental↗
PubMed1980

A new respiratory protective device.

This paper describes a new respiratory protective device for use in dangerous environments. The new system provides a lightweight alternative to present compressed air systems and a safe alternative to present pure oxygen respirator systems. The new system utilizes electronically controlled valves, two breathing bags, and a small, compressed supply of oxygen-rich air to achieve these goals. A prototype backpack system very adequately demonstrated the feasibility of such a system as a useable device for respiratory protection.

Environmental Exposure↗
PubMed1977

Altitude decompression sickness: hyperbaric therapy results in 145 cases.

Most cases of decompression sickness that occur at altitude resolve upon descent to lower altitudes. Before the use of hyperbaric therapy, cases that did not resolve accounted for some of the most difficult medical management problems in military aerospace medicine. On 27 March, 1941, the U.S. Navy Diving School successfully used hyperbaric therapy for a case of altitude-induced decompression sickness that did not resolve on return to ground level. Since then, over 145 such cases have been treated by hyperbaric therapy. At first, treatments involved using compressed air, with varying success. Current medical management of altitude-induced decompression sickness requires immediate compression to 2.8 ATA, equivalent to 60 ft of sea water (FSW) pressure, and a series of intermittent oxygen and air breathing periods during the subsequent slow decompression to surface. This report confirms the treatment recommendations set forth by Behnke and Downey, and crystallized by Goodman in 1964. Conclusions are based on treatment experience in the management of 120 cases in U.S. Air Force hyperbaric chambers, and a survey of hyperbaric facilities which have treated 25 other cases.

Adult↗
PubMed1996

An on-demand system of delivering pre-mixed inspiratory gas for use during physical activity.

This study analysed the effectiveness of an on-demand system of supplying pre-mixed inspiratory gases to subjects under working conditions. A supply of pre-mixed inspiratory gas is often required in order to study the effects of acute hypoxia/hyperoxia on numerous physiological variables whilst normobaric pressure is maintained. The principle aim of this investigation was to determine if the introduction of the on-demand system resulted in any changes in minute ventilation (VE), oxygen consumption (VO2), respiratory rate (RR), tidal volume (VT) or endurance performance during incremental cycle ergometry to exhaustion. Trained male subjects participated in the study (n = 9). The subjects completed two incremental trials on a Monark cycle ergometer. The trials commenced at a power output of 60W implementing a 30 W.4 min-1 work increment. In one trial the subjects inspired ambient room air as per normal VO2max testing, whilst in the other trial the subjects inspired compressed air supplied from high pressure cylinders using a demand valve. Trial order was randomised. Raw data (time, heart rate, VI[ATPS], respiratory rate, tidal volume, FEO2 and FECO2) were recorded on line every 15 seconds. No differences in gas exchange variables were apparent at rest (VO2 VE RR, VT) nor during submaximal work between normal and on-demand trials. VO2max, VEmax and physical performance were also not significantly different between trials. On the basis of these findings, it was suggested that the on-demand system of supplying inspiratory gas resulted in minimal changes in gas exchange variables and performance during incremental work. Using this system of gas supply researchers can effectively supply subjects with premixed gas for little financial expense.

Adult↗
PubMedDate not supplied

Cervicofacial and mediastinal emphysema as the result of a dental procedure.

Cases of cervicofacial subcutaneous emphysema occurring during dental treatment often result from the use of air-water cooled dental drills during tooth extraction. A case is presented in which a compressed air syringe, used to dry the field, caused diffuse cervicofacial emphysema with retropharyngeal and mediastinal extension. The point of entry appeared to be a 4 mm superficial laceration of the buccal mucosa. Despite the size of the wound, a significant amount of air was able to enter the tissues and spread quite distantly. Though many cases of subcutaneous emphysema go unnoticed, diffuse extension, especially with involvement of deep neck structures and with thoracic extension, must be recognized as they can be potentially life-threatening.

Cheek↗
PubMed2001

Chronic tobacco smoke exposure increases airway sensitivity to capsaicin in awake guinea pigs.

Tobacco smoke (TS) exposure induces airway hyperreactivity, particularly in sensitive individuals with asthma. However, the mechanism of this airway hyperreactivity is not well understood. To investigate the relative susceptibility of atopic and nonatopic individuals to TS-induced airway hyperreactivity, we exposed ovalbumin (OA)-sensitized and nonsensitized guinea pigs to TS exposure (5 mg/l air, 30-min exposure, 7 days/wk for 120-156 days). Two similar groups exposed to compressed air served as controls. Airway reactivity was assessed as an increase in enhanced pause (Penh) units using a plethysmograph that allowed free movement of the animals. After 90 days of exposure, airway reactivity increased in OA-TS guinea pigs challenged with capsaicin, bradykinin, and neurokinin A fragment 4--10 aerosols. In addition, substance P content increased in lung perfusate of OA-TS guinea pigs in response to acute TS challenge compared with that of the other groups. Airway hyperirritability was not enhanced by phosphoramidon but was attenuated by a cocktail of neurokinin antagonists, nor was airway hyperreactivity observed after either methacholine or histamine challenge in OA-TS guinea pigs. Chronic TS exposure enhanced neither airway reactivity to histamine or methacholine nor contractility of isolated tracheal rings. In conclusion, chronic TS exposure increased airway reactivity to capsaicin and bradykinin aerosol challenge, and OA-TS guinea pigs were most susceptible to airway dysfunction as the result of exposure to TS compared with the other groups. Increased airway reactivity to capsaicin suggests a mechanism involving neurogenic inflammation, such as increased activation of lung C fibers.

Administration, Inhalation↗