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Biomedical subjects

H Toyooka

Publications and source records attributed to H Toyooka.

At least 163 records · Page 9Linked to original sources
PubMed1993

Radiopacity of 12 visible-light-cured dental composite resins.

The radiopacity of 12 VL-cured composite resins was determined with reference to an aluminum step-wedge. Two anterior composites were radiolucent while two anterior and one anterior/posterior composites exhibited the radiopacity equal to, or slightly greater than, that of human enamel. Three posterior and one inlay composites possessed the radiopacity equivalent to, or in tiny excess of, that of human enamel. Three posterior composites had the radiopacity, fairly exceeding that of human enamel. Chemical analyses of the filler particles were carried out with SEM/EDX. It became evident that radiopaque fillers contained at least one radiopaque oxide component such as BaO, ZrO2 and Yb2O3 with varying concentrations. In general, the radiopacity of the composite resin was linearly proportional to the amount of the radiopaque oxide in the filler. It was suggested that ZrO2 was radiopacifier equivalent to, or even stronger than, BaO.

Composite Resins↗
PubMed1993

Hardness and fracture toughness of commercial core composite resins.

One important mechanical property of core composite resins is fracture toughness, KIC, which expresses serviceability in the oral cavity, such as the resistance to marginal fracture. KIC values of eight commercial core composite resins were examined by the single-edge notched-beam (S.E.N.B.) method. Two composites containing about 80 wt% Si3N4 fillers exhibited both the highest KIC value of around 2.0 MN.m-3/2 and the highest hardness value. The other six composites containing 66 to 86 wt% SiO2-based fillers had KIC values of around 1.2 to 2.0 MN.m-3/2, and there was a tendency toward higher KIC values as hardness increased. It was speculated that the clinical acceptability of core composite resins could be broadened, if dental clinicians selected composites with higher KIC values.

Composite Resins↗
PubMed1993

[Effects of laryngeal mask airway on circulation and on incidence of postoperative sore throat and hoarseness].

We studied the effects of laryngeal mask airway (LM) insertion on circulation and on the incidence of postoperative sore throat or hoarseness as compared with tracheal intubation in 50 pediatric patients. LM insertion caused less change of heart rate and systolic blood pressure than tracheal intubation. The incidence of postoperative sore throat and hoarseness was less in the patient of LM group. We conclude that LM is useful in pediatric anesthesia when less circulatory changes are desirable or when the postoperative sore throat or hoarseness is to be avoided.

Anesthesia, General↗
PubMed1993

[Anesthetic management of a patient with a history of right upper lobectomy for esophageal resection via left thoracotomy].

We anesthetized a patient for esophageal resection in a right lateral decubitus position, because of his right pleural adhesion after lobectomy for tuberculosis. Although hypoxemia was expected on left lung compression during the surgery, oxygenation was not compromised. A good ventilation/perfusion relationship might have been maintained in both the right and left lungs during the procedure.

Anesthesia, Epidural↗
PubMed1993

[The anesthetic management of Arnold-Chiari malformation with spinal cord injury].

A rare case of spinal cord injury at C3 level associated with Arnold-Chiari malformation is reported. A 33 year old male was admitted with a complaint of walking difficulty. MRI revealed cerebellar herniation, and a plain X-ray showed spinous process adhesion of C2-3 and slight scoliosis. Percent vital capacity was reduced to 69%, and blood cell count showed a slight anemia. The patient was anesthetized for an orthopedic surgery with pethidine 70 mg, thiamylal 200 mg, 60% nitrous oxide, 40% oxide, and 0.5-1.2% isoflurane. There was a mild decrease in arterial blood pressure during surgical procedures, but this could be easily treated by fluid therapy, and there was no episode of autonomic hyperreflexia. Postoperative course of the patient was uneventful, except a transient pneumonia and urinary tract infection. The key in the anesthetic management of Arnold-Chiari malformation with spinal cord injury is the control of intracranial pressure, care for respiratory dysfunction and the prevention of infection as well as autonomic hyperreflexia.

Adult↗
PubMed1992

Dobutamine increases diaphragmatic contractility in dogs.

The effects of dobutamine on diaphragmatic contractility were studied in 24 dogs anaesthetized with secobarbital and receiving mechanical lung ventilation. The phrenic nerves were stimulated supramaximally for two seconds with electrodes placed around the fifth and sixth cervical roots when the airway was closed at the level of FRC. The stimulating frequency ranged from 10 to 100 Hz. Transdiaphragmatic pressure gradient (Pdi) generated by the electrophrenic stimulation was used as an index of diaphragmatic contractility. The electrical activity of the diaphragm during the stimulation (Edi) was also measured with needle electrodes inserted in the right hemidiaphragm percutaneously. During an infusion of dobutamine (10 micrograms.kg-1.min-1 for 20 min), Pdi increased by 15 +/- 2.1% of control value at 20 Hz stimulation (P less than 0.01), and by 13 +/- 1.2% at 100 Hz stimulation (P less than 0.01). The Edi was not altered by dobutamine infusion. This enhancement of Pdi by dobutamine was abolished by simultaneous infusion of nicardipine, a Ca-channel blocker, but was not affected by prostaglandin E1. These results suggest that dobutamine has a stimulating effect on canine diaphragmatic contraction, and this action may be related to the increased inward movement of extracellular calcium.

Alprostadil↗
PubMed1992

Sternocleidomastoid muscle contractility at different levels of isoflurane anaesthesia in humans.

We have measured force-frequency curves of the sternocleidomastoid muscle in six patients at three different levels of isoflurane anaesthesia (1.0, 1.4 and 1.8 MAC). Spontaneous ventilation was suppressed by mild hypocapnia induced by mechanical ventilation. An anterior force vector of the sternocleidomastoid muscle was measured during isometric contraction induced by supramaximal electrical stimulation at 20, 50 and 100 Hz to the i.m. accessory nerves of the muscle. The force response at 20 Hz and 50 Hz did not change with an increase in isoflurane concentration, but it decreased at 100 Hz as isoflurane concentration increased. The reduction in the force at 100 Hz may be caused mainly by impaired neuromuscular transmission.

Adolescent↗
PubMed1991

Diaphragmatic fatigue and its recovery are influenced by cardiac output.

The effects of cardiac output (Qt) on diaphragmatic blood flow (Qdi) and diaphragmatic fatigue and its recovery were studied in dogs. Qdi was estimated by measurement of the left inferior phrenic arterial blood flow (QdiL). There was a significant positive correlation between % Qt and % QdiL. Transdiaphragmatic pressure (Pdi) was significantly smaller in the lowered Qt group than the control at the end of fatigue, and the speed of recovery from the fatigue was also significantly slower in the lowered Qt group. It is concluded that Qt was considered to play an important role in the pathogenesis of diaphragmatic fatigue and its recovery in the mechanically ventilated dogs.

Journal Article↗
PubMed1991

A close relationship between post-tetanic twitch and train-of-four responses during neuromuscular blockade by vecuronium.

The relationship between post-tetanic twitch (PTT) and train-of-four (TOF) responses after intravenous administration of vecuronium were studied using EMG in 20 patients under nitrous oxide and enflurane anesthesia. After the initial dose (0.2 mg.kg(-1)) of vecuronium, the detectable first twitch of PTT (PTT(1)) always preceded that of TOF (TOF(1)) with the mean time interval of 10.7 +/- 2.6 min. The post-tetanic count (PTC) which coincided with the first appearance of TOF(1) was 9.4 +/- 2.6. After the appearance of TOF(1), the magnitude of TOF(1) was almost identical to that of PTC(10) until full recovery from neuromuscular blockade was observed, whether the supplemental doses of vecuronium (0.03-0.04 mg.kg(-1) i.v.) were administered or not. The magnitude of TOF(2) was slightly lower than that of PTC(20). These results suggest that there is a close relationship between these two types of response, and by evaluating not only PTC but also the magnitude of each PTT, the recovery of TOF responses can be predicted and its extent be estimated fairly accurately.

Journal Article↗
PubMed1991

[Diaphragmatic fatigue and its recovery are influenced by markedly decreased cardiac output: possible involvement of neuromuscular junction].

Effects of highly decreased cardiac output on the development and recovery of diaphragmatic fatigue were studied in dogs. The fatigue was induced by supramaximal electrical stimulation (20 Hz) of phrenic nerves for 30 minutes. Cardiac output was reduced during this period to 30% of control value by mechanically obstructing inferior vena cava with a balloon in animals with lowered cardiac output group (lowered Qt group). Cardiac output was maintained at normal value throughout the experiment in animals of the other group (control group). The animals were observed for recovery for 60 minutes after induction of the fatigue. The standardized transdiaphragmatic pressure (Pdi/Pdi 100) and integrated electromyographic activity (Edi/Edi 100) elicited by electrical test stimuli (20, 100 Hz) were significantly lower in lowered Qt group (P less than 0.01) during entire fatigue and recovery period. The decrease of Pdi/Pdi 100 and Edi/Edi 100 at high frequency test stimuli (100 Hz) was observed only in lowered Qt group. These results suggest that when cardiac output is severely decreased the diaphragm is more susceptible to fatigue, and that this may be caused by a failure of neuromuscular junction as well as by an impaired excitation-contraction coupling.

Animals↗
PubMed1990

Tracheobronchial dilating effect of high frequency jet ventilation.

Effect of high frequency jet ventilation (HJFV) on tracheobronchial tone was examined in anesthetized dogs. Changes in intraluminal pressure of water-filled endotracheal cuff (Pcuff) were used as an indicator of tracheal smooth muscle tone. Animals were initially ventilated with conventional mechanical ventilation (CMV) to maintain normal Pa(CO)(2). HFJV (2.0 Hz.) was then applied to each animal in such a way to maintain the same mean airway pressure and Pa(CO)(2) as in CMV. Immediately after changing CMV to HFJV, Pcuff decreased significantly and remained decreased during the period of HFJV. After changing HFJV to CMV, Pcuff gradually returned to its previous level. Histamine-induced tracheobronchial constriction was partially released by HFJV as shown by a decrease in Pcuff and airway resistance (Raw) and by an increase in static lung-thorax compliance (Cst) measured immediately after the cessation of HFJV. These results suggest that HFJV has a tracheobronchial dilating action, presumably mediated by pulmonary stretch reflex, and this may be one of the mechanisms of an increase in mucous secretion and of other reported favorable effects of HFJV in some types of respiratory failure.

Journal Article↗
PubMed1990

Plasma alpha-atrial natriuretic peptide concentrations in acute respiratory failure associated with sepsis: preliminary study.

Plasma alpha-atrial natriuretic peptide (alpha-ANP) concentrations were measured during mechanical ventilation in nine patients with acute respiratory failure (ARF) associated with sepsis. The relationships between alpha-ANP and pulmonary hemodynamic variables were examined. A total of 22 measurements of alpha-ANP and other variables were obtained. The mean plasma alpha-ANP concentration of 22 measurements was 120.1 +/- 79.8 pg/ml (normal 31.7 +/- 12.0, mean +/- SD). Plasma alpha-ANP concentrations correlated with mean pulmonary artery pressure (MPAP) (r = .703, p less than .01) and pulmonary vascular resistance (PVR) (r = .606, p less than .01), but not with other variables. These findings suggest that alpha-ANP elevation may be related to the increases in MPAP and PVR in ARF associated with sepsis.

Aged↗
PubMed1990

[Impairment of neuromuscular transmission in fatigued canine diaphragm].

The role of impairment of neuromuscular transmission in fatigued canine diaphragm was investigated by comparing the function of fatigued diaphragm with that of neuromuscular junction (NMJ)-blocked diaphragm. Diaphragmatic fatigue was produced by intermittent supramaximal stimulation of bilateral phrenic nerves. Partial NMJ blockade was obtained by vecuronium bromide administered intravenously. During control study, no fade was observed either in integrated diaphragmatic electric activity (Edi) or transdiaphragmatic pressure (Pdi). In fatigued diaphragm, Edi generated by 100 Hz showed a remarkable fade. The fade was prominent in high frequency fatigue. In NMJ-blocked diaphragm, fade was observed in Pdi as well as in Edi produced by 100 Hz. The fade of Edi by 100 Hz was prominent. In low frequency fatigue, both Pdi and Edi produced by 20 Hz test stimulation were significantly lower than control values. These results show that in addition to impairment of excitation-contraction coupling, neuromuscular blockade is involved, at least in part, in low frequency diaphragmatic fatigue.

Animals↗
PubMed1989

[Laryngeal mask--a newly designed oral airway].

A newly developed oral airway, laryngeal mask (LM), was used in 40 patients by anesthesiologists of varied clinical experiences. Clear airway was obtained in 37 patients (92.5%). There were 3 patients in whom it was difficult to establish clear airway, probably because of inappropriate fitting of mask to larynx or of folding of epiglottis. Controlled or assisted ventilation was performed adequately in most of the patients, but there was recognizable gas leak in 13 patients when the airway pressure was above 15 cmH2O. The LM has many attractive features compared with a traditional face mask, and some of the promising clinical applications of LM are discussed.

Adolescent↗
PubMed1989

[Mass flow anesthesia delivery system and its application].

Microcomputer-based anesthesia delivery system using mass flow control devices has been developed. System is superior in computer control to conventional anesthesia machine because there is no mechanical setting. System consists of three thermal mass flow controllers (TMFC), one vapor source controller (VSC), personal computer system, and air circuits. Personal computer system has facilities of digital output, analogue input and analogue output interfaces. TMFCs and VSC are devices which operational principle is based on the thermal conductance and they are controlled by electrical signals from computer in the system. TMFCs control the mass flow of nitrous oxide, oxygen and carbon oxide according to each input voltage signal. VSC regulates mass vapor of halothane in order to keep set value up by means of alteration of oxygen carrier gas flow. Computer always monitors the gas flow of the TMFCs and VSC so that computer compensates the change of the carrier gas flow of VSC by regulating the TMFC for oxygen. Mixed gas from TMFCs and VSC is supplied through the air circuit to subject. Characteristics of the system was measured by mass spectrometer and flowmeter. Stability was 0.05% change after 30 minutes at the initial set of 3%. Experiment on animals using mongrel dogs has been performed to verify the system functions.

Anesthesia, Inhalation↗
PubMed1989

[Anesthetic management of a patient with perforated necrotic trachea after radical esophageal cancer surgery].

We anesthetized a 69-year-old man with perforated necrotic trachea after radical esophageal cancer surgery. We recognized during the reoperation that necrotizing part of the trachea was perforated from the cricoid cartilage to 2cm above the carina. We ventilated the both lungs successfully without leaks by inserting a double-lumen tube into the trachea after tracheostomy. Postoperatively, the carina and the main bronchi were also necrotized and perforated. We ventilated the both lungs without leaks by inserting two single-lumen tubes into the left and right bronchi separately. But, eventually the distal part of the both bronchi was also necrotized and perforated. Finally, the patient died of respiratory failure due to hypoventilation on the 7th day after the re-operation. We should remember this type of emergency complication after radical esophageal cancer surgery.

Aged↗
PubMed1987

CO2 rebreathing of T-piece system in patients during recovery phase from acute respiratory failure.

Eight respiratory parameters which might affect the amount of carbon dioxide rebreathing were assessed in seven patients who were breathing spontaneously from large-bore T tube system during the recovery phase from acute respiratory failure. With multivariate regression analysis, the absolute amount of rebreathed CO2 at the connector of endotracheal tube (VINSPCO2) were approximately estimated by using relatively small number of parameters, including minute volume (VEXP), fresh gas inflow to T piece system (VFGI) and preferably by additional parameters concerning CO2 output of the patients.CO2 rebreathing ratio, VINSPCO2 divided by gross outward flux of CO2 at the connector (VEXPCO2), was predicted with simple regression equation by using (VEXP/VFGI) as follows,(VINSPCO2)/(VEXPCO2) = 0.405 + 0.33 x ln (VEXP/VFGI)The maximum (VEXP/VFGI) ratio to prevent rebreathing of CO2 at the connector was 0.30, whereas the ratio to prevent CO2 accumulation due to rebreathing was 0.45.

Journal Article↗