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Biomedical subjects

S Isono

Publications and source records attributed to S Isono.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effects of tongue electrical stimulation on pharyngeal mechanics in anaesthetized patients with obstructive sleep apnoea.

The tongue plays a significant role in the maintenance of a patent airway. The purpose of this study was to examine the effects of tongue musculature contraction on the static mechanical properties of the pharynx in patients with obstructive sleep apnoea (OSA). During hyperventilation-induced apnoea in seven OSA patients anaesthetized with sevoflurane, the static pressure/area relationships of the oropharynx were obtained by means of step changes in airway pressure while endoscopically measuring cross-sectional area. At each airway pressure, the tongue was electrically stimulated via electrodes placed bilaterally. Tongue electrical stimulation (TES) did not further dilate the oropharyngeal area at higher airway pressure (3.2+/-1.9 versus 3.0+/-2.1 cm2), although the narrowed oropharyngeal area at lower airway pressures increased during TES (0.8+/-9.0) versus 1.7+/-1.8 cm2, p<0.05). Accordingly, the slope of the pressure/area relationship decreased during TES (0.24+/-0.20 versus 0.12+/-0.09 cm2 x cm H2O(-1), p<0.05). In conclusion, electrical stimulation of the tongue stiffens the retroglossal airway wall in patients with obstructive sleep apnoea.

Adult↗
PubMed1999

Sleep-disordered breathing in acromegalics--relation of hormonal levels and quantitative sleep study by means of bedside oximeter.

Sleep-disordered breathing (SDB) is common in patients with growth hormone (GH) secreting pituitary adenomas. Since long-term untreated SDB aggravates systemic conditions (hypertension and arrhythmia etc.), the therapeutic outcome of SDB is important in reducing morbidity and mortality rates. But the results of a quantitative analysis of the lowered GH and IGF-1 levels in SDB in a relatively large number of patients are not detailed. Ten consecutive acromegalic patients were studied with a bedside oximeter. Preoperatively they were divided into two groups based on the presence (SDB group = 6 patients) or absence (non-SDB group = 4 patients) of clinical symptoms of SDB such as habitual snoring, excessive daytime somnolence and nocturnal apneic episodes. The serum IGF-1 averaged 931.7 ng/ml in SDB group and 898.3 ng/ml in non-SDB group. The oxygen desaturation index (ODI) (the number of oxygen desaturations exceeding 4% from the base line) was 29.1+/-15.4 in the SDB group and 2.5+/-1.8 in the non-SDB group (P=0.01). Other oximeter parameters such as the percent of the time spent at O2 saturation < 90% and the mean and the lowest O2 saturations closely correlated with the degree of the clinical symptoms. A postoperative sleep study was conducted in 5 patients in the preoperative SDB group, 4 months or more after the surgery. The serum GH and IGF-1 levels normalized in 3 patients but remained slightly high in 2. ODI became 9.1+/-5.6, which was significantly lower than the preoperative value (P=0.026). One patient had a complete clinical resolution. The other 4 obtained slight to moderate improvement clinically and oximetrically despite normalized or decreased hormonal levels. This study clarified that the response of SDB to lowering of the GH level varies from one patient to another and persisting SDB despite the normalization of the hormonal levels suggests the involvement of other factors in the production of SDB.

Acromegaly↗
PubMed1998

Preoperative nocturnal desaturations as a risk factor for late postoperative nocturnal desaturations.

Severe postoperative hypoxaemia during sleep may increase the risk of postoperative cardiovascular complications. We hypothesized that the severity of hypoxic episodes after surgery are related to the presence of preoperative sleep-disordered breathing (SDB). We tested this hypothesis in a multicentre study designed to elucidate the major risk factors for development of postoperative nocturnal desaturations. We performed overnight oximetry before operation and for one night between the second and fourth day after operation in 80 patients undergoing major surgery. We calculated oximetry variables such as oxygen desaturation index (ODI), defined as the number of oxygen desaturations exceeding 4% below baseline, percentage time spent at SpO2 < 90% (CT90, %) and lowest SpO2 value. After operation, although the change in ODI was not significant (P = 0.34), deterioration in CT90 and lowest SpO2 values were significant (P = 0.036 and P = 0.007, respectively). Multivariate analysis of possible risk factors for postoperative desaturations revealed that preoperative hypoxaemia and apnoea witnessed by others were highly correlated with postoperative hypoxaemia.

Adult↗
PubMed1998

Upper airway reflexes during a combination of propofol and fentanyl anesthesia.

BACKGROUND: The effects of intravenous anesthetics on airway protective reflexes have not been fully explored. The purpose of the present study was to characterize respiratory and laryngeal responses to laryngeal irritation during increasing doses of fentanyl under propofol anesthesia. METHODS: Twenty-two female patients anesthetized with propofol and breathing through the laryngeal mask airway were randomly allocated to three groups: (1) eight patients who received cumulative total doses of 200 microg fentanyl given in the form of two doses of 50 microg and one dose of 100 microg spaced 6 min under mechanical controlled ventilation while end-tidal carbon dioxide tension (PCO2) was maintained at 38 mmHg (fentanyl-controlled ventilation group), (2) eight patients who received cumulative total doses of 200 microg fentanyl while breathing spontaneously while end-tidal PCO2 was allowed to increase spontaneously (fentanyl-spontaneous ventilation group), and (3) six spontaneously breathing patients who were anesthetized with propofol alone (propofol group). The laryngeal mucosa of each patient was stimulated by spraying the cord with distilled water, and the evoked responses were assessed by analyzing the respiratory variables and endoscopic images. RESULTS: Before administration of fentanyl, laryngeal stimulation caused vigorous reflex responses, such as expiration reflex spasmodic panting, cough reflex, and apnea with laryngospasm. Increasing doses of fentanyl reduced the incidences of all these responses, except for apnea with laryngospasm, in a dose-related manner in both the fentanyl-controlled ventilation and the fentanyl-spontaneous ventilation groups. Detailed analysis of endoscopic images revealed several characteristics of laryngeal behavior during the airway reflex responses. CONCLUSION: Incremental doses of fentanyl depress airway reflex responses in a dose-related manner, except for apnea with laryngospasm.

Adult↗
PubMed1998

Hypercapnia enhances the development of coughing during continuous infusion of water into the pharynx.

We investigated the effects of increasing CO2 ventilatory drive on the coordination of respiration and reflex swallowing elicited by continuous infusion of distilled water into the pharynx (2.5 ml/min) in 11 normal subjects. Ventilation was monitored using a pneumotachograph and swallowing was recorded by submental electromyogram. The CO2 ventilatory drive was increased by addition of external dead space, while ventilation, the frequency of swallows, and the timing of swallows in relation to the phases of the respiratory cycle were measured at steady-state conditions. We found that the CO2 ventilatory response is not influenced by continuous reflex swallowing but that hypercapnia influences the timing and frequency of these swallows. Signs of aspiration were never observed during continuous infusion of water at eucapnia, but seven of 11 subjects showed laryngeal irritation and/or pending aspiration during hypercapnia, and the incidence of laryngeal irritation was higher the greater the PCO2. Detailed analysis of laryngeal irritations consisting of single coughs in seven subjects revealed that the majority of laryngeal irritations occurred when swallows coincided with expiratory-inspiratory transition or when swallows coincided with inspiration, whereas laryngeal irritation after an expiratory swallow was never observed. These results suggest that the automatic respiratory control system is not influenced by continuous swallowing but that the coordination of swallowing and respiration may be compromised during hypercapnia.

Adult↗
PubMed1998

Comparison of static mechanical properties of the passive pharynx between normal children and children with sleep-disordered breathing.

Collapsibility of the active pharynx, where active contraction of the upper airway muscles is evident, was previously reported to be higher in children with obstructive sleep apnea (OSA) than in those with primary snoring during sleep. Contribution of neuromuscular and anatomic factors to the increased collapsibility, however, was not estimated. We therefore evaluated collapsibility of the passive pharynx, in which upper airway muscle activities were eliminated. Our aim in the present study was to test the hypothesis that children with sleep-disordered breathing (SDB) have a structurally narrowed and a more collapsible pharynx compared with normal children. The static pressure/area relationship of the passive pharynx was endoscopically quantified in 14 children with SDB and in 13 normal children under general anesthesia with complete paralysis. The majority of children with SDB primarily closed their airways at levels of enlarged adenoids and tonsils with positive closing pressure (Pclose) (3.5+/-4.3 cm H2O), whereas half of the normal children closed their airways at the soft palate edges and the other half at the tongue bases with subatmospheric Pclose (-7.4+/-4.9 cm H2O). Cross-sectional area of the narrowest segment was significantly smaller in SDB children than in normal children. Interestingly, collapsibility of the retropalatal and retroglossal segments significantly increased in SDB children, compared with the normal subjects. We conclude that anatomic factors play a significant role in the pathogenesis of pediatric OSA and that predisposing structural abnormalities of the entire pharynx are likely to contribute to manifestation of OSA in addition to enlarged adenoids and tonsils.

Adenoids↗
PubMed1998

Effects of negative pressure assisted ventilation on dyspnoeic sensation and breathing pattern.

Although negative pressure assisted ventilation with an assist-control mode may have a potential therapeutic role in the treatment of severe dyspnoea, the effects of negative pressure assisted ventilation with the assist-control mode on dyspnoea and breathing patterns have not been examined. We examined the effects of negative pressure assisted ventilation with the assist-control mode on dyspnoea and breathing patterns produced by a combination of resistive loading and hypercapnia in nine healthy subjects breathing spontaneously. Subjects were asked to rate their sensation of respiratory discomfort using a visual analogue scale. Negative pressure assisted ventilation caused a significant reduction in sensation of respiratory discomfort from a visual analogue scale score of 74 (55-91) (median (range)) before negative pressure assisted ventilation to 34 (15-53) during negative pressure assisted ventilation (p<0.01). During negative pressure assisted ventilation, there were significant changes in breathing patterns characterized by an increase in tidal volume and a decrease in respiratory frequency, while neither minute ventilation nor end-tidal carbon dioxide tension changed. Our results indicate that negative pressure assisted ventilation with the assist-control mode is effective in relief of dyspnoea and that negative pressure assisted ventilation influences the control of breathing to minimize respiratory discomfort.

Adult↗
PubMed1998

[Influence of sevoflurane on renal medullary blood flow in humans].

Proper anesthetic management is necessary to preserve renal function during anesthesia and surgery. Using ultra-sound color Doppler, we examined the influence of sevoflurane on renal medullary blood flow in 20 adult patients without renal dysfunction. After identifying an interlobar artery in the outer medulla, we measured the velocity of the arterial blood flow before induction of anesthesia, and during sevoflurane anesthesia (1 MAC, 1.5 MAC). The minimum velocity of the interlobar arterial blood flow (Vmin) during wakefulness correlated significantly with creatinine clearance measured preoperatively. We did not find any significant change in Vmin after induction of sevoflurane anesthesia, despite significant decreases in mean arterial blood pressure.

Adult↗
PubMed1997

Pharyngeal patency in response to advancement of the mandible in obese anesthetized persons.

BACKGROUND: During anesthesia in humans, anterior displacement of the mandible is often helpful to relieve airway obstruction. However, it appears to be less useful in obese patients. The authors tested the possibility that obesity limits the effectiveness of the maneuver. METHODS: Total muscle paralysis was induced under general anesthesia in a group of obese persons (n = 9; body mass index, 32 +/- 3 kg[-2]) and in a group of nonobese persons (n = 9; body mas index, 21 +/- 2 kg[-2]). Nocturnal oximetry confirmed that none of them had sleep-disordered breathing. The cross-sectional area of the pharynx was measured endoscopically at different static airway pressures. A static pressure-area plot allowed assessment of the mechanical properties of the pharynx. The influence of mandibular advancement on airway patency was assessed by comparing the static pressure-area relation with and without the maneuver in obese and nonobese persons. RESULTS: Mandibular advancement increased the retroglossal area at a given pharyngeal pressure, and mandibular advancement increased the retropalatal area in nonobese but not in obese persons at a given pharyngeal pressure. CONCLUSION: Mandibular advancement did not improve the retropalatal airway in obese persons.

Adult↗
PubMed1997

Anatomy of pharynx in patients with obstructive sleep apnea and in normal subjects.

Anatomic abnormalities of the pharynx are thought to play a role in the pathogenesis of obstructive sleep apnea (OSA), but their contribution has never been conclusively proven. The present study tested this anatomic hypothesis by comparing the mechanics of the paralyzed pharynx in OSA patients and in normal subjects. According to evaluation of sleep-disordered breathing (SDB) by nocturnal oximetry, subjects were divided into three groups: normal group (n = 17), SDB-1 (n = 18), and SDB-2 (n = 22). The static pressure-area relationship of the passive pharynx was quantified under general anesthesia with complete paralysis. Age and body mass index were matched among the three groups. The site of the primary closure was the velopharynx in 49 subjects and the oropharynx in only 8 subjects. Distribution of the location of the primary closure did not differ among the groups. Closing pressure (PC) of the velopharynx for SDB-1 and SDB-2 groups (0.90 +/- 1.34 and 2.78 +/- 2.78 cmH2O, respectively) was significantly higher than that for the normal group (-3.77 +/- 3.44 cmH2O; P < 0.01). Maximal velopharyngeal area for the normal group (2.10 +/- 0.85 cm2) was significantly greater than for SDB-1 and SDB-2 groups (1.15 +/- 0.46 and 1.06 +/- 0.75 cm2, respectively). The shape of the pressure-area curve for the velopharynx differed between normal subjects and patients with SDB, being steeper in slope near Pc in patients with SDB. Multivariate analysis of mechanical parameters and oxygen desaturation index (ODI) revealed that velopharyngeal Pc was the only variable highly correlated with ODI. Velopharyngeal Pc was associated with oropharyngeal Pc, suggesting mechanical interdependence of these segments. We conclude that the passive pharynx is more narrow and collapsible in sleep-apneic patients than in matched controls and that velopharyngeal Pc is the principal correlate of the frequency of nocturnal desaturations.

Adult↗
PubMed1997

Interaction of cross-sectional area, driving pressure, and airflow of passive velopharynx.

Previous studies have shown that, when the pharyngeal muscles are relaxed, the velopharynx is a highly compliant segment of the pharynx. Thus, under these circumstances, cross-sectional area of the velopharynx (AVP), driving pressure across the velopharynx (DeltaP), and inspiratory airflow (VI) will be mutually interdependent variables. The purpose of the present investigation was to describe the interrelation among these three variables during inspiration. We studied 15 sleeping patients with obstructive sleep apnea/hypopnea when the pharyngeal muscles were rendered hypotonic by applying continuous positive airway pressure to the nasal airway. AVP, determined by endoscopic imaging, was significantly greater at onset of VI limitation than at minimum oropharyngeal pressure (P < 0. 01). Snoring was never observed during VI limitation. In a subgroup of six patients, values for DeltaP, VI, and AVP were obtained at 0. 1-s intervals at various levels of mask pressure. For these six patients, the mathematical expression VI = 0.657(AVP/Amax) . DeltaP0. 332, where Amax is maximal AVP, described the relationship among the three variables (R2 = 0.962) for flow-limited and non-flow-limited inspirations. The impedance of the passive velopharynx, defined as DeltaP0.33/V, was inversely related to AVP and increased dramatically when AVP was <0.3 cm2. In summary, we observed a progressive decrease in AVP during flow-limited inspiration in patients with obstructive sleep apnea. This constriction of the velopharynx contributes to an increase in velopharyngeal impedance that, in turn, counterbalances the increase in DeltaP during flow limitation.

Adult↗
PubMed1996

Static properties of the passive pharynx in sleep apnea.

Complete paralysis under general anesthesia allowed separating anatomic factors from neural factors which influence pharyngeal patency. We compared static mechanical properties of the passive pharynx in normals and sleep apneics. The passive pharynx was narrower and more collapsible in sleep apneics than normal controls indicating significance of anatomic factors in the pathogenesis of obstructive sleep apnea.

Electroencephalography↗
PubMed1995

Upper airway obstruction during midazolam sedation: modification by nasal CPAP.

We examined the depressant effect of midazolam on respiration in 21 healthy women undergoing lower abdominal surgery with spinal anaesthesia. Airway gas flow, airway pressure, and the sound of snoring were recorded together with arterial oxygen saturation (SpO2). After spinal anaesthesia was established, subjects were deeply sedated with pentazocine 15 mg followed by incremental doses of midazolam 1 mg i.v. up to 0.1 mg.kg-1. When SpO2 decreased to < 90% or snoring and/or apnoea was observed, continuous positive airway pressure applied through the nose (nasal CPAP) was increased until the respiratory deterioration was reversed. While one patient remained free of respiratory events, the other 20 patients were successfully treated with nasal CPAP restoring normal SpO2 (95.5 +/- 1.7%) without snoring. Stepwise reduction of nasal CPAP determined the minimally effective CPAP to prevent snoring to be 5.1 +/- 2.1 cm H2O. Further reduction of nasal CPAP induced snoring in 15 patients and obstructive apnoea in five patients with the latter accompanied by a severe reduction of SpO2 (87.4 +/- 6.1%). Patients with apnoea were older than those who snored (P < 0.05. We conclude that upper airway obstruction contributes considerably to decreases in SpO2 during midazolam sedation for spinal anaesthesia.

Abdomen↗
PubMed1995

Advancement of the mandible improves velopharyngeal airway patency.

The velopharynx is the most common site of obstruction in patients with obstructive sleep apnea (OSA). Advancement of the mandible effectively reverses the pharyngeal obstruction. Accordingly, we hypothesized that mandibular advancement increases cross-sectional area of several segments of the upper airway, including the velopharynx and the oropharynx. We examined the pressure-area properties of the pharyngeal airway in 13 patients with OSA. Under general anesthesia and total muscle paralysis, the pharynx was visualized with an endoscope connected to a video-recording system. During an experimentally induced apnea, we manipulated the nasal pressure from 20 cmH2O to the point of total closure at the velopharynx. The procedure was repeated after maximal forward displacement of the mandible. Measurements of the cross-sectional area at different levels of nasal pressure allowed construction of a static pressure-area relationship of the "passive pharynx," where active neuromuscular factors are suppressed. In 12 of 13 patients with OSA, advancement of the mandible stabilized the airway by reducing the closing pressure and increasing the area at any airway pressure. Thus the maneuver shifted the static pressure-area curve of the velopharynx and the oropharynx upward in these patients. We conclude that anterior movement of the mandible widens the retropalatal airway as well as that at the base of the tongue in the passive pharynx of OSA patients.

Adult↗
PubMed1993

Partial monosomy 5p and partial trisomy 5q due to paternal pericentric inversion of chromosome 5.

A male infant with partial monosomy 5p and partial trisomy 5q due to paternal pericentric inversion of chromosome 5 (46,XY,rec(5), dup q,inv(5)(p15.1q35.1)pat) is reported together with the oral findings. The phenotype was chiefly the cri-du-chat syndrome. Severe retardation of mental and motor development, microencephaly, cardiac malformation, crying and facial appearance unique to the cri-du-chat syndrome were observed. Perioral and intraoral findings included thin upper lip, down-turning corners of mouth, micrognathia, shallow palate, and cleft of soft palate. Anterior deciduous teeth were small and canine deciduous teeth were conic. The row of deciduous teeth showed a flat arch-like shape that was very wide but short in length. No abnormality was noted in the number of deciduous teeth or the timing of eruption.

Adult↗
PubMed1993

Diaphragmatic activity during isoflurane anaesthesia in dogs.

The effect of isoflurane administration on diaphragmatic activity was investigated in six anaesthetized mechanically ventilated dogs. Diaphragmatic strength was assessed by measuring the transdiaphragmatic pressure (Pdi) generated during supramaximal stimulation of both cervical phrenic nerves at frequencies of 0.5, 10, 20, 50 and 100 Hz under partially isometric conditions at 1, 1.5 and 2 minimum alveolar anaesthetic concentrations (MAC), after maintaining 1 h of stable conditions. Pdi measurements were made at the start of the stimulation (initial) and at the end of a 2-s period (2-s). The force-frequency relationship was compared at each anaesthetic level. For single twitch (0.5 Hz) stimulation, the time constant of diaphragmatic relaxation was also assessed. The sequence of changing anaesthetic depth was altered in random fashion between animals. Pdi amplitude at single twitch stimulation was unchanged at the three anaesthetic concentrations. There was no significant difference in initial Pdi at various stimulus frequencies with increasing depth of isoflurane anaesthesia. In addition, no change in 2-s Pdi during low frequency stimulation (10 and 20 Hz) was noted during any of the three levels of anaesthesia. By contrast, 2-s Pdi with 50 Hz stimulation during 2 MAC isoflurane exposure decreased significantly below Pdi levels seen at 1 and 1.5 MAC (P < 0.01). Furthermore, 2-s Pdi at 100 Hz stimulation decreased significantly in a dose-dependent fashion. From these results, we conclude that isoflurane reduces diaphragmatic activity at higher stimulation frequencies of 50 and 100 Hz.

Anesthesia, Inhalation↗
PubMed1993

Static mechanics of the velopharynx of patients with obstructive sleep apnea.

The static mechanics of the hypotonic pharynx were endoscopically evaluated in nine sleeping patients with obstructive sleep apnea, having a primary narrowing only at the velopharynx. The velopharynx closed completely at a mean pressure of 0.18 +/- 1.21 cmH2O, and the mean half-dilation pressure was 1.93 cmH2O above closing pressure. The dependence of area on pressure was distinctly curvilinear, being steep near closing pressure and asymptotically approaching maximum area (mean = 1.32 cm2). The data for each patient were satisfactorily fitted by an exponential function (mean R2 = 0.98), and a single exponential relationship usefully represented the dependence of relative area on pressure above closing pressure for the population (R2 = 0.85). During the test inspiration, flow limitation was consistently observed when mask pressure exceeded closing pressure by 0.5-3.0 cmH2O. In summary, the static mechanics of the hypotonic velopharynx of patients with obstructive sleep apnea can be described by an exponential pressure-area relationship, with a closing pressure near atmospheric pressure and a high compliance in the range of airway pressure 0-3 cmH2O above closing pressure.

Adult↗