Search PubMed⌕ Search

Biomedical subjects

A Oliven

Publications and source records attributed to A Oliven.

At least 91 records · Page 5Linked to original sources
PubMed1989

Reflex effect of esophageal distension on respiratory muscle activity and pressure.

The electrical activity of the respiratory skeletal muscles is altered in response to reflexes originating in the gastrointestinal tract. The present study evaluated the reflex effects of esophageal distension (ED) on the distribution of motor activity to both inspiratory and expiratory muscles of the rib cage and abdomen and the resultant changes in thoracic and abdominal pressure during breathing. Studies were performed in 21 anesthetized spontaneously breathing dogs. ED was produced by inflating a balloon in the distal esophagus. ED decreased the activity of the costal and crural diaphragm and external intercostals and abolished all preexisting electrical activity in the expiratory muscles of the abdominal wall. On the other hand, ED increased the activity of the parasternal intercostals and expiratory muscles located in the rib cage (i.e., triangularis sterni and internal intercostal). All effects of ED were graded, with increasing distension exerting greater effects, and were eliminated by vagotomy. The effect of increases in chemical drive and lung inflation reflex activity on the response to ED was examined by performing ED while animals breathed either 6.5% CO2 or against graded levels of positive end-expiratory pressure (PEEP), respectively. Changes in respiratory muscle electrical activity induced by ED were similar (during 6.5% CO2 and PEEP) to those observed under control conditions. We conclude that activation of mechanoreceptors in the esophagus reflexly alters the distribution of motor activity to the respiratory muscles, inhibiting the muscles surrounding the abdominal cavity and augmenting the parasternals and expiratory muscles of the chest wall.

Animals↗
PubMed1989

Effect of hypercapnia and PEEP on expiratory muscle EMG and shortening.

The present study examined the effects of hypercapnia and positive end-expiratory pressure (PEEP) on the electromyographic (EMG) activity and tidal length changes of the expiratory muscles in 12 anesthetized, spontaneously breathing dogs. The integrated EMG activity of both abdominal (external oblique, internal oblique, rectus abdominis, and transverse abdominis) and thoracic (triangularis sterni, internal intercostal) expiratory muscles increased linearly with increasing PCO2 and PEEP. However, with both hypercapnia and PEEP, the percent increase in abdominal muscle electrical activity exceeded that of thoracic expiratory muscle activity. Both hypercapnia and PEEP increased the tidal shortening of the external oblique and rectus abdominis muscles. Changes in tidal length correlated closely with simultaneous increases in muscle electrical activity. However, during both hypercapnia and PEEP, length changes of the external oblique were significantly greater than those of the rectus abdominis. We conclude that both progressive hypercapnia and PEEP increase the electrical activity of all expiratory muscles and augment their tidal shortening but produce quantitatively different responses in the several expiratory muscles.

Animals↗
PubMed1989

Effect of salicylate on upper airway dilating muscles in anesthetized dogs.

It is well documented that salicylate given in large doses stimulates ventilation. As increased ventilatory drive is often associated with augmented upper airway dilating muscle activity, we evaluated in anesthetized dogs the effect of salicylate on the electrical activity of three upper airway muscles, the alae nasi, the genioglossus, and the posterior cricoarytenoid. The electromyograms of these muscles were compared with those of the diaphragm before and at 15-min intervals after intravenous salicylate administration (250 mg/kg). Salicylate induced a gradual increase in ventilation and in the electrical activity of all muscles examined (p less than 0.001). Compared to baseline activity, salicylate increased the electrical activity of the genioglossus more than that of the diaphragm (p less than 0.01). The increase in upper airway muscle activity was observed also in vagotomized dogs, and was not accounted for by changes in arterial blood gases or pH. Increases in upper airway muscle electrical activity were associated with a significant decrease in upper airway resistance to airflow (mean reduction of 62 +/- 7% SE, p less than 0.01). The preferential increase in genioglossus electrical activity and the decrease in upper airway resistance observed in this study with salicylate suggest that salicylate, and possibly other pharmacologic agents that stimulate ventilation, may improve upper airway patency.

Airway Resistance↗
PubMed1989

Functional enteroinsular axis in full-term newborn infants.

The term "enteroinsular axis" refers to the enhancement of insulin release by hormones secreted from the gut. Gastric inhibitory polypeptide (GIP) is one of the major hormones that mediates this function. The purpose of the present study was to examine whether the enteroinsular axis is functional in newborn infants born at term gestation. Between d 2 and d 4 of life, glucose was infused for 2 h intravenously or orogastrically to 44 fullterm newborn infants, of whom 18 were appropriate for gestational age, nine large for gestational age, eight small for gestational age; nine infants were born to diabetic mothers. Glucose was infused at either 8 mg/kg/min intravenously or 16 mg/kg/min orogastrically to achieve similar plasma glucose concentrations. Plasma insulin and GIP concentrations were compared. Plasma GIP concentration increased significantly with enteral glucose administration in all infants but remained unchanged with parenteral glucose infusion. The responses of plasma insulin and the insulin/glucose ratio were significantly greater in infants receiving enterally than parenterally infused glucose. However, when glucose was infused orogastrically at a lower rate (8 mg/kg/min), plasma GIP concentrations rose, but no enhancement of insulin response was detected, suggesting the importance of the role of circulating glucose in the "enteroinsular axis". The infants of diabetic mothers and the large-for-gestational-age infants had more rapid insulin response to orogastrically administered glucose, but their GIP responses were similar to that of normal infants. These findings suggest that, at term gestation, the newborn infants have a "functional" enteroinsular axis in response to glucose, i.e. the rising plasma GIP contributed in part to the enhanced insulin response to enterally infused glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Enteral Nutrition↗
PubMed1989

Effect of salicylate on upper airway stability and pressure flow: relationship in anesthetized dogs.

Previous studies have shown that upper airway muscle activity is augmented in response to increased respiratory drive, thereby improving upper airway patency. In the present study we evaluated the effect of salicylate, a well-known respiratory stimulant, on upper airway stability and pressure-flow relationship. Multiple levels of airflow were used to assess pressure-flow relationship in the isolated airways of anesthetized dogs and to calculate the coefficients of Rohrer's equation P = K1V + K2V2. In addition, we measured the negative intraluminal pressure needed to collapse the upper airway. These measurements were repeated after intravenous administration of sodium salicylate, 250 mg/kg. Salicylate-induced hyperventilation was associated with increased alae nasi electrical activity. Resistance to airflow and K2 decreased significantly (p less than 0.01), suggesting dilation of the upper airway lumen. The intraluminal pressure under which upper airway collapse occurred became more negative in all dogs (from -5.0 +/- 0.8 to -8.5 +/- 1.3 cm H2O, p less than 0.01), indicating improved stability of the upper airway walls. These findings suggest that salicylate, and presumably other pharmacologic agents that stimulate ventilation, can improve both upper airway patency and upper airway stability.

Airway Resistance↗
PubMed1988

Effect of fatiguing resistive loads on the level and pattern of respiratory activity in awake goats.

The effect of respiratory muscle fatigue on inspiratory muscle electrical activity (EMG), transdiaphragmatic pressure and ventilation during spontaneous breathing was examined in three awake goats. Studies were performed during progressive hypercapnia before and immediately after inspiratory muscle fatigue induced by flow resistive loading (IRL). IRL caused a decrease in the high-low ratio of the diaphragm and intercostal EMG and a decrease in Pdi during electrophrenic stimulation. After IRL, inspiratory time, the breathing duty cycle (inspiratory time/total breath cycle time), peak integrated activity of the diaphragm and external intercostal EMG per breath and per minute were all decreased at any given level of PCO2. Changes in the timing of respiratory motor activity and reduced muscle performance after IRL resulted in a decrease in transdiaphragmatic pressure and ventilation during hypercapnia. In conscious goats studied during spontaneous, chemically stimulated breathing, inspiratory muscle fatigue is associated with reductions in diaphragm and external intercostal muscle electrical activity and reductions in transdiaphragmatic pressure and ventilation.

Animals↗
PubMed1988

Successful resolution of unilateral pulmonary interstitial emphysema in a premature infant by selective bronchial balloon catheterization.

Pulmonary interstitial emphysema (PIE) is a common complication in premature infants with respiratory distress syndrome. The development of pulmonary interstitial emphysema leads to marked respiratory embarrassment in an already compromised infant. Although usually bilateral, PIE may be unilateral. Various forms of treatment for unilateral PIE in the premature infant have been described, including selective bronchial intubation, unilateral pneumonectomy, visceral pleurotomy, pure oxygen administration, and high-frequency low-pressure ventilation. A recently reported conservative regimen consisting of downward lateral positioning of the affected lung for several days may not be successful. We describe a premature infant with progressive worsening of unilateral PIE, which was successfully treated by selective bronchial balloon catheterization after failure of conservative management. In this manner, we avoided selective bronchial intubation or other aggressive forms of treatment.

Bronchi↗
PubMed1988

Corticosteroids in the management of sinoatrial block.

This report presented our experience in the treatment of sinoatrial (S-A) conduction disturbances with corticosteroids. Three patients with intermittent second-degree S-A block who failed to respond to atropine and isoproterenol were treated with prednisone for 6-17 weeks. Sustained improvement in S-A conduction following prednisone administration was confirmed by repeated Holter monitoring on and off therapy. Two patients eventually regained permanent sinus rhythm, while therapy led to marked diminution in S-A block in the 3rd patient. The possible mechanisms by which steroids may improve S-A conduction are discussed. Our observation is based on a small case series, each patient serving as his own control, and as such constitutes an indication for further confirmatory studies.

Atropine↗
PubMed1987

Effects of bronchoconstriction on respiratory muscle activity during expiration.

The effect of methacholine-induced bronchoconstriction on the electrical activity of respiratory muscles during expiration was studied in 12 anesthetized spontaneously breathing dogs. Before and after aerosols of methacholine, diaphragm, parasternal intercostal, internal intercostal, and external oblique electromyograms were recorded during 100% O2 breathing and CO2 rebreathing. While breathing 100% O2, five dogs showed prolonged electrical activity of the diaphragm and parasternal intercostals in early expiration, postinspiratory inspiratory activity (PIIA). Aerosols of methacholine increased pulmonary resistance, decreased tidal volume, and elevated arterial PCO2. During bronchoconstriction, when PCO2 was varied by CO2 rebreathing, PIIA was shorter at low levels of PCO2, and external oblique and internal intercostal were higher at all levels of PCO2. Vagotomy shortened PIIA in dogs with prolonged PIIA. After vagotomy, methacholine had no effects on PIIA but continued to increase external oblique and internal intercostal activity at all levels of PCO2. These findings indicate that bronchoconstriction influences PIIA through a vagal reflex but augments expiratory activity, at least in part, by extravagal mechanisms.

Animals↗
PubMed1986

Functional adaptation of diaphragm to chronic hyperinflation in emphysematous hamsters.

Costal strips of diaphragmatic muscle obtained from animals with elastase-induced emphysema generate maximum tension at significantly shorter muscle fiber lengths than muscle strips from control animals. The present study examined the consequences of alterations in the length-tension relationship assessed in vitro on the pressure generated by the diaphragm in vivo. Transdiaphragmatic pressure (Pdi) and functional residual capacity (FRC) were measured in 22 emphysematous and 22 control hamsters 4-5 mo after intratracheal injection of pancreatic elastase or saline, respectively. In 12 emphysematous and 12 control hamsters Pdi was also measured during spontaneous contractions against an occluded airway. To allow greater control over muscle excitation, Pdi was measured during bilateral tetanic (50 Hz) electrical stimulation of the phrenic nerves in 10 emphysematous and 10 control hamsters. Mean FRC in the emphysematous hamsters was 183% of the value in control hamsters (P less than 0.01). During spontaneous inspiratory efforts against a closed airway the highest Pdi generated at FRC tended to be greater in control than emphysematous hamsters. When control hamsters were inflated to a lung volume approximating the FRC of emphysematous animals, however, peak Pdi was significantly greater in emphysematous animals (70 +/- 6 and 41 +/- 8 cmH2O; P less than 0.05). With electrophrenic stimulation, the Pdi-lung volume curve was shifted toward higher lung volumes in emphysematous hamsters. Pdi at all absolute lung volumes at and above the FRC of emphysematous hamsters was significantly greater in emphysematous compared with control animals. Moreover, Pdi continued to be generated by emphysematous hamsters at levels of lung volume where Pdi of control subjects was zero.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1986

Effects of rifampin and isoniazid on the isolated perfused rat liver.

The effect of the antitubercular drugs rifampin and isoniazid on the function of the isolated, perfused rat liver was evaluated by monitoring the rate of bile flow and sulfobromophthalein (BSP) clearance. The effect of rifampin on bile flow was biphasic: rifampin concentration of 100 micrograms/ml increased the flow to 134% of baseline, while 1,000 micrograms/ml decreased the flow to 58% of baseline (p less than 0.01 for both). Rifampin also caused a dose-dependent inhibition of BSP removal from the perfusate and excretion in the bile. Isoniazid had no adverse effect on bile flow and BSP clearance, and the combination of isoniazid and rifampin had the same effects on the perfused liver as rifampin alone.

Animals↗
PubMed1986

Role of glucose in the regulation of endogenous glucose production in the human newborn.

The role of plasma glucose concentration in the regulation of endogenous glucose production in the human newborn was examined by infusing glucose at 2.6-4.6 mg/kg . min as a continuous infusion to eight normal term appropriate for gestational age infants, five preterm, and six small for gestational age infants. All infants were healthy, had no overt clinical problems and were studied 6 h after their last feed. Glucose production rates were measured during the basal state and during glucose infusion by tracer dilution using [6,6(2)H2]glucose. The rate of glucose production during the basal state was similar in preterm and term appropriate for gestational age infants (appropriate for gestational age 3.53 +/- 0.32, preterm 3.49 +/- 0.38 mg/kg . min, mean +/- SD), while it was higher in the small for gestational age infants (4.25 +/- 0.98, p less than 0.03) as compared with appropriate for gestational age. During glucose infusion, the peak glucose concentration was related to the rate of glucose infusion. The endogenous glucose production rates during glucose infusion were variable in the three groups. However, a negative correlation between peak glucose concentration and endogenous glucose production rate was observed (r = 0.59, p = 0.006). The insulin response to glucose infusion was comparable in all infants. In addition, three small gestational age and one preterm infants, who had become hypoglycemic in the immediate newborn period, were studied while they were receiving parenteral glucose and their plasma glucose had stabilized at 55.5 +/- 10.25 mg/dl. Tracer kinetic studies showed persistence of endogenous glucose production in these infants even though they were receiving high rates of exogenous glucose infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
PubMed1985

Effects of hypercapnia on inspiratory and expiratory muscle activity during expiration.

Persistence of inspiratory muscle activity during the early phase of expiratory airflow slows the rate of lung deflation, whereas heightened expiratory muscle activity produces the opposite effect. To examine the influence of increased chemoreceptor drive and the role of vagal afferent activity on these processes, the effects of progressive hypercapnia were evaluated in 12 anesthetized tracheotomized dogs before and after vagotomy. Postinspiratory activity of inspiratory muscles (PIIA) and the activity of expiratory muscles were studied. During resting breathing, the duration of PIIA correlated with the duration of inspiration but not with expiration. Parasternal intercostal PIIA was directly related to that of the diaphragm. Based on their PIIA, dogs could be divided into two groups: one with prolonged PIIA (mean 0.57 s) and the other with brief PIIA (mean 0.16 s). Hypercapnia caused progressive shortening of the PIIA in the dogs with prolonged PIIA during resting breathing. The electrical activity of the external oblique and internal intercostal muscles increased gradually during CO2 rebreathing in all dogs both pre- and postvagotomy. After vagotomy, abdominal activity continued to increase with hypercapnia but was less at all levels of PCO2. The internal intercostal response to hypercapnia was not affected by vagotomy. The combination of shorter PIIA and augmented expiratory activity with hypercapnia might, in addition to changes in lung recoil pressure and airway resistance, hasten exhalation.

Abdominal Muscles↗
PubMed1985

The effects of acute bronchoconstriction on respiratory activity in patients with chronic obstructive pulmonary disease.

Attacks of acute airway obstruction often complicate the course of chronic obstructive pulmonary disease (COPD). In asthmatic subjects, bronchospasm triggers an increase in respiratory drive, which results in hyperventilation and hypocapnia. In the present study, we assessed the effects of acute bronchoconstriction induced by aerosolized methacholine on breathing and lung mechanics in 12 patients with stable COPD. Even low doses of methacholine markedly increased airway resistance and caused hyperinflation and decreased inspiratory muscle performance in the patients. Increasing airway obstruction produced a progressive rise in PCO2 despite an increase in minute ventilation. Breathing frequency and average inspiratory flow were greater, but tidal volume decreased because of shortening of the inspiratory duration. The magnitude of CO2 retention during acute bronchoconstriction was inversely related to the changes in tidal volume and inspiratory time (p less than 0.01 for each). In subjects with COPD, the occlusion pressure response to progressive hypercapnia failed to increase during bronchoconstriction. These results show that patients with COPD retain CO2 during acutely increasing airway obstruction induced by bronchoconstriction partly because of a rapid shallow breathing pattern that reduces alveolar ventilation.

Aged↗
PubMed1985

Respiratory pressure sensation. Relationship to changes in breathing pattern and PCO2 during acute increase in airway resistance in patients with chronic obstructive pulmonary disease.

The intensity of sensations experienced during breathing by patients with chronic obstructive pulmonary disease (COPD) might influence their ventilatory response to altered lung mechanics. In 8 patients with COPD (mean FEV1, 1.6 +/- 0.6 L SD) the acuity with which changes in intrathoracic pressure were perceived was studied by a standard psychophysical technique, magnitude production of inspiratory pressure. Subjects voluntarily produced mouth pressures proportional to numbers randomly presented, and the sensory acuity to changes in pressure was assessed from the slope of log-log plots of numbers versus pressures. These slopes were then related to the ventilatory responses of the patients to external resistive loads of 10 cm H2O/L/s, applied during both inspiration and expiration, and methacholine-induced bronchoconstriction, which doubled baseline specific airway resistance. Both modes of increase in airway resistance caused an increase in end-tidal PCO2 in all patients (range, 0.5 to 11 mmHg). The magnitude of CO2 retention correlated significantly with the change in tidal volume during both external loading and bronchoconstriction (r = -0.77, p less than 0.01); decreases in tidal volume were associated with increases in PCO2. The slope for magnitude production of pressure was inversely related to changes in tidal volume during both modes of increases in airway resistance (r = 0.61, p less than 0.01 for both bronchoconstriction and external resistive loads). Patients with the highest exponents for pressure changes (highest slopes) demonstrated the greatest decreases in tidal volume. Consequently, a direct relationship was found between the magnitude of the exponent and the magnitude of CO2 retention during loaded breathing and bronchoconstriction (r = 0.81, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1984

Massive thrombosis as a result of triple infestation of the pulmonary arterial circulation by Ascaris, Candida, and Mucor.

A 35-year-old man with a brief history of dyspnea and fever experienced rapid progressive respiratory distress and died shortly after being hospitalized. Postmortem examination revealed thrombotic occlusion of the pulmonary tree; the thrombotic material showed Ascaris lumbricoides, Candida albicans, and Mucor. This rare coincidence is an unexpected complication of ascariasis that has not been described previously.

Adult↗
PubMed1984

Respiratory response to partial paralysis in anesthetized dogs.

The ability to maintain alveolar ventilation is compromised by respiratory muscle weakness. To examine the independent role of reflexly mediated neural mechanisms to decreases in the strength of contraction of respiratory muscles, we studied the effects of partial paralysis on the level and pattern of phrenic motor activity in 22 anesthetized spontaneously breathing dogs. Graded weakness induced with succinylcholine decreased tidal volume and prolonged both inspiratory and expiratory time causing hypoventilation and hypercapnia. Phrenic peak activity as well as the rate of rise of the integrated phrenic neurogram increased. However, when studied under isocapnic conditions, increases in the severity of paralysis, as assessed from the ratio of peak diaphragm electromyogram to peak phrenic activity, produced progressive increases in inspiratory time and phrenic peak activity but did not affect its rate of rise. After vagotomy, partial paralysis induced in 11 dogs with succinylcholine also prolonged the inspiratory burst of phrenic activity, indicating that vagal reflexes were not solely responsible for the alterations in respiratory timing. Muscle paresis was also induced with gallamine or dantrolene, causing similar responses of phrenic activity and respiratory timing. Thus, at constant levels of arterial CO2 in anesthetized dogs, respiratory muscle partial paralysis results in a decrease in breathing rate without changing the rate of rise of respiratory motor activity. This is not dependent solely on vagally mediated reflexes and occurs regardless of the pharmacological agent used. These observations in the anesthetized state are qualitatively different from the response to respiratory muscle paralysis or weakness observed in awake subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗