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Biomedical subjects

H T Folgering

Publications and source records attributed to H T Folgering.

At least 109 records · Page 6Linked to original sources
PubMed1986

[Obstructive sleep apnea syndrome in children; an indication for tonsillectomy and adenoidectomy].

A 3-year-old girl with obstructive sleep apnea syndrome associated with tonsillar and adenoid hypertrophy is discussed. Nocturnal sleep registration, 4 months after adeno-tonsillectomy revealed complete arrest of apnea episodes and there was improvement in sleep pattern. In the early detection of obstructive sleep apnea in children a careful history and nocturnal sleep registration are essential. In children, tonsillar and adenoid hypertrophy are the main causes of obstructive sleep apnea.

Adenoidectomy↗
PubMed1985

Ventilatory effects of atenolol and bevantolol in asthma.

The cardioequipotency of 400 mg bevantolol and 100 mg atenolol was determined by measuring the exercise heart rate in healthy subjects. The beta-blockers were then used in these doses to investigate their ventilatory effects in patients with asthma. The effects of both drugs on forced expiratory flow parameters for large and small airways were assessed at rest and during and after exercise. A dose-response curve was then plotted after inhalation of the beta 2-adrenoceptor agonist terbutaline. Bevantolol significantly decreased the forced expiratory volume in 1 second (FEV1) and the peak expiratory flow rate (PEFR) at rest, while there was no such change with placebo or atenolol. Both beta-blockers decreased the maximal expiratory flow rates at 50% of forced vital capacity (MEF50) and after expiration of 75% of the forced vital capacity (MEF25) at rest; the decrease was larger after bevantolol than after atenolol. During atenolol there was a decrease in FEV1 and in PEFR (P less than 0.01) 15 minutes after exercise in comparison with preexercise values. There was no significant difference between pre- and postexercise values of MEF50 and MEF25 during atenolol dosing. After bevantolol there was only a small change in PEFR after exercise, probably because of the low preexercise values of the ventilatory indices with this drug. Inhalation of terbutaline up to a dose of 2 mg significantly improved all ventilatory indices measured, but with bevantolol the values after 2 mg inhaled terbutaline were lower than the initial values.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1985

Ventilatory effects of long-term treatment with pindolol and metoprolol in hypertensive patients with chronic obstructive lung disease.

Effects of long-term treatment with pindolol (10 mg twice daily) and metoprolol (100 mg twice daily) on lung function and blood pressure were investigated in eight patients with chronic obstructive lung disease and hypertension. After a placebo period, both beta-adrenoceptor blockers were administered double-blind and cross-over for 4 weeks. By assessing parameters of expiratory flow an attempt was made to distinguish between large and small airways function. Diastolic blood pressure decreased significantly during both pindolol and metoprolol (P less than 0.01). Except for a decrease in forced expiratory volume in 1 s (FEV1) during metoprolol treatment, there was no other change in expiratory flow parameters after placebo or both beta-adrenoceptor blockers. Inhalation of terbutaline induced a small improvement in large airways function after placebo and metoprolol, but not after pindolol; there was no effect of terbutaline on parameters of small airways function. If a beta-adrenoceptor blocker is necessary in patients with chronic obstructive lung disease, a beta 1-adrenoceptor selective blocker is preferred in combination with bronchodilator agents.

Adult↗
PubMed1984

Ventilatory effects of beta 1-receptor-selective blockade with bisoprolol and metoprolol in asthmatic patients.

In a double blind, placebo-controlled study the ventilatory effects of the beta 1-selective receptor blockers bisoprolol (EMD 33512) and metoprolol and their interactions with the beta 2-adrenoceptor agonist terbutaline were investigated in 8 asthmatic patients. Both beta-blockers, in all the doses given, caused a significant decrease in peak expiratory flow rate (PEFR). Vital capacity (VC) and forced expiratory volume in one second (FEV1) were significantly decreased only after 10 mg bisoprolol. Terbutaline inhalation caused the same significant improvements in FEV1 and PEFR during placebo as during bisoprolol 10 mg, bisoprolol 20 mg and metoprolol 100 mg. Both beta-blockers caused equal changes in heart rate (HR) at rest. Systolic and diastolic blood pressure (BP) decreased significantly after bisoprolol 20 mg and metoprolol 100 mg, but not after bisoprolol 10 mg. Inhalation of terbutaline up to a dose of 3.5 mg had no influence on HR and BP. The results point to good beta 1-selectivity of bisoprolol 10 mg and 20 mg and metoprolol 100 mg in asthmatic patients. No correlation was found between the plasma levels of the beta-blockers and the changes in the ventilatory indices, HR or BP.

Adrenergic beta-Antagonists↗
PubMed1983

Effects of respiratory and (isocapnic) metabolic arterial acid-base disturbances on medullary extracellular fluid pH and ventilation in cats.

Ventilation is influenced by the brain extracellular fluid (ecf) pH which is sensed by the central chemoreceptors. In the present experiments we have investigated to what extent ventilatory effects of brain ecf pH changes depend on the origin of these pH changes. With this aim we have compared the effects of 'respiratory' (via changes in PaCO2) and 'metabolic' (via isocapnic pHa changes) ecf pH changes on steady state ventilatory activity. Experiments were performed in anaesthetized (both artificially ventilated and spontaneously breathing) cats with cut sinus nerves; medullary surface ecf pH was measured with a glass electrode with a flat pH-sensitive surface. We found that ecf pH changes caused by changes in PaCO2 give rise to greater ventilatory responses than the same ecf pH changes caused by (isocapnic) changes in pHa. Moreover, within the pH ranges measured, isocapnic pHecf-ventilatory response lines at higher PaCO2 are shifted upwards compared with those at lower PaCO2 levels. It was concluded that with the present technique it is impossible to show a unique relation between ecf pH and ventilation.

Acid-Base Imbalance↗
PubMed1982

Metabolic aspects of maximal exercise performance after slow release metoprolol and after atenolol.

Maximal exercise performance by eight healthy male subjects was tested after one week of medication with slow-release metoprolol 200 mg/d (metoprolol-SR), atenolol 200 mg/d or placebo, in a double blind crossover trial. The maximal working capacity was significantly decreased after atenolol and metoprolol-SR. Plasma glucose and FFA concentrations during the exercise test did not change: either after placebo therapy or after beta-blockade. The anerobic threshold did not change after beta-blockade, but the changes in lactate due to the exercise were less after beta-blockade. Neither beta-blocker affected the exercise-induced alteration in airway resistance. Both drugs caused a small but significant ventilatory depression at rest and at 75% of maximal exercise. It is concluded that the limiting factor in maximal exercise performance after beta 1-adrenergic blockade does not lie in oxygen transport to the working muscles via ventilation and the circulation, but is most probably due to anaerobic metabolism.

Adult↗
PubMed1982

Dynamics of brain extracellular fluid pH and phrenic nerve activity in cats after end-tidal CO2 forcing.

Ventilation is influenced by the interstitial [H+] of the brain. The pHecf, which in turn is determined largely by ventilation (via PaCO2) is sensed by the central chemoreceptors. In order to investigate the dynamics of both pHecf and neural tidal volume, we measured in cats with cut vagi and sinus nerves the dynamic medullary pHecf changes and the associated changes in integrated phrenic nerve activity after end-tidal CO2 forcing. The medullary surface ecf pH was measured with a glass electrode with a flat pH-sensitive surface. After CO2 up-steps, the pHecf changed with a time constant of about 43 sec, after down-steps 30 sec was found. The central time constant of the neural tidal volume response was 50 sec (mode) in both cases, whereas the overall response had a (modal) time constant of 80 sec. The results indicate that pHecf dynamics and the dynamic characteristics of the central neural respiratory organization are about equally important in determining the dynamic neural tidal volume response. It is argued that when PaCO2 changes, the dynamic pHecf change is perfusion limited and macroscopically homogeneous within the brainstem. Therefore, in our view it seems that the location of the central chemoreceptors within the brainstem is of minor importance in determining the dynamic neural tidal volume response to PaCO2 changes.

Animals↗
PubMed1981

Effects of positive and negative exercise on ventilatory CO2 sensitivity.

Investigations in our laboratory have shown an increased slope of the ventilatory response curve to CO2 (CO2 sensitivity) during positive and negative exercise as compared with the resting condition. CO2 sensitivity during positive and negative exercise did not differ in spite of differences in metabolism (VO2, VCO2) and type of muscle contraction (concentric or eccentric). Various aspects of positive and negative exercise were examined in order to find out whether they can explain the identical CO2 sensitivity. Cardiac output, oxygen consumption, rectal temperature and venous catecholamine concentration appeared to be higher in positive exercise than in negative exercise, and higher in negative exercise than at rest. However, these differences between the two types of exercise contrast with the identical CO2 sensitivity and thus cannot be of major importance in determining CO2 sensitivity. It is hypothesized that one or more of these variables might be responsible for increased CO2 sensitivity during exercise as compared with rest. The CO2 sensitivity, once increased, seems to be unaffected by further increases in these variables.

Carbon Dioxide↗
PubMed1981

Phrenic nerve afterdischarge after electrical stimulation of the carotid sinus nerve in cats.

The phrenic nerve afterdischarge in cats after electrical stimulation of the carotid sinus nerve (CSN) at different levels of PETCO2, PETO2 and anaesthesia, both with vagi intact and cut, is fitted to a mono-exponential decay. It is concluded that the time constant of this decay is not influenced by blood gas values, anaesthesia and vagotomy. However, the magnitude of the afterdischarge tends to zero at higher levels of phrenic nerve activity, so the phenomenon disappears. The results are explained by restricted central phasic sensitivity and the consequences for respiration control are discussed.

Action Potentials↗
PubMed1979

Description of the firing pattern of respiratory neurons by frequency modulated interspike interval distributions.

The description of the firing pattern of respiratory neurons presented here is based on extracellular recordings and directed to the possible influence (facilitating of inhibiting effect) that the neuron might have upon others (output) as well as to the extend of influences that are received from other neurons (input). Developing such a description the spike generating mechanism of the neuron was in a first approach characterized by a frequency modulated gamma distribution. Using this approach an acceptable match between calculated and measured interspike-interval distribution was found although mostly not statistically significant. This non-significancy is most probably due to the choice of the simple gamma distribution as a first approach. However, applying this description it seems possible to retrieve statistical information about the interaction between neurons from extracellular recordings. Based on this description it is proposed to use modal spike frequency as well as the variance of the interspike interval distribution as estimates for the activity and the extent of activation of the neuron.

Action Potentials↗
PubMed1978

Three successive steady-state CO2-response curves. No change of sensitivity of the ventilatory controlling system for CO2.

Three successive steady-state CO2-response curves, with 10-minute intervals, were taken in seven healthy subjects at rest in normoxia. No systematic difference in the slopes between the three curves could be found. The results suggest that a previous steady-state CO2-response curve does not change the sensitivity of the ventilatory controlling system for CO2.

Adult↗
PubMed1977

Capnostat and oxystat. Electronic devices to automatically maintain the end-tidal PCO2 and PO2 of a subject connected to a closed respiratory circuit at adjustable levels.

In respiratory physiology it is often desirable to maintain the end-tidal PCO2 and PO2 at adjustable levels independent of each other, e.g., when taking steady-state CO2 or O2 response curves, or when studying the ventilatory effects of exercise or drugs at constant levels of PCO2 and PO2. Based on the closed respiratory circuit described by Folgering et al. (1974), a new version was designed. The main new features of this version are that end-tidal PO2 instead of inspiratory PO2 can be kept constant, and that the correcting activity of both controllers (capnostat and oxystat) is proportional to the magnitude of the difference between the actual and the adjusted end-tidal PCO2 or PO2. An optic as well as an acoustic alarm is provided and will be switched on whenever no end-tidal PO2 is detected for an adjustable time.

Carbon Dioxide↗
PubMed1976

The role of the fusimotor system with respect to the contribution of the diaphragm and the intercostal muscles to the respiratory tidal volume.

The efferent electrical activity in the phrenic nerve can be quantified in such a way that it gives a good correlation to tidal volume. After administration of the drug benzoctamine this relationship changes: more phrenic nerve activity is needed for the same tidal volume. No changes were found in the neuro-muscular transmission from the phrenic nerve to the diaphragm. There was no alteration in dynamic compliance of the lungs or in airway resistance. The afferent phrenic nerve activity from proprioceptors in the diaphragm did not change. It seems unlikely that respiratory neurons in the brainstem were affected since the sensitivity of the respiratory system to CO2 did not change. It is known that the tonic fusimotoneuron activity is suppressed at a supraspinal level by benzoctamine. Since intercostal muscles have muscle spindles and the diaphragm hardly has any, the intercostal muscle activity will be affected more than diaphragmatic activity by benzoctamine. This could actually be shown by quantifying the electromyogram of inspiratory external intercostal muscles. The tidal volume regulation is controlled by the vagal feedback loop. In order to reach a certain tidal volume after administration of benzoctamine, the contribution of the diaphragm has to increase because the activity of the intercostal muscles is diminished.

Animals↗
PubMed1976

Ventilatory response to CO2 at rest and during positive and negative work in normoxia and hyperoxia.

Ventilation versus alveolar PCO2 relationships were determined by the steady-state method in 6 normal male subjects at rest and during positive and negative work at one load in both normoxic and hyperoxic condition. In 5 subjects the slopes of the VE-PACO2 lines during positive and negative work increased in normoxia as compared with rest. This effect was less evident in hyperoxia. It was also found that the slopes of the VE-PACO2 lines in positive and in negative work were about the same in both normoxic and hyperoxic conditions. Oxygen uptake and CO2 production during positive work is higher than during negative work. These results suggest that: 1) the disagreement between various authors on the change of the slope of the VE-PACO2 line may be due to the differences in the method of calculation of the slope or the method of the determination of VE-PACO2 lines; 2) the stimuli from the muscle spindles in the working muscle during exercise probably do not contribute to the increase in ventilatory response to CO2; 3) the increased slope of the normoxic VE-PACO2 line during exercise may be due to the interaction of several factors such as impulses from working muscles, chemosensitivity of central or peripheral chemoreceptors, adrenal-sympathetic pathways or temperature; 4) respiratory oscilations of PAO2 or PACO2 do not seem to influence the respiratory response to CO2.

Adult↗
PubMed1975

Ventilation estimated from efferent phrenic nerve activity in the paralysed cat.

The purpose of this study is to develop a reliable method for obtaining information about "spontaneous respiration" in paralysed cats. Therefore action potentials from one of the phrenic nerves are recorded. In a spontaneously breathing animal, a CO2 rebreathing experiment is performed in order to obtain a relationship between phrenic nerve activity and tidal volume. This phrenic nerve activity is corrected for the noise measured during expiration and quantified proportional to the square root of the mean impulse rate of the whole nerve bundle. Thus, high correlation coefficients (0.95 or more) between phrenic nerve activity and tidal volume can be obtained. After paralysing the cat this relationship can be used to estimate "spontaneous tidal volume" from the phrenic nerve activity. It appears to be necessary to perform unilateral phrenicotomy on the nerve from which recordings are taken, because there is a condiserable amount of afferent signals in the phrenic nerve which is dependent on the stroke volume of the respirator, on the alveolar PCO2 and somewhat on the alveolar PO2. It is concluded that after vagotomy and phrenicotomy and if suitably quantified, the electrical activity in the phrenic nerve gives accurate information on "spontaneous ventilation" in a paralysed cat.

Action Potentials↗