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Biomedical subjects

A B Froese

Publications and source records attributed to A B Froese.

47 records · Page 3Linked to original sources
PubMed1979

Cerebellar stimulation in the management of cerebral palsy: clinical and physiological studies.

Cerebellar stimulators were inserted into seven children who had cerebral palsy and in whom extensive investigation, including computerized tomography, had revealed no structural brain abnormality. A team including physiotherapists, occupational therapists, speech pathologists, and respiratory physiologists assessed the children pre- and postoperatively; their somatosensory evoked potentials were also measured. The mean age at implantation was 8.6 yearsl follow-up has ranged from 8 to 23 months (mean, 17.3 months). No adverse effects of the cerebellar stimulation have been noted. Detailed case histories obtained from the parents, together with formal assessment scores, indicate good improvement in six patients and mild but significant improvement in the seventh. Clinically, there has been gradual improvement in all seven patients. The charge density range associated with clinical improvement was 0.8 to 2.1 muCi/cm2/phase. The stimulation equipment must be monitored very carefully to ensure that any variation from the desired output is acceptably small because it is probable that sizable deviation is a determining factor in lack of response to this therapy.

Adolescent↗
PubMed1978

VA/Q inhomogeneity and AaDO2 in man during exercise: effect of SF6 breathing.

Pulmonary gas exchange was studied in five normal subjects both at rest and during moderate steady-state exercise on a bicycle ergometer while breathing a) room air and b) a mixture of 20.9% O2-balance sulfur hexafluoride (SF6). The alveolar-arterial oxygen pressure differences (AaDO2) widened significantly from rest to exercise. Breathing the O2-SF6 mixture reduced the AaDo2 significantly from 10.9 to 4.2 Torr at rest and from 15.5 to 10.1 Torr during exercise (P less than or equal to 0.01). There were no concurrent changes in metabolism, cardiac output, or heart rate during the SF6 breathing. Possible changes in the anatomic shunt fraction, alveolar-end-capillary equilibration, or the distribution of blood flow cannot account for these observations. We conclude that the AaDO2 increase during exercise reflects an inhomogeneity of ventilation-perfusion ratios (VA/Q) most probably arising within regions of the lung (intraregional inhomogeneity) rather than between regions (interregional inhomogeneity).

Adult↗
PubMed1978

A respiratory jacket for ventilatory measurements in children.

The properties of an air-filled polyurethane-coated nylon jacket for measuring volume parameters were determined on a model and in 13 subjects. There was a linear relationship between jacket pressure on a logarithmic scale and the lung volume change over an operating pressure range of 0.7-6 cmH2O. The magnitude of pressure change was frequency dependent. The magnitude of a calibration signal was reduced by superimposed tidal breathing. For the jacket tested, the calibration signal during tidal breathing was 87% of the calibration during apnea. With these properties established, a calibration technique was devised and tested on 13 infants. Corrected tidal volumes (VT) obtained with the jacket correlated well with those obtained with a pneumotachograph (r = 0.986). At the operating pressures used the jacket caused no significant change in functional residual capacity (FRC), VT, or frequency. The jacket is a reliable technique for measurement of VT and immediate changes in FRC in awake children.

Child, Preschool↗
PubMed1977

Contributions of changing rib cage--diaphragm interactions to the ventilatory depression of halothane anesthesia.

The ventilatory response to CO2 was subdivided into that portion due to increasing rib cage expansion, and that due to increased diaphragmatic descent. Five children were studied, awake, and anesthetized with halothane, 0.8-0.9%. During anesthesia there was a 67+/-8% reduction (mean+/-SE) in the slope of the response of overall ventilation to an increase in CO2. This was primarily due to an 89+/-8% reduction in the recruitment of rib cage ventilation (P less than .001). There was no significant change in the slope of the diaphragmatic response (anesthetized value 19+/-21% less than control), although the response curve was shifted to the right so that a higher CO2 concentration was needed to stimulate a given level of diaphragmatic excursion. Additional measurements of the inspiratory intercostal electromyogram in three adult subjects documented a rapid, profound depression of intercostal activity with halothane anesthesia that was associated with a marked decrease in rib cage ventilation. The authors conclude that a major component of the ventilatory depression associated with halothane anesthesia results from the preferential suppression of intercostal muscle function with relative sparing of diaphragmatic activity.

Adolescent↗
PubMedDate not supplied

The influence of chronic cerebellar stimulation on respiratory muscle coordination in a patient with cerebral palsy.

The effect of chronic cerebellar stimulation on respiratory muscle coordination has been evaluated using a relatively simple and objective target breathing test on one patient. Seven normal subjects were used as controls. Magnetometer recordings were used to determine whether abdominal and rib cage expansion were in phase. Subjects were asked to match their breathing frequency to a metronome signal. Their ability to control respiratory timing voluntarily was assessed in terms of the coefficient of variation (CV) of inspiratory time (Ti) and of expiratory time (Te). The CV's of Ti and Te were much greater in the patient in the absence of cerebrellar stimulation than they were in normal subjects. Both at 3 weeks and 6 months after implantation of the stimulator, a significant improvement in the performance of the patient was demonstrable with the stimulator on, although normal values were never achieved. This demonstrable influence of chronic cerebellar stimulation on respiratory muscle coordination has important implications for both the avoidance of respiratory complications and the potential improvement of speech in patients with cerebral palsy.

Adolescent↗