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Biomedical subjects

D C Shannon

Publications and source records attributed to D C Shannon.

At least 73 records · Page 4Linked to original sources
PubMed1985

Familial vocal cord dysfunction.

Vocal cord paralysis is a common cause of neonatal stridor. Familial vocal cord dysfunction, however, is unusual. All three siblings in one family had neonatal stridor. Vocal cord dysfunction was confirmed after endoscopic examination in two of the children; a temporary tracheotomy was required by one child. Results of evaluation, including pulmonary function tests, suggest discrete dysfunction localized to the neuromuscular pathway responsible for vocal cord abduction. Endoscopy is of prime importance in the diagnosis of vocal cord dysfunction. In considering therapy, the physician must weigh both the potentially life-threatening nature of vocal cord paralysis, as well as the likelihood of eventual spontaneous resolution of many familial and idiopathic cases.

Airway Obstruction↗
PubMed1984

Incidence and significance of primary abnormalities of cardiac rhythm in infants at high risk for sudden infant death syndrome.

The exact relationship between cardiac arrhythmias and sudden infant death syndrome (SIDS) is uncertain. Several reports have implicated both ventricular and supraventricular arrhythmias in isolated cases, but there have been no studies of the incidence or type of arrhythmias that occur in populations at risk for SIDS. Of 1699 infants at high risk for SIDS, 60 (4%) were found to have a primary cardiac arrhythmia (i.e., not associated with disordered respiration or apnea). The incidence of atrial and ventricular premature beats, supraventricular tachycardia, and Wolff-Parkinson-White syndrome was similar to the incidence found in normal infants. Primary bradycardia (defined as a heart rate less than 60 for greater than 10 s not associated with abnormal respiration) was the most common arrhythmia, occurring with a frequency and severity not seen in normal infants. Thirty-two infants experienced periodic bradycardia. In 19 of these latter infants, there were symptoms associated with these bradyarrhythmias that necessitated treatment. Heart rates as low as 20 beats/min were recorded. One infant presented with an episode of ventricular fibrillation and on further evaluation was noted to have recurrent bradyarrhythmias. In no infant was there abnormal prolongation of the QT interval. Primary bradyarrhythmias are seen at an increased incidence in infants at high risk for SIDS and may play a causal role in this syndrome. Most symptomatic infants can be adequately controlled with sympathomimetic or parasympatholytic therapy. Other cardiac arrhythmias occur at a rate similar to that in normal infants and are therefore unlikely to play a major role in SIDS.

Arrhythmias, Cardiac↗
PubMed1984

Sudden infant death syndrome: abnormalities in short term fluctuations in heart rate and respiratory activity.

In order to test the hypothesis that a defect in cardiorespiratory regulation contributes to death of infants from sudden infant death syndrome (SIDS), we analyzed the power spectra of heart rate and respiratory activity during 256-sec epochs of quiet sleep. Data were obtained from pneumogram recordings performed for 12 h at night on eight infants who subsequently died from SIDS and 22 age-matched control infants. We computed the heart rate and respiratory power spectra from a single epoch on each infant using an algorithm developed for an 8085 microprocessor system dedicated to this investigation. There was no statistically significant difference between SIDS and controls based on mean respiratory and heart rates. Spectral analysis revealed enhancement of low frequency power in the 0.02 to 0.1 Hz band in the heart rate power spectrum in the SIDS group compared to control (p less than 0.002) and dispersion in respiratory frequency as determined by the respiratory band width (p less than 0.00001). These data suggest that a predisposition to SIDS manifests itself in an abnormal pattern of fluctuations in heart rate and respiratory activity.

Female↗
PubMed1981

Power spectrum analysis of heart rate fluctuation: a quantitative probe of beat-to-beat cardiovascular control.

Power spectrum analysis of heart rate fluctuations provides a quantitative noninvasive means of assessing the functioning of the short-term cardiovascular control systems. We show that sympathetic and parasympathetic nervous activity make frequency-specific contributions to the heart rate power spectrum, and that renin-angiotensin system activity strongly modulates the amplitude of the spectral peak located at 0.04 hertz. Our data therefore provide evidence that the renin-angiotensin system plays a significant role in short-term cardiovascular control in the time scale of seconds to minutes.

Angiotensins↗
PubMed1981

Survival, cost of hospitalization, and prognosis in infants critically ill with respiratory distress syndrome requiring mechanical ventilation.

It was found that, during 1974, it cost an average of $8842 ($12,909 in 1979) to care for a survivor of severe respiratory distress syndrome (RDS) who required mechanical ventilation in this ICU compared to $2448 ($3574 in 1979) for nonsurvivors. Death in 15 out of the 16 nonsurvivors was accompanied by grade III-IV intraventricular hemorrhage. This complication also accounted for moderate to severe neurological impairment in two of the three survivors so affected. The cost of care prorated for life expectancy was $0.42 ($0.61 in 1979) per day of life. These data are compared with similar data generated from adult intensive care patients from the same institution.

Costs and Cost Analysis↗
PubMed1981

Ventilatory chemoreceptor response in parents of children at risk for sudden infant death syndrome.

We postulated that parents of infants who sustain near-death episodes associated with defective chemical regulation of breathing might share a similar defect. We, therefore, measured the ventilatory responses to progressive hypoxia and hypercapnia individually in eight sets of parents of infants who had sustained at least one near-death episode (apnea, cyanosis, pallor, limpness, and responsive only to mouth-to-mouth resuscitation); each infant had a ventilatory response to CO2 which was more than 2 S.D. below the mean normal. Ventilatory function measured by vital capacity forced expiratory volume 1.0 and flow curves was normal in each group. Responses to hypercapnia and hypoxemia in both fathers and mothers were similar to 11 pairs of controls. Ventilation during CO2 rebreathing normalized for surface area increased 0.87 liter/min/mm Hg in fathers, 0.94 in controls, 0.87 in mothers, and 0.75 in controls. Ventilation during progressive hypoxemia increased 88 liter/min/1 divided by mm Hg in fathers, 92 in controls, 86 in mothers, and 101 in controls. None of these differences was significant.

Adult↗
PubMed1981

Episodic complete airway obstruction in infants.

Four infants with episodic silent complete obstructed apnea are described. All had central sleep apnea, three had hypoventilation, and none had obstructive apnea observed on polygraphic recordings. Two infants were siblings of a sudden infant death syndrome victim and one was a sibling of a "near miss" infant. One infant died as a result of a prolonged episode that began while she was awake. In two infants apnea has been controlled with theophylline administration and in the third infant resolution of the episode was temporally related to atropine administration.

Airway Obstruction↗
PubMed1981

Treatment of apnea and excessive periodic breathing in the full-term infant.

Twenty-two full-term infants, aged 0 to 6 weeks, with a history of unexplained apnea and respiratory abnormalities on pneumogram recordings, were treated with theophylline (average dose 7.5 mg/kg/day and average serum level 11 micrograms/ml). Subsequent recordings showed a significant decrease in the amount of periodic breathing (14.3% vs 0.7%) and apnea 10 to 14.9 seconds (12.8 vs 1.0/100 min) when compared to the initial pneumogram. It is concluded that theophylline therapy in this group of infants will result in a reduction of apnea and periodic breathing.

Apnea↗
PubMed1980

Fulminant neonatal meningococcemia.

Neisseria meningitidis is a rare cause of infection in infants younger than 2 months of age, presumably because of transplacental passage of protective maternal antibodies. In most reported cases of meningococcal disease in neonates, a relatively mild clinical course has been observed. A 25-day-old infant survived acute, severe meningococcemia due to group B N meningitidis. This organism should be considered when neonates have signs of septicemia, especially in the presence of cutaneous petechiae and purpura.

Humans↗
PubMed1980

Pathophysiologic mechanisms causing sleep apnea and hypoventilation in infants.

Complete absence of chemoreception in the medulla is characterized by sustained hypoventilation. Except for the first months of life, this deficit does not, of itself, cause apnea. Both in infants who lack central chemical drive, as well as those who are only partly deficient, it is necessary to invoke at least one further pathophysiologic event. Various alterations in gas exchange, especially during sleep, which promote hypoxemia can contribute to a positive feedback effect on ventilation. If gas exchange is further impeded by upper-airway obstruction, only a massive arousal response separates the infant from death.

Airway Obstruction↗