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Biomedical subjects

V Hudson

Publications and source records attributed to V Hudson.

5 recordsLinked to original sources
PubMed2002

Assessment of dynamic cerebral autoregulation based on spontaneous fluctuations in arterial blood pressure and intracranial pressure.

Assessments of dynamic cerebral autoregulation usually measure the cerebral blood flow velocity (CBFV) response to changes in arterial blood pressure (ABP). We studied the effect of substituting ABP by cerebral perfusion pressure (CPP), expressed as the difference between ABP and intracranial pressure (ICP), in estimates of dynamic autoregulation obtained by transfer function analysis. CBFV, ABP and ICP were recorded during periods of physiological stability in 30 patients with severe head injury. Transfer function analysis was performed using the following combinations of input-output variables: ABP-CBFV, CPP-CBFV and CBFV-ICP. Frequency and time-domain (step response) functions were averaged for recordings with mean ICP < 20 mmHg (group A) and mean ICP > or = 20 mmHg (group B). The ABP-CBFV transfer function parameters and step response for group A were similar to previous studies in normal subjects, but group B showed deterioration of dynamic autoregulation. Radically different step responses were obtained from both groups for the CPP-CBFV transfer function and the coherence was not significantly improved. The CBFV-ICP transfer function had the highest values of coherence and indicates that changes in CBFV are the cause of spontaneous fluctuations in ICP. Furthermore, the ICP step response plateau was significantly higher for group B than for group A. An alternative calculation of the CBFV step response to changes in CPP resembled the corresponding responses for the ABP input. For spontaneous fluctuations in ABP, ICP and CBFV, it is not possible to calculate the CPP-CBFV transfer function directly due to the high positive correlation between ICP and CBFV, but an alternative estimate can be obtained by using the CBFV-ICP transfer function. The latter could also be useful as a method to assess intracranial compliance in head injury patients.

Adult↗
PubMed2001

Swallowing dysfunction in infants less than 1 year of age.

BACKGROUND: Gastroesophageal reflux (GER) occurs frequently in infants and children and is implicated as a trigger for reactive airways disease. While evaluating patients for GER by upper gastrointestinal studies (UGI), we frequently noticed laryngeal penetration or tracheal aspiration in infants < 1 year of age. We conducted this prospective study to assess the incidence of swallowing dysfunction in infants with vomiting or respiratory symptoms. METHODS: Between February 1994 and August 1997, 1,003 UGI in infants < 1 year of age were performed by two experienced pediatric radiologists. Fluoroscopy of swallowing using an appropriate image intensifier was observed as part of the UGI in all patients. In addition to evaluating premature infants, former premature infants, and infants with underlying conditions such as bronchopulmonary dysplasia (BPD), congenital heart disease (CHD), esophageal atresia and/or tracheoesophageal fistula (EA), and neurologic disorders, we assessed swallowing in 472 full-term infants in the general population who had respiratory symptoms or suspected GER, but no other apparent abnormalities. Swallowing was not assessed in patients with congenital bowel obstruction. The presence of normal swallowing or swallowing dysfunction was recorded immediately following the study. Chest radiographs obtained on the same day as the UGI were evaluated in the study. Forty-four videotaped modified barium-swallow studies (MBSS) were obtained in 25 general-population infants and reviewed frame-by-frame to determine the length of time that barium could be visualized in the subglottic trachea. RESULTS: The incidence of swallowing dysfunction is significant in premature and former premature infants, those with BPD, CHD, EA, various syndromes, and neurologic abnormality. In the general population of full-term infants referred for evaluation of vomiting or respiratory symptoms, 63 (13.4 % of 472) had swallowing dysfunction. Forty-four had tracheal aspiration (TA) and 19 had laryngeal penetration (LP). Gastroesophageal reflux was found in 79.5 % with TA and in 68.4 % with LP. The MBSS confirmed swallowing dysfunction in all patients shown to have vocal cord penetration or tracheal aspiration by UGI. CONCLUSIONS: Careful evaluation of swallowing during an UGI can identify swallowing dysfunction in full-term infants who have respiratory problems, as well as in infants with an abnormality that predisposes the patient to aspiration. Episodes of tracheal aspiration may be fleeting and overlooked if swallowing is not assessed carefully. An MBSS can confirm the observation of swallowing dysfunction found during an UGI and assist in planning appropriate dietary therapy that minimizes the likelihood of tracheal aspiration during feeding.

Deglutition Disorders↗