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Biomedical subjects

N B Hampson

Publications and source records attributed to N B Hampson.

At least 37 records · Page 2Linked to original sources
PubMed1996

Central nervous system oxygen toxicity during hyperbaric treatment of patients with carbon monoxide poisoning.

Hyperbaric oxygen (HBO2) is associated with a recognized risk for clinical central nervous system (CNS) toxicity. The risk for oxygen convulsions during routine hyperbaric treatment of most routine conditions is extremely low. Previous observations have suggested that the incidence of CNS toxicity during HBO2 treatment for carbon monoxide (CO) poisoning may be increased, both because of CNS injury caused by the poisoning and because higher treatment pressures are often utilized for this condition. This study reviews data from 900 CO-poisoned patients treated with HBO2 at Virginia Mason and Duke University Medical Centers from 1987 to 1996. One-third of the patient population was treated at each of the three HBO2 treatment pressures most commonly utilized for CO intoxication in North American multiplace chambers. Patient characteristics were similar in all groups. Among the 300 consecutive patients treated at each pressure, there was one seizure at 2.45 atm abs (0.3%), nine seizures at 2.80 atm abs (2.0%), and six seizures at 3.00 atm abs. This difference is statistically significant (P = 0.032; Fisher's Exact Test). The potential difference in seizure risk should be considered when selecting the HBO2 treatment pressure for CO poisoning.

Adult↗
PubMed1995

Pulmonary embolism: difficulties in the clinical diagnosis.

Pulmonary embolism is a common disease in the United States, affecting as many as 500,000 persons annually. Unfortunately, underdiagnosis of the disorder is also common, resulting in significant excess morbidity and mortality rates. Factors such as a lack of symptoms or the unavailability of effective testing techniques are not the reasons for pulmonary embolism's underdiagnosis. Instead, the disease is often often overlooked because the symptoms and signs caused by pulmonary embolism are nonspecific and may be confused with a variety of other cardiopulmonary disorders that have similar presentations. In addition to this overlap of symptoms and signs, pulmonary embolism frequently coexists with those diseases it mimics. This article describes the clinical characteristics of pulmonary venous thromboembolism, reviewing the symptoms and signs it typically exhibits, as well as the disease's routine laboratory test and chest radiographic abnormalities. These are contrasted with the clinical features of pneumonia, the disease for which pulmonary embolism is most commonly mistaken. I will show that clinical features can be used to increase suspicion for pulmonary embolism, but that additional diagnostic testing is necessary to definitively diagnose or exclude the condition. Accurate diagnostic tests are available for venous thromboembolism, even in the face of other coexistent cardiopulmonary disorders. As such, it should be possible to significantly reduce the morbidity and mortality rates caused by pulmonary embolism through both heightened clinical awareness and appropriate use of diagnostic testing strategies.

Aged↗
PubMed1994

Carbon monoxide poisoning from indoor burning of charcoal briquets.

OBJECTIVE: To describe the case characteristics of a series of patients poisoned with carbon monoxide (CO) resulting from indoor burning of charcoal briquets. DESIGN: Cases of patients with unintentional CO poisoning referred for treatment with hyperbaric oxygen were reviewed. Cases that occurred as the result of indoor burning of charcoal briquets were analyzed. SETTING: A private, urban, tertiary care center. PATIENTS: Seventy-nine patients ranging from 3 months to 87 years of age referred from 10 counties within the state of Washington between October 1982 and October 1993. RESULTS: Of 509 patients treated for acute unintentional CO poisoning, 79 cases occurred in 32 incidents as a result of indoor burning of charcoal briquets, for the purpose of either home heating or cooking. A majority of cases occurred in the months of October through January, commonly during power outages or when electricity was intentionally disconnected. Patients of minority races were disproportionately represented compared with the general population of the region. CONCLUSIONS: Carbon monoxide poisoning is a significant hazard from indoor use of charcoal briquets. All cases are avoidable and public awareness of the risk should be enhanced.

Adolescent↗
PubMed1994

Reduction in patient timing errors using a breath-activated metered dose inhaler.

Delivery of aerosol medication to the lower respiratory tract by metered dose inhaler (MDI) is often limited by the patient's inability to properly coordinate activation of the device with inspiration. This study evaluated a new breath-activated MDI device, designed to minimize patient timing errors by sensing inspiratory flow and automatically activating to deliver aerosol medication. Twenty novice adult volunteers, previously naive to the technique of MDI use, and 20 patients currently using MDIs were tested in their ability to coordinate MDI usage. Simultaneous recording of respiratory events and device activation allowed analysis of timing errors. With a conventional MDI, a 31.0 percent incidence of errors was seen in the novice group and a 21.5 percent incidence of errors was seen in the experienced group. These compared with error rates using the breath-activated MDI of 6.5 percent and 5.0 percent in the two groups respectively (p = 0.009, p = 0.04). The breath-activated inhaler was preferred by 35 of 40 subjects. In conclusion, MDI technique timing errors were significantly less with this breath-activated MDI device in both novice and experienced subjects, and it was also preferred by both groups.

Adolescent↗
PubMed1993

Hyperbaric oxygen therapy for radiation-induced hemorrhagic cystitis.

From May 1988 through May 1991, 14 patients with radiation-induced hemorrhagic cystitis confirmed by cystoscopy and biopsy, who had failed all other attempts at management and who had no evidence of infection or recurrent malignancy, were treated with hyperbaric oxygen therapy. During followup ranging from 10 to 42 months 8 patients (57%) had complete resolution of symptoms and 2 (14%) had marked improvement, for a total of 10 patients (71%) with a positive outcome. Of 4 patients (29%) with a poor outcome 3 had limited improvement and were later diagnosed as having recurrent malignancy that was not present on biopsy before hyperbaric treatment. One patient was withdrawn from hyperbaric treatment due to illness. The average cost per patient was $10,000 to $15,000, comparing favorably to the cost of multiple conservative treatments to control symptoms. Hyperbaric oxygen therapy for radiation-induced hemorrhagic cystitis appears to be an efficacious treatment modality for patients who have failed other forms of management.

Adolescent↗
PubMed1991

Panlobular emphysema in young intravenous Ritalin abusers.

We studied a distinctive group of young intravenous Ritalin abusers with profound obstructive lung disease. Clinically, they seemed to have severe emphysema, but the pathologic basis of their symptoms had not been investigated previously. Seven patients have died and been autopsied: in four, the lungs were fixed, inflated, dried, and examined in detail radiologically, grossly, microscopically, and by electron probe X-ray microanalysis. All seven patients had severe panlobular (panacinar) emphysema that tended to be more severe in the lower lung zones and that was associated with microscopic talc granulomas. Vascular involvement by talc granulomas was variable, but significant interstitial fibrosis was not present. Five patients were tested for alpha-1-antitrypsin deficiency and found to be normal, as were six similar living patients. These findings indicate that some intravenous drug abusers develop emphysema that clinically, radiologically, and pathologically resembles that caused by alpha-1-antitrypsin deficiency but which must have a different pathogenesis. Talc from the Ritalin tablets may be important, but the mechanism remains to be elucidated.

Adult↗
PubMed1991

Oral antibiotics for pneumonia.

The majority of patients presenting with community-acquired pneumonia can be treated with oral antibiotics and can be managed successfully as outpatients. Oral-antibiotic selection requires a knowledge of the classes of antibiotics available, utility of diagnostic testing, epidemiology of pneumonia, and a rational approach to empiric therapy when a cause cannot be immediately identified. These topics are reviewed, with the goal improved therapeutic efficacy in the oral treatment of pneumonia.

Administration, Oral↗
PubMed1990

Near-infrared optical responses in feline brain and skeletal muscle tissues during respiratory acid-base imbalance.

The effects of hyper- and hypocapnia on oxidative metabolism were evaluated by near-infrared (NIR) multiwavelength spectroscopy in intact brain and skeletal muscle tissues of the anesthetized cat. A 3-wavelength NIR algorithm was used to monitor cytochrome a,a3 oxidation state, regional blood volume, and tissue oxyhemoglobin and O2 stores simultaneously in brain and muscle in ventilated animals. Incremental hypercapnia was produced in 10 cats by raising arterial pCO2 from 27.0 +/- 1.3 to 95.1 +/- 1.9 mmHg with inspired CO2. Hypercapnia produced progressive increases in cerebral HbO2, blood volume, and cytochrome a,a3 oxidation state (P less than 0.01). In contrast, CO2 simultaneously decreased all 3 NIR parameters in intact hindlimb muscles (P less than 0.01). Blood volume changes during hypercapnia correlated with changes in blood flow measured qualitatively by intravascular injections of indocyanine green dye. Hypocapnia produced by hyperventilation in 8 cats lowered paCO2 from 28.5 +/- 0.4 to 13.5 +/- 0.5 mmHg. Hypocapnia decreased cerebral HbO2, blood volume, and cytochrome a,a3 redox level (P less than 0.05), but NIR changes were not seen in skeletal muscle. These experiments demonstrate preferential distribution of oxygen to brain during hypercapnia and the ability of NIR spectroscopy to assess regional oxygenation in multiple tissues non-invasively.

Acid-Base Imbalance↗
PubMed1990

Cerebral oxygen availability by NIR spectroscopy during transient hypoxia in humans.

The effects of mild hypoxia on brain oxyhemoglobin, cytochrome a,a3 redox status, and cerebral blood volume were studied using near-infrared spectroscopy in eight healthy volunteers. Incremental hypoxia reaching 70% arterial O2 saturation was produced in normocapnia [end-tidal PCO2 (PETCO2) 36.9 +/- 2.6 to 34.9 +/- 3.4 Torr] or hypocapnia (PETCO2 32.8 +/- 0.6 to 23.7 +/- 0.6 Torr) by an 8-min rebreathing technique and regulation of inspired CO2. Normocapnic hypoxia was characterized by progressive reductions in arterial PO2 (PaO2, 89.1 +/- 3.5 to 34.1 +/- 0.1 Torr) with stable PETCO2, arterial PCO2 (PaCO2), and arterial pH and resulted in increases in heart rate (35%) systolic blood pressure (14%), and minute ventilation (5-fold). Hypocapnic hypoxia resulted in progressively decreasing PaO2 (100.2 +/- 3.6 to 28.9 +/- 0.1 Torr), with progressive reduction in PaCO2 (39.0 +/- 1.6 to 27.3 +/- 1.9 Torr), and an increase in arterial pH (7.41 +/- 0.02 to 7.53 +/- 0.03), heart rate (61%), and ventilation (3-fold). In the brain, hypoxia resulted in a steady decline of cerebral oxyhemoglobin content and a decrease in oxidized cytochrome a,a3. Significantly greater loss of oxidized cytochrome a,a3 occurred for a given decrease in oxyhemoglobin during hypocapnic hypoxia relative to normocapnic hypoxia. Total blood volume response during hypoxia also was significantly attenuated by hypocapnia, because the increase in volume was only half that of normocapnic subjects. We conclude that cytochrome a,a3 oxidation level in vivo decreases at mild levels of hypoxia. PaCO is an important determinant of brain oxygenation, because it modulates ventilatory, cardiovascular, and cerebral O2 delivery responses to hypoxia.

Adult↗
PubMed1988

Endobronchial telangiectasias and hemoptysis in scleroderma.

Hemoptysis is considered a rare event in scleroderma and to date only two previous cases could be identified. The occurrence of hemoptysis with bleeding and friable telangiectasias is reported in a patient with rapidly progressing systemic sclerosis. This represents the first report of this association, although bleeding telangiectasias have been reported in other systems. A brief review of the relevant literature is included.

Bronchi↗
PubMed1988

Near infrared monitoring of human skeletal muscle oxygenation during forearm ischemia.

Changes in tissue oxygenation of forearm muscles were measured by near infrared (NIR) spectrophotometry in 10 healthy adults during tourniquet ischemia and venous outflow restriction. Muscle O2 stores were depleted rapidly by forearm ischemia manifest by a progressive decrease in tissue oxyhemoglobin and oxymyoglobin over 4-5 min. Muscle ischemia significantly decreased the oxidation level of cytochrome aa3, to below resting base line after only 1.5 min, and the enzyme became fully reduced after 6.5 min. After 8 min of ischemia, tourniquet release was accompanied by a transient increase in muscle blood volume due to influx of oxyhemoglobin. The cytochrome aa3 oxidation level increased above resting base line within 1 min after tourniquet release. Transcutaneous PO2 measurements recorded simultaneously from the same forearm correlated poorly with the kinetics of O2 availability and cytochrome oxidation in the underlying muscle tissue; this was not unexpected because overlying skin did not contribute significantly to NIR muscle signals. Venous outflow restriction without inflow obstruction increased muscle deoxyhemoglobin and tissue blood volume but did not change muscle O2 stores or cytochrome aa3 oxidation level. The ability of the NIR technique to detect dynamic trends in tissue oxygenation reveals that muscle O2 is rapidly consumed during tourniquet ischemia and rapidly restored by hyperemic responses after brief ischemia.

Blood Pressure↗
PubMed1987

Skeletal muscle oxygen availability during respiratory acid-base disturbances in cats.

Respiratory acid-base disorders elicit physiological responses that alter O2 delivery to various tissues. We have used a near infrared (NIR) optical technique to monitor cytochrome a,a3 oxidation state, tissue O2 store (relative hemoglobin plus myoglobin oxygenation), and regional blood volume in intact resting skeletal muscle during respiratory acid-base disturbances in anesthetized cats. Hypercapnic acidosis and hypocapnic alkalosis were produced in separate groups of animals by ventilation with increasing concentrations of CO2 (n = 13) or hyperventilation (n = 8). Respiratory acidosis decreased oxygen availability to hindlimb muscle while respiratory alkalosis did not change tissue oxygenation. Inspired CO2 progressively decreased muscle blood volume, cytochrome a,a3 oxidation level, and muscle oxygen store. These optical responses were greatly attenuated both by pre-treatment with bretylium and by hemorrhagic hypotension, suggesting mediation through sympathetic vasoconstriction. Metabolic acidosis, produced by intravenous HCl infusion (n = 8), did not reproduce the hindlimb optical responses mediated by CO2. These experiments demonstrate that hypercapnic acidosis significantly decreases oxygen supply to resting skeletal muscle in the anesthetized cat, probably via neuroregulatory responses to CO2 which do not depend on changes in arterial [H+] in the tested pH range.

Acidosis, Respiratory↗