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Biomedical subjects

A J Block

Publications and source records attributed to A J Block.

At least 55 records · Page 3Linked to original sources
PubMed1992

External stabilization of flail chest using continuous negative extrathoracic pressure.

On rare occasions after total sternectomy, patients develop persistent flail chest deformities requiring long-term mechanical respiratory assistance. We report the use of a temporary external chest shell to deliver constant negative extrathoracic pressure (CNEP) to a long-term ventilated patient with flail chest. The patient's anterior thoracic cage stabilized, and significant improvement in pulmonary function was observed. With these data in hand, an operation was done to permanently stabilize the anterior chest wall by bone grafting.

Aged↗
PubMed1991

Pancoast tumor: radiation therapy alone versus preoperative radiation therapy and surgery.

This is a retrospective analysis of 73 patients with non-oat cell carcinoma of the lung presenting as a Pancoast tumor. All patients were treated with curative intent between October 1964 and September 1987 (minimum follow-up 2 years). The treatment plan consisted of preoperative radiation therapy (usually 3000 cGy in 2 weeks or 4500 cGy in 5 weeks) in 41 patients and radiation therapy alone (usually 6500-7000 cGy in 6.5-8.0 weeks) in 32 patients. In general, radiation therapy alone was reserved for poor-prognosis patients (extensive disease or medical inoperability). Although 41 patients were initially scheduled to receive preoperative radiation therapy and surgery, the surgery was not performed in 12 cases (29%) because of patient refusal (4 patients), poor response to radiation therapy (4 patients), distant metastasis (2 patients), or debilitation (2 patients). Separate calculations were carried out for the patients who completed the surgery as planned (preoperative radiation therapy and surgery) and the entire group originally scheduled for combined-modality therapy. There was no significant difference in the absolute or cause-specific survival rates between treatment groups, but severe complications were significantly more common in patients receiving combined therapy.

Adult↗
PubMed1991

Pharyngeal volume in asymptomatic snorers compared with nonsnoring volunteers.

STUDY OBJECTIVE: to determine if asymptomatic snorers have smaller pharyngeal volumes than age- and height-matched nonsnorers. DESIGN: we recruited asymptomatic heavy snorers and nonsnorers for a study. Each snorer was matched by age (+/- 3 years) and height (+/- 2 inches) with a nonsnorer. The nonsnorers were required to be near ideal body weight. All volunteers underwent overnight polysomnography, pulmonary function testing, and magnetic resonance imaging of the pharynx while awake. The volume of the pharynx was determined by a computer with data input from a digitizing instrument. SETTING: Veterans Administration Hospital and University of Florida Teaching Hospital PARTICIPANTS: Nine volunteers were recruited for both the snorer and nonsnorer groups. Each participant was paid $50. There were no interventions. MEASUREMENTS AND RESULTS: There were no differences in sleep variables between the two groups. There was also no significant difference between pharyngeal volumes for the two groups. CONCLUSIONS: The volume of the pharynx in asymptomatic snorers is similar to the volume in age- and height-matched nonsnorers.

Adult↗
PubMed1991

The effect of nightly nasal CPAP treatment on underlying obstructive sleep apnea and pharyngeal size.

Nasal continuous positive airway pressure (CPAP) is an effective treatment for obstructive sleep apnea (OSA). It is usually prescribed for nightly use; however, recent studies show that patients often do not wear the appliance consistently. Previous studies have also suggested that nasal CPAP may improve a patient's underlying OSA even when the mask is not in place. We investigated 12 men with OSA to see if nasal CPAP used nightly for six weeks would improve their underlying sleep-disordered breathing. We also studied pharyngeal volumes measured using magnetic resonance imaging and a computer-controlled digitizing pad. Patients with more severe OSA had improvement after six weeks; however, they still demonstrated significant OSA. Patients with less severe OSA did not have significant change. We were unable to show a significant difference in any patient's awake pharyngeal volumes. We conclude that patients with OSA should be encouraged to wear their nasal CPAP machines regularly.

Humans↗
PubMed1990

Graded exercise testing and postthoracotomy complications.

A controversy exists over whether or not preoperative exercise testing can predict postthoracotomy complications. This study was designed to evaluate the usefulness of a presurgical exercise protocol in patients with lung disease, but no evidence of cardiac disease. Seventy patients underwent baseline pulmonary function testing and split function perfusion studies, when indicated, to calculate predicted postoperative pulmonary function. Noninvasive data were incrementally collected from 17 patients by using a treadmill exercise tolerance test that was designed to elicit maximal performance. Inhaled and exhaled gas flow and volume, the partial pressure of O2 and CO2, maximal O2 consumption (VO2max), and maximal minute ventilation (VE max) were measured. The breathing and heart rate reserves were calculated by standard formulae in an attempt to separate cardiac from pulmonary exercise limitation. Two patients had postoperative cardiopulmonary complications after thoracotomy and lung resection, and six patients had noncardiopulmonary complications. There was no significant prognostic relationship among VO2max, VE max, maximum O2 pulse, and the incidence of postoperative cardiopulmonary complications. The percentages of predicted VE max and predicted maximum heart rate were related to the occurrence of total complications, but not specifically to cardiopulmonary complications. The results emphasize the difficulty in attempting to exercise thoracotomy candidates with chronic lung disease to maximal performance. Excluding patients from further surgical consideration because of exercise limitation is not feasible based on these data.

Aged↗
PubMed1990

Effect of captopril injection in patients with moderate to severe hypertension.

The effect of intravenous captopril was studied in 24 white patients who had moderate to severe hypertension. Patients received incremental doses of 1 to 10 mg delivered at 10 min intervals over 50 to 80 min. Blood pressure (BP) was lowered within 5 to 10 min after the initial dose was administered and continued to decline, reaching a maximum response after 20 min (2 to 4 mg). At this time group mean BP fell from 175 +/- 3/111 +/- 1 to 166 +/- 3/97 +/- 2 mm Hg (P less than 0.01). Additional dose increments to an average cumulative dose of 40 mg did not increase the initial effect. No adverse side effects or symptomatic hypotension occurred in any subject. There was a significant correlation between diastolic BP decreases observed in response to intravenous captopril and subsequent long-term oral captopril therapy. The addition of hydrochlorothiazide increased the proportion of patients reaching normotension. We conclude that small intravenous bolus injections of captopril appear to be effective rapidly and are well tolerated in moderate to severe essential hypertension. Short-term intravenous administration seems to predict the response to chronic oral captopril therapy.

Administration, Oral↗
PubMed1990

Retrocalcaneal problems.

The majority of retrocalcaneal problems may be treated conservatively, using a biomechanical approach with appropriate shoe modification, padding, orthoses, and injection therapy. When appropriate indications are present, calcaneal osteotomies should be considered, despite less indication for these procedures than for simple resection of the retrocalcaneal exostoses.

Biomechanical Phenomena↗
PubMed1989

Measurement of pharyngeal volume by digitized magnetic resonance imaging. Effect of nasal continuous positive airway pressure.

Pharyngeal size is thought to play an important role in the pathogenesis of snoring and obstructive sleep apnea. It has been hypothesized that nasal continuous positive airway pressure (CPAP) works by enlarging pharyngeal size and splinting the airway open. In this study, we selected 12 heavy snorers and abolished their snoring with nasal CPAP in our sleep laboratory. Using magnetic resonance imaging and a computer program utilizing a digitizing pad, we measured these awake subjects' pharyngeal volumes without and with the nasal CPAP apparatus on at the level used to abolish their snoring. We found an average 27.7% increase in pharyngeal volume with nasal CPAP. We have visually shown an increase in pharyngeal size with the use of nasal CPAP in a cohort of heavy snorers.

Adult↗
PubMed1989

Nocturnal oxygen therapy does not improve snorers' intelligence.

STUDY OBJECTIVE: To determine whether nasal oxygen therapy at 2 L/min would (1) reverse nocturnal hypoxemia and (2) improve neuropsychologic function in men who snore heavily. DESIGN: To select heavy-snoring subjects for a treatment protocol, volunteers were screened for one night, breathing air the first half and oxygen the second half of the night. If nocturnal oxygen desaturation occurred in the first half and was improved in the second half of the night, the subject entered a two-month treatment program. In random order, either nocturnal air or nocturnal oxygen was administered for one month each at 2 L/min in a double-blind crossover design. Neuropsychologic testing was done before and after each month. SETTING: Oxygen concentrators were modified to produce either greater than 96 percent oxygen or air at 2 L/min. Machines were delivered to the home of the subject and the machines were used each night, administering inspirate by nasal cannula. PARTICIPANTS: Seventeen asymptomatic men who snored heavily and volunteered for minimal payment of $75. INTERVENTIONS: Air was administered for one month, and oxygen was administered for one month. MEASUREMENTS AND RESULTS: On the screening night, oxygen administration did not improve obstructive sleep apnea, but did improve oxygenation. After one month of oxygen therapy at night, there was no significant benefit to multiple measures of neuropsychologic function. CONCLUSION: In this study, oxygen therapy at night had no effect on neuropsychologic function in men who snore heavily.

Adult↗
PubMed1989

Consistency of respiratory measurements from night to night during the sleep of elderly men.

Fourteen healthy elderly men had polysomnography performed on two consecutive nights to assess the consistency of sleep and breathing from night to night. The reported first-night effect was seen on electroencephalographic sleep, leading to lighter or fitful sleep on the first night. Mean values for apneas, hypopneas, and oxygen desaturations did not change from night 1 to night 2. Five of 14 subjects would have changed classification from night to night if a cutoff of five apneas and hypopneas per hour were used to define normality. Because this numerical cutoff may not be valid in the elderly, the clinical significance of such a changing classification is not clear.

Aged↗
PubMed1988

Do patients with sleep apnea die in their sleep?

Patients with sleep apnea syndrome (SAS) show cardiac dysrhythmias in association with cyclical nocturnal hypoxemia; are they at risk of dying during sleep? To assess this claim, we reviewed the clinical course of 91 patients with polysomnographically documented SAS between July 1978 and June 1986. A control group was comprised of 35 patients who were referred with symptoms suggestive of SAS but had negative sleep studies. Follow-up was obtained by survey questionnaire. Nine of 91 SAS and four of 35 control patients had died by completion of the study. There were no statistically significant differences in mortality between the two groups. None of the SAS patients died in their sleep, but they reported a higher incidence of disability and vehicular mishaps than did control subjects. The findings in this study do not support the hypothesis that SAS patients are at increased risk of dying in their sleep.

Body Weight↗
PubMed1988

Stereoselectivity of tocainide pharmacodynamics in vivo and in vitro.

Racemic tocainide [R,S-T], which is used in the treatment of ventricular arrhythmias, consists of an R(-)-enantiomer [R-T] and an S(+)-enantiomer [S-T]. The present experiments examined these substances for pharmacodynamic differences. The ability of various doses of R-T, S-T, and R,S-T to both induce ataxia (A) and protect against chloroform-induced ventricular arrhythmias (P) in mice were compared at 20 min after subcutaneous treatment. For A effects, the ED50S (95% Fieller Limits) of R-T, S-T, and R,S-T were 125 (78-802), 125 (84-283), and 90 (61-149) mg/kg, respectively. For P effects, the ED50S were 40 (11-71), 116 (82-204), and 86 (55-187) mg/kg. The ratios of A/P, a measure of the margin of safety, were 3.1, 1.1, and 1.0. Effects upon intracardiac conduction in isolated rabbit hearts also exhibited, qualitatively, similar patterns of selectivity. At 1 X 10(-4) M intraatrial, His-Purkinje, intraventricular conduction times, and the QT interval were prolonged with the following order of potency: R-T greater than R,S-T greater than S-T; A-V nodal conduction was unchanged. R-T also evoked the greatest decrease in contractility. With respect to separation of antiarrhythmic action and the production of ataxia, R-T has a greater margin of safety than either S-T or R,S-T.

Animals↗