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Biomedical subjects

D Seaton

Publications and source records attributed to D Seaton.

At least 19 recordsLinked to original sources
PubMed2001

Determination of right ventricular ejection fraction from reprojected gated blood pool SPET: comparison with first-pass ventriculography.

Gated blood pool (GBP) studies are widely available and relatively inexpensive. We have previously published a simple and convenient method for measuring left ventricle ejection fraction (EF) with increased accuracy from single-photon emission tomography (SPET) GBP scans. This paper describes an extension of this method by which right ventricular EF may also be measured. Gated SPET images of the blood pool are acquired and re-oriented in short-axis slices. Counts from the left ventricle are excluded from the short-axis slices, which are then reprojected to give horizontal long-axis images. Time-activity curves are generated from each pixel around the right ventricle, and an image is created with non-ventricular pixels "greyed out". This image is used as a guide in drawing regions of interest around the right ventricle on the end-diastolic and end-systolic long-axis images. In 28 patients, first-pass ventriculography studies were acquired followed by SPET GBP scans. The first-pass images were analysed a total of four times by two observers and the SPET images were analysed three times each by two observers. The agreement between the two techniques was good, with a correlation coefficient of 0.72 and a mean absolute difference between first-pass and reprojected SPET EFs of 4.8 EF units. Only four of the 28 patients had a difference of greater than 8 EF units. Variability was also excellent for SPET right ventricular EF values. Intra-observer variability was significantly lower for SPET than for first-pass EFs: standard error of the estimate (SEE)=5.1 and 7.3 EF units, respectively (P<0.05). Inter-observer variability was comparable in the two techniques (SEE=5.2 and 6.9 EF units for SPET and first-pass ventriculography, respectively).

Adult↗
PubMed2001

Bedside tracer gas technique accurately predicts outcome in aspiration of spontaneous pneumothorax.

BACKGROUND: There is no technique in general use that reliably predicts the outcome of manual aspiration of spontaneous pneumothorax. We have hypothesised that the absence of a pleural leak at the time of aspiration will identify a group of patients in whom immediate discharge is unlikely to be complicated by early lung re-collapse and have tested this hypothesis by using a simple bedside tracer gas technique. METHODS: Eighty four episodes of primary spontaneous pneumothorax and 35 episodes of secondary spontaneous pneumothorax were studied prospectively. Patients breathed air containing a tracer (propellant gas from a pressurised metered dose inhaler) while the pneumothorax was aspirated percutaneously. Tracer gas in the aspirate was detected at the bedside using a portable flame ioniser and episodes were categorised as tracer gas positive (>1 part per million of tracer gas) or negative. The presence of tracer gas was taken to imply a persistent pleural leak. Failure of manual aspiration and the need for a further intervention was based on chest radiographic appearances showing either failure of the lung to re-expand or re-collapse following initial re-expansion. RESULTS: A negative tracer gas test alone implied that manual aspiration would be successful in the treatment of 93% of episodes of primary spontaneous pneumothorax (p<0.001) and in 86% of episodes of secondary spontaneous pneumothorax (p=0.01). A positive test implied that manual aspiration would either fail to re-expand the lung or that early re-collapse would occur despite initial re-expansion in 66% of episodes of primary spontaneous pneumothorax and 71% of episodes of secondary spontaneous pneumothorax. Lung re-inflation on the chest radiograph taken immediately after aspiration was a poor predictor of successful aspiration, with lung re-collapse occurring in 34% of episodes by the following day such that a further intervention was required. CONCLUSIONS: National guidelines currently recommend immediate discharge of patients with primary spontaneous pneumothorax based primarily on the outcome of the post-aspiration chest radiograph which we have shown to be a poor predictor of early lung re-collapse. Using a simple bedside test in combination with the post-aspiration chest radiograph, we can predict with high accuracy the success of aspiration in achieving sustained lung re-inflation, thereby identifying patients with primary spontaneous pneumothorax who can be safely and immediately discharged home and those who should be observed overnight because of a significant risk of re-collapse, with an estimated re-admission rate of 1%.

Adult↗
PubMed2001

Iatrogenic pneumothorax: marker gas technique for predicting outcome of manual aspiration.

BACKGROUND: Although manual aspiration is used for treating pneumothorax, the post-aspiration radiograph may not be a reliable indicator of whether the pleural leak remains. We have previously shown that marker gas can identify an air leak in patients with spontaneous pneumothoraces. OBJECTIVE: This study examines whether a marker gas technique can be safely used to manage patients with iatrogenic pneumothoraces. METHODS: 10 patients with iatrogenic pneumothorax were identified among a cohort referred for manual aspiration of pneumothorax, using a marker gas technique, in which inspired metered-dose inhaler propellant gas is detectable in pneumothorax aspirate using a portable flame ioniser. The presence of marker gas was taken to imply a persistent air leak. RESULTS: Marker gas was detected in the aspirate from 3 out of 10 pneumothoraces. 2 required intercostal tube drainage because of lung collapse following initial aspiration and 1 was treated conservatively. Marker gas was not detected in 7 cases (2 post-pacemaker insertion, 5 pleural aspiration +/- biopsy), and in all these cases, manual aspiration resulted in sustained re-expansion of the lung. There was a trend towards a significant relationship between the presence or absence of marker gas and the need for a further intervention (p = 0.055). CONCLUSION: The presence or absence of a pleural leak during manual aspiration of iatrogenic pneumothorax can be demonstrated by this technique. The absence of marker gas in the aspirate implies that manual aspiration will be successful, whereas its presence, in most cases, predicts either failure of manual aspiration to expand the lung or early re-collapse of the lung.

Aged↗
PubMed2000

Investigative modalities of mandibular invasion by squamous cell carcinoma.

OBJECTIVES/HYPOTHESIS: To compare preoperative investigations with histological findings in squamous cell carcinoma (SCC) of the oral mucosa that abuts the mandible. Both clinical and radiological examinations fail to predict accurately invasion of the mandible by intraoral SCC. STUDY DESIGN: This two-part, prospective study is of a consecutive series of patients whose first malignancy of the upper aerodigestive tract abutted the lingual surface of the mandible. METHODS: AR patients presented to the Queensland Radium Institute Head and Neck Clinic between 1993 and 1997 with a biopsy-proven SCC that abutted the mandible. These tumors were investigated clinically, radiologically, and histologically. Sensitivity, specificity, and predictive values were calculated for various approaches. In the second part of the study, single photon emission computed tomography (SPECT) bone scans were included. Quantification ratios of bone scans compared the average counting statistics in visually identified mandibular abnormal uptake with normal cervical spine and jaw. RESULTS: Sixty-seven patients were followed for 55 months and assessed with orthopantomogram (OPG), computed tomography (CT) scans, and, in the second part of the study, SPECT bone scans. Thirty-six tumors showed histological evidence of bony invasion. Bony involvement was suggested by OPG in 36 and confirmed histologically in 27 patients. CT scans showed evidence of bone invasion in 22 cases, with 18 of these histologically confirmed. Technetium 99m methylene diphosphonate (MDP) bone scans with planar imaging and SPECT were performed in 24 patients, and histological appearance was suitable for analysis in 14. Three patients with tumor (cervical spine ratios greater than 1.5 predicting malignant involvement) had this confirmed histologically. CONCLUSIONS: The first part of the study confirms our hypothesis that currently used investigations, as well as clinical assessment, fail to predict accurately invasion of the mandible by intraoral SCC. The second part suggests that SPECT scanning with high quantification ratios is promising in the prediction of tumor involvement.

Carcinoma, Squamous Cell↗
PubMed1991

Spontaneous pneumothorax: marker gas technique for predicting outcome of manual aspiration.

OBJECTIVE: To determine whether in a patient with spontaneous pneumothorax the presence or absence of a pleural leak can be shown at the time of manual aspiration by use of a marker gas. Also, to find out if the technique can predict whether manual aspiration will be successful, hence avoiding the need for intercostal tube drainage. DESIGN: Prospective study of 25 episodes of pneumothorax during which patients breathed air from a Douglas bag that contained chlorofluorocarbon gases from a metered dose inhaler while the pneumothorax was aspirated. SETTING: Medical unit of a district general hospital. PATIENTS: 22 patients who presented over nine months with acute pneumothorax. MAIN OUTCOME MEASURES: Presence or absence of chlorofluorocarbon marker gases in the aspirate. Presence or absence of sustained re-expansion of the affected lung in the chest radiograph. RESULTS: Marker gas was detected in the aspirate from 16 out of 25 pneumothoraces. Of these, 13 required intercostal tube drainage because of failure of the lung to re-expand. Marker gas was not detected in nine cases, and in all of these cases manual aspiration resulted in sustained re-expansion of the lung. CONCLUSIONS: The presence or absence of a pleural leak during manual aspiration of spontaneous pneumothorax can be shown by using this technique. The absence of marker gas in the aspirate implies that manual aspiration will be successful, whereas its presence predicts, in most cases, either failure of manual aspiration to expand the lung or early re-collapse of the lung.

Acute Disease↗
PubMed1988

The relationship between nasal airway size and nasal-oral breathing.

Most clinicians agree that impaired nasal breathing results in obligatory mouth breathing. Some believe that mouth breathing influences dentofacial growth; others disagree. The term mouth breathing is confusing because total mouth breathing rarely occurs. A combination of nasal and oral breathing is more usual. The purpose of the present study involving 116 adult subjects was to (1) assess the relationship between nasal impairment and nasal-oral breathing, (2) determine the switching range from nasal to nasal-oral breathing, and (3) quantify the term mouth breathing. The pressure-flow technique was used to estimate nasal airway size; inductive plethysmography was used to assess nasal-oral breathing in normal and impaired breathers. Analysis of the date showed a Pearson rank correlation of 0.545 (P less than 0.001) between nasal area and nasal-oral respiration. Ninety-seven percent of subjects with a nasal size less than 0.4 cm2 were mouth breathers to some extent. About 12% of subjects with an adequate airway were assumed to be habitual mouth breathers. The findings indicate that the switching range from nasal to nasal-oral breathing is very narrow (0.4-0.45 cm2). These results also confirm our contention that in adults an airway less than 0.4 cm2 is impaired.

Adult↗
PubMed1987

The relationship between nasal cross-sectional area and nasal air volume in normal and nasally impaired adults.

The controversy concerning the effects of nasal airway impairment on facial growth has stimulated renewed interest in upper airway respiratory function. The subjective manner in which airway impairment and mouth breathing have been assessed is, in our opinion, responsible for the differences observed among investigators and for their conclusions. We have been involved in a series of studies dealing with airway impairment and have report modifications of two techniques for objectively assessing respiration. The purpose of the present study was to examine a large population of adults, with and without nasal airway impairment, and assess the relationship between nasal cross-sectional area and nasal air volume to determine at what point airway size controls the passage of air during breathing. Statistical analysis of the data demonstrates that airway size alters air volume when nasal cross-sectional area is less than 0.4 cm2. The relationship between area and volume is very linear below 0.4 cm2, with air volume decreasing with decreased size. Although the data do indicate some influence over volume at sizes greater than 0.4 cm2, the effect is very slight. These findings support the prediction that upper airway impairment is present at nasal airways less than 0.4 cm2 in adults.

Adolescent↗
PubMed1986

Tuberculous empyema--a case history extending over 30 years.

A patient with chronic tuberculous empyema is described. The condition had been present for 30 years, following treatment by outpatient pneumothorax. A broncho-pleural fistula developed, the symptoms of which were aggravated during air-flight.

Bronchial Fistula↗
PubMed1980

Respiratory disability in coal miners.

It has been suggested that the assessment of ventilatory capacity alone is inadequate for the determination of disabling occupational respiratory impairment in coal miners. The Department of Labor has accepted this view and now routinely requests blood gas analyses in those claimants not meeting the ventilatory criteria. We tested the validity of this contention by selecting two groups of coal miners claiming total disability. The first consisted of 150 claimants who were referred for spirometry, while the second consisted of 50 claimants who had been referred for blood gas studies. Of those in group 1, eight met the extent criteria for disability, while only two of those in group 2 satisfied the criteria, and, in both, cardiac disease was responsible. We conclude that blood gas analyses are unnecessary in the determination of pulmonary disability in coal miners.

Blood Gas Analysis↗
PubMed1979

Late sequelae of paralytic poliomyelitis: a clinical and electromyographic study.

A prospective study was carried out on 24 volunteers who had suffered from paralytic poliomyelitis up to 51 years earlier. A quantitative EMG was carried out in each subject. Grossly raised mean amplitudes of the interference patterns were found in many strong muscles as well as in weak muscles. Such muscles frequently showed "contraction fasciculation", a manifestation of loss of normal small motor units. In many subjects the clinical and EMG evidence of chronic partial denervation were more widespread than the subjects had realised. It is suggested that if, with advancing age, minor damage occurs to the peripheral nervous system and the complement of motor neurones is already depleted by poliomyelitis, there will be an exaggerated response with increase in the lower motor neurone signs.

Adult↗