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Biomedical subjects

M Desmeules

Publications and source records attributed to M Desmeules.

12 recordsLinked to original sources
PubMed1992

Increasing incidence of primary malignant brain tumors: influence of diagnostic methods.

BACKGROUND: The incidence of brain cancer has increased dramatically over the last decades in most developed countries. Whether these trends can be attributed to improved diagnosis is not clear. PURPOSE: To determine the effect of new imaging technology on increased rates of brain cancer, we assessed the level of detection for neurological disorders when computed tomography (CT) and magnetic resonance imaging (MRI) results were not available. METHODS: A neurologist performed a blind review of hospital charts from 356 randomly selected patients, hospitalized between 1985 and 1989 for neurological disorders, including brain cancer. All prediagnosis information except CT and MRI results was used as a basis for diagnostic re-evaluation. Also, a random sample of 151 brain cancer patients diagnosed between 1960 and 1965 was selected for a description of diagnostic methods used during that period. RESULTS: A comparison between the original diagnoses and the re-evaluations for patients in the 1985-1989 sample indicated that there was, among the diseases selected, a 24% misclassification when CT scans and MRI were not available. In particular, 20% of brain tumors were undetected (95% confidence interval = 15%-25%), and 10% of non-tumor disorders were inaccurately labeled as brain tumors in the absence of these tests. The repeatability of the re-evaluations was 86%. CONCLUSIONS: Among elderly North Americans, at least twofold increases in brain cancer incidence were observed over the last two decades. Since our findings show that CT scans and MRI are responsible for the detection of about 20% of brain tumors, we conclude that other factors also are responsible for the observed trends.

Adolescent↗
PubMed1992

Work-related mesothelioma in Québec, 1967-1990.

Prior surveys of malignant mesothelioma in Québec have noted that almost all the excess in occupational exposure related mesothelioma was in the manufacture and industrial application of asbestos rather than in the mining and milling operations. To evaluate the current status of malignant pleural mesothelioma in the Québec workforce, we reviewed all cases of pleural mesothelioma seen and accepted by the Québec Workman's Compensation Board (CSST) for work related compensation of industrial disease. We identified 120 cases, 7 of whom were females. They were of an average age of 59 +/- 8.5 yrs (sd) (range 42-84); they were exposed to asbestos dust in the workplace for an average of 26 +/- 14.3 yrs (range 0.5-50). The cases were subdivided into 3 groups according to workplace asbestos exposures. There were 49 cases originating in the mines and mills of the Québec Eastern Township region (primary industry, group 1), 50 cases from the manufacture and industrial application sector (secondary industry, group 2), and 21 cases from industries where asbestos was not a major work material, often an "incidental" material (tertiary industry, group 3). Group 1 was of an average age of 62 +/- 8 years, exposed to asbestos dust 31 +/- 14 years and the distribution of exposure time was as follows: 15% cases with < or = 10 year-exposure and 77% > or = 25 year-exposure. In group 2, the age was significantly lower at 57 +/- 9 years; the exposure time was also significantly lower at 22 +/- 14 years, and the distribution of exposure time differed from the above (29% cases with < or = 10 year-exposure and 48% > or = 25 year-exposure). In group 3, the average age was 58 +/- 7 years, the exposure time was also significantly lower at 28 +/- 12 years and the distribution of exposure time differed from the above (33% cases with < or = 10 year-exposure and 62% > or = 25 year-exposure). Analyses of the yearly incidence of new cases in each group documented the general incremental trend in all groups, with the sharpest rises in group 3. In the mining towns of Thetford and Asbestos, the incidence of mesothelioma was proportional to the workforce, thus suggesting that the tremolite air contamination, which is 7.5 x higher in Thetford, may not be a significant determinant of the disease in these workers.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Mechanisms of the effectiveness of continuous positive airway pressure in obstructive sleep apnea.

Nasal continuous positive airway pressure (NCPAP) is considered the most effective treatment of obstructive sleep apnea. Its beneficial effects are related to the normalization of breathing during sleep and to the prevention of nocturnal desaturations. NCPAP interacts with the pathophysiologic mechanisms of sleep apnea onset and with the consequences of these apneas. Upper airway patency is maintained with NCPAP by a pneumatic splinting effect while changes in lung volume and pre-apnea SaO2 level may be implicated in the improvement of apnea-related desaturations. An improvement in central chemosensitivity could account for the improvement in diurnal oxygenation observed with long term NCPAP therapy.

Airway Resistance↗
PubMed1991

Increasing brain cancer rates in Canada.

OBJECTIVE: To analyse brain cancer patterns in Canada, particularly according to age and sex distributions, temporal patterns and regional variations. Changes in diagnostic techniques, survival rates and trends by tumour type were also examined. DESIGN: Descriptive epidemiologic study based on Canada-wide population data for 1959-88. OUTCOME MEASURES: Rates of death, incidence and admission to hospital because of brain cancer, as well as survival time and methods of diagnosis. SUBJECTS: Incidence and death rates and time trends were examined for Canada as a whole, by province and by census division. RESULTS: The rates of death from brain cancer increased rapidly among Canadians aged 55 years or more from 1959 to 1988. In particular, age-adjusted death rates increased by 117%, 797% and 118% among men 65 to 74 years, 75 to 84 and 85 or more respectively. The corresponding increases among women were 138%, 535% and 400%. The incidence rates also increased substantially. The trends in incidence rates by tumour type indicated that the increase was more pronounced for glioblastomas. The incidence rates of cases detected histologically, radiologically and clinically all increased. CONCLUSIONS: Because glioblastomas are generally easier to diagnose than astrocytomas and because the incidence rates of glioblastomas were found to increase substantially, the increased brain cancer rates among elderly people may not be entirely attributable to improved diagnostic techniques. However, analytic investigations of the impact of changes in diagnostic procedures on brain cancer trends are needed to clarify this issue.

Adolescent↗
PubMed1990

Alcohol and the response of upper airway resistance to a changing respiratory drive in normal man.

We studied the effects of alcohol ingestion on the response of upper airway resistance (UAR) to changing respiratory motor output in 9 normal subjects. Nasal and pharyngeal pressures were measured with two low bias flow catheters placed at the tip of the epiglottis and in the posterior nasopharynx. Respiratory flow was measured with a Fleisch no. 3 pneumotachograph connected to a tightly fitting mask. Breath-by-breath inspiratory upper airway resistances were calculated at isoflow during 1) a CO2 rebreathing (increase in drive), 2) 2 min following five slow vital capacities of 100% O2 (decrease in drive) (Post-O2 period), and 3) 1 min before each procedure (baseline measurements). The respiratory motor output was estimated by the pressure developed 0.1 sec after the onset of inspiration (P0.1) during rebreathing and by the mean inspiratory flow (VT/TI) during the post-O2 period. Measurements were performed before and after the ingestion of 1.5 ml/kg of 40% alcohol. Blood alcohol level rose from 0 to 14.9 +/- 1.8 mmol.L-1 (Mean +/- SD) and total supralaryngeal resistance increased from 2.8 +/- 1.8 cm H2O.L-1.sec to 4.2 +/- 1.8 cm H2O.L-1.sec (P less than 0.001, Student's paired t-test). During CO2 rebreathing UAR decreased exponentially as P0.1 increased both before and after alcohol intake. The slope of the plot Log (pharyngeal resistance) against P0.1 decreased from -17.0 x 10(-3) +/- 9.3 x 10(-3) before alcohol to -11.0 x 10(-3) +/- 6.6 x 10(-3) after alcohol intake (P = 0.03). The slope of the decrease in nasal resistance remained unchanged. A decrease in VT/TI occurred during the Post-O2 period and was accompanied by an exponential increase in UAR at each experiment. The slope of Log (pharyngeal resistance) over VT/TI was significantly higher after (-27.0 x 10(-3) +/- 7.1 x 10(-3)) than before alcohol (-12.0 x 10(-3) +/- 4.2 x 10(-3), P less than 0.001). The slope of the increase in nasal resistance with decreasing VT/TI rose from -8.4 x 10(-3) +/- 6.5 x 10(-3) to -13.0 x 10(-3) +/- 7.4 x 10(-3) after alcohol ingestion (P = 0.06). We conclude that alcohol ingestion depresses the pharyngeal responses to changing central drive in normal subjects.

Adult↗
PubMed1990

Changes in upper airway resistance with lung inflation and positive airway pressure.

The influence of pulmonary inflation and positive airway pressure on nasal and pharyngeal resistance were studied in 10 normal subjects lying in an iron lung. Upper airway pressures were measured with two low-bias flow catheters while the subjects breathed by the nose through a Fleish no. 3 pneumotachograph into a spirometer. Resistances were calculated at isoflow rates in four different conditions: exclusive pulmonary inflation, achieved by applying a negative extra-thoracic pressure (NEP); expiratory positive airway pressure (EPAP), which was created by immersion of the expiratory line; continuous positive airway pressure (CPAP), realized by loading the bell of the spirometer; and CPAP without pulmonary inflation by simultaneously applying the same positive extrathoracic pressure (CPAP + PEP). Resistance measurements were obtained at 5- and 10-cmH2O pressure levels. Pharyngeal resistance (Rph) significantly decreased during each measurement; the decreases in nasal resistance were only significant with CPAP and CPAP + PEP; the deepest fall in Rph occurred with CPAP. It reached 70.8 +/- 5.5 and 54.8 +/- 6.5% (SE) of base-line values at 5 and 10 cmH2O, respectively. The changes in lung volume recorded with CPAP + PEP ranged from -180 to 120 ml at 5 cmH2O and from -240 to 120 ml at 10 cmH2O. Resistances tended to increase with CPAP + PEP compared with CPAP values, but these changes were not significant (Rph = 75.9 +/- 6.1 and 59.9 +/- 6.6% at 5 and 10 cmH2O of CPAP + PEP). We conclude that 1) the upper airway patency increases during pulmonary inflation, 2) the main effect of CPAP is related to pneumatic splinting, and 3) pulmonary inflation contributes little to the decrease in upper airways resistance observed with CPAP.

Adult↗
PubMed1990

Influence of passive changes of lung volume on upper airways.

The total upper airway resistances are modified during active changes in lung volume. We studied nine normal subjects to assess the influence of passive thoracopulmonary inflation and deflation on nasal and pharyngeal resistances. With the subjects lying in an iron lung, lung volumes were changed by application of an extrathoracic pressure (Pet) from 0 to 20 (+Pet) or -20 cmH2O (-Pet) in 5-cmH2O steps. Upper airway pressures were measured with two low-bias flow catheters, one at the tip of the epiglottis and the other in the posterior nasopharynx. Breath-by-breath resistance measurements were made at an inspiratory flow rate of 300 ml/s at each Pet step. Total upper airway, nasal, and pharyngeal resistances increased with +Pet [i.e., nasal resistance = 139.6 +/- 14.4% (SE) of base-line and pharyngeal resistances = 189.7 +/- 21.1% at 10 cmH2O of +Pet]. During -Pet there were no significant changes in nasal resistance, whereas pharyngeal resistance decreased significantly (pharyngeal resistance = 73.4 +/- 7.4% at -10 cmH2O). We conclude that upper airway resistance, particularly the pharyngeal resistance, is influenced by passive changes in lung volumes, especially pulmonary deflation.

Adult↗
PubMed1989

Influence of respiratory drive on upper airway resistance in normal men.

The variations in nasal and pharyngeal resistance induced by changes in the central inspiratory drive were studied in 10 normal men. To calculate resistances we measured upper airway pressures with two low-bias flow catheters; one was placed at the tip of the epiglottis and the other in the posterior nasopharynx, and we measured flow with a Fleisch no. 3 pneumotachograph connected to a tightly fitting mask. Both resistances were obtained continuously during CO2 rebreathing (Read's method) and during the 2 min after a 1-min voluntary maximal hyperventilation. The inspiratory drive was estimated by measurements of inspiratory pressure generated at 0.1 s after the onset of inspiration (P0.1) and by the mean inspiratory flow (VT/TI). In each subject both resistances decreased during CO2 rebreathing; these decreases were correlated with the increase in P0.1. During the posthyperventilation period, ventilation fell below base line in seven subjects; this was accompanied by an increase in both nasal and pharyngeal resistances. These resistances increased exponentially as VT/TI decreased. Parallel changes in nasal and pharyngeal resistances were seen during CO2 stimulus and during the period after the hyperventilation. We conclude that 1) the indexes quantifying the inspiratory drive reflect the activation of nasopharyngeal dilator muscles (as assessed by the changes in upper airway resistance) and 2) both nasal and pharyngeal resistances are similarly influenced by changes in the respiratory drive.

Adult↗
PubMed1976

Tracheobronchopathia osteochondroplastica.

Tracheobronchopathia osteochondroplastica is a rare disorder characterized by the projection of ossified formations into the trachea and bronchi. Unlike most cases, which are reported because of incidential postmortem findings, our patient presented with a slowly resolving pneumonia. The diagnosis was suspected by radiographic evaluation and bronchoscopic findings, then confirmed by histopathologic studis of a tracheal biopsy specimen. Pulmonary function studies were normal, except for flow-volume loops, which provided information for diagnosis and follow-up.

Aged↗
PubMed1975

The effect of lobar obstruction on regional perfusion in the intact dog.

The effect of acute obstruction of the right lower lobes (RLL) on the relative perfusion of different lung regions was studied using Xenon-133 in anesthetized artificially ventilated supine dogs. When the RLL were obstructed at functional residual capacity (FRC) and the rest of the lung was inflated to a transpulmonary pressure of 10 or 20 cm H2O (1 cm H2O = 94.1 N/m2), relative perfusion increased within 10 s to the obstructed lobes by 59 and 92%, respectively. The increase was less marked but still present (17 and 42%, respectively) when obstruction was maintained for 15 min, at a time when arterial hypoxemia had occurred. Hence, there was increased perfusion to an obstructed hypoxic region. The perfusion distribution correlated with the difference in alveolar pressure between the obstructed lobes and the unobstructed lobes such that relative perfusion was always increased to the low alveolar pressure region.

Animals↗