Biomedical subjects

F Bellemare

Publications and source records attributed to F Bellemare.

At least 19 recordsLinked to original sources

PubMed2006

Sex differences in thoracic adaptation to pulmonary hyperinflation in cystic fibrosis.

Sex differences in thoracic adaptation have been reported in patients with cystic fibrosis (CF). The interplay between the pattern of thoracic adaptation and the function of the respiratory muscles in male and female CF patients with pulmonary hyperinflation was investigated. Thoracic dimensions and diaphragm length were measured at residual volume, functional residual capacity and total lung capacity using chest radiography in 23 CF (12 males) and 18 normal (11 males) subjects. Respiratory muscle recruitment during resting breathing was assessed by recording intrathoracic and intra-abdominal pressures. In female CF patients, ribcage expansion was predominant, tending to preserve diaphragm length. In male CF patients, thoracic configuration was normal and diaphragm shortening consequently greater. Ribcage cross-sectional area for a given rib inclination was greater in CF patients, indicating a structural expansion of the ribcage 2.5 times greater in females than males. The contribution of inspiratory ribcage muscles to inspiratory pressure was also greater relative to the diaphragm in the CF group. In conclusion, a structural expansion of the ribcage occurs in cystic fibrosis patients with lung hyperinflation that is greater in females than males. This is associated with an apparent greater contribution of inspiratory ribcage muscles to inspiratory pressure.

Adaptation, Physiological↗

PubMed2001

Thoracic dimensions at maximum lung inflation in normal subjects and in patients with obstructive and restrictive lung diseases.

OBJECTIVES: To compare the distribution of lung volume at total lung capacity (TLC) among adult men and women known to have normal lung function or chronic obstructive disease or restrictive lung disease (RLD). DESIGN: Five-year retrospective study. SETTING: Review of available clinical pulmonary function testing (PFT) reports and chest radiographs. PATIENTS: Sixty-four patients presenting with normal PFT and chest radiograph findings (normal subjects), 26 patients with severe COPD and increased TLC (COPD group), 29 patients with cystic fibrosis (CF) and increased TLC (CF group), and 19 patients with RLD with a clinical diagnosis of pulmonary fibrosis and a reduced TLC (RLD group). MEASUREMENTS: Average posteroanterior rib cage diameter (PAave), average lateral rib cage diameter (LAave), and average vertical height of the diaphragm (HDIave) were measured using radiography. Normal prediction equations were generated based on stature, body mass index (BMI), age, and sex as independent variables and then used in between-group comparisons. RESULTS: PAave correlated positively with BMI and age but not with height, whereas LAave correlated positively with BMI and height but not with age. HDIave correlated positively with height and age but negatively with BMI. PAave and LAave were smaller and HDIave was greater in women than men having the same stature. In the COPD group and in male CF group patients, BMI was low and only HDIave was greater than in sex-, age-, and height-matched normal subjects, but in female CF group patients, only the rib cage diameters were greater than normal. In the RLD group, PAave and HDIave were smaller than predicted and inversely related to each other, but LAave was normal. CONCLUSION: Variations in maximum lung volume caused by gender, growth, or by lung diseases are nonisotropic and entail substantial changes in chest wall shape.

Adult↗

PubMed2001

Anatomic landmarks to estimate the length of the diaphragm from chest radiographs: effects of emphysema and lung volume reduction surgery.

STUDY OBJECTIVES: To define anatomic landmarks that can be used to predict insertions of the diaphragm on chest radiographs and to estimate diaphragm length. DESIGN: Prospective clinical trial with a parallel group design. SETTING: Laboratory investigations in normal volunteers recruited by advertisement and in emphysema outpatients being evaluated for elective bilateral lung volume reduction surgery (LVRS). PATIENTS: Twenty-six normal subjects classified into young and older age groups, with a third group of 13 emphysema patients matched for age and sex with the older group. MEASUREMENTS: Identification and between-group comparisons were made of anatomic landmarks on anteroposterior and lateral chest radiographs obtained at total lung capacity. Predicted landmarks were generated from normal subjects. Within-subject and between-group comparisons were made of diaphragm length index (DLI) based on observed anatomic landmarks (DLIobs) and diaphragm length index based on predicted anatomic landmarks (DLIpred) at functional residual capacity. RESULTS: Anatomic landmarks were not different between the three groups or between male and female subjects, and were not different before and after LVRS in emphysema patients. No difference was found between DLIobs and DLIpred in normal subjects and emphysema patients, but both were smaller in emphysema patients than in normal subjects and increased after LVRS in emphysema patients. CONCLUSION: This study validates the use of anatomic landmarks to estimate DLI. Using these landmarks simplifies the determination of diaphragmatic lengths and could be a useful tool for the evaluation of the functional capacity of the diaphragm, and possibly as a prognostic indicator of patients who are candidates for LVRS.

Adult↗

PubMed2000

Temporal relation between acoustic and force responses at the adductor pollicis during nondepolarizing neuromuscular block.

BACKGROUND: Contracting muscle emits sounds. The purpose of this study was to compare the time course of muscular paralysis at the adductor pollicis muscle (AP) with use of acoustic myography and mechanomyography. METHODS: Thirteen elective surgery patients, American Society of Anesthesiologists physical status I, received rocuronium (0.6 mg/kg intravenously) as a bolus dose during general anesthesia. Force of AP was measured with use of a strain gauge, and sounds were recorded simultaneously with use of a small condenser microphone fixed on the palmar surface of the hand over the AP. Supramaximal stimulation was applied to the ulnar nerve at 0.1 Hz for 45-60 min. In seven patients, the response to train-of-four stimulation was also recorded during recovery. RESULTS: Force and sounds both were equally sensitive in measuring maximum block. The relation between sound and force was curvilinear, with good agreement near 0 and 100% and acoustic response exceeding mechanical response at intermediate levels of block. The acoustic signal had a slower onset and a faster recovery than the force response. The fade response of sound to train-of-four stimulation also recovered faster than that of force. CONCLUSION: Acoustic myography is an alternative method to monitor muscular paralysis that is easy to set up and applicable to most superficial muscles. However, the time course of relaxation at AP using acoustic myography differs from the time course of force relaxation. Therefore, these two methods are not equivalent when applied to AP.

Adult↗

PubMed1999

Influence of abdomen on respiratory mechanics in supine rabbits.

Previous studies showed that abdominal evisceration has no effect on respiratory system compliance. We hypothesized that this could be related to lung distortion in eviscerated animals. Methods were developed for continuous recording of pleural pressure (Ppl) at various sites over the costal (co) and diaphragmatic lung surface (di) in acutely and chronically instrumented rabbits. We compared deltaPpl,co and deltaPpl,di recorded at mid-lung height during inflations in anesthetized, paralyzed supine rabbits before and after evisceration. Cranial and caudal deltaPpl.co were the same under all conditions. In intact animals, deltaPpl.co and deltaPpl,di were equal at all inflation volumes, whilst in eviscerated animals, deltaPpl,di were smaller than deltaPpl,co, the difference increasing with lung inflation. At any given volume, rib cage circumference (Crc) was smaller after evisceration, but the Crc deltaPpl,co relationship remained unchanged. These results are indicative of non-uniform lung expansion after evisceration and are consistent with model predictions based on cylindrical deformation and lung stress-strain relationship. This deformation should mimic the effect of a reduced lung compliance, keeping respiratory system compliance of eviscerated animals nearly normal. Similar deformation should have occurred also in intact rabbits during strong inspiratory efforts and in the erect posture, because lower Ppl,di than Ppl,co values were observed at the same lung height under these conditions.

Abdomen↗

PubMed1999

In normal subjects bracing impairs the function of the inspiratory muscles.

Normal subjects can increase their capacity to sustain hyperpnoea by bracing their arms on fixed objects, a procedure which is also known to reduce dyspnoea in patients with chronic obstructive pulmonary disease (COPD). In the present study, it was tested whether bracing per se could improve the function of the diaphragm. The effect of bracing on diaphragm function was studied in six normal subjects by recording changes in oesophageal (delta Poes) and transdiaphragmatic (delta Pdi) pressure during inspiratory capacity (IC) manoeuvres in the seated and upright postures, and in the seated posture, also during bilateral phrenic nerve stimulation (BPNS) at functional residual capacity (FRC). The pattern of ribcage motion and deformation associated with bracing and with diaphragm contraction was also evaluated using inductance plethysmography and magnetometers. Bracing increased FRC by >300 mL and reduced IC by approximately 200 mL, in both postures. Delta Pdi during BPNS decreased on average by 15% indicating an impaired diaphragmatic function. The ribcage was deformed with bracing and was more distortable during BPNS. In conclusion, in normal subjects, bracing impairs the function of the inspiratory muscles and reduces ribcage stability. These negative effects cannot explain the improved capacity to sustain hyperpnoea when the arms are braced.

Adult↗

PubMed1997

Can we treat respiratory failure in Friedreich ataxia?

BACKGROUND: Neurochemical disorders associated with spinocerebellar ataxias are multiple. OBJECTIVE: To use replacement and neuroprotective therapy in a case of severe respiratory failure in Friedreich ataxia. PATIENT AND TREATMENT: A 44-year-old man with severe Friedreich ataxia displayed arduous periodic breathing associated with minor desaturation as well as obstructive or mixed apneas associated with severe desaturation during the night. He was given oxitriptan (5-hydroxy-L-tryptophan) (1500 mg/d), thiamine hydrochloride (100 mg/d), and amantadine hydrochloride (100 mg/d). The first sleep study was conducted during the night before treatment, whereas the second was performed during the night after 9 months of treatment. RESULTS: After treatment, striking clinical improvement of spastic dysphonia was accompanied by significant diminution in the time spent in periodic breathing and in the number of obstructive and mixed apneas during the night. Controlled studies are needed.

5-Hydroxytryptophan↗

PubMed1997

Time and frequency domain analysis of acoustic signals from a human muscle.

We wished to determine whether evoked force output from a human muscle could be inferred from the amplitude and the frequency of evoked muscular sounds. Sounds from adductor pollicis were recorded with a microphone and compared to evoked force changes produced by varying the intensity of nerve stimulation or of voluntary effort as well as by fatigue and twitch potentiation. In all instances, high correlations were obtained between evoked acoustic signals amplitude and evoked twitch force changes. Instantaneous time-frequency distributions of evoked acoustic signals also showed a high degree of cross correlation with evoked instantaneous twitch force, but no relationship was found for the group between the maximal frequency of sound and force changes. We conclude that evoked force changes from human muscles cannot be reliably inferred from frequency domain analysis of evoked sound signals and that, for this purpose, analysis of sound signals in time domain can be employed, an analysis potentially useful for muscles whose force output cannot be directly measured.

Adult↗

PubMed1997

Time-frequency analysis of the muscle sound of the human diaphragm.

The time-frequency characteristics of muscular sounds (phonomyogram) produced by the contraction of the human diaphragm under various contractile states is evaluated with the cone-kernel distribution. The results show that the instantaneous frequency of the phonomyogram of the diaphragm has a high cross-correlation (an average of 0.91 +/- 0.06) with the transdiaphragmatic pressure, with a delay varying between 25 and 35 ms. The instantaneous frequency response of the phonomyogram of the diaphragm shows a behaviour similar to that of the frog muscle; it rapidly rises and then fades out. However, the maximum of the instantaneous frequency of the phonomyogram of the diaphragm is not proportional to the maximum of the transdiaphragmatic pressure. This analysis also demonstrates the usefulness of the cone-kernel distribution for studying frequency-modulated signals like the muscular sound signals.

Diaphragm↗

PubMed1997

Diaphragmatic fatigue investigated by phonomyography.

Diaphragmatic phonomyogram (PMG) evoked by maximal bilateral phrenic nerve stimulation has previously been described as a good index of contractility of fresh and fatigued diaphragm. In the present study we hypothesized that diaphragmatic contractility changes could be even more simply evaluated by recording the relationship between the PMG and the compound motor action potential (CMAP) amplitudes during graded submaximal unilateral phrenic nerve stimulation at various intensities. Relationships between CMAPs and PMGs from left and right hemidiaphragms were recorded by means of surface electrodes and miniature microphones placed over the lower rib cage (eighth intercostal space) in five healthy subjects before and after a diaphragmatic fatigue task. These relationships in each subject were linear. The slope of these relationships decreased by 61.1 +/- 20.7% and by 70.4 +/- 14.6% on the right and left side respectively, but the intercepts did not change significantly. By comparison, transdiaphragmatic twitch pressure during maximal bilateral stimulation (PdiT) declined by 49.4 +/- 15%. We conclude that PMG during submaximal unilateral phrenic nerve stimulation is a reliable index of diaphragm contractility changes caused by fatigue. Using this method we have shown that all diaphragmatic motor units can be affected by fatigue.

Action Potentials↗

PubMed1997

Modulation of noninduced and phorbol ester-induced generation of superoxide anion by free liposomes and liposomes containing dexamethasone.

We tested the relative efficacy of free dexamethasone, dexamethasone containing liposomes and free liposomes in preventing superoxide anion, O-2 generation by neutrophils. O-2 production by 5 x 10(5) neutrophils, whether primed or not with lipopolysaccharide, was stimulated by phorbol 12-myristate 13-acetate (PMA) to 13.4 +/- 1.3 nmoles after 15 minutes compared to 1.2 +/- 0.3 nmoles with nonstimulated cells. Free liposomes but not dexamethasone (dexa) decreased non-stimulated as well as PMA-induced O-2 generation. Dexa-containing phosphatidylcholine from egg yolk: phosphatidylserine from bovine brain (PC:PS 7:3) liposomes, unlike free dexa, diminished PMA-stimulated O-2 production in a dose-dependent manner with a maximal effect at 37.5 micrograms/ml phospholipid (6.6 +/- 1.6 nmoles). The kinetics of cytochrome-c reduction revealed that decreased O-2 production resulted from an extended lag-time of release to almost 8 minutes with PMA induction and consequently led to the conclusion that liposomes modified the activity of NADPH oxidase as well as that of protein kinase C. Liposomes prepared with PC and PS of natural origin had a greater inhibitory effect on O-2 generation by neutrophils than dipalmitoylphosphatidylcholine (DPPC) and phosphatidylethanolamine from egg yolk (PE):PC (3:1) liposomes. When 100 microM of Ca2+ was added to the medium, the inhibitory action of liposomes prepared with egg yolK PC and DPPC was increased by 30 and 60% respectively, while that of PS and PE:PC was prevented. We also verified that liposomes by themselves, even if phagocytized, did not induce O-2 generation or its concentration was too low to be detected by this technique. From the clinical point of view, some formulations delayed non-induced and PMA-induced O-2 generation, thus adding to the anti-inflammatory effect of the glucocorticoid they transported.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1996

Insertional action of the abdominal muscles in rabbits and dogs.

The insertional action of the abdominal muscles was studied in supine anesthetized, apneic rabbits and dogs by comparing the changes in esophageal pressure (Pes), upper and lower rib cage circumference (Cru,u and Crc,I) and lung volume (VL) in response to electrical stimulation of all abdominal muscles before and after evisceration. In eviscerated animals, abdominal muscle contraction increased Pes and decreased both VL and Cre,I, but had no effect on Crc,u. Maximal responses were obtained at submaximal intensities of stimulation, and became larger with increasing lung volume. Relative to the vital capacity in intact animals, maximal delta VL for stimulation performed at FRC and TLC were 7.2 +/- 2.9(SD) and 39.5 +/- 7% in rabbits, and 6.3 +/- 0.8 and 18.3 +/- 5.9% in dogs, respectively. Relative to the changes in lung volume occurring with maximal contraction of the abdominal muscles in intact animals, the values of delta VL observed in the eviscerated animals amounted to approximately 35 and approximately 45% for stimulation performed at FRC and TLC, respectively. Hence, abdominal muscles exert substantial insertional action on the lower rib cage that can result in appreciable lung deflationary effects, particularly at elevated lung volumes.

Abdominal Muscles↗

PubMed1996

Effects of lung volume and fatigue on evoked diaphragmatic phonomyogram in normal subjects.

BACKGROUND: A diaphragmatic phonomyogram (PMG) evoked by maximal phrenic nerve stimulation at end expiratory lung volume (FRC) has been previously described as a good index of changes in diaphragmatic contractility with fatigue. A study was undertaken to assess whether this conclusion could be extended to different lung volumes. METHODS: Diaphragmatic compound motor action potentials (CMAPs) were recorded on each side of the chest by the means of surface electrodes placed over the eight intercostal spaces in five healthy subjects. Diaphragmatic PMGs from both sides were recorded with condenser microphones fixed to the skin close to the CMAP recording electrodes. Oesophageal and gastric balloon tipped catheters were employed to measure transdiaphragmatic pressure twitches (TwPDI) which served as the standard measure of changes in diaphragmatic contractility. PMG and TwPDI responses were compared at different lung volumes over inspiratory capacity both before and after fatiguing inspiratory resistive loading. RESULTS: No consistent relationship was found in different subjects or on different days in the same subject between PMG and lung volume or between PMG and TwPDI. However, the PMG:CMAP ratio from both sides at any given lung volume decreased after fatigue in roughly the same proportion as the TwPDI. CONCLUSIONS: These results show that, although PMG can detect changes in diaphragmatic contractility caused by fatigue in normal subjects, lung volume changes need to be controlled and each subject should serve as his or her own control.

Action Potentials↗

PubMed1996

Evidence from incorporation and patch-clamp experiments for a nonselective channel of large conductance at the luminal membrane of rabbit proximal tubule.

The presence of nonselective ionic channels at the apical membrane of rabbit proximal tubule cells was investigated by fusion of proximal tubule brush border membrane vesicles onto a planar bilayer and by means of patch clamp measurements on primary cultured proximal tubule cells. The fusion of brush border membrane vesicles onto a phosphatidylethanolamine-phosphatidylcholine (1:1) planar bilayer led to the identification of a nonselective channel of 115 pS in 200 mM NaCl conditions with an ionic permeability sequence for Na+, K+, and Cl- corresponding to PNa/PK = 0.3 and PNa/PCl = 3, respectively. This channel showed an increased open probability at depolarizing potentials, but its activity was independent of the Ca2+ concentration in both the cis and trans compartments. These findings were subsequently confirmed in inside-out patch clamp experiments carried out on primary cultured proximal tubule cells. This channel was seldom seen in cell-attached recordings on resting cells, but its presence was observed with a higher probability in patch excised experiments performed following superfusion of the cells with a hypotonic solution. It is suggested on the basis of these observations that the apical membrane of rabbit proximal tubule cells contains a voltage-dependent nonselective channel, the activity of which may contribute to the regulation of the membrane potential.

Animals↗

PubMed1995

Respiratory muscle fatigue.

Ventilatory failure may accompany a variety of pulmonary and neuromuscular diseases. There has been much controversy about whether this failure is due to respiratory muscle fatigue at peripheral sites or a failure of drive at sites within the central nervous system. The chapter reviews this topic.

Animals↗

PubMed1995

PC:PS liposomes induce a recruitment of neutrophils and the release of TNF alpha in the lungs of mice sensitized with Saccharopolyspora rectivirgula.

The aim of this study was to verify the effect of nasally instilled liposomes (L) or dexamethasone-containing L (Ldexa) on normal or inflamed lung tissue. Three groups of mice were studied. Group I was given saline instillations for 3 weeks prior to the instillation with liposomes. In groups II and III lung inflammation was induced by repeated instillations of Saccharopolyspora rectivirgula before the instillation of liposomes (group II) or liposomes containing dexamethasone (group III). Animals from all groups were killed at regular time intervals for up to 48 h after the instillation of liposomes. The total cell count in bronchoalveolar lavage fluid did not differ significantly between groups I and II. However, in group III it decreased rapidly from 6.2 to 2.8 x 10(5) cells mL-1 within 2 h. Differential counts did not change in group I, but in group II a transient neutrophilia was observed 180 min after the instillation of liposomes. In group III, the instillation of dexamethasone-containing liposomes depleted all neutrophils and lymphocytes after 4 h. No TNF alpha was found in samples of lavage fluid from any of the groups at time 0. In group I, liposomes induced the production of 0.03 ng mL-1 of TNF alpha in the 1 h sample only. In group II, TNF alpha peaked to 1 ng mL-1 at 1 h and had decreased to 0.35 ng mL-1 by 3 h. In group III, TNF alpha peaked at 1 h, but only reached a level of 0.1 ng mL-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Intranasal↗

PubMed1994

Phonomyogram of the diaphragm during unilateral and bilateral phrenic nerve stimulation and changes with fatigue.

As previously demonstrated in humans, contracting skeletal muscles vibrate laterally and generate sound. The amplitude of this acoustic signal, called the phonomyogram (PMG), is related to muscle force production. As in limb muscles, the diaphragm might produce mechanical tissue vibrations and a PMG. We recorded diaphragm twitches during phrenic nerve stimulation in normal subjects at FRC. Diaphragmatic compound motor action potentials (CMAP) were recorded on each side of the chest by surface electrodes over the eighth intercostal space. Condenser microphones were fixed to the skin close to the electrodes, and esophageal and gastric balloons employed to measure transdiaphragmatic pressure (Pdi). For unilateral and bilateral supramaximal single shocks (0.1 ms), PMG onset latencies from either side (12.4 +/- 0.6 ms) were intermediate between those of CMAP (7.3 +/- 0.7 ms) and of Pdi (20.3 +/- 2.8 ms). By varying stimulation intensity, significant linear relationships were obtained between CMAP and PMG amplitudes on each side. A significant linear relationship was also found between PMG for each side and Pdi peak values. PMG and Pdi both decreased with fatigue of the diaphragm. We conclude that PMG in response to single phrenic nerve shocks is a noninvasive index of electromechanical coupling, recruitment, and transdiaphragmatic pressure generation by the diaphragm.

Action Potentials↗

PubMed1994

Mechanics of the abdominal muscles in rabbits and dogs.

In anesthetized, apneic rabbits and dogs, direct tetanic stimulations of the abdominal muscles (AMS) were performed at different tracheal pressures (Ptr) in the supine and upright posture. Lung volume (V), esophageal (Pes) and abdominal pressure (Pab), circumference of the upper and lower lung apposed rib cage (Crc, u and Crc, l) and of the abdomen (Cab), and transverse diameter of the rib cage facing the abdominal contents (Drc,ab) were measured. At Ptr = 0, Pab and Pes increased, and V decreased with increasing the strength of AMS; delta Pes and delta V eventually levelled off, while delta Pab was still increasing. Both delta Pes and delta V were larger in the upright posture, whereas delta Pab were similar. Relative to the expiratory reserve volume (ERV), maximal delta V in the supine and upright posture were 75.6 +/- 2.1 (mean +/- SE) and 86.1 +/- 2.2% in rabbits, and 56.5 +/- 3.4 and 75.2 +/- 3.7% in dogs. Maximal AMS decreased V and increased delta Pab the more so the larger the lung volume. In the volume range 10-70% VC, delta V were 3-4% VC larger in the upright posture, while delta Pab were similar in both postures. With AMS, Cab decreased, and Crc,u and Crc,l increased, while Drc,ab increased in dogs and decreased in rabbits. Hence, (a) the abdominal muscles can account for most of the ERV, particularly in the upright posture; (b) their maximal deflationary effects on the lung are already reached with submaximal activation; (c) their expiratory capacity is hindered by the expansion of the lung apposed rib cage and limited by diaphragmatic passive tension, and (d) their efficiency is reduced by paradoxical motion and distortion both between and within the lung apposed rib cage and abdominal compartments. Possible mechanisms for the dependency of delta V on species, volume and posture are discussed.

Abdominal Muscles↗