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Biomedical subjects

T Lanthier

Publications and source records attributed to T Lanthier.

11 recordsLinked to original sources
PubMed1995

Cardiorespiratory effects of hemic versus nonhemic prime during and immediately following mitral valve replacement in dogs.

In order to limit the hemodilution effect during cardiopulmonary bypass (CPB) in low weight animal patients, blood is often used as a component of the prime solution. This study was undertaken to evaluate the effects of the addition of blood to the prime solution on the hemodynamic and respiratory parameters during and following mitral valve replacement in dogs. Ten dogs were randomly assigned to receive either a hemic (HP), 75% blood component, or a nonhemic prime (NP) solution. The hemodilution was 5 +/- 4% and 25 +/- 10% for the HP and NP groups, respectively. Cardiopulmonary measurements were taken 20 minutes before initiating CPB, during CPB, and 20 min after termination. The hematocrit level, the hemoglobin concentration, and the arterial oxygen content were significantly lower in the NP group during and following CPB. However, the systemic oxygen transport index was not significantly different between the NP group (355 +/- 87 mL/min/m2) and the HP group (546 +/- 155 mL/min/m2) following CPB. Our study indicates that, in normal dogs undergoing hemodilution from a nonhemic prime solution, the cardiovascular function is able to maintain the systemic oxygen transport in the period immediately following mitral valve replacement.

Analysis of Variance↗
PubMed1994

Evaluation of biocompatible osteoconductive polymer shelf arthroplasty for the surgical correction of hip dysplasia in normal dogs.

Biocompatible osteoconductive polymer (BOP) shelf arthroplasty was performed on ten nondysplastic dogs, divided into five groups. Each group was evaluated at 6, 13, 17, 26 or 39 weeks postsurgery. Evaluation consisted of clinical, radiological and histological studies. The dogs were injected with three fluorochrome markers, 28 days, 14 days and 6 hours before euthanasia. Transverse sections of undecalcified arthroplasty site were examined by microradiography and fluorescence microscopy; surface-stained sections were evaluated by light microscopy. The BOP shelf arthroplasty was not technically difficult. Minimal mineralization of the shelf was noted by radiography, 26 and 39 weeks postop. A moderate to large amount of fibrous mature connective tissue was observed around the BOP fibers throughout the study. Bone ingrowth occurred around the BOP fibers, but was minimal within them. This osseous proliferation of the arthroplasty was very slow to take place; it was first noted microscopically 17 weeks postsurgery and was still minimal 39 weeks after surgery. These findings suggest that there may be interference to the osteoconductive properties of BOP by fibrous tissue. Ossification of the shelf arthroplasty was too unsatisfactory to recommend its use for the treatment of canine hip dysplasia.

Animals↗
PubMed1992

Optimal time-window duration for computing time/frequency representations of normal phonocardiograms in dogs.

The optimal duration of the time-window used to compute the time-frequency representation (spectrogram) of the phonocardiogram was studied in four dogs by using intracardiac and thoracic measurements of the PCG. The power and cross-spectrograms of the intracardiac and thoracic PCGs were computed using a fast Fourier transform algorithm and a sine-cosine window with 10 per cent decaying functions. A coherence spectrogram was also computed for each dog to study the linear relationship between the two signals and determine the optimal time-window duration. Results show that the optimal range of the time-window duration is between 16 and 32 ms. A time-window shorter than 16 ms spreads out low-frequency components into the higher frequencies and generates a spectrographic representation with poor frequency resolution (> or = 62.5 Hz). A window larger than 32 ms increases the frequency resolution but smears the spectrographic representation of the signal in the time domain and thus cannot correctly reflect the time-varying properties of the signal. In both cases, the amplitude of the coherence function computed between the left ventricular and the thoracic phonocardiograms is overestimated.

Animals↗
PubMed1991

Interaction between the aortic valve leaflets and a Millar dual-micromanometer catheter during recording of the aortic component of the second heart sound in dogs.

The influence of the closure of the aortic valve leaflets on a dual-micromanometer Millar catheter is investigated with respect to the power spectrum of the aortic component (A2) of the second heart sound in dogs. The catheter inserted through the aortic valve is used to simultaneously record A2 in the left ventricle and in the aorta and to study the transmission of A2 up to the body surface. Results indicate that the interaction of the valve leaflets with the Millar dual-micromanometer catheter during the closure and vibration of the aortic valve does not produce a clapping artefact. The main effect is a change in the natural modes of vibration (resonant frequencies) of the aortic valve resulting from a modification of the vibrating structure (combined structure composed of the catheter, the aortic valve and the surrounding blood and tissues) because of the tight mechanical coupling between the aortic valve leaflets and the catheter. In addition, this modification of the natural modes of resonance does not invalidate the estimation of the frequency response of the transfer function between the aortic root and the thoracic recording site, even if the mean gain of the transfer function is affected and the phase slightly increased with frequency. On the contrary, the interaction of the aortic valve leaflets with the catheter seems to slightly increase the spectral contribution (coherence) of the intra-aortic A2 to the thoracic A2.

Animals↗
PubMed1991

Acoustic transmission of the aortic component of the second heart sound within the ascending aorta of dogs.

The spectral characteristics of the acoustic transmission of the aortic component of the second heart sound within the ascending aorta was studied using a Millar dual-micromanometer catheter. The tip micromanometer was located close to the aortic valve leaflets while the second micromanometer was located 3 cm above the aortic valve. The frequency response of the transmission properties (amplitude and phase) of the blood and the aortic wall was modelled by an equivalent acoustic transmission system. The signal recorded by the tip micromanometer located near the aortic valve was considered to be the input signal of the equivalent system and the signal recorded by the second micromanometer was used as the output signal. Results of the spectral analysis of the input and output signals show that the acoustic transmissibility of blood in the ascending aorta is high at 20 Hz (the attenuation is negligible). Between 20 and 60 Hz, the transmissibility decreases at a rate of -3 dB per octave while between 60 and 120 Hz it decreases at a rate of -14 dB per octave. Above 120 Hz the transmissibility is low and the resulting attenuation is greater than 20 dB. The phase of the transfer function is shifted by -60 degrees at 20 Hz and decreases at a mean rate of -2.0 degrees Hz-1 between 20 and 100 Hz and -0.75 degrees Hz-1 up to 400 Hz. The phase velocity of the sound transmission is relatively constant (5.5 ms-1) between 40 and 100 Hz and increases up to 9 ms-1 at 300 Hz.

Animals↗
PubMed1990

Spectral analysis and acoustic transmission of mitral and aortic valve closure sounds in dogs. Part 3. Effects of altering heart rate and P-R interval.

A surgical protocol was designed to implant, in seven dogs, a programmable sequential atrioventricular pacemaker after destruction of the bundle of His to produce a chronic heart block. The heart rate and P-R interval were then varied independently and their influence on the spectra and acoustic transmission of the mitral M1 and aortic A2 valve closure sounds was studied. Results indicate that the major effects of varying the P-R interval are a strong change in the intensity of M1 and modifications of its acoustic transmission across the heart/thorax acoustic system. No similar influence is observed on the intensity and acoustic transmission of A2. Varying the heart rate has a small effect of the intensity of M1 but none on the intensity of A2. In addition, changes in either the P-R interval or the heart rate do not seem to modify the spectral profile of the intracardiac and thoracic M1 and A2 components.

Animals↗
PubMed1990

Spectral analysis and acoustic transmission of mitral and aortic valve closure sounds in dogs. Part 4: Effect of modulating cardiac inotropy.

A surgical protocol was designed to implant in dogs a programmable atrioventricular pacemaker and to destroy the bundle of His with one to four 0.1 ml formaldehyde injections. The heart rate and P-R interval were paced at 100 beats min-1 and 75 ms, respectively. Cardiac inotropy was then varied in five animals by using injections or infusions of cardiotonic drugs (Dobutamine, Betalol and Quinidine). Their effect on the spectra and acoustic transmission of the mitral M1 and aortic A2 closure sound components produced within the left heart and transmitted up to the body surface was studied. Results indicate that changes in cardiac inotropy strongly modify the intensity of M1 and A2 but do not markedly affect their spectral distribution. They also affect the transfer function of the heart/thorax acoustic system, but this influence is small compared with that of a 12 min reference interval. In addition, it was shown that the intensity of M1 is more sensitive to the cardiotonic agents than the intensity of A2.

Animals↗
PubMed1990

Spectral analysis and acoustic transmission of mitral and aortic valve closure sounds in dogs. Part 1. Modelling the heart/thorax acoustic system.

A system model based on the simultaneous recording and analysis of the intracardiac and thoracic phonocardiograms to estimate the time-varying properties of the heart/thorax acoustic system of the dog is described. The presence of instrumental noise in the recording of intracardiac phonocardiograms is characterised, and it is demonstrated that its effect on the estimate of the transfer and coherence functions of the system can be quantified and corrected. Application of the model to study the spectral characteristics and the acoustic transmission properties of the mitral component M1 of the first heart sound and of the aortic component A2 of the second heart sound in the dog shows that the heart/thorax acoustic system acts like a bandpass filter having a higher attenuation for A2 than for M1. Between 20 and 100 Hz, the mean attenuation of M1 is 30 dB while that of A2 is 46 dB. Above 100 Hz, the attenuation slope is -12 dB per octave for M1 and -6 dB per octave for A2.

Animals↗
PubMed1990

Spectral analysis and acoustic transmission of mitral and aortic valve closure sounds in dogs. Part 2. Effects of neuromuscular blockade, sternotomy and pacemaker control, and a two-week recovery period.

The paper describes the effects of neuromuscular blockade, sternotomy and atrio-ventricular pacing, and a two-week recovery period on the spectra and acoustic transmission of mitral M1 and aortic A2 sound components in dogs. Results indicate that neuromuscular blockade does not affect the attenuation properties of the heart/thorax acoustic system even if it modifies the intensity of M1 and the phase of the transfer function. The immediate effect of sternotomy and cardiac pacing is an important increase in the attenuation of the heart/thorax acoustic system. This increased attenuation is different for both sounds (20 dB for M1 and 11 dB for A2) and disappears after a two-week recovery period. However, the resulting controlled dog model shows slightly different acoustic characteristics than those of the normal animal model.

Animals↗
PubMed1990

Use of laser Doppler flowmetry to determine blood flow in and viability of island axial pattern skin flaps in rabbits.

Perfusion and viability of island axial pattern skin flaps were tested in 37 healthy New Zealand white rabbits, using laser Doppler monitoring of blood flow in the capillary loops and the subpapillary plexus of the dermis. Skin flaps, selected on the basis of the caudal superficial epigastric vein and artery, were lifted and replaced in their original locus after selective occlusion of their vascular pedicles. Subjects were allotted into groups: control group (n = 10); arterial occlusion (n = 7); venous occlusion (n = 10); and arterial and venous occlusion (n = 10). The rabbits were monitored from 48 hours before surgery until euthanasia 48 to 72 hours after replacement of the flap. Flap viability was assessed on a clinical basis, using a comparative scoring method based on a numeric scale. The degree of necrosis in histologic sections was evaluated, using a scoring system. Laser Doppler measurements were obtained on 3 consecutive days before surgery, to establish the normal basal blood flow in the skin. Postsurgical measurements were obtained at 2-hour intervals for the first 8 hours and at 24, 48, and 72 hours after surgery. Measurements of basal blood flow varied significantly (P less than 0.05) from site to site on the surface of individual flaps and over time. When laser Doppler flowmetric (LDF) measurements from 6 sites on a flap were used as a measure of laser Doppler flow for the total flap, there was no significant difference between contralateral flap areas outlined on the abdomen of the rabbits. Temporal variations over 3 days for each rabbit or among rabbits were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗