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Biomedical subjects

M J Mussell

Publications and source records attributed to M J Mussell.

14 recordsLinked to original sources
PubMed1992

The need for standards in recording and analysing respiratory sounds.

Respiratory sounds (RSs) recorded from the chest and trachea are nowadays being electronically analysed by many investigators with a view to (i) determining the mechanisms of their production, and (ii) to develop automated diagnostic systems based on RS analysis, that objectively categorise RS as being associated with health or respiratory diseases. However, one problem that hampers this type of research is that almost every RS investigation team uses different equipment, protocols and analysis methods which, to varying degrees, makes inter-investigator results difficult to compare. The review first discusses the many variables involved in RS recording and analysis, and the different approaches used by different investigators, to highlight this problem and its consequences. Secondly, although the review cannot propose immediately acceptable guidelines and standards for RS analysis, it proposes a 'seed' set of guidelines that are 'up for discussion' between investigators in the field, the final goal being to inject a degree of standardisation in equipment and methods that are acceptable to all involved.

Auscultation↗
PubMed1992

Comparison of normal respiratory sounds recorded from the chest and trachea at various respiratory air flow levels.

Respiratory sounds (RS)s were recorded from the trachea and chest of 10 normal adult subjects at respiratory air flow levels of 1.6, 2.1 and 2.6 l/s using an oral flow transducer, and at approximately 2.1 l/s without the flow transducer. Tracheal RS (TRS) and chest RS (CRS) frequency spectra were generated using Fast Fourier Transform, and the peak, mean and maximum frequency parameters were derived from each spectra. Parametric analysis showed: (i) all three parameters for TRS spectra are significantly higher than those for CRS spectra; (ii) TRSs are on average eight times louder than CRSs; (iii) both TRSs and CRSs are air-flow independent over the flow range, though TRSs are significantly modified by the flow transducer while CRSs are not; and (iv) though of similar loudness, inspired and expired RSs (both TRSs and CRSs) have some significant spectral differences. To compare the complex shapes of RS spectra, each spectra was divided into narrow frequency bands (to create a feature set) and principal component analysis was performed on all spectral feature sets. TRSs and CRSs were shown to be independent biological signals with little overlap in their respective spectral characteristics.

Adult↗
PubMed1990

Effect of air flow and flow transducer on tracheal breath sounds.

Tracheal breath sounds (TBSs) were analysed in 12 normal adult subjects at the air flow levels of 1.6, 2.1 and 2.6 litres-1, using a low-resistance flow transducer, and at an estimated flow of 2.1 litres-1 without the flow transducer. The major findings were that the TBSs were significantly distorted by the flow transducer, but were independent of air flow. We therefore conclude that true TBSs can only really be recorded when an oral flow transducer is not used. The within-subject reproducibility of TBS was relatively good, while the cross-subject comparison of TBS showed that each subject produced their own unique spectral pattern, although the TBSs of normal subjects fall in a common frequency range. Also, inspiratory sounds were significantly lower in peak frequency than expiratory TBSs.

Adult↗
PubMed1990

Distinguishing normal and abnormal tracheal breathing sounds by principal component analysis.

Expired and inspired tracheal breathing sounds (BS) were recorded from 10 normal subjects and 8 patients with respiratory diseases, including bronchial asthma, sarcoidosis, fibrosing lung disease, chronic bronchitis, and radiation pneumonitis. Frequency spectra were generated using Fast Fourier Transform (FFT), and we observed considerable differences between BS spectra of normal subjects and patients. The frequency of peak amplitude and mean frequency of the BS spectra of patients were significantly higher than those of normal subjects. Spectral features were extracted by dividing each spectra into equal frequency bands--each feature being the mean amplitude of each FFT element within a frequency band. We used Principal Component Analysis to compare spectral feature sets and found a clear separation between normal and abnormal tracheal BS for 10, 20, and 40 features/spectra. We conclude that Principal Component Analysis of BS could become a new method of diagnosing respiratory disease in an automated fashion.

Adult↗
PubMed1990

A constant flux of carbon dioxide injected into the airways mimics metabolic carbon dioxide in exercise.

This paper reports the expired minute-ventilation (VE) responses of 5 subjects to three step levels in a) work rate on a bicycle ergometer (30, 50, and 70 W), b) inhaled constant fraction (CF) of CO2 (3, 5, and 7%), and c) inhaled constant flux (CFlux) of CO2 (0.3, 0.4, and 0.5 l/min (STPD) injected in the inspired air-stream). Both exercise (isocapnic with regulated PETCO2) and CFlux provoke larger and similar steady-state responses in VE, than CF. Both the CF and CFlux responses are hypercapnic, but the CFlux responses show evidence of "hypercapnic regulation." VE and total CO2 input into the alveoli (i.e., VCO2 plus inhaled CO2) are excellently correlated in both the CF and the CFlux cases. However, the CFlux delivery provokes a far greater VE for a given total input of CO2 than CF, and the CFlux response resembles the VE/VCO2 plot of exercise. We conclude that CFlux inhalation of CO2 simulates the metabolic CO2 production rate of exercise, and thus the humoral aspects of exercise hyperpnea in the steady state.

Adult↗
PubMed1990

Modeling of alveolar carbon dioxide oscillations with or without exercise.

In five persons the transient ventilatory response was measured to three step levels of exercise, inhaled constant fraction of CO2, and inhaled constant flux of CO2. With constant CO2 fraction inhalation (3, 5, and 7%), the transient response of the minute-ventilation (VE) is associated with on- and off-time delays (Td). Our Td periods include equipment delay, and our bolus inhalations by constant flux provoke on- and off-Td's of 6-8 s, which approximate to the transport delay of blood passing from the alveoli to the peripheral chemosensitive areas. With exercise (30, 50, and 70 W) we found a fast rise in VE (i.e., mainly in respiratory frequency) within the first breath, but no detectable on- and off-Td. The ventilatory responses to exercise are equal to those of constant CO2 flux inhalation. We modeled PACO2 oscillations, which occur through a respiratory cycle, and show that the oscillations provoked by constant CO2 flux have modified timing, amplitude, and slope compared with those of constant CO2 fraction. The increase in ventilation is the same when the CO2 is achieved by constant flux inhalation at rest or by exercise.

Carbon Dioxide↗
PubMed1989

A new CO2 inhalation system for studying regulation of breathing.

This paper describes the development of a computer-controlled system that controls inspired CO2 or end-tidal PCO2 (PETCO2) to follow preprogrammed functions such as step, sinusoid, and pulse, under normoxic, hyperoxic, and hypoxic conditions. The system uses a proportional-integral (PI) controller that was optimized by adjusting the PI parameters so as to minimize the integral-time of absolute error (ITAE) performance parameter.

Analog-Digital Conversion↗
PubMed1988

Trachea-noise biofeedback in asthma: a comparison of the effect of trachea-noise biofeedback, a bronchodilator, and no treatment on the rate of recovery from exercise- and eucapnic hyperventilation-induced asthma.

We review some of the evidence that supports the existence of psychosomatic triggers to bronchospasm in asthmatics, and hypothesize that it may also be possible to consciously reverse bronchospasm using trachea-noise biofeedback. We precipitated significant levels of bronchospasm in 16 asthmatics using exercise or eucapnic-hyperventilation challenges on five occasions, and administered four different treatments and a no-treatment control. The treatments were trachea-noise biofeedback (TNBF), wrong-information TNBF, an inhaled adrenergic bronchodilator, and a placebo inhaler, all given double blind. Half of the subjects had 3 training days in the use of the TNBF device before study. Our results show that TNBF, in the trained subjects only, is associated with a detectable, but not statistically significant, increase in the rate of recovery from bronchospasm over that found with no treatment. We conclude that, although asthmatics seem to have a strong ability to consciously induce bronchospasm, conscious reversal of a full asthma attack using TNBF is limited. Despite contrary conclusions by other investigators, we believe that this study demonstrated little TNBF-assisted recovery from bronchospasm. We suggest that this is because its effect may be inhibited by humoral mechanisms that sustain the attack, but we believe further work is required to support this.

Adult↗
PubMed1986

Trachea noise biofeedback device to help reduce bronchospasm in asthmatics.

Evidence suggests that conscious control of bronchial smooth muscle tone may be possible. The asthmatic wheeze is caused mainly by broncho-constriction and it is hypothesized that if wheeze were consciously reduced, some bronchodilation would occur. Described here is a biofeedback device which records asthmatic tracheal noise with a microphone, and generates both an audio and visual display of the degree of wheeze sound intensity. The subject attempts to reduce wheeze using the device. Wrong information is also generated within the device so that the placebo effect can be investigated.

Asthma↗
PubMed1986

Control of expired CO2 level and minute-ventilation during a hyperventilation challenge for asthmatics.

Hyperventilation of cold dry air initiates bronchospasm in most if not all asthmatics. The hyperventilation challenge is a useful means of studying asthma and the evaluation of anti-asthma drugs and treatments; two key elements of such a challenge are the means of achieving a target minute-ventilation and the maintainance of constant arterial CO2 levels during hyperventilation. The author describes a simple cold air eucapnic hyperventilation challenge which allows a subject to hyperventilate to a predetermined target minute-ventilation whilst maintaining a constant expired level of CO2.

Asthma↗