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Biomedical subjects

C J Griffiths

Publications and source records attributed to C J Griffiths.

At least 19 recordsLinked to original sources
PubMed1995

Respiratory muscle activity during rapid eye movement (REM) sleep in patients with chronic obstructive pulmonary disease.

BACKGROUND: In patients with chronic obstructive pulmonary disease (COPD) periods of hypopnoea occur during rapid eye movement (REM) sleep, but the mechanisms involved are not clear. METHODS: Ten patients with stable COPD were studied during nocturnal sleep. Detailed measurements were made of surface electromyographic (EMG) activity of several respiratory muscle groups and the accompanying chest wall motion using magnetometers. RESULTS: Hypopnoea occurred in association with eye movements during phasic rapid eye movement (pREM) sleep. During pREM sleep there were reductions in EMG activity of the intercostal, diaphragm, and upper airway muscles compared with non-REM sleep. Episodic hypopnoea due to partial upper airway occlusion ("obstructive" hypopnoea) was seen consistently in four subjects while the others showed the pattern of "central" hypopnoea accompanied by an overall reduction in inspiratory muscle activity. Although activity of the intercostal muscles was reduced relatively more than that of the diaphragm, lateral rib cage paradox (Hoover's sign) was less obvious during pREM-related hypopnoea than during wakefulness or non-REM sleep. CONCLUSIONS: Hypopnoea during REM sleep in patients with COPD is associated with reduced inspiratory muscle activity. The pattern of hypopnoea may be either "obstructive" or "central" and is generally consistent within an individual. Relatively unopposed action of the diaphragm on the rib cage during REM sleep is not accompanied by greater lateral inspiratory paradox.

Aged↗
PubMed1995

Respiratory muscle activity and oxygenation during sleep in patients with muscle weakness.

Patients with respiratory muscle weakness show nocturnal hypoventilation, with oxygen desaturation particularly during rapid eye movement (REM) sleep, but evidence in individuals with isolated bilateral diaphragmatic paresis (BDP) is conflicting. The effect of sleep on relative activity of the different respiratory muscles of such patients and, consequently, the precise mechanisms causing desaturation have not been clarified. We have studied eight patients, four with generalized muscle weakness and four with isolated BDP during nocturnal sleep with measurements including oxygen saturation and surface electromyographic (EMG) activity of various respiratory muscle groups. Nocturnal oxygenation correlated inversely with postural fall in vital capacity, an index of diaphragmatic strength. During REM sleep, hypopnoea and desaturation occurred particularly during periods of rapid eye movements (phasic REM sleep). In most subjects, such events were "central" in type and associated with marked suppression of intercostal muscle activity, but two subjects had recurrent desaturation due to "obstructive" hypopnoea and/or apnoea. Expiratory activity of the external oblique muscle was present whilst awake and during non-rapid eye movement (NREM) sleep in seven of the eight subjects in the semirecumbent posture. This probably represents an "accessory inspiratory" effect, which aids passive caudal diaphragmatic motion as the abdominal muscles relax at the onset of inspiration. Expiratory abdominal muscle activity was suppressed in phasic REM sleep, suggesting that loss of this "accessory inspiratory" effect may contribute to "central" hypopnoea. We conclude that, in patients with muscle weakness, nocturnal oxygenation correlates with diaphragmatic strength.(ABSTRACT TRUNCATED AT 250 WORDS)

Electromyography↗
PubMed1994

The effect of controlled-release salbutamol on sleep and nocturnal oxygenation in patients with asthma and chronic obstructive pulmonary disease.

Patients with asthma or chronic obstructive pulmonary disease (COPD) may have falls in oxygen saturation at night. We have investigated the effect of a long acting beta agonist (salbutamol CR) on nocturnal oxygen saturation (SaO2) in asthma and COPD. Eleven asthmatic and 14 COPD patients in stable condition were randomly allocated to 8 mg salbutamol CR or placebo twice daily in a double-blind, cross-over study. FEV1 at entry was 71.5% predicted in the asthmatic patients and 36% predicted in the COPD group. Each treatment period lasted 7 days, at the end of which measurements of ventilatory function and detailed sleep studies were performed. There was a significant improvement in morning FEV1 in the asthmatic patients when on active treatment and a small, but non-significant improvement in the COPD group. Sleep architecture and oxygenation were similar on placebo and on active treatment in both groups. We conclude that salbutamol CR has no significant effect on nocturnal oxygenation or sleep pattern in patients with mild asthma or moderately severe COPD.

Albuterol↗
PubMed1994

Automated measurement of the cyclic activity of respiratory muscles.

A microcomputer-based system developed for the automated analysis of the electromyogram (EMG) recorded from respiratory muscles in a variety of situations is described. In addition, an assessment of the performance of the system is presented, along with data relating intercostal EMG activity to ribcage movement in seated subjects. Studies were performed on sixteen normal subjects--non smokers, mean (+/- SD) age 31 (+/- 6) years, mean (+/- SD) mass 78 (+/- 8) kg--of which fifteen studies proved suitable for analysis. Each study lasted for a period of five minutes, during which time recordings of intercostal EMG, ribcage postero-anterior displacement (RCPA) and airflow were made. For every breath taken by each of the subjects, the peak integrated EMG activity (iEMGpeak) was measured both by hand and by the automated system. The automated and manual measurements of iEMGpeak, which ranged from 0.0 to 91.3 microV, differed by only -0.82 +/- 3.34 microV (mean +/- SD). The index iEMGpeak and two additional indices of iEMG activity (iEMGmean, iEMGarea) were evaluated with respect to RCPA, a measure of overall respiratory activity. The indices of iEMG were observed to show an exponential dependence on RCPAamp, the amplitude of ribcage motion. Following a log transformation to linearise the relationship, the correlation of each index with RCPAamp was evaluated; iEMGpeak and iEMGarea correlated similarly with RCPAamp (no significant difference at 5% level), but iEMGmean was found to be a significantly different (p < 0.001) and poorer correlate. We conclude that the automated analysis of respiratory iEMG as described in this paper can provide results showing consistency with manual measurement.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Bladder function in healthy volunteers: ambulatory monitoring and conventional urodynamic studies.

OBJECTIVE: To obtain data on conventional artificial filling cystometry and ambulatory monitoring in healthy asymptomatic control populations. SUBJECTS AND METHODS: Seventeen healthy volunteers were assessed by means of artificial filling cystometry (CMG), filling at rates of 50 ml/min (CMG 50) and 100 ml/min (CMG 100), and ambulatory monitoring (AM). RESULTS: Significant differences were found between AM and CMG with respect to: the pressure rise on filling (P < 0.02), voided volumes (P < 0.01) and maximum detrusor pressure on micturition (P < 0.01). Detrusor instability was found in 38% of volunteers on AM, in 17% on CMG 50, but in none on CMG 100. CONCLUSION: A range of baseline urodynamic values has been established which could provide the basis for future studies of ambulatory monitoring.

Adult↗
PubMed1993

Protection and radiography of heat affected teeth.

The authors propose a protocol for the stabilisation and protection of the fragile human skull (following very hot fires where there is breakdown of teeth and bone). Also discussed is a method for carrying out dental radiology on heat affected bone and teeth.

Accidents, Aviation↗
PubMed1993

Variability in ciliary beat frequency in normal subjects and in patients with bronchiectasis.

BACKGROUND: There is a wide variation in tracheobronchial clearance of inhaled aerosol in normal subjects and in patients with bronchiectasis, but little information is available on the variability in ciliary beat frequency (CBF). METHODS: The variability in CBF was measured in 10 nasal mucosal samples from each of 19 normal controls and 23 stable bronchiectatic subjects. RESULTS: The CBF varied at different mucosal sites in both normal subjects and bronchiectatic patients. Although the CBF of the fastest beating cilia was similar in both groups, the CBF of the slowest beating cilia was, on average, lower and showed greater within subject variation in bronchiectatic than in normal subjects. CONCLUSIONS: There is a wide variation in CBF in nasal mucosal samples and this is significantly wider in bronchiectatic subjects with some cilia beating slowly. This may be a consequence of chronic inflammation or infection.

Adult↗
PubMed1993

Detrusor contraction strength in men undergoing prostatectomy.

Elective prostatectomy is a frequently performed operation but the outcome may not always be satisfactory. This is probably because a significant number of men, despite subjective symptoms, are not urodynamically obstructed before operation and the preoperative assessment of obstruction is not easy using conventional urodynamic criteria. We have calculated detrusor contraction strength (WF) in men before and after prostatectomy. Our aim was to determine its relationship with symptomatic and urodynamic findings before and after prostatectomy and whether it was associated with clinical outcome. One hundred and twenty nine men listed for operation because of symptoms and low urinary flow rates were studied by means of urodynamic investigation and symptom scoring both before and 6 months after prostatectomy. A significant association was found between persistent obstructive symptoms after operation and a low WF before operation (P = 0.01), suggesting that weak detrusor function before operation was the cause of persistent symptoms afterwards. A significant correlation was also found between a high pre-operative WF and a high post-operative urinary flow rate; (P = 0.003); men with high detrusor power achieving the better flow rates after operation. Despite this relationship, the overall subjective clinical outcome was not strongly associated with WF and WF was no better than simple measurement of voiding pressure in predicting outcome in a multivariate analysis. The measurement of detrusor contraction strength provides some insight into the relationship between bladder function and clinical outcome after prostatectomy, but we have found it unable to predict outcome for the individual patient.

Aged↗
PubMed1992

Ambulatory monitoring of bladder pressure in low compliance neurogenic bladder dysfunction.

Upper tract dilatation is an important complication of neurogenic bladder dysfunction. Risk factors include incomplete bladder emptying with large residual volumes of urine and high tonic increases in bladder pressures during artificial filling. However, on natural bladder filling many of these patients do not have high tonic increases in detrusor pressures. We compared conventional urodynamic studies with ambulatory monitoring during natural bladder filling in 66 patients with low compliance neurogenic bladder dysfunction. There were marked differences in the tonic increase in bladder pressure during filling and in compliance during artificial bladder filling compared with ambulatory monitoring. Faster filling rates during artificial filling resulted in greater end filling pressures and lower compliance but the lowest increases in bladder pressure were found during ambulatory monitoring with natural bladder filling. During natural bladder filling significantly more patients had phasic changes in detrusor pressure; a high intensity of phasic activity during ambulatory monitoring correlated with high end filling pressures during artificial bladder filling. Upper tract dilatation was associated with large volumes of residual urine, high resting bladder pressures and low bladder compliance on filling at 100 ml. per minute. However, upper tract dilatation was most strongly associated with high intensity phasic pressure activity during natural bladder filling in combination with high residual urine volumes and high resting bladder pressures. On multivariate statistical analysis the intensity of phasic pressure activity during ambulatory monitoring was the best discriminator between patients with dilated and normal upper tracts. Our study has highlighted important differences in the results obtained by artificial filling cystometry and ambulatory monitoring during natural bladder filling. In particular, high increases in pressure did not occur during natural bladder filling, apparently being replaced by phasic activity. Within this group of patients who had the high risk factor of low bladder compliance measured during artificial bladder filling, a combination of greater residual urine volumes, greater resting pressures and greater phasic activity during natural bladder filling was found in patients with upper tract dilatation.

Adolescent↗
PubMed1992

Safety of ondansetron.

Ondansetron is a novel 5-HT3 receptor antagonist used for the treatment of cytotoxic-induced emesis and postoperative nausea and vomiting. Safety data from volunteer studies, non-emesis development studies, studies in the treatment of cytotoxic-induced emesis and postoperative nausea and vomiting, and spontaneous case reports, all indicate that ondansetron is well tolerated and has an excellent safety profile. There are no known interactions of ondansetron with other drugs, and no interference with postoperative recovery.

Drug Tolerance↗
PubMed1991

Filling and voiding pressures measured by ambulatory monitoring and conventional studies during natural and artificial bladder filling.

A total of 20 men awaiting elective prostatectomy for bladder outflow obstruction underwent conventional medium filling cystometry and ambulatory monitoring of bladder pressures during natural bladder filling. Total bladder capacity was similar during both tests (medium filling cystometry 256 +/- 138 ml. and ambulatory monitoring 248 +/- 120 ml., p not significant) as was the voided volume (medium filling cystometry 180 +/- 100 ml. and ambulatory monitoring 179 +/- 88 ml., p not significant). However, the peak urinary flow rate at the end of medium filling cystometry (4 +/- 6 ml. per second) was significantly lower than during ambulatory monitoring (9 +/- 4 ml. per second, p less than 0.05). The bladder contraction pressure during medium filling cystometry (79 +/- 44 cm. water) was significantly lower than during ambulatory monitoring (107 +/- 39 cm. water, p less than 0.005). Bladder pressures during voiding recorded after natural filling were significantly greater than after artificial filling. This finding may have significant implications for the use of conventional cystometry to study conditions such as outflow obstruction.

Aged↗
PubMed1991

A video system for investigating breathing disorders during sleep.

A system has been developed for investigating breathing during sleep that superimposes physiological signals on a video image of the patient, with the combined image plus sound recorded on video tape for later analysis. Signals normally displayed include oxygen saturation, airflow, chest wall motion, electroencephalogram, and electrooculogram; but others can be recorded if desired. The information is displayed on a timebase appropriate for the recognition and analysis of respiratory events during sleep. In addition, use is made of normally invisible video lines to record the analogue voltage waveforms so that on replay this information can be displayed on a fast timebase for analysing the more rapidly changing waveforms of electrophysiological signals. The system allows detailed polysomnography to be performed in the normal ward setting with the subject monitored overnight by the nursing staff. Subsequent analysis of the synchronised video, audio, and analogue signals allows measurement of the conventional indices obtained by polysomnography and aids their interpretation.

Humans↗
PubMed1991

Value of nocturnal oxygen saturation as a screening test for sleep apnoea.

The sensitivity and specificity of overnight recording of arterial oxygen saturation (SaO2) in routine clinical practice was evaluated in 41 subjects who were being investigated for possible sleep apnoea-hypopnoea syndrome. SaO2 was measured with an ear probe oximeter (Biox IIa) and chart recorder during an "acclimatisation" night immediately before a detailed polysomnographic study. The recordings were classified by two observers as positive, negative, or uninterpretable. Twelve of the 41 patients had the obstructive sleep apnoea syndrome when defined in terms of an apnoea-hypopnoea index greater than 15 events an hour on the second night. The sensitivity of nocturnal SaO2 on the acclimatisation night when the diagnostic criterion was an apnoea-hypopnoea index of greater than 5, greater than 15, and greater than 25/h was 60%, 75%, and 100% respectively. Corresponding values for specificity were 95%, 86%, and 80%. Oximetry alone therefore allowed recognition of a moderate or severe sleep apnoea syndrome. In routine practice an appreciable number of equivocal results is likely and repeat oximetry or more detailed polysomnography will then be required if clinical suspicion is high.

Evaluation Studies as Topic↗
PubMed1991

Breathing during sleep in patients with myotonic dystrophy and non-myotonic respiratory muscle weakness.

Sleep apnoea and hypopnoea have been reported in myotonic dystrophy, but it is unclear whether this is simply attributable to the respiratory muscle weakness which is common in this condition. We therefore investigated whether breathing and oxygenation during sleep were more abnormal in patients with myotonic dystrophy than in patients with non-myotonic muscle weakness. Seven subjects were studied in each of three groups: normal controls, myotonic dystrophy and non-myotonic weakness. Patients in the latter group were chosen to represent a similar range of severity of respiratory muscle weakness to those with myotonic dystrophy. Detailed polysomnography was performed; the severity of breathing disorders during sleep was quantified in terms of the frequencies of apnoea and hypopnoea and the degree of arterial desaturation. The myotonic patients showed more frequent apnoea and hypopnoea and more severe desaturation than the other two groups; the results in the non-myotonic patients were generally intermediate. The results suggest that abnormal breathing during sleep is common in myotonic dystrophy and is not due solely to the direct effects of respiratory muscle weakness. Somnolence, which is a well recognized symptom of myotonic dystrophy, was not clearly attributable to the sleep apnoea/hypopnoea syndrome nor to abnormal sleep architecture in the myotonic patients.

Adult↗
PubMed1990

Measurement of voiding pressures on ambulatory monitoring: comparison with conventional cystometry.

A series of 20 patients underwent conventional medium fill cystometry (CMG) and ambulatory monitoring during natural bladder filling (AM). The measurement of voiding pressures by the 2 techniques was compared. The maximum subtracted detrusor contraction pressure recorded during CMG (50 +/- 30 cm H2O) was significantly less than that recorded during AM (86 +/- 35 cm H2O). Voiding pressures during natural filling are greater than those observed during conventional urodynamic studies: this finding may have important implications in the definition of bladder outflow obstruction.

Adult↗
PubMed1989

Ambulatory monitoring of bladder and detrusor pressure during natural filling.

We have developed a system to perform fully ambulatory monitoring studies of the bladder. Bladder and rectal pressures are recorded during natural filling of the bladder for up to 6 hours. This system has been evaluated in 19 studies performed on 15 patients. The mean duration of the studies was 3 hours 51 minutes (standard deviation +/- 1 hour 3 minutes) and the mean number of voids per patient was 3.8 +/- 2.2. Visual inspection of the recorded data showed that subtraction of the rectal trace from the bladder trace provided a useful detrusor trace when subjects were ambulant as well as resting. When ambulant, movement caused typical peak-to-peak pressure variability in the bladder and rectal traces of approximately 30 +/- 20 cm. water (mean and standard deviation of peak-to-peak pressure for typical ambulant 5-minute sections for each patient), which after subtraction was reduced on the detrusor trace to 10 +/- 5 cm. water. The equivalent figures when resting were 9 +/- 5 cm. water, subtracting to less than 5 cm. water for the detrusor. Further measurements also were calculated for the whole of each trace. The system provided good quality recordings and should prove useful in future evaluations of natural fill urodynamic studies.

Adult↗
PubMed1989

Ambulatory monitoring of bladder pressures in patients with low compliance as a result of neurogenic bladder dysfunction.

A group of 28 patients with neurogenic bladder dysfunction and low bladder compliance was studied using medium fill cystometry (CMG) and ambulatory monitoring (AM) during natural bladder filling. The aims of the study were to compare the 2 techniques and to determine if ambulatory monitoring might be useful in predicting upper tract dilatation. AM demonstrated significantly lower end filling pressures compared with CMG. Phasic detrusor contractions were found more commonly during AM and the frequency of phasic detrusor contractions during AM was associated significantly with poor compliance identified during CMG. Patients with upper tract dilatation had significantly greater residual urine volumes, higher pressure rises during CMG and higher frequencies of phasic detrusor contractions compared with those patients with normal upper tracts. The high pressures seen at the end of a medium fill CMG were not found during AM and therefore are unlikely to be the underlying explanation of upper tract dilatation in such patients.

Adolescent↗