The effect of a mechanical glottis on peak expiratory flow rate and time to peak flow during a peak expiratory flow manoeuvre: a study in normal subjects and patients with motor neurone disease

We have evaluated a mechanical glottis in healthy volunteers and in patients with bulbar motor neurone disease. In healthy volunteers, the mechanical glottis increased peak flow rate and decreased the time to peak flow during forced expiration, but cough produced even higher flow rates and shorter times to peak flow. In patients, the mechanical glottis increased peak flow rate and decreased the time to peak flow. The mechanical glottis also produced higher peak flow rates when compared to the cough manoeuvres, and the time to peak flow was also significantly shorter with the mechanical glottis. We have shown that the use of a mechanical glottis tends to convert the airflow profile of a peak expiratory flow manoeuvre into that of a cough in both healthy volunteers and patients with motor neurone disease. Its potential role as an aid to clearance of airway secretions in patients with impaired laryngeal function remains to be seen.     

Changes in symptoms, peak expiratory flow, and sputum flora during treatment with antibiotics of exacerbations in patients with chronic obstructive pulmonary disease in general practice.

BACKGROUND--Bacterial infections of the lower airways during an exacerbation in patients with asthma or chronic obstructive pulmonary disease (COPD) may be the cause of an exacerbation or the consequence of a viral infection or an increase in airways limitation. To determine whether bacterial infection is an important component in the pathogenesis of an exacerbation, the effects of antimicrobial treatment must be studied. METHODS--Patients with asthma or COPD seen in general practice were studied in a double blind randomised manner to investigate whether the antimicrobial drugs amoxicillin (500 mg three times daily), cotrimoxazole (960 mg twice daily), or a placebo, each when added to a short course of oral corticosteroids, can accelerate recovery from exacerbations. Patients were instructed to contact their own physician early in the morning when complaints of increased shortness of breath, wheezing, or exacerbations of cough with or without sputum production occurred. Treatment effects were evaluated over the next 14 days by studying symptom scores (wheeze, dyspnoea, cough with and without mucus production, and awakening with dyspnoea), peak expiratory flow values (PEF, expressed as % predicted), and sublingual temperature. Bacteriological study of the sputum was made at the onset of an exacerbation and 7, 21 and 35 days afterwards. RESULTS--Of 195 patients enrolled 71 (36%) contacted their physician for symptoms of an exacerbation. Symptoms improved in all three groups, improvements ranging from 0.54 to 0.75 points per day on a four point scale. PEF% predicted showed improvements in the three groups after the exacerbation, ranging from 0.34% to 0.78% predicted per day, finally returning to baseline values. Sublingual temperature did not change. Six of 71 patients consulted their physician because of a relapse between four and 24 days after the start of treatment. In only two of the 50 sputum samples, collected during an exacerbation, and which contained > or = 10(5) bacteria in culture sensitive to the chosen antibiotic given, did any benefit from antimicrobial treatment occur. During the recovery period sputum purulence improved irrespective of antibiotic treatment. CONCLUSIONS--Antibiotics given with a short course of oral prednisolone during an exacerbation do not accelerate recovery as measured by changes in peak flow and symptom scores in ambulatory patients with mild to moderate asthma or COPD when treated by their general practitioners. Moreover, antibiotics do not reduce the number of relapses after treating an exacerbation.     

Value of serial peak expiratory flow measurements in assessing treatment response in chronic airflow limitation.

A double blind, randomised, placebo controlled, crossover trial of prednisolone (40 mg/day for 14 days) was carried out in 33 patients with chronic airflow limitation (mean age 62 years, mean FEV1 1.01 litres, mean FEV1/FVC ratio 44%), to assess the value of serial peak expiratory flow (PEF) measurements, taken five times daily in evaluating treatment response by comparison with other objective measurements and with measurements of symptoms. The mean serial PEF after a one week run in period was 189 1 min-1, during the second week of placebo 193 1 min-1, and during the second week on prednisolone 231 1 min-1. The difference in mean PEF values between placebo and prednisolone was significant (p less than 0.01). With regard to the response to steroids of the individual patients, 13 of the 33 had a detectable trend of improvement on visual inspection of serial PEF measurements during prednisolone treatment but only one during placebo administration. Of all the objective measurements made after the run in and after each treatment phase (12 minute walking distance, FEV1, forced vital capacity (FVC), serial PEF), the serial PEF chart provided the best discrimination between placebo and prednisolone treatment. There was no statistically significant association between steroid induced improvement in serial PEF measurements and in breathlessness, partly because of placebo improvements in symptoms in those who had no improvement in serial PEF values. This study indicates the importance of making objective measurements to identify a genuine steroid response rather than relying on symptomatic improvement alone. The best simple measurement to make is serial PEF during steroid trials. This is more sensitive in detecting a steroid response than are the 12 minute walking distance, FEV1, or FVC, and is also less likely than these measurements to show spurious placebo responses.     

Factors influencing peak expiratory flow in teenage boys.

BACKGROUND: Peak expiratory flow (PEF) is a useful measure of pulmonary health status and is frequently utilised in asthma management. Reduction in PEF is usually indicative of onset of asthma symptoms. However, use can be made of PEF values only if normal values are known. The definition of normal range is always difficult and may vary between regions and be affected by a variety of factors. OBJECTIVE: To establish PEF values for teenage boys in a Cape Town suburb and examine factors that possibly influence this measurement. SETTING: A high school for boys in the southern suburbs of Cape Town. METHODS: Measurements of PEF were taken for 124 boys. Subjects were approximately 16 years old and apparently healthy at the time of survey. Further details were provided by means of a questionnaire. RESULTS: PEF ranged from 350 to 760 l/min, with a mean (+/- standard deviation (SD)) of 539 +/- 68 l/min. Factors expected to influence PEF included height and mass, whereas unexpected factors included sport intensity and academic grade. A trend to reduced peak flow was already evident in boys who smoked and boys from homes where a parent smoked. Regression analysis suggested peak flow differences in our population compared with the standard reference. CONCLUSION: Interpretation of results obtained from peak-flow instruments should take into account additional knowledge concerning the individual. Further surveys of the South African population and of different groups should be done to establish local standards and factors influencing PEF.     

Serial measurements of peak expiratory flow and responsiveness to methacholine in the diagnosis of aluminium potroom asthma.

BACKGROUND: Obstructive airways disease in aluminium potroom workers has been recognised for over 50 years. There is still controversy about whether this is true occupational asthma. METHODS: A cross sectional survey of 379 potroom workers identified 26 subjects with symptoms suggestive of occupational asthma. Of these 26, 14 were considered by the plant physician to have occupational asthma and had a measurable PC20 methacholine (provocative concentration causing a 20% fall in FEV1). These 14 were further investigated by serial measurements of peak flow at home and work, symptom diaries, and measurements of methacholine reactivity before and after a three week holiday. RESULTS: There was a good correlation between daily symptom scores and minimum peak flow measurements; these showed changes characteristic of occupational asthma in 10 workers, with increased diurnal variation in peak flow and consistent deterioration in relation to work exposure. One further record showed probable occupational asthma and two showed consistent small changes in peak flow related to work exposure more in keeping with an irritant effect. Only one record was inadequate. Methacholine reactivity on a work day was within the normal range in nine of 13 subjects. A doubling of PC20 methacholine occurred in five of nine subjects with occupational asthma in whom repeated estimations were possible. CONCLUSIONS: This study confirms the existence of aluminium potroom asthma. The lack of correlation with measurements of non-specific responsiveness suggests that the primary mechanism is one of hypersensitivity, perhaps enhanced by the bronchial irritants also present in the potroom.     

Comparison of circadian variations using FEV1 and peak expiratory flow rates among normal and asthmatic subjects.

BACKGROUND--Most studies that describe circadian variations in asthma have used maximum rate of peak expiratory flow (PEF) rather than forced expiratory volume in one second (FEV1) to assess airway calibre. This study was designed to assess circadian variations in PEF and FEV1 measured simultaneously and to compare variations in these measurements in normal and asthmatic subjects in a stable clinical state. METHODS--Twenty nine subjects (nine asthmatic subjects on bronchodilators, 10 on inhaled steroids, and 10 normal controls) were asked to record their PEF and FEV1 with a new portable instrument every two hours during the day and once on waking at night for two weeks. Circadian variations were examined in different ways using arithmetical indices and cosinor analysis. RESULTS--78% of PEF values and 75% of FEV1 values were considered to be reproducible and were included in the analysis. Variations obtained using PEF did not differ from those obtained using FEV1. Significant cosinor variations were found in at least 50% of recording days for most of the subjects and showed the same features as for arithmetical indices. Daily variations in PEF and FEV1 were significantly correlated with airway calibre and PC20 methacholine (r approximately 0.5 to approximately 0.6). CONCLUSIONS--PEF is as satisfactory as FEV1 for describing circadian variations among normal subjects and stable asthmatic subjects.     

Circadian rhythm of peak expiratory flow in asthmatic and normal children.

A study was undertaken to examine the circadian rhythm of peak flow rate in asthmatic and normal children in the community by means of cosinor analysis. An initial study of 12 matched pairs of asthmatic and normal children was used to determine the mean amplitude of peak expiratory flow (PEF) variability in the two groups (7.8% and 4.4%) and the number of subjects required to show a significant difference. On the basis of this study 37 community based children with asthma diagnosed by questionnaire and 40 control subjects measured PEF four times daily for 14 days. Cosinor analysis of the data produced a significant fit in 20 asthmatic and 18 control children. A small but significant difference in amplitude was observed between the asthmatic (6.2%) and the control (4.2%) children. There was no significant phase difference between the rhythms in the two groups. Cosinor analysis explained 14% of PEF variance. It did not provide a reproducible estimate of phase between week 1 and week 2; the acrophase changed by more than one hour in 26 of 37 asthmatic children. The cosinor model may be inappropriate for the investigation of low amplitude circadian rhythms, especially when measurements are made infrequently.     

Influence of treatment on peak expiratory flow and its relation to airway hyperresponsiveness and symptoms. The Dutch CNSLD Study Group.

BACKGROUND--Despite effective treatments, the morbidity and mortality of obstructive airways disease (asthma and COPD) remains high. Home monitoring of peak expiratory flow (PEF) is increasingly being advocated as an aid to better management of obstructive airways disease. The few available studies describing effects of treatment on the level and variation of PEF have involved relatively small numbers of subjects and did not use control groups. METHODS--Patients aged 18-60 years were selected with PC20 < or = 8 mg/ml and FEV1 < 95% confidence interval of predicted normal. They were randomised to receive, in addition to a beta 2 agonist, either an inhaled corticosteroid (BA+CS), an anticholinergic (BA+AC), or a placebo (BA+PL). One hundred and forty one of these subjects with moderately severe obstructive airways disease completed seven periods of two weeks of morning and afternoon PEF measurements at home during 18 months of blind follow up. RESULTS--Improvements in PEF occurred within the first three months of treatment with BA+CS and was subsequently maintained: the mean (SE) increase in morning PEF was 51 (8) l/min in the BA+CS group compared with no change in the other two groups. Similarly, afternoon PEF increased by 22 (7) l/min. Diurnal variation in PEF (amplitude %mean) decreased from 18.0% to 10.2% in the first three months of treatment with BA+CS. Within-subject relations between changes in diurnal variation in PEF and changes in PC20 were found to be predominantly negative (median rho-0.40) but with a large scatter. Relations between diurnal variation in PEF and changes in symptom scores, FEV1, and bronchodilator response were even weaker. CONCLUSIONS--In patients with moderately severe obstructive airways disease, PEF rates and variation are greatly improved by inhaled corticosteroids. Since the relation of diurnal PEF variation with PC20, symptoms, FEV1, and bronchodilator response were all weak, these markers of disease severity may all provide different information on the actual disease state. PEF measurements should be used in addition to the other markers but not instead of them.     

Fall in peak expiratory flow during haemodialysis in patients with chronic renal failure.

Peak expiratory flow rate (PEF) was measured during haemodialysis in 30 unselected patients with chronic renal failure. The patients attended the hospital dialysis unit, where they received regular dialysis using a cuprophan dialyser with acetate buffered dialysate. Mean PEF had fallen by 60 l/min (13%) 30 minutes after the start of dialysis. In 10 of the 30 patients the fall in PEF was over 15%, the maximum fall being 32%. After the initial fall PEF increased throughout the next 2.5 hours of haemodialysis, but it fell again at five hours in the 14 patients who had been dialysed for four hours. During dialysis there was a reduction in blood white cell and platelet counts and in arterial oxygen tension at 30 and 60 minutes (p less than 0.05) and the white cell count and arterial oxygen tension were still reduced at three hours. The coincidence of the fall in PEF at 30 minutes and the fall in arterial oxygen tension suggests that bronchoconstriction might contribute to dialysis induced hypoxaemia by causing ventilation-perfusion disturbances. Appreciable airway dysfunction occurred in all the patients undergoing regular haemodialysis with new cuprophan dialysers and acetate buffered dialysate.     

Effects of regular salmeterol on lung function and exercise capacity in patients with chronic obstructive airways disease.

BACKGROUND: The aim of this study was to evaluate the effects of single and chronic dosing with salmeterol on exercise capacity and lung function in patients with chronic obstructive pulmonary disease. METHODS: Twenty nine patients of mean (SE) age 64 (1.5) years, forced expiratory volume in one second (FEV1) 42(3)% of predicted, and 5-15% reversibility to salbutamol 200 micrograms were randomised to receive four weeks treatment with salmeterol 50 micrograms twice daily or placebo in a double blind crossover fashion with a one week washout period in between. Measurements of spirometric parameters, static lung volumes, and exercise capacity were made one and six hours after a single dose, and six hours after the final dose of salmeterol or placebo. RESULTS: Salmeterol produced a small increase in FEV1 at one and six hours after a single dose, and this was maintained after chronic dosing (mean difference and 95% CI versus placebo): single dosing at one hour 0.07 (95% CI 0.02 to 0.11) 1, single dosing at six hours 0.16 (95% CI 0.09 to 0.22) 1, chronic dosing at six hours 0.11 (95% CI 0.03 to 0.19) 1. The increase in forced vital capacity (FVC) was greater with salmeterol than with placebo six hours after single but not chronic dosing: single dosing at six hours 0.17 (95% CI 0.04 to 0.29) 1, chronic dosing at six hours 0.02 (95% CI -0.18 to 0.22) 1. Slow vital capacity was increased after treatment with salmeterol compared with placebo one and six hours after single but not after chronic dosing. There were no significant differences in static lung volumes or exercise capacity after single or chronic dosing with salmeterol compared with placebo. Patients reported a significantly lower Borg score for perceived exertion following the six minute walk after chronic treatment with salmeterol compared with placebo. CONCLUSIONS: Salmeterol produced a small improvement in spirometric values compared with placebo consistent with the degree of reversibility originally shown by the subjects to salbutamol 200 micrograms. This was not associated with improvements in static lung volumes or exercise capacity, but there was some symptomatic benefit in that patients were able to walk the same distance in six minutes with less perceived exertion.     

Potassium studies in chronic obstructive airways disease.

Seventeen male patients with chronic obstructive airways disease in remission were separated into two groups according to arterial carbon dioxide tensions. Hypercapnia was associated significantly with hypoxia and increased red cell volume whereas normocapnia was not. Normocapnic patients were significantly lighter than those with hypercapnia. Total body potassium (TBK) measured by the whole body monitor was significantly low in two of the patients studied (P less than 0.005). The mean value for TBK for the normocapnic group as a whole was significantly low (P less than 0.005), but the mean value for the hypercapnic group was not. Serum potassium and erythrocyte potassium concentrations were normal even when TBK was low, and diuretics had no apparent influence on these potassium values. Of four patients (two in the series and two others) who had TBK measured after a recent episode of cor pulmonale, three had significantly low values. The only previous studies using a whole body monitor to measure TBK in chronic obstructive airways disease found no such low values, though other workers estimating exchangeable potassium by isotope dilution techniques had found evidence of gross potassium depletion. It is concluded that low TBK does indeed occur in patients with chronic obstructive airways disease and that gross depletion is more likely to follow an episode of cor pulmonale.     

Quantitative versus qualitative analysis of peak expiratory flow in occupational asthma.

BACKGROUND: Peak expiratory flow rates (PEF) are often used to confirm the diagnosis of occupational asthma. The records are usually analysed qualitatively, and this may lead to interobserver disagreement. In this study the diagnostic value of a qualitative assessment of change in PEF was compared with objective measures of change in PEF and the results of a specific inhalation challenge test with plicatic acid. METHODS: Twenty five patients with possible red cedar asthma recorded PEF six times a day for three weeks at work and for two weeks away from work and underwent a challenge test with plicatic acid at the end of the recording period. Patients were considered to have cedar asthma if the FEV1 after inhalation of plicatic acid was 15% or more below that on the control day. PEF was plotted against time and assessed qualitatively by three physicians. The graph was considered positive for cedar asthma if two of the three physicians agreed that PEF was lower at work than away from work. The 95% confidence interval for variation in PEF between periods at work and away from work was also obtained from 15 asthmatic patients without occupational asthma. Differences in PEF between periods at work and away from work were considered positive for occupational asthma in the patients exposed to cedar when they were outside the 95% confidence interval for variations in PEF in the 15 patients whose asthma was nonoccupational. RESULTS: Of the 25 men studied, 15 had a positive response to plicatic acid. The qualitative PEF analysis had a sensitivity of 87% and a specificity of 90% in confirming red cedar asthma as diagnosed by the specific challenge test. Among the objective methods tested, only the difference in mean PEF between the maximum PEF at weekends and the minimum PEF on working days had a sensitivity (93%) greater than that of the qualitative method and a similar specificity. CONCLUSIONS: The qualitative assessment of PEF is a good diagnostic test for cedar asthma. Only one objective method of PEF analysis proved to be slightly more sensitive than the qualitative method and similar in specificity.     

Comparison of normal and asthmatic circadian rhythms in peak expiratory flow rate.

A computer technique (cosinor analysis) has been used to evaluate circadian rhythms in airway calibre in normals and asthmatics. Two hundred and twenty-one normal subjects recorded peak expiratory flow rate (PEFR) at home four times a day for seven days. Rhythm detection was statistically significant in 145 of them (65.6%) who showed a mean amplitude of 8.3% of individual mean PEFR (+/- SD 5.2%). Amplitude was independent of age, sex, atopy, family history of asthma, and smoking habit. Fifteen of them were also studied three times a day for five days in the laboratory with flow-volume loops. Eleven showed significant PEFR rhythms at home. No single measurement from the flow-volume loop showed periodicity in as many of them but rhythms were now also detected in the other four normal subjects in some components of the loop. Fifty-six asthma patients were studied with a similar protocol of PEFR measurement and compared with the 145 rhythmic normal subjects. Mean phases of the normal and asthmatic rhythms were not significantly different with acrophases (peak of rhythm cycle) at 1557 and 1526 respectively. The mean asthmatic amplitude was, however, significantly greater at 50.9%. Nocturnal asthma, therefore, probably represents an exaggeration of a normal circadian rhythm in airway calibre. The amplitude of the PEFR rhythm is an index of bronchial lability and is thus valuable in monitoring asthma patients. An amplitude of greater than 20% should be a useful screening test for asthma.     

Validity of peak expiratory flow measurement in assessing reversibility of airflow obstruction.

BACKGROUND: Assessing the reversibility of airflow obstruction by peak expiratory (PEF) measurements would be practicable in general practice, but its usefulness has not been investigated. METHODS: PEF measurements were performed (miniWright peak flow meter) in 73 general practice patients (aged 40 to 84) with a history of asthma or chronic obstructive lung disease before and after 400 micrograms inhaled sulbutamol. The change in PEF was compared with the change in forced expiratory volume in one second (FEV1). Reversible airflow obstruction was analysed in two ways according to previous criteria. When defined as a 9% or greater increase in FEV1 expressed as a percentage of predicted values reversibility was observed in 42% of patients. Relative operating characteristic analysis showed that an absolute improvement in PEF of 60 l/min or more gave optimal discrimination between patients with reversible and irreversible airflow obstruction (the sensitivity and specificity of an increase of 60 l/min in detecting a 9% or more increase in FEV1 as a percentage of predicted values were 68% and 93% respectively, with a positive predictive value of 87%). When defined as an increase of 190 ml or more in FEV1, reversible airflow obstruction was observed in 53% of patients. Again an absolute improvement in PEF of 60 l/min or more gave optimal discrimination between patients with reversible and irreversible airflow obstruction (sensitivity 56%, specificity 94%, and positive predictive value 92%). CONCLUSION: Absolute changes in PEF can be used as a simple technique to diagnose reversible airflow obstruction in patients from general practice.     

Assessment of respiratory function in patients with chronic obstructive airways disease.

The reproducibility of some respiratory function tests and a simple self-paced walking test were assessed in 13 patients with stable chronic obstructive airways disease by making observations on six occasions at two to three weekly intervals. The coefficients of variation of the various tests were as follows: forced expiratory volume in one second, +/- 14.8%; forced vital capacity, +/- 11.1%; transfer factor (single breath carbon monoxide), +/- 15%; total lung capacity, +/- 8.8% by helium dilution and +/- 8.3% by body plethysmography; increase in heart rate and minute ventilation for an increase in oxygen uptake of 0.5 1 min-1, +/- 19.4% and +/- 16.3%; distance covered in a 12-minute walking test, +/- 8.2%. The 12-minute distance increased significantly over the first three studies. The considerable variations in the result of these tests in subjects with apparently stable clinical states and without changes in treatment should be considered when assessing the results of changes in treatment.     

Breathlessness and portable oxygen in chronic obstructive airways disease.

Breathlessness was measured in 20 patients with severe chronic obstructive lung disease by the use of a visual-analogue scale. Severe resting arterial hypoxaemia was not a feature. The severity of breathlessness measured in this way did not correlate well with the results of spirometric tests or with walking ability. The use of portable oxygen was studied during simple walking tests for its effect on walking ability and the sensation of breathlessness. Portable oxygen improved exercise capacity but a placebo effect of the system probably accounted for some of the improvement. A clear improvement of distressing breathlessness was observed and represented a useful therapeutic response. Breathlessness and simple exercise ability were shown to respond independently to oxygen breathing. The value of short-term intermittent oxygen in patients with severe chronic obstructive lung disease needs to be evaluated in terms of both exercise ability and breathlessness.     

Streamlining of air flow in the upper airways and trachea.

Streamlining of air flow in the upper airways and trachea has been investigated by inhaling 81m krypton through each side of the nose separately and counting over the lung fields with a gamma camera. 81m Kr inhaled through one nostril was uniformly mixed in the air stream by the time the carina was reached. Gas mixing occurs probably by a combination of diffusion and turbulent flow.