Determination of peak expiratory flow

It is still unknown whether peak expiratory flow (PEF) is determined by "wave speed" flow limitation in the airways. To investigate the influences of airway mechanical properties on PEF, five healthy adults performed maximal forced expiratory effort (MFEE) manoeuvres, in the standard manner and following breathholds at total lung capacity (TLC) of 2 s and 10 s. Oesophageal pressure (Poes) was measured as an index of respiratory effort. Subjects also performed a MFEE following a 10 s breathhold during which intrathoracic pressure was voluntarily raised by a Valsalva manoeuvre, which would increase transmural pressure and cross-sectional area of the extrathoracic airway. Additional MFEEs were performed with the neck fully flexed and extended, to change longitudinal tracheal tension. In separate studies, PEF was measured with a spirometer and with a pneumotachograph. Breathholds at TLC (2 s and 10 s), and neck flexion reduced PEF by a mean of 9.8% (SD 2.9%), 9.6% (SD 1.6%), and 8.7% (SD 2.8%), respectively, when measured with the spirometer. The same pattern of results was seen when measured with the pneumotachograph. These reductions occurred despite similar respiratory effort. Voluntarily raising intrathoracic pressure during a 10 s breathhold did not reverse a fall in PEF. MFEE manoeuvre with neck extension did not result in an increase in PEF, the group mean % changes being -3.0% (SD 5.0%). We conclude that these results do not allow the hypothesis that "wave-speed" (Vws) is reached at PEF to be rejected. A breathhold at TLC could increase airway wall compliance by allowing stress-relaxation of the airway, thus reducing the "Vws" achievable.     

Omeprazole as a diagnostic tool in gastroesophageal reflux disease

OBJECTIVE: To determine the diagnostic value of empirical treatment with omeprazole in the diagnosis of gastroesophageal reflux disease (GERD). METHODS: Patients with symptoms suggestive of GERD underwent upper gastrointestinal endoscopy and 24-h esophageal pH monitoring. Patients with reflux esophagitis grade 0 or 1 were included in the study and were randomized to double-blind treatment with either 40 mg omeprazole or placebo o.m. The effect of treatment was evaluated after 1 and 2 wk with a symptom questionnaire with a four-grade Likert scale, and symptomatic response outcome was compared with the results of 24-h pH-metry. RESULTS: Ninety-eight patients were included; however, 13 were excluded from the final analysis because of protocol violation. Of the remaining 85 patients, 54 had no signs of esophagitis at endoscopy, and 31 had esophagitis grade 1. The pH registration showed pathological gastroesophageal reflux in 47 patients (55%). Forty-one patients were randomized to treatment with omeprazole and 44 to placebo. There was a significant correlation between the pH registration result and response to omeprazole (p = 0.04, chi2), but not to placebo (p = 0.16). With pH-metry as the gold standard, the omeprazole test had positive and negative predictive values of 68% and 63%, respectively, for the diagnosis of GERD. When the omeprazole test was used as the gold standard, the positive and negative predictive values of pH monitoring were 68 % and 63 %, respectively. Similar sensitivity was found when the pH-metry was compared with presence of esophagitis. CONCLUSION: Determination of the symptomatic response to 40 mg of omeprazole for 14 days is a simple and inexpensive tool for the diagnosis of GERD, with a sensitivity and specificity comparable to 24-h pH monitoring.     

Management of asthma based on their peak expiratory flow rate monitoring

SCN1B, the human gene encoding the beta1-subunit of the voltage-gated sodium channel has previously been cloned and mapped to Chr 19q13.1. The sequence of the homologous mouse gene, Scn1b, has now been determined from cDNA. The mouse gene is highly conserved, encoding a predicted protein with 99%, 98% and 96% amino acid identity to the rat, rabbit, and human homologs, respectively. DNA sequence conservation is also striking in the 3' untranslated region which shows 67% and 98% to human and rat, respectively. Unlike the human and rat homologs, high expression of mRNA from the mouse gene is confined to adult skeletal muscle and brain, and is not observed in heart. As Scnlb maps to Chr 7, in close genetic proximity to the quivering gene (qv), the coding region of Scnlb was also cloned from a qvJ/qvJ homozygous mouse and assessed as a candidate for the site of this genetic defect. Comparison of qv and wild-type cDNAs showed no changes in the predicted amino acid sequence that could cause the qv phenotype. However, three silent polymorphisms in the DNA coding region indicate that Scn1b is close to qv, and is within a region of genetic identity with DBA/2J, the inbred background on which the qvJ allele arose.     

Reproducibility of peak expiratory flow measurements

The ease of PEF measurement and the availability of inexpensive, portable instruments have led to its increasing use. However, relatively little literature exists addressing the testing procedure, optimal frequency, instrument precision, and virtually no epidemiologic literature exists describing the variability of repeated PEF tests within a single test session (reproducibility). A summary of data from one of the authors' own worker population studies is presented which addresses precision of PEF measurement.     

The accuracy of several brands of portable peak flow meter, and the predicted value of peak expiratory flow rate for children

The accuracy, reproducibility and interdevice variability of 6 brands of peak flow meter were evaluated by using a flow generator. The accuracy was satisfiable except for Mini-Wright, which overread by up to 29%. It is essential to identify the brands to compare the data of peak expiratory flow rate (PEFR) from different studies. The reproducibility was under 5%, reliable enough for personal monitoring. The low range models were inferior to the normal range models as a whole. There are some studies about the normal value of PEFR for Japanese children. They have drawn different linear equations to obtain the predicted value of PEFR from the body height. However, none of them can be the "gold standard".     

Correlates of peak expiratory flow rate: a study of sand stone quarry workers in desert

BACKGROUND: Pulmonary infections continue to be a major cause of morbidity and mortality in patients with sickle cell disease (SCD). METHODS: In this study cell-mediated immunity in vitro was evaluated in 62 SCD patients (62 steady state and 16 with acute pneumonia) and compared with 44 normal controls (30 healthy and 14 with acute pneumonia). Lymphocyte blastogenic responses to phytohemagglutinin, tetanus toxoid and Candida albicans antigen were assessed in all subjects. In addition production of tumor necrosis factor, alpha- and gamma-interferon (IFN) were assayed. RESULTS: The results revealed comparable blastogenic responses to all three stimuli in all subjects except SCD patients with pneumonia. This group showed poor responses to all stimuli. The mean counts per minute were decreased 65 to 90% when compared with the other patients. Cytokine production of IFN-alpha and TNF was equivalent in all subjects. Conversely IFN-gamma production in both SCD groups, steady state (35 +/- 6 U/ml) and SCD with pneumonia (14 +/- 6 U/ml), was significantly decreased when compared with those in normal healthy controls (65 +/- 14 U/ml) and with pneumonia (48 +/- 17 U/ml). On analysis of individual titers 15 of 62 (24%) steady state and 10 of 16 (63%) SCD patients with pneumonia were deficient in IFN-gamma production in vitro. CONCLUSIONS: Acute pulmonary infections seem to have a profound effect on cell-mediated immunity in SCD. IFN-gamma deficiency, along with quantitative and qualitative T cell abnormalities, may represent significant factors to explain the frequent and severe infections seen in SCD.     

Peak expiratory flow and the resistance of the mini-wright peak flow meter

The purpose of this study was to examine whether the resistance of the peak flow meter influences its recordings. One hundred and twelve subjects, (healthy nonsmokers and smokers and subjects with lung diseases) performed three or more peak expiratory flow (PEF) manoeuvres through a Fleisch pneumotachograph with and without a mini-Wright peak flow meter added in random order as a resistance in series. The results were as follows. In comparison with a pneumotachograph alone, peak flow measured with an added mini-Wright meter had a smaller within-test variation, defined as the difference between the highest and second highest values of PEF in a series of blows. The mean (SE) variation was 14 (1.3) L.min-1 and 19 (1.5) L.min-1 with and without meter added, respectively. In comparison with the pneumotachograph alone, the addition of the mini-Wright meter caused PEF to be underread, especially at high flows. The difference (PEF with meter minus PEF without meter) = -0.064 (average PEF) -8 L.min-1; R2 = 0.13. The mean difference was -7.8 (1.1) %, and increased numerically for a given PEF, when maximal expiratory flow when 75% forced vital capacity remains to be exhaled (MEF75%FVC) decreased. The reproducibility criteria for repeated measurements of peak flow are more appropriately set at 30 L.min-1 than the commonly used 20 L.min-1, because a within-test variation of less than 30 L.min-1 was achieved in 76% of the subjects without PEF meter inserted and in 88% with meter inserted, with no difference between healthy untrained subjects and patients. The resistance of the peak expiratory flow meter causes less variation in recordings but reduces peak expiratory flow, especially at high values and when the peak is large as compared with the rest of the maximal expiratory flow-volume curve.     

Peak expiratory flow rate (PEF) and serum eosinophil cationic protein (ECP) changes in nocturnal asthmatics

We have investigated the serum ECP and peak expiratory flow rate in 20 patients with nocturnal asthma. Changes of PEF were measured in every 2 hours around the whole day, and the blood samples were obtained at 4:00 and 16:00 to measure the serum ECP level and the peripheral Eo numbers. In addition, 10 asthmatics as well as normal subjects received methacholine challenge at 4:00 and 16:00. It was found that the PEF reached the lowest point at 4:00 and obviously less than that at 16:00 (187.50 +/- 120.31 L/min vs 313.00 +/- 108.14 L/min, P < 0.05), that the airway reactivity at 4:00 was significantly higher than at 16:00 (P < 0.05) and the difference of MCH-PC20 between the two time points was 0.34 +/- 0.31 mg/ml, that the serum ECP level at 4:00 was obviously higher than that at 16:00 (11.14 +/- 7.40 micrograms/ml vs 5.49 +/- 4.12 micrograms/ml, P < 0.05). The change rate of PEF markedly related to the change of serum ECP between the two time points (r = 0.61, P < 0.05). The findings suggested that the activation of Eo and its release of ECP might be effect of the circadian-rhythmic change of pulmonary functions in nocturnal asthma.     

Perception of expiratory flow by asthmatics and non-asthmatics during rest and exercise.

The perception of normal and asthmatic individuals was assessed using a magnitude production procedure in a series of 3 studies, testing 10 male and 10 female 20–30 yr old Ss during rest, then 9 female 20–35 yr old Ss during submaximal exercise (both groups with no history of respiratory disease), and 10 12–18 yr old male asthmatics using no steroid medication and 10 nonasthmatic age- and sex-matched controls during rest and submaximal exercise. Findings do not support an abnormality in perception occurring during exercise in asthma patients. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Normal peak expiratory flow in healthy adult male and female subjects

A functional rotatory computed tomography (CT) study of 423 whiplash patients with cervical spine soft-tissue injury was undertaken to determine its diagnostic value. The results are correlated with previous CT studies on normal subjects, and an evaluation of paradox motion, in which the lower vertebra rotates more than the vertebra immediately superior to it, is given. Asymmetrical left/right rotation reached the pathological value in 36% of the patient population at the level of C0-1. Twice as many patients had hypermobile rotation to the left as compared with the right, perhaps indicating that the right alar ligament is more often damaged in injuries involving the whiplash mechanism. A higher percentage of pathological values for hypermobile rotation was found at the level of C0-1 than at C1-2. Patients exhibiting paradox rotation had a significantly higher amount of rotation to the contralateral side than did those who exhibited no paradox rotation. These findings validate the use of functional rotatory CT in the evaluation of soft-tissue damage of the upper cervical spine resulting from whiplash injury.     

Peak expiratory flow rate in school-going children

Two members of a unique class of natural antibodies have been identified in all of a large cohort of sera from clinically normal humans of broad age distribution. By means of a series of 10-12 mer peptides the epitope for each of those antibodies was characterized with regard to amino acid identity and conformation. Similar epitope specificity was revealed for the IgM isotopes of cord blood and early post natal sera and for IgM and IgG of adult sera, suggesting that the class of natural antibodies represented by the two identified in this study includes those genomically coded for at their effector level of maturation in the B cells of the neonate. Assay of series of specimens from each of four clinically normal adults revealed that those two natural antibodies are present at relatively constant titer, unique to each individual, over four to five and a half year periods. Those observations imply that the primary function of that class of natural antibodies may be related to maintenance of homeostasis and the molecular identity of each of the two epitopes suggests a role, for each, as monitor or control in intracellular traffic. The previous identification of those epitopes in a conserved protein of HIV also provides support for the proposition that a secondary function of natural antibodies, arising from fortuitous coincidence of the identity of the epitopes, may be that of early defense against infectious invaders.     

Health-related quality of life outcomes of omeprazole versus ranitidine in poorly responsive symptomatic gastroesophageal reflux disease

OBJECTIVE: This study evaluated changes in health-related quality of life (HRQL) outcomes of once-daily omeprazole compared with ranitidine for the short-term treatment of patients with poorly responsive symptomatic gastroesophageal reflux disease (GERD). METHODS: A double-blind, randomized clinical trial, compared omeprazole versus ranitidine for the treatment of poorly responsive GERD. Eligible patients had a history of predominant heartburn symptoms with symptomatic heartburn after 6 weeks of ranitidine treatment. Patients were randomized to omeprazole 20 mg once daily (n = 156) or ranitidine 150 mg twice daily (n = 161) and followed for 8 weeks. Assessments were completed at baseline and after 8 weeks with physician-rated symptoms: Gastrointestinal Symptom Rating Scale (GSRS); Psychological General Well-Being (PGWB) Index; Sleep Scale; Impact on Daily Activities Scale, and Overall Treatment Effect. Primary HRQL endpoints were the GSRS reflux scale and PGWB total score. RESULTS: No differences between the 2 treatment groups were observed in baseline demographic, clinical or HRQL measures. After 8 weeks, omeprazole-treated patients had greater improvement in GSRS reflux scale scores (p<0.0001) and PGWB total scores (p = 0. 019) compared with ranitidine-treated patients. Significant between group differences favoring omeprazole were also observed in GSRS total scores (p<0.0001), abdominal pain scale scores (p = 0.003), and indigestion scale scores (p = 0.003), Impact on Daily Activities (p = 0.001), PGWB positive well-being (p = 0.015), anxiety (p = 0. 030), and general health scale scores (p = 0.010). Patient ratings of overall treatment effect demonstrated the significantly (p<0. 0001) greater benefits of omeprazole (mean = 5.26) compared with ranitidine treatment (mean = 3.83). CONCLUSIONS: Omeprazole treatment significantly reduced persistent reflux-related symptoms and normalized psychological well-being compared with ranitidine in poorly responsive symptomatic patients with GERD.     

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.     

Rates of change in peak expiratory flow and in diurnal variation in peak flow in patients recovering from acute severe asthma

Reexpression of the insulin-like growth factor type II (IGF-II) gene has recently been described in hepatocellular carcinoma (HCC). In this study, we used a nonisotopic in situ hybridization method to analyze the expression of IGF-II mRNA in a series of 28 HCCs arising on cirrhotic and noncirrhotic livers. An immunohistochemical method was used to detect IGF-II peptide. Hepatitis B virus (HBV) status and the histological differentiation degree were also evaluated. Increased expression of IGF-II mRNA was found in 4 of 28 HCCs, and 7 of 17 cirrhotic patients showed IGF-II mRNA in the cirrhotic nodules surrounding the HCC. A slightly higher rate of positivity for IGF-II mRNA was found in the HBV-negative patients than in HBV-positive ones. Positive immunostaining for the IGF-II peptide in the HCC and/or in surrounding cirrhotic nodules was found in 10 of 28 cases. The normal hepatocytes of the noncirrhotic patients were always negative for IGF-II peptide and mRNA. The similarities between our results and those from experimental models in woodchucks seem to support the concept that heterogeneous phenotypic groups could exist in human HCCs.     

Peak expiratory flow rate in Nigerian school children

Peak expiratory flow rate (PEFR) was measured using the Wright's peak flow meter in 263 school boys and 275 school girls living in Lagos, Nigeria. Their ages ranged from 6.0 years to 19.0 years (mean 11.9 +/- 3.8 yrs. for boys and 11.8 +/- 3.9 yrs. for girls). Mean PEFR was 359.2 +/- 102.0 L/min (range 160.0-610.0 L/min) in boys and 327.7 +/- 81.3 L/min (range 160.0-500.0 L/min) in girls. Apart from ages 17, 18 and 19, peak expiratory flow rates were similar in both boys and girls. In both sexes, PEFR correlated positively and significantly with age, height, weight and body surface area. Also in both sexes and in all age groups studied, PEFR was significantly higher than predicted values obtained from previous Nigerian and caucasian prediction equations. When compared with values obtained from a second caucasian prediction equation, observed values were significantly higher in the 6-10 years and 16-19 years age groups in boys and 11-15 years and 16-19 years age groups in girls. New prediction equations for calculating PEFR in Nigerian boys and girls are presented. Observed PEFR may be due to enhanced stature in Nigerian children resulting from improved environment and genetic factors.     

Evaluation of the effect of environmental exposure to tobacco smoke on variability of peak expiratory flow rate in children

A panel study was conducted in autumn (116 children) and repeated in spring (66 children) to test the hypothesis that the individual variability of peak expiratory flow rate (PEFR) depends on the environmental exposure to tobacco smoke (ETS). PEFR was measured twice a day (morning: PEFR-M; evening: PEFR-E), using individual meters at homes, in children exposed (ETS+) and not exposed (ETS-) to tobacco smoke at home. In examined groups the individual variability of PEFR-M was--on average--8.0% (ETS+; autumn), 8.1% (ETS+; spring), 10.5% (ETS-; autumn) and 7.7% (ETS-; spring). The individual variability of PEFR-E was 8.0% (ETS+; autumn), 7.9% (ETS+; spring), 9.5% (ETS-; autumn) and 7.4% (ETS-; spring). The results of multivariate analysis of within- and between-subject variability showed the presence of statistically significant within-subject variability only in ETS+ group (PEFR-M in autumn; PEFR-M and PEFR-E in spring). With all the limitations of a panel study design the findings suggest that environmental exposure to tobacco smoke in children affects the degree of within-subject variability of PEFR in children.     

Relationship of daytime asthma symptom frequency to morning peak expiratory flow

This study examined appraisal of self and others, as measured by semantic differential ratings of Police, State, Society, Family, Friend, Myself as a Man/Woman, and Myself as a Political Person, in 55 tortured political activists in Turkey, 55 nontortured political activists, and 55 nontortured, politically noninvolved controls. There were no remarkable differences between tortured and nontortured political activists; both groups differed from controls in having a more negative appraisal of the police and the state and stronger perceptions of danger, mistrust, and injustice in relation to state authority. Lack of beliefs concerning a "benevolent state" may have protected the survivors from the traumatic effects of state-perpetrated torture. Further research into the possible protective role of belief systems in posttraumatic stress disorder is needed.     

Effects of air pollution on symptoms and peak expiratory flow measurements in subjects with obstructive airways disease

In preterm neonates, intraventricular haemorrhage is linked to the dysfunction of cerebral autoregulation (AR). We aimed at tracing the critical closing pressure (CCP) in order to quantify AR and to reveal its inner workings. In an observational study, 10 preterm neonates (median, range: ga 28 weeks, 25 to 32 weeks; bw 1070, 685 to 1730 g; age 2d, 1 to 7 d) were continuously Doppler traced (a. carotis interna) for > 10 min. Systemic blood pressure (BP, a. umbilicalis, a. radialis, a. temporalis) was recorded simultaneously (> 1200 cardiac cycles each). Systolic BP was on average 11 mmHg above CCP. There was a striking parallel between both variables, even in cases of sudden spontaneous BP fluctuations > 30% (r = 0.72, 0.41 to 0.99), while systolic cerebral blood flow velocity remained largely unaffected (r = -0.15, -0.75 to 0.53), indicating a properly functioning AR. CCP was 28 mmHg, 14 to 38 mmHg. Based on our data, a physiological model of AR is developed, integrating anatomy, metabolic and neuronal pathways with former physiologic findings--including low frequency cycling of cerebral blood flow velocity. Tracing of CCP is thought to have the potential to identify infants with impaired AR. Since this method is noninvasive and independent of angle of insonation (thus rendering it uncritical in probe fixation), it is a promising tool for sustained monitoring of cerebral haemadynamics in the clinical setting.