The reproducibility of forced expiratory wheezes

Previous work has shown forced expiratory wheezes (FEW) to be associated with onset of flow limitation and to have spectral characteristics similar to wheezes heard in patients with obstructive lung diseases. This study was designed to determine whether the acoustic characteristics of FEW are reproducible under controlled lung volume and flow conditions. Six healthy, nonsmoking young adults 28 to 37 yr of age were studied. They performed FVC maneuvers through a set of round apertures (diameters, 14, 12, 10, 8, 6, 4, 2, and 1 mm). Flow, measured with a pneumotachograph, and tracheal lung sounds, recorded with a Hewlett-Packard HP20510A contact sensor, were recorded simultaneously on magnetic tape and analyzed off-line. For each subject, data from three different aperture sizes, measured in triplicates, were analyzed (total of 54 runs); 199 different wheezes were identified (mean, 3.7 wheezes/run), and 56.7 +/- 5.1% (mean +/- SEM) of wheezes found in a certain run (range, 41.7 to 77.8%) were identical to wheezes found in the other two runs of the same aperture size (i.e., same flow rate). In 17 of the 18 sets of triplicate runs analyzed, at least one major wheeze was identical in all three runs of the set. In three of the sets, two different identical wheezes were found. These findings support a deterministic mechanism of generation of wheezes and is in line with the predictions of the "flutter theory."     

Inter-session reproducibility of peak expiratory flow with standardized expiratory maneuvers

BACKGROUND: In adults performing forceful expiratory maneuvers, the length of post-inspiratory pause prior to forced expiration may influence the subsequently measured peak expiratory flow (PEF) and increase its variability. We investigated the effects of two different lengths of breath-hold at total lung capacity (TLC) on the short-term reproducibility of PEF in healthy volunteers. METHODS: Forty-six healthy volunteers (age 34.6+/-8.5; 23 men) performed a series of maximal forceful expirations in two different test sessions, separated by approximately 2 weeks. In each test-session, PEF was measured with two different types of maneuvers. One maneuver (P) included a brief (<2s) post-inspiratory pause at TLC prior to forced expiration, whereas the second maneuver (NP) included no pause at TLC. The speed of inspiration to TLC was fast and similar for both maneuvers. In a given test session, all volunteers performed four efforts for each type of maneuver. The highest PEF for each maneuver was used for analysis. The Bland-Altman statistical analysis was used to determine inter-session reproducibility of PEF. RESULTS: Within-maneuver analysis of the between-test session reproducibility of PEF showed that neither maneuver systematically biased the measured PEF (mean difference 0.02L/s for the P and 0.17L/s for the NP maneuver). Inter-maneuver between-test session analysis similarly showed that neither maneuver introduced a systematic bias in the maximal PEF (mean difference ranged from -0.15 to -0.01L/s). The limits of agreement were comparable in all maneuver-pair analyses. CONCLUSIONS: Forceful expiratory maneuvers with or without a brief (<2s) pause at TLC produce comparable PEF values in test-retest sessions.     

Postural variation of the maximum inspiratory and expiratory pressures in normal subjects

The maximum static inspiratory and expiratory pressures (MIP and MEP, respectively) were measured in 15 normal male subjects (average age, 27.14 years) in standing and sitting position. The MIP was determined at RV and FRC and MEP was determined at TLC and FRC. No significant differences were found for these parameters between the two postures. Our study proves that the posture adopted by the subject when these two maneuvers are performed does not influence the results obtained.     

Forced expiratory wheezes in a patient with dynamic expiratory narrowing of central airways and an oscillating pattern of the flow-volume curve

Forced expiratory wheezes (FEW) are common and the pathogenesis of this phenomenon might involve fluttering of the airways, but this theory has not been confirmed in patients. We report a case of a patient with FEW and a normal FEV1 that showed a bronchoscopically confirmed collapse of the trachea and main stem bronchi during forced expiration. Superimposed to the flow-volume curve was an oscillating pattern with a frequency that corresponded well with the wheeze generated during forced expiration. The oscillating pattern in the flow-volume curve and the collapse of the major airways supports the theory of wheezes generated by fluttering airways during forced expiration. Although FEW may be found also in healthy subjects, flow limitation is essential for the generation of FEW. The inclusion of a forced expiratory maneuver in the clinical examination might therefore be helpful in guiding the diagnosis towards airways obstruction.     

Factors influencing urinary 6-sulphatoxymelatonin, a major melatonin metabolite, in normal human subjects

6-Sulphatoxymelatonin (aMT6s) has been measured, by a direct radioimmunoassay, in urine from 130 normal volunteers aged 2-80 years. Its relationship to a number of physiological parameters has been assessed. Total urinary excretion of aMT6s did not vary in a group of 40 children aged 2-20 years (24 boys and 16 girls) except when expressed as a function of body weight. In this case, total aMT6s excretion over 24 h decreased as a function of age. In 90 adult volunteers (44 men and 46 women) aged 20-80 years, there was an age-related decline in total 24 h aMT6s excretion with significantly lower values in elderly subjects. In this same adult group no relationships were found between total aMT6s excretion and body weight or height. No sex differences were found either in the 2-20 years or the 20-80 years groups. Pineal calcification was assessed by lateral skull X-ray in 26 adult volunteers (17 men and 9 women) aged 20-50 years. No significant differences in aMT6s excretion were found as a function of pineal calcification. In 16 of these subjects plasma melatonin and aMT6s also showed no relationship to pineal calcification. These studies confirm the usefulness of aMT6s as an index of melatonin secretion in normal volunteers.     

The best peak expiratory flow is flow-limited and effort-independent in normal subjects

Recently, it has been suggested that peak expiratory flow (PEF) may be determined by the wave speed flow-limiting mechanism. In six normal male subjects (age = 33 +/- 8 years) performing expiratory forced vital capacity (FVC) maneuvers, a negative expiratory pressure (NEP) of -10 cm H2O was randomly applied at the beginning of maximal expiration to assess changes in PEF as compared with baseline. During FVC maneuvers, the expiratory effort was measured by changes in esophageal pressure (Pes), as either peak expiratory Pes-Pes at end expiratory lung volume (DeltaPes(peak)) or maximal rate of rise of Pes (dPes/dt(max)). In each experimental condition, at least three FVC maneuvers with comparable expiratory effort were selected for analysis for each subject. With similar DeltaPes(peak) (107.2 +/- 34.9 versus 111.7 +/- 40.5 cm H2O) and dPes/dt(max) (1181 +/- 518 versus 1177 +/- 546 cm H2O/second) PEF amounted to 10.84 +/- 1.08 L/second and to 10.82 +/- 1.03 L/second with and without NEP, respectively. These data show that PEF obtained by normal subjects to the best of their abilities (best PEF) does not increase with NEP and indicate that the best PEF is a flow-limited and effort-independent parameter, reflecting only lung and airways mechanics as the other subsequent maximal expiratory flows achieved during the FVC maneuver.     

Forced expiratory maneuvers in children aged 3 to 5 years

There is no consensus about reproducibility and reliability of spirometry in young children. We evaluated forced expiratory maneuvers from 98 children aged 3 to 5 years with a variety of respiratory disorders before and after bronchodilator treatment. Forced vital capacity (FVC) and forced expiratory volume in 1 sec (FEV,) were analyzed for reproducibility by the American Thoracic Society criteria and for reliability based on the coefficient of variation (CVYo). Over 90% of the patients cooperated, however, while 95% could exhale for at least 1 second, very few generated an FEV, on all 6 “best” efforts. This clearly improved with age. Of all patients nearly 60% performed reproducible pre-and postbronchodilator sets of FVC but only 32% performed reproducible sets of FEV₁. Based on the CV%, those patients who could reproducibly perform an FVC and FEV, did it quite reliably (mean CV%, 9.38 and 7.01 for FVC and FEV₁, respectively). We conclude that while some very young children can perform spirometry, reliability of performance cannot be assumed in this age group. Pediatr Pulmonol. 1994;18:144–149. © 1994 Wiley-Liss, Inc.     

Effects of different expiratory maneuvers on inspiratory muscle force output

We assessed the effects of two different expiratory maneuvers (fast [F] or slow [S]) on the ability of normal subjects (n = 12, age 35 +/- 6 yr) to generate maximal inspiratory pressures and maximal inspiratory flows near residual volume (RV). With the F maneuver, the subject exhaled rapidly to RV and immediately performed a maximal inspiratory effort, whereas with the S maneuver the subject exhaled slowly to RV, paused for 4 to 6 s at RV, and then inspired forcefully. Maximal static inspiratory pressure against an occluded airway (PImax), and maximal dynamic inspiratory pressure (PIdyn) and maximal inspiratory flow (V Imax) with no added resistance, as well as the electromyographic activity of the parasternal muscles, were measured during each maneuver. Both maneuvers were initiated from TLC and were performed randomly. In comparison with the S maneuver, the F maneuver yielded values of higher (mean +/- SE) PImax (148 +/- 5 cm H2O versus 135 +/- 7 cm H2O, p < 0.05), PIdyn (33 +/- 2 cm H2O versus 28 +/- 2 cm H2O, p < 0.05), and V Imax (12.3 +/- 0.4 L/s versus 11.4 +/- 0.6 L/s, p < 0.05). In addition, the rate of rise of PImax, the rate of rise of PIdyn, and the integrated peak electromyographic activity of the parasternal muscles were significantly greater with the F than with the S maneuver, suggesting greater inspiratory muscle (IM) activation. The enhanced IM activation may be related to a specific inspiratory-expiratory muscle interaction similar to the agonist-antagonist interactions described for a pair of skeletal muscles.     

Breathing during sleep in normal subjects

Despite considerable data, little is certain about changes in breathing during sleep, let alone possible mechanisms for these changes. This article reviews methodologic problems, including the definition of the normal subject, the definition of the sleep state, and the effects of instrumentation, and discusses data on respiration during REM and NREM sleep in normal humans. Although the evidence is incomplete, respiration during sleep appears fragile, prone to instability, to upper airway obstruction, to hypoventilation, and to ventilation-perfusion mismatch, jeopardizing the homeostatic function of CO2 output and O2 uptake.     

Maximal inspiratory and expiratory mouth pressures in sitting and half-lying positions in normal subjects

Maximal inspiratory (PImax) and expiratory (PEmax) mouth pressures were measured in seven normal adults in both sitting and half-lying positions on 2 days. Analysis of variance did not reveal significant differences between measurements made in the two positions for either PImax or PEmax. Measurements were repeatable and the results obtained in both positions were pooled. The coefficient of variation of PImax was 4.7% between-trials and 10.3% between-days, and those for PEmax were 3.4% and 4.4%, respectively. It is suggested that measurements of PImax and PEmax made in the half-lying position after thoracic surgery can be compared to pre-operative values which are commonly obtained in sitting without any influence from a positional effect. Details of the methodology to improve the reliability of the respiratory mouth pressures technique are discussed.     

Forced expiratory maneuvers in very young children. Assessment of flow limitation

The application of negative expiratory pressure (NEP) to the airway opening during forced expiratory maneuvers has recently been described as a noninvasive method to assess whether flow limitation is achieved in adults. This methodology has great potential for extending the measurement of forced expiratory maneuvers to young children who may not produce maximal efforts as reproducibly as adults. We used NEP to assess flow limitation in 10 children between 3 and 5 yr of age. NEP was well tolerated by all subjects. With the application of NEP, there was not a step increase in flow, a finding consistent with flow limitation for the subjects. In addition to visual inspection, we proposed a method to quantify the change in flow during a short NEP. The flow-volume curves obtained with and without NEP were visually the same, other than the flow transients produced by NEP. The calculated values of FVC and FEF25-75 were not significantly different when measured from flow- volume curves with and without NEP. There was a statistically significant increase in FEV1 with NEP; however, the group mean increase in FEV1 was less than 2%. We conclude that NEP may be a useful technique to determine whether flow limitation has been achieved in young children performing forced expiratory maneuvers.     

Factors influencing the healing rate of gastric ulcer in hospitalised subjects.

A multiple linear regression analysis was carried out on 75 inpatients with gastric ulcer. In order to elucidate the effects of various factors - endoscopic and roentgenological findings, age, sex, medical history, and drugs such as antacids, anticholinergics or both - on the healing rate, these factors were compared between those with ulcer which healed within eight weeks after treatment and those which did not. In patients over 50 years of age, alcohol consumption of over 60 g per day until admission, duration of present ulcer pain for over three months, single ulcer, ulcer located in the lesser curvature and uneven elevation around the ulcer, there was significant delaying effect on ulcer healing. Drug ingestion, sex, smoking habits until admission, size, depth, and shape of ulcer, coexisting gastritis, and past and family history of ulcer disease had no significant effect on healing after eight weeks. The patients with less than two unfavourable factors (n = 46) had the best healing rate (100%) compared with those with three (n = 20) or four or more (n = 9) unfavourable factors. The healing rate of the latter two groups was 60% and 22%, respectively (p less than 0.001). A prognostic score based on these six factors represents the severity of gastric ulcer disease with regard to the healing rate in patients prescribed antacids, and/or anticholinergic drugs.     

Factors influencing frequency of flatus emission by healthy subjects

The purpose of the present study was to measure the frequency of flatus emission by 25 healthy subjects and to determine if factors commonly thought to influence flatulence actually correlate with the frequency of gas passage. Over a one-week period on their usual diet, subjects passed gas 10±1 times/day [upper limit of normal (mean+2sd): 20 times/day]. The addition of the nonabsorbable disaccharide lactulose (10 g/day) to the diet significantly (P<0.01) increased flatus frequency to 19±2.4 times per day. Gender, age, and the ability of an individual's colonic flora to produce methane had no significant influence on flatus frequency either on the basal or lactulose-supplemented diets. Some subjects consistently passed gas more often than did others. These individual differences appeared to result, in part, from differences in the ability of the flora to produce gas from a given quantity of fermentable material.Supported in part by the Department of Veterans Affairs, and the National Institute of Diabetes and Digestive and Kidney Diseases DK-13093.     

Effects of cisapride on salivary production in normal subjects

Cisapride improves reflux esophagitis and enhances esophageal acid clearance. To test the effect of cisapride on salivary production, we enrolled 14 healthy volunteers in a double-blind, randomized, placebo-controlled study. Subjects received cisapride, 10 mgper os four times a day, or placebo for three days. Saliva, collected during fasted and fed states, was analyzed for volume and buffer capacity. Buffer capacity was expressed as the volume of 0.01 N HCl needed to titrate 1 ml of saliva to pH 6.1. Both volume and buffer capacity significantly increased during the fed state as compared to the fasted on both cisapride and placebo. Cisapride significantly enhanced the postprandial salivary volume and buffer capacity compared to placebo: 29.6±11.3 ml vs 22.9±9.5 ml and 1.07±0.31 vs 0.89±0.28, respectively (P<0.0001). Cisapride's enhancement of salivary flow rate and buffer capacity in the fed state may be another mechanism by which it exerts its beneficial effect in patients with reflux esophagitis.Supported by a grant from The Janssen Research Foundation.Preliminary data from this paper have been presented at the 1994 meeting of the American Motility Society, Wintergreen, Virginia and published, in abstract form (Gastroenterology 107:1242, 1994).     

Factors influencing normal blood pressure maintenance in young adults

Despite an alarming increase in the prevalence of hypertension among Chinese young adults, longitudinal studies investigating factors that affect the maintenance of normal blood pressure (BP) in this population are lacking. Our study aimed to address this knowledge gap. A total of 7100 participants from the Kailuan Study who had normal BP and were aged <30 years at their first physical examination between 2006 and 2016 were included in this study. Cox proportional hazards regression models were used to assess hazard ratios (HR), and 95% confidence intervals (CI) were calculated to assess the associations between influencing factors and the maintenance of normal BP in young adults. Analyses were stratified by sex. During the follow-up period (mean, 7.98 years), 1921 participants (27.06%) maintained normal BP. Higher education levels (HR, 1.11; 95% CI, 1.00–1.22), low salt intake (HR, 1.25; 95% CI, 1.04–1.51), being underweight (HR, 1.16; 95% CI, 1.02–1.31), and having normal weight (HR, 1.19; 95% CI, 1.01–1.39), normal blood glucose (HR, 1.22; 95% CI, 1.02–1.46), and no family history of hypertension (HR, 1.65; 95% CI, 1.41–1.92) at baseline were found to be associated with maintaining normal BP. Compared with female smokers, female non-smokers had 1.68 times higher odds of maintaining normal BP. This study identified factors that influence the maintenance of normal BP in the young population in China. This information can assist clinicians in establishing comprehensive and effective primary prevention measures for hypertension.