Control of the expiratory flow in a lung model and in healthy volunteers with an adjustable flow regulator: a combined bench and randomized crossover study

Background Pursed-lips breathing (PLB) is a technique to attenuate small airway collapse by regulating the expiratory flow. During mandatory ventilation, flow-controlled expiration (FLEX), which mimics the expiratory flow course of PLB utilizing a digital system for measurement and control, was shown to exert lung protective effects. However, PLB requires a patient’s participation and coordinated muscular effort and FLEX requires a complex technical setup. Here, we present an adjustable flow regulator to mimic PLB and FLEX, respectively, without the need of a patient’s participation, or a complex technical device. Methods Our study consisted of two parts: First, in a lung model which was ventilated with standard settings (tidal volume 500 ml, respiratory rate 12 min−1, positive end-expiratory pressure (PEEP) 5 cmH2O), the possible reduction of the maximal expiratory flow by utilizing the flow regulator was assessed. Second, with spontaneously breathing healthy volunteers, the short-term effects of medium and strong expiratory flow reduction on airway pressure, the change of end-expiratory lung volume (EELV), and breathing discomfort was investigated. Results In the lung model experiments, expiratory flow could be reduced from − 899 ± 9 ml·s−1 down to − 328 ± 25 ml·s−1. Thereby, inspiratory variables and PEEP were unaffected. In the volunteers, the maximal expiratory flow of − 574 ± 131 ml·s−1 under baseline conditions was reduced to − 395 ± 71 ml·s−1 for medium flow regulation and to − 266 ± 58 ml·s−1 for strong flow regulation, respectively (p < 0.001). Accordingly, mean airway pressure increased from 0.6 ± 0.1 cmH2O to 2.9 ± 0.4 cmH2O with medium flow regulation and to 5.4 ± 2.4 cmH2O with strong flow regulation, respectively (p < 0.001). The EELV increased from baseline by 31 ± 458 ml for medium flow regulation and 320 ± 681 ml for strong flow regulation (p = 0.033). The participants rated breathing with the flow regulator as moderately uncomfortable, but none rated breathing with the flow regulator as intolerable. Conclusions The flow regulator represents an adjustable device for application of a self-regulated expiratory resistive load, representing an alternative for PLB and FLEX. Future applications in spontaneously breathing patients and patients with mandatory ventilation alike may reveal potential benefits. Trial registration: DRKS00015296, registered on 20th August, 2018; URL: https://www.drks.de/drks_web/setLocale_EN.do.

INFLUENCE OF SEX, AGE AND BODY MASS INDEX ON SOME FUNCTIONA INDICES OF PULMONARY VENTILATION IN PHYSICALLY ACTIVE CHILDREN

Purpose: The purpose of the present study is to examine the impact of age, sex and body mass index (BMI) on some indices of the pulmonary ventilation in healthy children actively practicing sport, between 11 and 14 years of age, living in Plovdiv, Bulgaria. Materials and methods: A group of 22 healthy volunteers (boys, n=14 and girls, n=8) with high level physical activity underwent a functional test for the evaluation of pulmonary ventilation. In order to assess the influence of age, BMI and sex on some indices of pulmonary ventilation, they were divided into the following groups: in accordance with the age - group 11-12 years old (n=14) and group 13-14 years old (n=8); in accordance with the BMI group < 20 kg/m2 (n=14) and BMI group >20 kg/m2 (n=8) and in accordance with the sex – boys group (n=14) and girls group (n=8). The results are presented as X±SD. The data has been analyzed with Independent Samples Test (t-test) (SPSS v. 13. 0). The difference at P<0.05 was accepted as significant. Results: We did not find significant differences in most of the indices between the groups by age, body mass index and sex. Although there was higher maximum pulmonary ventilation and higher peak (maximal) expiratory flow in boys compared with the girls. Conclusion: Despite the good health condition and high level of physical activity, we found out higher maximum pulmonary ventilation and higher peak (maximal) expiratory flow in boys as compared with the girls.

Fractional exhaled nitric oxide could identify early spirometry change in clinically suspected asthma patients without airway obstruction

Fractional exhaled nitric oxide (FeNO) has been proposed as a non-invasive biomarker for allergic inflammation seen in asthma. The aim of this study was to assess the ability of FeNO to discriminate spirometry and lung volume measurements between those with and without airway obstruction among subjects with clinically suspected asthma. A retrospective study was conducted. Diagnostic evaluations including spirometry and FeNO testing (NO electrochemical equipment: NIOX VERO; Aerocrine AB, Solna, Sweden) were performed in all subjects. Airway obstruction was defined according to the Standardization of Spirometry of the American Thoracic Society (ATS)/European Respiratory Society (ERS), and 2014 recommendations of the Chinese National Guidelines of Pulmonary Function Test. It was used the Student t test for analysis of continuous variables and the χ2 test for analysis of discrete variables including FeNO levels and lung function metrics. Of the 138 subjects with clinically suspected asthma, airway obstruction was found in 61. There was no significant difference in the mean FeNO levels among subjects with or without airway obstruction ( p = 0.241) among un-selected subjects. Likewise, there was no difference in the FeNO levels between aged (>50 years) and younger subjects (⩽50 years) ( p = 0.804). A significant proportion of subjects had a normal FeNO level (<25 part per billion, ppb) in spite of having airway obstruction (39/138), 25 had an elevated FeNO level (⩾25 ppb) in spite of having no airway obstruction (25/138). Additionally, the airway-obstructed subjects with increased FeNO level had comparable spirometry to those with normal FeNO level ( p > 0.05). However, among subjects without airway obstruction, the forced expiratory volume in 1 s (FEV1)/predicted (pred), maximal expiratory flow at 25% of forced vital capacity (FVC) (MEF25%)/pred, maximal expiratory flow at 50% of FVC (MEF50%)/pred and maximum mid-expiratory flow (MMEF)/pred were significantly lower in the FeNO ⩾ 25 ppb group compared to those in the FeNO < 25 ppb group. These analyses indicated that increased FeNO levels could help to determinate early spirometry change within clinically suspected asthma subjects without airway obstruction. It is highlighted the importance of FeNO as a phenotype associated with an increased risk of airway obstruction in some subjects in this study.

Reductions in Cardiopulmonary Disease Risk Following Calisthenic Concurrent Aerobic and Resistance Training in Young Adults in a Low Resource Setting

Background: Studies have demonstrated that young adults, especially in low- to middle-income countries, are increasingly susceptible to unfavorable alterations in body composition during their transition from adolescence to adulthood. This places young adults at an increased risk for numerous chronic diseases, such as cardiovascular, and/or pulmonary diseases. Objectives: This study aimed to determine if concurrent aerobic and resistance calisthenic training could reduce cardiopulmonary disease risk in young adults in a low resource setting. Methods: Thirty young adult males were randomly assigned to either a six-week non-exercising control group (NON) or concurrent aerobic or resistance training group (CON) that engaged in three, non-consecutive, 60-minute exercise sessions using a combination of 4 - 5 progressive resistance training exercises for two sets of 15 - 20 repetitions and 30 minutes of aerobic exercises at a rating of perceived exertion of 9 - 15. This study assessed anthropometry (body mass, stature, body mass index waist-to-hip ratio, waist-to-stature ratio, sum of skinfolds, percentage body fat, fat mass, fat free mass and conicity index) and lung function (forced vital capacity (FVC), forced expired volume in one second (FEV1), forced expiratory volume in one second/forced vital capacity ratio (FEV1/FVC), peak expiratory flow (PEF), maximal expiratory flow at 75% (MEF75%), maximal expiratory flow at 50% (MEF50%) and maximal expiratory flow at 25 (MEF25%). Results: Concurrent training resulted in significant (P ≤ 0.05) improvements in waist-to-hip ratio (0.94 ± 0.04 to 0.92 ± 0.05; P = 0.042), fat free mass (57.46 ± 9.16 to 58.21 ± 8.65 kg; P = 0.018), percentage body fat (14.56 ± 5.96 to 13.24 ± 5.77%, P = 0.006), fat mass (10.22 ± 5.31 to 9.29 ± 5.17 kg; P = 0.008), sum of skinfolds (96.22 ± 35.64 to 87.67 ± 32.15 mm; P = 0.004), PEF (5.06 ± 2.04 to 6.57 ± 2.51 L; P = 0.018), MEF75% (4.78 ± 2.01 to 6.24 ± 1.99 L.sec-1; P = 0.026), MEF50% (4.08 ± 1.20 to 5.24 ± 1.44 L.sec-1; P = 0.043) and MEF25% (2.66 ± 0.63 to 3.31 ± 1.87 L.sec-1; P = 0.038). Conclusions: The findings support the feasibility and efficacy of a simple and inexpensive concurrent aerobic and resistance training program to simultaneously improve body composition and lung function in an attempt to curb the increasing incidence of overweight/obesity and associated lung dysfunction in young adults in a low resource setting.

Reference value for expiratory time constant calculated from the maximal expiratory flow-volume curve

Background The expiratory time constant (RCEXP), which is defined as the product of airway resistance and lung compliance, enable us to assess the mechanical properties of the respiratory system in mechanically ventilated patients. Although RCEXP could also be applied to spontaneously breathing patients, little is known about RCEXP calculated from the maximal expiratory flow-volume (MEFV) curve. The aim of our study was to determine the reference value for RCEXP, as well as to investigate the association between RCEXP and other respiratory function parameters, including the forced expiratory volume in 1 s (FEV1)/ forced vital capacity (FVC) ratio, maximal mid-expiratory flow rate (MMF), maximal expiratory flow at 50 and 25% of FVC (MEF50 and MEF25, respectively), ratio of MEF50 to MEF25 (MEF50/MEF25). Methods Spirometric parameters were extracted from the records of patients aged 15 years or older who underwent pulmonary function testing as a routine preoperative examination before non-cardiac surgery at the University of Tokyo Hospital. RCEXP was calculated in each patient from the slope of the descending limb of the MEFV curve using two points corresponding to MEF50 and MEF25. Airway obstruction was defined as an FEV1/FVC and FEV1 below the statistically lower limit of normal. Results We retrospectively analyzed 777 spirometry records, and 62 patients were deemed to have airway obstruction according to Japanese spirometric reference values. The cut-off value for RCEXP was 0.601 s with an area under the receiver operating characteristic curve of 0.934 (95% confidence interval = 0.898–0.970). RCEXP was strongly associated with FEV1/FVC, and was moderately associated with MMF and MEF50. However, RCEXP was less associated with MEF25 and MEF50/MEF25. Conclusions Our findings suggest that an RCEXP of longer than approximately 0.6 s can be linked to the presence of airway obstruction. Application of the concept of RCEXP to spontaneously breathing subjects was feasible, using our simple calculation method.

Analysis of maximal expiratory flow-volume curves in adult survivors of preterm birth

Adult survivors of very preterm (≤32 wk gestational age) birth without (PRE) and with bronchopulmonary dysplasia (BPD) have variable degrees of airflow obstruction at rest. Assessment of the shape of the maximal expiratory flow-volume (MEFV) curve in PRE and BPD may provide information concerning their unique pattern of airflow obstruction. The purposes of the present study were to 1) quantitatively assess the shape of the MEFV curve in PRE, BPD, and healthy adults born at full-term (CON), 2) identify where along the MEFV curve differences in shape existed between groups, and 3) determine the association between an index of MEFV curve shape and characteristics of preterm birth (i.e., gestational age, mass at birth, duration of oxygen therapy) in PRE and BPD. To do so, we calculated the average slope ratio (SR) throughout the effort-independent portion of the MEFV curve and at increments of 5% of forced vital capacity (FVC) between 20 and 80% of FVC in PRE ( n = 19), BPD ( n = 25), and CON ( n = 20). We found that average SR was significantly higher in PRE (1.34 ± 0.35) and BPD (1.33 ± 0.45) compared with CON (1.03 ± 0.22; both P < 0.05) but similar between PRE and BPD ( P = 0.99). Differences in SR between groups occurred early in expiration (i.e., 20–30% of FVC). There was no association between SR and characteristics of preterm birth in PRE and BPD groups (all P > 0.05). The mechanism(s) of increased SR during early expiration in PRE/BPD relative to CON is unknown but may be due to differences in the structural and mechanical properties of the airways.

The Concavity of the Maximal Expiratory Flow–Volume Curve Reflects the Extent of Emphysema in Obstructive Lung Diseases

A concave-shaped maximal expiratory flow-volume (MEFV) curve is a spirometric feature in chronic obstructive pulmonary disease (COPD). The MEFV curve is characterized by an increase in the Obstructive Index, which is defined as a ratio of forced vital capacity to the volume-difference between two points of half of the peak expiratory flow on the MEFV curve. We hypothesized that the Obstructive Index would reflect the severity of emphysema in patients with COPD and asthma-COPD overlap (ACO). Thus, the aim of this retrospective study was to evaluate whether the Obstructive Index on spirometry is associated with the extent of emphysema on computed tomography (CT) in patients with COPD, ACO, and asthma (N = 65, 15, and 53, respectively). The percentage of low-attenuation volume (LAV%) and wall area (WA%) were measured on CT. The Obstructive Index was higher in patients with COPD and ACO than in those with asthma. Spearman correlation showed that a greater Obstructive Index was associated with a higher LAV%, but not WA%. Multivariate analysis showed that Obstructive Index was associated with LAV% (standardized β = 0.43, P < 0.0001) independent of other spirometric indices. The Obstructive Index is a useful spirometric index that reflects the extent of emphysema.