The initial angle of the maximum expiratory flow-volume curve: a novel start-of-test criteria of spirometry in children.

The aim of the present study was to define an initial angle called ß and to assess its diagnostic value for identifying poor-quality maneuvers in spirometry testing in children. Furthermore, its predictive equation or normal value was explored. Children aged 4-14 years with respiratory symptoms who underwent spirometry were enrolled. Based on the efforts labeled during maneuvering and the quality control criteria of the guidelines, children were categorized into good-quality and poor-quality groups. According to ventilatory impairment, children in the good-quality group were divided into three subgroups: normal, restricted, and obstructed. Angle ß was the angle between the line from the expiratory apex to the origin of coordinates and the x-axis of the maximal expiratory flow-volume (MEFV) curve. Demographic characteristics, angle ß, and other spirometric parameters were compared among groups. The diagnostic values of angle ß, forced expiratory time (FET), and their combination were assessed using receiver operating characteristic curves. Data from 258 children in the good-quality group and 702 healthy children in our previous study were used to further explore the predictive equation or normal value of angle ß. The poor-quality group exhibited a significantly smaller angle ß (76.44° vs. 79.36°; P < 0.001), significantly lower peak expiratory flow (PEF), FET, and effective FET (ETe), and significantly higher expiratory volume at peak flow rate (FEV-PEF) and ratio of extrapolated volume and forced vital capacity (EV/FVC) than the good-quality group. There was no significant difference in angle ß among the normal, restricted, and obstructed groups. Logistic regression analysis revealed that smaller angle ß and FET values indicated poor-quality MEFV curves. The combination of angle ß < 74.58° and FET < 4.91 s had a significantly larger area under the curve than either one alone. The normal value of angle ß of children aged 4-14 years was 78.40 ± 0.12°.   Conclusions: Angle ß contributes to the quality control evaluation of spirometry in children. Both angle ß < 74.58° and FET < 4.91 s are predictors of poor-quality MEFV curves, while their combination offers the highest diagnostic value. What is Known: • A slow start is one of the leading causes of poor-quality maximal expiratory flow-volume (MEFV) curves, which is a particularly prominent issue among children due to limited cooperation, especially those younger than 6 years old. • It is relatively difficult to differentiate between ventilatory dysfunction and poor cooperation when a slow start occurs in children; therefore, there is an urgent need for an objective indicator that is unaffected by ventilatory impairment to evaluate quality control of spirometry. What is New: • The initial angle ß, which was introduced at the ascending limb of the MEFV curve in the present study, has a certain diagnostic value for poor-quality MEFV curves in children. • Angle ß < 74.58° is a predictor of poor-quality MEFV curves, and its combination with FET < 4.91 s offers a higher diagnostic value.

Ratio of Maximal Inspiratory to Expiratory Flow Aids in the Separation of COPD from Asthma.

Patients who have chronic obstructive pulmonary disease (COPD) and bronchial asthma (BA) share symptoms such as, dyspnoea, cough and wheeze. Differentiating these diseases in the ambulatory setting can be challenging especially in older adult smokers who are being treated with a variety of medications. The objective of this study was to test the value of adding a maximal inspiratory manoeuvre to basic spirometry to differentiate COPD and BA. One hundred forty-three COPD patients and 142 BA patients had measurements of maximal inspiratory and expiratory flow during routine spirometry. Parameters from these tests were used to assess diagnostic accuracy using receiver-operating characteristic (ROC) analyses followed by logistic regression. The association of two independent parameters were analyzed using linear regression analyses. Results show that forced expiratory volume in one second/forced vital capacity (FEV1/FVC%) <62.4 was the best independent predictor to diagnose COPD. The combination of FEV1/FVC% <62.4 and the ratio of peak inspiratory flow/maximal expiratory flow at 50% FVC (PIF/MEF50) >3.06 significantly predicted COPD. Post-test probability for prediction of COPD was 82.0% when patients had both parameters. When asthmatic patients with a smoking history were compared with COPD patients, FEV1/FVC% <63.4 and PIF/MEF50 >3.29 were both independent predictors of COPD. The post-test probability for COPD was 94.4% when patients had both parameters. The association between FEV1/FVC% and PIF/MEF50 was significantly different between COPD and BA. In conclusion, the addition of the maximal inspiratory effort to routine pulmonary function measurements provides a simple test to help differentiate COPD and BA.

CT and radiographic evaluation of bronchial collapsibility at forced expiration in asymptomatic brachycephalic dogs.

Bronchial collapse due to bronchomalacia is an important cause of chronic coughing in dogs. Radiographic and CT evidence of bronchial collapse has previously been reported in healthy Beagle dogs under forced expiration. However, published studies in brachycephalic dog breeds that are prone to bronchial collapse are currently lacking. In the present prospective analytical experimental study, CT and radiography were used to measure the bronchial diameter and collapsibility of each pulmonary bronchus during end-expiratory, 5 mL/kg forced-expiratory, and 10 mL/kg forced-expiratory phases in 17 asymptomatic brachycephalic dogs and six healthy Beagle dogs. Bronchial collapsibility was significantly greater during forced expiration, than that at the end of expiration in both groups (P < .001). Bronchial collapsibility measurements of the left lung lobes and the right cranial, middle, and accessory lobes were significantly higher in asymptomatic brachycephalic dogs than those in healthy Beagle dogs, during all expiratory phases (P < .05). The higher bronchial collapsibility of brachycephalic dogs was also supported using CT multiplanar reconstruction images and radiography. In conclusion, radiographic and CT measures of bronchial collapsibility in asymptomatic brachycephalic dogs are higher than measures in healthy Beagle dogs. Therefore, measures of bronchial collapse in brachycephalic dogs should not be evaluated using the same baseline measures as those used for healthy Beagle dogs.

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.

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.

Angle ß of greater than 80° at the start of spirometry may identify high-quality flow volume curves.

BACKGROUND AND OBJECTIVE: The American Thoracic Society (ATS) and European Respiratory Society (ERS) emphasize a satisfactory start in maximal expiratory flow-volume (MEFV) curves and highlight subjective parameters: performance without hesitation and expiration with maximum force. We described a new parameter, angle ß for characterization of the start to the MEFV curve. METHODS: Subjects completed the MEFV curve at least three times and at least two curves met ATS/ERS quality. Subjects were divided into normal, restrictive and obstructive groups according to pulmonary function test results. The tangent line was drawn at the start of the MEFV curve's ascending limb to the x-axis and the angle ß between the tangent line and x-axis was obtained. The relationships between tangent of ß, pulmonary function parameters (PFPs) and anthropometric data were assessed. The MEFV curves with insufficient explosion at the start were considered as poor-quality MEFV curves. RESULTS: In 998 subjects with high-quality spirometry, although PFP varied in relation to the three aspects: the angle ß and its tangent were similar (P > 0.05), the tangent of ß did not correlate with PFP or anthropometric measurements (P > 0.05) and the lower limit of normal (LLN) of the angle ß was 80° in the group with high-quality spirometry (P < 0.05). Angle ß derived from poor-quality MEFV curves was smaller than that from good quality one (P < 0.05). CONCLUSION: Angle ß may function as a parameter to assess the expiratory efforts, which can be used to assess the quality of the MEFV curve start.

Graphic analysis of flow-volume curves: a pilot study.

BACKGROUND: Conventional spirometric parameters have shown poor correlation with symptoms and health status of chronic obstructive pulmonary disease (COPD). While it is well-known that the pattern of the expiratory flow-volume curve (EFVC) represents ventilatory dysfunction, little attempts have been made to derive quantitative parameters by analyzing the curve. In this study, we aimed to derive useful parameters from EFVC via graphic analysis and tried to validate them in patients with COPD. METHODS: Using Graphical Analysis 3.4 Vernier Software, we derived from the EFVC such parameters as area of obstruction (Ao), area of triangle (AT), area of rectangle (AR) and ratio of volume at 75 and 25% peak expiratory flow (PEF) (0.25/0.75 V). For validation, we reviewed clinical and spirometric data of 61 COPD patients from Seoul National University Airway Registry (SNUAR) and Korean obstructive Lung Disease (KOLD) cohorts. RESULTS: Of all parameters, only RV/TLC significantly correlated with scores from St. George's Respiratory Questionnaire (SGRQ) (r = 0.447, p = 0.037). Six-minute walking distance (6MWD) highly correlated with Ao/AR (r = -0.618, p = 0.005) and Ao/PEF (r = -0.581, p = 0.009) whereas neither FEV1 nor FEV1/FVC had significant correlation with 6MWD. CONCLUSIONS: Ao/AR and Ao/PEF are promising parameters which correlate well with the exercising capacity of COPD patients.

[Quality control for maximal expiratory flow-volume curve as a pulmonary function test in school-age children].

OBJECTIVE: To assess the quality control for the maximal expiratory flow-volume (MEFV) curve in school-age children. METHODS: Eight hundred and sixty-two children who had two or more MEFV manoeuvres were classified into ≥6-year-old (n=379), ≥8-year-old (n=210), ≥10-year-old (n=64), and 12-17-year-old groups (n=109). The parameters of quality control and concordance with quality control criteria for MEFV were compared between the two groups. In addition, patients who were diagnosed with asthma were classified into two groups, one with normal pulmonary function (n=155) and the other with abnormal pulmonary function (n=62), based on the results of spirometry. Differences in the parameters of quality control for spirometry were compared between the two groups. RESULTS: Eight hundred and sixty-two children underwent 2 367 MEFV manoeuvres, 97.8% of which met the start of test criterion for backward extrapolated volume (VBE) of less than 0.15 L, with the highest concordance in the ≥6-year-old group and the lowest concordance in the 12-17-year-old group. Three hundred and eighty-one children (44.2%) met the end of test criterion for forced expiratory time (FET) and the concordance in children over 10 years of age was lower than that in children under 10 years of age (P<0.05). Differences in two best forced expiratory volume in first second (FEV1) and forced vital capacity (FVC) manoeuvres were within 150 mL in 91.9% and 84.8%, respectively, of the children. The parameters of quality control for spirometry were better for asthmatic children with abnormal pulmonary function compared with asthmatic children with normal pulmonary function (P<0.05). CONCLUSIONS: Concordance with the start of test criteria and the manoeuvre repeatability criteria is high, whereas the concordance with the end of test criteria is low. It is suggested that the concordance with the FET criteria should be improved.

Partial versus maximal forced exhalations in COPD: enhanced signal detection for novel therapies.

BACKGROUND: Evaluation of novel compounds for COPD often relies on FEV1 for signal detection. Partial forced exhalations from end-tidal inspiration (PEFV) might complement FEV1 in identifying such a signal. We examined the prevalence of bronchodilator response (BDR) using PEFV and FEV1 in patients with COPD. METHODS: 110 consecutive COPD patients were tested prospectively with PEFV and maximal expiratory flow before and after inhalation of a short-acting ß2 agonist (salbutamol, 400 µg). Partial flow at 800 ml above residual volume was derived from the PEFV (PF800). Significant changes in PF800 and/or FEV1 were set at the upper 95% confidence interval after placebo (n = 28). RESULTS: Four groups were identified by the presence (+) or absence (-) of a BDR: Group 1 [PF800 (-)FEV1(-)] when no change was observed (n = 31), Group 2 [PF800(+)FEV1(-)] when PF800 alone improved (n = 31), Group 3 [PF800(-)FEV1(+)] when FEV1 alone improved (n = 26), and Group 4 [PF800(+)FEV1(+)] when both variables improved (n = 18). There were 35 non-responders in any parameter, and 75/110 subjects who showed a response in at least one parameter. The changes in PF800 and FEV1 were not correlated suggesting these assess different airway generations. CONCLUSIONS: The use of PF800 increased detection of a BDR in COPD compared to FEV1 alone and may reflect small airway responses. The PEFV maneuver is simple, repeatable and may avoid some of the theoretical disadvantages of FEV1. The role of PF800 for evaluating novel anti-inflammatory agents remains to be determined.

Effect of exercise-induced bronchoconstriction on the configuration of the maximal expiratory flow-volume curve in adults with asthma.

We determined the effect of exercise-induced bronchoconstriction (EIB) on the shape of the maximal expiratory flow-volume (MEFV) curve in asthmatic adults. The slope-ratio index (SR) was used to quantitate the shape of the MEFV curve. We hypothesized that EIB would be accompanied by increases in SR and thus increased curvilinearity of the MEFV curve. Adult asthmatic ( n  = 10) and non-asthmatic control subjects ( n  = 9) cycled for 6-8 min at 85% of peak power. Following exercise, subjects remained on the ergometer and performed a maximal forced exhalation every 2 min for a total 20 min. In each MEFV curve, the slope-ratio index (SR) was calculated in 1% volume increments beginning at peak expiratory flow (PEF) and ending at 20% of forced vital capacity (FVC). Baseline spirometry was lower in asthmatics compared to control subjects (FEV1 % predicted, 89.1 ± 14.3 vs. 96.5 ± 12.2% [SD] in asthma vs. control; p  < 0.05). In asthmatic subjects, post-exercise FEV1 decreased by 29.9 ± 13.2% from baseline (3.48 ± 0.74 and 2.24 ± 0.59 [SD] L for baseline and post-exercise nadir; p  < 0.001). At baseline and at all timepoints after exercise, average SR between 80 and 20% of FVC was larger in asthmatic than control subjects (1.48 ± 0.02 vs. 1.23 ± 0.02 [SD] for asthma vs. control; p < 0.005). This averaged SR did not change after exercise in either subject group. In contrast, post-exercise SR between PEF and 75% of FVC was increased from baseline in subjects with asthma, suggesting that airway caliber heterogeneity increases with EIB. These findings suggest that the SR-index might provide useful information on the physiology of acute airway narrowing that complements traditional spirometric measures.

Effect of carrying a weighted backpack on lung mechanics during treadmill walking in healthy men.

Weighted backpacks are used extensively in recreational and occupational settings, yet their effects on lung mechanics during acute exercise is poorly understood. The purpose of this study was to determine the effects of different backpack weights on lung mechanics and breathing patterns during treadmill walking. Subjects (n = 7, age = 28 ± 6 years), completed two 2.5-min exercise stages for each backpack condition [no backpack (NP), an un-weighted backpack (NW) or a backpack weighing 15, 25 or 35 kg]. A maximal expiratory flow volume curve was generated for each backpack condition and an oesophageal balloon catheter was used to estimate pleural pressure. The 15, 25 and 35 kg backpacks caused a 3, 5 and 8% (P < 0.05) reduction in forced vital capacity compared with the NP condition, respectively. For the same exercise stage, the power of breathing (POB) requirement was higher in the 35 kg backpack compared to NP (32 ± 4.3 vs. 88 ± 9.0 J min(-1), P < 0.05; respectively). Independent of changes in minute ventilation, end-expiratory lung volume decreased as backpack weight increased. As backpack weight increased, there was a concomitant decline in calculated maximal ventilation, a rise in minute ventilation, and a resultant greater utilization of maximal available ventilation. In conclusion, wearing a weighted backpack during an acute bout of exercise altered operational lung volumes; however, adaptive changes in breathing mechanics may have minimized changes in the required POB such that at an iso-ventilation, wearing a backpack weighing up to 35 kg does not increase the POB requirement.

[A comparative study between inflation and deflation pressure-volume curve in determining the optimal positive end-expiratory pressure].

OBJECTIVE: To determine the optimal positive end-expiratory pressure (PEEP) according to inflation and deflation pressure-volume curve (P-V curve) in patients with acute respiratory distress syndrome (ARDS). METHODS: ARDS models were reproduced in 20 dogs, and they were randomly divided into two groups. In both groups, Levenberg-Marquardt iterative algorithm was employed using software to explore parameters fitting with Boltzmann formula, by which the real inflection point of pressure (Pinf d) in deflation limb or lower inflection point pressure (PLip) in inflation limb on P-V curve were defined. For the control group (inflation curve) P-V curve of PLip + 2 cm H(2)O [1 cm H(2)O = 0.098 kPa] was applied as the best PEEP value. In the experimental group (deflation curve) the Pinf d was taken as the best PEEP value. The heart rate (HR), blood pressure (BP), fingertip pulse oxygen saturation [SpO(2)], static lung compliance (Cst), arterial partial pressure of oxygen [PaO(2)] and arterial partial pressure of carbon dioxide [PaCO(2)] were monitored at 0, 2, 6, 12, 24 and 48 hours. RESULTS: Oxygenation index increased significantly both in control and experimental groups. In experimental group, oxygenation index (mm Hg, 1 mm Hg = 0.133 kPa) of 12, 24 and 48 hours was respectively significantly higher than that of the control group (12 hours: 177.63 ± 8.94 vs. 165.60 ± 8.90, 24 hours: 194.19 ± 10.67 vs. 168.70 ± 10.60, 48 hours: 203.15 ± 13.21 vs. 171.26 ± 9.21, all P < 0.01). Cst [ml/cm H(2)O] at 2, 6, 12, 24 and 48 hours was respectively higher than that of the control group (2 hours: 41.00 ± 4.17 vs. 36.20 ± 3.90, 6 hours: 44.00 ± 4.65 vs. 36.88 ± 3.39, 12 hours: 46.92 ± 5.47 vs. 37.92 ± 3.10, 24 hours: 42.83 ± 8.97 vs. 37.92 ± 3.09, 48 hours: 42.64 ± 9.04 vs. 37.97 ± 2.98, P < 0.05 or P < 0.01). CONCLUSION: Determining optimal PEEP for ARDS with deflation P-V curve was better than that of inflation curve.

Validation of a diagnostic score for the diagnosis of autoinflammatory diseases in adults.

Most autoinflammatory disorders typically come out in the pediatric population, although a limited number of patients may experience disease onset during adulthood. To date, a late disease onset has been described only in familial Mediterranean fever, caused by mutations in the MEFV gene, and in tumor necrosis factor receptor-associated periodic syndrome, caused by mutations in the TNFRSF1A gene. The relative rarity and lack of information on adult-onset autoinflammatory diseases make it likely that mutations will be found in an even smaller percentage of cases. With the aim of improving the genetic diagnosis in adults with suspected autoinflammatory disorders, we recently identified a set of variables related to the probability of detecting gene mutations in MEFV and TNFRSF1A and, in addition, we have also proposed a diagnostic score for identifying those patients at high risk of carrying mutations in these genes. In the present study we evaluated the preliminary score sensitivity and specificity on a wider number of patients in order to validate the goodness of fit of the model. Two hundred and nineteen consecutive patients with a clinical history of periodic fever attacks were screened for mutations in MEFV and TNFRSF1A genes; detailed information about family/personal history and clinical manifestations were also collected. For the validation of the score we considered data both from the 110 patients used to build the preliminary diagnostic score and from the additional 219 patients enrolled in the present study, for a total number of 329 patients. Early age at disease onset, positive family history for recurrent fever episodes, thoracic pain, abdominal pain and skin rash, which are the variables that had previously been shown to be significantly associated with a positive genetic test result (12), were used for validation. On univariate analysis the associations with a positive genetic test were: age at onset (odds ratio [OR] 0.43, p=0.003), positive family history for recurrent fever episodes (OR 5.81, p<0.001), thoracic pain (OR 3.17, p<0.001), abdominal pain (OR 3.80, p<0.001) and skin rash (OR 1.58, p=0.103). The diagnostic score was calculated using the linear combination of the estimated coefficients of the logistic multivariate model (cut-off equals to 0.24) revealing good sensitivity (0.778) and good specificity (0.718). In conclusion, our score may serve in the diagnostic evaluation of adult patients presenting with recurrent fever episodes suspected of having an autoinflammatory disorder, helping identify the few subjects among them who may be carriers of mutations in MEFV and TNFRSF1A genes.

Supramaximal flows: comparison between asthmatics and patients with chronic obstructive pulmonary disease.

BACKGROUND: The major motive that prompted this study was to investigate whether or not the differences in supramaximal flow (SF) behavior between patients suffering from asthma and patients suffering from chronic obstructive pulmonary disease (COPD) might aid in clarifying the differences in the physiopathology of the two diseases. OBJECTIVES: The aim of the present study was therefore to compare SFs in asthma and COPD patients with similar degrees of air-flow limitation. METHODS: Twelve asthmatic patients were individually matched with 12 COPD patients by forced expiratory volume during the first second (FEV(1)) as a percent (±5%) of the reference value (ΔFEV(1)) and by age (±4 years). The subjects performed baseline maximal expiratory flow-volume curves (MEFV) and then repeated the same maneuvers through a valve that occluded the air flow 6 times per second with an open/closed time ratio of 4/1. We then plotted an envelope of the expiration-interrupted curve passing through the SF peaks, measured the increase in flow at 50% of the forced vital capacity between the baseline curve and the envelope curves (ΔVmax(50)), and compared the FEV(1) of the interrupted curve to the FEV(1) obtained from control MEFV curves (ΔFEV(1)). RESULTS: We found significantly higher values for ΔVmax(50) (p < 0.03) and ΔFEV(1) (p < 0.01) in the asthmatics compared to the COPD patients. CONCLUSIONS: The differences reported here are best explained by a greater preservation of elastic recoil pressure at a similar degree of air-flow limitation in the asthmatics than in the COPD patients.

Use of flow-volume curves to predict oral appliance treatment outcome in obstructive sleep apnea: a prospective validation study.

PURPOSE: Flow-volume curves have been shown to relate to upper airway physiology during sleep and may be useful for predicting the response to treatment of obstructive sleep apnea (OSA) with mandibular advancement splints (MAS). The aim of this study was to prospectively assess the potential clinical utility of a previously derived prediction method using flow-volume curves performed during wakefulness. METHODS: Patients with newly diagnosed OSA interested in undertaking treatment with a custom-made MAS were approached to participate in the study. Response to treatment was defined by a 50% or greater reduction in the apnea-hypopnea index. Flow-volume curves were performed in the erect position prior to construction of the MAS. RESULTS: Flow-volume curves were performed in 35 patients. Of these, 25 patients were responders, and 10 patients were non-responders. A combined cut-off of an inspiratory flow rate at 50% of vital capacity (MIF50) less than 6.0 L/s and a ratio of the expiratory flow rate at 50% of vital capacity to MIF50 of greater than 0.7 correctly classified 48.6% of the patients. It had a sensitivity of 36.0%, specificity of 80.0%, positive predictive value of 81.8%, and negative predictive value of 33.3%. CONCLUSIONS: These results suggest that the previously derived prediction model, using flow-volume curves performed during wakefulness, was not sufficient to reliably predict the response to treatment of OSA with MAS. A combination of a functional assessment using flow-volume curves and a structural evaluation of the upper airway with imaging modalities may result in a prediction model with better performance characteristics.

[New parameters "average flow" and "acceleration wave": comparison with current parameters in the flow volume curve].

AIM: The flow volume curve is an essential test method for diagnosis and treatment of the respiratory diseases. However, this curve depends on patient's continuous effort toward optimal expiration and it has been reported that differences in this effort may possibly result in error in flow speed. To overcome the potential error, we devised the "average flow" and the "acceleration wave" that comprehends the overall data of the expiration flow speed, and have done comparative analysis with the current parameters. METHODS: The average flow is derived by taking the integration from the beginning of the expiration to the end, and divides the integrated value by the number of data counts. Additionally, the acceleration wave is derived by taking the second degree derivative of the flow volume curve. RESULTS: The average flow showed strong correlation among healthy male and healthy female V50, obstructive index and criteria for COPD severity patients. Also, we were able to obtain the maximum acceleration from the acceleration wave. Significantly, this value showed strong correlation with the COPD patient's peak flow and average flow/peak flow. CONCLUSIONS: If the ratio of the average flow and the peak flow is below a fixed criterion, it is an obstructive lung disease, if it is above, it is possible to detect restrictive lung disease. Since the maximum acceleration rate of the acceleration wave is derived by the start of the expiration nearly up to 100 ml, it is especially possible to detect minute changes of the flow speed in large respiratory tract.

Factors for the Variability of Three Acceptable Maximal Expiratory Flow-Volume Curves in Chronic Obstructive Pulmonary Disease.

BACKGROUND: Generally, the maximal expiratory flow-volume (MEFV) curve must be measured for the diagnosis and staging of chronic obstructive pulmonary disease (COPD). As this test is effort dependent, international guidelines recommend that three acceptable trials are required for each test. However, no study has examined the magnitude and factors for the variability in parameters among three acceptable trials. METHODS: We evaluated the intra-individual variations in several parameters among three acceptable MEFV curves obtained at one-time point in patients with COPD (n = 28, stage 1; n = 36, stage 2; n = 21, stages 3-4). Next, the factors for such variations were examined using forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC). RESULTS: The averages of coefficient of variation (CV) for FEV1 and FVC were 2.0% (range: 1.0-3.0%) and 1.6% (0.9-2.2%), respectively. Both parameters were significantly better than peak expiratory flow rate, forced expiratory flow at 50% of expired FVC, and forced expiratory flow at 75% of expired FVC (CVs: 5.0-6.9%). A higher spirometric stage was significantly associated with higher CVs for FVC and FEV1, and older age was significantly correlated with a higher variation in FEV1 alone. Furthermore, a significantly inverse association was observed between emphysema severity, and the CVs for FEV1, but not that for FVC, regardless of spirometric stage. CONCLUSION: Both FVC and FEV1 are highly reproducible; nevertheless, older age, lower FEV1 at baseline, and non-emphysema phenotype are factors for a higher variability in FEV1 in patients with COPD.

Thoracic gas compression during forced expiration is greater in men than women.

Intrapleural pressure during a forced vital capacity (VC) maneuver is often in excess of that required to generate maximal expiratory airflow. This excess pressure compresses alveolar gas (i.e., thoracic gas compression [TGC]), resulting in underestimated forced expiratory flows (FEFs) at a given lung volume. It is unknown if TGC is influenced by sex; however, because men have larger lungs and stronger respiratory muscles, we hypothesized that men would have greater TGC. We examined TGC across the "effort-dependent" region of VC in healthy young men (n = 11) and women (n = 12). Subjects performed VC maneuvers at varying efforts while airflow, volume, and esophageal pressure (POES ) were measured. Quasistatic expiratory deflation curves were used to obtain lung recoil (PLUNG ) and alveolar pressures (i.e., PALV  = POES -PLUNG ). The raw maximal expiratory flow-volume (MEFVraw ) curve was obtained from the "maximum effort" VC maneuver. The TGC-corrected curve was obtained by constructing a "maximal perimeter" curve from all VC efforts (MEFVcorr ). TGC was examined via differences between curves in FEFs (∆FEF), area under the expiratory curves (∆AEX ), and estimated compressed gas volume (∆VGC) across the VC range. Men displayed greater total ∆AEX (5.4 ± 2.0 vs. 2.0 ± 1.5 L2 ·s-1 ; p < .001). ∆FEF was greater in men at 25% of exhaled volume only (p < .05), whereas ∆VGC was systematically greater in men across the entire VC (main effect; p < .05). PALV was also greater in men throughout forced expiration (p < .01). Taken together, these findings demonstrate that men display more TGC, occurring early in forced expiration, likely due to greater expiratory pressures throughout the forced VC maneuver.

Curvilinearity of a Maximum Expiratory Flow-Volume Curve: A Useful Indicator for Assessing Airway Obstruction in Children With Asthma.

BACKGROUND: Lung function parameters are used as signs in the diagnosis and evaluation of asthma; however, their sensitivity and specificity are not ideal. We calculated and combined angle ß with lung function parameters to identify the ideal indicator. OBJECTIVE: We aimed to identify an ideal indicator for evaluating the severity of airway obstruction in children with asthma. METHODS: In total, 151 school-age children diagnosed with asthma were selected as the asthma group, and 106 healthy children were selected as the control group. The subjects were divided into the exacerbation group, chronic persistent group, and clinical remission group. Furthermore, the subjects were classified into mild and moderate groups or severe and critical groups. Angle ß was calculated in each group. A receiver operating characteristic curve analysis was performed to determine the cutoff values of angle ß and lung function parameters that together provided high sensitivity and specificity for airway obstruction evaluation in children with asthma. RESULTS: The mean value of angle ß in the asthma group was significantly smaller than that in the control group (178.18° and 196.72°, respectively, P < .001). More exacerbations or greater severity corresponded to smaller angle ß values (P < .001). The best cutoff value of angle ß was 189.43°, and the area under the receiver operating characteristic curve of angle ß was 0.877, which is greater than the area under the receiver operating characteristic curve of FEV1, forced expiratory flow (FEF) at 75% vital capacity (FEF25%), and FEF at 50% vital capacity (FEF50%), but smaller than the area under the receiver operating characteristic curve of FEF75% and FEV1/FVC%. Interestingly, combining these measures can enhance the sensitivity and specificity in assessing airway obstruction. CONCLUSIONS: Angle ß was a useful indicator for assessing airway obstruction. Furthermore, angle ß combined with FEV1, FEV1/FVC%, FEF25%, FEF50%, and FEF75% can enhance the sensitivity and specificity of airway obstruction evaluations.

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 ß = 0.43, P < 0.0001) independent of other spirometric indices. The Obstructive Index is a useful spirometric index that reflects the extent of emphysema.