Body plethysmographic study of specific airway resistance in a sample of healthy adults

Background and objective: sRaw (specific airway resistance) is a corrected index (Raw multiplied by thoracic gas volume) that describes airway behaviour regardless of lung volume. Normal values of sRaw in adult subjects have never been formally defined. To establish sRaw interpretation criteria and to define a range of reference values, we evaluated variability, reproducibility and reliability of sRaw measurements in a group of healthy adults. Methods: We analysed 517 subjects of both genders, aged 18–65 (group A), and to assess the reproducibility of the measurements, we investigated intra‐individual variation and potential daily and weekly sRaw rhythms in a subgroup of 18 co‐operative healthy subjects (group B). Results: In group A, there was no pattern of association between any of the considered anthropometric parameters; mean sRaw was higher in men (6.24 vs 5.95 cmH₂O s in females; P = 0.0128), but when the data were stratified by age, gender‐related differences were only found in the group aged 46–60 (males 6.45 cmH₂O s, females 6.01 cmH₂O s; P = 0.0219). In group B, there was no statistically significant, time‐dependent variation during the single tests, nor any circadian or weekly rhythm. Conclusions: sRaw is a reliable parameter; therefore, we propose that the lower and upper 95% confidence limits should be considered as reference values for adults of both genders, regardless of age. The availability of reference values may be useful in clinical practice and research.     

New predictive equations for spirometric reference values and comparison with Morris equation in a Korean population

Background and objective:   The clinical importance of the differences between actual and predicted spirometric indices in non-Western populations is poorly defined. This study evaluated the differences between the spirometric values derived from Morris equation, traditionally used in South Korea, and the actual values, in the classification and detection of patients with respiratory diseases, and developed new predictive equations for the calculation of reference spirometric values for healthy Koreans.
Methods:   Data derived from a subset of the population who completed the initial baseline survey of the Korean Health and Genome Study were used to develop new predictive equations for spirometric reference values, using multiple linear regression. The effects of the new equations relative to those of Morris on the detection and classification of patients with respiratory diseases were then evaluated.
Results:   In total, 9999 people completed the baseline survey; a subgroup of 1314 met the study inclusion criteria and were used to develop the new predictive equations. Morris equation are 53.8% less accurate in detecting people with restrictive disorders and 15.8% less accurate in estimating the severity of COPD than the newly derived equations, although the differences between values derived from the traditional equations and values from the new equations were as small as 3.3–7.6%.
Conclusions:   The use of spirometric reference values that underestimate the actual parameters, despite the small differences, may have a significant influence on the detection of patients with restrictive disorders and the staging of COPD.     

Specific airway resistance is a better outcome parameter in bronchial provocation testing compared to FEV1 in patients with bronchial asthma

Objectives: Asthma is a chronic inflammatory disease characterized by airway hyperresponsiveness (AHR). A bronchial provocation test (BPT) is used to test for AHR. However forced expiratory volume in one second (FEV₁), used as outcome parameter is effort-related, in contrast to specific airway resistance (sRaw). This research was conducted to provide insight in the usefulness of sRaw as an outcome parameter in BPT. Methods: A total of 85 patients performing a BPT were included in the study. Bronchial reactivity was defined as the provocative dosage or provocative concentration causing a 20% decrease in FEV1 (PC-20) or a 100% increase in sRaw (PC+100). Results: No significant response in either FEV₁ or sRaw was found in 20 patients (24%). Twenty-nine patients (34%) only had a positive response for sRaw; 24 out of these 29 patients recognized their symptoms. 36 patients (42%) showed a positive response for both PC-20 and PC + 100. Conclusions: Twenty-nine patients (34%) showed a significant increase in sRaw without a fall in FEV₁. As performing sRaw is not a routine investigation, these patients are at risk of being excluded from a diagnosis of asthma. We suggest performing sRaw for patients without a fall in FEV₁ during BPT when they report recognizable symptoms.     

Effect of endotracheal tube size on airway resistance and dynamic lung compliance

There are different results on the effect of endotracheal tube (ETT) size on respiratory mechanics in patients undergoing mechanical ventilation, and there are few reports in adult laparoscopic surgery. The aim of this study was to investigate the effect of ETT size on airway resistance (RAW) and dynamic lung compliance (COMPL) in patients undergoing laparoscopic colorectal surgery. Seventy-two patients undergoing laparoscopic radical surgery for colorectal cancer under general anesthesia with endotracheal intubation were selected and divided into 3 groups (n = 24) using the random number table method Group A (ETT ID 7.0), Group B (ETT ID 7.5), and Group C (ETT ID 8.0). After mechanical ventilation, intraoperative RAW and COMPL were monitored in each of the 3 groups. In the non-pneumoperitoneal state, RAW in group ID7.0 is significantly higher than this in group ID7.5 and group ID8.0 (P < .05); the RAW between the 2 groups with ID7.5 and ID8.0 was not statistically significant (P > .05). The difference of COMPL between the 3 groups was statistically significant (P < .05); the COMPL of Group ID7.0 is lower than Group ID7.5, and Group ID7.5 is lower than Group ID8.0. In the pneumoperitoneal state, the RAW between ID7.0 group and ID8.0 group was statistically significant, the RAW difference between ID7.0 group and ID7.5 group, ID7.5 group and ID8.0 group not statistically significant (P > .05);the COMPL between the 3 groups was not statistically significant (P > .05). In the non-pneumoperitoneal state, the smaller the ETT internal diameter within a certain range, the higher RAW and the lower COMPL; in the pneumoperitoneal state, the RAW with the ID7.0 ETT was higher than that with the ID8.0 ETT, and the ETT size within a certain range had no effect on COMPL.     

Normative reference values for lung transfer factor in Isfahan, Iran

OBJECTIVES AND BACKGROUND: Transfer factor or carbon monoxide diffusing capacity (DL(CO)) is a particularly valuable test of the appropriateness of gas exchange across the alveolocapillary membrane. The purpose of this study is to derive predictive equations for DL(CO) and its derivative volume-corrected DL(CO) (DL(CO)/VA) measured by single-breath method in a large non-smoking population sample in Isfahan. METHODOLOGY: We evaluated 1429 randomly selected subjects (732 men, aged 5-85 years). Gender-specific linear prediction equations were developed by multiple regression analysis; with measured DL(CO), and DL(CO)/VA values (mmol/min/kPa), as dependent variables regressed against age (A), height (H) and body surface area (BSA). RESULTS: For both genders, age had negative effects on DL(CO), while height had a positive effect on DL(CO) and DL(CO)/VA (P < 0.01). The prediction equations for DL(CO) and DL(CO)/VA are: '0.152 x height - 0.056 x age - 11.595' and '-0.12 x age + 2.467', for men and: '-0.035 x age - 0.133 x height - 10.707' and '-0.012 x age - 0.02 x height + 2.755', for women, respectively. CONCLUSIONS: Our results therefore provide an original frame of reference for either DL(CO) or DL(CO)/VA in Iranian population, obtained from a standardized single-breath technique.     

Effect of electronic compensation on plethysmographic airway resistance measurements

OBJECTIVES: To compare the performance of a plethysmograph which incorporated electronic compensation (Jaeger) to one which incorporated a heated humidified breathing system (Hammersmith plethysmograph). WORKING HYPOTHESIS: The performance of a plethysmograph which incorporated electronic compensation would be impaired compared to that which incorporated a heated humidified system. STUDY DESIGN: In vitro and in vivo comparison. PATIENT SELECTION: Eleven children, median postnatal age 13 (range 5-15) months. METHODS: In vitro, the plethysmographs were assessed using known resistances (1.94, 4.85, and 6.80 kPa, equivalent to 20, 50, and 70 cm H(2)O/L/sec, respectively). In vivo, comparison was made of the results of children studied in both plethysmographs. RESULTS: In vitro, the resistance results of the two plethysmographs were similar to each other and to the known resistances. In vivo, the median "effective" airways resistance result of the Jaeger (4.15 kPa/L/sec) was significantly higher than the inspiratory resistance of the Hammersmith plethysmograph (3.0 kPa/L/sec), but the median inspiratory resistances of the Jaeger were significantly lower than those of the Hammersmith plethysmograph (2.8 kPa/L/sec vs. 3.0 kPa/L/sec). The mean within patient coefficient of variability for inspiratory resistance of the Jaeger plethysmograph (16.7%) was significantly higher than that of the Hammersmith plethysmograph (11.6%) (P = 0.014). CONCLUSION: These results suggest plethysmographs which incorporate electronic compensation may be inappropriate for use in infants and very young children.     

慢性阻塞性肺疾病患者心率变异性与气道阻力和肺功能的关系分析

目的探讨慢性阻塞性肺疾病(简称慢阻肺)患者心率变异性(HRV)与其气道阻力(R)和肺功能(LF)的关系。方法将140例慢阻肺患者根据慢阻肺分级分为轻度组(n=41)、中度组(n=58)和重度组(n=41),另选取30例同期健康查体者作为对照组。比较四组HRV、R和LF并分析慢阻肺患者HRV与其R和LF的关系。结果轻度组、中度组的和重度组HRV和LF均低于对照组,R则高于对照组,慢阻肺患者HRV和LF亦随着慢阻肺分级的增大而降低,R则随着慢阻肺分级的增大而升高(P0.05)。Pearson相关性分析结果显示,慢阻肺患者HRV与R和LF均相关(P0.05)。结论慢阻肺患者存在HRV和LF的降低及R的增加,其HRV与R和LF均相关,可用于其病情的预测。     

Laboratory reference values for healthy adults from southern Tanzania

Objectives To define and discuss reference ranges for commonly determined laboratory parameters in healthy adults from southern Tanzania. Methods A population‐based sample of adult volunteers from Mbeya, Tanzania, who were not HIV positive or showing signs and symptoms of other diseases, participated in this study. We enrolled 145 women and 156 men between 19 and 48 years of age to determine clinical chemistry (CC), haematology and lymphocyte immunophenotyping (LIP) parameters using standard laboratory methods. Medians and nonparametric 95% reference ranges for each parameter were determined and compared with reference ranges from the USA, Europe and from other African countries. Results Agreement with ranges from developed countries was poor: for CC values the average concordance was 80.9% and 86.7% with values from two developed countries. Haematology ranges from the USA classified 86.3% of values correctly, whereas ranges from three different sub‐Saharan Africa (SSA) sites classified between 82.5% and 94.5% of values correctly. The agreement of LIP reference ranges was 87.5% with values determined in Germany but between 91.7% and 95.8% compared with values determined at other sites in SSA. Conclusion Clinical reference ranges determined in developed countries are inadequate for use in SSA. Laboratories in this region should either define their own or use values determined under similar conditions. The ranges reported here are more appropriate for use in SSA than ranges determined in developed countries.     

The Global Lung Initiative 2012 reference values reflect contemporary Australasian spirometry

We aimed to ascertain the fit of the European Respiratory Society Global Lung Initiative 2012 reference ranges to contemporary Australasian spirometric data. Z‐scores for spirometry from Caucasian subjects aged 4–80 years were calculated. The mean (SD) Z‐scores were 0.23 (1.00) for forced expirtory volume in 1 s (FEV₁), 0.23 (1.00) for forced vital capacity (FVC), ?0.03 (0.87) for FEV₁/FVC and 0.07 (0.95) for forced expiratory flows between 25% and 75% of FVC. These results support the use of the Global Lung Initiative 2012 reference ranges to interpret spirometry in Caucasian Australasians.     

支气管镜肺减容术之旁路通气法治疗肺气肿的研究进展

本文对支气管镜肺减容术尤其是旁路通气法治疗肺气肿研究成果和最新进展等进行综述.     

Limitations of electronic compensation for measuring plethysmographic airway resistance in infants

Electronic compensation to overcome thermal artifacts during plethysmographic estimations of airway resistance is now used routinely in adults and school-age children, and was shown to be a valuable means of discriminating airway function between preschool children with and without lung disease. A similar system is now commercially available for infants, which could increase the applicability of this technique. However, we noted marked discrepancies in electronically calculated values of airway resistance in this age group, both with respect to absolute values displayed and marked within-subject variability on a single test occasion. The aim of this technical report is to summarize our recent findings in order to alert other users to potential problems. Airway resistance (R(aw)) was measured in 62 infants (28 with cystic fibrosis (CF); 34 healthy). Three to five epochs of quiet regular tidal breathing were collected in each infant. Marked within-subject, within-test variability was observed, with the median coefficient of variation (CV) being 9.1% (range, 1.2-52.6%) within and 8.5% (0.1-112%) between epochs. Among healthy infants, R(aw) varied from 0.1-6.4 (kPa x liter(-1) x sec), with no relationship to either body or lung size and complete overlap of results with those from infants with CF, despite abnormal lung function in the latter when assessed by other means. The marked within- and between-subject variability in healthy infants, and lack of discriminative power of R(aw) when derived from electronically compensated values, currently preclude application in either clinical or research studies.     

A scoring system for lung function tests in infants.

Measurements of thoracic gas volume (TGV), airway resistance (Raw), and airway conductance (Gaw) were calculated in a group of 42 normal infants using a whole-body plethysmograph. Maximum expiratory flow at functional residual capacity was measured in a separate group of 108 normal infants. Using data obtained from these infants the following regression equations were calculated: Gaw (L.s-1.cmH2O) = -0.0475 + 0.00164 x length (cm) square root of TGV (mL1/2) = -3.22 + 0.263 x length (cm) VmaxFRC (mL.s-1) = -173 + 5.2 x length (cm). The standard errors of prediction are a measure of the scatter of individual results from the normal population about the true regression line. They were used to define limits of the normal ranges for these tests of lung function, and to develop a scoring system. This approach is preferable to expressing results as percent predicted, which gives no indication of how likely a measurement is to be within normal limits.     

总气道阻力与FEV_1在检测哮喘气道可逆性中的比较

目的目前国内常用的诊断哮喘的方法为呼吸量检查法,但是其存在一定缺点,比如哮喘或阻塞性肺疾病患者急性加重期时无法配合。而脉冲振荡肺功能测量法的优点就是不需要用力呼吸,平静呼吸下就可以测量。本研究通过对呼吸总阻抗等指标与FEV1相比较,对脉冲振荡肺功能进行了更详细的应用研究。方法入选2015年2月到12月我院呼吸内科急性哮喘发作成年患者120名,在用药前后同时进行呼吸量肺功能法和脉冲振荡肺功能法的测量,对两种不同方法测量结果的相关性进行比较,比较两种肺功能在检测哮喘患者用药前后改善率的敏感性。结果用药后FEV1有较大的幅度的升高,而脉冲振荡技术所得的R5敏感度明显优于FEV1(P0.05)。结论在检测哮喘患者用药前后的改善率方面,R5能够更为准确的反应哮喘患者的气道可逆性的改善率,且脉冲振荡肺功能操作简单,更适合支气管哮喘急性发作期的患者。     

Specific airway resistance,interrupter resistance,and respiratory impedance in healthy children aged 2–7 years

We report data on respiratory function in healthy children aged 2–7 years in whom we measured respiratory resistance by the interrupter technique (Rint); total respiratory impedance (Zrs), respiratory resistance (Rrs), and reactance (Xrs) by the impulse oscillation technique; and specific airway resistance (sRaw) by a modified procedure method in the whole body plethysmograph. Measurements were attempted in 151 children and were successfully obtained in 121 children with a mean (SD) age of 5.3 (1.5) years; no measurements were possible in 30 children (mean age 3 (0.9) years). The repeatability of measurements was independent of the age of the subjects, and the within-subject coefficient of variation was 11.1%, 8.1%, 10.8%, and 10.2% for sRaw, Rint, Zrs, and Rrs at 5 Hz (Rrs5), respectively. All lung function indices were linearly related to age, height, and weight. A significant negative correlation with age, height, and weight was found for Rint, Zrs, and Rrs5. Xrs5 was positively correlated to age and body size. The mean values of Rint, Rrs5, Xrs5, and Zrs in children younger and older than 5 years were 1.04, 1.38, −0.5, and 1.48 kPa · L⁻¹ · s and 0.9, 1.18, −0.37, and 1.23 kPa · L⁻¹ · s, respectively. sRaw showed no significant correlation with body size or age and the mean sRaw in children younger and older than 5 years was 1.09 and 1.13 kPa · s, respectively. None of the indices of respiratory function differed between boys and girls. Xrs and Rrs exhibited a significant frequency dependence in the range of 5–35 Hz. The techniques applied in this study require minimal cooperation and allow measurement of lung function in 80% of our population of awake young children. Further studies are needed to evaluate the potentials of the presently established reference values for clinical and epidemiological purposes. Pediatr Pulmonol. 1998; 25:322–331. © 1998 Wiley-Liss, Inc.     

Nasal airway dimensions and lung function in awake,healthy neonates

Possible relations between nasal airway dimensions and measures of lung function are not well established. It has been suggested that a major part of airway resistance is found in the nose. However, little is known about the shape of tidal flow volume (TFV) loops in relation to nasal caliber. We therefore investigated whether lung function assessed by tidal breathing in healthy newborn infants was affected by nasal airway dimensions. Nasal airway dimensions were measured in 17 healthy newborn babies (mean age, 2.7 days) by acoustic rhinometry before and immediately after lung function measurements. Lung function was evaluated by TFV loops and passive respiratory mechanics (single-breath occlusion technique), first with both nostrils open, and subsequently immediately after occlusion of the larger of the two nostrils, causing at least a 50% reduction in nasal minimum cross-sectional area (MCA). Neither the TFV expiratory ratios (time and volume to reach peak flow to total time and volume, respectively [t_PTEF/t_E and V_PTEF/V_E, respectively]), nor resistance or compliance of the total respiratory system differed significantly regardless of whether one or both nostrils were open. With one nostril closed there were no significant effects on any of the measured lung function parameters. We conclude that in healthy awake neonates reducing the cross-sectional area of nasal dimensions by 50% does not affect TFV loops or passive respiratory mechanics. Pediatr. Pulmonol. 1998; 25:99–106. © 1998 Wiley-Liss, Inc.     

Exhaled nitric oxide in healthy nonatopic school-age children: determinants and height-adjusted reference values

Exhaled nitric oxide (FENO) was proposed as a marker of airway inflammation, but data about FENO in healthy children measured with standardized methods are so far limited. In order to assess the determinants of FENO in healthy children, we investigated a population-based sample of school-age children (n = 276) with a questionnaire, skin-prick tests, spirometry, and the measurement of FENO. The FENO of 114 nonatopic and nonsmoking children considered healthy were analyzed with stepwise multiple regression analysis, which showed significant associations with age, standing height, weight, and body surface area, but not with gender. Height was found to be the best independent variable for the regression equation for FENO, which on average showed an increase in the height range of 120-180 cm from 7 to 14 ppb. In the random sample of children, increased FENO was associated with atopy (odds ratio, 9.0; 95% confidence interval, 3.9-21.1; P < 0.0001), and significantly with allergic rhinitis and atopic dermatitis, but not with asthma. Respiratory symptom-free children with skin-prick test positivity had significantly higher FENO than healthy nonatopic subjects. We conclude that height is the best determinant of FENO in healthy children. Due to the strong effect of atopy, FENO data should not be interpreted without knowing the atopic status of the child. The present reference values of FENO may serve in clinical assessments for measuring airway inflammation in children.     

双相气道正压通气治疗急性肺损伤的临床观察

目的探讨双相气道正压（BIPAP）通气模式对急性肺损伤（acute lung injury,ALI）患者的治疗作用。方法将20例接受机械通气治疗的Au患者随机分为容量控制通气组（VCV组）和双相气道正压通气组（BIPAP组）,每组各10例。观察两组血气分析、呼吸力学指标。结果通气后BIPAP组的氧分压（PaO2）、动脉血氧饱和度（SaO2）、氧合指数（OI）均显著高于VCV组（P〈0.05）;通气结束时,VCV组镇静剂用量和气管插管通气时间均显著高于BIPAP组（P〈0．05）。结论BIPAP通气模式人机协调性好,缩短了治疗时间。     

内科肺减容术在慢性阻塞性肺疾病最新研究进展

阻塞性呼吸道疾病是多种疾病组成的,但它们都可因炎症导致气道狭窄,从而导致呼吸做功增加.由于其患病人数多,病死率高,严重影响患者的劳动能力和生活质量.不同群体的哮喘、慢性支气管炎和肺气肿最佳治疗策略应该是多方面的,如高危肺气肿患者应包括药物学和非药物方法以及手术治疗.回顾当前支气管镜介入水平,近十年其发展目标是更好地控制哮喘症状和缓解由于不适合肺减容手术的肺气肿患者症状,由此可见,新型支气管镜技术针对气道阻塞性疾病治疗有很大帮助.