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.

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.

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.

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.

Actualización en espirometría y curva flujo / volumen en escolares y adolescentes / School and adolescent spirometry and flow / volume curve update

Spirometry is the most commonly used test to evaluate lung function in children and adults. To obtain good quality results, several requirements must be fulfilled: professional capacity of the technician, the quality of the equipment, the patient's collaboration, the use of appropriate reference standards. The purpose of spirometry is to define types of ventilatory alterations of the central and peripheral airways, to evaluate the response to bronchodilators and to guide the presence of restrictive diseases. The new consensus of national and international experts are described, which have been perfecting several aspects of this test.

La espirometría es el examen más comúnmente utilizado para evaluar la función pulmonar en niños y adultos. Para obtener resultados de buena calidad deben cumplirse varios requisitos, desde la capacidad profesional del técnico, calidad de los equipos, colaboración del paciente y utilización de patrones de referencia adecuados. La espirometría tiene como utilidad definir alteraciones ventilatorias obstructivas de vía aérea central y periférica, evaluar respuesta a broncodilatador y orientar al diagnóstico de enfermedades restrictivas. Se describen los nuevos consensos de expertos nacionales e internacionales, los cuales han ido perfeccionando varios aspectos de este examen.

Bronquiolitis obliterante secundaria a sindrome de stevens-johnson. Presentacion de 2 casos y revision de la literatura / Obliterans bronchiolitis secondary to stevens-johnson syndrome: case reports

Stevens-Johnson syndrome corresponds to a hypersensitivity reaction produced by various etiologies, for example exposure to drugs, microbial agents, or by an idiopathic cause. It is marked by an acute vesicular-bullous eruption, which affects the skin and mucous membranes, with systemic manifestations of variable severity, and it may present a fatal evolution. Stevens-Johnson syndrome can occasionally present chronic pulmonary complications, such as bronchiolitis obliterans; however, other etiologies are more frequent in our environment, for example severe pneumonia due to adenovirus. Our objective is to present two cases of bronchiolitis obliterans post Stevens-Johnson syndrome and to make a literature review.

El síndrome de Stevens-Johnson corresponde a una respuesta de hipersensibilidad producida por diversas etiologías, que incluyen exposición a drogas, agentes microbianos o idiopática. Se manifiesta por una erupción vesículo-bulosa aguda, que afecta la piel y las mucosas, con manifestaciones sistémicas de severidad variable, pudiendo presentar una evolución fatal. El síndrome de Stevens-Johnson puede presentar ocasionalmente complicaciones pulmonares crónicas, como bronquiolitis obliterante, siendo en nuestro medio más frecuente otras etiologías, como la observada luego de una neumonía grave por adenovirus. El objetivo es presentar dos casos de bronquiolitis obliterante post síndrome de Stevens-Johnson y hacer una revisión de la literatura.

Biphasic flow-volume loop in granulomatosis with polyangiitis related unilateral bronchus obstruction.

Spirometry flow-volume measurement is used routinely in the outpatient setting to rule out obstructive lung diseases. Biphasic flow-volume loop is a classic presentation of unilateral bronchial stenosis due to multiple etiologies and it should raise clinical suspicion. Granulomatosis with polyangiitis (GPA) is a systemic inflammatory condition with pulmonary manifestations that may be infiltrative (e.g., pneumonia), hemorrhagic, and may rarely cause bronchial stenosis. Herein, we present a case of GPA-related, bronchial obstruction that caused biphasic flow-volume loop along with a literature review.

Subjective and Objective Assessments of Flow-Volume Curve Configuration in Children and Young Adults.

RATIONALE: Analysis of maximal expiratory flow-volume curves (MEFVCs) allows for determination of airway obstruction, but quantitative methods to describe these curves are not commonly used. OBJECTIVES: We sought to determine the variability in MEFVC concavity assessment by pulmonary physicians, whether objective indices of concavity can be substituted for subjective expert impression, and whether MEFVC concavity correlates with clinical outcomes. METHODS: A survey of 37 MEFVCs (plus 3 duplicates) was sent to pulmonologists for quantitative assessment of MEFVC concavity. Objective indices (ß-angle, ratio forced expiratory flow at 50% of total lung volume to peak expiratory flow rate [FEF50/PEFR], ratio of maximum mid-expiratory flow to FVC [MMEF/FVC], kmax, and averaged flow-volume second derivatives) were calculated for each MEFVC and were correlated with the mean expert score. Both the mean expert scores and the best-performing index were then correlated with hospitalizations. MEASUREMENTS AND MAIN RESULTS: Ninety-two respondents provided usable data. There was substantial variability in concavity scores between subjects, but strong intrasubject reliability. Mean expert score did not differ by physician years of experience. Several indices (ß-angle, FEF50/PEFR, FEV1/FVC, MMEF/FVC, FEF50, and forced expiratory flow between 25 and 75% of total lung volume) correlated strongly with mean expert scores. A new variable (ß-MMEF) was constructed using coefficients from stepwise linear regression and accurately predicted the mean expert score (R(2) = 0.96). Mean expert score and ß-MMEF showed similar odds ratios for hospitalization (2.13 and 2.32, respectively) with identical positive (∼71%) and negative (87%) predictive values. The ß-MMEF was also associated with hospitalizations in two independent cohorts of children with asthma and cystic fibrosis. CONCLUSIONS: The ß-MMEF is an objective measure of maximal expiratory flow-volume curve concavity and highly correlates with expert impression. Both the mean expert score for expiratory curve concavity and the ß-MMEF were associated with increased risk of subsequent hospitalization. The ß-MMEF may be a useful biomarker for disease severity in asthma and cystic fibrosis.

Evaluación de flujos y volúmenes dinámicos en pacientes con compromiso muscular respiratorio / Dynamic flows and volumes evaluation in patients with respiratory muscle impairment

Spirometry measures the forced expiratory volumes and flows. In patients with neuromuscular disease, these are altered since there is some respiratory muscle involvement. The usefulness of this test is based on the interpretation of the shape of the flow / volume loop and values of spirometric variables. In patients with neuromuscular disease, Forced Vital Capacity is the most used especially for its prognosis value.

La espirometría mide volúmenes y flujos espiratorios forzados. En los pacientes con enfermedad neuromuscular (ENM) estos se ven alterados debido al compromiso muscular respiratorio. La utilidad de este examen se basa en la interpretación de la forma de la curva flujo/volumen y los valores de las variables espirométricas. En los pacientes con ENM la Capacidad Vital Forzada es la más utilizada ya que otorga valor pronóstico.

Oxygen desaturation during the six-minute walk test in COPD patients / Análise da dessaturação de oxigênio durante o teste de caminhada de seis minutos em pacientes com DPOC

Objective: To evaluate the behavior of oxygen saturation curves throughout the six-minute walk test (6MWT) in patients with COPD. Methods: We included 85 patients, all of whom underwent spirometry and were classified as having moderate COPD (modCOPD, n = 30) or severe COPD (sevCOPD, n = 55). All of the patients performed a 6MWT, in a 27-m corridor with continuous SpO2 and HR monitoring by telemetry. We studied the SpO2 curves in order to determine the time to a 4% decrease in SpO2, the time to the minimum SpO2 (Tmin), and the post-6MWT time to return to the initial SpO2, the last designated recovery time (RT). For each of those curves, we calculated the slope. Results: The mean age in the modCOPD and sevCOPD groups was 66 ± 10 years and 62 ± 11 years, respectively. At baseline, SpO2 was > 94% in all of the patients; none received supplemental oxygen during the 6MWT; and none of the tests were interrupted. The six-minute walk distance did not differ significantly between the groups. The SpO2 values were lowest in the sevCOPD group. There was no difference between the groups regarding RT. In 71% and 63% of the sevCOPD and modCOPD group patients, respectively, a ≥ 4% decrease in SpO2 occurred within the first minute. We found that FEV1% correlated significantly with the ΔSpO2 (r = −0.398; p < 0.001), Tmin (r = −0.449; p < 0.001), and minimum SpO2 (r = 0.356; p < 0.005). Conclusions: In the sevCOPD group, in comparison with the modCOPD group, SpO2 was lower and the Tmin was greater, suggesting a worse prognosis in the former. .

Objetivo: Avaliar o comportamento da curva de saturação de oxigênio durante o teste de caminhada de seis minutos (TC6) em pacientes com DPOC. Métodos: Incluímos 85 pacientes e todos realizaram espirometria, sendo classificados como portadores de DPOC moderada (DPOCm, n = 30) ou grave (DPOCg, n = 55). Todos os pacientes realizaram TC6 em um corredor de 27 m com monitoramento contínuo da SpO2 e FC por telemetria. A partir das curvas de SpO2, foram analisados os tempos para atingir a queda de 4% da SpO2, para atingir a SpO2 mínima (Tmin) e para a recuperação da SpO2 após o TC6 (TR). Foram calculadas as inclinações dessas curvas. Resultados: A média de idade nos grupos DPOCm e DPOCg foi de 62 ± 11 anos e 66 ± 10 anos, respectivamente. Todos os pacientes iniciaram o teste com SpO2 > 94%, nenhum recebeu suplementação de oxigênio durante o TC6, e não houve interrupções. A distância percorrida no TC6 não apresentou diferença significativa entre os grupos. Os menores valores da SpO2 ocorreram no grupo DPOCg. Não houve diferença no TR entre os grupos, e 71% e 63% dos pacientes nos grupos DPOCg e DPOCm, respectivamente, apresentaram queda de SpO2 ≥ 4% até o primeiro minuto. O VEF1% apresentou correlações significativas com ΔSpO2 (r = −0,398; p < 0,001), Tmin (r = −0,449; p < 0,001) e SpO2 mínima (r = 0,356; p < 0,005). Conclusões: As curvas dos pacientes do grupo DPOCg em relação às do grupo DPOCm apresentaram valores menores de SpO2 e maior Tmin, sugerindo um pior prognóstico nos primeiros. .

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.

Fisiología de la curva flujo/volumen espirométrica / Flow-volume curve: its physiological basis

We describe physiological basis to explain flow/volume curve obtained by forced spirometry. The main factors involved are alveolar and intraluminal airway pressure and transthoracic pressure, whose interrelationship determines dynamic airway compression. Lung and thoracic elastic recoil pressure and lung volumes also participate.

Se describen las bases fisiológicas de la curva flujo/volumen obtenida mediante espirometría forzada. Los principales factores involucrados son la presión alveolar y de la vía aérea y la presión transtorácica, cuyo balance determina la compresión dinámica de la vía aérea. Además intervienen la presión de retracción elástica pulmonar y de la caja torácica y los volúmenes pulmonares.

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.

Spectral analysis of respiratory flow and gas concentrations / Análise espectral de fluxo e concentrações de gases respiratórios

In this research we obtained samples of human respiratory flow, oxygen concentration and carbon dioxide concentration signals from 20 healthy subjects and evaluated the average power spectral density (PSD) of these signals. For each subject,the respiratory samples were acquired in four progressive levels of exercise in a cycle ergometer. Auto regressive moving average models were designed to represent the PSD found in each phase. An average PSD of the four levels was also calculated. Results have shown that the bandwidth of O2 concentration, CO2 concentration and flow signals was 8  Hz, 7 Hz, and 15  Hz, respectively, within the dynamic range of 50  dB. The PSD curves found can be used for optimal filter design for signal enhancing in fast on-line measurement of these signals.

Nesta pesquisa foram registradas amostras dos sinais respiratórios de fluxo, concentração de oxigênio e concentração de gás carbônico em 20 voluntários saudáveis. A densidade espectral de potência (DEP) média foi então calculada. Para cada voluntário, as amostras dos sinais foram registradas em quatro intensidades progressivas de esforço físico em uma bicicleta ergométrica. Para representar a DEP encontrada em cada fase foram ajustados modelos auto-regressivos de média móvel. Uma DEP média entre as quatro intensidades também é fornecida. Os resultados mostraram que as larguras de banda dos sinais de concentração de O2, concentração de CO2 e fluxo foram 8  Hz, 7  Hz e 15  Hz, respectivamente, dentro de uma faixa dinâmica de 50  dB. As curvas de DEP encontradas podem ser usadas em projetos de filtros ótimos para equalização destes sinais em medições em tempo real.

[A case of relapsing polychondritis monitored by repeated measurements of flow-volume curve].

A 57-year-old man was admitted to our hospital with hoarseness, productive cough, and dyspnea. Chest CT revealed a thickening of the tracheal wall, and the flow-volume curve showed a constrictive upper airway flow pattern. Bronchoscopy revealed disappearance of cartilaginous rings and tracheal stenosis. Biopsy of the cricoid cartilage showed findings compatible with relapsing polychondritis and a diagnosis of relapsing polychondritis was made in accordance with Damiani's criteria. The flow-volume curve and symptoms were immediately improved by methylprednisolone pulse therapy, but on reduction of oral prednisorone, recurrence was identified by flow-volume curve and bronchoscopy. Administration of dapson and cyclophosphamide in addition to oral prednisolone after intravenous methylprednisolone and flow-volume curve resulted in improvement. In this case, monitoring of flow-volume curve was useful for the evaluation of airway complication in relapsing polychondritis.

Area under the maximum expiratory flow-volume curve--a sensitive parameter in the evaluation of airway patency.

BACKGROUND: The most frequently used parameters for assessing bronchoconstriction and bronchodilation are forced expiratory volume in 1 s (FEV(1)) and peak expiratory flow (PEF). OBJECTIVES: To assess the sensitivity of other parameters after induced bronchoconstriction and bronchodilation. METHODS: From maximum expiratory flow-volume (MEFV) curves, forced vital capacity, FEV(1), PEF, maximum expiratory flows (MEF) at 25, 50 and 75% of vital capacity and the area under the MEFV curve (A(ex)) were measured in two groups of asthmatic children after induced bronchoconstriction and bronchodilation, and in children with cystic fibrosis (CF) after bronchodilation. RESULTS: In 142 asthmatics without airway obstruction, bronchoconstriction was induced by inhalation of 1% histamine aerosol. The 20% fall in A(ex) compared to baseline was found in all asthmatics, while the 20 and 15% falls in FEV(1) were noted in 36 and 65% of the patients, respectively. Other parameters were less sensitive or interpretation was problematic. Another 110 asthmatics with mild-moderate airway obstruction were treated with various bronchodilators. The 20% increase in A(ex) was observed in all asthmatics, while the 20% increase in FEV(1) was found in only 33% of the patients and the 15% increase in FEV(1) in 51%. In 9 CF children, the pattern of changes in A(ex) and FEV(1) after bronchodilation was similar to that in asthmatics. CONCLUSIONS: A(ex) was a sensitive and less problematic parameter in the evaluation of airway patency in comparison with FEV(1) and other parameters measured from the MEFV curve in our study patients.

Mid-term survival after abdominal aortic aneurysm surgery predicted by cardiopulmonary exercise testing.

BACKGROUND: Cardiopulmonary exercise (CPX) testing measures how efficiently subjects meet increased metabolic demand. This study aimed to determine whether preoperative CPX testing predicted postoperative survival following elective abdominal aortic aneurysm (AAA) repair. METHODS: Some 130 patients had CPX testing before elective open AAA repair. Additional preoperative, operative and postoperative variables were recorded prospectively. Median follow-up was 35 months. The correlation of variables with survival was assessed by single and multiple regression analyses. RESULTS: CPX testing identified 30 of 130 patients who had been unfit before surgery. Two years after surgery the Kaplan-Meier survival estimate was 55 per cent for the 30 unfit patients, compared with 97 per cent for the 100 fit patients. The absolute difference in survival between these two groups at 2 years was 42 (95 per cent confidence interval 18 to 65) per cent (P < 0.001). CONCLUSION: Preoperative CPX testing, combined with simple co-morbidity scoring, identified patients unlikely to survive in the mid-term, even after successful AAA repair.

Pruebas de función pulmonar en el niño / Pulmonary function test in children

Contar con pruebas de función pulmonar permite realizar un diagnóstico y seguimiento más adecuado en los pacientes que presentan patología respiratoria crónica o recurrente, o en aquellos que padezcan una enfermedad que de forma directa o indirecta afecte al aparato respiratorio. Estos exámenes se pueden hacer en forma aceptable y reproducible en niños desde los tres a seis años de vida. En este artículo se detallan las características más importantes de las pruebas de función pulmonar que frecuentemente se utilizan en el niño, como son la espirometría, curva flujo-volumen, prueba de provocación bronquial con ejercicio y con metacolina y la flujometría. También se detalla una técnica novedosa que permite medir la resistencia de la vía aérea, denominada oscilometría de impulso, de la cual se dispone en Clínica Las Condes y tiene la particularidad de requerir mínima cooperación por parte del paciente. Para el médico que solicita un examen de función pulmonar, es relevante conocer las condiciones de aceptabilidad, reproducibilidad e interpretación básicas, para que tenga un verdadero rol en el manejo de la patología respiratoria del niño.