Inspiratory Flow-volume Curves Research Articles

Area under the inspiratory flow-volume curve (AIN): Proposed normative values.

Area under expiratory flow-volume curve (AEX) has been shown to be a valuable functional measurement in respiratory physiology. Area under inspiratory flow-volume loop (AIN) also shows promise in characterizing upper and/or lower airflow obstruction. we aimed here to develop normative reference values for AIN, able to ascertain deviations from normal. We analyzed AIN in 4,980 spirometry tests recorded in non-smoking, healthy individuals in the Pulmonary Function Testing Laboratory. The mean (95% confidence interval, CI), standard deviation and median (25th-75th interquartile range) AIN were 16.05 (15.79-16.31), 9.08 and 14.72 (9.12-21.42) L2·sec-1, respectively. The mean (95% CI) and standard deviation of the best-trial measurements for square root of AIN (Sqrt AIN) were 3.84 (3.81-3.87) and 1.14; 4.15 (4.12-4.18) and 1.03 in men, and 2.68 (2.63-2.72) and 0.72 L·sec-1/2 in women. The mean (standard deviation) of pre- and post-bronchodilator Sqrt AIN were 3.71 (1.17) and 3.81 (1.19) L·sec-1/2, respectively. The mean (95% CI), standard deviation and lowest 5th percentile (lower limit of normal, LLN) of Sqrt AIN/Sqrt AEX (%) were 101.3 (100.82-101.88), 18.7, and 71.8%; stratified by gender, it was 102.2 (101.6-102.8), 18.6, and 72.8% in men, and 98 (96.9-99.2), 18.8, and 68.6% in women, respectively. The availability of area under the inspiratory flow-volume curve (AIN) and the derived indices offers a promising opportunity to assess upper airway disease (e.g., involvement of larynx, trachea or major bronchi), especially because some of these measurements appear to be independent of age, race, height, and weight.

Forced inspiratory flow volume curve in healthy young children

Spirometry testing should include both expiratory and inspiratory measurements. Inspiratory forced maneuvers can demonstrate extrathoracic airway abnormalities, of which various symptoms may suggest asthma. However, the inspiratory portion of the forced flow/volume maneuver in young healthy children has not yet been described. To document and analyze the forced inspiratory flow volume curve indices in healthy young children. Healthy preschool children (age 2.5-6.5 years) from community kindergartens around Israel. The teaching method included multi-target, interactive spirometry games and accessory games for inspiration (e.g., inspiratory whistle). One hundred and fourteen out of a total of 157 children performed duplicate full adequate inspiratory maneuvers. Repeatability between two maneuvers was 5.6%, 4.0%, 5.1%, 7.3% for inspiratory capacity (IC), forced inspiratory vital capacity (FIVC), peak inspiratory flow (PIF), and mid inspiratory flow (FIF50). Inspiratory flow indices were significantly lower than the expiratory flow indices. The time to reach PIF was significantly longer (mean +/- SD; 229 +/- 21 msec) than the time to reach peak expiratory flow (92 +/- 8 msec; P < 0.0001). The shape of the inspiratory curve was parabolic and did not vary with age. The formed predicted equations were in agreement with the extrapolated values for older healthy children. The majority of healthy young children can perform reliable maximum inspiratory flow volume curves. Our results provide a framework of reference equations for maximum inspiratory flow volume curve in the young children. The clinical applications of these equations have to be explored.

Pulse Oximetry Coupled With Spirometry in the Emergency Department Helps Differentiate an Asthma Exacerbation From Possible Vocal Cord Dysfunction

Nolan PK, Chrysler M, Phillips G, Goodman D, Rusakow LS. Pediatr Pulmonol. 2007;42(7):605–609 PURPOSE OF THE STUDY. These investigators sought to determine if they could find evidence for vocal cord dysfunction (VCD) in asthmatic adolescents whose condition failed to respond adequately to treatment in the emergency department (ED) for a presumptive asthma exacerbation. STUDY POPULATION. Subjects with wheezing presenting to the ED of an urban children's hospital were recruited. Inclusion criteria were age 12 to 21 years, failure to respond to treatment for wheeze sufficiently to allow discharge, and pulse oximetry reading of ≥97%. Exclusion criteria were having other cardiac or pulmonary disease, inability to perform spirometry, or need for endotracheal intubation. METHODS. Spirometry with standard techniques was performed by using a computer-linked pneumotachygraph and appropriate software to capture both expiratory and inspiratory flow volume curves. Spirometric results were classified as small airway obstruction, variable extrathoracic airway obstruction (consistent with VCD), a combination of the 2 previous findings, or normal airflow. RESULTS. Twenty ED encounters with 17 subjects were studied. Only 5 (25%) of the encounters included spirometric evidence of small airway obstruction, but 12 of 20 had evidence for VCD (ie, variable extrathoracic airway obstruction on the inspiratory loop). These 12 included 3 that also had evidence for small airway obstruction. There were 6 encounters with no abnormality on spirometry. CONCLUSIONS. Spirometry may identify presumptive refractory asthma exacerbations that, instead, are episodes of VCD. REVIEWER COMMENTS. Several years ago we treated an 8-year-old boy who had been admitted to the hospital for status asthmaticus 4 times in 1 month but never had an oxygen requirement. A videotape of the boy when he was symptomatic (provided by the parents) showed obvious stridor, not wheezing. Similarly, in this study the cardinal observation was refractory “wheeze” without arterial desaturation. Computerized spirometry is not universally available in the ED, and in addition, not all such units have software capable of displaying the inspiratory limb of the flow-volume loop. However, in busy ED environments with large asthmatic populations, availability of this measurement should greatly aid the classification of wheezing events. Pediatricians need to be more aware that VCD may present symptoms that mimic asthma.

Use of Flow–Volume Curves to Predict Oral Appliance Treatment Outcome in Obstructive Sleep Apnea

It has been recognized that mandibular advancement splint (MAS) treatment is effective in some, but not all, patients with obstructive sleep apnea (OSA). Hence there is a need for a simple and reliable clinical tool to assist in the differentiation of treatment responses. We hypothesized that abnormalities of flow-volume curves, together with other clinical variables, may have clinical utility in the prediction of MAS treatment outcome. Fifty-four patients with known OSA underwent MAS treatment. Expiratory and inspiratory flow-volume curves were measured in the erect and supine positions to derive midinspiratory flow (MIF(50)) and the ratio of expiratory to inspiratory flow at 50% of vital capacity (MEF(50):MIF(50)). Multivariable logistic regression was performed to identify additional significant clinical variables in the prediction of treatment outcome. The mean (+/- SD) apnea-hypopnea index (AHI) in 35 responders was significantly reduced from 28.9 +/- 13.7 to 6.7 +/- 5.8/hour (p<0.001). In 19 nonresponders there was no significant change in AHI. MIF(50) was lower (6.04 +/- 1.80 vs. 6.88 +/- 1.08 L/second; p=0.035) and the MEF(50):MIF(50) ratio was higher (0.82 +/- 0.23 vs. 0.61 +/- 0.15; p=0.001) in responders than nonresponders. Logistic regression analysis revealed that the MEF(50):MIF(50) ratio was the most important predictive factor for MAS treatment outcome, but that body mass index, age, and baseline AHI were also contributory. These data suggest that flow-volume curves, in combination with other factors such as body mass index, age, and baseline AHI, may have a useful clinical role in the prediction of treatment outcome with MAS.

Lung volume reduction surgery (LVRS): criteria for selecting patient in Antonio Pedro Hospital, Federal Fluminense University, Niter i city, Rio de Janeiro, Brazil

Chronic Obstructive Pulmonary Disease (CPOD) is an important problem in Brazil and other countries. The clinical treatment of ambulatory patients is now reasonably standardized. Lung volume reduction surgery (LVRS) is an alternative of surgical treatment of emphysema (aside from lung transplantation). The aim of this study was to analyse patient selection criteria for LVRS. This study was carried out using a sample of 31 patients referred to and given assistance to at the Smoking and Chronic Obstructive Pulmonary Disease Outpatient Ward Antonio Pedro Hospital, who were evaluated to check whether or not they could be eligible for LVRS. Aiming at evaluating the major criteria for eligibility for LVRS, the patients underwent a protocol including standardized anamnesis and physical examination, spirometry with maximum inspiratory and expiratory flow volume curves associated with post-bronchodilatator test, room air arterial blood gases, a six-minute walking test, plain chest roentgenograms and left lateral chest roentgenograms, high-resolution chest computed tomographic scans and lung perfusion scans. Statistical analysis was conducted with description of data proportions. Contraindications to surgery included chronic bronchitis (29% or nine patients), forced expiratory volume in one second (FEV 1) more than 80 percent predicted (13% or four patients), negative consent for surgery (10% or three patients), fibrosis pattern, severe depression and bronchiectasis (two patients each one), solitary pulmonary nodule, severe obesity, severe bullous emphysema, pulmonary hipertension, pulmonary resection history, current cigarette smoking, diffuse emphysema with alpha-1-antitrypsin deficiency and severe cardiac disease (one patient each). Indication. One selected patient with severe symptoms of emphysema met criteria for LVRS (bilateral superior lobe heterogeneous pattern of emphysema on chest computed tomography and lung perfusion scan). Chronic bronchitis was the major isolated factor to contraindicate LVRS. Most patients who fit the criteria for the surgery performance refused to undergo the LVRS for fear of the surgery and after pulmonary rehabilitation. The most important criteria for LVRS is bilateral superior lobe heterogeneous pattern of emphysema.

Inspiratory flow-volume curve in snoring patients with and without obstructive sleep apnea.

We analyzed the flow-volume curves of 50 patients with complaints of snoring and daytime sleepiness in treatment at the Pneumology Unit of the University Hospital of Brasília. The total group was divided into snorers without obstructive sleep apnea (OSA) (N = 19) and snorers with OSA (N = 31); the patients with OSA were subdivided into two groups according to the apnea/hypopnea index (AHI): AHI < 20/h (N = 14) and AHI > 20/h (N = 17). The control group (N = 10) consisted of nonsmoking subjects without complaints of snoring, daytime sleepiness or pulmonary diseases. The population studied (control and patients) consisted of males of similar age, height and body mass index (BMI); spirometric data were also similar in the four groups. There was no significative difference in the ratio of forced expiratory and inspiratory flows (FEF50%/FIF50%) in any group: control. 0.89; snorers, 1.11; snorers with OSA (AHI < 20/h), 1.42, and snorers with OSA (AHI > 20/h), 1.64. The FIF at 50% of vital capacity (FIF50%) of snoring patients with or without OSA was lower than the FIF50% of the control group (P < 0.05): snorers 4.30 l/s; snorers with OSA (AHI < 20/h) 3.69 l/s; snorers with OSA (AHI > 20/h) 3.17 l/s and control group 5.48 l/s. The FIF50% of patients with severe OSA (AHI > 20/h) was lower than the FIF50% of snorers without OSA (P < 0.05): 3.17 l/s and 4.30 l/s, respectively. We conclude that 1) the FEF50%/FIF50% ratio is not useful for predicting OSA, and 2) FIF50% is decreased in snoring patients with and without OSA, suggesting that these patients have increased upper airway resistance (UAR).

Effect of a Nasal Dilatator on Nasal Patency During Normal and Forced Nasal Breathing

A nasal dilatator contains two elastic strips, which provide the dilatator with a spring action. The aimed function of the nasal dilatator is to slightly open the nares and hereby facilitate nasal breathing. The aim of this study was to evaluate the effect of a nasal dilatator by measuring nasal airway resistance during normal breathing and nasal forced expiratory and inspiratory flows and volumes with and without use of the nasal dilatator. Nasal resistance was measured with a whole body plethysmograph; maximal expiratory and inspiratory flow-volume curves were obtained with a pneumotachometer. These measurements were performed in ten healthy volunteers. No significant difference was found between nasal resistance with and without the nasal dilatator. However, values for forced inspiratory volume in 1 s (FIV 1) with the nasal dilatator, proved to be significantly higher (p=0.045,paired t-test) than values obtained without the nasal dilatator; mean improvement was 0.26 L (sd = 0.36). No significant improvement in peak inspiratory flow (PIF) was found, as was the case for the other flows and volumes. It is concluded that the nasal dilatator causes no appreciable improvement of nasal patency during normal breathing. In view of the fact that FIV 1 values increased significantly, we believe that the nasal dilatator prevents collapse of the external nares during forced inspiration. A beneficial effect during exercise when ventilation is increased is however doubtful because in that situation most volunteers switch to oronasal breathing already at submaximal exercise.

Airway function tests and vocal cord paralysis in lung transplant recipients

Maximum expiratory and inspiratory flow-volume (MEFV, MIFV) curves, specific airway conductance (sGaw), and flexible fiberoptic laryngoscopy were examined in 8 pediatric lung transplant recipients with vocal cord paralysis (VCP). Six were heart-lung (H-L) and 2 double-lung (D-L) recipients, 7 had left VCP, and 1 had right VCP. Based on the pulmonary function tests (PFT), 2 subgroups could be distinguished in the 8 recipients with VCP. Group A (5/8 recipients; mean age, 13 +/- 3.4 years; mean height, 144.3 +/- 12.3 cm) had significantly reduced specific airway conductance (sGaw; < 2 SD from predicted) and normal MEF25, MEF50, peak expiratory flow (PEF), forced expiratory volume in 1 second (FEV1), and %FEV1/forced vital capacity (FVC); this pattern suggested variable extrathoracic airway obstruction. PIF was normal in 4/5 and reduced in 1/5 of these recipients. Group B (3/8 recipients with VCP; mean age, 17 +/- 2.4 years; mean height, 156.3 +/- 12.0 cm) had significantly reduced sGaw, MEF25, MEF50, PEF, FEV1, and %FEV1/FVC, implying primarily small airway obstruction. These recipients had bronchiolitis obliterans. The results suggest that a pattern of reduced sGaw and normal MEFs, PEF, FEV1, and PIF should raise the possibility of VCP in patients after lung transplantation. sGaw is more sensitive than PIF and PEF in identifying airway obstruction due to VCP, and should be routinely included in the follow-up evaluation of lung transplant recipients.

Bronchodilatation and the Inspiratory Flow Volume Curve

The inspiratory flow volume curve is included in the spirometric tracing provided by most pulmonary function laboratories and is useful in assessing upper airway abnormalities. We analyzed the changes in peak inspiratory flow (PIF), forced inspiratory flow at 50% (FIF50), and forced inspiratory vital capacity (FIVC) that occur with bronchodilator challenge testing (3 puffs of a beta-agonist by metered-dose inhaler without a spacer device) in 145 consecutive patients. Fifty-five patients responded to bronchodilators with either a 12% or 200-mL change in FEV1 or FVC. All of these subjects produced forced expiratory maneuvers that fulfilled American Thoracic Society criteria or acceptability. The FIVC was the only inspiratory parameter that consistently showed a similar correlation to the bronchodilator responsiveness demonstrated by the FEV1 or FVC. With the reduction in air trapping, a 12% or 200-mL change in the FIVC is additional confirmatory evidence of bronchodilator responsiveness.

Differential effects of nasal continuous positive airway pressure on reversible or fixed upper and lower airway obstruction.

Our study was to assess whether there were differential effects of nasal continuous positive airway pressure (nCPAP) on different kinds of obstruction in either upper or lower airways in patients with chronic obstructive pulmonary disease (COPD). nCPAP (6 cmH2O for ten minutes) was applied to 7 patients with reversible extrathoracic upper airway obstruction (RUAO) and 3 patients with fixed extrathoracic upper airway obstruction (FUAO). Eighteen stable asthmatics, receiving methacholine challenge to induce a more than 20% reduction in FEV1, were randomly investigated for the effect of nCPAP or sham pressure on reversible lower airway obstruction. Nine stable COPD patients were enrolled to study the effect on irreversible lower airway obstruction. Maximal expiratory and inspiratory flow volume curves and dyspnoea scores were obtained before and after immediate withdrawal of nCPAP. In the RUAO group, nCPAP significantly improved stridor and dyspnoea scores, decreased the ratio of FEF50/FIF50 from 2.05 +/- 0.25 to 1.42 +/- 0.16, and increased peak inspiratory flow (PIF) as well as forced inspiratory vital capacity by 26 +/- 8% and 9 +/- 4%, respectively. In expiratory phase, there was no significant change in pulmonary functions. In asthmatics, nCPAP significantly reversed methacholine-induced bronchoconstriction increasing forced vital capacity by 10 +/- 3%, FEV1 by 15 +/- 4% and PIF by 32 +/- 11%. nCPAP significantly increased the response to bronchodilators. The improvement in airflow rate persisted for at least 5 min after nCPAP withdrawal and was highly correlated with the response to bronchodilators. There was no significant effect of nCPAP on airflow rate in COPD patients. Subjective dyspnoea score changes paralleled the pulmonary function improvement. We conclude that there are differential effects of nCPAP on airflow rates in patients with different nature of airway obstruction. Patients with airway obstruction caused by structural changes may not benefit from the use of nCPAP in improving airflow rates.

Indices from flow-volume curves in relation to cephalometric, ENT- and sleep-O2 saturation variables in snorers with and without obstructive sleep-apnoea

In a group of 37 heavy snorers with obstructive sleep apnoea (OSA, Group 1) and a group of 23 heavy snorers without OSA (Group 2) cephalometric indices, ENT indices related to upper airway collapsibility, and nocturnal O2 desaturation indices were related to variables from maximal expiratory and inspiratory flow-volume (MEFV and MIFV) curves. The cephalometric indices used were the length and diameter of the soft palate (spl and spd), the shortest distance between the mandibular plane and the hyoid bone (mph) and the posterior airway space (pas). Collapsibility of the upper airways was observed at the level of the tongue base and soft palate by fibroscopy during a Muller manoeuvre (mtb and msp) and ranked on a five point scale. Sleep indices measured were the mean number of oxygen desaturations of more than 3% per hour preceded by an apnoea or hypopnoea of more than 10 s (desaturation index), maximal sleep oxygen desaturation, baseline arterial oxygen saturation (Sa,O2) and, in the OSA group, percentage of sleep time with Sa,O2 &lt; 90%. The variables obtained from the flow-volume curves were the forced vital capacity (FVC), forced expiratory and inspiratory volume in 1 s (FEV1 and FIV1), peak expiratory and peak inspiratory flows (PEF and PIF), and maximal flow after expiring 50% of the FVC (MEF50). The mean of the flow-volume variables, influenced by upper airway aperture (PEF, FIV1) was significantly greater than predicted.(ABSTRACT TRUNCATED AT 250 WORDS)

Inspiratory Flow Rate for the Evaluation of Bronchodilator in Patients with COPD

Background: Although there are improvements of clinical symtoms after bronchodilator inhalation in COPD patients, it has been noted that there was no increase of in some cases. did not reflect precisely the improvement of ventilatory mechanics after bronchodilator inhalation in these COPD patients. The main pathophysiology of COPD is obstruction of airway in expiratory phase but in result, the load of respiratory system is increased in inspiratory phase. Therefore the improvement of clinical symptoms after bronchodilator inhalation may be due to the decrease of inspiratory load. So we performed the study which investigated the effect of bronchodilator on inspiratory response of vetilatory mechanics in COPD patients. Methods: In 17 stable COPD patients, inspiratory and expiratory forced flow-volume curves were measured respectively before bronchodilator inhalation. 10mg of salbutamol solution was inhaled via jet nebulizer for 4 minutes. Forced expiratory and inspiratory flow-volume curves were measured again 15 minutes after bronchodilator inhalation. Results: , FVC and /FVC% were ( predicted), ( predicted) and respectively before bronchodilator inhalation. The values of increase of , FVC and PIF(Peak Inspiratory Flow) were (relative increase: 17.0%), (29.0%) and /sec(37.5%) respectively after bronchodilator inhalation. The increase of PIF was twice more than in average(p was not increased after bronchodilator inhalation were 35.0%, 44.0% and 55.5% respectively. Conclusion: The inspiratory parameter reflected improvement of ventilatory mechanics by inhaled bronchodilater better than expiratory parameters in COPD patients.

Lung function, CT-scan and X-ray in upper airway obstruction due to thyroid goitre

The purpose of this study was to assess the clinical reliability and to compare routine lung function tests (maximal flows and resistance) and radiological images (computed tomography (CT)-scan and X-ray) in upper airway obstruction. We, therefore, performed these examinations prospectively in 28 female patients (aged 68 +/- 13 yrs) with a goitre and without pulmonary disorders. Lung function measurements consisted of maximum expiratory and inspiratory flow-volume curves and of airway resistance. CT-scans and X-rays were performed during apnoea at functional residual capacity (FRC). Peak expiratory flow was 3.6 +/- 1.3 l.s-1 (i.e. 62 +/- 21% predicted); airway resistance was 0.38 +/- 0.14 kPa (i.e. 149 +/- 58% pred); and specific conductance was 1.0 +/- 0.3 kPa (i.e. 70 +/- 24% pred). Almost all lung function tests were significantly correlated with each other. On CT-scan the tracheal cross-sectional area at the zone of tracheal narrowing could be evaluated in 26 patients and was 58 +/- 17% (CT1/2) of the control area 2 cm above the carina (CT2). On X-ray the sagittal and coronal tracheal diameters at the zone of narrowing could only be measured in 16 subjects and were 60 +/- 17% (X-dia1/2) of the diameter at the control level. CT1/2 and X-dia1/2 were significantly correlated to each other. No correlation was found between the lung function tests and the radiological indices except airway resistance and CT2. Routine lung function and CT-scan do not provide comparable information on the degree of airway obstruction due to a goitre.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of the Inspiratory Flow-Volume Curve: Should it Always Precede the Forced Expiratory Maneuver?

The inspiratory flow-volume (FV) curve can be used to identify patients with upper airway obstruction, air trapping, and restriction. Current computed pulmonary function testing equipment often mandates a forced expiratory maneuver (FEM) immediately prior to the forced inspiratory maneuver (standard method). We evaluated the inspiratory FV curve with and without an antecedent FEM in 119 subjects referred for pulmonary function testing. The subjects were divided into four groups by grading the degree of airway obstruction using confidence intervals of the FEV1/FVC percent predicted minus the actual FEV1/FVC percent measured from the best FEM according to Intermountain Thoracic Society recommendations. The forced inspiratory vital capacity (FIVC), forced inspiratory flow 50 (FIF50), and peak inspiratory flow (PIF) from the inspiratory FV curve with an antecedent FEM was compared with the FIVC, FIF50, and PIF without an antecedent FEM in each category of obstructive lung disease. The FIVC without the antecedent FEM was significantly larger than that with an antecedent FEM by 170 ml (p < 0.002) in subjects with severe airway obstruction, but was not significantly different in the other groups. The FIF50 was not significantly different in any group, but approached significance in both normal subjects and subjects with severe obstruction. The PIF was not significantly different in any group, but approached significance in the normal subjects, order for patients with severe obstructive airway disease to generate a valid forced inspiratory FV curve, it should be obtained without an antecedent FEM. When a plateau of the inspiratory FV curve is encountered, we suggest that is useful to generate the inspiratory FV curve prior to the FEM and to analyze its flow and volume characteristics independent of the FEM. The "best" inspiratory FV curve should then be displayed with the "best" FEM for proper evaluation of the FV loop.

Effects of treatment on airway dynamics and respiratory muscle strength in Parkinson's disease.

To investigate how treatment can affect airway dynamics and respiratory muscle strength in Parkinson's disease (PD), we assessed maximum effort inspiratory and expiratory mouth pressures (MIP and MEP), oscillatory impedance, and maximum expiratory and inspiratory flow-volume curves (MEFV and MIFV) in 10 patients (8 male and 2 female; mean age 51 +/- 5.3 yr, SD) after temporary interruption of antiparkinsonian therapy (off) and during continuous subcutaneous infusion of a direct stimulant of dopamine receptors, apomorphine (on). Treatment improved neurologic scores (off 25 +/- 5, on 9 +/- 5, modified Webster scale, p < 0.001), MEP (off 45 +/- 25, on 63 +/- 29 cm H2O, p = 0.003), and peak inspiratory flow (PIF; off 3.83 +/- 1.6, on 4.37 +/- 1.7 L/s, p = 0.028). Maximum inspiratory pressure was very low off treatment (-25 +/- 16 cm H2O) and improved moderately with apomorphine (-33 +/- 17 cm H2O) (p = 0.064). Total respiratory resistance during tidal breathing was normal in 9 patients both off and on treatment despite, in some cases, dramatic changes in MEFV and MIFV curves. These results suggest that abnormalities of the flow-volume curves may be due to problems in the rapid activation and coordination of contraction of upper airways and chest wall muscles during forced maneuvers, which is improved by apomorphine treatment.

Rare rheumatic disorders: b. Relapsing polychondritis

Relapsing polychondritis is a rare inflammatory disease of cartilagecontaining tissue. The respiratory manifestations comprise recurrent and usually progressive inflammation of the cartilage of the nose, larynx, airways and ribs. Involvement of the respiratory tract is of prognostic importance as it has been associated with the majority of deaths in this condition (McAdam et al, 1976). Pathologically, the affected cartilage shows loss of basophilic staining of the matrix, perichondrial inflammation and eventually destruction of cartilage with replacement by fibrous tissue. Narrowing of the airways results from inflammatory swelling during active stages of the disease and destruction of tracheal or bronchial cartilage with the formation of fibrous tissue and associated scarring. The functional abnormalities are due to varying combinations of structural narrowing of the airway lumen and loss of stability due to abnormally large dynamic changes in airway ~alibre during breathing. The airway narrowing may be localized to the larynx or to a narrow segment of trachea or can extend more distally along the cartilagecontaining airways. Narrowing of the airways may be complicated by secondary infection due to inadequate clearance of secretions which results from either impairment of mucociliary mechanisms or from diminished effectiveness of cough. Patients with respiratory tract involvement can present with hoarseness, dysphonia, cough, shortness of breath, a choking sensation or tenderness over the affected cartilages of the airway or ribs. Wheezing due to airway narrowing can lead to a mistaken diagnosis of asthma (Gibson and Davis, 1974). The important investigations to assess the severity and extent of airway involvement are functional and radiographic. In some patients bronchoscopy has been performed, allowing direct visualization of the extent of inflammation of the airway (Krell et al, 1986). Plain or computed tomography of the trachea and main bronchi helps determine the extent of the disease (Figure 1). The most useful functional information is obtained by examination of maximum expiratory and inspiratory flow-volume curves (Figure 2). Various combinations of limitation of maximal expiratory and inspiratory flow have been reported (Gibson and Davis, 1974; Mohsenifar et al, 1982; Krell et al, 1986), the exact pattern depending on the main site and

Effects of posture on flow-volume curves during normocapnia and hypercapnia in patients with obstructive sleep apnoea.

A high ratio of forced expiratory to forced inspiratory maximal flow at 50% of vital capacity (FEF50/FIF50) may identify upper airway dysfunction. Since hypercapnia increases the motor activity of airway dilating muscles its effects on the maximum expiratory and inspiratory flow-volume curves (MEIFV) in patients with obstructive sleep apnoea and in normal subjects in different postures was studied. The effects of posture on the maximum expiratory and inspiratory flow-volume curves during the breathing of air and 7% carbon dioxide in 11 patients with obstructive sleep apnoea were compared with those in nine normal subjects. Measurements were made in the sitting, supine, and right lateral recumbent positions. Forced expiratory flow at 50% vital capacity (FEF50), forced inspiratory flow at 50% vital capacity (FIF50) and FEF50/FIF50 were determined. In the normal subjects FEF50, FIF50, and FEF50/FIF50 were not affected by change in posture or by breathing carbon dioxide. In the patients there was a fall in FIF50 and an increase in FEF50/FIF50 when breathing air in the supine position compared with values in the seated and lateral position. While they were breathing carbon dioxide there was a slight increase in FEF50 when patients were seated or in the lateral position compared with values during air breathing. Hypercapnia abolished the effects of posture on FEF50/FIF50. Values for FEF50/FIF50 in the supine position while they were breathing air correlated with the apnoeic index but not with other polysomnographic data. In patients with obstructive sleep apnoea the upper airway is prone to collapse during inspiration when the patient is supine, even when awake; this tendency can be reversed by breathing carbon dioxide.

The biphasic spirogram: a clue to unilateral narrowing of a mainstem bronchus.

Two patients with narrowing of a mainstem bronchus each showed two unusual functional features that are likely to be characteristic of this condition. The maximum inspiratory flow-volume curve showed an end inspiratory "tail" and the forced expiratory spirogram had a biphasic shape with normal initial curvature but a "straight line" appearance in later expiration. In one patient relief of the bronchial stenosis by the insertion of a stent restored normal contours to the spirogram and flow-volume curves.

Maximal expiratory and inspiratory flow-volume curves in Parkinson's disease.

In order to investigate the type and degree of upper airway obstruction (UAO) in a group of patients with Parkinson's disease in different stages of the disease, we obtained maximal expiratory and inspiratory flow-volume (MEFV and MIFV) curves and maximal static mouth pressures. The clinical disability was indicated by a Hoehn-Yahr (H-Y) scale, ranging from III to V, and a more continuous Northwestern University Disability Scale (NUDS), ranging from zero to 50. Twelve patients were in H-Y Group III, and eleven and eight were in Groups IV and V, respectively. The pattern of the flow-volume curves was classified as either normal, or with superimposed regular or irregular oscillations (A), or with rounded-off and delayed expiratory peak appearance (B). Mean MEFV curves in Groups III and IV were not appreciably different from reference. In Group V, the mean curve showed a lower peak expiratory flow (PEF) and a more convex tail. Only the effort-dependent variables PEF, peak inspiratory flow (PIF), and maximal mouth pressures at RV and TLC (PmTLC and PmRV) appeared to be significantly correlated with the NUDS index and decreased with increasing clinical disability. The mean values of those variables were also significantly different between the H-Y groups. The number of normal curves decreased from H-Y Group III to Group V. The contribution of A and B curves was relatively equal in the groups, with only a small number of A curves.(ABSTRACT TRUNCATED AT 250 WORDS)

Maximum Flow Ratios at Mid-Vital Capacity in Young Healthy Adults

Upper airway obstruction is usually diagnosed by visual examination of maximum expiratory and inspiratory flow-volume curves and by calculating a ratio of expiratory to inspiratory flow at 50 percent of vital capacity (mid-vital capacity flow ratio); however, reference values of this ratio have not been well established, and considerable variability exists. The purpose of this study was to examine the range of mid-vital capacity flow ratios in a group of healthy subjects and to determine if some of the variability is accounted for by different maximum inspiratory pressures. We measured maximum expiratory and inspiratory flows at 50 percent of vital capacity from the flow-volume curves, and maximum inspiratory pressures in a group of 60 healthy nonsmokers (30 men and 30 women) whose ages ranged from 21 to 40 years. We found that mid-vital capacity flow ratio (mean +/- SD) was 0.72 +/- 0.19 in men and 0.77 +/- 0.18 in women. The coefficient of variation of the mid-vital capacity flow ratio was 28 percent for men and 23 percent for women. The 95 percent confidence limits for the mid-vital capacity flow ratio were 0.65 to 0.79 for men and 0.70 to 0.84 for women. Maximum inspiratory pressures (mean +/- SD) were 129 +/- 30 cm H2O in men and 91 +/- 16 cm H2O in women, not significantly different from previous studies. Normalizing maximum inspiratory flow for maximum inspiratory pressure did not reduce the coefficient of variation, which became 29 percent in men and 30 percent in women. We conclude that the range of mid-vital capacity flow ratios is wide, and it cannot be reduced by standardizing it for maximum inspiratory pressures.