Normal Airway Resistance Research Articles

Algorithm for Nasal Breathing Impairment Evaluation.

Assessing patients with complaints of nasal obstruction has traditionally been done by evaluation of the nasal airway looking for fixed or dynamic obstructive locations that could impair nasal airflow. Not infrequently, however, symptoms of nasal obstruction do not match the clinical examination of the nasal airway. Addressing this subset of patients may be a challenge to the surgeon. Evaluation of patients with symptoms of nasal obstruction should include a combination of a patient-reported assessment of nasal breathing and at least one objective method for measuring nasal airflow or nasal airway resistance or dimensions. This will allow distinction between patients with symptoms of nasal obstruction and low airflow or high nasal airway resistance and patients with similar symptoms but whose objective evaluation demonstrates normal nasal airflow or normal airway dimensions or resistance. Patients with low nasal airflow or high nasal airway resistance will require treatment to increase nasal airflow as a necessary step to improve symptoms, whereas patients with normal nasal airflow or nasal airway resistance will require a multidimensional assessment looking for less obvious causes of impaired nasal breathing sensation.

Comparison of ventilation techniques for compensation of mask leakage using a ventilator and a regular full-face mask: A bench study

BackgroundThe use of noninvasive ventilation (NIV) during and after extubation is common. We designed this study to determine the optimal strategy to compensate for mask leaks and achieve effective ventilation during NIV by comparing commonly used operating room ventilator systems and a regular facemask. MethodsWe tested four operating room ventilator systems (Dägger Zeus, Dägger Apollo, Dägger Fabius Tiro, and General Electric Healthcare Carestation 650) on a lung model with normal compliance and airway resistance and evaluated pressure control ventilation (PCV), volume control ventilation (VCV), and AutoFlow mode (VAF). We set the O2 flow at 10 L/min and the maximal flow at 13, 16, or 26 L/min. We simulated five leak levels, from no leak to over 40 L/min (I to V levels), using customized T-pieces placed between the lung model and the breathing circuit. We recorded the expired tidal volume (Vte) from the lung model and peak inspiratory pressure via two flow/pressure sensors that were placed distally and proximally to the T-pieces. Results1. Comparison of four ventilators: with any given ventilation mode, an increase in leak level caused a decrease in Vte. With PCV, only Zeus produced Vte larger than 150 ml at leak level V. 2. Effect of ventilation mode on Vte: across all four ventilators, PCV resulted in a higher Vte than VCV and VAF (P < 0.01). PCV mode with all ventilators at leak level II provided Vte values that were equal to or greater than those obtained with no leak. 3. Effect of O2 flow on Vte Using PCV mode: only Carestation 650 Vte at leak level II during PCV were significantly greater with 16 L/min O2 flow compared with 10 L/min O2 flow (P < 0.01). 4. Actual leak: increasing the O2 flow from 10 L/min to the maximum O2 flow dramatically increased the real leak with all 4 ventilators at any fixed leak level (P < 0.01). 5. Preset PIP vs. actual PIP with PCV: at low preset PIP and leak levels such as leak II and III, the discrepancy between preset PIP and actual PIP was small. The disparity between the preset and actual PIP grew when the target PIP and the leak level were raised. ConclusionFor NIV using a mask, the ventilator is preferred whose Pressure generator is Turbine, the PCV mode is preferred in the ventilation mode and the oxygen flow is set to 10 L/min or maximum oxygen flow.

Increased expiratory flows identify early interstitial lung disease.

Most interstitial lung diseases (ILDs) manifest with a restrictive ventilatory defect as the common physiologic abnormality. Low carbon monoxide diffusing capacity (Dlco) is considered to be the earliest abnormality on pulmonary function tests (PFTs) in patients with ILD. However, its measurement requires complex and expensive equipment. Our study aimed to assess if high expiratory flows are the earliest PFT abnormality in patients with idiopathic pulmonary fibrosis (IPF) and ILD. In a real-world cohort of incident cases with ILD, we identified the initial PFTs on all patients newly diagnosed with ILD at Kingston Health Sciences Center (in Kingston, Ontario, Canada) between 2013 and 2017. The diagnosis of ILD, including IPF, was established as per current guidelines. Among patients with normal forced vital capacity (FVC), total lung capacity (TLC), and Dlco, we assessed the frequency of high expiratory flows defined as forced expiratory volume in 1 s (FEV1)/FVC, FEF25, FEF25-75, FEF75, and peak expiratory flow > 95% confidence limit of normal. We adjusted for emphysema, increased airway resistance, and obesity. We assessed PFTs of 289 patients with ILD; 88 (30%) of them had normal FVC, TLC, and Dlco. Among these, high FEV1/FVC was the most common abnormality in 37% of patients, in 43% of nonobese patients, and in 58% of those with no emphysema and normal airway resistance. Results were similar in the 88 patients with IPF. High FEV1/FVC could allow identifying patients with ILD/IPF in the earliest stages of their disease with simple spirometry, leading to earlier diagnosis and treatment.

Impulse oscillometry to differentiate between chronic obstructive pulmonary disease and bronchial asthma

BackgroundThe impulse oscillation system (IOS) yields useful clinical data that predominantly include functional assessment of peripheral airways more than that available from commonly used spirometry. The aim of this study was to differentiate between chronic obstructive pulmonary disease (COPD) and bronchial asthma using IOS.Patients and methodsThis study was carried out on 40 patients; 20 patients were diagnosed with bronchial asthma and the remaining 20 patients had a clinical diagnosis of COPD. All patients underwent baseline IOS and spirometry, and then after 15 min of inhalation of 400 μg salbutamol, spirometry was repeated in all patients.ResultsA highly statistically significant difference was found between asthma patients and COPD patients in R20, whereas no statistically significant difference was found between the two studied groups in R5, X5. There was a statistically significant difference between asthma patients and COPD patients in resistance; 75% of asthmatic patients had increased total airway resistance, mainly proximal, 20% had increased total airway resistance, mainly peripheral, and 5% had normal airway resistance, whereas all COPD patients had increased total airway resistance, mainly peripheral. No significant correlation was found between IOS parameters and spirometric parameters in COPD or asthmatic patients, but in both groups, there was a significant correlation between forced expiratory volume 1 (FEV1) and R5, X5.ConclusionIOS provides useful clinical information that prominently includes functional assessment of small, peripheral airway behavior beyond that available from commonly used pulmonary function tests. IOS also aids differentiation between COPD and bronchial asthma. COPD patients had increased airway resistance, mainly in the peripheral airways, whereas asthmatic patients had increased airway resistance, mainly in the proximal airways. R20 is the best IOS parameter to differentiate between these two diseases.

Forced oscillometry track sites of airway obstruction in bronchial asthma

BackgroundSpirometry is the most commonly used method for assessment of airway function in bronchial asthma but has several limitations. Forced oscillometry was developed as a patient-friendly test that requires passive cooperation of the patient breathing normally through the mouth. ObjectiveTo compare spirometry with forced oscillometry to assess the role of forced oscillometry in the detection of the site of airway obstruction. MethodsThis case-and-control study included 50 patients with known stable asthma and 50 age- and sex-matched healthy subjects. All participants underwent spirometry (ratio of force expiration volume in 1 second to forced vital capacity, percentage predicted for forced expiration volume in 1 second, percentage predicted for forced vital capacity, percentage predicted for vital capacity, and forced expiratory flow at 25–75%) and forced oscillometry (resistance at 5, 20, and 5–20 Hz). ResultsBy spirometry, all patients with asthma had airway obstruction, 8% had isolated small airway obstruction, 10% had isolated large airway obstruction, and 82% had large and small airway obstruction. By forced oscillometry, 12% had normal airway resistance, 50% had isolated small airway obstruction with frequency-dependent resistance, and 38% had large and small airway obstruction with frequency-independent resistance. There was significant difference between techniques for the detection of the site of airway obstruction (P = .012). Forced oscillometry indices were negatively correlated with spirometric indices (P < .01). ConclusionForced oscillometry as an effortless test, conducted during quiet tidal breathing, and does not alter airway caliber; thus, it can detect normal airway function better than spirometry in patients with asthma. Forced oscillometry detects isolated small airway obstruction better than spirometry in bronchial asthma.

Relationship between hypostasis effect in the lung parenchyma on CT and small airway resistance: a preliminary study

Objective To investigate the correlation between hypostasis effect in the lung parenchyma on CT (HELC) and small airway resistance. Methods Forty-two consecutive patients and 6 volunteers without parenchyma pathologic change on CT or history of chest operation were enrolled in the study, which was approved by the hospital institution, and informed consent was obtained. CT scans of 3 slices with thickness 5 mm were performed at the levels of aorta arch, sub-bronchial carina and diaphragmatic dome in both supine and prone positions with smooth breathing and reconstruction of 1.25 mm. CT and pulmonary function test (PFT) studies were performed within 2 days. Patients were divided into two groups according to the ratio of the forced expiratory volume in 1 s and the forced vital capacity of predict% (FEV1.0/FVC%) as gold standard: group A (normal small airway resistance, SAR) with FEV1.0/FVC% ≥ 80%, and group B: (abnormal SAR) with FEV1.0/FVC% < 80%. Two senior radiologists blinded to PFT results reviewed CT images from PACS with consensus to identify and document hypostasis effect, defined as crescent-shaped ground glass in the dorsal subpleural lung parenchyma in supine and disappeared in prone position, shown in CT images. The number and frequency of cases with hypostasis effect on CT between the two groups were compared statistically with Chi square test. Result Thirty-three cases were in group A with FEV1/FVC of 92.0%±7.5% (80.4% to 105.2%), and 24 cases of them (66.7%) showed hypostasis effect on CT scans; 15 cases were in group B with FEV1.0/FVC% of 63.4%±10.0% (46.6% to 78.0%), and only 2 cases (13.3%) demonstrated hypostasis effect (χ2=14.653, P<0.01). Conclusions The rate of HELC appearance decreases with increasing of small airway resistance. Lack of hypostasis effect in lung CT imaging with smooth breathing during CT scan may reflect increased intra pulmonary pressure caused by airflow limitation, and may be used as a new indicator of COPD. Key words: Airway resistance; Pulmonary ventilation; Tomography, X-ray computed

Pulmonary stretch receptor spike time precision increases with lung inflation amplitude and airway smooth muscle tension

Slowly adapting pulmonary stretch receptors (SARs) respond to different lung inflation volumes with distinct spike counts and patterns, conveying information regarding the rate and depth of breathing to the cardiovascular and respiratory control systems. Previous studies demonstrated that SARs respond to repetitions of the same lung inflation faithfully, suggesting the possibility of modeling an SAR's discrete response pattern to a stimulus using a statistically based method. Urethane-anesthetized rabbit SAR spike trains were recorded in response to repeated 9-, 12-, and 15-ml lung inflations, and used to construct model spike trains using K-means clustering. Analysis of the statistics of the responses to different lung inflation volumes revealed that SARs fire with more temporal precision in response to larger lung inflations, because the standard deviations of real spikes clustered around the modeled spike times of responses to 15-ml stimuli were smaller than those produced by 12 or 9 ml, even at the same absolute firing frequencies. This implied that the mechanical coupling of SAR endings with pulmonary tissue is critical in determining spike time reliability. To test this, we collected SAR responses during bronchial constriction, compared them with those produced by the same SARs under normal airway resistance, and found that their firing reliability improved during bronchial constriction. These results suggest that airway distension and mechanical coupling of the receptor endings with the airway wall (partially determined by smooth muscle tone) are important determinants of SAR spike time reliability.

The spontaneous course of nasal obstruction in patients with normal nasal airway resistance

The spontaneous course of nasal obstruction in patients with normal nasal airway resistance

A new expiratory support system for resolving air trapping in lungs during mechanical ventilation: A lung model study

The aim of the study was to assess a new expiratory support (ES) system in resolving air trapping in the lungs during mechanical ventilation. The ES system consisted of a cylinder and two valves that were connected to the ventilatory circuit. The movements of them were synchronized with the ventilator. The cylinder aspirated gas during expiration. We compared the effects of the ES on air trapping between a narrower and an ordinary size endotracheal tube (ETT) (internal diameter (ID): 5 and 8 mm). In addition, we compared the effects of the ES on air trapping between normal and high airway resistance of the lungs (5 and 20 cm H(2)O/L/s). The ventilatory settings were as follows: volume controlled ventilation with constant inspiratory flow rate; tidal volume, 0.5 L; inspiratory time, 1.0 s; expiratory time, 1.0, 1.5, or 2.0 s; and PEEP, 0 cm H(2)O. The ES normalized the end-expiratory alveolar pressure of the 5 mm ID ETT at a level similar to that of the 8 mm ID ETT. The ES also resolved the air trapping induced by the high airway resistance of the lungs. In conclusion, the ES system resolved the air trapping associated with a narrow endotracheal tube and high airway resistance of the lungs.

Effect of lung mechanics on mechanically assisted flows and volumes.

To correlate the air flows generated by mechanical insufflation-exsufflation as a function of pressure delivery in a lung model at two pulmonary compliance and three airway resistance settings. With each combination of pulmonary compliances of 25 and 50 ml/cm H2O and airway resistances of 6, 11, and 17 cm H2O/liter/sec, ten cycles of mechanical insufflation-exsufflation were applied using pressure deliveries of 40 to -40, 50 to -50, 60 to -60, and 70 to -70 cm H2O. The resulting peak exsufflation flows and volumes were recorded. In a multivariate analysis, the pulmonary compliance, airway resistance, and pressure delivery were all found to significantly affect exsufflation flows and volumes such that a decreased pulmonary compliance or an increased airway resistance produced a decrease in exsufflation flow and volume, whereas an increased pressure delivery produced greater exsufflation flow and volume. Although mechanical insufflation-exsufflation pressures of 40 to -40 cm H2O are generally adequate for most patients with normal lung compliance and airway resistance, higher settings are often required when compliance decreases, by obesity or scoliosis, and possibly when airway resistance is increased.

Variability of respiratory effort in relation to sleep stages in normal controls and upper airway resistance syndrome patients

Objective: Investigation of the role of sleep states on the respiratory effort of controls and subjects with upper airway resistance syndrome (UARS) using nasal cannula/pressure transducer system and esophageal manometry. Patients and methods: One night's monitoring of sleep and breathing, including the determination of peak end inspiratory esophageal pressure (respiratory effort) with esophageal manometry and flow limitation with nasal cannula. Analysis of the data, breath-by-breath, using visual inspection and a computerized program. Setting – a university sleep laboratory. Patients were nine men with UARS and nine control men matched for age, ethnicity, and body mass index. Results: A modulation of respiratory effort by sleep state and stages is seen in all subjects, the lowest noted during REM sleep and the highest associated with Slow Wave Sleep. When total nocturnal breaths are investigated, a significant difference between peak end inspiratory esophageal pressure [(Pes)-considered as an index of respiratory effort] is noted between normal subjects and UARS. Two specific breathing patterns, seen primarily in UARS patients, are NREM sleep stage dependent. Crescendos (defined as more negative peak end inspiratory Pes with each successive abnormal breath) occur mostly during stages 1–2 NREM sleep, while segments consisting of regular and continuous, breath-after-breath, high respiratory efforts are associated with Slow Wave Sleep. Depending on sleep stage, visually scored arousal response displays differences in Pes negativity. The termination of the abnormal breathing pattern, always well defined with Pes, is not necessarily associated with a pattern of ‘flow limitation’ at the nasal cannula tracing, even when a visually scored EEG arousal is present. Conclusions: UARS patients have significantly more breaths, with more negative peak end inspiratory Pes, than do control subjects. The modulation of peak end inspiratory Pes (an index of respiratory effort) by sleep stage and state differs in UARS patients and control subjects. The nasal cannula/pressure transducer system may not detect all abnormal breathing pattern during sleep. As indicated by the visual sleep scoring, repetitive arousals may lead to more or less severe sleep fragmentation.

Persistent Cough in an Adolescent

Jessica, a 14-year-old girl with a history of asthma, went to her pediatrician's office because of a persistent cough. She had been coughing for at least 3 months with occasional cough-free periods of less than a few days. The cough was nonproductive and was not accompanied by fever, rhinorrhea, or facial or chest pain. Jessica and her mother observed that the cough increased with exercise and typically was not present during sleep. She has used two metered-dose inhalers--albuterol and cromolyn--without any change in the cough pattern. For the past 5 years, Jessica has had mild asthma responsive to albuterol. She enjoys running on the cross-country team, soccer, and dancing. She is an average student and denies any change in academic performance. She has never been hospitalized or had an emergency department visit for asthma or pneumonia. There has been no recent travel or exposure to a person with a chronic productive cough, tobacco smoke, or a live-in pet. Jessica lives with her mother and younger sister in a 10-year-old, carpeted apartment without any evidence of mold or recent renovation. In the process of taking the history, the pediatrician noticed that Jessica coughed intermittently, with two or three coughs during each episode. At times, the cough was harsh; at other times, it was a quiet cough, as if she were clearing her throat. She was cooperative, without overt anxiety or respiratory distress. After a complete physical examination with normal findings, the pediatrician interviewed Jessica and her mother alone. Jessica's parents had been divorced for the past 6 years. She lived with her mother but visited her father, and his new family with two young children, every weekend. She spoke about this arrangement comfortably and said that she loved her father and mother but didn't like the tension she experienced at her father's home. "I don't like adults arguing when kids are around." When asked why she thought the cough persisted so long, she commented in a neutral tone, "I don't know. It's never been like this before." Jessica's pediatrician prescribed an inhaled steroid with the albuterol. When the cough did not respond after 1 week, he ordered a chest radiograph (normal) and a tuberculin skin test (purified protein derivative-negative), and he added montelukast (a leukotriene inhibitor) and monitored airway resistance with a peak flow meter. The cough persisted, and the peak flow recording showed normal airway resistance. At this time, Jessica's pediatrician suspected a conversion reaction and contemplated the next best therapeutic strategy.

LUNG DEPOSITION AND EXTREMELY SLOW INHALATIONS OF PARTICLES. LIMITED EFFECT OF INDUCED AIRWAY OBSTRUCTION

Studies of lung deposition and clearance have focused on the large airways. Still, lung diseases affect also the small airways. We have developed a method for selective particle deposition in the smallest ciliated airways. Eight healthy subject inhaled 6-mum radiolabelled test particles on 3 occasions at 0.05 L/s and retention was measured for 72 hours. At one occasion, the subjects inhaled the particles at a normal airway resistance. At a second occasion, a 2-3-fold increase in airway resistance was induced by a cholinergic provocation before inhalation of the particles. At a third occasion, a corresponding provocation was induced after inhalation of the particles. The percentage lung depositions were 76+/-7, 68+/-7, and 73+/-8 (mean +/- SD) for ''normal airway resistance,'' ''provocation before,'' and ''provocation after'' exposures, respectively. The lower value for the ''provocation before'' exposure was probably a result of increased mucociliary clearance, due to cholinergic stimulation, before the first measurements of radioactivity. The retentions at 24 hours were 51+/-7, 52+/-9, and 51+/-8 in percent of initial lung deposition for ''normal airway resistance,'' ''provocation before,'' and ''provocation after'' exposures, respectively. We conclude that our inhalation technique is useful in studying conditions in the bronchioles, as deposition is rather independent of airway resistance.

Expression of interleukin 9 in the lungs of transgenic mice causes airway inflammation, mast cell hyperplasia, and bronchial hyperresponsiveness.

Interleukin (IL)-9, a pleiotropic cytokine produced by the Th2 subset of T lymphocytes has been proposed as product of a candidate gene responsible for asthma. Its wide range of biological functions on many cell types involved in the allergic immune response suggests a potentially important role in the complex pathogenesis of asthma. To investigate the contributions of IL-9 to airway inflammation and airway hyperresponsiveness in vivo, we created transgenic mice in which expression of the murine IL-9 cDNA was regulated by the rat Clara cell 10 protein promoter. Lung selective expression of IL-9 caused massive airway inflammation with eosinophils and lymphocytes as predominant infiltrating cell types. A striking finding was the presence of increased numbers of mast cells within the airway epithelium of IL-9-expressing mice. Other impressive pathologic changes in the airways were epithelial cell hypertrophy associated with accumulation of mucus-like material within nonciliated cells and increased subepithelial deposition of collagen. Physiologic evaluation of IL-9-expressing mice demonstrated normal baseline airway resistance and markedly increased airway hyperresponsiveness to inhaled methacholine. These findings strongly support an important role for IL-9 in the pathogenesis of asthma.

Jet Ventilation Using Fiberoptic Bronchoscopes

A fiberoptic bronchoscope is used to facilitate tracheal intubation in cases of difficult direct laryngoscopy.Occasionally, difficulty is encountered in advancing the endotracheal tube after the fiberoptic bronchoscope has been introduced into the trachea. This study tested the feasibility of providing jet ventilation through the suction channel of the fiberoptic bronchoscope as an interim measure under those or similar circumstances. Three commercial models of fiberoptic bronchoscopes with suction channels of 1.2-, 1.5-, and 2-mm diameter, respectively, were tested in a mechanical test lung at varying compliances and resistances using a jet injector connected to an oxygen source at 50 psi. The fiberoptic bronchoscope with the 2-mm suction channel was also studied in seven adult patients who were anesthetized and paralyzed. Jet ventilation was manually performed at the rate of 12/min for 10 min. In the mechanical test lung, the tidal volumes with 1.2-, 1.5-, and 2-mm suction channels were as follows: 280 mL, 490 mL, and 880 mL, respectively, at a compliance of 50 mL/cm H2 O and normal resistance; 260 mL, 470 mL, and 820 mL, respectively, at a compliance of 50 mL/cm H2 O and high resistance to simulate bronchospasm; 130 mL, 270 mL, and 890 mL, respectively, at a compliance of 20 mL/cm H2 O and normal resistance; 120 mL, 220 mL, and 810 mL, respectively, at a compliance of 20 mL/cm H2 O and high resistance. In anesthetized, paralyzed patients, oxygen saturation was 96% or more throughout the study. PaO2, PaCO2, and pHa at the end of 10 min of jet ventilation were 374 +/- 121 mm Hg, 36 +/- 12 mm Hg, and 7.41 +/- 0.05, respectively. We conclude that effective jet ventilation can be provided using fiberoptic bronchoscopes with a suction channel 2 mm in diameter in most anesthetized, paralyzed adult patients. From the results in the mechanical lung, we also predict that effective jet ventilation can be performed in patients with normal compliance and airway resistance using a fiberoptic bronchoscope with a suction channel 1.2 mm in diameter. (Anesth Analg 1995;80:384-7)

Tracheomalacia repair using ceramic rings.

Tracheomalacia resulting from tracheostomy or compressive thyroid disease often represents a difficult problem in airway management. In an attempt to improve this condition, biocompatible ceramic rings were surgically implanted in 16 patients to restore normal patency of the airway by first expanding the tracheal lumen lateral, and then in an anterior dimension. Preoperatively, patients displayed moderate to severe obstruction with marked restrictions in lifestyle, as confirmed by history, physical examination, and airway resistance studies. Additionally, three of these patients were trach-dependent at the time of implantation. Postoperatively all 16 patients have normal airway resistance parameters with a dramatic improvement in lifestyle, whereas the three with tracheostomy were successfully decannulated. The routine use of these rings has alleviated the need for rib/cartilage grafts, primary resections with anastomosis, prolonged periods of cannulation, and multiple surgeries. Our experience in the use of ceramic rings for tracheomalacia repair will be presented, highlighting selection criteria for their use, intraoperative placement, perioperative complications, and post-operative followup for a minimum of 6 months.

Functional Laryngeal Obstruction Relieved by Panting

A 49-year-old man presented with a two-day history of severe recurrent dyspnea and inspiratory stridor. A chest roentgenogram, computed tomographic scan of the neck, direct laryngoscopy, and bronchoscopy excluded organic upper airway obstruction. Laryngospasm occurred during the bronchoscopy. Although flow volume loops revealed severe upper airway obstruction (inspiratory and expiratory), airway resistance measured plethysmographically (during panting) was normal. Because of this observation, panting was recommended for relief of the patient's recurrent attacks of functional laryngeal obstruction. The panting maneuver immediately and completely relieved all 25 to 30 subsequent attacks. After the patient recovered clinically, a flow volume loop was repeated and was found to be normal. The marked discrepancy between severe flow limitation (as detected by flow volume loops) and normal airway resistance (measured plethysmographically) may be a diagnostic test for functional laryngeal obstruction, and panting may be an effective emergency measure for its relief. Relief by panting may also suggest the diagnosis. A second patient with an almost identical symptom complex is described, in whom the panting maneuver was also dramatically successful in promptly aborting recurrent severe attacks of airway obstruction and stridor.

The spontaneous course of nasal obstruction in patients with normal nasal airway resistance

Sixty-seven patients, candidates for septoplasty in the years 1976-1978 because of nasal obstruction and deviated nasal septum, but not having surgery because their nasal airway resistance was normal, were reviewed in 1982 and again in 1989. Between 1982 and 1989, 6% of the patients became free of their respective nasal complaints, and 18% of their nasal obstruction, the corresponding overall figures for the period between 1976 and 1978, and 1989, being 20 and 36%. In fact, the majority of the patients were suffering from vasomotor rhinitis and because in so many cases nasal obstruction tends to disappear as time goes on, a conservative waiting policy would seem to be an appropriate approach to treatment.

Normal nasal airway resistance in noses of different sizes and shapes

Measurement of nasal airway resistance is becoming a common clinical technique. Accurate definition of the normal range of airflow is critical for maximal usefulness of this technique. Since typical nasal size and shape vary greatly with ethnic background, different norms for different ethnic groups may be appropriate. Nasal airway flow and resistance and external nasal size and shape were measured in 130 asymptomatic subjects (52 black, 56 white, and 22 Hispanic). Nasal length, width, columellar length, and nasolabial angle were similar for whites and Hispanics, but both groups differed significantly from blacks--even when changes attributable to biologic aging were factored out. In spite of these differences, there was no significant difference in any nasal airflow or resistance parameter among groups, suggesting that currently used airflow and resistance standards are valid for these three different ethnic groups.

Joint and Pulmonary Changes in Diabetes-Reply

In Reply.—We appreciate the additional information offered by Dr Madacsy. His findings1were consistent with those of our studies.2As he suggested, we did analyze our data to compare the vital capacities between diabetic patients with LJM and those without LJM, but we found no significant difference between the two groups by Χ2, multiway table, or linear regression analysis. In a previous study of three diabetic patients with severe LJM, we performed detailed pulmonary function tests, including spirometry, body plethysmography, nitrogen washout curves, and arterial blood gas measurements.3In these patients, we demonstrated decreased vital capacities, decreased total lung capacities, an abnormal slope of phase III of the nitrogen washout curve, and abnormal oxygenation; however, the patients had normal airway resistance and normal PEF50and, therefore, had no evidence of obstructive airway disease. To examine a large number of children (N = 375) at a