Upper Airway Obstruction

doi:10.1378/chest.80.2.207

Chest

Volume 80, Issue 2, August 1981, Pages 207-211

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PHYSIOLOGY

The airway may be divided functionally into the following three levels: first, peripheral airways of 2 mm diameter or less; second, larger or major airways from 2 mm diameter up to the main carina; and third, the upper airways which include the trachea, larynx, pharynx, and nose or mouth. The effects of any obstruction of the upper airways will depend on several variables which include (a) the size of the airway at the site of the obstruction, (b) the location of the obstruction, (c) the nature

LABORATORY FEATURES

In normal subjects during a forced expiration from total lung capacity (TLC), the maximum airflow is achieved during the first 25 percent of the vital capacity (VC) and is directly dependent on effort and inversely on resistance. In the remaining 75 percent of the VC, flow is limited in such a way that an increase in effort with its associated increase of pleural pressure does not result in increased flow. The precise mechanism of flow limitation over the lower 75 percent of the VC is the

FLOW VOLUME LOOP

Miller and Hyatt³ suggested that the flow volume plot of a forced expiratory and inspiratory vital capacity maneuver would be particularly helpful in categorizing UAO. They simulated major airway obstruction by having normal subjects breathe through fixed resistances and found that flow rate increased to a certain level early in both inspiration and expiration and then plateaued. The plateau was reached at lower flow rates as the resistances were progressively increased (Fig 4).

The effect of a

SPIROMETRY

A simple plot of a FVC maneuver of volume vs time, the timed spirogram, will also give some clues to the presence of upper airway obstruction.³ Figure 6 shows the spirogram and flow volume loop from a patient with an intrathoracic variable obstruction (a paratracheal tumor). The linear portion of the spirogram indicates constant flow which is equivalent to the plateau (ie, constant flow) of the flow volume loop. For comparison, a spirogram from a normal subject is shown on the right.

Rotman et al

MIXED UPPER AND LOWER AIRWAY OBSTRUCTION

The combination of CAO and UAO may arise in several circumstances, for instance, tracheal stenosis occurring after tracheal intubation for an episode of respiratory failure in a patient with chronic airflow obstruction (CAO). Using principles outlined below, the presence of UAO in patients with lower airflow limitation may be distinguished.

In the upper airways, flow is turbulent and depends on the density of the gas, whereas in peripheral airways, flow is laminar and independent of gas density.⁵

DISTRIBUTION OF VENTILATION AND BRONCHODILATOR RESPONSE

In the presence of UAO without peripheral airway obstruction, tests of distribution of ventilation such as the nitrogen washout are normal.⁸ A marked elevation in airway resistance unresponsive to bronchodilators is also often seen in patients with UAO. The combination of a normal nitrogen washout and elevated airway resistance in a patient complaining of wheezing or dyspnea should lead one immediately to suspect upper airway obstruction as the cause.

OTHER LABORATORY FEATURES

Resistance in any tube can be measured by dividing the pressure drop along the tube by the flow. In man, resistance across the upper airway is about 1 cm H₂O/L/sec, whereas most patients with symptomatic UAO are found to have a resistance between 4 and 15 cmH₂O/L/sec while breathing quietly. The resistance of the upper airway is not constant and with increasing flow (such as during exercise), there is a disproportionate rise in the resistance, probably explaining the dyspnea on exertion of

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REFERENCES (10)

HH Rotman et al.
Diagnosis of upper airway obstruction by pulmonary function testing.
Chest
(1975)
MA Sackner
Physiologic features of upper airway obstruction.
Chest
(1972)
M Kryger et al.
Diagnosis of obstruction of the upper and central airways.
Am J Med
(1976)
F Al-Bazzaz et al.
Respones to exercise in upper airway obstruction.
Am Rev Respir Dis
(1975)
B Geffin et al.
Stenosis following tracheostomy for respiratory care.
JAMA
(1971)

There are more references available in the full text version of this article.

Cited by (60)

Non-malignant central airway obstruction
2014, Archivos de Bronconeumologia
Citation Excerpt :
Pulmonary function tests are useful for both diagnosis and follow-up after an intervention. In the case of tracheal stenosis, a trend toward flattening of the inspiratory and expiratory flow-volume loop is observed, depending on the site and characteristics of the lesion.7 This change is not normally seen until the tracheal lumen measures less than 10 mm.
The most common causes of non-malignant central airway obstruction are post-intubation and post-tracheostomytracheal stenosis, followed by the presence of foreign bodies, benign endobronchial tumors and tracheobronchomalacia. Other causes, such as infectious processes or systemic diseases, are less frequent. Despite the existence of numerous classification systems, a consensus has not been reached on the use of any one of them in particular. A better understanding of the pathophysiology of this entity has allowed us to improve diagnosis and treatment. For the correct diagnosis of nonspecific clinical symptoms, pulmonary function tests, radiological studies and, more importantly, bronchoscopy must be performed. Treatment must be multidisciplinary and tailored to each patient, and will require surgery or endoscopic intervention using thermoablative and mechanical techniques.
Las causas más frecuentes de patología obstructiva no maligna de la vía aérea central son las estenosis postintubación y postraqueotomía, seguidas por los cuerpos extraños y la traqueobroncomalacia. Otras causas, como las secundarias a procesos infecciosos y enfermedades sistémicas, son menos frecuentes. A pesar de la existencia de numerosas clasificaciones, todavía no se ha alcanzado consenso sobre la utilización de alguna de ellas en concreto. Un mejor conocimiento de su fisiopatología nos ha permitido aumentar el diagnóstico y mejorar su tratamiento; su presentación clínica inespecífica exige la realización de diversos estudios funcionales, radiológicos y fundamentalmente endoscópicos para su correcto diagnóstico. El tratamiento debe ser multidiciplinario e individualizado, requiriendo tratamiento quirúrgico o endoscópico mediante diferentes técnicas termoablativas y mecánicas.
Anesthesia for Tracheal Resection and Reconstruction
2012, Anesthesiology Clinics
Citation Excerpt :
Intrathoracic compromise occurs in expiration when thoracic pressure is above tracheal pressure. In contrast, the emphysematous pattern of small airway collapse occurs in expiration and later in exhalation.11–13 Spontaneous ventilation is better tolerated with intrathoracic lesions because thoracic pressure drops below tracheal pressure during inspiration.
Inspiratory airflow limitation after exercise challenge in cold air in asthmatic children
2012, Respiratory Medicine
Citation Excerpt :
Analysis of the inspiratory flow limb is difficult, especially in children. The MIF50 can be used to analyze inspiratory flow limitation in children17,21 and Tomalak and co-workers have calculated reference values for children.17 The observed mean pre-exercise MIF50 was approximately 1 standard deviation above predicted, which indicates that the children in our study were capable of performing technically acceptable flow volume loops.
Methacholine and histamine can lead to inspiratory flow limitation in asthmatic children and adults. This has not been analyzed after indirect airway stimuli, such as exercise. The aim of the study was to analyze airflow limitation after exercise in cold, dry air.
72 asthmatic children with mild to moderate asthma (mean age 13.2 ± 2.2 yrs) performed a treadmill exercise challenge. A fall of >10% in FEV₁ was the threshold for expiratory flow limitation and a fall of >25% of MIF₅₀ was the threshold for inspiratory flow limitation. The occurrence of wheeze, stridor and cough were quantified before and after exercise.
After exercise, the mean fall in FEV₁ was 17.7 ± 14.6%, while the mean fall in MIF₅₀ was 25.4 ± 15.8%; no correlation was found between fall in FEV₁ and MIF₅₀ (R²: 0.04; p = 0.717). 53 of the 72 children showed an inspiratory and/or expiratory airflow limitation. 38% (20/53) of these children showed an isolated expiratory flow limitation, 45% (24/53) showed both expiratory and inspiratory flow limitation and 17% (9/53) showed an isolated inspiratory flow limitation. The fall in FEV₁ peaked 9 min after exercise and correlated to expiratory wheeze. The fall in MIF₅₀ peaked 15 min after exercise and correlated to inspiratory stridor. The time difference in peak fall between FEV₁ and MIF₅₀ was statistically significant (5.9 min; p < 0.001, 99% CI: 2.3–9.5 min).
In conclusion, this study shows that an exercise challenge in asthmatic children can give rise to inspiratory airflow limitation, which may give rise to asthma like symptoms.
Biphasic flow volume curve due to obstruction of main bronchus by bronchogenic cyst
2011, Respiratory Medicine CME
Citation Excerpt :
Currently the curve flow volume is determined during the forced expiratory maneuver, along with the curve volume/time for most commercially available spirometers. It is a simple test that, if properly interpreted, helps locate the site of the obstruction.10–20 Moreover, the flow/volume curve is used for monitoring the evolution of lung transplant patients anastomosis,6,7 as it is a simple test that can be repeated often avoiding bronchoscopy.
The biphasic curve or bicompartmental flow volume obtained during the forced maneuver is the characteristic of the obstruction of a main bronchus. We report the case of a 64-year-old woman, with progressive dyspnea, coughing and wheezing localized in the left hemithorax, who had been diagnosed with bronchial asthma and was not responding to treatment. The flow volume curve showed an end inspiratory arm configuration compatible with unilateral obstruction of a main bronchus. Chest computed tomography with three-dimensional reconstruction showed a left main bronchus compression by a cyst formation, the bronchoscopy confirmed the obstruction. At surgery a bronchogenic cyst was resected.
After the procedure, dyspnea, cough, expectoration and wheezing disappeared. The postoperative flow volume curve showed a normal configuration. We are not aware of a previous report of a biphasic flow volume curve due to a mediastinal bronchogenic cyst.
The flow volume curve is a noninvasive procedure useful in the diagnosis of unilateral obstruction of a main bronchus.
Consensus document on spirometry in Andalusia
2009, Semergen
Role of the impulse oscillometry in the evaluation of tracheal stenosis
2018, Pulmonology
Citation Excerpt :
Spirometry, however, is not always feasible in patients with UAO, due to patient-related factors that do not allow or interfere with an optimal forced expiratory manoeuvre (e.g. severe dyspnoea, cough, fatigue, language barrier, cooperation and cognitive impairment). Furthermore, significant changes in spirometry appear relatively late in the course of the upper airway narrowing process9 and spirometry values may not correlate with the degree of airway narrowing.10,11 These observations indicate the need for a method that can detect UAO and specifically tracheal stenosis in high risk patients.
Tracheal stenosis is a rare and challenging disease. Bronchoscopy is the gold standard for diagnosis and assessment but brings inherent risks. Spirometry is commonly used to access obstructions but is not always feasible due to patient related factors. We therefore considered impulse oscillometry (IOS) as a non-invasive method to quantify airway obstruction and its potential use for diagnosis and follow-up of tracheal stenosis.
Patients with confirmed tracheal stenosis were recruited between January 1st, 2015 and December 31st, 2016. Before bronchoscopy, all subjects underwent IOS and spirometry; for patients submitted to interventional bronchoscopy the same techniques were also performed after the procedure. We assessed the correlation between IOS measurements and airway narrowing as well as between IOS and spirometry values.
Twenty-one patients were included. Tracheal narrowing was inversely correlated with X5% (r −0.442, p 0.045) and positively correlated with FEV1/PEF (r 0.467, p 0.033). The stenosis length was inversely correlated with PEF and PEF% (r −0.729, p = 0.001 and r −0.707, p = 0.002, respectively). There was a strong correlation between spirometric and IOS values. We did not find any significant differences between pre- and post-intervention IOS values for patients assessed after interventional bronchoscopy.
Our study showed a weak correlation between X5% and tracheal narrowing making it unclear whether IOS can be used for physiological assessment of patients with tracheal stenosis. Stenosis length correlated with PEF making it a potential predictor of successful surgical approach. The correlation between IOS and spirometric values makes IOS a potential alternative in patients with suspected tracheal stenosis who are not able to perform spirometry. Larger scale studies should clarify the role of IOS in this pathology.

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Chest

Clinical Significance of Pulmonary Function TestsUpper Airway Obstruction

Section snippets

PHYSIOLOGY

LABORATORY FEATURES

FLOW VOLUME LOOP

SPIROMETRY

MIXED UPPER AND LOWER AIRWAY OBSTRUCTION

DISTRIBUTION OF VENTILATION AND BRONCHODILATOR RESPONSE

OTHER LABORATORY FEATURES

First page preview

Chest

Chest

Am J Med

Respones to exercise in upper airway obstruction.

Am Rev Respir Dis

Stenosis following tracheostomy for respiratory care.

JAMA

Clinical Significance of Pulmonary Function Tests
Upper Airway Obstruction