Upper Airway Obstruction BY AHMAD YOUNES PROFESSOR OF THORACIC MEDICINE

1. Upper Airway Obstruction BYAHMAD YOUNESPROFESSOR OF THORACIC MEDICINE Mansoura Faculty of Medicine

2. Upper Airway Obstruction • Upper airway is the segment of the conducting airways that extends between the nose (during nasopharyngeal breathing) or the mouth (during oropharyngeal breathing)and the main carina, located at the distal end of the trachea. • Physiological points of narrowing are the nostrils, the velopharyngeal valve (at the passage between the nasopharynx and oropharynx), and the glottis. • Malignant etiologies and benign strictures related to airway interventions are becoming more prevalent.

3. Upper Airway Obstruction • Common etiologies of upper airway obstruction in adults include infection, inflammatory disorders, trauma, and extrinsic compression related to pathology of adjacent structures. • Definitive management depends on the underlying etiology and may include both medical and surgical interventions.

4. HISTORICAL PERSPECTIVE • In the mid-sixteenth century, the first successful tracheostomy was performed to relieve upper airway obstruction caused by a pharyngeal abscess. • In the early nineteenth century, the procedure was used to treat croup, and diphtheria. • By the turn of the twentieth century, rigid bronchoscopy was used to remove a foreign body from the trachea. • Ikeda introduced the flexible bronchoscope in 1967.

5. HISTORICAL PERSPECTIVE • Malignancy become more prevalent with increasing tobacco use and exposure to modern environmental toxins. • Complications of endotracheal intubation and tracheostomy have become well recognized causes of benign upper airway stenosis. • Improvement in pharmacologic agents to treat infectious, inflammatory, and malignant etiologies, as well as developments in radiation oncology, have had significant effects on management of upper airway obstruction. • Development of new endoscopic and imaging techniques and introduction of interventional pulmonology also have proved useful in the management of upper airway obstruction.

6. Upper and Lower Airway Obstruction • The causes of upper airway obstruction are considerably less common than diseases of the lower airways, such as chronic COPD and asthma. • Symptoms (e.g., dyspnea, noisy breathing,) and clinical signs (e.g., wheezing, diminished breath sounds) may be identical, leading to diagnostic confusion. • Since COPD and asthma are much more common, they are often assumed to be the cause of the patient’s symptoms. • When the obstruction develops acutely, asphyxia and death may result within minutes to hours. • Therapy for acute asthma or an exacerbation of COPD is ineffective in this setting . • When upper airway obstruction develops slowly,a delay in diagnosis may predispose patients to unnecessary complications, including bleeding or respiratory failure, and, in the case of an upper airway malignancy, to advanced and incurable disease.

7. Symptoms and Signs of Upper Airway Obstruction • The main symptoms of upper airway obstruction are dyspnea and noisy breathing. • These symptoms are especially prominent during exercise and also may be aggravated by a change in body position. • The patient may complain that breathing is labored in the recumbent position and may have a severely disrupted sleep pattern. • Upper airway obstruction in such patients causes sleep apnea syndrome, which may resolve completely when the obstruction is relieved. Therefore, daytime somnolence may be a prominent feature of upper airway obstruction. • In severely affected patients, cor pulmonale may occur as a result of chronic hypoxemia and hypercarbia.

8. Symptoms and Signs of Upper Airway Obstruction Typically, significant anatomic obstruction precedes overt symptoms. For example, by the time exertional dyspnea occurs, the airway diameter is likely to be reduced to about 8 mm. Dyspnea at rest develops when the airway diameter reaches 5 mm, coinciding with the onset of stridor. Stridor is a loud ,musical sound of constant pitch that usually connotes obstruction of the larynx or upper trachea. Sound recordings from the neck and chest have shown that the sound signals from the asthmatic wheeze and stridor are of similar frequency. This explains why errors in diagnosis can be made and an upper airway obstruction due to a tumor or foreign body may be mistakenly treated as asthma.

9. Symptoms and Signs of Upper Airway Obstruction • Unlike wheezing, which is characteristic of diffuse lower airway narrowing and occurs predominantly during expiration, the musical sounds of stridor usually occur during inspiration and are heard loudest in the neck. • Neck flexion may change the intensity of stridor, suggesting a thoracic outlet obstruction. • When the obstructing lesion is below the thoracic inlet, both inspiratory and expiratory stridor may be heard. • Hoarseness may be a sign of a laryngeal abnormality. • Muffling of the voice without hoarseness may represent a supra-glottic process.

10. Physiological Assessment • Physiological abnormalities do not become apparent on lung function testing until severe obstruction occurs. • Upper airway obstruction must narrow the airway lumen to < 8 mm in diameter in order to produce abnormalities on a flow-volume loop. This corresponds to an obstruction of > 80 % of the tracheal lumen. • FEV1 remains above 90 %of controluntil a 6-mm orifice is created. Therefore, spirometry may not be an effective way to detect upper airway abnormalities. • The peak expiratory flow rate (PEFR) and maximal voluntary ventilation (MVV) are more sensitive than the FEV1 in detecting upper airway obstruction.

11. Flow-volume loop • During a forced expiratory maneuver from total lung capacity (TLC), the maximal flow achieved during the first 25 percent of the forced vital capacity is dependent on effort, i.e., an increase in driving pressure (effort) may result in increased flow. • During the remaining 75 percent of the forced vital capacity maneuver, flow is determined by the mechanical properties of the lungs and is not effort dependent. • During this portion of forced exhalation ,a linear deceleration of flow is caused by dynamic compression of the intra-thoracic airways. An increase in effort and therefore pleural pressure causes further compression of the intrathoracic airways and a further limitation of airflow.

12. Normal flow-volume loop following maximal expiratory (above) and inspiratory (below) effort. Small vertical lines denote seconds.

13. Flow-volume loop • At higher lung volumes, flow may be limited by an upper airway obstruction. • At low lung volumes, flow may not be affected by an upper airway obstruction, since measurement of flow in this effort-independent portion of the curve represents the function of the peripheral airways. • Since the FEV1 reflects a large portion of flow at these lower lung volumes ,it is not a sensitive test for upper airway obstruction. • Because the PEFR reflects flow at higher lung volumes, it may be abnormal when the FEV1 is not. • Forced inspiratory flow is limited by effort during the entire inspiratory maneuver. Flow increases from RV to near the mid-portion of the curve, where it becomes maximal at the peak inspiratory flow rate. Flow then declines until TLC is reached.

14. Flow-volume loop • The turbulent non-laminar airflow, which occurs during forced inspiration and causes airway pressure to fall in this portion of the airway, favors slight narrowing of the extra-thoracic airway. • Peak inspiratory flow, therefore, is < peak expiratory flow in normal subjects. • Because of the dynamic compression of the intra-thoracic airways that occurs during exhalation, flow during the middle of inspiration, i.e., the FIF50%,is usually > FEF50%. • Typical patterns of the flow-volume loop may be seen, depending on whether the obstruction to flow is “fixed” or “variable,” and whether the site of the obstruction is above or below the thoracic outlet or supra-sternal notch.

16. Fixed obstructions of the upper airway • Fixed obstructionsof the upper airway are those whose cross-sectional area does not change in response to trans-mural pressure differences during inspiration or expiration. • A fixed obstruction may occur in either the intra-thoracic or extra-thoracic airways. • Irrespective of the site of the obstruction, a fixed lesion results in the flattening of the flow-volume loop. • Non-distensible narrowing of the upper airway (fixed airway obstruction) occur in benign and malignancy strictures.

17. Fixed obstructions of the upper airway • Maximal inspiratory and expiratory flow-volume loops with fixed obstruction show constant flow, represented by a plateau during both inspiration and expiration • On the expiratory curve, the plateau effect is seen in the effort-dependent portion of the curve near TLC; very little change is noted in the effort-independent portion near residual volume. • Since the inspiratory curve is similar in appearance, the ratio of FEF50% to FIF50% is normal (close to 1). • The FIV1 and FEV1 are nearly the same in fixed upper airway obstruction.

18. CT of the neck shows a laryngeal abscess with significant impingement on the laryngeal inlet. The flow-volume loop demonstrates a plateau of flow during inspiration and expiration, the FEF50%/FIF50% ratio is near 1.

19. Variable extrathoracic airway obstruction • A variable obstructionis one that eliciting varying degrees of obstruction during the respiratory cycle. • Vocal cord paralysis is a common cause of variable extrathoracic obstruction. • A variable extrathoracic airway obstruction increases the turbulence of inspiratory flow, and intraluminal pressure falls markedly below atmospheric pressure. This leads to partial collapse of an already narrowed airway and a plateau in the inspiratory flow loop. • Expiratory flow is not significantly affected, since the markedly positive pressure in the airway tends to decrease the obstruction. • The ratio of FEF50% to FIF50% is high (usually > 2). • Similarly, the FEV1 is > the FIV1.

20. Variable extrathoracic obstruction due to thyroid cyst. A. CT of the neck shows a 10- × 4-cm cystic mass (large arrow) in the thyroid gland compressing the trachea (small arrow).B . Flow-volume loop shows inspiratory obstruction.FEF50%/FIF50% is very high, and the inspiratory curve is flattened.

21. variable intrathoracic airway obstruction • A variable obstruction in the intrathoracic airways show predominant reduction in maximal expiratory flow is associated with a relative preservation of maximal inspiratory flow. • This association occurs because intrapleural pressure becomes markedly positive during forced expiration and causes dynamic compression of the intrathoracic airways. • The obstruction caused by an intrathoracic lesion is accentuated and a plateau in expiratory flow occurs on the flow-volume loop. • During inspiration, intrapleural pressure is markedly negative; therefore, the obstruction is decreased. • The ratio of FEF50% to FIF50% is very low and may approach 0.3. • The FEV1 is considerably < the FIV1. • Although the flow ratios are similar to those seen in patients with COPD and chronic asthma, these disorders often can be distinguished by expiratory curve in patients with COPD and asthma is primarily altered in the effort-independent portion of the curve, leading to a characteristic shape unlike the plateau configuration of an upper airway obstruction.

22. Variable intrathoracic obstruction due to squamous cell carcinoma of the trachea.A. CT of the chest shows a tracheal lesion (arrow). B . Superimposed flow volume loops show a plateau of expiratory flow preceded by a peak of flow at higher lung volumes. The forced inspiratory flow is preserved in comparison to expiratory flow, but it is also reduced. FEF50%/FIF50% is 0.4.

23. Flow-volume loop typical of chronic obstructive lung disease. Very lowFEF50%/FIF50% and typical curvilinear shape are noted.

24. Spirometry • Routine spirometry, may be helpful. If the forced spirogram shows that the PEFR is reduced disproportionately to the reduction in FEV1, an upper airway obstruction should be suspected. • Other findings that suggest the diagnosis include a ratio of < 1.0 for the FIF25–75% and the FEF25–75%. • Whenever the MVV is reduced in association with a normal FEV1, a diagnosis of upper airway obstruction should be considered.

25. Upper and Lower Airway Obstruction • In contrast to the situation in patients with diffuse obstructive disease of the lower airways (e.g., COPD, asthma), the ventilation-perfusion mismatch does not occur in upper airway obstruction. • Hypercarbia is not seen unless the degree of obstruction is very severe, although nocturnal hypercarbia may occur while daytime levels of Pco2 are normal. • Hypoxemia is also not present except during exercise and with severe airflow limitation, when it may accompany increases in the level of PCO2. • In contrast to asthma and many instances of COPD, the airflow obstruction caused by an upper airway lesion does not resolve following the inhalation of a bronchodilator.

26. Radiographic Assessment • CT has afforded the most important approach to imaging of the extrathoracic airways . • The standard chest roentgenogram is often not helpful in detecting the presence, or the cause, of upper airway obstruction. • The trachea is usually well visualized on the postero-anterior and lateral views in chest roentgenograms of good quality. It is located in the midline and is moderately deviated at the level of the aortic arch • Many standard roentgenograms are under-penetrated so that the trachea may become a “blind spot.” • The use of digital imaging techniques may avoid such pitfalls. However, thoracic CT studies have become the procedure of choice for imaging the upper airway.-

27. Acute epiglottitis.Lateral soft-tissue radiograph ofthe neck of a patient with stridor shows swelling of the epiglottis (large arrow) and loss of normal convexity of the edematous aryepiglottic folds (small arrow).

28. A. CT scan of the chestdemonstrating marked narrowing of the trachea with intraluminalcalcified nodular projections in a patient with tracheopathiaosteoplastica. B . CT scan of the chestdemonstrating multiplanner reformation of the trachea in thesagittal plane of the same patient.

29. CT scan of the chest demonstratingmarked extraluminal compression of the trachea causedby intrathoracic goiter.

30. Radiographic Assessment • Helical CT scanning (HCT) minimizes artifacts due to respiratory motion and provides imaging of the whole thoracic volume during a single breath hold. Since the early 1990s, HCT has become the preferred noninvasive modality for evaluation of the central airways. • The use of HCT using multidetector technology and thin collimation provides high-resolution images of the entire thorax, improved special resolution, greater speed of image acquisition, and excellent contrast enhancement. • HCT techniques using multi-planar and three-dimensional reconstruction can provide virtual images of the thorax that enhance the perception of local and diffuse anatomic lesions of the upper airways.

31. HRCT of the chest with three-dimensional reconstruction of the upper airway showing focal tracheal compression (A, B ). .

33. Radiographic Assessment • The images may demonstrate the degree of tracheal widening or narrowing, show the location and longitudinal extent of abnormalities, assess tracheal wall thickness, and demonstrate associated extratracheal diseases. • The use of paired inspiratory-dynamic and expiratory multislice HCT has proved helpful for the diagnosis of tracheomalacia. • If complete collapse is not demonstrated during expiration, then one should confirm the diagnosis by quantitatively measuring the degree of airway luminal narrowing during expiration. • Tracheo-malacia is generally defined as a reduction in cross-sectional area of > 50 % on expiratory images.

34. Magnetic resonance imaging • Magnetic resonance imaging (MRI) is another modality that may be used to assess the central airways and surrounding mediastinal structures. • MRI provides a multi-plane image of the chest without the need for contrast material. • The technique is best used to investigate vascular structures surrounding central airways, such as vascular rings or aneurysms that may compress the trachea, rather than the airways themselves, which are better visualized using CT scanning.

37. CAUSES OF UPPER AIRWAY OBSTRUCTION Deep Cervical Space Infections • The cervical fascia is divided into a superficial and, a more complex, deep layer. This configuration and complexity divides the neck into functional units. • Infection can spread along the planes formed by the cervical fascia. • Infections affecting the deep neck tissues may result in life-threatening upper airway obstruction. • Patients with deep cervical space infections may present with sore throat, odynophagia, neck swelling, pain, fever, and dyspnea. • Stridor and profound respiratory difficulty are signs of significant upper airway obstruction. • Parapharyngeal, peritonsillar, submandibular, and retropharyngeal abscesses are common locations in adults.

38. Deep Cervical Space Infections • Mixed infections caused by aerobic and anaerobic infections are common and have been reported in up to two-thirds of cases. • An odontogenic origin is probably most common, with upper respiratory tract infections as an important etiology in children. • Intravenous drug abuse, mandibular fractures, iatrogenic and non-iatrogenic traumatic injury to the upper airway, underlying malignancy, and poor underlying immune status are associated conditions. • Ludwig’s anginaan infection of the submandibular space and the floor of the mouth is potentially lethal and is commonly associated with significant upper airway obstruction. • This entity is usually a cellulitic process and can affect the submandibular spaces bilaterally. • 75 percent of the cases with true Ludwig’s angina required tracheostomy.

39. Ludwig’s angina

40. Treatment of deep cervical infections • Treatment of deep cervical infections involves maintenance of oxygenation and ventilation by securing an adequate airway, administration of appropriate antibiotics, and when indicated, use of surgical drainage. • Complications of deep cervical infections include upper airway obstruction , Lemierre’s syndrome , distant infection, septic embolization, carotid artery rupture, pulmonary embolism, direct extension of infection resulting in mediastinitis and empyema, and rupture of the abscess during intubation or other interventions.

41. Lemierre’s syndrome • Lemierre’s syndrome, arises from a nasopharyngitis or peritonsillar abscess. • This lateral pharyngeal space infection results in suppurative thrombophlebitis of the internal jugular vein, septicemia, and metastatic abscess formation, particularly in the lungs and joints. • Fusobacterium necrophorumis usually the causative agent and has been cultured from blood in > 80 % of cases. • Symptoms begin with a sore throat, fever and painful swelling in the neck, followed by tender lymphadenopathy and tenderness along the sterno-cleidom-astoid muscle (representing thrombophlebitis of the internal jugular vein). • Dysphagia, trismus, and upper airway obstruction may occur as a result of swelling of the lateral pharyngeal space. • Contrast-enhanced CT scan of the neck is most useful in establishing the diagnosis of thrombosis of the internal jugular vein and may demonstrate soft-tissue abscesses, fasciitis, and myositis, which may require extensive surgical debridement. • Without the use of early and appropriate antibiotics, such as high-dose penicillin with metronidazole, or monotherapy with clindamycin, the mortality rate approaches 100 percent.

42. Epiglottitis • Epiglottitis is an infectious process that causes variable degrees of inflammation and edema of the epiglottis and supraglottic structures. • Supraglottitis may be more appropriate term in adults, since the supraglottic structures usually are involved with variable involvement of the epiglottis. • This condition can be life threatening. • Its prevalence is 0.18 to 9.7 cases per million adults; the mortality rate may be as high as 7.1percent. • Clinical presentation includes odynophagia, with inability to swallow secretions, sore throat, dyspnea, hoarseness, fever, tachycardia, and stridor. • In one review, 44 %of the patients had a normal routine oropharyngeal examination. • Fiberoptic laryngoscopy is necessary to make the diagnosis. • Radiographic studies can be helpful in ruling out other etiologies with similar presentations and in evaluating potential complications. • The airway must be secured, and radiographic studies should not delay diagnosis or management. • Supraglottitis may involve the base of the tongue, uvula, pharynx, and false vocal cords.

43. Epiglottitis • The disease may be increasing in prevalence among adults and declining in children, perhaps, reflecting introduction of haemophilus-b conjugate vaccines. • The disorder appears to be more prevalent in colder, winter months and in smokers. • Blood cultures are positive in less than one-third of cases. • Although Haemophilus influenzae is the most common organism isolated in children, adult supraglottitis may be caused by a variety of organisms, including Haemophilus influenzae, pneumococci, group A streptococci, Staphylococcus aureus, Streptococcus viridans, mycobacteria, fungi, and viruses. • Throat cultures can be helpful in diagnosis and management; however, treatment should not be delayed while awaiting culture results.

44. Epiglottitis • Illicit drug use may be associated with epiglottitis, with inhalation of heated objects (e.g., metal pieces from a crack cocaine pipe or the tip of a marijuana cigarette) causing thermal injury to supraglottic structures. • Signs, symptoms, and roentgenographic and laryngoscopic findings are similar to infectious epiglottitis. • Initial antibiotic therapy using a third-generation cephalosporin or extended-spectrum penicillin is reasonable. • Corticosteroids often are used in management of acute epiglottitis despite lack of evidence to support their use. • Based on anecdotal case reports, epinephrine is also used. • Patients should be observed closely and experienced staff should be available immediately to secure the airway by intubation or surgical approach, if needed.

45. Laryngotracheobronchitis • Laryngotracheobronchitis (croup), an acute viral respiratory illness commonly seen in children, is characterized by narrowing of the subglottic area, causing symptoms of stridor, barking cough, and hoarseness. • Adult croup is a rare condition. • Rare instances of diphtheric croup have been described in adults; noninfectious membranous tracheitis related to trauma also has been reported.

46. Bacterial tracheitis • Acute bacterial tracheitis refers to involvement of the subglottic trachea by bacterial infection and usually follows an episode of viral laryngotracheobronchitis. • Thick, purulent exudates and mucosal edema may cause symptoms of upper airway obstruction. • Staphylococcus aureusappears to be the predominant organism. • Prompt antibiotic therapy, close observation with attention to airway compromise, and frequent suctioning are important.

47. Rhinoscleroma • Rhinoscleroma is a chronic, progressive granulomatous infection of the upper airway that may cause airflow obstruction. • This disorder affects primarily the nose and paranasal sinuses, but also may involve the nasopharynx, larynx, trachea, and bronchi. • The causative organism is Klebsiella rhinoscleromatis. • About 5 percent of patients have diffuse narrowing of the trachea. • Prolonged antibiotic therapy with trimethoprim-sulfamethoxazole is effective.

48. Tuberculosis • The incidence of laryngeal tuberculosis may be on the rise due to the epidemic caused by the human immune deficiency virus. • This form of the infection is relatively uncommon, accounting for < 1 % of tuberculosis cases. • Laryngeal tuberculosis may present as progressive hoarseness and ulceration or a laryngeal mass. • PPD skin test and acid-fast bacilli in sputum may suggest the diagnosis. • Biopsy from the laryngeal abnormality usually is required. Biopsy features include granulomatous inflammation,caseating granulomas, and acid-fast bacilli. • The true vocal cords and epiglottis are the areas most likely affected. • Treatment with antituberculous medications is usually adequate and should be instituted promptly, since the disease is highly contagious. • Surgical interventions, including tracheostomy , are reserved for airway obstruction and long-term complications and, in one report, were required in 12 %of the cases.

49. Endobronchial tuberculosis • Endobronchial tuberculosis may result in significant airflow limitation that is related to the initial lesion or subsequent stricture formation. • A barking cough and sputum production are common findings. • Early diagnosis and treatment with antituberculous medications should decrease the development of fibrostenosis and resultant airflow limitation. • The role of steroids in reducing the incidence of fibrostenotic complications remains unclear and controversial. • Management may require endoscopic or surgical approaches.

50. Head and Neck Cancer • Head and neck cancers, which represent the fifth most common cancer worldwide, develop in the oral cavity, pharynx, larynx . • The great majority are squamous cell carcinomas. • Symptoms include hoarseness , hemoptysis, sore throat, and otalgia; life-threatening upper airway obstruction may be seen. • Five percent of newly undiagnosed laryngeal cancers present with severe dyspnea or stridor and may require emergency laryngectomy or tracheostomy.