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Chapter 33:  Assessment of Pulmonary Function in Normal and Pathological States

 

Pulmonary Function Tests:  Spirometry

1Spirogram (Volume vs Time)

 

1Above data represented as Flow-Volume Loop
2Flow: Volume Loops (c) John Rhoades 

2http://asthma.about.com/library/weekly/aa090897.htm

 

  • The above flow volume loop is consistent with airway obstruction, as indicated by the concave shape of the upper right portion of the graph. The red line would be the predictive value taking into account parameters such as patient height, weight, age, and ethnicity. Noteworthy points along the graph have been numbered and are defined as follows.

    1. Peak expiratory flow rate (PEFR). The value of PEFR is that it allows assessment of expiratory muscle strength, large airway patency (trachea, main bronchi) as well as overall test validity. An asthmatic patient may have normal or decreased PEFR values.

    2. Forced Expiratory Flow at 25% (FEF25%) occurs when 25% of the total volume (FVC) has been exhaled. If maximal patient effort in exhalation is being maintained, then this flow rate would be reflected of flow through medium-size to large bronchi. This value in concert with the FEF 75% gives the range FEF25%-75%, which overall represents the middle half of FVC. This range appears less dependent on patient effort and is perhaps more reflective of the presence or absence of small airway obstruction. The FEF25%-75%is sensitive to the total volume exhaled (FVC) and appears to exhibit significant variability. Generally, patients with asthma may have decreased FEF25% with the extent of the decreased dependent on the magnitude of the inflammatory response and extent of bronchoconstriction. The effect on FEF25% may be noticeable and variable expiratory flow rates in may be observed in the absence of overt patient symptoms.

    3. FEF50% is being expiratory flow rate at the 50%.relative to the total volume (FVC) which will be exhaled. As suggested earlier, FEF50% may be indicative of medium-small airway caliber and may be used as an alternative to FEF25%-75%.

    4.FEF75% is the flow rate at the 75% relative to the total volume to be exhaled (FVC). This point reflects small airway status and is used in the FEF25%-75% calculation. Decreased values in FEF75% would be expected in the asthmatic patient, even if symptoms are not apparent. This result is expected because most chronic pulmonary diseases are manifest initially in the smallest airways, which contribute significantly towards the end of the expiratory part of the flow volume loop.

    5. Forced Inspiratory Flow at 25% of FVC (FIF25%). This point is defined as the flow rate at the 25 percent point relative to the total volume which will be inhaled. This flow rate will not be particularly important in understanding for assessing the asthmatic state. However, it is an important value for anesthesiology because it indicates upper airway obstruction. Reduced inspiratory flow rates may be due to obstructions in the mouth, upper & lower pharynx, larynx, and vocal cords.

    6.Peak Inspiratory Flow Rate (PIFR) is defined by the fastest flow rate noted during the inspiratory cycle.

    7.Forced Inspiratory Flow at 50% of FVC (FIF50%) represents the flow rate at the 50% point relative to the total volume to be inhaled.

    8. Forced Inspiratory Flow at 75% of FVC (FIF 75%) represents the flow rate at the 75% point relative to the total volume to be inhaled.

    9 Forced Expiratory Volume at the 0.5 seconds (FEV 0.5). This value defines the amount of air exhaled (assuming maximal effort) in 0.5 seconds.

    10. Forced Expiratory Volume after 1 seconds (FEV1). At maximal effort, FEV 1 defines the air volume exhaled within the first second. Following administration of bronchodilator agent, FEV 1 values tend to improve in the asthmatic patient.

 

12Spirometry in More Depth
  • 12Spirometry: Definition--Spirometry measures the mechanical function of the lung, chest wall, and respiratory muscles. The method of analysis is based on an assessment of the total volume of air exhaled from a full lung, i.e. total lung capacity (TLC) to an empty lung (residual volume). For reliable assessment, this volume which represents the forced vital capacity (FVC) should be reproducible to within about 0.2 L. The process involves the patient inhaling as much as possible followed by rapid and forceful exhalation for as long as possible. The spirometry has been assigned a CPT code (94010) with a special code to cover cases in which spirometry is performed both before and after the use of bronchodilator (94060).

  • 12To a first approximation a reduction in any amount is air exhaled forcefully within the first seconds of FEV, a.k.a. FEV1 may indicate an elemental reduction in the maximum inflation capacity of the lung (TLC). The most common cause of FEV1 reduction is airway obstruction and the use of inhalational bronchodilators determines the reversibility of airway obstruction. As noted earlier, determination this reversibility is important in development of a preanesthetic plan for patients with obstructive disease because the prophylactic use of bronchodilators may obviate interoperative pulmonary adverse events.

  • 12The indication for use of spirometry includes many different endpoints in addition to preanesthetic assessment. 

    • Evaluation of dyspnea, determination of the presence of pulmonary disease as well as assessing the efficacy of drugs that might treat such disease, quantifying the extent of ventilatory impairment as well as monitoring for the presence or evolution of occupationally-related lung disease in addition to evaluation of operative risk all represent reasons to perform spirometric testing.

  • 12In some patients there many relative contraindications for spirometry. 

    • Some examples include:

      1. unstable angina

      2. recent myocardial infarction

      3. abdominal or thoracic aneurysm

      4. cerebral aneurysms

      5. recent eye surgery in which increased intraocular pressure which occurs during forced expiration would be problematic

      6. patients with relatively recent abdominal or thoracic surgery 

      7. patients with a history of syncope associated with forced exhalation.

  • 12Particularly for the perioperative or preoperative assessment, the efficacy of bronchodilators ( use of bronchodialator attenuate the likelihood of interoperative bronchoconstriction)  is often determined. 

    • To establish a baseline in those patients who routinely take bronchodilators, the medication may be withheld with the recognition that withholding medication may in fact itself worsened bronchospasm. 

    • Nevertheless in order to establish baseline lung function and determine the maximal theoretical effect of bronchodilator medication might be withheld.

  • 12The extent to which interoperative planning will be based on spirometry is interdependent on the validity of the spirometric test. Accordingly the quality of the tests are important and unreliable test results must be considered accordingly. Guidelines from the American Thoracic Society defines an acceptable spirometric test in the following manner:

    •  (1) minimal hesitation associated with the start of the forced expiratory component, specifically extrapolated volume (EV) should be < 5% of the FVC or 0.15L, whichever is larger

    • (2) cough does not occur during the first seconds of forced exhalation

    • (3) at least 1 of 3 criteria which define a valid end-of-test has been met:

      • (a) smooth curvilinear rise of the line-time tracing to a plateau that lasts at least one second

      • (b) is a test fails to show a expiratory plateau but a forced expiratory time (FET) of 15 seconds obtains or 

      • (c) the patient should not to or could not continue forced exhalation for medical reasons.

  • 12As suggested above, the two largest values for FVC and the two largest values for FEV1 should vary by no more than 0.2L. 

    • Analysis of spirometric test problems indicate that start-of-test difficulties which effect FEV 1assessment tend to be rare, maybe about 2%, but end-of-test difficulties which ultimately affect FVC quality are much more common, about 60%-80%. 

    • The quality of FVC is insured therefore if there is a 12 to 15 second expiratory time even if the expiratory plateau is not evident. 

    • Checking the beginning of the volume-time tracing for possible "hesitant" start is important since such hesitation can give an incorrect, underestimation of FEV1

    • 12The most important 3 values for assessment of abnormal pulmonary function would be: (1) FVC, (2)  FEV1, and (3)  FEV 1/FVC.

Flow-Volume Characteristics of Acceptable and Unacceptable Spirometry

 

  1. "Instantaneous start of exhalation

  2. Rapid rise in flow to peak flow

  3. Shap peak occuring early in exhalation

  4. Smooth continuous fall in flow without interruption

  5. Gradual fall in low flow to RV

  6. Smooth continuous inhalation to TLC

  7. Reproducible shape

  1. Slow start
  2. Slow rise in flow
  3. Broad, late peak
  4. Erratic Flow (cough)
  5. Abrupt return to 0 flow
  6. Incomplete inhalation
  7. Non-reproducible"

  • 12Variable intrathoracic obstruction

    • Possible causes:

      • 13Tracheomalacia

        • "A congenital weakness and floppiness of the walls of the trachea (main airway).

        • Tracheomalacia occurs when the cartilage in the trachea fails to develop or mature in a timely manner, resulting in the wall of the trachea being floppy rather than relatively rigid. Children with tracheomalacia have noisy breathing (high-pitched sounds when breathing, called stridor, and rattling noisy breaths) that becomes even worse if they develop upper respiratory infections."

      • 14Polychondritis

        • "Relapsing polychondritis is a disease characterized by autoimmune-like episodic or progressive inflammation of cartilage and other connective tissue, such as the nose, ears, throat, joints, kidneys, and heart.

        • As relapsing polychondritis advances, it causes more dangerous symptoms such as deterioration of the cartilage that holds the windpipe open. Progressive disease can destroy the integrity of the airway and compromise breathing. Destruction of the rib cartilage can collapse the chest, again hindering breathing. Joints everywhere are involved in episodes of arthritis, with pain and swelling. Other tissues besides cartilage are also involved, leading to a variety of problems with the skin and other tissues. Occasionally, the aorta or heart valves are damaged."

      • Tumors of the lower trachea or main bronchus

  • 12Variable extrathoracic obstruction

    • Possible causes:

      • unilateral/bilateral vocal cord paralysis

      • vocal cord constriction

      • airway burns

      • reduced pharyngeal cross-sectional area

15Relapsing polychondritis: A Case Study
  • Introduction:
    • Relapsing polychondritis (RP) involves recurrent cartilaginous and connective tissue inflammation. This disorder is rare in the underlying mechanism unknown. Some patients with RP exhibit inspiratory abnormalities and high mortality morbidity accompany this involvement. More commonly, RP manifests as auricular chondritis, nasal chondritis and polyarthritis. Female patients are more likely to exhibit airway complication secondary to RP. Patients with relapsing polychondritis may have operations fairly frequently for nasal reconstruction, bronchoscopy, valvular surgery, tracheobronchial stenting and tracheostomy. The case report which follows provides a context for discussion of anesthetic management in patients with RP.
  • This patient was a female Asian of middle-age with extensive tracheobronchial involvement who underwent tracheostomy subsequent to tracheal collapse. The procedure was performed under general anesthesia.

  • The patient was a 48-year-old Asian woman who presented with dyspnea and exhibited productive cough for the previous eight months. The initial diagnosis was bronchial asthma. Helix inflammation of both ear pinnae and polyarthralgia with small and large joint involvement were also noted in the history and physical. Initially, bronchoscopic and chest x-ray evaluations were performed and found normal. The pulmonary function test predicted value (FVC) was 2.46 L. in the actual test result was 2.41 L.. The FEV 1 was 1.63 L. (Predicted value was 2.1 L.). The peak expiratory flow rate was 4.88 L. relative to a predicted value of 5.62 L.. These analyses suggested mild flow obstruction that was unresponsive to bronchodilator treatment. Nasal root elevation and stridor (progressive) had been noticed by family.

 

  • Upon admission, physical examination revealed voice hoarseness, saddle nose deformity and bilateral ear perichondritis. Inspiratory and expiratory stridor (resting) was observed. Laboratory findings were generally normal as were and electrocardiographic and neck & chest x-rays. Epiglottis inflammation and glottis inflammation as well as limited cord movement was revealed by bronchoscopy. At this point, during bronchoscopy, the patient became cyanotic with severe stridor in the decision was made to secure airway by tracheostomy under general anesthesia.
  • Preoperative assessment:
    • Blood pressure was 154/92 mm Hg, heart rate = 102 bpm, respiratory rate = 16/min, pO2 = 97% on room air. Preanesthetic medication included 0.6 mg atropine with 8% Xylocaine. 
    • Awake orotrachial intubation was implemented using direct laryngoscopy. 
    • As a result of a swollen epiglottis with a significantly narrowed glottic opening because of erythema and edema, only a 6 mm (internal diameter) cuffed can be used. 
    • Following endotracheal intubation, 5 mg/kg thiopental, 100 micrograms fentanyl and 0.4 mg/kg atracurium was administered by IV. Ventilation was controlled to allow a tidal volume of 500 ml with a respiratory rate of 10/min.. The peak inspiratory pressure was 28 cm H20. 
    • A 6.5 mm tracheostomy tube was placed in the patient sent to the recovery room. Initially, the vital signs exhibited stability (blood pressure = 130/90 mm Hg; heartrate = 100/min.; respiratory rate = 15/min.,pO2 =99% with T-piece circuit at FiO2 of 50%). 
    • Following tracheal suctioning, the patient reported respiratory difficulty.
      • O2 saturation remained acceptable; however, blood pressure increased to 160/100 mm Hg with an attendant increased heartrate to 120/min. and an increase in respiratory rate to 25/min.. 
      • Bronchoscopy indicated diffuse inflammation and swelling of the entire trachea with extension to the right main bronchus. 
      • Furthermore, collapse of the trachea and bronchi were visualized during inspiration and expiration. Suction applied through the bronchoscope also induced tracheal collapse. 
      • Application of continuous positive airway pressure (CPAP) at 8 cm H20 was implemented to prevent airway collapse. CPAP application reduced patient breathlessness. Further treatment was implemented in the ICU. High dose corticosteroid and nonsteroidal anti-inflammatory drugs were given to suppress the inflammatory component (tracheobronchial tree). Antibiotics were prescribed following identification Streptococcus viridans in the respiratory tract. The recommendation was the placement endobronchial stents; however, this procedure was delayed due to the presence of to respiratory tract infection.
  • Discussion: 
    • Relapsing polychondritis (RP) is a rare disease but offers certain specific challenges to anesthesia practice because of the disease process alters the structural characteristics of cartilage which in turn present intubation challenges and challenges associated with maintenance of the patent airway. 
    • Although RP appears to be an inflammatory, autoimmune disease, laboratory tests to confirm the presence of RP are unavailable. 
    • The inflammatory component is managed with corticosteroid treatment which at least for severe cases does not stop the progressive process. Relapsing polychondritis, although not noted in the case study, may also present cardiovascular challenges since cardiac involvement may include aortic and mitral valve regurgitation, pericarditis, paroxysmal atrial tachycardia, aneurysms, myocarditis, and systemic vasculitis. 
    • Ventilatory impairment, as a manifestation of RP, occurs in about 50% of RP patients, mainly female patients, and respiratory difficulties in the setting has a high associated morbidity and mortality.
  • Airway involvement can be diffuse or more localized and the involvement, especially relevant for intubation and airway maintenance, may be extrathoracic or intrathoracic (bronchi and trachea). 
  • The airway involvement is indicated by tenderness over the anterior trachea and thyroid cartilage, sore throat, and nonproductive cough. 
  • More severe disease include additional manifestation such as voice hoarseness, dyspnea, and stridor. 
  • Airway obstruction in RP results from:
    1. airway narrowing (acute stage) resulting from inflammatory reactions, i.e. swelling 
    2. subsequent development of scar tissue and 
    3. "dynamic airway collapse" because those cartilage destruction at laryngeal, tracheal and bronchial sites. And regions exhibiting scarring and inflammation, abnormal mucociliary function predisposes to infection.
  • Airway assessment would include CT scans [head & neck] as well as radiography. Airway caliber changes may be identified and these changes are permanent, secondary to scarring. 
    • However, airway caliber dynamic changes which occur during breathing would not be revealed by radiographic techniques. 
    • Bronchoscopy allows direct evaluation of these dynamic changes and specifies locations and characteristics of structural abnormalities. 
    • Unexpected airway collapse intraoperatively can have catastrophic consequences such as death.
  • Anesthetic management: as noted earlier, these patients may undergo "routine" surgeries in support of tracheostomy, nasal reconstruction, bronchoscopy, valvular surgery, or tracheobronchial stenting. 
    • Due to loss of cartilaginous structural support, airway management becomes the central, crucial  issue.
      •  Accordingly, preoperative assessment concerning the extent of structural weakness is important to anesthetic plan development. 
      • Cartilaginous destruction can make intubation challenging because of a small glottis. Smaller endotracheal tube sizes may be a benefit. 
      • Tracheal intubation itself may be associated with sudden death secondary to tracheal collapse; however, this eventuality might be prevented by continues positive pressure mask ventilation. 
      • In the case above, awake laryngoscopic intubation was used, technique allowing reasonable visualization during intubation. Following endotracheal intubation, positive pressure ventilation prevents airway collapse.
        • Fiber-optic bronchoscopy in support of intubation may be an alternative. 
        • Also, general anesthesia might be avoided and instead use local or regional approaches. 
        • Preoperative management might include corticosteroid use to decrease inflammation.
      • Intraoperative bronchoscopy may be useful to more completely assessed tracheobronchial involvement. The trachea might also be treated with local anesthetic through tracheostomy; such agents may reduce tracheobronchial irritability during emergence. 
      • For patients with primarily (only) epiglottic or subglottic disease, tracheostomy would be indicated. Here the point is that for more generalized disease tracheostomy alone would not be expected to be effective since tracheal collapse below the tracheostomy point could be anticipated. 
      • Avoidance of airway collapse in these cases then require positive pressure ventilation. With diffuse tracheobronchial relapsing polychondritis, continues positive airway pressure (CPAP) may be an effective intervention. 
      • In patients with tracheomalacia, CPAP provides a "splint" which presents airway collapse. 
      • Effective airway stenting might require a CPAP of about 10 cm H2O. CPAP opposes elevated pleural pressures, maintaining therefore airway integrity.
  • Tracheobronchial tree mechanical stenting offers treatment alternatives (silicone stents, self-expanding stainless steel stents). Stent placement, which probably should be done early in the RP disease process, is performed under general anesthesia.
  • 12Obstructive defects:
    • FEV 1 reduction disproportionate compared to the FVC is a key to diagnosing obstructive lung dysfunction. 
      • This characteristic would be associated with a number of lung diseases including:
        • asthma
        • acute/chronic bronchitis
        • bronchiectasis
        • emphysema
        • cystic fibrosis
        • pneumonia
        • emphysema
        • -1-antitrypsin deficiency
        • bronchiolitis. 
      • For any given expiratory volume, expiratory flow be reduced. The reduction in airflow in the situation can be secondary to a number of factors including airway inflammation, increased intraluminal secretions, bronchial spasm, and/or decreased airway parenchymal support due to reduced lung elastic recoil.
    • Assessment of reversibility is important in terms of developing an anesthetic planning; therefore, spirometry-determined airway obstruction raises the question of whether or not inhaled bronchodilators might be useful
      • The American Thoracic Society has developed a minimal response that would be demonstrated in order to affirmatively decide that bronchodilator treatment is useful. 
      • This minimum response corresponds to at least a 12% and 0.2 L increase in either the FVC or FEV1 as documented by spirometry performed between 15-20 minutes following inhalation of a normal therapeutic bronchodilator dosage. In this protocol is reasonable in predicting the likelihood of bronchodilator-mediated clinical benefits; however, negative result does not mean that no clinically beneficial response might be obtained. Positive responses to bronchodilators appears to be well correlated with positive responses to steroid treatment.
  • 12Restrictive defects
    • Restrictive lung disease is characterized by a reduction in FVC with a normal or elevated FEV1/FVC ratio.
  • 12Spirometric quantification:
    • FVC, FEV1, and FEV1/FVC ratios will usually be above the lower limits of normal; however, the question is how are these lower limits of normal estimated. The general approach is to define the lower limit of normal as a result that a mean predicted value -1.64 times the standard error of the estimate from the population study on which the reference is based. The reference would take into account patient gender, age and height. Should the lower limit of normal value be unavailable than the FVC and FEV1 should be greater than or equal to 80% of predicted and the FEV1/FVC ratio should be no more than about 8-9% below the predicted ratio. Of these two approaches, the American Thoracic Society, has recommended the use of the lower limit of normal measure rather than the 80% of predicted for setting the line below which abnormality would be concluded from the test results.
    • Reduced FVC on spirometry without a reduced FEV1/FVC ratio indicates restrictive ventilatory dysfunction. Shortened exhalation during spirometry can result in a reduced FVC. Shortened exhalation can be due to a number of factors including cardiomegaly, ascites, pregnancy, obesity, pleural effusion, kyphoscoliosis, pulmonary fibrosis, pleural tumors, neuromuscular disease, diaphragmatic weakness or paralysis, space-occupying (mass) lesions, congestive heart failure, lung resection, inadequate expiration due to pain, severe obstructive lung disease, and inadequate inspiration.
    • Reductions in FVC and/or FEV1 Classification.
      • "Mild: 70%-79% of predicted
      • Moderate: 55%-69% of predicted
      • Severe: 45%-54% of predicted
      • Very Severe: < 45% of predicted"
  • 12Obese Patients:
    • Special assessments include: sitting vs. supine vital capacity measurements. 
      • Diaphragmatic strength assessments can be made by vital capacity measurements in patients who are either sitting or in the supine position. First measurements are made in the upright (sitting position) and then measurements made in the supine position 
      • Diaphragm weakness (or paralysis) would be reflected by reduction in the vital capacity of less than 90% of the upright vital capacity. 
      • Increased vital capacity reduction in the supine position may not mean diaphragmatic dysfunction if the patient is obese. In that case, resistance to obesity to diaphragm descent may explain the reduction.
  • 12Interoperative and postoperative risk assessment
    • FEV 1 is an important measurement for operative risk assessment associated with pulmonary impairment. The general rule is that when FEV 1  is greater than 2L or greater than about 50% of normal (predicted), significant complications are unlikely. 
      • However, the surgical site is an important consideration in risk assessment. For example, chest surgery has the highest risk. Furthermore, the patient-related considerations can translate to higher operative risk due to pulmonary complications.
    • Increased operative risk for pulmonary related complications is associated also with pre-existing patient conditions. Some of these conditions include: cardiovascular disease, pulmonary hypertension, exertional dyspnea, pre-existing pulmonary dysfunction, a history of heavy smoking, respiratory infection, cough, advanced age (> 70 years), poor nutrition, obesity, general debilitation, as well as the expectation of a prolonged surgical procedure.
    • Lung surgery: assessment for this type of surgery requires an estimation of postoperative FEV1 based on preoperative FEV 1. Scintigraphy (perfusion scans) may be helpful in certain ambiguous cases to more quantitatively ascertain contributions from remaining pulmonary parenchyma. Relative perfusion percentage (Q) of remaining parenchyma is thought proportional to its ventilation contribution and may be helpful in estimating postoperative pulmonary function using the following relationship:
      • postoperative FEV 1 = preoperative FEV 1 x Q% of remaining lung parenchyma. An example calculations also presented in reference 12 as follows:
        • in this example the preoperative FEV 1 is 1.6 L and lung to be resected indicates 40% perfusion. Therefore postoperative FEV 1 would be estimated by 1.6 x 0.6 or 0.96 L (i.e. 1 L). Chronic respiratory failure could be associated with an estimated postoperative FEV 1 < 0.8 L. so the 0.8 L might be used as a cut-off for acceptable operative risk. For patients with preoperative FEV 1 < 2 L or 50% of predicted, arterial blood gas values and cardiopulmonary exercise evaluation may be helpful in further assessing operative risk. The equation above for assessing operative risk in lung resection procedures has been itself validated in clinical trial (17)
          • In that study patients were considered relatively safe for pneumonectomy if they exhibited a negative history for cardiovascular problems and a normal ECG and also demonstrated in FEV 1 and a pulmonary diffusing capacity for carbon monoxide (DLCO) > 80% predicted. If FEV 1 or CLVO was found less than 80% of predicted, patients would be subjected to cardiopulmonary exercise testing as part of a more complete preoperative assessment.

Flow Volume Loop Summary

Figure from: Chapter 13 in: Textbook in Medical Physiology And Pathophysiology  Essentials and clinical problems Copenhagen Medical Publishers  1999 - 2000, Poul-Erik Paulev, M.D., D.Sci  (http://www.mfi.ku.dk/ppaulev/chapter13/Chapter13.htm), used with author's permission

3Interstitial Fibrosis
  • 3"The interstitial lung diseases are a group of heterogeneous disorders characterized by diffuse and usually chronic involvement of the connective tissue of pulmonary interstitium. These disorders are grouped together because of common clinical, radiological and patho-physiological changes, but in establishing a diagnosis you must consider dozens of different disorders. These can be classified according to etiology."--University of Western Ontario, Department of Pathology; maintained by C.J. Gibson--http://www.uwo.ca/pathol/MedsII/NonNeolung/lung3.htm#Objectives


Interstitial Fibosis (Lung): left--low power; right--higher power:University of Western Ontario, Department of Pathology

  • 3Several history and physical considerations and diagnostic test results support a diagnosis of idiopathic interstitial fibrosis

    • Clinical data

      • Male, age 50. (Onset of disease in the 4th or 5th decade with a ratio of 2:1 occurrence in males versus females)

      • progressive dyspnea, non-productive cough

      • no history of a predisposing condition

      • clubbing of fingernails, auscultatory crackles

    • "Radiologic data

      • bilateral reticulonodular infiltrates with basal prominence"

    • "A chest x-ray showed bilateral reticulonodular pulmonary infiltrates more prominent in the bases.
      There was no obvious lymphadenopathy."

  • 3"At autopsy the lungs had the gross appearance of "honeycomb lung" - the gross manifestation of interstitial fibrosis."

  • 3"An additional microscopic finding was thickening of the walls of muscular arteries which occurs secondary to pulmonary hypertension which is in turn a sequela of interstitial fibrosis."

5Pulmonary Alveolar Proteinosis
  • 5Pulmonary alveolar proteinosis is a rare disease of unknown etiology characterized pathologically by accumulation of  periodic acid-Schiff (PAS)-positive material consisting mostly of phospholipids and protein within the alveolar spaces.

  • 5Pulmonary alveolar proteinosis  occurs mainly in previously healthy men and women within the 20 to 60 yr old age range.

    • Pathologic findings are limited to the lungs.

    • The pathologic process may be diffuse or local, affecting typically the basal and posterior lung segments although occationally affecting only anterior segments.

  • 5Physical findings are limited to the lungs but may be absent despite diffuse parenchymal involvement noted on chest x-ray. "Fine inspiratory crackles are usually heard over the affected lung areas."

  • 5Chest x-ray often reveals a butterfly pattern of opacities similar to that seen in pulmonary edema. "High-resolution CT scanning shows ground-glass opacification and thickened intralobular structures and interlobular septa in typical polygonal shapes, referred to as crazy-paving."

  • 5"Vital capacity, residual volume, functional residual capacity, total lung capacity, and carbon monoxide single-breath diffusing capacity are usually slightly reduced."

  • 5"Hypoxemia may be present at rest or, if disease is mild, only with mild to moderate exercise. The PaO2 while breathing 100% O2 is usually low, indicating an intrapulmonary right-to-left shunt."

6Chest X-Ray: Pulmonary Alveolar Proteinosis (Jeffrey R. Galvin, M.D.; Michael P. D'Alessandro, M.D.; Yasayuki Kurihara, M.D.

 

Chest X-Ray: Pulmonary Alveolar Proteinosis 

 

7PAS-stain Pulmonary Alveolar Proteinosis 

"Granular, pink, PAS+ alveolar exudate fills alveoli. Denser pink clumps, acicular clefts, and a few disintegrating macrophages are present in the exudate. Electron microscopy shows myelin figures. Lavage fluid appears milky. Alveolar walls are only slightly thickened."

 

8Bronchiolitis Obliterans
  • 8Causes for Bronchiolitis Obliterans include infections (such as mycoplasma, Legionella, or viral),  toxic fume exposure usually nitrogen dioxide, collagen vascular disease (rheumatoid arthritis, system lupus erythematosis), bone marrow & heart-lung transplanation and drug reaction (penicillamine). An idiopathic manifestation ha also been reported.  Bronchiolitis Obliterans is formally defined as "concentrically scarred or stenotic small airways in the lung periphery.

  • 8Imaging.
    "The chest radiograph is often normal but may demonstrate mild hyperinflation and peripheral attenuation of vascular markings.  

    • Computed tomography usually shows a mosaic pattern of low attenuation areas representing either air trapping or hypoxic vasoconstriction in secondary pulmonary lobes from obstruction of small airways. Centrilobular nodular opacities can be seen in some cases as a result of the peribronchiolar distribution of granulation tissue." 

     

8Bronchiolitis Obliterans X-ray imaging (Jeffrey R. Galvin, M.D.; Michael P. D'Alessandro, M.D.; Yasayuki Kurihara, M.D.

 

Bronchiolitis Obliteran--CT imaging (Jeffrey R. Galvin, M.D.; Michael P. D'Alessandro, M.D.; Yasayuki Kurihara, M.D.

 

 

  • 1Extrinsic RVD occurs when alveolar volume is reduced due to compression by mass effect (such as tumor, blood, effusion) or if there is a reduction in thoracic compliance which causes a reduced number of ventilated alveoli. 

    • Examples of such causes include scoliosis, neuromuscular diseases, obesity, and scoliosis. 

    • Obstructive manifestation of sarcoidosis presents later in the disease process. 

    • A restrictive ventilatory disease which is sometimes reversible is adult respiratory distress syndrome (ARDS), which is associated with a 50% mortality rate. ARDS may frequently present in the perioperative time-frame in the patient subgroup that exhibits a history of sepsis, severe trauma, pancreatitis, or multiple organ system failure.

  • 1The importance of restrictive ventilatory defects is reflected in two elements -- (1) the diagnostic and management challenge and (2) their importance as representative of reversible restrictive alterations following anesthesia and surgery, particularly intrathoracic and upper abdominal surgery. 

    • RVD may be induced by pain, residual neuromuscular blockade, abdominal wound dressings, thoracic wound dressings, and diaphragmatic as well as chest wall neuromuscular dysfunction. 

    • These factors may be individually addressed preoperatively were perioperatively to reduce the likelihood of RVD-induced postoperative complications. For RVD and OVD, the process of anesthesia and surgery may induce mechanical ventilatory restrictions that are inflected on pre-existing, usually restrictive, ventilation abnormalities.

8Emphysema

  • 8Alveolar space dilation and destruction of the alveolar walls is characteristic of emphysema. These changes results in significant reduction of lung elastic recoil of the lung.

  • 8Physiological Changes with Emphysema: Compliance

    • Compliance is significantly above normal causing increased lung distention with reduced emptying.  This Chronic lung overinflation results (high total lung capacity, functional residual capacity, and residual volume), resulting in reduced diaphragmatic curvature which makes the diaphragm less efficient in generating small pleural pressure changes required for breathing. 

    • Pulmonary function tests on a patient with emphysema will reveal reduced expiratory flow (due to their low lung recoil), including a low FEV1, FVC, and FEV1/FVC ratio.(see below):

 

9Bronchitis
 
9Comparison of airways in bronchitis (left) and normal (right)
  • 9Bronchitis is a chronic condition associated with chronic cough with mucus production

    • .Mucus secretions and associated bronchial inflammation causeairway narrowing which increases flow resistance.  Obstructive pulmonary symptoms result. 

    • Pulmonary function: A decreased FEV1 and FEV1/FVC are characteristic of bronchitis. By contrast to asthma and emphysema, bronchitis is seldom associated with high residual volume. Bronchitis-medicated reduction in airway caliber, while reducing flow rates, is not further associated with airway collapse which would trap air in the lung.

 

Asthma

  • Airway hyperresponsiveness that is associated with increased bronchiolar smooth muscle tone and chronic inflammation are hallmarks of asthma.  Bronchospasm further constricts an already attenuated airway caliber and defines the acute asthma attack.  Bronchospasm also tends to cause airway closure which traps air and promotes lung hyperinflation.  In acute asthma, the patient will exhibit high lung volumes with increased FRC and will inspire an air volume that approximates total lung capacity. 

  • Pulmonary function tests during acute asthma exhibit obstructive flow properties, including a reduction in rate of maximal expiratory flow (a reduction in FEV1 and the FEV1/FVC ratio) secondary to increased resistance, and a decrease in FVC which correlates with the extent of lung hyperinflation.

  • "Because these patients breathe at such high lung volumes (near the top of the pressure-volume curve, where lung compliance greatly decreases), they must exert significant effort to create an extremely negative pleural pressure, and consequently fatigue easily. Overinflation also reduces the curvature of the diaphragm, making it less efficient in generating further negative pleural pressure."

 

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