Atelectasis

Definition

Atelectasis is Defined as the Collapse of Aerated Lung

  • Etymology: Greek roots ateles and ektasis = incomplete expansion

Epidemiology

Atelectasis in the Intensive Care Unit (ICU) Setting

Incidence

  • Acute Lobar Atelectasis is One of the Commonly Encountered Clinical Problems in Critical Care Medicine (Chest, 2019) [MEDLINE]

Atelectasis (and Pulmonary Complications) in the Postoperative Setting

Lobar Atelectasis (to At Least Some Extent) May Complicate Many Major Surgeries (Eur J Radiol, 1996) [MEDLINE] (Current Opinion Anaesthesiology, 2007) [MEDLINE]

  • Lobar Atelectasis Occurs in 90% of Cardiac Surgeries
  • Lobar Atelectasis Occurs in 75% of Spinal Surgeries
  • Lobar Atelectasis Occurs in 25% of Upper Abdominal Surgeries

Postoperative Pulmonary Complications are a Major Etiology of Perioperative Morbidity and Mortality (Br J Anaesth, 2017) [MEDLINE]

General Risk Factors for Postoperative Pulmonary Complications (Am J Respir Crit Care Med, 2005) [MEDLINE] (Ann Intern Med, 2006) [MEDLINE] (J Clin Anesth, 2013) [MEDLINE]

  • Definite Risk Factors
    • Age >65 y/o
    • Chronic Obstructive Pulmonary Disease (COPD)
    • Cigarette Use within the Prior 8 wks
      • Active Tobacco Use Increases the Risk of Perioperative Pulmonary Complications (Although the Incremental Risk is Small in the Absence of Chronic Lung Disease)
    • Emergency Surgery
    • Functional Dependence
    • Heart Failure
    • Intraoperative Long-Acting Neuromuscular Blockade
    • Poor General Health Status (ASA Class >2)
    • Serum Albumin <3 g/dL
    • Surgery Lasting >3 hrs
    • Upper Abdominal/Thoracic (Open)/Aortic/Head and Neck/Neurosurgical/Abdominal Aortic Aneurysm Surgery
  • Probable Risk Factors
    • Abnormal Chest X-Ray
    • Arterial pCO2 >45 mm Hg
    • Current Upper Respiratory Tract Infection
    • General Anesthesia (as Compared to Spinal/Epidural Anesthesia or Other Regional Anesthesia)
    • Postoperative Nasogastric Tube Placement

ARISCAT Risk Index for Postoperative Pulmonary Complications (Anesthesiology, 2010) [MEDLINE]

  • Age
    • ≤50 y/o: adjusted odds ratio = 1
    • 51-80 y/o: adjusted odds ratio = 1.4 (0.6-3.3), risk score = 3
    • >80 y/o: adjusted odds ratio = 5.1 (1.9-13.3), risk score = 16
  • Duration of Surgery
    • ≤2 hrs: adjusted odds ratio = 1
    • 2-3 hrs: adjusted odds ratio = 4.9 (2.4-10.1), risk score = 16
    • >3 hrs: adjusted odds ratio = 9.7 (2.4-19.9), risk score = 23
  • Emergency Surgery: adjusted odds ratio = 2.2 (1.0-4.5), risk score = 8
  • Preoperative Anemia (Hemoglobin ≤10 g/dL): adjusted odds ratio = 3 (1.4-6.5), risk score = 11
  • Preoperative Oxygen Saturation
    • ≥96%: adjusted odds ratio = 1
    • 91-95%: adjusted odds ratio = 2.2 (1.2-4.2), risk score = 8
    • ≤90%: adjusted odds ratio = 10.7 (4.1-28.1), risk score = 24
  • Respiratory Infection in the Last Month: adjusted odds ratio = 5.5 (2.6-11.5), risk score = 17
  • Surgical Incision
    • Upper Abdominal Surgery: adjusted odds ratio = 4.4 (2.3-8.5), risk score = 15
    • Intrathoracic Surgery: adjusted odds ratio = 11.4 (1.9-26.0), risk score = 24
  • Risk Class
    • Low (<26 Points): 1.6% postoperative pulmonary complication rate
    • Intermediate (26-44 Points): 13.3% postoperative pulmonary complication rate
    • High (≥45 Points): 42.1 % postoperative pulmonary complication rate

Etiology

Obstructive Atelectasis (Due to Airway Obstruction) (see Obstructive Lung Disease)

General Comments

  • Airway Obstruction (of Any Etiology) Results in Absorptive Atelectasis Distal to the Site of Obstruction
    • Furthermore, High Inspired Oxygen Concentration (Which is Common in the Intensive Care Unit) Favors Alveolar Gas Absorption, Enhancing the Development of Atelectasis (J Appl Physiol, 2013) [MEDLINE]

Tracheobronchial Infection with Intrinsic Airway Obstruction

  • Actinomycosis (see Actinomycosis)
    • Epidemiology
      • Case Reports of Endobronchial Actinomycosis (Chest, 2002) [MEDLINE]
  • Klebsiella Rhinoscleroma (see Klebsiella Rhinoscleroma)
    • Clinical
      • While Nasopharyngeal Involvement is the Most Common Anatomic Site, Tracheal Involvement Can Occur in Rare Cases
  • Mycobacteria
    • Mycobacterium Avium Complex (MAC) (see Mycobacterium Avium Complex)
      • Endobronchial Disease Cases May Occur
    • Mycobacterium Tuberculosis (Tuberculosis) (see Tuberculosis)
      • Endobronchial Disease Cases May Occur
  • Nocardiosis (see Nocardiosis)
    • Epidemiology
      • Case Reports of Endobronchial Nocardiosis (Eur Respir J, 1994) [MEDLINE] (Mt Sinai J Med, 2006) [MEDLINE]
  • Aspergillus Tracheobronchitis (see Invasive Aspergillosis)
    • Clinical
      • Aspergillosis of Bronchial Stump (in Lung Transplant Patient)
      • Obstructive Bronchial Aspergillosis
      • Pseudomembranous Tracheobronchitis
      • Ulcerative Tracheobronchitis

Tracheobronchial Neoplasm with Intrinsic Airway Obstruction

  • Primary Endobronchial Benign or Malignant Tumor
    • Example: Bronchial Adenoma (see Bronchial Adenoma)
      • Obstruction by Endotracheal or Endobronchial Adenoma
    • Example: Bronchial Carcinoid (see Bronchial Carcinoid)
      • Obstruction by Endotracheal or Endobronchial Carcinoid
    • Example: Lung Cancer (see Lung Cancer)
      • Obstruction by Endotracheal or Endobronchial Disease
  • Endobronchial Metastases (see Lung Metastases-Endobronchial)

Extrinsic Tracheobronchial Airway Compression

Other Tracheobronchial Obstructive Process

  • Bronchial Stenosis (see Bronchial Stenosis)
    • Physiology
      • Narrowed Bronchial Airway
  • Bronchocentric Granulomatosis (see Bronchocentric Granulomatosis)
  • Broncholithiasis (see Broncholithiasis)
    • Physiology
      • Endotracheal or Endobronchial Obstruction by Broncholith
  • Bronchopulmonary Amyloidosis (see Amyloidosis)
    • Physiology
      • Endobronchial Obstruction by Nodular Amyloid Lesions
  • Bronchospasm
  • Cystic Fibrosis (CF) (see Cystic Fibrosis)
    • Epidemiology
      • Atelectasis is Present in 5% of of Cystic Fibrosis Patients During the First 5 Years of Life (and Incidence Decreases with Aging) (Am Rev Respir Dis, 1978) [MEDLINE]
      • May Occur During an Exacerbation or without Other Clinical Symptoms
    • Physiology
      • Aspergillus-Associated Mucoid Impaction Can Be Etiologic in Some Cases (See Below) (Pediatr Radiol, 2007) [MEDLINE]
      • However, Most Cases Do Not Have a Demonstrable Mucoid Impaction on Bronchoscopy
    • Clinical
      • Atelectasis May Be Lobar or Segmental
      • Atelectasis Has a Right-Lung Predominance
  • Inadvertent Placement of Nasogastric/Orogastric Tube into Tracheobronchial Tree (see Nasogastric/Orogastric Tube)
    • Physiology
      • Inadvertent Placement of Nasogastric/Orogastric Tube into the Tracheobronchial Tree with Airway Obstruction
  • Mucoid Impaction in Tracheobronchial Airway (see Mucoid Impaction)
  • Mucous Plugging of Tracheobronchial Airway
    • Epidemiology
      • Common Etiology of Airway Obstruction in the Intensive Care Unit
      • Associated with Bacterial Pneumonia (Particularly in a Patient with Other Risk Factors for Poor Secretion Clearance, Such as Altered Mental Status, Neuromuscular Disease, etc)
  • Post-Pneumonectomy Syndrome (see Post-Pneumonectomy Syndrome)
    • Physiology
      • Dynamic Airway Obstruction Caused by Severe Rotation and Shift of the Mediastinum After Pneumonectomy
  • Post-Radiation Therapy (see Radiation Therapy)
    • Physiology
      • Endobronchial Granulation Tissue (or Stricture)
  • Relapsing Polychondritis (see Relapsing Polychondritis)
    • Physiology
      • Endotracheal or Endobronchial Obstruction by Loss of Supporting Cartilage in Airways
  • Smoke Inhalation (see Smoke Inhalation)
    • Physiology
      • Tracheobronchial Mucosal Injury with Sloughing and Airway Obstruction
  • Toxic Fume Airway Injury
    • Epidemiology
      • Example: ammonia inhalation (see Ammonia)
    • Physiology
      • Tracheobronchial Mucosal Injury with Sloughing and Airway Obstruction
  • Tracheobronchial Foreign Body (see Airway Foreign Body)
    • Physiology
      • Endotracheal or Endobronchial Obstruction by Foreign Body
  • Tracheobronchial Fracture (see Tracheobronchial Fracture)
    • Physiology
      • May Result in Compromised Patency of the Tracheal or Bronchial Lumen
  • Tracheobronchomalacia (see Tracheobronchomalacia)
    • Physiology
      • Abnormally Collapsible Trachea and/or Bronchial Airways
  • Tracheoesophageal Fistula (TEF) (see Tracheoesophageal Fistula)
    • Physiology
      • May Result in Compromised Patency of the Tracheal Lumen
  • Tracheobronchopathia Osteochondroplastica (TPO) (see Tracheobronchopathia Osteochondroplastica)
    • Physiology
      • Multiple Cartilaginous or Bony Submucosal Endotracheal or Endobronchial Nodules (Either of Which May Produce Airway Obstruction)
  • Granulomatosis with Polyangiitis (GPA) (Wegener’s Granulomatosis) (see Granulomatosis with Polyangiitis)
    • Physiology
      • Endotracheal or Endobronchial Obstruction by Granulomatous Tissue

Non-Obstructive Atelectasis

Abdominal Disorder

  • Abdominal Pain/Abdominal Surgery (see Abdominal Pain)
    • Epidemiology
      • Abdominal Splinting is Common After Abdominal Surgery
    • Physiology
      • Incisional Pain Restricts Inspiration
      • Abdominal Surgery Impairs Diaphragmatic Activity
        • Diaphragmatic Activity During Expiration Normally Functions to Slow the Rate of Lung Deflation, Preventing Closure of Dependent Small Airways
        • Incisions in the Upper Abdomen or Lower/Midline Thorax Decrease Diaphragmatic Contractility (Regardless of Presence of Pain) (Am Rev Respir Dis, 1983) [MEDLINE]
        • In Contrast, Lower Abdominal Incisions (Laparoscopic Procedures, etc) Have a Very Limited Impact on Diaphragmatic Functioning (Arch Surg, 1993) [MEDLINE]
  • Abdominal Compartment Syndrome (see Abdominal Compartment Syndrome)
    • Physiology
      • Increased Intra-Abdominal Pressure, Resulting in Decreased Thoracic Volume
      • Abdomen-Impeded Diaphragmatic Descent Decreases the Functional Residual Capacity (FRC)
  • Ascites (Large Volume) (see Ascites)
    • Physiology
      • Increased Intra-Abdominal Pressure, Resulting in Decreased Thoracic Volume
      • Abdomen-Impeded Diaphragmatic Descent Decreases the Functional Residual Capacity (FRC)
  • Obesity (see Obesity)
    • Physiology
      • Increased Intra-Abdominal Pressure, Resulting in Decreased Thoracic Volume
      • Abdomen-Impeded Diaphragmatic Descent Decreases the Functional Residual Capacity (FRC)
      • In a Study of Sedated and Paralyzed Patients, Morbid Obesity Decreased the Functional Residual Capacity (FRC) and Increased the Alveolar-Arterial Oxygen (A-a O2) Gradient (J Appl Physiol, 1997) [MEDLINE]
  • Pregnancy (see Pregnancy)
    • Physiology
      • Increased Intra-Abdominal Pressure, Resulting in Decreased Thoracic Volume
      • Abdomen-Impeded Diaphragmatic Descent Decreases the Functional Residual Capacity (FRC)

Thoracic Surgery/Trauma

  • Thoracic Surgery
    • Physiology
      • Incisional Pain Restricts Inspiration
      • Thoracic Surgery Impairs Diaphragmatic Activity
        • Diaphragmatic Activity During Expiration Normally Functions to Slow the Rate of Lung Deflation, Preventing Closure of Dependent Small Airways
        • Incisions in the Upper Abdomen or Lower/Midline Thorax Decrease Diaphragmatic Contractility (Regardless of Presence of Pain) (Am Rev Respir Dis, 1983) [MEDLINE]
        • In Contrast, Lower Abdominal Incisions (Laparoscopic Procedures, etc) Have a Very Limited Impact on Diaphragmatic Functioning (Arch Surg, 1993) [MEDLINE]
  • Thoracic Trauma
    • Types
    • Physiology
      • Traumatic Airway Injury May Result in Airway Mucosal Edema, Which Decreases Airway Diameter and Impedes Secretion Clearance
      • Traumatic Lung Injury May Cause Lung Parenchymal Edema
      • Trauma-Associated Chest Wall Pain (with Associated Rib Fractures, etc) May Decrease Tidal Volume and Impair Cough and Secretion Clearance
      • Pulmonary Contusion Causes Pulmonary Surfactant Dysfunction (see Pulmonary Contusion): see below

Space-Occupying Intrathoracic Disorder

  • Bullae (see Bullae)
    • Physiology
      • Expansion of Bulla (Especially on Mechanical Ventilation), Resulting in Compression of Adjacent Lung
        • Due to Increased Compliance of the Bullous Lesion, Airflow on Mechanical Ventilation Tends to Be Redirected to the Bullous Lesion with Disproportionate Expansion of It (as Compared the Remaining Lung)
  • Large Intrathoracic Tumor with Compression of Adjacent Lung
  • Pleural Effusion (see Pleural Effusion-Transudate and Pleural Effusion-Exudate):
    • Physiology
      • Loss of Contact Between the Visceral and Parietal Surfaces with Deformation of Shape of the Lung, Resulting in Atelectasis
      • Even a Small Pleural Effusion Can Compress the Adjacent Lung
  • Pneumothorax (see Pneumothorax)
    • Non-Tension Pneumothorax
      • Introduction of Air into Pleural Space Leads to Compression of Adjacent Lung (to Some Extent) and the Loss of Contact Between the Visceral and Parietal Surfaces with Deformation of Shape of Lung, Resulting in Atelectasis
    • Tension Pneumothorax
      • Mechanism Involves Positive Pressure in the Pleural Space with Compression of Adjacent Lung

Neuromuscular Disease (see Respiratory Failure)

  • Mechanism
    • Diaphragmatic Weakness/Paralysis with Pressure of Abdominal Contents on the Diaphragm
    • Poor Inspiration with Low Tidal Volumes
    • Impaired Cough Reflex (with Decreased Mucous Clearance)
    • Decreased Distribution of Ventilation
  • Types of Neuromuscular Disease
    • Chemosensitivity Disorders
    • Brainstem Disease
    • Spinal Cord Disease
    • Upper Motor Neuron Disease
    • Peripheral Neuropathy (see Peripheral Neuropathy)
    • Neuromuscular Junction Disease
    • Myopathy (see Myopathy)

Cicatrization Atelectasis

Impaired Lung Surfactant Activity

  • Acute Respiratory Distress Syndrome (ARDS) (see Acute Respiratory Distress Syndrome)
    • Physiology
      • ARDS is Associated with Decreased Surfactant Synthesis or Decreased Surfactant Activity, Resulting in Alveolar Instability and Collapse
      • Lung-Protective Low Tidal Volume Ventilation Used Commonly in the Treatment of ARDS May Predispose to the Development of Atelectasis (Respir Care, 2001) [MEDLINE]
  • Aspiration (see Aspiration Pneumonia)
    • Physiology
      • Gastric Acid Aspiration Decreases the Amount of Functional Surfactant, Resulting in Alveolar Instability and Collapse
  • Coronary Artery Bypass Grafting (CABG) Surgery (see Coronary Artery Bypass Graft)
    • Physiology
      • CABG Surgery Impairs Lung Surfactant Activity (J Thorac Cardiovasc Surg, 1993) [MEDLINE]
  • Prolonged Low Tidal Volumes
    • Epidemiology
    • Physiology
      • Persistently Low Tidal Volumes Predispose to Development of Atelectasis (Respir Care, 2001) [MEDLINE]
        • This Can Countered by Periodic Sighs and/or Positive End-Expiratory Pressure (PEEP)
  • Pulmonary Contusion (see Pulmonary Contusion)
    • Physiology
      • Surfactant Dysfunction, Resulting in Alveolar Instability and Collapse
  • Radiation Pneumonitis (see Radiation Pneumonitis and Fibrosis)
    • Physiology
      • Surfactant Inactivation, Resulting in Alveolar Instability and Collapse
  • Smoke Inhalation (see Smoke Inhalation)
    • Physiology
      • Surfactant Dysfunction
  • Uremia (see Chronic Kidney Disease)
    • Physiology
      • Surfactant Dysfunction

Acceleration Atelectasis

  • Epidemiology
    • Acceleration Atelectasis Has Been Described in Pilots Subjected to High, Vertical Accelerative Forces (Between 5-9G) (Aviat Space Environ Med, 1987) [MEDLINE]
      • At 5G, up to 50% of Pulmonary Airways are Distorted and/or Closed Due to Gravitational Forces
  • Physiology
    • Acceleration Atelectasis is Exacerbated by Breathing a High Fractional Concentration of Oxygen
    • Decreased Vital Capacity (VC)

Other

  • Acute Pulmonary Embolism (PE) (see Acute Pulmonary Embolism)
    • Physiology
      • Alteration in Lung Surfactant (Eur J Med Res, 2009) [MEDLINE]
      • Other Mechanisms May Play a Role, as Well
  • Ankylosing Spondylitis (see Ankylosing Spondylitis)
    • Epidemiology
      • Atelectasis Occurs in a Small Percentage of Cases
  • Bronchioloalveolar Carcinoma (BAC) (see Lung Cancer)
    • Physiology
      • Causes “Replacement Atelectasis”, Where the Alveoli of an Entire Lobe of the Lung are Filled with Tumor Cells
  • Endotracheal Intubation (see Endotracheal Intubation)
    • Mechanisms
      • Coaxial Positioning of the Endotracheal Tube’s Narrow Opening
      • Cuff-Blockaded Transfer of Tracheal Secretions to the Pharynx
      • Prevention of Glottic Closure
  • Esophageal Variceal Sclerotherapy (see Esophageal Varices)
    • Epidemiology
      • Atelectasis Occurs in 12% of Cases
  • General Inhalational Anesthesia (see General Anesthesia)
    • Epidemiology
      • Data from the I-LOCATE Trial Indicate that the Incidence of Atelectasis Developing During Bronchoscopy Performed Under General Anesthesia in Dependent Lung Zones is High (Occurred in 89% of Cases) (Chest, 2020) [MEDLINE]
        • Median Time from Anesthesia Induction to Development of Atelectasis: 33 min (Range: 3-94 min) (Chest, 2020) [MEDLINE]
        • The Degree of Atelectasis Which Occurs Following Bronchoscopy Performed Under General Anesthesia is Proportional to Body Mass Index and Length of General Anesthesia (Chest, 2020) [MEDLINE]
    • Physiology
      • General Inhalational Anesthesia Causes Atelectasis, Independent of Other Risk Factors (Such as Hyperoxia, Recumbent Position, Surgical Incisions, etc)
      • General Anesthesia Causes a Loss in Muscle Tone, Resulting in a Decrease in Functional Residual Capacity (FRC) (see General Anesthesia) (Best Pract Res Clin Anaesthesiol, 2010) [MEDLINE]
      • General Anesthesia Impairs the Mucociliary Escalator (Am Rev Respir Dis, 1976) [MEDLINE]
      • General Anesthesia Promotes Secretion Generation (Am Rev Respir Dis, 1976) [MEDLINE]
  • Hyperoxia (Excessive Oxygen Administration) (see Oxygen)
    • Epidemiology
      • Hyperoxia May Occur During Induction for General Anesthesia in the Preoperative Setting (Best Pract Res Clin Anaesthesiol, 2010) [MEDLINE]
    • Physiology
      • Hyperoxia Results in Washout of Nitrogen from Alveolus, Resulting in Oxygen Absorption from the Alveolus into the Blood, Leading to a Small Alveolus Which is Prone to Collapse (“Absorptive Atelectasis”)
      • Inhalation of 100% Oxygen During Anesthesia for Only 5 min Results in Atelectasis with Increased Intrapulmonary Right-to-Left Shunt (Anesthesiology, 2003) [MEDLINE]
  • Opiates (see Opiates)
    • Physiology
      • At Moderate Doses, Opiates Tend to Preserve the Tidal Volume, But Decrease the Respiratory Rate (Which Predisposes to the Development of Atelectasis) (Anaesthesia, 1999) [MEDLINE] (Br J Anaesth, 2008) [MEDLINE]
      • Use of Excessive Analgesia During the Postoperative Period, etc Decreases Respiratory Drive and Impairs the Cough Reflex (Lung, 1981) [MEDLINE]
  • Recumbent Body Position
    • Mechanism
      • Recumbent Body Position Decreases the Functional Residual Capacity (FRC)
      • Healthy Adult Loses 700-1,200 mL of Functional Residual Capacity (FRC) in the Transition from Sitting to Fully Supine (Recumbent) Body Position (Am Rev Respir Dis, 1984) [MEDLINE]
      • In the Fully Supine Position, the Weight of the Heart and Mediastinum Narrow and Pinch the Left Lower Lobe Bronchi (Am J Respir Crit Care Med, 2000) [MEDLINE]

Physiology

Background

Normal Lobar Lung Anatomy

  • The Lung is Divided into Lobes by Fissures Which are Relatively Impermeable to Gas Transfer
    • This Anatomic Configuration Likely Serves to Compartmentalize Infection and Tissue Damage to a Smaller Region of the Lung (Crit Care Med, 2008) [MEDLINE]
    • However, Some Lung Fissures are Incomplete, Allowing Collateral Ventilation

Relative Frequency of the Laterality of Lower Lobe Atelectasis

  • Collapse of the Left Lower Lobe Occurs Approximately Twice as Commonly as Collapse of the Right Lower Lobe (Br J Radiol, 1983) [MEDLINE]
    • While the Right Mainstem Bronchus Has a Straighter Course than the Left Mainstem Bronchus, the Observed Increased Frequency of Left Lower Lobe Collapse is Likely Explained by Cardiac Compression and Deformation of Gravitationally-Dependent Bronchi (Am J Respir Crit Care Med, 2000) [MEDLINE]

Mechanical Determinants of the Functional Residual Capacity (FRC)

  • Functional Residual Capacity (FRC) is a Reflection of the Balance Between the Lung’s Tendency to Collapse and the Chest Wall’s Tendency to Expand
    • FRC is Typically Preserved or Increases with Aging (Clin Interv Aging, 2006) [MEDLINE]
    • Recumbent Body Position Significantly Decreases the FRC, Due to the Following Factors
      • Abdomen-Impeded Diaphragmatic Descent: prominent factor
        • The Positional Changes of Pressure and Volume are Most Pronounced Over the Range of 60° to 0° from Horizontal (Scand J Rehab Med, 1971) [MEDLINE]
      • Alterations of the Chest Wall Configuration
      • Hydrostatic Forces
    • Transpulmonary Pressures (Alveolar-Pleural Pressures) in the Dependent Regions of the Lung are Lower than Those in Superior Regions of the Lung
    • The Lung Volume at Which Closure of Dependent Airways Begins is Termed the Closing Volume
    • With Aging, the FRC May Decrease Below the Closing Volume (Especially in the Recumbent Body Position) (J Appl Physiol, 1970) [MEDLINE]

Role of Alveolar-Capillary Gas Exchange in Preventing Alveolar Collapse

  • During Normal Room Air Breathing, Venous Blood Flowing Past the Alveolus Has a pO2 Which is Approximately 50 mm Hg Below the Atmospheric pO2 (Due to the Normal Arteriovenous Oxgen Differential)
    • Maintaining the Pulmonary Capillary to Alveolus Diffusion Gradient (While Sustaining Alveolar Patency) Requires a Continuous Supply of Gas and Maintenance of Adequate Transpulmonary Pressure to Counter the Forces Which Favor Lung Recoil (i.e. Collapse)
  • Hyperoxia Results in Washout of Nitrogen from Alveolus, Resulting in Oxygen Absorption from the Alveolus into the Blood, Leading to a Small Alveolus Which is Prone to Collapse (“Absorptive Atelectasis”)
    • Inhalation of 100% Oxygen During Anesthesia for Only 5 min Results in Atelectasis with Increased Intrapulmonary Right-to-Left Shunt (Anesthesiology, 2003) [MEDLINE]
    • When Breathing 100% FIO2, Absorptive Collapse of a Lobe with Compromised Ventilation May Occur in <60 min, While Complete Absorption While Filled with Room Air May Require 12-24 hrs (J Appl Physiol, 2013) [MEDLINE]

Mechanisms of Atelectasis

Mechanism of Obstructive Atelectasis (Most Common Mechanism of Atelectasis)

  • Endobronchial Airway Obstruction (at Any Point Between the Trachea and Distal Airways), Resulting in Reabsorption of Alveolar Oxygen and Nitrogen (with Collapse of Previously Aerated Lung)
  • Rate of Development of Atelectasis Depends on the Degree of Obstruction (Complete vs Partial), Presence of Collateral Ventilation to the Affected Alveoli (Provided by the Pores of Kohn and Canals of Lambert), and Composition of the Inspired Gas
  • Stages
    • Early Stage: collapse of aerated lung within hours (volume loss), leading to V/Q mismatch (with resulting hypoxemia) and mediastinal shift toward the atelectatic side
    • Later Stage: filling of collapsed alveoli with cells and secretions (which may prevent complete collapse)
    • Late Stage: persistent obstruction, leading to infection, fibrosis, and/or bronchiectasis

Mechanism of Non-Obstructive Atelectasis

  • May Occur Due to a Space-Occupying Lesion in the Thorax with Compression of Adjacent Lung, Due to Loss of Surfactant (with Alveolar Collapse), Due to the Loss of Visceral-Parietal Pleural Contact (Due to Pleural Effusion, Pneumothorax), or Due to Replacement of Parenchymal Lung Tissue by Scarring or Infiltrative Disease
    • Middle and Lower Lobes Tend to Collapse More Readily in the Presence of Pleural Effusion
    • Upper lobes tend to collapse more readily in the presence of pneumothorax
  • Atelectasis Also Contributes to the Development of Pleural Effusion
    • Atelectasis (of Any Etiology) Creates Decreased Perimicrovascular Pressure, Resulting in Movement of Fluid from Parietal Pleural Interstitium into the Pleural Space (Until the Gradient Equalizes)

Consequences of Lobar Atelectasis

  • Impaired Global Lung Compliance with Increased Ventilatory Workload, Resulting in Hypoxemic, Hypercapnic Respiratory Failure (see Respiratory Failure)
  • Arterial Hypoxemia/Hypoxemic Respiratory Failure (see Hypoxemia and Respiratory Failure)
  • Increased Right Ventricular Afterload (In Cases with Extensive Atelectasis)
    • Due to Mechanical Vascular Obstruction and Reactive Vasoconstriction

Diagnosis

Physical Exam

Chest X-Ray (CXR)/Chest Computed Tomography (CT) (see Chest X-Ray and Chest Computed Tomography)

  • Both are Usual Imaging Modalities to Diagnose Atelectasis and Assess for Potential Etiologies
  • Obstructive Atelectasis
    • Volume Loss with Shifting of Mediastinum Toward Side of Atelectasis (Except in Cases Where the Mediastinum/Trachea are Anatomically Fixed)

Bronchoscopy (see Bronchoscopy)

  • Bronchoscopy May Be Required to Exclude an Endobronchial Lesion
  • Bronchoscopic Evaluation is Particularly Indicated in Patients with Unexplained Atelectasis Which Might Represent an Undiagnosed Endobronchial Lesion
    • Delayed Diagnosis of Such Endobronchial Lesions is a Common Medical-Legal Issue

Clinical Manifestations

General Presentations

  • Asymptomatic
    • Atelectasis May Be Asymptomatic in Some Cases
  • Chest Pain (see Chest Pain)
    • Epidemiology
      • May Occur
  • Cough (see Cough)
    • Epidemiology
      • Cough is Particularly Common with Atelectasis Associated with Middle Lobe Syndrome (see Middle Lobe Syndrome)
  • Dyspnea (see Dyspnea)
    • Epidemiology
      • May Occur
  • Hypoxemia (see Hypoxemia)
    • Physiology
      • Hypoxemia Occurs Due to Perfusion of Collapsed Lung (at Least in the Early Stages of Atelectasis), Resulting in V/Q Mismatch
  • Small Unilateral Pleural Effusion (see Pleural Effusion-Transudate)
    • Epidemiology
      • Atelectasis May Result from a Pleural Effusion (Via Compressive Mechanisms)
      • Atelectasis May Also Cause a Small Pleural Effusion
    • Diagnosis
      • Chest X-Ray (CXR)/Chest Computed Tomography (CT) Pattern (see Chest X-Ray and Chest Computed Tomography)
        • Usually Small, Unilateral Pleural Effusion, with Associated Volume Loss (and Normal Heart Size)
      • Pleural Fluid is Typically Transudative in Cases of Effusion Which Occurs Secondary to Atelectasis (However, in Cases Where the Pleural Effusion is the Primary Event, Pleural Fluid May Be Either Transudative or Exudative)
        • Pleural Fluid Appearance: serous
        • Pleural Fluid pH: >7.4
        • Pleural Fluid Glucose: same as serum glucose
        • Pleural Fluid Cell Count/Differential: <1000 cells (mononuclear-predominant)
  • Acute Respiratory Failure (see Respiratory Failure)
    • Epidemiology
      • Respiratory Failure May Occur in Association with the Acute Development of Large Volume Atelectasis (Either Obstructive or Non-Obstructive)
  • Plate-Like/Discoid/Subsegmental Atelectasis
    • Physiology
      • Likely Occurs Due to Small Bronchial Obstruction (Which May Occur with Hypoventilation, Pulmonary Embolism, or Lower Respiratory Tract Infection)
    • Diagnosis
  • Post-Operative Atelectasis
    • Epidemiology
      • Common After Thoracic or Abdominal Surgery
    • Physiology
      • Likely Occurs Due to Effects of General Anesthesia, Manipulation of the Lung, Diaphragmatic Dysfunction, Hypoventilation (Due to Pain), and/or Surfactant Dysfunction
    • Prevention
      • Recruitment Maneuver Followed by PEEP, May Together Decrease the Development of Atelectasis and Improved Oxygenation in Morbidly Obese Patients Undergoing General Anesthesia (Anesthesiology, 2009) [MEDLINE]
  • Lack of Association Between Atelectasis and Fever
    • Studies Do Not Indicate that There is a Correlation Between Atelectasis and Fever (Chest, 2011) [MEDLINE]

Rounded Atelectasis (see Rounded Atelectasis)

  • Definition
    • Rounded Atelectasis is a Region of Circularly-Folded Atelectatic Lung Tissue, Typically with Adhesions to the Visceral Pleura
  • Etiology
    • Mineral Dust Exposure (Asbestos, Silica, etc)
    • Exudative Pleural Effusion
    • Pneumothorax
    • Absence of Significant Pleural Disease
  • Diagnosis
    • Chest CT Criteria (see Chest Computed Tomography)
      • “Comet-Tail Sign”
      • Contiguity to Areas of Diffuse Pleural Thickening
      • Lentiform or Wedge-Shaped Outline
      • Volume Loss

Middle Lobe Syndrome (Brock Syndrome) (see also Middle Lobe Syndrome)

  • Definition
    • Middle Lobe Syndrome is Most Consistently Defined in the Medical Literature as Recurrent or Chronic Right Middle Lobe Atelectasis (see Atelectasis) (Postgrad Med, 1948) [MEDLINE] (Dis Chest, 1966) [MEDLINE] (Thorax, 1980) [MEDLINE] (Respiration, 2012) [MEDLINE]
    • A Similar Syndrome May Also Occur in the Lingula, Being Termed the “Lingula Syndrome” (Chest, 2004) [MEDLINE]
  • Etiology
    • Similar to Other Types of Atelectasis, Middle Lobe Syndrome Can Be Either Obstructive or Non-Obstructive
  • Clinical
    • Asymptomatic, Incidentally-Noted Right Middle Lobe Atelectasis on Chest X-Ray (CXR) or Chest Computed Tomography (CT) (see Chest X-Ray and Chest Computed Tomography)
    • Chest Pain (see Chest Pain)
      • May Occur (Clin Respir J, 2009) [MEDLINE]
    • Cough (see Cough)
      • Occurs in 30-50% of Cases (Clin Respir J, 2009) [MEDLINE] (Respiration, 2012) [MEDLINE]
    • Dyspnea (see Dyspnea)
      • May Occur (Clin Respir J, 2009) [MEDLINE]
    • Wheezing (see Wheezing)
      • May Occur
    • Post-Obstructive Pneumonia (see Community-Acquired Pneumonia)
      • In One Histopathologic Study of Right Middle Lobe Syndrome Cases Cured Surgically (n = 60), 60% Had Chronic Suppurative Infection, 33% Had Neoplasm, and 7% Had Tuberculosis (Med Interne, 1982) [MEDLINE]
    • Bronchiectasis (see Bronchiectasis)
      • Occurs in 50% of Cases (Respiration, 2012) [MEDLINE]

Prevention of Postoperative Atelectasis (and Other Postoperative Pulmonary Complications)

Preoperative Measures

Incentive Spirometry (see Incentive Spirometry)

  • Useful as Preventive Strategy
    • Note that the Benefit is Greatest When Incentive Spirometry is Started Preoperatively (Especially if Education Regarding its Use is Provided)

Smoking Cessation (see Tobacco)

  • Clinical Efficacy
    • Smoking Cessation Improves Wound Healing and Postoperative Pulmonary Recovery (Cochrane Database Syst Rev, 2010) [MEDLINE]
    • Smoking Cessation for >8 wks Prior to the Procedure Appears to Be Preferred (Cochrane Database Syst Rev, 2010) [MEDLINE]

For Patients with Asthma/Chronic Obstructive Pulmonary Disease (COPD), Optimize Disease Control (see Asthma and Chronic Obstructive Pulmonary Disease)

  • Therapies
    • Bronchodilators
    • Inhaled Corticosteroids (see Corticosteroids)
    • Systemic Corticosteroids (see Corticosteroids)
      • Systemic Corticosteroids (Prednisone 40 mg/day x 5 Days, etc) May Be Required for a Patient with an Acute Exacerbation
  • Delay in Surgery
    • May Be Required in Cases Where Disease Control Cannot Be Adequately Established Prior to the Surgical Procedure

Treat Active Respiratory Infection (If Present)

  • Therapies
    • Antibiotics
  • Delay in Surgery
    • May Be Required in Cases Where an Active Respiratory Infection Cannot Be Adequately Treated Prior to the Surgical Procedure

Preoperative Oral Care

  • Therapies
    • Dental Hygienist Visit
    • Preoperative Chlorhexidine Mouthwash

Chest Physical Therapy (CPT) (see Chest Physical Therapy)

  • Therapies
    • Aerobic Exercises
    • Breathing Exercises
    • Inspiratory Muscle Training
  • Clinical Efficacy
    • Preoperative Exercise Program May Decrease the Risk of Postoperative Pulmonary Complications in Patients Undergoing Elective Lung, Cardiac or Abdominal Surgery (JAMA, 2006) [MEDLINE] (Clin Rehabil, 2011) [MEDLINE] (Cochrane Database Syst Rev, 2012) [MEDLINE] (Cochrane Database Syst Rev, 2015) [MEDLINE] (Eur J Vasc Endovasc Surg, 2015) [MEDLINE]
    • Australian Double-Blinded, Randomized Controlled Trial of Preoperative Chest Physical Therapy in the Prevention of Pulmonary Complications in Patients Undergoing Upper Abdominal Surgery (BMJ, 2018) [MEDLINE]: n = 441 adults
      • A 30 min Preoperative Physiotherapy and Breathing Exercise Training Session (within an Existing Hospital Multidisciplinary Preadmission Clinic) Halves the Incidence of Postoperative Pulmonary Complications and Specifically Hospital-Acquired Pneumonia

Intraoperative Measures

Utilize a Shorter Surgical Procedure (<3 hrs, If Possible)

  • Shorter Surgical Procedure Will Shorten the General Anesthesia Time

Utilize a Less Invasive Surgical Procedure (If Possible)

  • Types of Less Invasive Procedure (Assuming that Operative Time is Not Prolonged)
    • Laparoscopic Procedure
    • Robotic Procedure

Utilize Neuraxial Anesthesia (If Possible)

  • Neuraxial Anesthesia is Preferred Over General Anesthesia

Utilize Regional Anesthesia (If Possible)

  • Regional Anesthesia (Nerve Block) is Preferred, When This is an Option

Intraoperative Lung Protective Ventilation

  • International Expert Panel-Based Consensus Moderate to High-Quality Statements and Recommendations for Lung-Protective Ventilation for the Surgical Patient (Br J Anaesth, 2019) [MEDLINE]
    • Formation of Perioperative Clinically Significant Atelectasis May Be an Important Risk Factor for the Development of Postoperative Pulmonary Complications
    • Decreasing Lung/Chest Wall Compliance Caused by Surgical/Anaesthesia-Related Factors (i.e. Pneumoperitoneum, Positioning, and Circuit Disconnect) Should Be Treated by Appropriate Interventions
    • Individualized PEEP Can Prevent Progressive Alveolar Collapse
    • Recruitment Maneuvers Can Reverse Alveolar Collapse, But Have Limited Benefit without Sufficient PEEP
    • Increasing FIO2 May be Effective in Increasing the Oxygenation, But is Not an Effective Intervention to Improve Dynamic Compliance of the Respiratory System
    • Low Tidal Ventilation (6-8 ml/kg) and PEEP (+5 cm H2O) Should Be Used Initially (Zero PEEP is Not Recommended)
    • Appropriate PEEP and Recruitment Maneuvers May Improve Intraoperative Respiratory Function and Prevent Postoperative Pulmonary Complications
    • Before Anesthesia Induction, Position the Patient with the Head of Bed Elevated >30° (and Avoid Supine Positioning, If Possible)
      • If Not Contraindicated, Before the Loss of Spontaneous Ventilation, Use NIPPV or CPAP to Attenuate Anaesthesia-Induced Respiratory Changes
    • In Addition to Standard Monitoring, Dynamic Compliance, Driving Pressure (Plateau Pressure – PEEP) and Plateau Pressure Should Be Monitored on All Mechanically-Ventilated Patients
    • Continuous Hemodynamic and Oxygen Saturation Monitoring is Recommended Before and During the Performance of an Alveolar Recruitment Maneuver
      • Ensure Adequate Hemodynamic Stability Before Performing an Alveolar Recruitment Maneuver
      • Avoid Alveolar Recruitment Maneuvers when Contraindicated

For Patients with Asthma/Chronic Obstructive Pulmonary Disease (COPD), Administer Short-Acting β-Adrenergic Agonists (SABA’s) Prior to Intubation (see Asthma and Chronic Obstructive Pulmonary Disease)

  • Therapies
    • Administer SABA 2-4 Puffs within 30 min Prior to Intubation

Avoid Long-Active Neuromuscular Junction Antagonists

  • Avoid Long-Active Neuromuscular Junction Antagonists During Induction and the Surgical Procedure (If Possible)

Avoid Swan-Ganz Catheter Placement (If Possible) (see Swan-Ganz Catheter)

  • Avoid Swan-Ganz Catheter Placement, Unless Required for the Procedure Itself (Such as For a Procedure Requiring Intraoperative Management of Congenital Heart Disease, Pulmonary Hypertension, etc)

High-Flow Nasal Cannula (HFNC) (see Oxygen)

  • Clinical Efficacy
    • Study of High-Flow Nasal Cannula vs Face Mask Oxygen in Patients Undergoing CT-Guided Hepatic Tumor Radiofrequency Ablation Under Deep Sedation (Eur J Anaesthesiol, 2020) [MEDLINE]
      • HFNC Oxygen Group Exhibited Les Postprocedural Atelectasis than the Face Mask Oxygen Group (Median 7.4 [Interquartile Range: 3.9-11.4%] vs 10.5 [Interquartile Range: 7.2-14.6%]; p = 0.0313)
      • The Number of Patients Requiring Oxygen Supplementation in the Recovery Room and During Transport from the Recovery Room to the Ward Did Not Differ Significantly Between the Groups (24.1 vs. 50.0%; p = 0.0596)

Ultrasound-Guided Lung Recruitment

  • Clinical Efficacy
    • Study of Ultrasound-Guided Lung Recruitment on the Development of Postoperative Atelectasis in Children Undergoing Simple Procedures (with Associated Endotracheal Intubation) (Eur J Anaesthesiol, 2020) [MEDLINE]
      • No Significant Difference Between the Groups, in Terms of Degree of Atelectasis as Assessed in the Post-Anesthesia Care Unit (PACU)
      • An Inspiratory Airway Pressure of >30 cm H2O was Required for Full Recruitment of Alveoli in Healthy Children

Continuous Positive Airway Pressure (CPAP) (see Continuous Positive Airway Pressure)

  • Clinical Efficacy
    • Study of Continuous Positive Airway Pressure to Prevent Postoperative Atelectasis in Anesthetized Children (Eur J Anaesthesiol., 2021) [MEDLINE]
      • Use of 5 cm H2O of CPAP in Healthy Children (Aged 6 mos-7 y/o) During Induction and Emergence of Anesthesia Prevented Atelectasis, with a Benefit Maintained During the First Postoperative Hour

Postoperative Measures

Incentive Spirometry (see Incentive Spirometry)

  • Useful as Preventive Strategy
    • Note that the Benefit is Greatest When Incentive Spirometry is Started Preoperatively
  • Clinical Efficacy
    • Systematic Review of Incentive Spirometry to Prevent Pulmonary Complications After CABG Surgery (Cochrane Database Syst Rev, 2007) [MEDLINE]: n = 4 trials (n = 443 patients)
      • Individual Small Trials Suggest No Evidence of Clinical Benefit of Incentive Spirometry in Decreasing Postoperative Pulmonary Complications and in Decreasing the Negative Effects on Pulmonary Function in Patients Who Have Undergone CABG
      • Patients Treated with Incentive Spirometry Had Worse Pulmonary Function and Arterial Oxygenation, as Compared to Positive-Pressure Breathing Modalities (CPAP, BiPAP, IPPB)
      • In View of the Modest number of Patients Studied, Methodological Shortcomings and Poor Reporting of the Included Trials, These Results Should Be Interpreted Cautiously
    • Systematic Review of Incentive Spirometry in Decreasing Pulmonary Complications in Patients Who Have Undergone Upper Abdominal Surgery (Cochrane Database Syst Rev, 2014)[MEDLINE]: n = 12 studies (n = 1834 patients)
      • Low-Quality Evidence Regarding the Lack of Efficacy of Incentive Spirometry for the Prevention of Postoperative Pulmonary Complications in Patients Who Have Undergone Upper Abdominal Surgery
    • Trial of Incentive Spirometry in Decreasing Pulmonary Complications in Patients Who Have Undergone Laparotomy (JAMA Surg, 2015) [MEDLINE]
      • Education and Incentive Spirometry for Unmonitored Patient Use Does Not Result in Statistically Significant Improvement in Pulmonary Dynamics Following Laparotomy

Intermittent Positive-Pressure Breathing (IPPB) (see Intermittent Positive-Pressure Breathing)

  • Intermittent positive pressure breathing (IPPB) was used commonly in the 1960s and 1970s, but was associated with more complications than other methods of lung expansion and is not part of routine management
  • Clinical Efficacy
    • IPPB is of Limited or No Value as Prophylaxis Against Postoperative Pulmonary Complications (Pneumonia, Atelectasis), as a Means of Delivering Aerosol Medications, or as a Means of Treating Stable Chronic Obstructive Pulmonary Disease (Postgrad Med, 1976) [MEDLINE]

Early Post-Operative Ambulation

  • Indicated for Postoperative Prevention of Atelectasis

Epidural Anesthesia (see Epidural Anesthesia)

  • Use of Epidural Anesthesia (Instead of Intravenous Opiates) is Preferred, When Applicable

Avoid Nonsteroidal Anti-Inflammatory Drugs (NSAID’s) (Such as Ketorolac, Ibuprofen, etc) in Patients with Asthma and/or Aspirin-Exacerbated Respiratory Disease (see Asthma and Aspirin-Exacerbated Respiratory Disease)

  • These Agents May Exacerbate Underlying Respiratory Disease

Continuous Positive Airway Pressure (CPAP)

  • Technique
    • Nasal or Full Face Mask CPAP at 10 cm H2O for 4-6 hrs
  • Clinical Efficacy
    • CPAP May Decrease the Incidence of Hypoxemia, Pneumonia, Reintubation, and ICU Admission in High-Risk Patients
    • Early Use of CPAP Via Mask for 30 min q2hrs Had Better Outcomes to Re-Open Collapsed Alveoli After Cardiac Surgery than Incentive Spirometry (Saudi Med J, 2012) [MEDLINE]
    • Systematic Review of CPAP in Perioperative Setting for Major Abdominal Surgery (Cochrane Database Syst Rev, 2014) [MEDLINE]
      • Very low-quality evidence from this review suggests that CPAP initiated during the postoperative period might reduce postoperative atelectasis, pneumonia and reintubation
      • Effects on mortality, hypoxia, and invasive ventilation were uncertain
    • Study of Continuous Positive Airway Pressure to Prevent Postoperative Atelectasis in Anesthetized Children (Eur J Anaesthesiol., 2021) [MEDLINE]
      • Use of 5 cm H2O of CPAP in Healthy Children (Aged 6 mos-7 y/o) During Induction and Emergence of Anesthesia Prevented Atelectasis, with a Benefit Maintained During the First Postoperative Hour

Avoiding Nasogastric Tubes Use After Abdominal Surgery (Unless Required for Symptom Control (see Nasogastric-Orogastric Tube)

  • Clinical Efficacy
    • Systematic Review of Nasogastric Tube Use Following Abdominal Surgery (Cochrane Database Syst Rev, 2005) [MEDLINE]
      • Routine Nasogastric Tube Use Does Not Accomplish Any of its Intended Goals and Should Be Abandoned in Favor of Selective Nasogastric Tube Use (to Specifically Treat Abdominal Distension or Nausea)

Intermittent Positive Pressure Breathing (IPPB) (see Intermittent Positive Pressure Breathing)

General Comments

  • Unclear Clinical Benefit

Clinical Efficacy

  • IPPB is of Limited or No Value as Prophylaxis Against Postoperative Pulmonary Complications (Pneumonia, Atelectasis), as a Means of Delivering Aerosol Medications, or as a Means of Treating Stable Chronic Obstructive Pulmonary Disease (Postgrad Med, 1976) [MEDLINE]

Treatment

General Measures

  • Treat Underlying Infection (If Present)
    • Antibiotics, as Required
  • Treat Underlying Conditions Which Might Impede Secretion Clearance (If Present)
    • Neuromuscular Disease/Neurologic Impairment
  • Humidification
    • Helps to Humidify Mucous

Upright Body Position

Rationale

  • Since Recumbent Body Position Decreases FRC and Enhances the Development of Atelectasis, Upright Body Position (and Mobilization) is Generally Recommended

Clinical Efficacy

  • Body Positioning is Generally More Effective as a Prophylactic Therapy when Combined with an Effective Secretion-Mobilizing Modality (Respir Care, 2012) [MEDLINE] (Burns, 2013) [MEDLINE]

Bronchodilators

Indications

  • Bronchodilators are Indicated for Patients with Airflow Obstruction

Agents

Clinical Efficacy

  • Systematic Review of Pharmacologic Agents (N-Acetylcysteine, Heparin + N-Acetylcysteine, Albuterol, Ipratropium Bromide, and Saline) Which Promote Airway Clearance in Hospitalized Subjects (Respir Care, 2015) [MEDLINE]: n = 9 studies (5 randomized controlled trials, 3 crossover randomized controlled trials, and 1 retrospective cohort study)
    • Studies Reported No Benefit of the Studied Agents on Expectoration, Pulmonary Function, and Atelectasis (and Little Effect on Changes in Sputum Volume, Weight, or Viscosity)

Corticosteroids (see Corticosteroids)

Mechanical Secretion Clearance Modalities

Modalities

  • Chest Physical Therapy (CPT) (see Chest Physical Therapy)
    • Standard Therapeutic Modality with Extensive Clinical Experience (J Thorac Dis, 2017) [MEDLINE]
    • Small Randomized Prospective Study of Therapeutic Bronchoscopy vs Chest Physical Therapy in the Treatment of Acute Lobar Atelectasis (Am Rev Respir Dis, 1979) [MEDLINE]: n = 31
      • No Significant Differences Between the Groups with Regard to Restoration of Volume Loss After the First Treatment Intervention, at 24 hrs, or at 48 hrs (p > 0.20)
      • Presence of Air Bronchogram was a Predictor of Delayed Resolution in Both Groups
        • At 24 hrs, 26% of the Air Bronchograms Demonstrated 83% Resolution (p < 0.001)
    • Narrative Review of Chest Physical Therapy in Mechanically-Ventilated Patients without Pneumonia ( J Thorac Dis, 2017) [MEDLINE]
      • Chest Physical Therapy was Safe, But Had Debatable or No Significant Impact on Any Relevant Patient Outcome Parameter (Including Pneumonia
      • Current Evidence Does Not Support Prophylactic Chest Physical Therapy in Adult Mechanically-Ventilated Patients without Pneumonia
  • Flutter Valve (see Flutter Valve)
    • May Be Useful in Some Cases
  • High-Frequency Oscillation Respiratory Therapy (Vest) (see High-Frequency Oscillation Respiratory Therapy)
    • May Be Useful in Some Cases
  • Postural Drainage
    • May Be Useful in Some Cases
  • Therapeutic Bronchoscopy (see Bronchoscopy)
    • Indicated for Significant Mucous Plugging with Associated Atelectasis (Particularly in Cases with Associated Respiratory Failure)
    • Small Randomized Prospective Study of Therapeutic Bronchoscopy vs Chest Physical Therapy in the Treatment of Acute Lobar Atelectasis (Am Rev Respir Dis, 1979) [MEDLINE]: n = 31
      • No Significant Differences Between the Groups with Regard to Restoration of Volume Loss After the First Treatment Intervention, at 24 hrs, or at 48 hrs (p > 0.20)
      • Presence of Air Bronchogram was a Predictor of Delayed Resolution in Both Groups
        • At 24 hrs, 26% of the Air Bronchograms Demonstrated 83% Resolution (p < 0.001)

RTX Respirator

Device

  • Biphasic External Cuirass-Style Ventilator

Clinical Efficacy

  • May Be Useful in Subset of Elderly Patients with Sputum Retention (Intern Med, 2009) [MEDLINE]

Mechanical Insufflation-Exsufflation Device (Cough Assist Device) (see Mechanical Insufflation-Exsufflation Device)

Indications

MetaNeb (see MetaNeb)

  • Clinical Efficacy
    • Retrospective Pilot Study of Intrapulmonary Percussive Ventilation in On-Ventilated Critically Ill Patients (J Intensive Care Soc, 2021) [MEDLINE]
      • Application of intrapulmonary percussive ventilation intervention was feasible and safe in non-ventilated adult patients in critical care

Mucoactive Agents

Dornase Alfa (Pulmozyme) (see DNase)

  • Pharmacology
    • DNase
  • Clinical Efficacy
    • Retrospective Descriptive Study of the Effect of DNase on Atelectasis in Non-Cystic Fibrosis Pediatric Patients (Crit Care, 2005) [MEDLINE]
      • After Treatment with DNase for Atelectasis of Presumably Infectious Origin in Non-Cystic Fibrosis Pediatric Patients, Clinical Improvement was Observed within 2 hrs and Radiologic Improvement was Documented within 24 hrs in the Large Majority of Children
      • Increased Airway Obstruction and Ventilation-Perfusion Mismatch Occurred in 3 Children (Possibly Due to Rapid Mobilisation of Mucous)
    • Small Randomized Trial of Dornase Alfa vs Hypertonic Saline for the Treatment of Atelectasis in Mechanically-Ventilated Critically Ill Patients (J Aer Med Pulm Drug Del, 2012) [MEDLINE]: n = 33
      • No Significant Difference Between Dornase Alfa and Normal Saline (in Terms of Chest X-Ray Atelectasis Score)
      • No Significant Difference Between Hypertonic Saline and Normal Saline (in Terms of Chest X-Ray Atelectasis Score)
    • Australian Systematic Review of Inhaled Mucoactive Agents (Dornase Alfa, N-Acetylcysteine, Ambroxol, Hypertonic Saline, Heparin, Mannitol, and Isotonic Saline) in Critically Ill Medical/Surgical/Trauma Inpatients with Acute Lung Disease (Heart Lung, 2019) [MEDLINE]: n = 227 full-text articles were reviewed (of which 10 trials were included)
      • No Adverse Events were Reported for Dornase Alfa (n = 63), N-Acetylcysteine (N-Acetylcysteine, n = 50), Ambroxol (n = 140), Hypertonic Saline (n = 33), Heparin (n = 384), Mannitol (n = 20), or Isotonic Saline
      • During Invasive Mechanical Ventilation, N-Acetylcysteine, Dornase Alfa and Saline Had No Effect on Mucous
      • Postoperatively, Mucous Characteristics Improved with N-Acetylcysteine (n = 10)
      • Ambroxol Decrease Length of Stay (Mean Difference: 4 Days) and Halved Complications Following Lung Carcinoma Resection (n = 140)*
      • Heparin Improved Ventilator-Free Days (n = 130, Mean Difference 3.9-4.6 Days) and Intensive Care Length of Stay (n = 223, 3.2 Days), But Not Ventilator-Acquired Pneumonia
      • Dornase Alfa, Hypertonic Saline, and N-Acetylcysteine were Ineffective for Atelectasis/Mucous Plugging While Intubated
      • More Data are Required to Support Using N-Acetylcysteine, Ambroxol, and Heparin During Acute Illness

Guaifenesin (Mucinex) (see Guaifenesin)

  • History
    • Guaifenesin Has Been Used Medically Since at Least 1933
  • Pharmacology
    • Expectorant Which Increases the Volume and Decreases the Viscosity of Secretions in the Trachea and Bronchi

Nebulized Hypertonic Saline (see Hypertonic Saline)

  • Pharmacology
    • Induction of Osmotic Flow of Water into the Mucous Layer, Rehydrating the Airway Surface Liquid and Improving Mucociliary Clearance (J R Soc Med, 2011) [MEDLINE]
    • Decreases Airway Edema by Enhancing the Absorption of Water from the Mucosa and Submucosa
    • Disruption of Ionic Bonds within the Mucous Gel, Which Could Decrease Cross-Linking and Entanglements (J R Soc Med, 2011) [MEDLINE]
    • Dissociates DNA from the Mucoprotein, Which Allows Natural Proteolytic Enzymes to then Digest the Mucoprotein (J R Soc Med, 2011) [MEDLINE]
    • Triggers Cough (J R Soc Med, 2011) [MEDLINE]
    • Decreases Pseudomonas Aeruginosa Biofilms (J R Soc Med, 2011) [MEDLINE]
    • Increase the Levels of the Antioxidants, Glutathione and Thiocyanate, in the Airway Surface Liquid (J R Soc Med, 2011) [MEDLINE]
  • Clinical Efficacy
    • Small Randomized Trial of Dornase Alfa vs Hypertonic Saline for the Treatment of Atelectasis in Mechanically-Ventilated Critically Ill Patients (J Aer Med Pulm Drug Del, 2012) [MEDLINE]: n = 33
      • No Significant Difference Between Dornase Alfa and Normal Saline (in Terms of Chest X-Ray Atelectasis Score)
      • No Significant Difference Between Hypertonic Saline and Normal Saline (in Terms of Chest X-Ray Atelectasis Score)

Nebulized N-Acetlycysteine (Mucomyst) (see N-Acetylcysteine)

  • Pharmacology
    • N-Acetylcysteine Liquefies Mucous and DNA Via Disruption of Disulfide Bonds
    • N-Acetylcysteine Has Antioxidant Effects (When Used at an Adequate Dose)
  • Clinical Efficacy
    • Systematic Review of Pharmacologic Agents (N-Acetylcysteine, Heparin + N-Acetylcysteine, Albuterol, Ipratropium Bromide, and Saline) Which Promote Airway Clearance in Hospitalized Subjects (Respir Care, 2015) [MEDLINE]: n = 9 studies (5 randomized controlled trials, 3 crossover randomized controlled trials, and 1 retrospective cohort study)
      • Studies Reported No Benefit of the Studied Agents on Expectoration, Pulmonary Function, and Atelectasis (and Little Effect on Changes in Sputum Volume, Weight, or Viscosity)
    • Australian Systematic Review of Inhaled Mucoactive Agents (Dornase Alfa, N-Acetylcysteine, Ambroxol, Hypertonic Saline, Heparin, Mannitol, and Isotonic Saline) in Critically Ill Medical/Surgical/Trauma Inpatients with Acute Lung Disease (Heart Lung, 2019) [MEDLINE]: n = 227 full-text articles were reviewed (of which 10 trials were included)
      • No Adverse Events were Reported for Dornase Alfa (n = 63), N-Acetylcysteine (N-Acetylcysteine, n = 50), Ambroxol (n = 140), Hypertonic Saline (n = 33), Heparin (n = 384), Mannitol (n = 20), or Isotonic Saline
      • During Invasive Mechanical Ventilation, N-Acetylcysteine, Dornase Alfa and Saline Had No Effect on Mucous
      • Postoperatively, Mucous Characteristics Improved with N-Acetylcysteine (n = 10)
      • Ambroxol Decrease Length of Stay (Mean Difference: 4 Days) and Halved Complications Following Lung Carcinoma Resection (n = 140)
      • Heparin Improved Ventilator-Free Days (n = 130, Mean Difference 3.9-4.6 Days) and Intensive Care Length of Stay (n = 223, 3.2 Days), But Not Ventilator-Acquired Pneumonia
      • Dornase Alfa, Hypertonic Saline, and N-Acetylcysteine were Ineffective for Atelectasis/Mucous Plugging While Intubated
      • More Data are Required to Support Using N-Acetylcysteine, Ambroxol, and Heparin During Acute Illness
    • Expert Review of Mucoactive Agents in Acutely Ill Patients (Expert Rev Respir Med, 2017) [MEDLINE]
      • In the Non-Cystic Fibrosis Patient Population, there is Limited Evidence Regarding these Medications
      • While Some Studies Have Found Benefit, the Quality of Evidence is Low
      • While Certain Patients May Derive Benefit, the General Use of these Medications in Acutely Ill Patients without Cystic Fibrosis Cannot Be Recommended at This Time
    • Substudy of Routine vs On-Demand Nebulization of N-Acetylcysteine with Salbutamol on the Accumulation of Airway Secretions in Endotracheal Tubes (Substudy of the NEBULAE Trial) (Intensive Care Med Exp, 2020) [MEDLINE]
      • In Adult Critically Ill Patients on Invasive Ventilation, Routine Nebulization of Mucolytics and Bronchodilators Did Not Affect Accumulation of Airway Secretions in the Endotracheal Tube

Strategies to Manage Atelectasis in Mechanically-Ventilated Patients (see Mechanical Ventilation-General)

  • Utilization of Positive End-Expiratory Pressure (PEEP)
    • Study of Transpulmonary Pressure and Positive End-Expiratory Pressure in Morbidly Obese Patients (BMI 48 ± 11 kg/m2) (Crit Care Med, 2017) [MEDLINE]
      • In Morbid Obesity, Low-to-Negative Transpulmonary Pressures Predict Lung Collapse and Intratidal Recruitment/Derecruitment
      • After the Development of Atelectasis, Lung Recruitment Followed by a Decremental PEEP Trial Identified the PEEP Level (17.4 ± 2.1 cm H2O) Required to Restore Nonaerated Lung Tissue and Reestablish Lung Elastance and Oxygenation (While Avoiding Increased Pulmonary Vascular Resistance)

AARC Guideline for Pharmacologic Airway Clearance Therapies in Hospitalized Patients (Respir Care, 2015) [MEDLINE]

Hospitalized Adult and Pediatric Patients Without Cystic Fibrosis

  • Dornase Alfa is Not Recommended in Adults and Children with Non-Cystic Fibrosis Bronchiectasis
  • Routine Use of Bronchodilators to Aid in Secretion Clearance is Not Recommended
  • Routine Use of Aerosolized N-Acetylcysteine to Improve Airway Clearance is Not Recommended

Adult and Pediatric Patients With Neuromuscular Disease, Respiratory Muscle Weakness, or Impaired Cough

  • Due to Insufficient Evidence, Use of Aerosolized Agents to Change Sputum Physical Properties or Improve Airway Clearance is Not Recommended for Patients with Neuromuscular Disease or Weakness

Postoperative Adult and Pediatric Patients

  • Due to Insufficient Evidence, Mucolytics are Not Recommended in the Treatment of Atelectasis
  • Routine Administration of Bronchodilators to Postoperative Patients is Not Recommended

Prognosis/Complications

Complications of Re-Expansion of Atelectatic Lobe

  • Re-Expansion Pulmonary Edema May Occur Following Reinflation of a Long-Collapsed and Surfactant-Depleted Lung Lobe (J Appl Physiol Respir Environ Exerc Physiol, 1979) [MEDLINE] (Ann Thorac Cardiovasc Surg, 2008) [MEDLINE]

References

  • Effects of age and body position on “airway closure” in man. J Appl Physiol. 1970;28(4):448-451 [MEDLINE]
  • Effects of respiratory paralysis in tetraplegic and paraplegic patients. Scand J Rehab Med. 1971;3(4):145-150 [MEDLINE]
  • Intermittent positive-pressure breathing. A critical appraisal. Postgrad Med. 1976 May;59(5):103-7. doi: 10.1080/00325481.1976.11714357 [MEDLINE]
  • Postoperative impairment of mucous transport in the lung. Am Rev Respir Dis. 1976;114(4):673-679 [MEDLINE]
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