Medical School · Year 3 · Emergency Medicine · includes a quiz and discussion video

Seminar 03: Respiratory Emergencies

Year 3: Emergency Medicine Clerkship

Learning Objectives

By the end of this seminar, students will be able to:

1. Manage acute asthma and COPD exacerbations
2. Diagnose and treat pulmonary embolism
3. Recognize and manage pneumothorax
4. Apply non-invasive ventilation appropriately
5. Perform rapid sequence intubation
6. Identify patients with impending respiratory failure

Seminar Outline

I. Assessment of Respiratory Distress

The clinical evaluation of respiratory distress begins with rapid visual assessment of the patient's overall appearance, work of breathing, and air exchange quality before any formal measurement or examination occurs. Patients in severe distress often assume tripod positioning with hands on knees and shoulders elevated to maximize accessory muscle recruitment, while those unable to speak in complete sentences demonstrate critically limited respiratory reserve. Tachypnea with respiratory rates exceeding twenty-two breaths per minute, nasal flaring, intercostal and supraclavicular retractions, and paradoxical abdominal breathing patterns indicate escalating respiratory effort. The patient who can speak in full sentences generally has adequate respiratory reserve, while speech limited to phrases or single words signals progressive deterioration requiring urgent intervention.

Signs of impending respiratory failure demand immediate recognition and preparation for advanced airway management to prevent catastrophic decompensation. Fatigue manifesting as decreasing respiratory effort despite ongoing distress indicates exhaustion of compensatory mechanisms rather than clinical improvement. The paradox of apparent normalization of respiratory rate in a previously tachypneic patient may actually represent dangerous fatigue rather than therapeutic response. Altered mental status ranging from agitation suggesting hypoxia to somnolence indicating hypercapnia signals critical gas exchange failure. The silent chest in an asthmatic or COPD patient represents minimal air movement rather than bronchospasm resolution and constitutes an ominous finding demanding immediate intervention.

Diagnostic evaluation quantifies the severity of respiratory compromise and helps identify the underlying etiology guiding treatment selection. Continuous pulse oximetry monitoring provides real-time oxygen saturation data, though understanding its limitations including delayed response to acute changes and unreliability in poor perfusion states prevents overreliance on a single parameter. Arterial or venous blood gas analysis reveals pH, carbon dioxide tension, and oxygenation status that pulse oximetry cannot assess, with respiratory acidosis indicating ventilatory failure requiring mechanical support. Chest radiography identifies infiltrates suggesting pneumonia, pneumothorax requiring procedural intervention, and pulmonary edema amenable to diuresis. Point-of-care ultrasound has emerged as an invaluable bedside tool, with lung sliding excluding pneumothorax and B-lines indicating interstitial edema.

Oxygen delivery device selection matches the degree of hypoxemia with appropriate flow rates and FiO2 delivery capabilities to achieve target saturations. Nasal cannula delivering one to six liters per minute provides approximately twenty-four to forty percent FiO2 and suffices for mild hypoxemia. Simple face masks at six to ten liters per minute deliver thirty-five to fifty percent FiO2 for moderate hypoxemia. Non-rebreather masks with reservoir bags at ten to fifteen liters per minute achieve sixty to ninety percent FiO2 for severe hypoxemia. High-flow nasal cannula represents a significant advancement, delivering up to sixty liters per minute of heated humidified oxygen at precise FiO2 up to one hundred percent while providing mild positive pressure support. Bag-valve-mask ventilation with reservoir at fifteen liters per minute delivers near one hundred percent FiO2 and provides active ventilatory support.

<image>Panel A: Visual signs of respiratory distress showing accessory muscle use, tripod positioning, nasal flaring, and intercostal retractions. Panel B: Signs of impending respiratory failure including fatigue, silent chest, altered mental status, and cyanosis with clinical significance. Panel C: Diagnostic evaluation algorithm incorporating pulse oximetry, blood gas analysis, chest radiography, and point-of-care ultrasound. Panel D: Oxygen delivery devices comparison showing nasal cannula through high-flow nasal cannula with flow rates and FiO2 ranges.</image>

II. Asthma Exacerbation

Asthma exacerbation results from bronchial smooth muscle constriction, mucosal inflammation, and mucus hypersecretion causing airflow obstruction that manifests as wheezing, dyspnea, chest tightness, and cough with variable severity. Triggers include viral respiratory infections representing the most common precipitant, allergen exposure, exercise, cold air, environmental irritants, and medication effects from beta-blockers or aspirin in sensitive individuals. Severity assessment incorporates symptom intensity, ability to speak in sentences versus phrases versus words, accessory muscle use, and objective parameters including peak flow and oxygen saturation. Peak expiratory flow provides objective measurement with values above seventy percent of predicted indicating mild exacerbation, forty to sixty-nine percent indicating moderate severity, and below forty percent signifying severe obstruction requiring aggressive intervention.

Initial treatment focuses on bronchodilation and systemic anti-inflammatory therapy delivered simultaneously to reverse the pathophysiologic processes causing airway obstruction. Inhaled short-acting beta-agonists constitute first-line treatment, with albuterol delivered via nebulizer continuously or via metered-dose inhaler with spacer at four to eight puffs every twenty minutes during severe exacerbations. Ipratropium bromide at zero point five milligrams added to albuterol provides anticholinergic bronchodilation through complementary mechanisms, with evidence supporting improved outcomes when added to beta-agonists in the first hour of severe exacerbation treatment. Systemic corticosteroids including oral prednisone forty to sixty milligrams or intravenous methylprednisolone one hundred twenty-five milligrams reduce airway inflammation and should be administered within the first hour regardless of apparent response to bronchodilators. Supplemental oxygen targets saturation of ninety-two to ninety-five percent.

Adjunctive therapies become important when standard treatment produces inadequate response or when severe exacerbation presents with impending respiratory failure. Magnesium sulfate two grams intravenously over twenty minutes relaxes bronchial smooth muscle and provides benefit in severe exacerbations not responding adequately to initial therapy. Intramuscular or subcutaneous epinephrine at zero point three to zero point five milligrams offers systemic beta-agonist effect when inhaled medication cannot effectively reach distal airways due to severe obstruction. Non-invasive positive pressure ventilation with BiPAP can support the exhausted patient while other therapies take effect, potentially avoiding intubation in carefully selected patients who can protect their airway and cooperate with treatment. Ketamine provides bronchodilation in addition to sedation, making it an attractive choice when intubation becomes necessary.

Disposition decisions depend on response to emergency department treatment assessed through serial peak flow measurements, symptom resolution, and sustained improvement over an observation period. Good response with peak flow above seventy percent of predicted, minimal symptoms, and stable oxygen saturation generally supports discharge with oral corticosteroids for five days and arranged follow-up. Incomplete response despite aggressive treatment suggests need for observation or inpatient admission for continued bronchodilator therapy and monitoring. Severe exacerbations requiring continuous nebulization, those with persistent hypoxia, or patients with concerning features such as prior intubation warrant intensive care admission. Intubation represents a last resort given the challenges of mechanical ventilation in severe asthma, but respiratory failure mandates definitive airway management.

<image>Panel A: Asthma severity classification based on speech ability, peak flow percentage, oxygen saturation, and clinical examination findings. Panel B: Initial treatment protocol showing continuous albuterol, ipratropium, corticosteroids, and oxygen with timing and dosing. Panel C: Adjunctive therapy indications including magnesium sulfate, epinephrine, BiPAP, and ketamine for refractory severe exacerbations. Panel D: Disposition algorithm stratifying patients by treatment response into discharge, observation, admission, and ICU pathways.</image>

III. COPD Exacerbation

Chronic obstructive pulmonary disease exacerbation is defined by acute worsening of respiratory symptoms beyond normal day-to-day variation requiring change in medication, typically manifesting as increased dyspnea, increased sputum volume, or increased sputum purulence. The underlying pathophysiology involves chronic airflow limitation from bronchitis and emphysema with superimposed acute triggers that overwhelm the patient's limited respiratory reserve. Infection represents the most common identifiable trigger, with both viral and bacterial pathogens implicated, while environmental pollution, temperature changes, and medication non-adherence contribute to remaining cases. Arterial blood gas analysis proves particularly important in COPD patients, who may have chronic hypercapnia making acute-on-chronic respiratory failure interpretation more complex, with pH rather than absolute PCO2 level guiding management intensity.

Treatment parallels asthma management with important differences reflecting the distinct underlying pathophysiology and chronicity of COPD. Short-acting bronchodilators including both beta-agonists and anticholinergics form the foundation of treatment, with nebulized albuterol and ipratropium administered together providing greater bronchodilation than either alone. Systemic corticosteroids reduce inflammation and accelerate recovery, with oral prednisone forty milligrams daily for five days proving equivalent to longer courses and avoiding unnecessary steroid exposure. Controlled oxygen supplementation targeting saturation of eighty-eight to ninety-two percent prevents hypoxia while avoiding suppression of hypoxic respiratory drive in patients dependent on hypoxia for ventilatory stimulus, though correcting life-threatening hypoxia takes precedence over theoretical concerns about oxygen-induced hypercapnia.

Antibiotic therapy in COPD exacerbation targets common respiratory pathogens when clinical features suggest bacterial infection requiring antimicrobial treatment. Indications for antibiotics include increased sputum purulence accompanying increased dyspnea or sputum volume, with strongest evidence supporting treatment when all three cardinal symptoms are present. Outpatient regimens include azithromycin or doxycycline covering typical respiratory pathogens including Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis. Inpatients may receive respiratory fluoroquinolones such as levofloxacin or moxifloxacin providing broader coverage including atypical organisms. Treatment duration of five to seven days generally suffices, with longer courses not demonstrating additional benefit.

Non-invasive positive pressure ventilation has transformed COPD exacerbation management by reducing intubation rates, mortality, and hospital length of stay when applied to appropriate candidates with hypercapnic respiratory failure. Indications include respiratory acidosis with pH below 7.35 and PCO2 above forty-five millimeters of mercury despite initial treatment, severe dyspnea with accessory muscle use, or persistent hypoxia despite supplemental oxygen. BiPAP with typical starting settings of inspiratory pressure ten centimeters of water and expiratory pressure five centimeters of water reduces work of breathing and assists carbon dioxide elimination. Contraindications include respiratory arrest, altered mental status preventing airway protection, inability to clear secretions, hemodynamic instability, and facial deformity preventing mask seal. Response should be assessed with repeat blood gas at one to two hours, with failure to improve indicating need for intubation.

<image>Panel A: COPD exacerbation diagnosis showing cardinal symptoms of increased dyspnea, sputum volume, and sputum purulence with common triggers. Panel B: Treatment components comparing bronchodilator, corticosteroid, and oxygen therapy approaches with specific dosing. Panel C: Antibiotic selection criteria and regimens for outpatient versus inpatient management with drug choices. Panel D: BiPAP indications, settings, contraindications, and assessment of response with criteria for intubation.</image>

IV. Pulmonary Embolism

Pulmonary embolism represents a common, potentially fatal condition that demands systematic evaluation because its protean manifestations overlap extensively with other causes of dyspnea and chest pain. The classic presentation includes sudden onset dyspnea, pleuritic chest pain, and hemoptysis, though this complete triad appears in only a minority of cases, with many patients presenting with isolated dyspnea, syncope, or nonspecific symptoms. Risk factors for venous thromboembolism include immobilization, recent surgery especially orthopedic procedures, active malignancy, pregnancy and postpartum state, estrogen therapy, prior VTE, and inherited thrombophilias such as Factor V Leiden mutation. Clinical suspicion should be heightened when hypoxia exceeds that expected from examination findings, when tachycardia appears disproportionate to clinical context, or when chest radiograph appears unexpectedly normal despite significant respiratory symptoms.

Clinical decision rules standardize PE probability assessment and guide appropriate testing strategies to avoid both missed diagnoses and unnecessary imaging. The Wells criteria for PE incorporate clinical signs of DVT, heart rate above one hundred, immobilization or surgery within four weeks, prior VTE, hemoptysis, active malignancy, and clinical judgment that PE is more likely than alternative diagnosis, generating scores that categorize patients as low, moderate, or high probability. The PERC rule identifies very low-risk patients in whom D-dimer testing itself is unnecessary, requiring absence of all eight criteria: age over fifty, heart rate over one hundred, oxygen saturation below ninety-five percent, hemoptysis, estrogen use, prior VTE, unilateral leg swelling, and surgery or trauma within four weeks. Low-probability patients who are PERC-negative require no further testing, while moderate-probability patients undergo D-dimer testing with negative results excluding PE and positive results prompting CT angiography.

CT pulmonary angiography has become the diagnostic standard for PE, offering high sensitivity and specificity while providing alternative diagnoses when PE is excluded. Direct visualization of intraluminal filling defects within pulmonary arteries establishes the diagnosis, with extent and location of clot burden informing prognosis and management decisions. Right ventricular enlargement on CT, indicated by RV to LV diameter ratio exceeding one, suggests right heart strain that correlates with increased mortality even in hemodynamically stable patients. Ventilation-perfusion scanning remains an alternative when CT angiography is contraindicated due to contrast allergy, severe renal insufficiency, or pregnancy, with high-probability scans diagnostic and normal scans effectively excluding clinically significant PE.

Treatment of hemodynamically stable PE centers on anticoagulation to prevent clot propagation while endogenous fibrinolysis gradually resolves existing thrombus over weeks to months. Direct oral anticoagulants including rivaroxaban and apixaban have largely replaced warfarin for outpatient management, offering fixed dosing without monitoring requirements. Low-molecular-weight heparin provides immediate anticoagulation when oral agents are unsuitable or as bridge therapy. Massive PE with hemodynamic instability characterized by hypotension, altered mental status, or cardiac arrest warrants systemic thrombolysis with alteplase one hundred milligrams over two hours, accepting increased bleeding risk given high mortality of untreated massive PE. Submassive PE with right ventricular strain but maintained blood pressure presents a therapeutic dilemma, with thrombolysis considered on case-by-case basis balancing bleeding risk against potential benefit. Catheter-directed therapy and surgical embolectomy provide alternatives when systemic thrombolysis is contraindicated or fails.

<image>Panel A: Pulmonary embolism presentation spectrum from classic symptoms through atypical presentations with risk factors increasing clinical suspicion. Panel B: Clinical decision rule application showing Wells criteria scoring and PERC rule evaluation with diagnostic algorithm. Panel C: CT pulmonary angiography interpretation showing intraluminal filling defects and right ventricular strain indicators. Panel D: Treatment stratification from anticoagulation for stable PE through thrombolysis for massive PE with hemodynamic instability.</image>

V. Pneumothorax

Pneumothorax results from air accumulation in the pleural space causing partial or complete lung collapse, with classification into spontaneous, traumatic, and iatrogenic categories that influence clinical presentation and management approach. Primary spontaneous pneumothorax occurs in patients without underlying lung disease, typically tall, thin young males, often associated with apical blebs that rupture without obvious precipitant. Secondary spontaneous pneumothorax complicates COPD, cystic fibrosis, and other parenchymal lung diseases, carrying higher morbidity due to limited respiratory reserve in patients with already compromised pulmonary function. Traumatic pneumothorax follows both penetrating and blunt chest injury, while iatrogenic pneumothorax complicates central venous catheterization, thoracentesis, mechanical ventilation, and lung biopsy procedures.

Clinical presentation varies with pneumothorax size, rate of development, and underlying cardiopulmonary reserve, ranging from asymptomatic incidental discovery to life-threatening cardiopulmonary compromise. Typical symptoms include sudden onset pleuritic chest pain and dyspnea, with examination revealing decreased breath sounds and hyperresonance to percussion on the affected side. Tracheal deviation toward the contralateral side represents a late finding of tension physiology rather than an early diagnostic sign. Diagnosis is confirmed by chest radiograph demonstrating visible pleural line with absent lung markings peripherally, optimally visualized on expiratory films that maximize the contrast between collapsed lung and surrounding air. Point-of-care ultrasound showing absent lung sliding provides rapid bedside diagnosis in unstable patients, offering superior sensitivity to chest radiograph while allowing immediate assessment without transport delays.

Tension pneumothorax represents a clinical diagnosis requiring immediate intervention without waiting for radiographic confirmation, as the one-way valve effect causes progressive accumulation of pleural air with mediastinal shift, impaired venous return, and cardiovascular collapse. Clinical features include severe respiratory distress, hypotension, tachycardia, distended neck veins from obstructed venous return, absent breath sounds unilaterally, and tracheal deviation away from the affected side appearing as a late finding. Needle decompression using a fourteen-gauge angiocatheter inserted above the rib at the second intercostal space midclavicular line or at the fourth to fifth intercostal space anterior axillary line provides immediate temporizing relief evidenced by rush of escaping air and clinical improvement. Tube thoracostomy must follow needle decompression to provide definitive treatment, as the needle merely converts tension to simple pneumothorax.

Management of non-tension pneumothorax depends on size, symptoms, underlying lung disease, and anticipated need for positive pressure ventilation. Small primary spontaneous pneumothorax in stable patients, typically defined as less than two centimeters apex-to-cupola distance, may be managed conservatively with observation, supplemental oxygen to accelerate resorption, and repeat imaging to confirm resolution. Large or symptomatic pneumothoraces require intervention, with options including simple aspiration through small-bore catheter, pigtail catheter drainage, or traditional tube thoracostomy inserted at the fourth to fifth intercostal space anterior-midaxillary line in the triangle of safety. Secondary spontaneous pneumothorax generally requires tube drainage due to limited respiratory reserve. All patients requiring positive pressure ventilation need tube thoracostomy before or immediately upon intubation given high risk of tension physiology development with positive pressure.

<image>Panel A: Pneumothorax classification showing primary spontaneous, secondary spontaneous, traumatic, and iatrogenic categories with typical patient profiles. Panel B: Clinical presentation and diagnostic findings including chest radiograph appearance and ultrasound findings with absent lung sliding. Panel C: Tension pneumothorax recognition and needle decompression technique showing anatomic landmarks at midclavicular and anterior axillary sites. Panel D: Management algorithm for non-tension pneumothorax stratified by size and underlying lung disease.</image>

VI. Non-Invasive Ventilation

Non-invasive positive pressure ventilation delivers mechanical ventilatory support through a mask interface without endotracheal intubation, providing respiratory support while avoiding intubation-associated complications when applied to appropriate candidates. The two primary modes include continuous positive airway pressure providing single constant pressure throughout the respiratory cycle primarily addressing oxygenation through alveolar recruitment and preload reduction, and bilevel positive airway pressure adding inspiratory pressure support above the expiratory baseline to augment tidal volume and directly assist ventilation. CPAP proves most beneficial for cardiogenic pulmonary edema where preload and afterload reduction combined with alveolar recruitment dramatically improves both hemodynamics and gas exchange. BiPAP addresses hypercapnic respiratory failure in COPD exacerbation by reducing work of breathing and augmenting minute ventilation.

Evidence strongly supports NIPPV for specific conditions where appropriate application reduces intubation rates, mortality, and hospital length of stay compared to conventional oxygen therapy. COPD exacerbation with respiratory acidosis represents the strongest indication, with BiPAP reducing intubation by approximately fifty percent in appropriately selected patients. Cardiogenic pulmonary edema responds rapidly to CPAP or BiPAP, with improved hemodynamics and oxygenation often apparent within minutes of initiation. Immunocompromised patients with respiratory failure benefit from avoiding intubation-associated infection risk, making NIPPV particularly valuable in this population when feasible. Post-extubation respiratory distress in selected patients may respond to NIPPV, potentially preventing reintubation.

Contraindications to NIPPV identify patients in whom mask ventilation poses unacceptable risk or cannot provide adequate support, mandating alternative approaches. Cardiac or respiratory arrest requires definitive airway management rather than mask ventilation. Altered mental status preventing airway protection or cooperation with treatment creates aspiration risk that outweighs NIPPV benefits. Facial trauma, burns, or surgery preventing adequate mask seal precludes effective positive pressure delivery. Hemodynamic instability requiring vasopressors suggests severity beyond what NIPPV can address. Active vomiting or high aspiration risk, copious secretions overwhelming clearance capacity, and recent upper gastrointestinal surgery creating leak concerns represent additional contraindications. The presence of multiple relative contraindications may collectively argue against NIPPV trial.

Monitoring during NIPPV and timely recognition of failure prevent catastrophic deterioration in patients not responding to non-invasive support. Comfort assessment and mask adjustment improve tolerance, as claustrophobia and air leak represent common challenges to successful NIPPV. Clinical improvement should be apparent within one to two hours, with decreased respiratory rate, reduced accessory muscle use, and improved oxygen saturation indicating success. Arterial blood gas at one to two hours objectively assesses response, with improving pH and decreasing PCO2 confirming effective treatment. Failure indicators demanding transition to intubation include worsening respiratory acidosis despite pressure adjustments, declining mental status, hemodynamic instability, inability to clear secretions, and lack of clinical improvement. Delayed intubation after clear NIPPV failure worsens outcomes compared to timely recognition that invasive ventilation is required.

<image>Panel A: NIPPV modes comparing CPAP single-pressure effect with BiPAP inspiratory and expiratory pressure support mechanisms. Panel B: Evidence-based indications showing COPD exacerbation, cardiogenic pulmonary edema, and immunocompromised respiratory failure. Panel C: Contraindications to NIPPV including arrest, altered mental status, facial trauma, and hemodynamic instability. Panel D: Monitoring parameters and failure recognition with criteria for transitioning to invasive ventilation.</image>

VII. Airway Management

Indications for emergency endotracheal intubation encompass failure of oxygenation despite maximal supplemental oxygen, failure of ventilation with hypercapnia causing respiratory acidosis, failure to protect the airway from aspiration or maintain patency, and anticipated clinical course requiring prophylactic airway control before deterioration occurs. The decision to intubate represents clinical judgment integrating multiple factors rather than single threshold values, though objective parameters including oxygen saturation below ninety percent despite high-flow oxygen, respiratory rate above thirty-five or below eight, rising PCO2 with acidosis, and GCS below eight provide supporting evidence. The trajectory of illness often proves more important than absolute values, with rapid deterioration mandating earlier intervention than slowly progressive abnormalities allowing additional therapeutic trials.

Preparation for emergency intubation follows systematic frameworks ensuring all necessary equipment and medications are immediately available and functioning before induction. The classic approach addresses equipment including laryngoscope with functioning light and appropriate blade, endotracheal tubes of multiple sizes with cuff tested, stylet, suction, bag-valve-mask with reservoir, and backup airway devices including supraglottic airways and surgical airway equipment. Preoxygenation using non-rebreather mask or high-flow nasal cannula for three to five minutes washes nitrogen from functional residual capacity, creating an oxygen reservoir that extends safe apnea time during laryngoscopy. Monitoring with pulse oximetry, continuous capnography, and cardiac monitor allows real-time assessment throughout the procedure. The difficult airway assessment using LEMON criteria evaluates external appearance, mouth opening per the 3-3-2 rule, Mallampati score, airway obstruction, and neck mobility to identify patients at increased intubation difficulty.

Rapid sequence intubation represents the standard approach for emergency intubation in patients with intact reflexes, using medication-assisted paralysis to optimize laryngoscopy conditions while minimizing aspiration risk through continuous cricoid pressure and rapid sequence technique without intervening bag-mask ventilation. Induction agents include etomidate at zero point three milligrams per kilogram offering hemodynamic stability but adrenal suppression concerns, ketamine at one to two milligrams per kilogram providing bronchodilation and maintained blood pressure ideal for asthma and hypotensive patients, and propofol at one to two milligrams per kilogram causing hypotension limiting its use in shock states. Neuromuscular blockade follows immediately with succinylcholine at one point five milligrams per kilogram providing rapid onset and short duration but contraindicated in hyperkalemia and neuromuscular disease, or rocuronium at one point two milligrams per kilogram offering comparable onset without succinylcholine contraindications but longer duration.

Confirmation of correct endotracheal tube placement requires multiple modalities to prevent unrecognized esophageal intubation, a catastrophic error causing hypoxic death if not immediately identified and corrected. End-tidal carbon dioxide detection represents the gold standard, with sustained waveform capnography over multiple breaths confirming tracheal placement, as esophageal intubation produces minimal or absent CO2. Direct visualization of the tube passing between the vocal cords provides initial confirmation but does not exclude subsequent displacement. Auscultation for bilateral breath sounds and absence of gastric insufflation supplements but does not replace capnography. Chest radiograph confirms depth of insertion with tip ideally two to four centimeters above the carina but does not distinguish tracheal from esophageal placement. Absent capnography waveform mandates immediate removal and reoxygenation regardless of other findings.

<image>Panel A: Intubation indications showing oxygenation failure, ventilation failure, airway protection, and anticipated deterioration with supporting parameters. Panel B: Preparation checklist including equipment, preoxygenation, monitoring, and LEMON difficult airway assessment. Panel C: Rapid sequence intubation medications comparing induction agents and neuromuscular blocking agents with dosing and contraindications. Panel D: Intubation confirmation hierarchy showing capnography as gold standard supplemented by visualization, auscultation, and radiography.</image>

VIII. Post-Intubation Care

Confirmation of proper endotracheal tube placement extends beyond initial verification to include documentation of tube depth at the lip, chest radiograph assessment of position relative to the carina, and establishment of procedures preventing inadvertent displacement. The tube should be secured with commercial holder or tape at a documented lip level, typically twenty-one centimeters for adult females and twenty-three centimeters for adult males, providing reference for subsequent position checks. Chest radiograph confirms tip position ideally two to four centimeters above the carina, with right mainstem intubation the most common malposition requiring tube withdrawal. Continuous capnography monitoring provides real-time confirmation that the tube remains correctly positioned, with sudden waveform loss indicating displacement or obstruction demanding immediate assessment.

Initial ventilator settings provide baseline respiratory support while blood gas results guide subsequent adjustments toward individualized targets. Assist-control mode guarantees a minimum number of breaths while allowing patient triggering of additional supported breaths. Tidal volume of six to eight milliliters per kilogram of ideal body weight, calculated from height rather than actual weight, provides adequate ventilation while limiting barotrauma and volutrauma. Respiratory rate of fourteen to sixteen breaths per minute generates initial minute ventilation, adjusted based on pH and PCO2 goals. Positive end-expiratory pressure starting at five centimeters of water maintains alveolar recruitment and improves oxygenation, with higher levels indicated for refractory hypoxemia. Initial FiO2 of one hundred percent prevents desaturation, weaned rapidly once adequate oxygenation is confirmed to avoid oxygen toxicity.

Sedation and analgesia maintain patient comfort, ensure ventilator synchrony, and prevent dangerous complications from agitation including self-extubation and hemodynamic instability. Analgesia-first approaches using fentanyl provide pain control that reduces sedation requirements. Propofol infusion provides titratable sedation with rapid offset allowing neurological assessment but causes dose-dependent hypotension. Dexmedetomidine offers sedation without respiratory depression, potentially facilitating earlier extubation, but bradycardia and hypotension may occur. Ketamine provides sedation with bronchodilation and maintained hemodynamics, particularly useful in asthma and hypotensive patients. Sedation scales such as Richmond Agitation-Sedation Scale guide titration toward target sedation depth avoiding both undersedation with agitation and oversedation delaying liberation.

Troubleshooting acute deterioration in the intubated patient follows the DOPE mnemonic systematically evaluating common reversible causes before assuming primary disease progression. Displacement of the tube into the esophagus or right mainstem bronchus causes sudden desaturation and absent or unilateral breath sounds. Obstruction from mucus plugging, kinking, or patient biting the tube prevents adequate ventilation despite ventilator cycling. Pneumothorax, particularly tension pneumothorax, may develop spontaneously or from positive pressure ventilation, causing hypotension with unilateral breath sound loss. Equipment failure from disconnection, ventilator malfunction, or oxygen supply interruption requires systematic checking of the entire circuit. When deterioration occurs, immediate disconnection from the ventilator and manual bag ventilation allows simultaneous assessment of airway patency and equipment while other causes are evaluated.

<image>Panel A: Tube confirmation and securing showing lip-level documentation, radiographic position assessment, and continuous capnography monitoring. Panel B: Initial ventilator settings with mode selection, tidal volume calculation, respiratory rate, PEEP, and FiO2 parameters. Panel C: Sedation and analgesia options comparing propofol, fentanyl, dexmedetomidine, and ketamine with indications and cautions. Panel D: DOPE mnemonic for troubleshooting with Displacement, Obstruction, Pneumothorax, and Equipment evaluation.</image>

IX. Community-Acquired Pneumonia

Community-acquired pneumonia presents with cough often productive of purulent sputum, fever, pleuritic chest pain, and dyspnea, though elderly and immunocompromised patients frequently display atypical presentations with confusion, falls, or functional decline without classic respiratory symptoms. Physical examination reveals signs of consolidation including bronchial breath sounds, egophony, increased tactile fremitus, and crackles over the affected area. Chest radiograph demonstrating new infiltrate in the appropriate clinical context confirms the diagnosis, though early in disease course or in dehydrated patients, infiltrates may not yet be radiographically apparent. Laboratory abnormalities including leukocytosis suggest bacterial infection, though normal or low white blood cell counts may occur particularly in elderly or immunocompromised patients, and should not reassure against serious infection.

Severity assessment guides disposition decisions and treatment intensity, with multiple validated scoring systems available for clinical use. The CURB-65 score incorporates Confusion, Uremia with BUN above twenty milligrams per deciliter, Respiratory rate above thirty, Blood pressure systolic below ninety or diastolic below sixty, and age sixty-five or older, with each criterion scoring one point. Scores of zero to one generally support outpatient management, score of two suggests observation or admission, and scores of three to five indicate inpatient care with consideration of intensive care. The Pneumonia Severity Index offers more precise risk stratification but requires multiple laboratory values making bedside calculation cumbersome. Clinical judgment supplements scoring systems, as social factors, comorbidities, and ability to tolerate oral medications influence appropriate disposition.

Empiric antibiotic selection targets likely pathogens based on treatment setting and patient risk factors, with regimens covering both typical bacteria and atypical organisms. Outpatient treatment of otherwise healthy patients typically employs amoxicillin or doxycycline, with doxycycline offering additional coverage for atypical organisms. Patients with comorbidities including chronic lung, heart, liver, or kidney disease, diabetes, or recent antibiotic use require broader coverage with amoxicillin-clavulanate plus azithromycin or a respiratory fluoroquinolone such as levofloxacin or moxifloxacin. Inpatients receive ceftriaxone plus azithromycin or a respiratory fluoroquinolone providing coverage of typical and atypical pathogens. Severe pneumonia requiring intensive care adds consideration for Pseudomonas coverage with piperacillin-tazobactam or cefepime and MRSA coverage with vancomycin when risk factors are present.

Respiratory failure complicating pneumonia requires escalating respiratory support while antibiotics address the underlying infection. Supplemental oxygen maintains saturation above ninety-two percent, with escalation through nasal cannula, high-flow nasal cannula, and non-invasive ventilation as hypoxemia worsens. High-flow nasal cannula has emerged as valuable therapy providing high FiO2 with mild positive pressure and good patient tolerance. Non-invasive ventilation may provide temporary support but must be used cautiously in pneumonia given concerns about delayed intubation and increased secretion management challenges with mask ventilation. Intubation and mechanical ventilation become necessary when non-invasive support proves inadequate. Patients developing acute respiratory distress syndrome require lung-protective ventilation with low tidal volumes and appropriate PEEP, with prone positioning considered for severe hypoxemia.

<image>Panel A: Pneumonia presentation showing typical symptoms and atypical presentations in elderly and immunocompromised patients. Panel B: CURB-65 severity scoring with criteria, point values, and disposition recommendations by score category. Panel C: Empiric antibiotic regimens stratified by outpatient healthy, outpatient with comorbidities, inpatient, and ICU settings. Panel D: Respiratory support escalation from supplemental oxygen through HFNC, NIPPV, and mechanical ventilation with ARDS considerations.</image>

X. Other Respiratory Emergencies

Massive hemoptysis represents a life-threatening emergency where the primary danger is asphyxiation from airway flooding rather than exsanguination from blood loss, making airway management the immediate priority. Definitions vary but generally include greater than five hundred milliliters over twenty-four hours or greater than one hundred milliliters per hour of expectorated blood. Positioning the patient with bleeding lung dependent prevents blood from flooding the contralateral lung while preparations for definitive management proceed. Intubation using a large endotracheal tube facilitating suctioning and potential bronchoscopy should be performed early if the airway becomes threatened, with selective mainstem intubation of the non-bleeding lung or use of a bronchial blocker as advanced options. Definitive management includes bronchoscopic evaluation and intervention, bronchial artery embolization for hemoptysis of bronchial artery origin, and surgical resection when other measures fail.

Anaphylaxis causes upper airway obstruction through angioedema affecting the larynx and surrounding structures, typically accompanied by urticaria, bronchospasm, and cardiovascular collapse in severe cases. Epinephrine administered intramuscularly in the anterolateral thigh at zero point three to zero point five milligrams represents the cornerstone of treatment, providing alpha-adrenergic vasoconstriction to improve blood pressure and reduce angioedema along with beta-adrenergic bronchodilation. The dose may be repeated every five to fifteen minutes if symptoms persist or recur. Adjunctive medications including antihistamines with both H1 and H2 blockers, corticosteroids, and intravenous fluids for hypotension provide secondary benefit but must never delay epinephrine administration. Early airway management is indicated when stridor, voice changes, or progressive throat swelling suggest impending airway compromise, as delay until complete obstruction creates a near-impossible intubation scenario.

Epiglottitis, though now uncommon due to Haemophilus influenzae type b vaccination, remains a life-threatening cause of upper airway obstruction requiring immediate recognition and careful management. Presentation includes severe sore throat out of proportion to pharyngeal findings, drooling from inability to swallow secretions, muffled hot-potato voice, stridor, and often anterior neck tenderness over the hyoid. Patients assume sniffing or tripod position to maximize airway patency, and agitation from examination or procedures may precipitate complete obstruction. Lateral neck radiograph may show the thumbprint sign of an edematous epiglottis, but imaging should not delay airway management in unstable patients. The airway should be secured in a controlled setting with surgical backup immediately available, ideally in the operating room. Intravenous antibiotics covering respiratory pathogens, typically ceftriaxone or ampicillin-sulbactam, along with corticosteroids to reduce airway edema constitute medical management.

Foreign body aspiration presents differently in adults and children, with adults typically aspirating food during meals, often after alcohol consumption or with neurological impairment affecting swallowing, while children aspirate small objects during play. Complete obstruction causing inability to speak, cough, or breathe demands immediate intervention with abdominal thrusts for conscious patients or chest compressions and direct laryngoscopy for visualization and removal in unconscious patients. Partial obstruction with effective cough should not be interrupted by intervention attempts, as patient efforts may successfully dislodge the object. Radiography may demonstrate radiopaque foreign bodies, but many aspirated objects including food are not visible, requiring bronchoscopy when clinical suspicion remains high despite normal imaging. Rigid bronchoscopy provides both diagnostic confirmation and therapeutic removal of foreign bodies within reach of the bronchoscope.

<image>Panel A: Massive hemoptysis management priorities showing airway protection, dependent positioning, intubation indications, and definitive treatment options. Panel B: Anaphylaxis protocol emphasizing intramuscular epinephrine as first-line treatment with dosing, repeat intervals, and adjunctive medications. Panel C: Epiglottitis recognition with clinical features, imaging findings, and airway management approach with surgical backup. Panel D: Foreign body aspiration management comparing complete versus partial obstruction and intervention techniques for conscious and unconscious patients.</image>

Summary

• Respiratory distress assessment integrates visual inspection, pulse oximetry, blood gas analysis, and imaging to identify etiology and severity, with signs of impending failure including fatigue, altered mental status, and silent chest demanding urgent intervention
• Asthma exacerbation treatment centers on continuous albuterol, ipratropium for severe cases, and early systemic corticosteroids, with magnesium sulfate and BiPAP for refractory severe presentations
• COPD exacerbation management includes bronchodilators, corticosteroids for five days, antibiotics when purulent sputum present, and BiPAP for hypercapnic respiratory failure with pH below 7.35
• Pulmonary embolism evaluation uses clinical decision rules with Wells criteria and PERC to stratify testing, proceeding to D-dimer for moderate-risk patients and CT angiography for high-risk or D-dimer-positive patients
• Tension pneumothorax is a clinical diagnosis requiring immediate needle decompression at the second intercostal space midclavicular line or fourth to fifth intercostal space anterior axillary line, followed by tube thoracostomy
• Non-invasive ventilation benefits COPD exacerbation and cardiogenic pulmonary edema but requires recognition of failure within one to two hours and timely transition to intubation
• Rapid sequence intubation uses preoxygenation followed by induction with etomidate or ketamine and paralysis with succinylcholine or rocuronium, with capnography confirming placement
• Post-intubation care includes lung-protective tidal volumes of six to eight milliliters per kilogram ideal body weight, sedation titrated to target, and DOPE troubleshooting for acute deterioration
• Anaphylaxis requires immediate intramuscular epinephrine zero point three to zero point five milligrams with repeat dosing as needed, with early airway management for progressive throat swelling

Key Terms

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