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Flail Chest Case: Ventilator Protocols and Respiratory Manifestations

Case Overview

  • Traumatic flail chest case requiring intensive respiratory support and multidisciplinary management.
  • Key complications included pulmonary contusion/atelectasis, pneumonia, evolving bilateral infiltrates, right pleural involvement with bronchopleural fistula, and multiorgan dysfunction (initial fluid resuscitation-related cardiovascular strain and transient renal function impairment).
  • Course featured prolonged mechanical ventilation, progressive chest wall stabilization, infection risk from thick sputum, and eventual weaning after ~2 weeks of ventilatory support.

Initial Admission and Ventilator Course

  • Oxygenation strategy and ventilation settings:
    • Initial FIO₂: 0.40 (40%) with mechanical ventilation; routine ABG monitoring.
    • Across 72 hours: continued intubation and ventilation with FIO₂ = 0.40 and rate = 12/min; careful chest assessment for pneumothorax/pneumonia.
  • Clinical trajectory: aggressive IV fluid resuscitation at 100 mL/h; sputum became thick and yellow; lung expansion therapy increased to PEEP = 8 cm H₂O.
  • On the second day: right pneumothorax diagnosed; chest tube inserted; persistent air leak.
  • The following day: tachycardia to 160/min; BP 142/82 mm Hg; rectal temp 99.2°F; ventilator rate 12/min, PEEP 10 cm H₂O; auscultation with bilateral crackles.
  • ABG on FiO₂ = 0.70:
    • ext{pH} = 7.37,\, ext{PaCO}2 = 38 ext{ mmHg},\ ext{HCO}3^- = 23 ext{ mEq/L},\ ext{PaO}2 = 58 ext{ mmHg},\ ext{SaO}2 = 90 ext{%}
  • Therapeutic steps:
    • Rapid diuresis initiated; cardiac function reportedly improved dramatically.
    • Over the next days: chest radiographs showed dense bilateral infiltrates; oxygenation remained difficult even with high FiO₂.
    • Sputum remained thick and yellow; airway clearance emphasized.
  • Respiratory assessment and plan (key elements during hospitalization):
    • S: N/A—intubated, sedated, paralyzed.
    • O: Afebrile; HR 160; regular rhythm; BP 142/82; RR 12 on vent; right chest tube with air leak; crackles bilaterally.
    • CXR: fractures align; bilateral dense infiltrates; ABG on FiO₂ 0.70: pH 7.37, PaCO₂ 38, HCO₃ 23, PaO₂ 58, SaO₂ 90%; sputum thick and yellow.
    • P: Mechanical ventilation protocol with increased PEEP to 12 cm H₂O; maintain FiO₂ at 0.70; start Airway Clearance Therapy protocol; suction PRN; obtain sputum for Gram stain and culture; SaO₂ monitoring.
  • Early organ function data:
    • BUN rose to 60 mg/dL; creatinine rose to 1.9 mg/dL, attributed to trauma-related stress on kidneys; liver enzymes remained normal.
    • BUN and creatinine gradually normalized during weeks 2–3.
  • Weaning trajectory:
    • Weaning from the ventilator proceeded slowly and successfully over the next 2 weeks.

Pathophysiology and Respiratory Manifestations in Flail Chest

  • Coremechanisms:
    • Paradoxical movement of the chest wall occurs when double fractures involve at least three adjacent ribs, causing chest wall instability and abnormal ventilation.
    • Pendelluft: gas movement between the two lungs during a single respiratory cycle due to regionally different pleural pressures, leading to dead-space rebreathing and hypoventilation.
    • Chest wall instability and atelectasis reduce alveolar ventilation and promote shunt-like venous admixture.
  • Consequences for gas exchange:
    • Decreased ventilation-perfusion ratio leads to intrapulmonary shunting and venous admixture, lowering PaO₂ and CaO₂.
    • Peripheral chemoreceptors are stimulated by hypoxemia, increasing ventilatory drive.
  • Clinical implications:
    • Increased respiratory rate as a compensatory response to hypoxemia and chest wall instability.
    • Possible development of ARDS in severe cases, prompting higher PEEP and tighter oxygenation strategies.
  • Radiologic and anatomical notes:
    • Chest radiographs may show increased density in atelectatic areas or regions of post-flail pneumonia.
    • Rib fractures can require dedicated rib series to visualize.
    • The chest radiograph may reveal bilateral dense infiltrates reflecting atelectasis or consolidation.
  • Notable clinical signs:
    • Paradoxical chest movement with inspiration (inward rib movement) and outward bulging of the flail segment during expiration.
    • Diminished breath sounds bilaterally in some cases; chest wall instability correlates with gas exchange abnormalities.

Respiratory Care and Ventilation Protocols

  • Lung Expansion Therapy Protocol:
    • Administer to offset/alleviate alveolar consolidation and atelectasis associated with flail chest.
    • Mild analgesia may be used if expansion techniques cause pain.
  • Mechanical Ventilation Protocol:
    • Acute ventilatory failure associated with flail chest often necessitates continuous mechanical ventilation, frequently with PEEP, to maintain adequate ventilation.
    • See also: Ventilator Initiation and Management Protocol (Protocol 11.1) and Ventilator Weaning Protocol (Protocol 11.2).
  • Oxygen Therapy Protocol:
    • Oxygen is used to treat hypoxia and decrease work of breathing, but hypoxemia due to alveolar atelectasis/capillary shunting can be refractory to oxygen therapy alone.
    • FiO₂ targets are adjusted per protocol to maintain adequate saturation while avoiding oxygen toxicity.
  • Clinical imaging and assessment integration:
    • Radiographs and ABG values are used to guide PEEP adjustments and ventilator support.
    • Documentation of ventilator settings should accompany ABG values in SOAP notes.
    • The respiratory therapist may correlate sputum characteristics with infection risk and culture results.

Case Study: Flail Chest – Admitting History and Respiratory Management Details

  • Patient: 40-year-old, obese male involved in a major multi-vehicle collision.
  • Presenting vital signs and exam:
    • BP 80/62 mm Hg; pulse 90 bpm; RR 42 breaths/min (shallow); marked agitation/respiratory distress; paradoxical chest wall movement on the right.
  • Injuries and findings:
    • Right anterolateral chest fractures: double fractures of ribs 2–10; eyelid laceration; thigh lacerations with patellar tendon rupture; increased AP chest diameter; diminished breath sounds bilaterally; prolonged expiration.
    • Thoracic imaging: no pneumothorax or hemothorax initially; double fractures identified; AP diameter enlargement noted.
  • Initial ventilator settings in ED:
    • V₁ (tidal volume) = 8 mL/kg; PEEP = 5 cm H₂O; FiO₂ = 1.0; rate = 12/min.
    • ABG in operating room on 100% O₂: ext{pH} = 7.48, ext{ PaCO}2 = 30 ext{ mmHg}, ext{HCO}3^- = 23 ext{ mEq/L}, ext{ PaO}2 = 360 ext{ mmHg}, ext{ SaO}2 = 98 ext{%}
  • Postoperative ICU management:
    • No spontaneous respirations; pharmacologic paralysis (vecuronium) for ventilation control; FiO₂ remained at 1.0 until stabilization.
    • Initial assessment: double rib fractures; no pneumothorax or hemothorax on radiographs; flail chest features present.
    • Ventilatory strategy: Decrease tidal volume (V₊) to correct acute alveolar hyperventilation and maintain controlled ventilation with PEEP until chest wall is stable; wean protocol implemented as stabilization occurs.

Radiologic Findings and General Management

  • Chest radiographs:
    • Increased opacity in atelectatic areas or areas with post-flail pneumonia.
    • Rib fractures may require rib series for demonstration.
    • In flail chest, density on the affected side increases due to compression and atelectasis.
  • General management principles:
    • Mild cases: analgesia and routine airway clearance may suffice.
    • Severe cases: stabilization of the chest is necessary to permit bone healing and prevent atelectasis; continuous mechanical ventilation with PEEP is commonly used.
    • Paralytics may be required for ventilatory control in severe cases.
    • Typical duration of mechanical ventilation for bone healing: approximately 5–10 days.
  • Additional notes:
    • Oxygen therapy is essential but hypoxemia from capillary shunting may persist despite high FiO₂; balance with PEEP to optimize alveolar recruitment.

Oxygen Therapy and Airway Clearance

  • Oxygen Therapy Protocol:
    • Used to treat hypoxia and reduce work of breathing; however, hypoxemia from atelectasis/capillary shunting can be refractory to oxygen alone.
  • Airway Clearance and Sputum Management:
    • Sputum can be thick and yellow; mucus plugging contributes to hypoxemia and infection risk.
    • Sputum Gram stain and culture recommended for targeted antibiotic therapy when infection suspected.
    • Airway clearance therapy, suctioning as needed, and monitoring of sputum characteristics are integral to care.

Clinical Lab Trends and Recovery

  • Renal function and liver enzymes:
    • BUN increased to 60 mg/dL; creatinine rose to 1.9 mg/dL during the first week, likely trauma-related.
    • Renal values gradually returned toward baseline during week 2.
  • Cardiorespiratory improvement:
    • Cardiac function improved with diuresis; no sustained hypotension reported post-resuscitation.
    • Ventilatory support gradually weaned over the ensuing weeks with continued monitoring.

Key Concepts and Formulas (Selected)

  • Key variables:
    • V_T = ext{tidal volume} \ ext{(mL/kg)}
    • RR = ext{respiratory rate (breaths/min)}
    • FIO_2 = ext{fraction of inspired oxygen}
    • PEEP = ext{positive end-expiratory pressure}
  • Pathophysiology terms:
    • Pendelluft: gas shift between lungs during the respiratory cycle due to asynchronous alveolar compression/expansion in flail chest.
    • Venous admixture: shunt-like process where deoxygenated blood mixes with oxygenated blood, reducing arterial PaO₂.
  • Typical management milestones:
    • Use of PEEP to stabilize the chest wall and improve oxygenation in the presence of ARDS or severe atelectasis.
    • Early airway clearance and infection surveillance via sputum Gram stain/culture.
    • Weaning after stabilization and radiographic improvement, often spanning days to weeks depending on injury severity.

Connections to Foundational Principles and Real-World Relevance

  • Mechanistic links:
    • Flail chest disrupts normal rib cage mechanics, leading to paradoxical movement, decreased alveolar ventilation, and gas exchange impairment.
    • PEEP helps recruit collapsed alveoli, improves oxygenation, and stabilizes the chest wall to facilitate healing.
  • Clinical implications:
    • Multiorgan involvement is common in major chest trauma; vigilant monitoring for renal, hepatic, and cardiac function is essential.
    • Prolonged hospitalization and frequent assessments (e.g., >120 observations) may be necessary to manage evolving conditions and adjust therapy.
  • Ethical and practical considerations:
    • Balancing aggressive fluid resuscitation with risk of pulmonary edema and worsened oxygenation requires careful hemodynamic monitoring.
    • Pain management and early mobilization are critical, but analgesia must not compromise airway protection or ventilatory drive.

Self-Assessment Questions (with Answers)

1) In flail chest, which of the following occur? 1) Tidal volume (V_T) increases 2) Atelectasis often occurs 3) Intrapulmonary shunting occurs 4) Pneumothorax is rare

  • Answer: c) 2 and 3 only

2) When a patient has a severe flail chest, which of the following occurs? a) Venous return increases b) Cardiac output increases c) Systemic blood pressure increases d) Central venous pressure increases

  • Answer: d) Central venous pressure increases

3) A flail chest consists of a double fracture of at least:

  • a) Two adjacent ribs b) Three adjacent ribs c) Four adjacent ribs d) Five adjacent ribs
  • Answer: b) Three adjacent ribs

4) Which of the following respiratory care technique(s) is (are) commonly used in the treatment of severe flail chest? 1) Cough and deep breathe 2) Intubation with continuous mandatory ventilation 3) Negative pressure ventilation (cuirass) 4) Positive end-expiratory pressure/continuous positive airway pressure (PEEP/CPAP)

  • Options:
    • a) 1 only
    • b) 3 only
    • c) 2 and 4 only
    • d) 2, 3, and 4 only
  • Answer: c) 2 and 4 only

5) When mechanical ventilation is used to stabilize a flail chest, how much time generally is needed for adequate bone healing to occur?

  • a) 5 to 10 days
  • b) 10 to 15 days
  • c) 15 to 20 days
  • d) 20 to 25 days
  • Answer: a) 5 to 10 days

Note on Documentation

  • As recommended in the case discussion, ventilator settings and ABG values should be clearly documented in the SOAP notes to track changes in respiratory status and to guide ongoing management.