Gas exchange

  • Q: What is gas exchange?

  • A: The process by which oxygen is transported to the cells and carbon dioxide is transported from the cell [1].

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  • Q: What is ventilation?

  • A: The process of breathing oxygen into the lungs [1].

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  • Q: What is transport in the context of gas exchange?

  • A: The availability and ability of hemoglobin to carry oxygen [1].

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  • Q: What is perfusion in the context of gas exchange?

  • A: Relates to the gas exchange in the cells [1].

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  • Q: What is ischemia?

  • A: Insufficient flow of oxygenated blood to tissues, may result in cell injury or death [1].

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  • Q: What is anoxia?

  • A: Total lack of oxygen in body tissues [1].

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  • Q: What is hypoxia?

  • A: Insufficient oxygen reaching cells [1].

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  • Q: What is hypoxemia?

  • A: Reduced oxygenation in arterial blood [1].

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  • Q: What structures are in the upper respiratory tract?

  • A: Nose, nasal cavity, mouth, pharynx (throat), larynx (voice box) [2].

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  • Q: What structures are in the lower respiratory tract?

  • A: Trachea, bronchi, bronchioles, alveolar ducts, and alveoli, surfactant, and blood supply [2].

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  • Q: Why are children at greater risk for impaired gas exchange?

  • A: A child’s airway is smaller and less developed than an adult’s [2].

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  • Q: What happens during inspiration?

  • A: It is active due to contraction of intercostal muscles and diaphragm [3].

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  • Q: What happens during expiration?

  • A: Usually passive, uses elastic recoil to expel air [3].

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  • Q: What is compliance?

  • A: Measure of the ease of lung expansion [3].

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  • Q: What is diffusion?

  • A: Oxygen and CO2 moving back and forth across the alveolar-capillary membrane [3].

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  • Q: How does the medulla control respiration?

  • A: The medulla has chemo receptors that respond to changes in PaO2, PaCO2 and Ph to affect breathing patterns [3].

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  • Q: How do mechanical receptors affect respiration?

  • A: Stretch receptors prevent over inflation of the lungs [4].

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  • Q: How do gases move during transportation?

  • A: Gas will always diffuse from areas of high concentration to areas of low concentration [4].

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  • Q: How is oxygen transported to the cells?

  • A: The high pressure of oxygen in alveoli causes it to diffuse into pulmonary capillaries, dissolves into the plasma and attaches to hemoglobin in RBCs [4].

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  • Q: How is carbon dioxide transported from the cells?

  • A: The high pressure of the CO2 in cells causes it to diffuse into plasma [5].

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  • Q: What is oxygen saturation (SaO2)?

  • A: Measures amount of oxygen bound to hemoglobin [5]. Normal adult is 95-100% [5].

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  • Q: What is SpO2?

  • A: Oxygen saturation level as measured on a pulse oximeter [5].

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  • Q: What is PaO2?

  • A: Pressure of oxygen dissolved in the arterial blood [5]. Normal adult is 80-100mmHg (found via ABG) [5].

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  • Q: How does hemoglobin concentration affect gas exchange?

  • A: Determines the oxygen and carbon dioxide transport capacity [6]. 1 gram of Hgb can carry about 1.34 ml of oxygen [6].

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  • Q: Who is at greatest risk for impaired gas exchange?

  • A: Especially infants and elderly [6].

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  • Q: What are the individual risk factors for impaired gas exchange?

  • A: Age, smoking, presence of chronic medical conditions, immunosuppression, reduced state of cognition, brain injury, prolonged immobility [6, 7].

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  • Q: What are the main causes of impaired gas exchange?

  • A: Ineffective ventilation, reduced capacity for gas transportation, inadequate perfusion [7].

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  • Q: What parts of the body are included in the assessment of respiratory status?

  • A: Nose, mouth, pharynx, neck, thorax, lung [8].

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  • Q: What are the expected findings during assessment of respiratory status?

  • A: Breathing=quiet and effortless (RR=12-20), O2 sats= 95-100%, Thorax appears symmetrical, expansion is equal bilateral, Trachea midline, AP diameter 1:2, Breath sounds=clear bilaterally, Has energy [8, 9].

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  • Q: What are the abnormal findings during assessment of respiratory status?

  • A: Shortness of breath/labored breathing (RR>20), O2 sats <92%, Thorax appears asymmetrical, expansion is unequal bilateral, Deviation of trachea, >1:2 AP diameter (=barrel chest), Breath sounds=rales, course crackles, wheezes, diminished, absent; presence of cough, Fatigue [8, 9].

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  • Q: What condition is indicated by finger clubbing?

  • A: Chronic hypoxemia [10, 11].

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  • Q: What condition is indicated by stridor?

  • A: Partial obstruction of trachea or larynx [10, 11].

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  • Q: What condition is indicated by wheezes?

  • A: Bronchoconstriction [10, 11].

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  • Q: What condition is indicated by pleural friction rub?

  • A: Pleurisy [10, 11].

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  • Q: What condition is indicated by increased tactile fremitus?

  • A: Lung consolidation with fluid or exudate [10, 11].

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  • Q: What condition is indicated by hyperresonance?

  • A: Air trapping [10, 11].

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  • Q: What condition is indicated by fine crackles?

  • A: Interstitial edema [10, 11].

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  • Q: What condition is indicated by absent breath sounds?

  • A: Atelectasis [10, 11].

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  • Q: What are some diagnostic tests for gas exchange?

  • A: O2 saturation monitoring, end tidal CO2 monitoring, sputum cultures, arterial blood gases (ABG’s), hemoglobin and hematocrit, abnormal cell cytology, Chest Xray, CTs, MRI, Pulmonary function test, V/Q Scan, Bronchoscopy, Thoracentesis, Lung biopsies [11, 12].

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  • Q: What is the first action the nurse should take if a pulse oximetry monitor indicates that the patient has a drop in SpO2 from 95% to 85%?

  • A: Assess patient for signs of cyanosis and check position of probe [11].

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  • Q: What is the purpose of thoracentesis?

  • A: HCP inserts needle into pleural space, to drain excess fluid [12].

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  • Q: What are some interventions for decreased gas exchange?

  • A: Positioning, oxygen therapy, airway management and support, chest physiotherapy and postural drainage, nutrition, medication administration [13].

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  • Q: What is FiO2?

  • A: The fraction of inspired O2 being delivered to the client [13].

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  • Q: What is the FiO2 of room air?

  • A: 21% [13].

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  • Q: How does increasing the liter of oxygen affect FiO2?

  • A: Increases the FiO2 by 3% [13].

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  • Q: How much oxygen is delivered via nasal cannula?

  • A: Low flow of O2 delivered in liter flow, 1LNC is about 24% oxygen should not be delivered at more than 6L [13].

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  • Q: How much oxygen is delivered via high flow nasal cannula?

  • A: Blends O2 with compressed air to generate a high FIO2 up to 100% and 60L [13].

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  • Q: How much oxygen is delivered via simple face mask?

  • A: O2 can be at 6-12L flow of 40-50% FIO2 [13].

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  • Q: How much oxygen is delivered via non-rebreather O2 mask?

  • A: Used for high flow O2 (10-15L) can give O2 up to 90% FIO2 [13].

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  • Q: How much oxygen is delivered via bag valve mask?

  • A: Can hook up to oxygen and deliver at 15L FiO2 100% [13].

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  • Q: How can gas exchange problems be prevented?

  • A: Infection control, smoking cessation, immunizations, preventing post-op complications [14].