Gas Exchange and Oxygenation: The Upper Respiratory System

The Respiratory System

Respiratory systems is divided into two functional Systems: 1 Respiratory systems is divided into two functional Systems: 1. Upper Respiratory Tract nares, nasal cavity, pharynx and larynx 2. Lower Respiratory Tract trachea, bronchi, bronchioles, alveoli, and alveolar-capillary membrane

Oxygenation Ventilation – movement of air to the alveoli. A mechanical action Respiration – gas exchange at the alveolar-capillary membrane Perfusion – blood flow at the alveoli-capillary bed. Affected by lung pressure and resistance, edema, secretions and bronchospasm. Diffusion – movement of oxygen into capillaries and carbon dioxide out of the blood.

Gas Exchange Gas exchange is the process by which oxygen is transported to cells and carbon dioxide is transported from cells. Impairment of gas exchange occurs when the diffusion of gases (oxygen and carbon dioxide) are affected by: Ineffective ventilation Reduced capacity for gas transportation (reduced hemoglobin and/or red blood cells), e.g. blood loss or anemia Inadequate perfusion

Risk Factors for Impaired Gas Exchange Presence of chronic medical conditions, such as: chronic obstructive pulmonary disease (COPD), emphysema cystic fibrosis (CF), heart Failure (HF) Age Smoking Immunosuppression Reduced state of cognition Brain injury Prolonged immobility

Pathophysiology: Upper Respiratory System Common cold is a viral infection that starts in the upper respiratory tract, sometimes spreading to the lower structures. Allergic or seasonal rhinitis occurs when the upper airways respond to a specific allergen. Sinusitis occurs when the epithelial lining of the sinus cavities becomes inflamed. It can be caused by bacteria or viruses. Pharyngitis is an inflammation or infection of the pharynx. Laryngitis is an inflammation of the larynx. Influenza is an infection caused by any of several strains of myxo-viruses.

Upper Respiratory System

Drug Classifications for Upper Respiratory Disease Antitussives Antihistamines Decongestants Expectorants Mucolytics Anti-inflammatories

Antitussive Drugs Prototype drug: dextromethorphan (Robitussin DM) Antitussives are drugs that suppress the cough reflex. Many disorders of the upper and lower respiratory tracts are accompanied by an uncomfortable, nonproductive cough. Coughing normally is a protective mechanism that forces foreign irritants out of the respiratory system, opening it for more efficient flow of air. Prototype drug: dextromethorphan (Robitussin DM)

Dextromethorphan: Core Drug Knowledge Pharmacotherapeutics Chronic nonproductive cough Pharmacokinetics Administered: oral. Metabolism: liver. Excreted: kidneys. Pharmacodynamics Directly affects the cough center in the medulla in the brain (CNS effect) Chemically related to the opiate agonists and can suppress coughing as effectively as narcotics.

Dextromethorphan: Core Drug Knowledge (cont.) Contraindications and precautions Chronic coughs resulting from emphysema and asthma Side effects Nausea, vomiting, drowsiness, dizziness, irritability, and restlessness Adverse effects Poor respiratory clearance due to cough suppression effect

Dextromethorphan: Teaching, Assessment, and Evaluation Patient and family education Emphasize that sedation, drowsiness, and impaired orientation can occur. Advise not to drive or operate heavy equipment. Caution patients who are taking certain antidepressants. Ongoing assessment and evaluation Monitor the effect of dextromethorphan on the patient’s motor control, sedation, and respiratory status.

Discussion Question Would an antitussive be a good idea for a patient with severe lower respiratory disease, such as emphysema? Why or why not?

Decongestant Drugs Prototype drugs: pseudoephedrine (Sudafed) Decongestants are drugs taken to decrease nasal congestion, a condition that is caused by an inflammatory response in the upper respiratory tract. Nasal decongestants work by constricting the nasal arterioles, thereby decreasing the swelling of the nasal membrane. These drugs can be administered orally or topically. Prototype drugs: pseudoephedrine (Sudafed) Phenylephrine (Neo-Synephrine)

Pseudoephedrine: Core Drug Knowledge Pharmacotherapeutics Reduces the volume of nasal mucus and is recommended for the temporary relief of nasal congestion Pharmacokinetics Administered: oral. Metabolism: liver. Excreted: kidneys. Onset: 30 minutes. Pharmacodynamics Causes vasoconstriction in the nasal mucous membranes

Pseudoephedrine: Core Drug Knowledge (cont.) Contraindications and precautions Caution with pregnancy and lactation Adverse effects Tension, anxiety, restlessness, tremor, insomnia, and weakness Maximizing therapeutic effects Encourage patients to use a humidifier, drink plenty of fluids, and avoid smoke-filled rooms. Minimizing adverse effects Provide the patient with appropriate safety measures.

Pseudoephedrine: Teaching, Assessment, and Evaluation Patient and family education Explain to patients that the purpose of the drug is to promote breathing and relieve congestion. Caution patients to avoid using other OTC drugs. Ongoing assessment and evaluation Monitor patients receiving pseudoephedrine for rebound congestion, sedation, dizziness, insomnia, weakness, tremor, and urinary retention.

Discussion Questions What else do you know about pseudoephedrine (Sudafed)? It’s access is controlled as it is a main ingredient in the illegal manufacture of methamphetamine. “Extra credit”: What herbal remedy is related to pseudoephedrine? Ma Huang, which is now banned due to deaths in athletes from cardiac arrest.

Decongestants: Phenylephrine Phenylephrine (Neo-Synephrine) usually used in nasal spray form to treat allergic or nonallergic rhinities by relieving nasal stuffiness and as a decongestant for sinusitis and the common cold Pharmacodynamics stimulates alpha-1 adrenergic receptors in the sinuses causing reduction in inflammation of the nasal membranes

Decongestants: Phenylephrine Contraindicated Chronic rhinitis and caution in hypertension or coronary artery disease Adverse Reactions CNS Stimulation – agitation, nervousness, unease Vasoconstriction Rebound nasal congestion develops very quickly Minimizing Adverse Effects Do not use nasal spray more than 3-5 days Taper use by alternating nostrils every other day

Nasal Glucocorticoids: Mometasone Mometasone (Nasonex) are given by nasal spray Pharmacotherapeutics Used to decrease the inflammation associated with allergic rhinitis by reducing: sneezing, nasal itching, and runny nose. Adverse Effects Sore throat, nosebleed, headache, burning in the nose Minimizing Adverse Effects/Patient Education Administer daily – not PRN It may take up to 7 days to reach desired effects

Antihistamines Prototype drug: Loratadine (Claritin) Antihistamines are used to relieve symptoms of allergies. These drugs block the action of histamine as it is released during the inflammatory response to an antigen. Effective for allergic rhinitis. Their action restores normal airflow through the upper respiratory system. Prototype drug: Loratadine (Claritin) or fexofenadine (Allegra)

Loratadine: Core Drug Knowledge Pharmacotherapeutics Relieves symptoms associated with seasonal and perennial allergies Pharmacodynamics Selectively blocks the effects of histamine at H1-receptor sites Contraindications and precautions Hypersensitivity Adverse effects Nausea, drowsiness, dyspepsia, and fatigue

Loratadine : Nursing Diagnoses and Outcomes Risk for Injury caused by drowsiness and fatigue related to drug-induced CNS effects Patient and family education Caution patients to take the drug as prescribed. Tell patients to avoid the use of other OTC drugs.

Expectorant Drugs Prototype drug: guaifenesin Expectorants are drugs that liquefy lower respiratory tract secretions. This effect decreases the viscosity of the secretions and improves airflow. Expectorants are available in many OTC preparations. Prototype drug: guaifenesin

Guaifenesin: Core Drug Knowledge Pharmacotherapeutics Relieves dry, nonproductive cough Pharmacodynamics Enhances the output of respiratory tract fluids by reducing the adhesiveness and surface tension of the fluids Contraindications and precautions Known allergy to medication Adverse effects GI symptoms, headache, and dizziness

Guaifenesin: Patient Education Maximizing therapeutic effects Teach the patient about good pulmonary hygiene, which includes coughing, using deep breathing, drinking plenty of fluids, and using a humidifier. Minimizing adverse effects Suggest that the patient eats small, frequent meals to alleviate GI upset. Guaifenesin should only be used for one week.

Mucolytic Drugs Prototype drug: acetylcysteine (Mucomyst) Mucolytics break down mucus. The drugs can be administered by a nebulizer or by direct instillation into the trachea. Mucolytics usually are reserved for patients who have major difficulty mobilizing and coughing up secretions. Prototype drug: acetylcysteine (Mucomyst)

Acetylcysteine: Core Drug Knowledge Pharmacotherapeutics Used to liquefy the thick, tenacious secretions. Pharmacodynamics It splits disulfide bonds that are responsible for holding the mucous material together. Contraindications and precautions Hypersensitive Adverse effects Bronchospasm, bronchoconstriction, chest tightness, a burning feeling in the upper airway, and rhinorrhea Unpleasant (sulfur, rotten egg) smell with

Acetylcysteine: Planning and Interventions Maximizing therapeutic effects Administer an inhaled beta-agonist before administering acetylcysteine. Minimizing adverse effects Inform the patient that nebulization may produce an initially disagreeable odor, but that this odor is transient.

Drug + Effect Matching Loosens/thins secretions Rebound nasal congestion Suppresses mucous production due to anticholinergic effects Central nervous system suppression of cough reflex Allergic rhinitis Sympathetic nervous system stimulation Phenylephrine Acetylcysteine Mometasone Pseudoephedrine Dextromethorphan Loratadine

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Answers to NCLEX-Style Questions 1. B 2. B 3. C 4. A

Case Study: The Common Cold Erika Adams, age 22, comes to the nurse-run clinic at the university with complaints of a cold and flu-like symptoms. She states that her cough is keeping her up at night. Data obtained from the nursing assessment include the following: Complaints of fatigue, body aches, cough, nasal congestion, and mild fever Vital signs: temperature, 99.1°F; pulse, 90; respiration, 20; blood pressure, 98/68 Harsh nonproductive cough noted.

Case Study: The Common Cold You suggest comfort measures, including rest and increased fluids, a steam vaporizer. The patient’s recommended medications include the use of pseudoephedrine, 30 to 60 mg PO every 4 to 6 hours PRN; and dextromethorphan, 30 mg PO every 4 to 8 hours PRN.

Case Study: The Common Cold How do these drugs work together to address Erika’s underlying pathologic conditions? What other medications may have been considered for treating Erika’s symptoms? Which findings might demonstrate possible adverse effects from drug therapy? What teaching is required for Erika regarding her drug therapy?