Respiratory System Anatomy and Mechanisms

Respiratory Physiology

• Intercostal muscles are located in between ribs
• The lung is surrounded by a pleural sac, which has parietal pleura and visceral pleura
• The diaphragm is positioned at the bottom of lungs

Upper Respiratory Tract

• The upper respiratory tract includes the nose, mouth, pharynx, epiglottis, larynx, and trachea

Lower Respiratory Tract

• The lower respiratory tract includes the bronchi, bronchioles, alveolar ducts, and alveoli
• Lung lobes are also part of lower respiratory tract

Conducting Airways

• The trachea leads to the following:
  • Bronchi
  • Segmental bronchi
  • Sub-segmental bronchi
  • Bronchioles
  • Alveolar ducts
  • Alveoli
• Generations:
  • Trachea- 0
  • Bronchi - 8
  • Segmental bronchi- 15
  • Subsegmental bronchi - 21-22
  • Alveolar Ducts - 24
  • Alveoli - 28

Mechanism of Respiration - Inspiration

• The diaphragm descends and intercostal muscles contract, causing ribcage expansion
• Thoracic cavity volume increases, intrapulmonary volume increases causing decreased intrapulmonary pressure
• Air will enter nose/mouth

Mechanism of Respiration - Expiration

• Diaphragm rises and intercostal muscles will relax causing rib cages to descend.
• Thoracic cavity volume decreases leading to decreased intrapulmonary volume, causing increased intrapulmonary pressure
• Gas will flow out the lungs

Regulation of Respiration - Neural Regulation

• The central nervous system controls the respiratory rate, and rhythm
• The cerebral cortex regulates the voluntary control of respiration

Regulation of Respiration - Chemical Regulation

• The rate and depth of respirations are based on changes in the blood concentrations of CO₂ and O₂, and in hydrogen ion concentration (pH)
• Chemoreceptors in the medulla, aortic body and carotid body sense changes in the chemical content and stimulate neural regulators to adjust

Steps in Oxygenation

• Ventilation refers to the process of moving gases into and out of the lungs
• Diffusion is the exchange of respiratory gases in the alveoli and capillaries
• Perfusion is the ability of the cardiovascular system to pump oxygenated blood to the tissues and return deoxygenated blood to the lungs

Respiratory Gas Exchange

• The thickness of the alveolar capillary membrane affects the rate of diffusion
• Oxygen transport is the combination of Lungs + cardiovascular (CV) system
• Hemoglobin carries O₂ and CO2
• Carbon dioxide transport

Respiratory Defense Mechanism

• Respiratory defense mechanisms include:
  • Filtration of air
  • Mucociliary clearance system
  • Cough reflex
  • Reflex bronchoconstriction
  • Alveolar macrophages

Terminology

• Work of breathing is the effort required to expand and contract the lungs: inspiration and expiration
• Surfactant is a chemical produced in the lungs to maintain the surface tension of the alveoli and keep them from collapsing
• Atelectasis refers to a collapse of the alveoli that prevents normal exchange of oxygen and carbon dioxide
• Hypoxia refers to inadequate tissue oxygenation at the cellular level.
  • It is life threatening and if left untreated can lead to fatal cardiac dysrhythmias.
  • The earliest sign is restlessness and changes in level of consciousness
• Hypercapnia is excessive CO2 in the bloodstream
• Hyperventilation is inadequate alveolar ventilation to meet the oxygen demand of the body or eliminate sufficient CO2
  • Decreased CO2 means blood is more alkaline
• Hypoventilation is a state of ventilation in which the lungs remove CO2 faster than it is produced by cellular metabolism
  • Increased CO2 means blood is more acidic
• Cyanosis involves Blue discoloration of the skin and mucous membranes caused by decreased hemoglobin in capillaries
  • A late sign of hypoxia; observed in tongue, soft palate, and conjunctiva of the eye

Cardiovascular Physiology

• Myocardial pump includes two atria and two ventricles
  • When the myocardium stretches, the strength of the subsequent contraction increases (Starling's law)
• Coronary artery circulation involves the coronary arteries supplying the myocardium with nutrients and remove wastes
• Myocardial blood flow is unidirectional through four valves
  • S1: mitral and tricuspid close
  • S2: aortic and pulmonic valves close
• Systemic circulation involves the arteries and veins delivering nutrients and oxygen and remove waste products

Critical Lab Values

• PaO2 values are:
  • ≥70%: SpO2 ≥94% Significance: Adequate unless hemodynamically unstable or has difficulty releasing O₂ to the tissues
  • 60%: SpO2 90% Significance: Adequate in almost all patients but with less error margin
  • 55%: SpO2 88% Significance: Adequate with chronic hypoxemia, if no cardiac event
  • 40%: SpO2 75% Significance: Inadequate but maybe acceptable short term basis (CO2 retention)
  • <40%: SpO2 <75% Significance: Inadequate, tissue hypoxia and cardiac dysrhythmias is possible.

Blood Gas Normal Values - Arterial Blood Gases

• Assumes patient is ≤60 years of age and breathing room air.
• Values decrease with age.
• The same normal values when SpO2 are obtained by oximetry.
• Normal values at sea level:
  • pH: 7.35-7.45
  • PaO2: 80-100 mm Hg
  • SaO2: >95%
  • PaCO2: 35-45 mm Hg
  • HCO3-: 22-26 mEq/L (mmol/L)

Blood Gas Normal Values - Venous Blood Gases

• Assumes patient is ≤60 years of age and breathing room air.
• Values decrease with age.
• The same normal values when SvO2 are obtained by oximetry.
• Normal values at sea level:
• pH: 7.32-7.43
• PvO2: 38-42 mm Hg
• SvO2: 60%-80%+
• PVCO2: 38-55 mm Hg
• HCO3-: 22-26 mEq/L (mmol/L)

Factors Affecting Oxygenation

• Physiological
• Developmental
• Lifestyle
• Environmental

Physiological Factors

• Any disorder that affects the body to meet oxygen demands affects oxygenation
• Respiratory and cardiac disorders
  • Conduction disturbances such as dysrhythmias affecting oxygenation:
    • stenosis
    • regurgitation
  • myocardial ischemia ( angina pectoris and myocardial infarction)
  • altered cardiac output (heart failure (left or right))
• Decreased oxygen-carrying capacity:
  • Anemia
  • Carbon monoxide poisoning (CO)
• Hypovolemia:
  • Shock and severe dehydration leads to extracellular fluid loss and reduced circulating blood volume leading to hypoxia which affects oxygenation.
• Decreased inspired oxygen concentration (FiO2)
  • High altitude, hypoventilation (drug overdose) affects oxygenation

More Physiological Factors

• Increased metabolic rates affects oxygenation
  • Seen in pregnancy, wound healing, exercise, and fever.
• Conditions reducing chest wall movement affects oxygenation
  • Seen in pregnancy and obesity
• Musculoskeletal abnormalities affects oxygenation
  • Includes flail chest and cerebral palsy
• Neuromuscular Disease
  • Guillain-Barre syndrome, myasthenia gravis, and poliomyelitis
• Central Nervous System
  • Disease or trauma to medulla oblongata
  • Cervical trauma to C3-C5 causes phrenic nerve damage (controls diaphragm movement)

Developmental Factors

• Infants and toddlers
  • Immature immune system, frequent upper respiratory infections
• School-age children and adolescents
  • Frequent upper respiratory infections
  • Risk for cigarette smoking in adolescents
• Young and middle adults
  • Cardiopulmonary risk factors such as unhealthy diets, lack of exercise, stress, smoking, illegal substances
• Older adults
  • Risk for respiratory infections
  • Decreased elastic recoil of lungs and stiffening of chest walls lead to more rounded and smaller lungs.
  • Physiological changes through calcification of heart valves, SA nodes, and costal cartilages and atherosclerotic plaques. -Alveoli enlarget which decreases surface area for gas exchange
  • Decreased functional cilia – which decreases cough mechanism

Lifestyle Factors

• Nutrition
  • Obesity decreases lung expansion and increase tissue oxygen demands
  • Malnourishment causes respiratory muscle wasting and decreased respiratory excursion
  • Anemia occurs
• Exercise
  • Increases efficiency of myocardial muscle
  • Recommended for 30-60 minutes per day
• Smoking
  • Nicotine causes vasoconstriction worsening peripheral vascular and coronary artery disease
  • COPD
• Substance Abuse
  • Alcohol depresses the respiratory center
  • Inhalants cause direct lung damage
• Stress
  • Body will respond with increase metabolic rate and oxygen demand

Environmental Factors

• Urban areas -Pollution
• Occupational pollutants -Asbestos, talcum powder, dust and airborne fibers
• Tobacco smoke causes a -Higher incidence of pneumonia, ear infections and asthma in children

Nursing Assesment - History

• Chest pain
  • Angina Pectoris requires immediate thorough evaluations; also evaluate location, duration, radiation, and frequency of issues
    • Men present with left side of chest with radiation to left arm
    • Women present with less definitive symptoms: nausea, fatigue, breathlessness
  • Pleuritic chest pain involves inflammation or infection of the pleural space, worsening with inspiration; knifelike lasting from minutes to hours
  • Musculoskeletal pain is caused by costochondritis (from prolonged coughing episodes) or exercise; pain worsens with inspiration
• Fatigue is a subjective loss of endurance that may be an early sign of worsening chronic disease.
  • Ask patients to rate on scale 0-10
• Dyspnea: difficult or uncomfortable breathing that is a Clinical sign of hypoxia that can occur with exertion, stress or respiratory infections
  • Orthopnea is identified by the number of pillows needed to comfortable breathe
  • Can present with the use of accessory muscles, nasal flaring or marked increased in rate and depth of respiration
  • Ask patient to rate on scale 0-10
• Cough
  • Productive or nonproductive sputum; note the color, blood-tinged, consistency, odor, and amount
  • Hemoptysis involves bloody sputum with alkaline pH
  • Hematemesis occurs in the Gl tract and has acidic pH
  • When does the cough occur? note specific times of day.
  • Coughing early morning or when rising may be caused by GERD or sinusitis
• Wheezing is a High pitched musical sound from narrowed airway
  • Can be caused by asthma, acute bronchitis, or pneumonia
  • Occurs inspiration, expiration or both -Determine if there are any precipitating factors: URI, allergens, exercise or stress
• Environmental or Geographical Exposures:
  • Carbon monoxide (CO), Smoke, Occupational
• Smoking -Direct or indirect exposure to tobacco -Pack-year history (packages per day x years)
• Repiratory infections
  • Frequency and duration of respiratory tract infection
  • Average: 4 per year
  • Vaccinations: pneumococcal, influenza
  • HIV infection: opportunistic infections (P. carinii pneumonia)

Rest of Nursing Assessment - History

• Alleries
• Health Risks -History of lung cancer or cardiovascular disease
• TB exposure
• Medications

Physical Examination - Inspection

• Note Level of Consciousness
• Chest wall movement should be examined for retractions (sinking in of soft tissues of chest between intercostal space) and Accessory muscles
• Breathing pattern can take the form of Apnea, Paradoxical breathing (chest wall contracts during inspiration and expands during exhalation), Kussmaul respiration (metabolic acidosis), and Cheyne-Stokes respirations (periods of apnea with deep breathing)
• Patients in distress may take on a Tripod position
• Respirations should be observed a normal adult (12 to 20 regular breaths/min)
• Nail clubbing indicates prolonged oxygen deficiency, endocarditis, and congenital heart defects.

Physical Exam - Palpation

• Involves Thoracic excursion
• Should be examined for Fremitus, Thrills, Heaves
• Cardiac point of maximal impulse (PMI)
• Examine Peripheral Extremities for Capillary refills (<2-3 seconds), Peripheral pulses, and Skin temperature and color

Physical Exam - Auscultation

• Auscultate for Adventitious lung sounds and abnormal heart sounds (S3, S4, murmurs)

Nursing Diagnosis and Planning

• Activity intolerance, decreased cardiac output, and fatigue can lead to: -Impaired gas exchange, impaired spontaneous ventilation, or impaired verbal communication
• The following have the potential to cause ineffective airway clearance, ineffective breathing pattern, or ineffective health maintenance: -Risk for aspiration, risk for infection, risk for suffocation
• Risk for imbalanced fluid volume

Goals

• Focus on Ineffective airway clearance related to pulmonary secretions -Pulmonary secretions will return to baseline levels within 24 to 36 hours.
• Patient's oxygenation status will improve in 36 hours.

Implementation: Health Promotion

• Involve Vaccinations: Influenza and pneumococcal
• Practice a Healthy lifestyle by eliminating risk factors and eating right and doing regular exercise.
• Avoid Environmental pollutants, secondhand smoke, work chemicals, and pollutants

Acute Care Implementation

• Administer Pharmacological agents such as Bronchodilators, inhaled steroids, mucolytic, and low dose anti-anxiety medications
• Oxygen therapy protocols
• Use Physical techniques -Breathing techniques, Cough control, Relaxation techniques

Airway Management

• Maintain free Trachea, bronchi, and large airways from obstruction
• Involve Mobilization of pulmonary secretions and Maintian clear airways by coughing or suctioning Decreases recovery time and complications
• Provide Hydration to maintain thin easily removable secretions
  • Maintain 1500-2500 ml/day unless contraindicated
• Use Humidification to make procedure necessary if patient is receiving oxygen (>4 L/min)
• Use Nebulization with moisture and medication to inspired air by mixing particles of varying size to the air
• Enhances mucociliary clearance for removal of mucus and cellular debris

Airway Management Techniques

• Coughing and Deep breathing postoperative after Q 2 hours while awake to prevent accumulation of secretions
  • Cascade cough, Huff Cough, and Quad cough
• Acute phase of mucus production involves Deep breathing Q 2 hours while awake, Cough Q 1 hour while awake, and Cough Q 2 - 3 hours at night time
  • Deep inhalation increases lung volume and airway diameter Allows air to move and pass through partially obstructed mucus plugs or foreign matter
• Chest physiotherapy (CPT)
  • Postural drainage, chest percussion and vibration
  • Is followed by coughing or suctioning of a patient who has the decreased ability to cough
• Recommended for patients with mucus production > 30 mL/day

Airway Management Techniques - Suctioning

-Use Sterile technique with oropharynx and trachea and suction oral secretions last

• Oropharyngeal and nasopharyngeal:
  • Used when the patient can cough effectively but is not able to clear secretions
• Orotracheal and nasotracheal: -Used when the patient is unable to manage secretions
• Tracheal suctions are used with an artificial airway

Airways

• Oral airway prevents obstruction of the trachea by displacement of the tongue into the oropharynx
• Endotracheal and tracheal airways are for short-term use to ventilate, relieve upper airway obstruction, protect against aspiration, and clear secretions
• Tracheostomy is a long-term assistance where surgical incision is made into trachea

Maintenance and Promotion of Lung Expansion

• Encourages Ambulation, Positioning (reduces pulmonary stasis and maintains ventilation and oxygenation), and Incentive spirometry (encourages voluntary deep breathing)
• Utilize Noninvasive ventilation to maintain positive airway pressure and improves alveolar ventilation

The Process of Using Incentive Spirometry

• Hold the spirometer upright
• Place the mouth piece in mouth and seal lips tightly
• Breathe slowly as deeply as possible
• Notice yellow piston rises to top of column, yellow indicator reaches blue outlined area
• Hold breath as long as possible, then slowly exhale allowing piston to fall to the bottom of the column
• Rest for a few seconds and repeat 1-5 10 times every hour
• Postion the yellow indicator on the left side of spirometer to show your best efforts, use indicator as a goal during each slow deep breath
• After each set of 10 deep breaths, cough to be sure lungs are clear.
• If you have incision, support your incision when coughing placing pillow firmly agaisnt
• Once you are able to get out of bed safely, take frequent walks and practice the cough

Maintenance and Promotion of Oxygenation

• Involves Oxygen therapy to prevent or relieve hypoxia
• Implement Safety precautions
• Supply oxygen throguh Tanks or wall-piped system
• Delivery occurs through -Nasal cannula -Oxygen mask

Delivery of Oxygen

• Nasal Cannulas can use a flow rate up to 6 L/min at a FIO2 range of 24-40% oxygen
  • Flow rates >4 L/min must need humidifier
  • Be aware of skin breakdown over ears and nostrils from cannula and tight application
• Oxygen Masks: Simple Face Mask is a short-term oxygen source -Has a Flow rate of 6 to 10 L/min -Levels below 5 L/min will cause rebreathing of CO2 -FIO2 ranges from 40-60% -Contraindicated for patients with conditions with CO2 retention such as COPD
• Oxygen Masks: Non-Rebreather has a flow rate of 10 L minimum
  • FIO2 range is 60-80%.
  • Valve between the bag and mask prevents exhaled air from returning into bag, this reduces rebreathing
  • Bag should at least 1/3 to 1/2 full on inspiration -Deflated bag = breathing in large amount of exhaled CO2
• Oxygen Masks: Venturi masks have
  • a Flow rate of 4 to 12 L/min depending on flow meter selected
  • FIO2 range of 24-60%

Common Respiratory Diseases - Atelectasis and Asthma

• Atelectasis: Collapse of full or partial lung (alveoli)
  • Most common cause from postsurgical procedures
  • Encourage deep breathing and incentive spirometer usage
• Asthma involves a chronic inflammatory disorder of airways
  • Leads to reversible episodes of wheezing, breathlessness, chest tightness and cough
  • Triggered by allergies, exercise, cigarette smoking, and GERD

Common Respiratory Diseases - COPD

• Chronic Obstructive Pulmonary Disease (COPD) is generally progressive -Has irreversible airflow limitations during forced exhalation due to loss of elastic recoil with an airflow is obstructed by mucous hypersecretion, mucosal edema, and bronchospasm
• Its Risk factors are cigarette smoking, Age >40 years, >10 years of smoking, and occupational chemical and dust, and air pollution.
  • COPD has two types involving chronic bronchitis and emphysema
• Oxygen therapy includes:
  • a treatment to maintain Oxygen saturation >90% during rest, exercise and sleep.
  • PaO2 greater than 60 mmHg
  • Increasing O2 saturation may lead to increased levels of CO2 and worsening outcomes
  • Treatments involve Antibiotics or other therapies to Increase exercise capacity and Improve overall survival

Questions

• Patients with a temperature of 101.5 F have rapid breathing owing to increased metabolic demands
• The earliest sign of hypoxia is restlessness
• Nurses need to closely monitor the oxygen status of an elderly patient undergoing anesthesia because decreased lung defense mechanisms may cause ineffective airway clearance
• Assist patient to cough, turn, and deep breathe every 2 hours to prevent hospital acquired pneumonia in an elderly patient

Explore the anatomy of the respiratory system, including the upper and lower respiratory tracts. Understand the roles of the intercostal muscles, pleura, and diaphragm. Learn about the conducting airways and the mechanism of respiration, focusing on inspiration.