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Gas Exchange and Respiratory Function Part One


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Title: Gas Exchange and Respiratory Function Part One

Gas Exchange and Respiratory FunctionPart One
  • By Linda Self

Review of Terms
  • Cyanosisinfluenced by polycythemia and anemia
  • Clubbing-Schamroth method
  • Hemoptysis
  • Perfusionactual blood flow through the
  • Ventilation----movement of gas into and out of
    the alveoli
  • Diffusionoxygen and CO2 exchanged from
  • environmentgttracheagtbronchigtbronchioles and
  • Compliance-measure of the elasticity,
    expandability, and distensibility of lungs,
    influenced by surfactant

VentilationPerfusion Ratios
  • Normal lung is 11
  • Shunts when perfusion exceeds ventilation, a
    shunt exists. Blood bypasses the alveoli w/o gas
    exchange occurring.
  • Pneumonia, atelectasis, tumors, mucous plugs

Ventilation-Perfusion Ratios cont.
  • High ventilation-perfusion ratio---Dead space
  • Ventilation exceeds perfusion
  • Alveoli do not have adequate blood supply for gas
    exchange to occur
  • Pulmonary emboli, pulmonary infarction,
    cardiogenic shock

Ventilation-Perfusion Ratios cont.
  • Silent unitabsence of ventilation and perfusion
  • Seen in pneumothorax and severe ARDS

Neurologic Control of Ventilation
  • Phrenic nerve
  • Respiratory center in medulla and pons
  • Central chemoreceptors in medulla, influenced by
    chemical changes in csf
  • Peripheral chemoreceptors in aortic arch and
    carotid arteries, respond first to changes in
    PaO2, then PaCO2 and pH

Gerontologic Considerations
  • Decreased strength of respiratory muscles
  • Decreased elasticity
  • Increased respiratory dead space
  • Decreased number of cilia
  • Decreased cough and gag reflex
  • Increased collagen of alveolar walls

Respiratory Assessment
  • Health History
  • Risk factors for respiratory disease-genetics,
    smoking, allergens, occupational and recreational
  • Dyspnea, orthopnea
  • Cough, ?productive
  • Chest pain
  • Cyanosis
  • Lung sounds
  • Clubbingindicates chronicity

Diagnostic Evaluation
  • PFTs-assess respiratory function, screening,
    assess response to therapy
  • FVCvital capacity performed with a maximally
    forced expiratory effort
  • Forced expiratory volumeFEV1volume of air
    exhaled in the specified time during the
    performance of forced vital capacity. FEV1 is
    volume exhaled in one second.
  • FEV1/FVC--ratio of timed forced exp. volume to
    forced vital capacity

Diagnostic Evaluation--ABGs
  • 1. pH
  • 2. evaluate the PaCO2 and HCO3-
  • 3. Look to see if compensation has occurred. If
    CO2 is gt40, respiratory acidosis If HCO3- lt24,
    metabolic acidosis next look at value other than
    primary disorder, if moving in same direction as
    primary value, compensation is underway.

ABGs continued
  • Can have two acid-base disturbances at same time
  • This can be identified when the pH does not
    explain one of the changes, e.g.,
  • pH 7.2
  • PaCO2 52
  • HCO3 13
  • Notice that oxygen level is not a component in
    determining the acid-base balance

ABGs cont.
  • Normal values for arterial gases 7.35-7.45, CO2
    35-45 mm Hg, HCO3 22-26 mEq/L, O2 80-100 mm Hg,
    BE /-2 mEq/L
  • sat gt94
  • Mixed Venous Blood 7.33-7.41, CO2 41-51 mm Hg,
    HCO3 22-26 mEq/L, O2 35-40 mmHg, BE /- 2mEq/L,
    sat 60-80
  • See chapter 14 of text

  • Results in decreased myocardial contractility and
    a decreased vascular response to catecholamines.
    May interfere with metabolism of certain

  • Can radically impair oxygen release from RBCs.
    For this reason, use bicarbonate infrequently in
    code situations

Other diagnostic studies
  • Pulse oximetrynot reliable in severe anemia,
    high CO levels, or in shock
  • CO2 monitoringtells us ventilation to lungs is
    occurring, that CO2 is being transported to
    lungs, exp. CO2 indicates adequate ventilation
  • Cultures
  • Imagingchest xray, CT, MRI, lung scans (inject
    isotope, inhale radioactive gas), PET
  • Bronchoscopy
  • Thoracentesis
  • others

Sleep Apnea
  • Associated with frequent, loud snoring with
    breathing cessation for 10 seconds or long, at
    least 5 episodes per hour, followed by awakening
    by a snort when O2 levels drop
  • May be associated with obesity
  • Decreased pharyngeal tone (related to alcohol,
    sedatives, neuromuscular disease)

Sleep Apnea
  • Diagnosed by polysomnography (ECG, EEG, EMG,
    pulse oximetry)
  • More common in men
  • High risk for CAD, cerebrovascular disease and
    premature death.
  • Results in hypoxia and hypercapnia which trigger
    sympathetic response. Can lead to dysrhythmias
    and elevated BP

Sleep Apnea signs and symptoms
  • Excessive daytime sleepiness
  • Frequent nocturnal awakening
  • Insomnia
  • Loud snoring
  • Morning headaches
  • Personality changes
  • Systemic hypertension
  • Dysrhythmias
  • Pulmonary hypertension, cor pulmonale
  • polycythemia

  • Nurse educates patient
  • Avoid alcohol and sedatives
  • Weight loss
  • CPAP or BiPAPCPAP prevents airway collapse,
    BiPAP makes breathing easier and results in lower
    airway pressure
  • Uvulopalatopharyngoplasty
  • Tracheostomy
  • Provigil, Provera, Diamox, Triptil may help

Cancer of the Larynx
  • Squamous cell most common95
  • Increasing in women
  • More common in African Americans
  • Most common in individuals between 50-70 years of
  • Carcinogenstobacco, alcohol, exposure to
    asbestos, wood dust, cement dust, tar products,
    leather and metals
  • Most often affects glottic area

Laryngeal Cancer
  • Clinical manifestations
  • Hoarseness of greater than two weeks duration
  • Persistent cough
  • Sore throat
  • Dysphagia
  • Dyspnea
  • Ulceration
  • Foul breath
  • Cervical adenopathy
  • Weight loss
  • Debilitation

Assessment and Diagnosis
  • HP
  • Laryngoscopy with biopsy/staging of disease
  • CT and MRI to assess adenopathy and further

Laryngeal CancerManagement
  • Depends on staging of tumor
  • Options include surgery, radiation and
  • Sometimes combination therapy
  • Ensure any dental problems corrected, usually
    before other treatments

Surgical Management
  • Laser surgery, supraglottic laryngectomy,
    hemilaryngectomy, total laryngectomy
  • In case of total laryngectomy, advanced cancer
  • Laryngeal structures removed including portion of
    trachea. Results in permanent loss of voice and
    permanent tracheostomy
  • Often will have radical neck dissection involves
    removal of sternocleidomastoid muscle, lymph
    nodes, jugular vein, surrounding soft tissue

Post-operative Care
  • Usually ICU postop
  • Monitor airway, VS, hemodynamic status and
    comfort level
  • Monitor for hemorrhage
  • Monitor for infection
  • Monitor tracheal stoma
  • Have extra trach at bedside (of same size!)

Post-operative Care
  • May be on ventilator initially
  • Will have trach
  • Ensure humidity at all times
  • May have split thickness skin graft or trapezius
    or pectoralis muscle graftsensure side of flap
    or graft not in dependent position
  • May have PCA
  • NG, G tube or jejunostomy tube may be in
    placenutrition important
  • Speech rehab, esophageal speech, electrolarynges
  • Support group

Patients with chronic obstructive pulmonary
  • COPDnonreversible
  • Includes emphysema and chronic bronchitis
  • Can co-exist with asthma
  • Present with s/s in middle life and incidence
    increases with age
  • FVC and FEV1 decreased

Chronic Bronchitis
  • Disease of airways
  • Increased mucous production, decreased ciliary
    activity, inflammation, reduced alveolar
    macrophage function

  • Lobulephysiologic unit of lung consisting of
    bronchiole and its branches (alveolar ducts, sacs
    and alveoli)
  • Two typespanlobar and centrilobular
  • In Panlobartypedestruction of bronchiole,
    alveolar duct and alveoli little inflammation,
    hyperexpanded chest, work on exhalation
  • Centrilobar typederangement of the V/Q ratios,
    chronic hypoxemia, hypercapnea, polycythemia and
    right sided heart failure
  • See p. 688 for schematic

  • Risk factors include
  • Cigarette smoking
  • Occupational dusts, chemicals, pollution
  • Deficiency of alpha1-antitrypsin, protective
    enzyme that protects lung parenchyma from
    injury---seen in Caucasians

COPD clinical manifestations
  • Chronic cough, sputum production, and dyspnea on
    exertion (DOE)
  • Weight loss common
  • Increased number of respiratory infections
  • In primary emphysema, will have barrel chest

Diagnosis of COPD
  • Thorough HP
  • Spirometry to evaluate airflow obstruction
  • FEV1/FVC will be less than 70
  • Reversibility will be tested
  • Chest xray
  • ABGs
  • Screening for alpha1-antitrypsin deficiency
  • Classified by five stages0 through IV (see p.

Medical Management
  • Smoking cessation will slow progression
  • May use Chantix, Wellbutrin, nortriptyline,
  • Bronchodilatorsbeta agonists, anticholinergics,
    methyxanthines, combinations, nebulized
    medications, inhaled and systemic corticosteroids
  • Influenza and pneumococcal vaccines
  • Oxygen therapyusually started in severe COPD
  • High fat, low CHO diet

Oxygen Therapy in COPD
  • Previously felt that high levels of O2 affected
    hypoxic drive
  • Now thought that Haldane effect relates to
    ability of hgb to carry O2 and CO2. With
    increased levels of O2, increased saturation,
    increased CO2 load w/o being able to expel it.
    So, increased hypercapnia.

Surgical Management
  • Bullectomyhave blebs or enlarged airspaces that
    do not contribute to ventilation
  • Lung volume reduction surgerymay improve quality
    of life but not life expectancy
  • Lung transplantation

Nursing Management
  • Key is education
  • Breathing exercises
  • Inspiratory muscle trainingbreathe against a set
  • Activity pacing
  • Self-care activities
  • Physical conditioning
  • Oxygen tx
  • Nutritional therapy
  • Coping measures

  • Chronic, irreversible dilation of the bronchi and
  • Caused by inflammation d/t recurrent infections
    damaging bronchial walls, thick sputum and
    decreased mucociliary clearance genetic
    disorders like CF, idiopathic causes
  • Results in atelectasis, fibrosis, VQ mismatch
  • R/O TB or other pathology
  • Tx-chest PT, smoking cessation, continuous abx
    tx, possible surgical resection of affected areas

  • Chronic inflammatory disease characterized by
    mucosal edema, airway hyperreactivity, and
    mucous production
  • Largely reversible
  • Allergy is strongest predisposing factor
  • Poorly controlled asthma can result in
    remodeling. Bronchial muscles and mucous glands
    enlarge, alveoli hyperinflate and subbasement

  • Cells that play role in inflammation of asthma
    include leukotrienes, bradykinins,
    prostaglandins, mast cells, neutrophils,
  • Beta receptor stimulation results in decrease of
    chemical mediators and causes bronchodilation
  • Three most common symptoms of asthma are cough,
    dyspnea and wheezing

  • Family, environmental and occupational history is
  • Comorbid conditions like GERD, drug-induced
    asthma and allergic bronchopulmonary
    aspergillosis may be present

  • Triggers
  • Complicationsstatus asthmaticus
  • Rescue and maintenance medications
  • Peak flow monitoringmeasure highest airflow
    during a forced expiration. See asthma action
    plan on p. 715. Height, age and sex are variables
    to consider in personal best determination.

Status Asthmaticus
  • Severe and persistent asthma that does not
    respond to conventional therapy. Can be
    precipitated by infection, irritants, ASA or
  • Severe bronchospasm with mucous plugging leading
    to asphyxia
  • Labored breathing, engorged neck veins, cough,
  • ABGs indicated
  • O2, IV fluids, burst of steroids, short acting
    corticosteroids, possibly magnesium sulfate
  • Nurse monitors, administers fluids and meds,
    ensures no irritants in environment

  • Closure of collapse of alveoli
  • Often occurs in postoperative setting and in
    those who are immobilized
  • Can result from any obstruction that blocks air
    to and from alveoli

  • Clinical manifestationscough, sputum, low grade
    fever. In severe cases, tachycardia, tachypnea,
    central cyanosis
  • Chest xray may reveal patchy infiltrates,
    crackles will be heard over affected area, O2
    saturation may be lower than 90

  • Preventionturning, mobilizing patient, deep
    breathing maneuvers, incentive spirometry,
    secretion management such as suctioning,
    nebulizers, chest PT
  • ManagementIPPB, chest PT, nebulizer tx,
    bronchoscopy, possible ventilator support,

  • Is an inflammation of the lung parenchyma caused
    by microorganisms
  • Community acquiredusually caused by Strep
    pneumo, Hemophilus influenza, Legionella,
    Mycoplasma pneumoniae, Chlamydia, viral
  • Hospital acquiredPseudomonas, Staph aureus,

  • Pneumonia in the immunocompromised
    patientAspergillus, Pneumocystis, Mycobacterium
  • Aspiration pneumonia
  • Is the most infectious disease causing death in
    the United States

Pathophysiology of pneumonia
  • Arises when normal flora has been aspirated, when
    host defenses are down or from bloodborne
    organisms that enter the pulmonary circulation
  • Affects ventilation and diffusionwill have
    adequate perfusion but not ventilation

Risk factors for Pneumonia
  • Conditions resulting in mucous obstruction
    (cancer, smoking, COPD)
  • Immunosuppression
  • Prolonged immobility
  • Depressed cough
  • NPO, ETT, NG or OG tubes
  • Alcohol intoxication
  • Advanced age
  • Medications that depress respirations

Clinical Manifestations of Pneumonia
  • Not possible to diagnose a certain type by
    manifestations alone
  • May be sudden in onset with fever, chills and
    pleuritic pain as seen in pneumococcal pneumonia
  • May be gradual in onset with low grade fever, HA,
    pleuritic pain, myalgias and pharyngitis
  • Orthopnea
  • Purulent sputum

Diagnosis of Pneumonia
  • History
  • Physical exam
  • Sputum cultures
  • Blood cultures
  • Chest xray
  • Possible bronchoscopy depending on severity

Medical Management
  • Antibiotic depending on Gram stain
  • Often treat empirically, intervene promptly
  • CAP-tx with Zithromax, Biaxin, doxy, or
    fluoroquinolone. With comorbidities, may use
    Augmentin, Vantin, Ceftin, and a macrolide or
    doxy. Symmetrel for Flu A, Tamiflu for Flu A/B.
    Bactrim for PCP.

Medical Management cont.
  • Hospital acquiredIV antibiotics such as second
    generation cephalosporins, carbapenems,
    fluoroquinolones. If MRSA, use vancomycin, Zyvox.
    For Pseudomonas, use Timentin, Unasyn, and an
  • Viral pneumonia is supportive care only.
  • Hydration is important in all types.

Other treatments
  • Antihistamines
  • Nasal decongestants
  • Antipyretics
  • Monitoring O2 saturation, possibly ABGs
  • Serial xrays

Gerontologic Considerations
  • In elderly the classic s/s of cough, chest pain,
    sputum production and fever may be absent
  • May be difficult to distinguish heart failure
    from pneumonia
  • Xrays particularly helpful in this population

Nursing the patient with pneumonia
  • Frequent assessmentnight sweats, fever, chills,
    cough, lung sounds
  • Encourage hydration as hydration thins and
    loosens secretions
  • Humidification w/or w/o oxygen
  • Encourage cough, chest physiotherapy
  • Promote rest
  • Maintain nutrition
  • Promote patient education

Respiratory Care Modalities
  • Nasal cannulaup to 6L/min. Delivers up to 42
  • Simple maskflow rate 6-8L/min. Delivers 40-60
  • Partial rebreather maskflow rate is 8-11L/min.
    Delivers 50-75 oxygen.
  • Nonrebreather maskflow at 12 L/min. Delivers
    80-100 oxygen.
  • Venturi mask4-6 L/min, 6-8 L/min. Deliver
    respective oxygen concentration of 24, 26, 28 or
    30, 35, 40 oxygen. Most accurate delivery.

Respiratory Care Modalities
  • Oxygen
  • Hypoxemiadecrease in arterial oxygen tension in
  • Hypoxiadecrease on oxygen supply to tissues
  • Oxygen toxicitycan occur if delivering gt50 for
    longer than 48h. Caused by free radical
  • Signs/symptoms of oxygen toxicityparesthesias,
    fatigue, refractory hypoxemia, alveolar
    atelectasis, alveolar infiltrates

  • Consider alveolar collapse with high levels of

  • Surgical procedure in which an opening is made
    into the trachea
  • Tracheostomy tube
  • Temporary or permanent
  • Used to bypass an upper airway obstruction, allow
    removal of tracheobronchial secretions, permit
    long term use of mechanical ventilation, to
    prevent aspiration in unconscious patient or to
    replace endotracheal tube

Complications of tracheostomy
  • Bleeding, pneumothorax, air embolism, aspiration,
    subcutaneous or mediastinal emphysema, recurrent
    laryngeal nerve damage
  • Airway obstruction from accumulation of
    secretions ,tracheoesophageal fistula, tracheal

Nursing Care of the Patient with Tracheostomy
  • Initially, semi-fowlers position to facilitate
    ventilation, promote drainage, minimize edema,
    and prevent strain on the sutures
  • Allow method of communication
  • Ensure humidity to trach
  • Suction secretions as needed
  • Manage cuffusually keep pressure less than 25 mm
    Hg but more than 15 mm Hg to prevent aspiration

Endotracheal Intubation
  • Pass ETT via nose or mouth into trachea
  • Method of choice in emergency situation
  • Passed with aid of a laryngoscope
  • ETT generally has a cuff, ensure that cuff
    pressure is between 15-20 mm Hg.
  • Use warmed, humidified oxygen
  • Should not be used for more than 3 week

Preventing Complications Associated with
Endotracheal and Tracheostomy Tubes
  • Administer adequate warmed humidity
  • Maintain cuff pressure at appropriate level
  • Suction as needed
  • Maintain skin integrity
  • Auscultate lung soundsETT can lodge in right
    mainstem bronchus
  • Monitor for s/s of infection
  • Monitor for cyanosis
  • Maintain hydration of patient
  • Use sterile technique when suctioning and
    performing trach care
  • Monitor O2 sat

Mechanical Ventilation
  • Used to control patients respirations, to
    oxygenate when patients ventilatory efforts are
    inadequate, to rest respiratory muscles
  • Can be positive pressure or negative pressure
  • Key for the nurse is assess patientnot the

Indications for Mechanical Ventilation
  • PaO2 lt50 mm Hg with FiO2 gt0.60
  • PaO2 gt50 mm Hg with pH lt7.25
  • Vital capacity lt 2 times tidal volume
  • Negative inspiratory force lt 25 cm H20
  • Respiratory rate gt 35 bpm
  • ( vital capacity is dependent on age, gender,
    weight and body build. Usually is twice tidal
    volume. If lt 10mL/kg, will need respiratory

Classification of VentilatorsNegative Pressure
  • Used for patients with polio, muscular dystrophy,
    ALS, myasthenia gravis
  • Examples include the iron lung chamber, pneumo
    wrap and tortoise shell (portable devices with
    rigid shell to create a negative pressure)

Ventilatorspositive pressure
  • Inflate lungs by exerting positive pressure on
    the airway
  • Usually requires trach or ETT
  • Used in home setting as well
  • Pressure cycled, time cycled and volume cycled
  • Noninvasive positive pressure ventilation is an
    option, does not require ETT

Positive Pressure Ventilators
  • Pressure cycled ventilatorsdelivers air until
    reaches a preset pressure, then cycles off, then
    passive expiration
  • Can vary as patients airway resistance or
    compliance changes
  • Volume delivered thus will vary and may
    compromise ventilation

Positive Pressure Ventilators
  • Time cycled rarely seen in adults (used in
    newborns and infants)
  • Volume cycledmost common. Delivers a preset
    volume usually 8-10ml per kg
  • Noninvasive positive pressure ventilationCPAP
    and BiPAP. CPAP indicated for sleep apnea, BiPAP
    esp. useful to avoid intubating patients and in
    those with neuromuscular disorders, other

Ventilator Modes
  • Assist control
  • Intermittent mandatory control
  • Synchronized intermittent mandatory ventilation
  • Pressure supportassists SIMV, applies pressure
    plateau to spont. resp. during inspiratory phase
  • New modes incl. computerized systems

Initial Ventilator Settings
  • Tidal volume
  • Lowest concentration of oxygen to maintain PaO2
    80-100 mm Hg
  • Peak inspiratory pressure
  • ModeAC or SIMV, possibly PEEP
  • Sensitivity so that patient can trigger the vent.
    With minimal effort
  • Check ABGs after being on vent. for 20-30 minutes

  • If patient becomes agitated, confused,
    tachycardic, blood pressure increases for some
    unexplained reason, assess for hypoxia and
    manually ventilate on 100.
  • If patients heart rate slows and BP drops during
    suctioning, possible vagal stimulation. Stop
    suctioning and give 100 O2.

Bucking the ventilator
  • Occurs when the patients inspiration and
    expiration are out of synch with the ventilator
  • Anxiety, hypoxia, increased secretions,
    hypercapnia, others
  • Sedatives, muscle relaxants, paralytics may be

Monitoring and Managing Potential Complications
associated with the ventilator
  • See handout
  • Alterations in cardiac function
  • Barotrauma and volutrauma resulting in
  • Vagal stimulation
  • Pulmonary infectionsuse chlorhexidine gluconate
    in oral care

Weaning from the Ventilatorcriteria for weaning
  • Vital capacityamount of air expired after
    maximum inspiration. Should be 10-15mL/kg.
  • Maximum inspiratory pressure-used to assess the
    patients respiratory muscle strengthshould be
    at least -20cm H20
  • Tidal volumevolume of air that is inhaled or
    exhaled during effortless breath.

Weaning criteria cont.
  • Minute ventilationequals resp rate times tidal
    volume. Normal is 6 L/min.
  • PaO2 greater than 60 mm Hg with FiO2 lt50, stable
    vital signs, adequate nutritional status
  • Would refrain from sedating patient during weaning

Thoracic Surgeries
  • Pneumonectomy
  • Lobectomy
  • Segmental resection
  • Lung volume reduction
  • others

Risk factors for thoracic surgery related
atelectasis and pneumonia
  • Preopage, obesity, poor nutritional status,
    smoking, preexisting lung disease, comorbid
  • Intraoperativethoracic incision, prolonged
  • Postopimmobile, supine, inadequate pain
    management, prolonged intubation/ventilator,
    presence of NG tube, LOC, lack of education

Care of Patient after Thoracotomy
  • Maintain airway clearance
  • Positioning-lobectomy turn either
    side,pneumonectomy turn on affected side,
    segmental resection varies per doctor
  • Chest tube drainage/care
  • Relieve pain
  • Promote mobility
  • Maintain fluid volume and nutrition

Care of Patient after Thoracotomymonitor and
manage potential complications
  • Monitor respiratory status
  • Vitals
  • For dysrhythmias
  • For bleeding, atelectasis and infection
  • Monitor chest tube drainage, for leaks, for tube
    kinks, for excessive drainage

Chest tube drainage system
  • Based on three bottle system
  • Drainage chamber
  • Water seal
  • Wet or dry suction
  • Monitor water seal for bubbling
  • Check for subq emphysema
  • Gently milk tube
  • Occlusive dressing
  • Monitor drainage
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