Gas Exchange and Gas Exchange and Respiratory FunctionRespiratory Function

Part OnePart One

By Linda Self

Review of TermsReview of TermsCyanosis—influenced by polycythemia and

anemiaClubbing-Schamroth methodHemoptysisPerfusion—actual blood flow through the

circulationVentilation----movement of gas into and out

of the alveoliDiffusion—oxygen and CO2 exchanged from environment>trachea>bronchi>bronchioles

and alveoli Compliance-measure of the elasticity,

expandability, and distensibility of lungs, influenced by surfactant

Ventilation—Perfusion Ventilation—Perfusion RatiosRatiosNormal lung is 1:1Shunts: when perfusion exceeds

ventilation, a shunt exists. Blood bypasses the alveoli w/o gas exchange occurring.

Pneumonia, atelectasis, tumors, mucous plugs

Ventilation-Perfusion Ratios Ventilation-Perfusion Ratios cont.cont.

High ventilation-perfusion ratio---Dead space

Ventilation exceeds perfusionAlveoli do not have adequate

blood supply for gas exchange to occur

Pulmonary emboli, pulmonary infarction, cardiogenic shock

Ventilation-Perfusion Ratios Ventilation-Perfusion Ratios cont.cont.Silent unit—absence of

ventilation and perfusionSeen in pneumothorax and

severe ARDS

Neurologic Control of Neurologic Control of VentilationVentilationPhrenic nerveRespiratory center in medulla and

ponsCentral 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 Gerontologic ConsiderationsConsiderationsDecreased strength of

respiratory musclesDecreased elasticityIncreased respiratory dead spaceDecreased number of ciliaDecreased cough and gag reflexIncreased collagen of alveolar

walls

Respiratory AssessmentRespiratory AssessmentHealth HistoryRisk factors for respiratory disease-

genetics, smoking, allergens, occupational and recreational exposure

Dyspnea, orthopneaCough, ?productiveChest painCyanosisLung soundsClubbing—indicates chronicity

Diagnostic EvaluationDiagnostic EvaluationPFTs-assess respiratory function,

screening, assess response to therapy FVC—vital capacity performed with a

maximally forced expiratory effortForced expiratory volume—FEV1—

volume 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--Diagnostic Evaluation--ABGsABGs1. pH2. evaluate the PaCO2 and HCO3-3. Look to see if compensation has

occurred. If CO2 is >40, respiratory acidosis; If HCO3- <24, metabolic acidosis; next look at value other than primary disorder, if moving in same direction as primary value, compensation is underway.

ABG’s continuedABG’s continuedCan have two acid-base disturbances at

same timeThis can be identified when the pH does

not explain one of the changes, e.g., pH 7.2PaCO2 52HCO3 13Notice that oxygen level is not a

component in determining the acid-base balance

ABGs cont.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 >94%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

AcidosisAcidosisResults in decreased myocardial

contractility and a decreased vascular response to catecholamines. May interfere with metabolism of certain medications

AlkalosisAlkalosisCan radically impair oxygen

release from RBCs. For this reason, use bicarbonate infrequently in code situations

Other diagnostic studiesOther diagnostic studiesPulse oximetry—not reliable in severe

anemia, high CO levels, or in shockCO2 monitoring—tells us ventilation to

lungs is occurring, that CO2 is being transported to lungs, exp. CO2 indicates adequate ventilation

CulturesImaging—chest xray, CT, MRI, lung

scans (inject isotope, inhale radioactive gas), PET

BronchoscopyThoracentesisothers

Sleep ApneaSleep ApneaAssociated 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 obesityDecreased pharyngeal tone

(related to alcohol, sedatives, neuromuscular disease)

Sleep ApneaSleep ApneaDiagnosed by polysomnography

(ECG, EEG, EMG, pulse oximetry)More common in menHigh 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 Sleep Apnea signs and symptomssymptoms

Excessive daytime sleepinessFrequent nocturnal awakeningInsomniaLoud snoringMorning headachesPersonality changesSystemic hypertensionDysrhythmiasPulmonary hypertension, cor

pulmonalepolycythemia

ManagementManagementNurse educates patientAvoid alcohol and sedativesWeight lossCPAP or BiPAP—CPAP prevents

airway collapse, BiPAP makes breathing easier and results in lower airway pressure

UvulopalatopharyngoplastyTracheostomyProvigil, Provera, Diamox, Triptil may

help

Cancer of the LarynxCancer of the LarynxSquamous cell most common—95%Increasing in womenMore common in African AmericansMost common in individuals

between 50-70 years of ageCarcinogens—tobacco, alcohol,

exposure to asbestos, wood dust, cement dust, tar products, leather and metals

Most often affects glottic area

Laryngeal CancerLaryngeal CancerClinical manifestations1.Hoarseness of greater than two weeks

duration2.Persistent cough3.Sore throat4.Dysphagia5.Dyspnea6.Ulceration7.Foul breath8.Cervical adenopathy9.Weight loss10.Debilitation

Assessment and DiagnosisAssessment and DiagnosisH&PLaryngoscopy with

biopsy/staging of diseaseCT and MRI to assess adenopathy

and further stageing

Laryngeal Cancer—Laryngeal Cancer—ManagementManagement

Depends on staging of tumorOptions include surgery,

radiation and chemotherapySometimes combination therapyEnsure any dental problems

corrected, usually before other treatments

Surgical ManagementSurgical ManagementLaser surgery, supraglottic

laryngectomy, hemilaryngectomy, total laryngectomy

In case of total laryngectomy, advanced cancer present

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 CarePost-operative CareUsually ICU postopMonitor airway, VS,

hemodynamic status and comfort level

Monitor for hemorrhageMonitor for infectionMonitor tracheal stomaHave extra trach at bedside (of

same size!)

Post-operative CarePost-operative CareMay be on ventilator initiallyWill have trachEnsure humidity at all timesMay have split thickness skin graft or

trapezius or pectoralis muscle grafts—ensure side of flap or graft not in dependent position

May have PCA NG, G tube or jejunostomy tube may be

in place—nutrition importantSpeech rehab, esophageal speech,

electrolaryngesSupport group

Patients with chronic Patients with chronic obstructive pulmonary obstructive pulmonary

disordersdisordersCOPD—nonreversible Includes emphysema and chronic

bronchitisCan co-exist with asthma Present with s/s in middle life and

incidence increases with ageFVC and FEV1 decreased

Chronic BronchitisChronic BronchitisDisease of airwaysIncreased mucous production,

decreased ciliary activity, inflammation, reduced alveolar macrophage function

EmphysemaEmphysemaLobule—physiologic unit of lung consisting

of bronchiole and its branches (alveolar ducts, sacs and alveoli)

Two types—panlobar and centrilobularIn Panlobartype—destruction of

bronchiole, alveolar duct and alveoli; little inflammation, hyperexpanded chest, work on exhalation

Centrilobar type—derangement of the V/Q ratios, chronic hypoxemia, hypercapnea, polycythemia and right sided heart failure

See p. 688 for schematic

EmphysemaEmphysemaRisk factors include:1.Cigarette smoking2.Occupational dusts, chemicals,

pollution3.Deficiency of alpha1-antitrypsin,

protective enzyme that protects lung parenchyma from injury---seen in Caucasians

COPD clinical COPD clinical manifestationsmanifestationsChronic cough, sputum

production, and dyspnea on exertion (DOE)

Weight loss commonIncreased number of respiratory

infectionsIn primary emphysema, will have

“barrel chest”

Diagnosis of COPDDiagnosis of COPD

Thorough H&PSpirometry to evaluate airflow

obstructionFEV1/FVC will be less than 70%Reversibility will be testedChest xray ABGsScreening for alpha1-antitrypsin

deficiencyClassified by five stages—0 through

IV (see p. 690)

Medical ManagementMedical ManagementSmoking cessation will slow

progressionMay use Chantix, Wellbutrin,

nortriptyline, clonidineBronchodilators—beta agonists,

anticholinergics, methyxanthines, combinations, nebulized medications, inhaled and systemic corticosteroids

Influenza and pneumococcal vaccinesOxygen therapy—usually started in

severe COPDHigh fat, low CHO diet

Oxygen Therapy in COPDOxygen Therapy in COPDPreviously felt that high levels of

O2 affected hypoxic driveNow 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 Surgical Management Bullectomy—have blebs or

enlarged airspaces that do not contribute to ventilation

Lung volume reduction surgery—may improve quality of life but not life expectancy

Lung transplantation

Nursing ManagementNursing ManagementKey is educationBreathing exercisesInspiratory muscle training—

breathe against a set resistanceActivity pacing Self-care activitiesPhysical conditioningOxygen txNutritional therapyCoping measures

BronchiectasisBronchiectasisChronic, irreversible dilation of the

bronchi and bronchiolesCaused 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 pathologyTx-chest PT, smoking cessation,

continuous abx tx, possible surgical resection of affected areas

AsthmaAsthmaChronic inflammatory disease

characterized by mucosal edema, airway hyperreactivity, and mucous production

Largely reversibleAllergy is strongest predisposing

factorPoorly controlled asthma can

result in remodeling. Bronchial muscles and mucous glands enlarge, alveoli hyperinflate and subbasement fibrosis.

AsthmaAsthmaCells that play role in

inflammation of asthma include: leukotrienes, bradykinins, prostaglandins, mast cells, neutrophils, eosinophils

Beta receptor stimulation results in decrease of chemical mediators and causes bronchodilation

Three most common symptoms of asthma are cough, dyspnea and wheezing

AsthmaAsthmaFamily, environmental and

occupational history is necessaryComorbid conditions like GERD,

drug-induced asthma and allergic bronchopulmonary aspergillosis may be present

AsthmaAsthmaTriggersComplications—status asthmaticusRescue and maintenance

medicationsPeak flow monitoring—measure

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 AsthmaticusStatus AsthmaticusSevere and persistent asthma that does

not respond to conventional therapy. Can be precipitated by infection, irritants, ASA or others

Severe bronchospasm with mucous plugging leading to asphyxia

Labored breathing, engorged neck veins, cough, wheezing

ABGs indicatedO2, IV fluids, burst of steroids, short

acting corticosteroids, possibly magnesium sulfate

Nurse monitors, administers fluids and meds, ensures no irritants in environment

AtelectasisAtelectasisClosure 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

AtelectasisAtelectasisClinical manifestations—cough,

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%

AtelectasisAtelectasisPrevention—turning, mobilizing

patient, deep breathing maneuvers, incentive spirometry, secretion management such as suctioning, nebulizers, chest PT

Management—IPPB, chest PT, nebulizer tx, bronchoscopy, possible ventilator support, thoracentesis

PneumoniaPneumonia

Is an inflammation of the lung parenchyma caused by microorganisms

Community acquired—usually caused by: Strep pneumo, Hemophilus influenza, Legionella, Mycoplasma pneumoniae, Chlamydia, viral

Hospital acquired—Pseudomonas, Staph aureus, Klebsiella

PneumoniaPneumoniaPneumonia in the

immunocompromised patient—Aspergillus, Pneumocystis, Mycobacterium tuberculosis

Aspiration pneumoniaIs the most infectious disease

causing death in the United States

Pathophysiology of Pathophysiology of pneumoniapneumoniaArises when normal flora has

been aspirated, when host defenses are down or from bloodborne organisms that enter the pulmonary circulation

Affects ventilation and diffusion—will have adequate perfusion but not ventilation

Risk factors for Risk factors for PneumoniaPneumoniaConditions resulting in mucous

obstruction (cancer, smoking, COPD)ImmunosuppressionProlonged immobilityDepressed coughNPO, ETT, NG or OG tubesAlcohol intoxicationAdvanced ageMedications that depress

respirations

Clinical Manifestations of Clinical Manifestations of PneumoniaPneumonia

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

OrthopneaPurulent sputum

Diagnosis of PneumoniaDiagnosis of PneumoniaHistoryPhysical examSputum culturesBlood culturesChest xrayPossible bronchoscopy

depending on severity

Medical ManagementMedical ManagementAntibiotic depending on Gram stainOften treat empirically, intervene

promptlyCAP-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 Medical Management cont.cont.

Hospital acquired—IV antibiotics such as second generation cephalosporins, carbapenems, fluoroquinolones. If MRSA, use vancomycin, Zyvox. For Pseudomonas, use Timentin, Unasyn, and an aminoglycoside.

Viral pneumonia is supportive care only.

Hydration is important in all types.

Other treatmentsOther treatmentsAntihistaminesNasal decongestantsAntipyreticsMonitoring O2 saturation,

possibly ABGsSerial xrays

Gerontologic Gerontologic ConsiderationsConsiderationsIn 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 Nursing the patient with pneumoniapneumonia

Frequent assessment—night sweats, fever, chills, cough, lung sounds

Encourage hydration as hydration thins and loosens secretions

Humidification w/or w/o oxygenEncourage cough, chest

physiotherapyPromote restMaintain nutritionPromote patient education

Respiratory Care Respiratory Care ModalitiesModalitiesNasal cannula—up to 6L/min.

Delivers up to 42% oxygenSimple mask—flow rate 6-8L/min.

Delivers 40-60% oxygen. Partial rebreather mask—flow rate is

8-11L/min. Delivers 50-75% oxygen.Nonrebreather mask—flow at 12

L/min. Delivers 80-100% oxygen.Venturi mask—4-6 L/min, 6-8 L/min.

Deliver respective oxygen concentration of 24, 26, 28 or 30, 35, 40% oxygen. Most accurate delivery.

Respiratory Care Respiratory Care ModalitiesModalitiesOxygen Hypoxemia—decrease in arterial

oxygen tension in bloodHypoxia—decrease on oxygen supply

to tissuesOxygen toxicity—can occur if

delivering >50% for longer than 48h. Caused by free radical production.

Signs/symptoms of oxygen toxicity—paresthesias, fatigue, refractory hypoxemia, alveolar atelectasis, alveolar infiltrates

Consider alveolar collapse with high levels of oxygen

TracheostomyTracheostomySurgical procedure in which an

opening is made into the tracheaTracheostomy tubeTemporary or permanentUsed 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 Complications of tracheostomytracheostomyBleeding, pneumothorax, air

embolism, aspiration, subcutaneous or mediastinal emphysema, recurrent laryngeal nerve damage

Airway obstruction from accumulation of secretions ,tracheoesophageal fistula, tracheal ischemia

Nursing Care of the Patient Nursing Care of the Patient with Tracheostomywith Tracheostomy

Initially, semi-fowler’s position to facilitate ventilation, promote drainage, minimize edema, and prevent strain on the sutures

Allow method of communicationEnsure humidity to trachSuction secretions as neededManage cuff—usually keep pressure

less than 25 mm Hg but more than 15 mm Hg to prevent aspiration

Endotracheal IntubationEndotracheal IntubationPass ETT via nose or mouth into

tracheaMethod of choice in emergency

situationPassed with aid of a laryngoscopeETT generally has a cuff, ensure

that cuff pressure is between 15-20 mm Hg.

Use warmed, humidified oxygenShould not be used for more than

3 week

Preventing Complications Associated Preventing Complications Associated with Endotracheal and Tracheostomy with Endotracheal and Tracheostomy

TubesTubesAdminister adequate warmed humidityMaintain cuff pressure at appropriate

levelSuction as neededMaintain skin integrityAuscultate lung sounds—ETT can lodge

in right mainstem bronchusMonitor for s/s of infectionMonitor for cyanosisMaintain hydration of patientUse sterile technique when suctioning

and performing trach careMonitor O2 sat

Mechanical VentilationMechanical VentilationUsed to control patient’s

respirations, to oxygenate when patient’s ventilatory efforts are inadequate, to rest respiratory muscles

Can be positive pressure or negative pressure

Key for the nurse is assess patient—not the ventilator

Indications for Mechanical Indications for Mechanical VentilationVentilation

PaO2 <50 mm Hg with FiO2 >0.60PaO2 >50 mm Hg with pH <7.25Vital capacity < 2 times tidal volumeNegative inspiratory force < 25 cm

H20Respiratory rate > 35 bpm( *vital capacity is dependent on age,

gender, weight and body build. Usually is twice tidal volume. If < 10mL/kg, will need respiratory assist)

Classification of Ventilators—Classification of Ventilators—Negative PressureNegative 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)

Ventilators—positive Ventilators—positive pressurepressureInflate lungs by exerting positive

pressure on the airwayUsually requires trach or ETTUsed in home setting as well Pressure cycled, time cycled and

volume cycledNoninvasive positive pressure

ventilation is an option, does not require ETT

Positive Pressure Positive Pressure VentilatorsVentilatorsPressure cycled ventilators—

delivers air until reaches a preset pressure, then cycles off, then passive expiration

Can vary as patient’s airway resistance or compliance changes

Volume delivered thus will vary and may compromise ventilation

Positive Pressure Positive Pressure VentilatorsVentilatorsTime cycled rarely seen in adults

(used in newborns and infants)Volume cycled—most common.

Delivers a preset volume usually 8-10ml per kg

Noninvasive positive pressure ventilation—CPAP and BiPAP. CPAP indicated for sleep apnea, BiPAP esp. useful to avoid intubating patients and in those with neuromuscular disorders, other conditions.

Ventilator ModesVentilator ModesAssist control Intermittent mandatory controlSynchronized intermittent

mandatory ventilationPressure support—assists SIMV,

applies pressure plateau to spont. resp. during inspiratory phase

New modes incl. computerized systems

Initial Ventilator SettingsInitial Ventilator SettingsTidal volumeLowest concentration of oxygen to

maintain PaO2 80-100 mm HgPeak inspiratory pressureMode—AC or SIMV, possibly PEEPSensitivity so that patient can

trigger the vent. With minimal effortCheck ABGs after being on vent. for

20-30 minutes

Remember………..Remember………..If patient becomes agitated,

confused, tachycardic, blood pressure increases for some unexplained reason, assess for hypoxia and manually ventilate on 100%.

If patient’s heart rate slows and BP drops during suctioning, possible vagal stimulation. Stop suctioning and give 100% O2.

Bucking the ventilatorBucking the ventilatorOccurs when the patient’s

inspiration and expiration are out of synch with the ventilator

Anxiety, hypoxia, increased secretions, hypercapnia, others

Sedatives, muscle relaxants, paralytics may be necessary

Monitoring and Managing Monitoring and Managing Potential Complications Potential Complications

associated with the associated with the ventilatorventilatorSee handout

Alterations in cardiac functionBarotrauma and volutrauma

resulting in pneumothoraxVagal stimulationPulmonary infections—use

chlorhexidine gluconate in oral care

Weaning from the VentilatorWeaning from the Ventilator—criteria for weaning—criteria for weaning

Vital capacity—amount of air expired after maximum inspiration. Should be 10-15mL/kg.

Maximum inspiratory pressure-used to assess the patient’s respiratory muscle strength—should be at least -20cm H20

Tidal volume—volume of air that is inhaled or exhaled during effortless breath.

Weaning criteria cont.Weaning criteria cont.Minute ventilation—equals resp

rate times tidal volume. Normal is 6 L/min.

PaO2 greater than 60 mm Hg with FiO2 <50%, stable vital signs, adequate nutritional status

Would refrain from sedating patient during weaning

Thoracic SurgeriesThoracic SurgeriesPneumonectomyLobectomySegmental resectionLung volume reductionothers

Risk factors for thoracic Risk factors for thoracic surgery related atelectasis surgery related atelectasis

and pneumoniaand pneumoniaPreop—age, obesity, poor nutritional

status, smoking, preexisting lung disease, comorbid states

Intraoperative—thoracic incision, prolonged anesthesia

Postop—immobile, supine, inadequate pain management, prolonged intubation/ventilator, presence of NG tube, LOC, lack of education

Care of Patient after Care of Patient after ThoracotomyThoracotomy

Maintain airway clearancePositioning-lobectomy turn either

side,pneumonectomy turn on affected side, segmental resection varies per doctor

Chest tube drainage/careRelieve painPromote mobilityMaintain fluid volume and

nutrition

Care of Patient after Care of Patient after Thoracotomy—monitor and Thoracotomy—monitor and

manage potential manage potential complicationscomplications

Monitor respiratory statusVitalsFor dysrhythmiasFor bleeding, atelectasis and

infectionMonitor chest tube drainage, for

leaks, for tube kinks, for excessive drainage

Chest tube drainage Chest tube drainage systemsystem

Based on three bottle systemDrainage chamberWater sealWet or dry suctionMonitor water seal for bubblingCheck for subq emphysemaGently milk tube Occlusive dressingMonitor drainage