Gas Exchange and Respiratory
Function
Part One

By Linda Self
Review of Terms
Cyanosis—influenced by polycythemia and anemia
Clubbing-Schamroth method
Hemoptysis
Perfusion—actual blood flow through the circulation
Ventilation----movement of gas into and out of the
alveoli
 Diffusion—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 Ratios
Normal lung is 1:1
 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 unit—absence 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 exposure
 Dyspnea, orthopnea
 Cough, ?productive
 Chest pain
 Cyanosis
 Lung sounds
 Clubbing—indicates chronicity

Diagnostic Evaluation
PFTs-assess respiratory function, screening,
assess response to therapy
 FVC—vital capacity performed with a
maximally forced expiratory effort
 Forced 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--ABGs
1. pH
 2. 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 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: 7.357.45, 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 4151 mm Hg, HCO3 22-26 mEq/L, O2 3540 mmHg, BE +/- 2mEq/L, sat 60-80%
 See chapter 14 of text

Acidosis

Results in decreased myocardial
contractility and a decreased vascular
response to catecholamines. May interfere
with metabolism of certain medications
Alkalosis

Can radically impair oxygen release from
RBCs. For this reason, use bicarbonate
infrequently in code situations
Other diagnostic studies







Pulse oximetry—not reliable in severe anemia,
high CO levels, or in shock
CO2 monitoring—tells us ventilation to lungs is
occurring, that CO2 is being transported to lungs,
exp. CO2 indicates adequate ventilation
Cultures
Imaging—chest 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
Management







Nurse educates patient
Avoid alcohol and sedatives
Weight loss
CPAP or BiPAP—CPAP 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 common—95%
Increasing in women
More common in African Americans
Most common in individuals between 50-70
years of age
Carcinogens—tobacco, alcohol, exposure to
asbestos, wood dust, cement dust, tar
products, leather and metals
Most often affects glottic area
Laryngeal Cancer
 Clinical manifestations
1. Hoarseness of greater
2. Persistent cough
3. Sore throat
4. Dysphagia
5. Dyspnea
6. Ulceration
7. Foul breath
8. Cervical adenopathy
9. Weight loss
10. Debilitation
than two weeks duration
Assessment and Diagnosis
H&P
 Laryngoscopy with biopsy/staging of
disease
 CT and MRI to assess adenopathy and
further stageing

Laryngeal Cancer—Management
Depends on staging of tumor
 Options include surgery, radiation and
chemotherapy
 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 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 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 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 important
Speech rehab, esophageal speech, electrolarynges
Support group
Patients with chronic obstructive
pulmonary disorders
COPD—nonreversible
 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

Emphysema





Lobule—physiologic unit of lung consisting of
bronchiole and its branches (alveolar ducts, sacs
and alveoli)
Two types—panlobar and centrilobular
In 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
Emphysema
Risk factors include:
1. Cigarette smoking
2. Occupational dusts, chemicals, pollution
3. 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 H&P
 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 stages—0 through IV (see
p. 690)

Medical Management






Smoking cessation will slow progression
May use Chantix, Wellbutrin, nortriptyline,
clonidine
Bronchodilators—beta agonists,
anticholinergics, methyxanthines,
combinations, nebulized medications, inhaled
and systemic corticosteroids
Influenza and pneumococcal vaccines
Oxygen therapy—usually 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
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 Management
Key is education
Breathing exercises
Inspiratory muscle training—breathe against
a set resistance
 Activity pacing
 Self-care activities
 Physical conditioning
 Oxygen tx
 Nutritional therapy
 Coping measures



Bronchiectasis





Chronic, irreversible dilation of the bronchi and
bronchioles
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
Asthma
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 fibrosis.

Asthma
Cells 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

Asthma
Family, environmental and occupational
history is necessary
 Comorbid conditions like GERD, druginduced asthma and allergic
bronchopulmonary aspergillosis may be
present

Asthma
Triggers
 Complications—status asthmaticus
 Rescue and maintenance medications
 Peak 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 Asthmaticus






Severe 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 indicated
O2, IV fluids, burst of steroids, short acting
corticosteroids, possibly magnesium sulfate
Nurse monitors, administers fluids and meds,
ensures no irritants in environment
Atelectasis
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

Atelectasis
Clinical 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%

Atelectasis
Prevention—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

Pneumonia
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

Pneumonia
Pneumonia in the immunocompromised
patient—Aspergillus, Pneumocystis,
Mycobacterium tuberculosis
 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 diffusion—will 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 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 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 assessment—night 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 cannula—up to 6L/min. Delivers up to
42% oxygen
Simple mask—flow rate 6-8L/min. Delivers
40-60% oxygen.
Partial rebreather mask—flow rate is 811L/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 Modalities
Oxygen
Hypoxemia—decrease in arterial oxygen
tension in blood
 Hypoxia—decrease on oxygen supply to
tissues
 Oxygen 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
Tracheostomy
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 ischemia

Nursing Care of the Patient with
Tracheostomy
Initially, semi-fowler’s 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 cuff—usually 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 sounds—ETT 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 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
Ventilation
PaO2 <50 mm Hg with FiO2 >0.60
 PaO2 >50 mm Hg with pH <7.25
 Vital capacity < 2 times tidal volume
 Negative inspiratory force < 25 cm H20
 Respiratory 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—
Negative 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 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 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 Ventilators
Time 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 Modes
Assist control
 Intermittent mandatory control
 Synchronized intermittent mandatory
ventilation
 Pressure support—assists 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
 Mode—AC or SIMV, possibly PEEP
 Sensitivity so that patient can trigger the
vent. With minimal effort
 Check ABGs after being on vent. for 2030 minutes

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 ventilator
Occurs 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
Potential Complications
associated with the ventilator
See handout
 Alterations in cardiac function
 Barotrauma and volutrauma resulting in
pneumothorax
 Vagal stimulation
 Pulmonary infections—use chlorhexidine
gluconate in oral care

Weaning from the Ventilator—
criteria for weaning
Vital capacity—amount of air expired
after maximum inspiration. Should be 1015mL/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.
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 Surgeries
Pneumonectomy
 Lobectomy
 Segmental resection
 Lung volume reduction
 others

Risk factors for thoracic surgery
related atelectasis and pneumonia
Preop—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 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
Thoracotomy—monitor 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
