Gas Exchange and Respiratory Function Part One By

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 CO 2 exchanged from environment>trachea>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 Pa. O 2, then Pa. CO 2 and p. H

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 diseasegenetics, 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—FEV 1— volume of air exhaled in the specified time during the performance of forced vital capacity. FEV 1 is volume exhaled in one second. FEV 1/FVC%--ratio of timed forced exp. volume to forced vital capacity

Diagnostic Evaluation--ABGs 1. p. H 2. evaluate the Pa. CO 2 and HCO 3 3. Look to see if compensation has occurred. If CO 2 is >40, respiratory acidosis; If HCO 3 - <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 p. H does not explain one of the changes, e. g. , p. H 7. 2 Pa. CO 2 52 HCO 3 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, CO 2 35 -45 mm Hg, HCO 3 2226 m. Eq/L, O 2 80 -100 mm Hg, BE +/-2 m. Eq/L sat >94% Mixed Venous Blood: 7. 33 -7. 41, CO 2 41 -51 mm Hg, HCO 3 22 -26 m. Eq/L, O 2 35 -40 mm. Hg, BE +/- 2 m. Eq/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 CO 2 monitoring—tells us ventilation to lungs is occurring, that CO 2 is being transported to lungs, exp. CO 2 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 O 2 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 Bi. PAP—CPAP prevents airway collapse, Bi. PAP 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 5070 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 FEV 1 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 alpha 1 -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 FEV 1/FVC will be less than 70% Reversibility will be tested Chest xray ABGs Screening for alpha 1 -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 O 2 affected hypoxic drive Now thought that Haldane effect relates to ability of hgb to carry O 2 and CO 2. With increased levels of O 2, increased saturation, increased CO 2 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, drug -induced 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 O 2, 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, O 2 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 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 O 2 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 6 L/min. Delivers up to 42% oxygen Simple mask—flow rate 6 -8 L/min. Delivers 40 -60% oxygen. Partial rebreather mask—flow rate is 811 L/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 48 h. 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 O 2 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 Pa. O 2 <50 mm Hg with Fi. O 2 >0. 60 Pa. O 2 >50 mm Hg with p. H <7. 25 Vital capacity < 2 times tidal volume Negative inspiratory force < 25 cm H 20 Respiratory rate > 35 bpm ( *vital capacity is dependent on age, gender, weight and body build. Usually is twice tidal volume. If < 10 m. L/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 810 ml per kg Noninvasive positive pressure ventilation—CPAP and Bi. PAP. CPAP indicated for sleep apnea, Bi. PAP 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 Pa. O 2 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 20 -30 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% O 2.

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 10 -15 m. L/kg. Maximum inspiratory pressure-used to assess the patient’s respiratory muscle strength—should be at least 20 cm H 20 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. Pa. O 2 greater than 60 mm Hg with Fi. O 2 <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

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