Caring for patients in respiratory failure Even if you don’t work in an ICU, you’re likely to encounter patients in respiratory failure.
By Michelle Fournier, MN, RN, CCRN-K
RESPIRATORY FAILURE is one of lungs to deflate. With normal Respiration—the process of ex - the most common reasons for ad - breathing, expiration is purely pas - changing oxygen (O 2) and carbon mission to the intensive care unit sive. But with exercise or forced dioxide (CO 2)—involves ventilation, (ICU) and a common comorbidity expiration, expiratory muscles (in - oxygenation, and gas transport; the in patients admitted for acute care. cluding the abdominal wall and in - ventilation/perfusion (V/Q) relation - What’s more, it’s the leading cause ternal intercostal muscles) become ship; and control of breathing. Res - of death from pneumonia and active. These important muscles are piration is regulated by chemical chronic obstructive pulmonary dis - necessary for coughing. and neural control systems, includ - ease (COPD) in the United States. ing the brainstem, peripheral and This article briefly reviews the central chemoreceptors, and physiologic components of respira - mechanoreceptors in skeletal mus - tion, differentiates the main types of cle and joints. (See Control of respiratory failure, and discusses breathing .) medical treatment and nursing care A dynamic process, ventilation is for patients with respiratory failure. affected by the respiratory rate (RR) and tidal volume—the amount of Physiologic components of air inhaled and exhaled with each ventilation and respiration breath. Pulmonary ventilation refers The lung is highly elastic. Lung in - to the total volume of air inspired flation results from the partial pres - or expired per minute. sure of inhaled gases and the diffu - Not all inspired air participates in sion-pressure gradient of these gas exchange. Alveolar ventila - gases across the alveolar-capillary tion—the volume of air entering membrane. The lungs play a pas - alveoli taking part in gas ex - sive role in breathing, but ventila - CNE change—is the most important vari - tion requires muscular effort. When 1.32 contact able in gas exchange. Air that dis - the diaphragm contracts, the tho - hours tributes to the conducting airways racic cavity enlarges, causing the is deemed dead space or wasted air LEARNING OBJECTIVES lungs to inflate. During forced in - because it’s not involved in gas ex - spiration when a large volume of 1. Discuss the physiology of ventila - change. (See Oxygenation and gas tion and respiration. air is inspired, external intercostal transport .) muscles act as a second set of in - 2. Differentiate the types of respirato - Ultimately, effective ventilation ry failure. spiratory muscles. is measured by the partial pressure 3. Describe the treatment of respira - Accessory muscles in the neck of CO in arterial blood (Pa CO ). tory failure. 2 2 and chest are the last group of in - All expired CO 2 comes from alveo - spiratory muscles, used only for The author and planners of this CNE activity have lar gas. During normal breathing, deep and heavy breathing, such as disclosed no relevant financial relationships with the breathing rate or depth adjusts any commercial companies pertaining to this during intense exercise or respirato - activity. See the last page of the article to learn to maintain a steady Pa CO 2 be - ry failure. During expiration, the di - how to earn CNE credit. tween 35 and 45 mm Hg. Hyper - aphragm relaxes, decreasing tho - Expiration: 11/1/17 ventilation manifests as a low racic cavity size and causing the Pa CO 2; hypoventilation, as a high
American Nurse Today Volume 9, Number 11 www.AmericanNurseToday.com 18 Pa CO 2. During exercise or certain disease states, increasing breathing Control of breathing depth is far more effective than in - Breathing is controlled by carefully integrated neurologic, chemical, and mechani - creasing the RR in improving alve - cal processes. The neurologic respiratory center in the brain’s medulla is sensitive to olar ventilation. carbon dioxide (CO 2) and hydrogen-ion concentrations in body fluids. It can com - pensate to changing conditions within seconds to minutes.
Lung recoil and compliance • Acidemia (decreased blood pH) or elevated partial pressure of arterial CO 2 stim - The lungs, airways, and vascular ulates the respiratory center, which increases respiratory rate or depth. This, in trees are embedded in elastic tis - turn, reduces the CO 2 level and increases blood pH. sue. To inflate, the lung must • Alkalemia (increased blood pH) inhibits the respiratory center, resulting in slow - stretch to overcome these elastic er or more shallow breathing, CO 2 retention, and reduced blood pH. components. Elastic recoil —the Usually, the lungs can compensate for respiratory and metabolic imbalances. lung’s ability to return to its origi - But when lung dysfunction is severe or the metabolic imbalance is prolonged, the nal shape after stretching from in - lungs can’t fully compensate and renal compensation is required. However, renal halation—relates inversely to com - compensation is slow, taking hours to days. pliance . Lung compliance indirectly Interruption of or damage to respiratory structures or respiratory control mech - reflects lung stiffness or resistance anism ultimately affects the ability to exchange gases effectively and can lead to to stretch. A stiff lung, as in pul - such disorders as chronic obstructive pulmonary disease, interstitial lung disease, monary fibrosis, is less compliant and respiratory failure. than a normal lung. With reduced compliance, more work is required to produce a nor - Clinical indicators of acute respi - COPD exacerbation is a classic ex - mal tidal volume. With extremely ratory failure include: ample of V/Q mismatching. Shunt - high compliance, as in emphysema • partial pressure of arterial oxy - ing, which occurs in virtually all where there is loss of alveolar and gen (Pa O2) below 60 mm Hg, or acute lung diseases, involves alveo - elastic tissue, the lungs inflate ex - arterial oxygen saturation as lar collapse or fluid-filled alveoli. tremely easily. Someone with em - measured by pulse oximetry Examples of type 1 respiratory fail - physema must expend a lot of ef - (Sp O2) below 91% on room air ure include pulmonary edema fort to get air out of the lungs • Pa CO 2 above 50 mm Hg and pH (both cardiogenic and noncardio - because they don’t recoil back to below 7.35 genic), pneumonia, influenza, and their normal position during expi - • Pa O2 decrease or Pa CO 2 increase pulmonary hemorrhage. (See Ven - ration. In both pulmonary fibrosis of 10 mm Hg from baseline in tilation and perfusion: A critical and emphysema, inadequate lung patients with chronic lung dis - relationship .) ventilation leads to hypercapnic ease (who tend to have higher Type 2 , or hypercapnic, respira - respiratory failure. Pa CO 2 and lower PaO 2 baseline tory failure, is defined as failure to values than other patients). exchange or remove CO 2, indicated Respiratory failure In contrast, chronic respiratory by Pa CO 2 above 50 mm Hg. Pa - Respiratory failure occurs when failure is a long-term condition that tients with type 2 respiratory failure one of the gas-exchange func - develops over time, such as with who are breathing room air com - tions—oxygenation or CO 2 elimina - COPD. Manifestations of chronic monly have hypoxemia. Blood pH tion—fails. A wide range of condi - respiratory failure are less dramatic depends on the bicarbonate level, tions can lead to acute respiratory and less apparent than those of which is influenced by hypercapnia failure, including drug overdose, acute failure. duration. Any disease that affects respiratory infection, and exacerba - alveolar ventilation can result in tion of chronic respiratory or car - Three main types of respiratory type 2 respiratory failure. Common diac disease. failure causes include severe airway disor - Respiratory failure may be The most common type of respira - ders (such as COPD), drug over - acute or chronic. In acute failure, tory failure is type 1 , or hypoxemic dose, chest-wall abnormalities, and life-threatening derangements in respiratory failure (failure to ex - neuromuscular disease. arterial blood gases (ABGs) and change oxygen), indicated by a Type 3 respiratory failure (also acid-base status occur, and pa - Pa O2 value below 60 mm Hg with called perioperative respiratory tients may need immediate intuba - a normal or low Pa CO 2 value. In failure) is a subtype of type 1 and tion. Respiratory failure also may ICU patients, the most common results from lung or alveolar at - be classified as hypoxemic or causes of type 1 respiratory failure electasis. General anesthesia can hypercapnic. are V/Q mismatching and shunts. cause collapse of dependent lung
www.AmericanNurseToday.com November 2014 American Nurse Today 19 Oxygenation and gas transport
A gas consists of individual molecules in constant random mo - The oxyhemoglobin curve depicts O 2 binding to Hgb in tion. These molecules bombard the walls of any vessel con - the lung and O 2 unloading in the tissues. Body temperature, taining them, exerting pressure against the wall. The pressure blood acidity, and underlying conditions, such as anemia or exerted is proportional to gas temperature and concentration. chronic hypoxia, may influence the efficiency of this process.
How gas exchange occurs Factors affecting gas diffusion across the respiratory Movement of gases—oxygen (O 2) and carbon dioxide membrane (CO 2)—into and out of the alveoli and cells occurs by simple The following factors affect the rate of gas diffusion across diffusion, defined as passive movement of molecules from an the respiratory (alveolar-capillary) membrane. area of higher concentration to one of lower concentration. • Membrane thickness. The diffusion rate is inversely propor - The distance across the capillary wall and the lubricating plas - tional to the thickness of the respiratory membrane. Such ma layer measures about 1 micron—roughly 100 times small - conditions as pulmonary edema, excessive sputum, and fi - er than a single human hair. This short distance allows quick, brosis thicken the membrane, lengthening the distance re - effective exchange of O 2 and CO 2 across the alveolar-capillary quired to cross the membrane. membrane. • Surface area. The lung’s large surface area is influenced by Hemoglobin (Hgb) transports O 2 from the lungs to the tis - alveolar size and inflation. Surface area is directly propor - sues. Every 100 mL of blood that passes through the tissues tional to diffusion; a large surface area favors diffusion. delivers about 4 mL of O 2. Where O 2 pressure is high, oxygen Clinical conditions that reduce surface area include atelec - combines loosely with the heme portion of hemoglobin in the tasis and such procedures as lobectomy. lung, forming oxyhemoglobin. When oxyhemoglobin reaches • Gas solubility and molecular weight. Each gas has an in - the tissues, where O 2 pressure is low, hemoglobin releases O 2. herent solubility and molecular weight. The diffusion rate The illustration below shows the basic process of gas of a gas is directly proportional to its solubility and in - exchange. versely proportional to its molecular weight. Although CO 2 weighs more than O 2, it’s more soluble and diffuses 20 times faster. Damage to the respiratory membrane im - pairs O 2 diffusion capacity but may not affect CO 2 diffu - sion. Therefore, in disease states, the partial pressure of O2 in arterial blood (Pa O2) decreases before the partial pressure of CO 2 in arterial blood (Pa CO 2) changes. So pa - tients with pulmonary diseases that interfere with diffu - sion develop problems related to hypoxemia before they start retaining CO 2. • Driving pressure. In the lung, driving pressure is the gradi - ent between Pa O2 or Pa CO 2 in the alveoli and the pressure of these gases in the blood. In the tissues, driving pressure is the difference between Pa O2 and Pa CO 2 in the capillaries compared to pressures in tissue cells. In the alveolus, O 2 driving pressure is 64 mm Hg; CO 2 driving pressure is only 5 mm Hg. Because CO 2 is more soluble, it doesn’t need a high driving pressure. Administering supplemental O 2 in - creases driving pressure. alveoli. Patients most at risk for up to 40% of cardiac output may diaphoresis, accessory muscle use, type 3 respiratory failure are those flow to the respiratory muscles. diminished lung sounds, inability to with chronic lung conditions, ex - speak in full sentences, an impend - cessive airway secretions, obesity, Signs and symptoms of ing sense of doom, and an altered immobility, and tobacco use, as respiratory failure mental status. The patient may as - well as those who’ve had surgery Patients with impending respiratory sume the tripod position in an at - involving the upper abdomen. failure typically develop shortness tempt to further expand the chest Type 3 respiratory failure also of breath and mental-status changes, during the inspiratory phase of res - may occur in patients experienc - which may present as anxiety, tach y - piration. In chronic respiratory fail - ing shock, from hypoperfusion of p nea, and decreased Sp O2 despite ure, the only consistent clinical in - respiratory muscles. Normally, less increasing amounts of supplemen - dictor is protracted shortness of than 5% of total cardiac output tal oxygen. breath. flows to respiratory muscles. But Acute respiratory failure may Be aware that pulse oximetry in pulmonary edema, lactic acido - cause tachycardia and tachypnea. measures the percentage of hemo - sis, and anemia (conditions that Other signs and symptoms include globin saturated with oxygen, but commonly arise during shock), periorbital or circumoral cyanosis, it doesn’t give information about
American Nurse Today Volume 9, Number 11 www.AmericanNurseToday.com 20 Ventilation and perfusion: A critical relationship For adequate organ and tissue oxygenation, ventilation (V, the may result. Causes of extreme V/Q mismatching include: amount of air reaching the alveoli) should match perfusion (Q, • shunting, in which alveolar perfusion is normal but venti - the amount of blood reaching the alveoli). Although ventila - lation is absent tion and perfusion to the lungs aren’t distributed uniformly, • dead space—portions of the respiratory tract where air they tend to match: Where ventilation is maximal, blood flow doesn’t participate in gas exchange is maximal, and vice versa. The V/Q ratio reflects the matching • nonperfused lung areas. of these two components. A low V/Q ratio occurs when pulmonary gas exchange is Because air rises, alveoli in the apex of each lung are always impaired—a situation that typically causes hypoxemia. Carbon partially inflated and thus don’t accommodate much further dioxide (CO ) excretion also is impaired, which can lead to in - ventilation. The lung bases, on the other hand, have a much 2 creased partial pressure of CO in arterial blood ( Pa CO ). How - lower alveolar pressure and ventilate more readily than the 2 2 ever, this is rare because increased Pa CO typically triggers res - apices. The low pulmonary arterial pressure is just enough to 2 piratory stimulation and increased alveolar ventilation, which pump blood to the top of the lung. Although all parts of the returns Pa CO to normal. This scenario is most common in pa - lung receive some perfusion, hydrostatic pressure in the vas - 2 tients with chronic bronchitis, asthma, and acute pulmonary culature directs most of the blood flow through the lower (de - edema. pendent) portion of the lung. So when a person sits or stands, On the other hand, a high V/Q ratio occurs when a well- blood flow to the lung bases exceeds blood flow to the apices. ventilated lung area is poorly perfused; ventilation is wasted Balancing ventilation and perfusion as it fails to oxygenate the blood. The most common cause is The lung uses hypoxic vasoconstriction to balance ventilation pulmonary embolism, which impairs blood flow. A high V/Q and perfusion. When a lung region becomes hypoxic, small ar - ratio also may occur in emphysema due to air trapping. teries feeding that region sense hypoxia in alveolar gas and con - These illustrations show what happens with a normal V/Q strict in response. Constriction redirects blood away from the ratio, a low V/Q ratio, a very low V/Q ratio (shunt), and a high hypoxic region to better-oxygenated lung areas. When a V/Q V/Q ratio. mismatch or imbalance occurs, as from lung disease, hypoxemia
www.AmericanNurseToday.com November 2014 American Nurse Today 21 To detect changes in oxygen delivery to the tissues or defense mechanisms. Clinicians the patient’s ventilatory function. should consider nutritional support So be sure to consider the patient’s respiratory status and individualize such support to entire clinical presentation. Com - ensure adequate caloric and pro - pared to Sp O2, an ABG study pro - tein intake to meet the patient’s vides more accurate information early, assess the patient’s respiratory needs. on acid-base balance and blood oxygen saturation. Capnography is tissue oxygenation Patient and family education another tool used for monitoring Provide appropriate education to patients receiving anesthesia and the patient and family to promote in critical care units to assess a pa - status regularly. adherence with treatment and help tient’s respiratory status. It directly prevent the need for readmission. monitors inhaled and exhaled con - Explain the purpose of nursing centration of CO 2 and indirectly quate coronary artery perfusion. In measures, such as turning and in - monitors Pa CO 2. addition, stay alert for conditions centive spirometry, as well as med - that can impair O 2 delivery, such ications. At discharge, teach pa - Treatment and management as elevated temperature, anemia, tients about pertinent risk factors In acute respiratory failure, the impaired cardiac output, acidosis, for their specific respiratory condi - healthcare team treats the underly - and sepsis. tion, when to return to the health - ing cause while supporting the pa - As indicated, take steps to im - care provider for follow-up care, tient’s respiratory status with sup - prove V/Q matching, which is cru - and home measures they can take plemental oxygen, mechanical cial for improving respiratory effi - to promote and maximize respira - ventilation, and oxygen saturation ciency. To enhance V/Q matching, tory function. O monitoring. Treatment of the un - turn the patient on a regular and derlying cause, such as pneumonia, timely basis to rotate and maxi - Selected references COPD, or heart failure, may require mize lung zones. Because blood Cooke CR, Erikson SE, Eisner MD, Martin diligent administration of antibi - flow and ventilation are distrib - GS. Trends in the incidence of noncardio - otics, diuretics, steroids, nebulizer uted preferentially to dependent genic acute respiratory failure: the role of race. Crit Care Med . 2012;40(5):1532-8. treatments, and supplemental O 2 as lung zones, V/Q is maximized on appropriate. the side on which the patient is Gehlbach BK, Hall JB. Respiratory failure and mechanical ventilation. In Porter RS, ed. For chronic respiratory failure, lying. The Merck Manual . 19th ed. West Point, PA; despite the wide range of chronic Regular, effective use of incen - Merck Sharp & Dohme Corp.; 2011. or end-stage pathology present tive spirometry helps maximize dif - Kaynar AM. Respiratory failure treatment and (such as COPD, heart failure, or fusion and alveolar surface area management. Updated August 14, 2014. systemic lupus erythematosus with and can help prevent atelectasis. http://emedicine.medscape.com/article/16798 lung involvement), the mainstay of Regular rotation of V/Q lung zones 1-treatment#aw2aab6b6b2. Accessed August treatment is continuous supplemen - by patient turning and reposition - 23, 2014. tal O , along with treatment of the ing enhances diffusion by promot - Kress JP, Hall JB: Approach to the patient 2 with critical illness. In Longo DL, Fauci AS, underlying cause. ing a healthy, well-perfused alveo - Kasper DL, et al., eds. Harrison’s Principles lar surface. These actions, as well of Internal Medicine . 18th ed. New York, Nursing care as suctioning, help mobilize spu - NY: McGraw-Hill Professional; 2012. Nursing care can have a tremen - tum or secretions. Pinson R. Revisiting respiratory failure, part dous impact in improving efficien - 1. ACP Hosp . 2013;Oct:5-6. www.acphospi - cy of the patient’s respiration and Nutritional support talist.org/archives/2013/10/coding.htm. Ac - ventilation and increasing the Patients in respiratory failure have cessed August 23, 2014. chance for recovery. To detect unique nutritional needs and con - Pinson R. Revisiting respiratory failure, part changes in respiratory status early, siderations. Those with acute respi - 2. ACP Hosp . 2013;Nov:7-8. www.acphospi - talist.org/archives/2013/11/coding.htm. Ac - assess the patient’s tissue oxygena - ratory failure from primary lung cessed October 3, 2014. tion status regularly. Evaluate ABG disease may be malnourished ini - Schraufnagel D. Breathing in America: Dis - results and indices of end-organ tially or may become malnourished eases, Progress, and Hope . American Tho - perfusion. Keep in mind that the from increased metabolic demands racic Society; 2010. brain is extremely sensitive to O 2 or inadequate nutritional intake. supply; decreased O 2 can lead to Malnutrition can impair the func - Michelle Fournier is director of clinical consulting an altered mental status. Also, tion of respiratory muscles, reduce with Nuance/J.A. Thomas & Associates in Atlanta, know that angina signals inade - ventilatory drive, and decrease lung Georgia.
American Nurse Today Volume 9, Number 11 www.AmericanNurseToday.com 22 CNE Caring for patients in respiratory failure POST-TEST • CNE: 1.32 contact hours Earn contact hour credit online at www.AmericanNurseToday.com/ContinuingEducation.aspx
Instructions ANA Center for Continuing Education and Professional Development’s To take the post-test for this article and earn contact hour credit, please accredited provider status refers only to CNE activities and does not im - go to the blue link above. Simply use your Visa or MasterCard to pay ply that there is real or implied endorsement of any product, service, or the processing fee. (ANA members $15; nonmembers $20.) Once company referred to in this activity nor of any company subsidizing you’ve successfully passed the post-test and completed the evalua - costs related to the activity. The planners and author of this CNE activity tion form, you’ll be able to print out your certificate immediately . have disclosed no relevant financial relationships with any commercial companies pertaining to this CNE. Provider accreditation The American Nurses Association’s Center for Continuing Education and Professional Development is accredited as a provider of continuing PURPOSE /GOAL nursing education by the American Nurses Credentialing Center’s To provide nurses with information on how to better care for Commission on Accreditation. ANCC Provider Number 0023. patients in respiratory failure. Contact hours: 1.32 ANA’s Center for Continuing Education and Professional Development LEARNING OBJECTIVES is approved by the California Board of Registered Nursing, Provider 1. Discuss the physiology of ventilation and respiration. Number CEP6178 for 1.58 contact hours. 2. Differentiate the types of respiratory failure. 3. Describe the treatment of respiratory failure. Post-test passing score is 75%. Expiration: 11/1/17
Please mark the correct answer 4. Which of the following clinical 8. Which type of respiratory failure online. findings indicate acute respiratory results from lung or alveolar atelectasis? failure? a. Postoperative 1. Which statement about the a. Partial pressure of CO in arterial blood b. Perioperative respiratory center’s response to changes 2 (Pa CO 2) above 50 mm Hg and pH c. Hypercapnic in carbon dioxide (CO 2) and hydrogen-ion below 7.35 d. Hypoxemic concentration is correct? b. Pa CO below 50 mm Hg and pH above a. The respiratory center can compen - 2 9. Signs and symptoms of impending 7.35 respiratory failure include: sate for changes in hours or days. c. Partial pressure of arterial oxygen b. The respiratory center can compen - a. bradypnea. (Pa O ) increase of 10 mm Hg from sate for changes in seconds or minutes. 2 b. tachypnea. baseline in patients with chronic lung c. bradycardia. c. Alkalemia stimulates the respiratory disease center. d. increased Sp O2. d. Pa CO 2 decrease of 10 mm Hg from d. Acidemia inhibits the respiratory cen - baseline in patients with chronic lung 10. Which statement about pulmonary ter. disease care for patients with respiratory failure is accurate? 2. The most important variable in gas 5. Which statement about ventilation exchange is: a. V/Q matching is minimized on the side and perfusion is correct? on which the patient is lying. a. amount of wasted air. a. When a lung region becomes hypoxic, b. amount of dead space. b. Incentive spirometry should be used small arteries constrict in response. sparingly. c. bronchial ventilation. b. When a lung region becomes hypoxic, d. alveolar ventilation. c. Regular turning helps improve V/Q small arteries dilate in response. matching. 3. Which statement about lung c. A high ventilation/perfusion (V/Q) ratio d. Slight decreases in temperature can compliance is correct? occurs when pulmonary gas exchange impair O delivery. a. Compliance is not related to the work is impaired. 2 it takes to breathe. d. A low V/Q ratio occurs when a well- 11. Which statement about the nutritional b. High compliance is associated with ventilated lung area is poorly perfused. needs of patients with respiratory failure is less work required to breathe. correct? 6. In which type of respiratory failure do a. Malnutrition can increase ventilatory c. Elastic recoil relates inversely to patients who are breathing room air compliance. drive. commonly have hypoxemia? b. Malnourishment typically is not a d. Elastic recoil relates directly to a. Type 1 compliance. problem. b. Type 2 c. Nutritional support requirements are c. Type 3 universal. d. Type 4 d. Increased metabolic demands can 7. Shunting and V/Q mismatching are cause malnourishment. common causes of which type of respiratory failure? a. Postoperative b. Perioperative c. Hypercapnic d. Hypoxemic
www.AmericanNurseToday.com November 2014 American Nurse Today 23