18.3: Factors Affecting Cardiopulmonary Function
By the end of this section, you will be able to:
- Examine physiological considerations for impaired cardiopulmonary function
- Recognize lifestyle and behavioral pattern considerations for impaired cardiopulmonary function
- Remember diagnostic testing used to monitor cardiopulmonary functioning
In the upcoming section, pathophysiology is considered, as impaired cardiopulmonary function is examined. Nonmodifiable and modifiable influences can have significant impacts on cardiopulmonary function and are thus considered risk factors. Age and genetics are examples of nonmodifiable risk factors, as the alterations or changes to the cardiopulmonary system are unavoidable. Risk factors that are modifiable include behaviors and lifestyle choices, so whether a person is active and follows a diet that helps prevent negative cardiopulmonary changes is considered modifiable. Sometimes such positive behaviors are successful at halting or slowing processes like the development of hypertension, obesity, or hyperlipidemia.
In health care, it is often considered more beneficial to take a proactive approach and focus on the prevention of medical diseases and diagnoses, rather than waiting for a reactive response. Patients who have an understanding of their own health status and play an active role in their care are more inclined to seek preventive care and screenings, thereby avoiding preventable illness, or obtaining care early. Some such patients are able to minimize dysfunction of the cardiopulmonary system.
A variety of diagnostic tests assist healthcare providers in the identification of abnormalities, whether through preventive screenings or prompt recognition. Depending on the test, providers can monitor the progress of the disease or the effectiveness of treatment, whether medical, surgical, or pharmacological. Care plans can therefore be evaluated and redesigned based on individual patient status and goals of the patient and healthcare team.
Physiological Considerations for Impaired Cardiopulmonary Function
Homeostasis is a delicate balance, and minute changes can lead to slight or major changes physiologically. In the case of cardiopulmonary function, such alterations may affect either of the interrelated systems. Nonmodifiable risk factors for impaired cardiopulmonary function include advancing age, genetics, race, family history, and health status. Modifiable risk factors include physical inactivity, smoking, diet, and obesity.
Nurses need to anticipate such alterations and be prepared to act on changes. In many situations, proactive actions can make a huge difference, sometimes even more than reactive responses to an already symptomatic problem (Agency for Healthcare Research and Quality [AHRQ] PSNet, 2019). This section explores several factors that are likely to have effects on the cardiopulmonary system, followed by diagnostic testing that is used to monitor the function of this inescapably intertwined set of systems.
Age
Some cardiovascular changes within the heart, vessels, and blood occur naturally with age. Within the heart structure, the sinoatrial (SA) node can lose cells, and fat deposits and fibrous tissues can develop causing the SA node to fire at a slightly lower HR. In some people, enlargement of the left ventricle can occur with age, causing the chamber to hold less blood. Arrhythmias can develop, such as A-fib, caused by types of heart disease. Deposits of lipofuscin, degeneration of heart cells, and thickened heart valves can cause a heart murmur from turbulent blood flow within the heart.
In the blood vessels, baroreceptors can become less sensitive with aging, causing dizziness or orthostatic hypotension . Capillary walls may thicken, slowing the rate of exchange of nutrients and oxygen for waste and carbon dioxide. The aorta can thicken and stiffen, creating an increase in BP and cardiac hypertrophy.
A reduction in body water increases the viscosity of blood, causing a decrease in blood volume. Red blood cells are produced at a slower rate, delaying the body’s response to anemia or blood loss. A decrease in neutrophils reduces the body’s immune response to infection.
Aging also affects the pulmonary system. Aging lungs lose elastic recoil, causing small airway collapse and decreased alveolar surface area, decreasing lung compliance . Spirometry changes include a decrease in total lung capacity, an increase in residual volume, and a decrease in the vital capacity of the lungs. In the chest wall cavity, conditions such as osteoporosis, arthritis, calcification of the thoracic spine, and changes to intercostal muscles can increase chest wall rigidity. The chest wall can become barrel shaped to compensate for a loss of lung elasticity, causing the diaphragm to flatten and become less efficient.
Genetics
There are genetic disorders that affect the pulmonary and/or cardiovascular systems. Research has identified several such inherited cardiovascular diagnoses and described them as vascular, cardiomyopathies, or involving arrhythmias (Musunuru et al., 2020). For example, elevated lipids can be difficult to treat for some individuals; familial hypercholesterolemia may be the genetic source of this dyslipidemia.
A rather common example of a vascular genetic disorder is Marfan syndrome, which is often associated with excessive height and other long bones like those of the hands and feet. However, Marfan syndrome also frequently impacts blood vessels, including the aorta. The risk of aortic aneurysm and possible dissection is a major concern with this genetic diagnosis (Musunuru et al., 2020). Another genetic disorder, Loeys-Dietz syndrome, is similar to Marfan syndrome, as it impacts connective tissues and can cause aortic aneurysm and potential dissection.
Long QT syndrome and bradycardia syndrome are arrhythmias associated with genetics, although there are other possible causes, including certain medications (Musunuru et al., 2020). Genetic cardiomyopathies include several of the muscular dystrophies, including Duchenne, limb-girdle, and Emery-Dreifuss. Dilated and hypertrophic cardiomyopathies can also be rooted in genetics.
More than sixty genes have been identified as involved in at least a dozen pulmonary syndromes (Brigham and Women’s Hospital, 2023). One of the most common breathing disorders is asthma, and for some sufferers, the cause is genetic. Many of the pulmonary syndromes are rather rare. Pulmonary syndromes are distinguished by those associated with cysts (causing the formation of abnormal cysts), fibrosis (causing abnormal, scar-like tissue), or bronchiectasis (causing dilated airways).
While rare and involving organs other than the lungs, cystic fibrosis (CF) is perhaps best recognized as a lung disorder; it is considered a bronchiectatic syndrome (Brigham and Women’s Hospital, 2023). CF causes mucus to become thick and sticky, with respiratory secretions among those affected; this can cause airway limitations and difficulty breathing. Pulmonary fibrosis and pulmonary hypertension are both fibrotic genetic disorders. Alpha-1 antitrypsin deficiency is a genetic cystic pulmonary disorder that affects the lungs and potentially the liver. Alpha-1 antitrypsin deficiency involves symptoms similar to those of emphysema, and indeed patients may progress to an emphysema diagnosis (Brigham and Women’s Hospital, 2023).
Health Status
The status of one’s health at baseline can be critical for outcomes when faced with any sort of alteration of normal physiological function. Those people who are generally healthy when there is a challenging event, whether illness, injury, or emotional stress, have a far better chance of confronting the event with little physiological decline or residual effect. Conversely, someone whose baseline is poor health, as reflected by multiple comorbidities (multiple medical diagnoses), is at a disadvantage as far as withstanding the challenging event.
The metabolic syndrome is an example of a cluster of diseases (including hypertension, high blood sugar levels, a large waistline or apple shape, high triglycerides, and low HDL cholesterol) that occur together, increasing the likelihood of developing heart disease. Some patients are not identified as having the syndrome, as they experience only one or two of the diagnoses. There are certain disorders that commonly cluster together like those of metabolic syndrome, with the possibility of additive effects from the multiple disorders identified. Several comorbidities have been identified with frequent prevalence in patients with cardiopulmonary disorders. The four cardiopulmonary diagnoses isolated in this research were HF, peripheral arterial disease (PAD), coronary heart disease (CHD), and stroke. DM, COPD, and low vision were identified as the comorbidities with the most statistically significant impact on the development of the disorders.
The interaction of comorbidities and their contribution to the diagnoses can be exemplified (Buddeke et al., 2019):
- DM is also associated with the development of microvascular damage, which can play a part in vision problems, as well as hypertension and PAD.
- Hyperlipidemia is a frequent contributor to intravascular plaque development, hypertension, and ultimately significant heart disease that may lead to MI and/or stroke. MI is a common cause of HF.
- COPD is often associated with cigarette smoking; impaired gas exchange is one of the common results. The cardiovascular system is also likely to be impacted, resulting in MI and/or stroke.
Medications
Medications are prescribed for any number of reasons, and they are not without potential for problems. Drugs have desired effects and side effects. Sometimes, side effects are negative or even dangerous, referred to as adverse effects. Following are some examples of medications that have the potential to negatively affect the cardiovascular or pulmonary systems, or both.
Often, medications to treat one problem can lead to another. An example is the antidysrhythmic class of drugs. Most of these drugs are accompanied by a warning they may cause other dysrhythmias. Amiodarone is one such drug, as there is a risk for cardiac rhythm changes. Amiodarone may also affect the pulmonary system, with pulmonary fibrosis (Penn Medicine, 2023) and acute respiratory distress syndrome possible.
Chemotherapeutic agents, typically for the treatment of cancers, are associated with many side and adverse effects, some of which can be very uncomfortable or toxic to body systems. Cyclophosphamide, an alkylating antineoplastic is one such drug, with the potential to cause pulmonary fibrosis and cardiotoxicity. While cyclophosphamide’s impact on the cardiac system is considered reversible, another cardiotoxic chemotherapy drug, daunorubicin, has a cumulative effect with dosing, and therefore a maximum dose. To avoid cardiac problems such as HF, daunorubicin is carefully considered with regard to the type of cancer, type of previous treatment, and total dose administered in the past.
Lifestyle and Behavior Patterns
Lifestyle and behavior patterns include decisions people make about dietary choices, habits they acquire, activities they involve themselves in, and the level of activity in which they participate. Such behaviors have a significant influence on health and wellness in a general and holistic way, and certainly, there are important considerations when one looks particularly at the cardiopulmonary system . As mentioned previously with discussion of overall health status, there are a variety of pathophysiological changes and medical diagnoses that are more likely to occur when certain lifestyles are lived and behaviors are selected, especially when these are habitual and/or frequent.
Smoking contributes to a number of diseases of the lungs, heart, and vessels. Constant exposure to chemicals in the lungs, mouth, and larynx can cause abnormal cells to divide and cause cancer. Smoking causes a disruption of the mucociliary elevator in the lungs, which can lead to increased colonization of bacteria in the lower respiratory tract and frequent infections. It also causes atherosclerosis , increasing a person’s chances for CHD, hypertension, stroke, peripheral artery disease, and abdominal aortic aneurysm (CDC, 2020).
Scenario: Patient is a 15-year-old named Richard, who has been vaping for the past year. The patient has been to see the primary care provider on a monthly basis for “a cold” that doesn’t improve, over the past four months.
Patient: I suppose you’re going to lecture me.
Nurse: I doubt lecturing will be helpful. Unless you think it would be.
Patient: My parents gripe at me all the time about it. Doesn’t do anything. Just makes me more pissed off.
Nurse: Exactly.
Patient: Yeah. Won’t do anything.
Nurse: What I would like to do is tell you a bit about the cold you’ve had so long, that won’t go away.
Patient: Yeah. Why won’t the doctor give me something to fix it?
Nurse: That’s the problem. What you’ve got going on is not a cold, but what your body’s doing from the vaping. It looks like your lungs aren’t happy about this, and what seems like a cold is your lungs trying to recover after each time you use your vape pen.
Patient: But my friends don’t have any problems with it.
Nurse: Maybe they don’t yet. Or maybe some of them never will. But the problem is, you’re here today and have been before because your lungs aren’t taking it well. And what the doctor can do is help you cut down and stop if you’ll give it a chance. If today’s not the day, I’d like to ask you to come in again to see me in a week. That way, you can think about it, read this pamphlet, and if you have questions, write them down. I’ll answer them next week.
Patient: It probably won’t help, but I’ll take the paper and see you in a week.
Choices about one’s diet are also major contributors to pathophysiological changes, and this can be from deficits or excesses. Some people make decisions about avoiding certain foods and end up with disorders related to certain nutritional deficits. Electrolytes are a good example of nutrients that, like acid-base balance, must be maintained within the established window of normal ranges for proper metabolic function. Sodium is an electrolyte often first considered for its concerns when levels are high or low. Either abnormality may present with neurological changes, perhaps some mild confusion, but can be far more extreme, and/or long lasting. Sodium retention is associated with water retention, so elevated plasma sodium tends to cause hypervolemia and hypertension. Potassium can cause devastating problems if it is not kept in range: if elevated or decreased, minor symptoms may be apparent, or ultimately dysrhythmias are possible, and may be deadly. Phosphate is another electrolyte and is often overlooked for its importance in metabolic function. Recall that cellular energy involves ATP, and the P is phosphate. Therefore, without adequate levels of phosphate, ATP production is reduced. With functions as critical as those of the respiratory and cardiac systems, a constant supply of energy is necessary.
Perhaps more often considered as a nutritional abnormality is overconsumption, especially when the proper combination of necessary nutrients is not part of the diet. Rather, consumption is not only excessive but may involve improper dietary intake, such as sweetened beverages and snacks, high-sodium meals and snacks, and a lack of balance of essential dietary sources. This results in not only higher weight but also malnutrition. Overeating and subsequent higher weight may involve hyperlipidemia or be associated with hypertension or type 2 DM. Or it may be related to excessive sodium intake, and associated fluid retention and hypertension.
Physical Activity Level
One of the behaviors with an impact on cardiopulmonary function is physical activity. At least 150 minutes of moderate aerobic exercise activity weekly is recommended by the AHA (2023) to maintain and possibly improve health status and avoid complications. The success of the AHA recommendations appears to lie in patients making exercise habitual and incorporating other healthy living activities into these new lifestyle choices.
Improved circulation is one of the major benefits of increased activity, as it maximizes oxygenation and perfusion , and all body systems reap the benefits, from improved neurological function to enhanced elasticity of blood vessels and improved BP, to normalizing lipid levels and reducing atherosclerotic plaque formation and CAD.
Cultural Influences
Whether conscious of it or not, cultural influence is within the very fabric of people’s lives. From birth, it surrounds people, and throughout the life span, it influences and guides relationships and decisions in so many ways. With regard to the cardiopulmonary system , culture may have effects on acceptance of medical advice and the healthcare system, dietary choices and traditions, how and what activities are accepted and utilized, emotional and societal support systems, and stress levels (Acare Pro, 2023).
Culture determines dietary habits. Many people in the United States, for example, continue the practice of consuming meals with meat as the primary component, potatoes or another starchy carbohydrate as a major side dish, and a small helping of vegetables. This high-calorie diet, combined with a sedentary lifestyle, increases the likelihood of weight gain; higher weight is a risk factor for cardiovascular disorders.
Adding spices for flavor is another example of cultural influence, with some adding hot and savory spices, while others minimize additive flavors. Salt is an extremely common and popular spice, and processed foods like lunch meats and canned soups tend to have high sodium content, which is contraindicated for some, particularly with cardiac conditions like hypertension and HF.
Some cultures embrace complementary alternative medicine practices, while others are more skeptical. Herbal remedies, and the notion of whether a food or beverage should be consumed at a certain temperature, are important in certain cultural settings (Acare Pro, 2023). Some drugs may be recommended to be taken on an empty stomach, or with food, and cultural influences may interfere with either medical instruction. Communication is impactful herein, as misunderstandings are possible and lead to a lack of treatment and worsening of the health condition.
While the likelihood that the exploration of influences of culture upon health status, and cardiopulmonary health in particular, could continue with many more exemplars, the final example here is that of medical care. Cultural perspectives prompt a variety of attitudes about health care (Acare Pro, 2023): is it embraced openly and fully, or approached with extreme caution? This may be demonstrated by whom patients choose for their health care. Do they require their provider to be a well-educated physician, a naturopathic practitioner, or a neighborhood healer whose training was obtained informally but is well accepted in the area? The preference and selection as to which expertise is sought may be from cultural mores over years or perhaps even decades or longer. If patients are distrustful of medical practitioners, they are again less likely to follow recommended treatment plans.
Environmental Influences
Environmental stressors can have a negative impact on cardiopulmonary health. Living in the city can intensify these stressors. Examples of environmental stressors include air pollution, noise and light pollution, wildfires, and climate change (Münzel et al., 2021). The cardiovascular and pulmonary systems are both susceptible to these environmental influences.
Noise, especially that related to traffic, can possibly increase the risk of hypertension, MI, and stroke (Münzel et al., 2021). The premise is related to the stress response, with increased release of cortisol and catecholamines causing the signs and symptoms associated with stress. This includes SNS stimulation and often results in elevated HR and BP. If sustained, such stress-associated manifestations have the potential to lead to MI and stroke. Climate change is also implicated in contributing to stress-related changes, such as cardiac strain and sleep disturbances, as well as inflammatory responses to airborne pollutants such as dust and wildfire smoke (Münzel et al., 2021).
Air pollution is identified as a contributor to cardiovascular disease itself, as sources such as automobile exhaust or burning of fossil fuels release chemicals into the air (Münzel et al., 2021). Such chemicals can cause mild irritation or an allergic response or may be toxic and lead to inflammatory and immune responses, and infections. With long-standing exposure, CAD can develop, with the risk of ACS including MI and ultimately HF or death. Dysrhythmias and stroke are also potential results from exposure to air pollutants.
Environmental influences on the pulmonary system focus on a variety of means of damaging lungs through accelerated aging and reducing cellular healing abilities (Eckhardt & Wu, 2021). Means of pulmonary damage include inflammation, oxidation, damage to DNA, and cellular dysfunction, including impaired healing. Environmental exposures may also cause allergic responses, which can vary from mild to severe.
Environmental exposures to such substances toxic to the respiratory system include tobacco smoke, combustion of fossil fuels, and automobile exhaust. Tobacco smoke contains numerous chemicals, which can cause mild results like inflammation or may be carcinogenic. Burning of fossil fuels releases sulfur and nitrogen dioxide (among other chemicals), which contribute to pulmonary damage (Eckhardt & Wu, 2021). Employment-related exposure may also include populations who mine granite or sandstone and are therefore exposed to silica dust, and coal miners, who are exposed to coal dust and at risk for pneumoconiosis (“black lung”). Mesothelioma is another possible lung disorder related to environmental exposure to asbestos.
Diagnostic Testing Used to Monitor Cardiopulmonary Functioning
As varied as the potential dysfunctions of the cardiopulmonary system may be, so too are the diagnostic tests used to determine what is happening with a patient, and the extent of the dysfunction(s). Such testing may be invasive or noninvasive, may concentrate on the cardiovascular system or the respiratory system, and may provide information about general function (or lack thereof), infection, or injury.
Cultures
Cultures are obtained to identify whether an infection of some sort is present by growing particular microbes in the laboratory. Varied sources can be cultured, including samples of blood, sputum, urine, or swabs from a wound or throat (MedlinePlus, 2023). Not only can cultures verify the presence of bacteria in general, but identification of which bacteria are present is typically provided. Other microbes may also be cultured, including mycobacterium (the specific type of bacteria that causes tuberculosis), viruses, and fungi.
Cultures are routinely allowed to grow for forty-eight to seventy-two hours; particularly virulent microbes often grow quickly and are clearly identified within forty-eight hours. To ensure accuracy in results, some cultures are grown for longer periods. Examples include bacteria cultures incubated for up to five days, fungal cultures for up to four weeks, and mycobacterial cultures for three to eight weeks (Van Leeuwen & Bladh, 2023).
In addition to culture, for treatment purposes, sensitivity is often ordered. This offers identification of a particular bacteria and exposes the microbes to various antibacterial drugs to distinguish the drugs that are effective, most effective, or ineffective in reducing or eliminating the microorganism(s). For what is anticipated to be a simple infection, the healthcare provider may order merely a culture, but sensitivity results can be extremely helpful in narrowing broad-spectrum antibacterials to effective but narrower-spectrum drugs. Hospitalized patients frequently have complicated infections, and bacterial resistance is a reality, so it is common for healthcare providers to order the culture and sensitivity (C&S) at the time of the original order.
Blood
Blood cultures are ordered when sepsis is suspected. In many facilities, laboratory personnel draw blood samples for blood cultures to avoid contamination of the sample. With some infections, pathogens are only found in the blood intermittently, so a series of three or more blood cultures, as well as blood draws from different veins, may be performed to increase the chance of finding the infection.
Blood cultures (Figure 18.14) are incubated for several days before being reported as negative. Some types of bacteria and fungi grow more slowly than others and/or may take longer to detect if initially present in low numbers.
A positive result indicates bacteria have been found in the blood (bacteremia). Other types of pathogens, such as a fungus or a virus, may also be found in a blood culture. When a blood culture is positive, the specific microbe causing the infection is identified, and susceptibility testing is performed to inform the healthcare provider which antibiotics or other medications are most likely to be effective for treatment.
Sputum
A sputum culture is a diagnostic test that evaluates the type and number of bacteria present in sputum. The patient is asked to cough deeply and spit any mucus that comes up into a sterile specimen container. The sample is sent to a laboratory where it is placed in a special dish (Figure 18.15) and is watched for two to three days or longer to see if bacteria or other disease-causing germs grow. Acid-fast bacillus testing, along with C&S testing, is used to diagnose tuberculosis (TB). When testing for TB, at least three consecutive samples are collected, with at least one being an early morning sample.
Blood Gases
Blood gases are done to acquire information as to a patient’s oxygenation and acid-base balance. This includes pH, partial pressure of CO 2 (PaCO 2 ), partial pressure of O 2 (PaO 2 ), O 2 saturation (SaO 2 ), bicarbonate (HCO 3 ), and base excess (the amount of base present in the blood).
Blood gas samples are drawn with a specific heparinized syringe that only needs a small sample of blood. In years past, the syringe had to be placed on ice and sent to the laboratory for testing. Now it is more common to use a point-of-care device called an iSTAT. From the syringe, blood is placed into the receiving area of an iSTAT cartridge, which is then placed into the analyzer. Within approximately two minutes, the results are available.
Arterial
Arterial blood gases (ABG) are measured by collecting blood from an artery , rather than a vein , and are most commonly collected via the radial artery. Acquiring an ABG requires training and is often painful for the patient. Therefore, this test is not done on a routine basis and is not typical for a stable patient. In severe illness, however, with a patient whose O 2 status is questionable or at risk, the information from an ABG can provide the necessary results for guiding immediate care and planning ongoing interventions.
While some components of blood gas testing are closely correlated between an arterial and venous sample, those indicative of oxygenation (PaCO 2 , PaO 2 ) are most reliable if the source is arterial (Lentz et al., 2019). Acid-base information: pH, HCO 3 , and base excess (or deficit) demonstrate a reasonable correlation between arterial and venous samples. For accuracy in the results of bicarbonate, a plasma sample for specific chemistry should be obtained, as it is not a measured value as part of a blood gas (Lentz et al., 2019).
Scenario: The patient is Gloria, who is 74-years-old; her history includes emphysema and frequent urinary tract infections. She was brought to the hospital by her son, who found her sitting in her recliner, very confused. She is now in the ICU, and the nurse is preparing to draw an ABG. Her son, Reggie, is in the room with her.
Nurse: Gloria, I need to get a blood sample from your wrist.
Patient: MmmHmm. Oh, what? Who?
Nurse: I’m going to put a needle in your wrist for a blood sample. Reggie, would you sit on that side of her and hold her hand?
Patient's son She already has an IV in her arm. Won’t that work?
Nurse: This is different, this sample has to come from her artery. I want to use the one on the inside, where we often feel for a pulse, the radial artery. This will tell us more about why she was so quiet and confused when you found her, and why she’s still like that. And if her emphysema is worse now.
Patient's son Oh, okay. I think she had that last time. She was on a respirator, you know, about three months ago. Her breathing got real bad.
Nurse: Yes, I’ll bet you’re right. She probably had this done then, too. So, I’m going to draw from her right side, and if you can just hold her left hand and let her know you’re here. Try to keep her still, so she doesn’t jump or pull away when she feels the stick. The results only take a couple of minutes, so we’ll have a better idea of things when I call the doctor with the results. Thanks for your help.
Venous
Venous blood gas (VBG) acquisition is considered less painful than an arterial sample; veins tend to be more superficially located and are often visible and/or palpable. Arteries are deeper and the puncture for an ABG is done blindly, based on palpation. Occasionally, while attempting an ABG, a venous sample is accidentally obtained, or a mixture of arterial and venous blood. In such a circumstance, the results may provide inadequate information. Because a VBG is less painful to draw, if the physician is attempting to determine acuity versus chronicity, hypercarbia, or whether the problem has a respiratory or metabolic cause (Lentz et al., 2019), a VBG may be ordered.
Cardiac Biomarkers
There are three major cardiac biomarkers: creatine kinase (CK), troponin I, and creatine kinase myocardial band (CK-MB). CK-MB and troponin I are the two tests commonly ordered when a MI is suspected, or an exacerbation of HF. CK-MB is elevated within four to six hours after an MI, peaks within twenty-four hours, and normalizes within seventy-two hours (Van Leeuwen et al., 2023). Troponin I levels rise between two and six hours post-MI, followed by two peaks—the first between fifteen and twenty-four hours postinjury, and again at sixty to eighty hours after injury.
Another cardiac biomarker that is used to diagnose HF is the brain natriuretic peptide (BNP). BNP is used not only for initial diagnostic purposes but also to manage ongoing treatment, assess progression of HF, and evaluate patients during exacerbations (Van Leeuwen & Bladh, 2023). BNP rises when a stretch of the heart occurs from hypervolemia, and so as the congestive nature of HF increases, so does this peptide.
Capnography
Two methods are used to monitor ventilation and oxygenation: capnography (the amount of CO 2 at the end of exhalation) and pulse oximeter , respectively. Since capnography measures exhaled CO 2 , it is also referred to as end-tidal CO 2 (ETCO 2 ); the normal range is 35 to 45 mm Hg (Sullivan, 2020). Commonly, patients whose medical condition indicates the necessity for ETCO 2 monitoring are critically ill. Patients in low perfusion states (e.g., shock, hypovolemia) may be candidates for capnography, as healthcare providers are seeking specific information about ventilatory status and the ability of the tissues to access circulating O 2 . It can also be a helpful tool for monitoring interventions and modifying treatment promptly (Sullivan, 2020).
Capnography can be done with a special type of nasal cannula, which can deliver O 2 and obtain ETCO 2 results. Or the nasal prongs can be in place while a patient is receiving O 2 by mask (simple, continuous positive airway pressure [CPAP], or nonrebreather). There is also an attachment that can be used in conjunction with the ventilator for mechanically ventilated patients to be continuously monitored. There are specific monitors for ETCO 2 , whether static or portable, and specific settings, as capnography is done by anesthesia providers during surgery, and in ICUs it is monitored by nurses in addition to continuous monitoring of other vital functions, like pulse oximetry, RR, HR, and BP. The waveform depicts the respiratory cycle and indicates the amount of CO 2 at each phase (Sullivan, 2020). Waveform variations (Figure 18.16) from the rather square shape of normal indicate likely pathophysiological changes, like pulmonary embolism, pneumothorax, or airway obstruction (Duckworth, 2017).
Pulse Oximetry
To understand pulse oximetry, it is important to recall the hemoglobin molecule and its relationship to O 2 . Hemoglobin is a molecule within red blood cells, and each of these molecules can carry four molecules of O 2 . A pulse oximeter is a noninvasive device (Figure 18.17) placed on the finger that is able to read this saturation of hemoglobin using light. It is portable in many settings, including available for home use, or attached for continuous monitoring in settings like emergency departments, ICUs, or operating rooms.
A normal saturation at sea level is 94 to 98 percent. At elevation, it may be acceptable for patients’ pulse oximetry to be lower, yet still be considered normal. Also, certain pathophysiological changes affect pulse oximetry or have effects on what percentage is desired for a particular patient. In patients with COPD or emphysema, a normal oxygen level is 88 to 90 percent, because lung disease causes a lower O 2 and higher PaCO 2 balance. A patient who has experienced blood loss after a surgery or traumatic injury or is anemic because of a disorder like iron deficiency may have a lack of O 2 being circulated because there is a lack of carriers.
A demonstration of teaching a patient how to use a peak expiratory flow rate (PEFR) for monitoring asthma is presented in this video.
Pulmonary Function Studies
To help diagnose respiratory dysfunction and determine whether a problem is restrictive or obstructive, pulmonary function tests (PFTs) may be performed (Figure 18.18 and Table 18.3). A restrictive disorder is when air has difficulty flowing out of the lungs, and an obstructive disorder is when the movement of airflow is restricted by the inability of lung tissue and/or chest wall to expand. The results of PFTs are dependent on the effort of the patient, and results should be considered with the patient’s history when reaching a diagnosis (Ponce et al., 2022).
| Type of Test | Lung Volumes | Tests | Results |
|---|---|---|---|
|
Spirometry
Device: Spirometer
|
|
FRC results can be used to estimate results of other volumes
FEV1 classifies the severity of obstructive lung diseases based on percent of predicted values. FEV1/FVC ratio helps distinguish obstructive from restrictive lung disease With FEV1/FVC ratio, TLC can be used to evaluate restrictive lung disease |
FEV1 greater than 70 percent predicted = MILD disease
60 to 69 percent = MODERATE disease 50 to 59 percent = MODERATE to SEVERE disease 35 to 49 percent = SEVERE disease Less than 35 percent = VERY SEVERE disease FEV1/FVC ratio greater than 0.70 with TLC less than 80 percent predicted value indicates restrictive lung disease |
|
Peak Expiratory Flow Rate
Device: Peak Flow Meter (PFM) Process: Exhale forcefully into PFM |
Peak expiratory flow rate (PEFR): The fastest rate that air can be exhaled |
PEFR assists patients to manage lung diseases (e.g., asthma, emphysema, chronic bronchitis)
Guides as to disease progress/current status |
Results use system of traffic light:
GREEN—Go: Continue current treatment(s) YELLOW—Caution: Call healthcare provider with results from PFM RED—Stop/Emergency: Use rescue inhaler Call HCP Go to ED |
Learn more about PFTs and associated terminology, reasons, and risks at this website.
Electrocardiogram
ECGs use a special type of paper, which looks rather like fine graph paper: the horizontal lines indicate the passage of time, with each small box representing 0.04 seconds and each larger box, which contains five small boxes, indicating 0.2 seconds. The vertical lines indicate electrical voltage. When an ECG tracing is viewed, there is a line established that indicates a straight passage of time: measurements of components of the cardiac cycle are made based on deflection and return from and to this line. This is referred to as the isoelectric line or baseline. Most commonly, nurses note whether the inflection rises from the isoelectric line or has a downward path, or a combination of both. The voltage is not necessarily routinely measured (Figure 18.19).
Nursing education programs provide introductions to cardiac rhythms—the depth of information depends on the type of program and other specific requirements. In settings like the ED, ICU, telemetry, and postanesthesia care unit (PACU), nurses are educated to recognize normal and abnormal traits of the cardiac cycle and, depending on facility policy, to provide a rhythm strip (six-second tracing of one or two leads from a continuous monitor), with measurements to indicate any noted abnormalities in conduction.
The electrical impulses in the heart produce electrical currents that flow through the body and can be measured on the skin using electrodes. This information can be observed as an electrocardiogram (ECG), a recording of the electrical impulses of the cardiac muscle (Figure 18.20). ECGs are extremely valuable for diagnosis and guiding treatment of patients with cardiac symptoms.
An ECG is often combined with cardiac biomarker testing when acute symptoms indicative of MI or other cardiac emergencies are present. ECG can also be performed to monitor conditions and treatments or used for routine screening for cardiomyopathy. An ECG machine conventionally has twelve leads, which are labeled with their respective placement on the body (Figure 18.21).
See the competency checklist for Performing a Twelve-Lead EKG. You can find the checklists on the Student resources tab of your book page on openstax.org.
Small graph paper (Figure 18.22) is used to record and measure an ECG. The vertical axis shows the electrical signal strength, and the horizontal axis shows the passage of time. Measurements are taken based on the boxes. Each large box is outlined in a darker shade and contains five smaller boxes, both horizontally and vertically. Horizontally, each small box shows the passage of 0.04 seconds, so each large box (four small boxes) indicates 0.2 seconds.
See the competency checklist for Applying a Holter Monitor. You can find the checklists on the Student resources tab of your book page on openstax.org.
On the ECG paper, the firing of the SA node and the electrical signal to the AV node, with atrial contraction, is known as the P wave. Next the AV node receives and holds the signal after the atria contract, while the ventricles fill, called the PR segment. The PR interval is the time from the beginning of the P wave to the start of the Q wave. The QRS complex is the flow of electricity from the AV node through the bundle of His and to the Purkinje fibers—this leads to ventricular contraction. Last is the T wave, when the ventricles repolarize. The QT interval measurement is taken from the beginning of the Q through the end of the T wave. Finally, the ST segment measurement is from the end of the S to the start of the T wave (Figure 18.23) (Christensen et al., 2023).