Tag: pulmonary edema

Normal physiological changes of the mother during pregnancy have the potential to exacerbate preexisting cardiorespiratory conditions or lead to new disorders. By Bill Pruitt, MBA, RRT, CPFT, AE-C, FAARC During pregnancy, many changes occur in the mother’s body to accommodate and support the developing fetus, from providing warmth, nutrients, and oxygen to removing waste products from the baby as metabolism occurs. These changes in the mother’s body have the potential to exacerbate preexisting medical conditions, or bring about new challenges to the mother’s health and well-being. SUBSCRIBE TO DAILY RT NEWS Mothers suffering from asthma, cystic fibrosis, systemic and/or pulmonary hypertension, valve diseases, arrhythmias, or other cardiac pathology may find their conditions worsen. In addition, new conditions may manifest during pregnancy, such as preeclampsia, gestational asthma, acute pulmonary edema, cardiomyopathy, or others. This article will focus on several of these maternal issues and discuss the pathology and the management needed to support the mother. Normal Cardiovascular Changes in Maternal Physiology As a fetus begins to develop, the mother’s body has to change to accommodate the demands required to support the process. Beginning at about 6 weeks, her blood volume begins to increase; by approximately 32 weeks gestation, it reaches a peak of about 4.7 to 5.2 liters total (about a 45% increase, or 1.2 to 1.6 liters of extra volume).[1] During this time, the distribution of blood shifts as well. By the third trimester, there is an increase in interstitial and plasma volume. This hypervolemia has many possible causes, including increased sodium and the effects of estrogen on the renin-angiotensin system, a hormone system that regulates sodium balance, fluid volume, and blood pressure. Fetal growth and the baby’s weight at birth correlate directly with the increase in plasma volume. Meanwhile, a reduction in plasma volume is linked to clinical issues such as intrauterine growth restriction (IUGR) and small for gestational age (SGA) in the newborn, and preeclampsia in the mother. Other cardiovascular changes include an increase in red blood cell production, with a 17% to 40% increase in red blood cell mass (between 250 mL and 450 mL). This ramp-up in red blood cell production requires about a 500 mg increase in iron. Despite the increase in red blood cell mass, the larger plasma volume results in a relative decrease in hemoglobin concentration (referred to as physiologic anemia of pregnancy).[1] Cardiac Output and Blood Pressure Cardiac output increases during pregnancy and may hit a peak of 150% of normal. The time frame for this is near to that of the blood volume changes mentioned prior; cardiac output begins to increase during the first trimester and hits the maximum between 25 and 35 weeks gestation. Increased stroke volume provides the initial increase in cardiac output, but the mechanism shifts to an increase in heart rate as stroke volume increases up to the end of the second trimester, then plateaus. Heart rate increases by about 20 beats per minute by the time the pregnancy reaches week 32. Changes in maternal position will alter the cardiac output due to compression or release of the inferior vena cava (IVC). Positioning on the side allows for normal venous return, whereas a supine position will compress the IVC and have a marked effect on cardiac output levels. While measuring cardiac output using an invasive pulmonary artery catheter and the Fick method, the dye dilution method, or the thermodilution technique using a cold injectate has been recognized as the gold standard, M-mode Doppler echocardiography has gained recognition as having good correlation with the PA catheter methods, while avoiding the issues linked to invasive monitoring.[1] Meanwhile, blood pressure begins to decrease with the advancing pregnancy until about 20 to 24 weeks, then begins to rise to normal or above normal levels once term is reached. Systemic vascular resistance (SVR) also undergoes a significant decrease, with an approximate 10% reduction during the first trimester and reaching about 35% below normal at the midpoint of the gestation, where it remains fairly level. (It is thought that nitric oxide plays a part in the decrease in SVR.)[1] Normal Pulmonary Changes in Maternal Physiology Oxygen consumption reflects the uptick in maternal metabolism by increasing between 20% and 30% by the time full term is reached. Early in the pregnancy, oxygen consumption is covered by the increase in cardiac output so the blood supply to the fetus is rich in oxygen. However, as the pregnancy progresses, O2 consumption continues to increase and overtakes the increase in cardiac output, resulting in a widening arterial-venous oxygen difference. The final a-v O2 difference at term returns to normal prepregnancy levels.[1] Pulmonary function is altered, with an increase in tidal volume of 30% to 40%, resulting in an increase in minute ventilation of approximately 40%. As a result of a drop in both the expiratory reserve volume and the residual volume, the functional residual capacity (FRC) is reduced by about 20%. These changes are brought on by the growth of the fetus in the abdomen, which causes the diaphragm to elevate approximately 4 cm.[2] Total lung capacity is reduced by about 5%. The relative state of hyperventilation results in a respiratory alkalosis when arterial blood gases are checked. FEV1 and peak expiratory flow (PEF) are normally unchanged during normal pregnancy.[2,3] Despite the decrease in FRC, total lung capacity (TLC) will decrease only slightly due to a widening of the thoracic cage. Lung compliance remains stable during the pregnancy, but there is a decrease in chest wall and total respiratory compliance.[4] Cardiopulmonary Complications During Pregnancy: Asthma Asthma is a common problem in the general population and may be an issue during pregnancy. This disease is estimated to affect between 3% and 8% of pregnancies.[5] Asthma is said to follow the “Rule of Thirds” for pregnant women: about 28% of pregnancies with existing asthma show an improvement, about 33% of pregnant asthmatics have no change in their asthma, and about 35% get worse.[2,3] During pregnancy, an asthmatic has an increased risk of preeclampsia, excessive vomiting, gestational diabetes, low birth weight, and premature delivery.[2] Issues during pregnancy that may aggravate asthma include gastroesophageal reflux disease (GERD), changes in the chest wall conformation, and increases in upper respiratory infections.[3] The National Heart, Lung, and Blood Institute began the National Asthma Education and Prevention Program (NAEPP) several years ago, which has released guidelines for the diagnosis and management of asthma in the form of the Expert Panel Report (EPR). The third report was released in 2007 and refers the reader to the 2004 NAEPP working group’s publication, “Working Group Report on Managing Asthma During Pregnancy: Recommendations for Pharmacologic Treatment—Update 2004.”[6] This report states that it is better to treat the pregnant asthmatic than to have her suffer with asthma symptoms and exacerbations.[6] Asthma during pregnancy calls for the same assessment, monitoring, and education as during nonpregnant conditions. The goal is to provide the optimal care for keeping asthma under control using the right medications in order to have the best quality of life for the mother and the optimal conditions for the fetus/neonate. As described in the EPR-3 guidelines and in the Working Group Report 2004, albuterol is the preferred drug for controlling intermittent asthma, with the addition of an inhaled corticosteroid for persistent conditions (including mild, moderate, and severe persistent asthma). Budesonide (also known as Pulmicort by AstraZeneca) is the preferred inhaled corticosteroid due to the amount of data regarding the drug’s safety and efficacy during pregnancy.[2,6] Hypoxemia (and hypotension) should be treated early and effectively to avoid complications with the fetus, which may be compromised prior these two problems becoming an issue to the mother.[2,5] Close fetal surveillance is needed whenever the mother has any loss of asthma control, particularly in an acute asthma attack, as the fetus will suffer from oxygen desaturation with the slightest drop in maternal PaO2.[2] Pregnant women are encouraged to follow a comprehensive approach to asthma control: avoidance of triggers, smoking cessation, immunotherapy, commitment to self-monitoring, following an asthma action plan, proper self-administration of medications, and early intervention if symptoms do not improve with self-management. These issues are no different than for those not pregnant.[3] Cystic Fibrosis The life expectancy has been increasing for patients with cystic fibrosis (CF), to the point where, for those born in the 1990s, the predicted median age of survival has moved well into adulthood (over 40 years of age).[13] With this increase in life expectancy, pregnancy is becoming more frequent. While almost all males with CF are infertile due to closure or absence of the vas deferens, females with CF often have normal reproductive organs and normal menses, and are able to become pregnant. Recommendations call for bimonthly visits to a CF center during pregnancy and assessment, monitoring (including lung function tests), education, and adjustment of medications carried out with care. When comparing CF patients to non-CF patients 1 year after pregnancy, the CF National Patient Registry database showed no difference in the rate of hospital admissions, use of home IV antibiotics, use of supplemental oxygen, or use of supplemental nutrition. Premature delivery is the most common complication of pregnancy in the CF patient population—occurring in some 24% of those with severe CF. Otherwise, those with CF are comparable to those without CF when looking for...

Tag: pulmonary edema

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