Pregnancy Physiology: Cardiovascular, Hematologic and Respiratory System

00:01 So now let's talk about the physiology of pregnancy.

00:05 So here's a case.

00:06 Jennie is a 25 year old gravida 1 para 0 female at 34 weeks of gestation.

00:13 She reports increased difficulty in taking deep breath.

00:16 She did not shortness of breath on exertion and no chest pain.

00:20 Her pregnancy has been uncomplicated and she has no medical problems.

00:24 What is the most likely cause of her difficulty in breathing? And we'll think about this as we go throughout the lecture.

00:30 So when we think about the changes, physiology that happen in pregnancy, there are eight systems that we want to focus on.

00:37 First cardiovascular.

00:39 Next hematologic.

00:41 Next respiratory.

00:43 Then the.

00:43 The gastrointestinal system.

00:46 Then the renal system.

00:47 Metabolic, endocrine and anatomic changes that we see throughout the pregnancy.

00:53 So let's start with the cardiovascular system.

00:55 First, there are some anatomical changes that we need to talk about.

00:58 The heart is displays left and upward and is rotated on its long axis in pregnancy.

01:04 This is important because where you listen for heart sounds is a little different than in the non-pregnant patient.

01:10 So now let's think about the physiologic changes within the cardiovascular system.

01:14 So we know that the systemic vascular resistance changes.

01:17 So how do you think it changes? Does it increase? Does it decrease? Well, in fact, it decreases.

01:24 And this is the reason in the first and the second trimester, we notice that the blood pressure also decreases.

01:30 Well, when we think about the main arterial pressure, what do you think happens there? Does it increase? Does it decrease? It in fact, decreases as well.

01:39 Our heart rate also changes in pregnancy.

01:42 What do you think? Does it increase or does it decrease? The heart rate also increases in pregnancy.

01:48 And lastly, cardiac output.

01:51 Do you think it increases or decreases? You probably guessed right. It increases.

01:56 In fact, it increases to almost 15 to 40% in the first trimester and even more during the labor process.

02:05 So now let's moved to the hematologic system that also changes in pregnancy.

02:10 First, we noticed that the blood volume increases to 40 to 45% above the non-pregnant patient.

02:16 This is mostly because of increase in erythrocytes and in plasma.

02:20 And we noticed that pregnant women have a physiologic anemia because of this increase.

02:25 So what else changes? Well, our iron requirements also increase in pregnancy.

02:29 Some of that can be met in the diet, but in some pregnant women, they require iron supplementation to meet that increase demand.

02:37 Now our immune system also changes in pregnancy.

02:41 We're not exactly sure why that happens, but we do know that the immune system is blunted in pregnancy, making pregnancy an immunodeficiency state.

02:50 Now lastly, but most importantly in the hematologic system.

02:53 Pregnant women are hypercoagulable.

02:56 That means their blood is thickened.

02:57 And because of that, there are increased risk for deep vein thrombosis as well as pulmonary embolism.

03:03 This is important to think about as this can be a huge cause of maternal mortality, especially in light of patients that undergo C-section.

03:11 Surgery, we know, increases our risk of DVT and pregnancy because it is a hyper collateral state, also increases that risk.

03:18 So we need to be sure to watch out for that.

03:22 So now moving on to the respiratory system, there are some anatomic as well as physiologic changes in that system as well.

03:29 First is the change in the diaphragm.

03:31 We notice that that rises by four centimeters.

03:34 Can you think of why that may be? Well, let me tell you, the uterus is increasing during that time.

03:40 As the uterus gets larger, the diaphragm gets pushed up as well.

03:44 So how does that affect our physiologic changes within the respiratory system? Well, the functional residual capacity decreases.

03:52 And again, that's just because the diaphragm is pushing up.

03:55 So that residual capacity decreases.

03:57 The total lung volume, however, does not change our expiratory residual volume and our residual volume also decrease.

04:06 And then when we think about our tidal volume and our ventilate ventilation, they both increase.

04:12 So this is a nice diagram that puts all those things that I just told you into one big location.

04:18 So I would make sure that you go through this in a lot of detail to make sure you understand those changes in the long volume, as we previously discussed.

04:26 So let's move on to a question.

04:28 During pregnancy, which of the following physiologic changes happen within the pulmonary system? A Because of compression from the uterus, the total lung capacity decreases.

04:39 B Because of compression from the uterus, there is rotary capacity decreases.

04:44 C Because of compression from the uterus, the residual volume decreases.

04:48 R. D None of the above. What do you think? Well, the answer is C because of the compression from the uterus.

04:57 And remember, that also causes the diaphragm to decrease by four centimeters.

05:02 The residual volume also decreases.