Pregnancy Physiology: Cardiovascular, Hematologic & Respiratory System– Obstetrics | Lecturio


So now let’s talk about
the physiology of pregnancy. So here’s a case. Jennie is a 25 year old gravida
1 para 0 female at 34 weeks of gestation. She reports increased difficulty
in taking deep breath. She denies shortness of breath
on exertion and no chest pain. Her pregnancy has been
uncomplicated and she has no medical problems. What is the most likely cause
of her difficulty in breathing? And we’ll think as we go
throughout the lecture. So when we think about the
changes of physiology that happen in pregnancy, there are
8 systems that we will want to focus on. First cardiovascular. Next hematologic. Next respiratory. Then the gastrointestinal system. Then the renal system,
metabolic, endocrine and anatomical changes that we
see throughout the pregnancy. So let’s start with
the cardiovascular system. First there are some anatomical
changes that we need talk about. The heart is displaced left
and upward and is rotated on it’s long axis in pregnancy. This is important, because when
you listen for heart sounds, it’s a little different than
in a non-pregnant patient. So now let’s talk about
the physiological changes within the cardiovascular system. So we know that the systemic
vascular resistance changes. So how do you think it changes. Does it increase? Does it decrease? Well, in fact it decreases. And this is the reason in
the 1st and the 2nd trimester, we notice that the blood
pressure also decreases. 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. Our heart rate also
changes in pregnancy. What do you think,
does it increase? or does it decrease? The heart rate also
increases in pregnancy. And lastly, cardiac output. Do you think it increases
or decreases? You probably guessed right. It increases. In fact it increases to
almost to 15 to 40% in the 1st trimester and even more
during the labor process. So now let’s move to
the hematologic system. That also changes in pregnancy. First we notice that the blood
volume increases to 40 to 45% about the non-pregnant patient. This is mostly because of
increase in the erythrocytes and in plasma. And we notice that pregnant
woman have physiologic anemia because of this increase. So what else changes. Well our iron requirements
also increase in pregnancy. Some of that can be met
in the diet but in some pregnant women, they require ion supplementation
to meet that increase demand. Now our immune system
also changes in pregnancy. We’re not exactly
sure why that happens. But we do know that the immune
system is blunted in pregnancy. Making pregnancy
immunodeficient state. Now lastly but most importantly
in the hematological system. Pregnant women
are hypercoagable. That means their blood is
thickened and because of that they are at increased risk
for dethrombosis as well as pulmonary embolism. This is important to think about
as this can be a huge cause of maternal mortality. Specially in life of patients
that undergo C-section. Surgery we know increases
our risk of DBT and pregnancy because it is a
hypercoagable state. It also increases that risk. So we need to be sure
to watch out for that. So now moving on to
the respiratory system. There are some anatomic as well
as physiologic changes in that system as well. First is the change
in the diaphragm. We notice that rises
by 4 centimeters. Can you think of why that maybe? Well, let me tell you. The uterus is increasing
during that time. As the uterus gets larger,
the diaphragm get’s pushed up as well. So how does that affect our
physiologic changes within the respiratory system. Well the functional
residual capacity decreases. And again that’s just because
the diaphragm is pushing up, so that residual capacity decreases. The total lung volume
however does not change. Our expiratory residual volume
and our residual volume also decrease. And then when we think
of our tidal volume and our minute ventilation,
they both increase. So this is a nice diagram
that puts all those things that I’ve just told you,
into one big location. So I would make sure
that you go through this in a lot of detail to make
sure you understand those changes in the lung volume
as we’ve previously discussed. So let’s move on to a question. During pregnancy which of the
following physiological changes within the pulmonary system? A. Because of compression
from the uterus, the total lung capacity (TLC) decreases. B. Because of compression
from the uterus, the inspiratory capacity (IC)
decreases. C. Because of compression from
the uterus, the residual volume (RV) decreases. Or D. None of the above. What do you think? Well, the answer is C. Because of the compression from
the uterus, and remember that also causes the diaphragm
to decrease by 4 centimeters. The residual volume
also decreases. Total lung capacity,
inspiratory capacity, those volumes do not change
because of pregnancy.

11 Replies to “Pregnancy Physiology: Cardiovascular, Hematologic & Respiratory System– Obstetrics | Lecturio”

  1. Good lecture I'm a big fan of lecturio ☺☺☺☺☺☺☺☺☺☺☺☺☺☺☺☺☺😊😊😊😊😊😊😊😊👏

  2. Simply excellent. Very grateful for clear, concise and well presented video. Thank you for the great channel. 😊😊 10/8/2019

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