Flashcards in RM Week 11 Deck (47)
List the two hormones in pregnancy that alter respiratory function?
Increased estrogen: causes fluid retention and edema throughout the airway mucosa and stimulates mucous gland hyperplasia, also increases blood volume (increases oxygen delivery)
Increased progesterone: sensitises Central chemoreceptors resulting in decreases pulmonary carbon dioxide and increased pH
What does relative hyperventilation of mother help with?
Aids clearance of fetal co2
Is there any significant change in PaO2 in the mother?
What can happen in pregnancy in regards to asthma?
Altered hormone levels may affect asthma control. (Can improve, worsen or stay the same). Airway hyperactivity can be increased but generally returns to pre-pregnancy levels with red months postpartum
What affects respiratory mechanics in mother in the last trimester? Also how is loss of lung function this partially offset?
Enlarging of the uterus. Diaphragm is displaced by the chephalad which decreases RV , decreases ERV, decreases IRV, decreases FRC.
Partially offset by increased anterior-posterior and transverse diameters of the chest and widening of subcostal angles
What's happens to VC and FEV1 in pregnancy?
Stay the same
When in weeks does an infant have a chance of surviving if premature?
26-27 weeks and over. This is during transition from canalicular to saccular
What secretes lung fluid?
Alveolar epithelial cells
What is the primary role of lung liquid?
To flush out debris out of lung and prevent developing tissues from collapsing. Appears to maintain a positive pressure relative to amniotic fluid, resulting in lung expansion responsible for stimulating cell division and lung growth
When do attempted respiratory movements begin to take place in the fetus?
By the end of first trimester . Increase in frequency from 22-35 weeks gestation
When are respiratory movements inhabited in the fetus and what is the point of this?
During last 7 days - helps to prevent lungs filling with fluid as well as debris from the meconium(first stool). Excreted into amniotic fluid
What type of Hb makes up 70% of all the Hb in a newborn?
Fetal Hb - HbF
Which has a higher oxygen affinity? Adult or fetal Hb?
Fetal Hb - designed to operative at a lover PO2
When is HbF replaced by adult Hb?
By 6 months of age
When do the majority of babies take their first breath?
Within the first 20s and have established a normal rhythm by 90 seconds
What allows air to be drawn into the lungs in birth?
Thoracic compression during vaginal delivery followed by elastic recoil of rib cage.
What are the major stimuli to breathing in newborns?
Largely unknown but cooling of skin and mechanical stimulation (via respiratory centre)
At birth where does fluid in lungs go?
Epithelial cells in lungs switch from secreting the lung fluid to absorption of fluid
How much pressure is required to oppose surface tension and open the alveoli for the first time?
25mmHg negative pressure
Why is it important that infant doesn't expel all their air in first expiration?
May cause alveoli to collapse and be retained like that by dynamic airway compression
How is surface tension created in the alveoli?
Attraction of water molecules in the alveolar fluid . h2O is more attracted to eachother than to air,
Where is surface tension directed towards in the alveoli?
The centre - acts to prevent alveoli being overstretched
What would happen if alveoli were lined by water alone?
Airway collapse as water attractive forces so strong
What's does surfactant do regarding surface tension?
Reduces surface tension by physically getting in the way of water molecules
What is surfactant made up of?
90% lipids, rest is proteins and carbohydrates
What is the most important lipid in surfactant and what is it responsible for?
DPPC- responsible for surfactants effect on surface area
Where is surfactant synthesized?
Type 11 alveolar cells
Half life of surfactant?
Other roles of surfactant ?
May have a role in lung defence (antiviral/bacterial), protein component may increase phagocytosis of bacteria and viruses . May assist with mucocillary escalator