repiratory physio 6

Question 1

how do alveoli respond to low oxygen and how is this different from the systemic system? what is the alveolar response called?

Answer 1

• different in the sense that when there is low oxygen in the alveoli, there is vasoconstriction rather than dilation so that you can get blood redistribution to better aerated alveoli
• called hypoxic pulmonary vasoconstriction (HPV)

Question 2

what are some conditions that would bring about hypoxic pulmonary vasoconstriction?

Answer 2

• obstructed airway
• failure to ventilate
• acute lung damage
• high altitude- because low oxygen at sea level
• disease states that cause decreased ventilation (COPD)

Question 3

what does hypoxic vasoconstriction and associated vascular structural remodeling eventually cause

Answer 3

Pulmonary arterial htn

Question 4

when is 2,3 DPG high?

Answer 4

-it is used and is in high amounts when the patient is anemic, chronic hypoxia, acclimation to high altitude

Question 5

what’s important to note regarding the lung base versus it’s apex? how is this important clinically

Answer 5

• lung base carries more blood due to gravity
• it is better to look at when detecting problems with pressure as the alveolar pressure is higher than in the apex
• an increase in hydrostatic pressure can be detected when the blood leaks out into the capillaries and out into the interstitium where we can see opacity right at the base of the lung

Question 6

what is the structure of the pulmonary capillaries

Answer 6

• pulmonary capillaries surround the alveoli but are very leaky to protein molecules and are thin walled with low pressure

Question 7

what are the forces acting on capillaries, interstitium and alveoli?

Answer 7

• capillaries have a hydrostatic pressure pushing fluid out into the interstitium
• capillaries also have oncotic pressure pulling fluid back in to the capillaries and out of the interstitium
• the interstitium always has a negative net force unless there is edema or inflammation
• the alveoli has surface tension at its pores that brings fluid out of the interstitium and into alveoli while aslo having evaporation that does the same. it also has an even LARGER hydrostatic pressure pushing fluid into the interstitium
• > the interstitium then drains this net force of fluid into the lymphatics

Question 8

what is the average normal value of ventilation to perfusion ratio

Answer 8

0.8

Question 9

what are some v/q (ventilation/perfusion) defects

Answer 9

1) ventilation but no blood flow = dead space
2) hi ventilation but little blood flow
3) low ventilation but high perfusion
4) no ventilation- no ventilation but have blood flow

Question 10

what is dead space and what does it’s alveolar gas composition resemble? what is a clinical example of this?

Answer 10

• dead space is regions in the alveoli that are ventilated but not perfused
• because there isn’t any gas exchange, the composition at the alveoli resembles what you are breathing in
• pulmonary embolism -blockage in the capillary going to the alveolus