Keyword
HPV (Hypoxic pulmonary vasoconstriction)
Definition
Hypoxic lung regions에 blood flow를 줄이는 lung의 보상작용
Mixed venous PO2보다 Hypoventilation 이나 낮은 PO2의 gas breathing으로 인한 low alveolar oxygen tension에 영향을 더 받음
Constriction의 세기는 Hypoxia에 노출된 lung segment의 size에 관계되어 size가 작을수록 세기가 세짐
Factors inhibit HPV (Increasing venous admixture)
- Very high or low pulmonary artery pressure
- Hypocapnia
- High or very low mixed venous PO2
- Vasodilators (Nitroglycerin, nitroprusside, milrinone, b-agonist, CCB)
- Pul. infection
- Inhalation anesthetics (including N2O)
Factors decrease blood flow to the ventilated lung
-> Increasing blood flow to the collapsed lung 으로 HPV 효과를 무효화
- PEEP
- Hyperventilation
- High peak inspiratory pressure
- A low FiO2 (HPV유발)
- Vasoconstrictors (normoxic vessels에 hypoxic한 곳보다 영향 큼)
- Intrinsic PEEP (Expiratory time 연장으로 인한)
Further readings
Morgan and Mikhail's Clinical Anesthesiology, 5th edition, P.549
Reference
Morgan and Mikhail's Clinical Anesthesiology, 5th edition, P.549