Physiology of Aviation and Diving

How does higher altitude cause hypoxia

Barometric pressure decreases → The PO2 and PCO2 in air decreases significantly

How is barometric pressure calculated

Water vapor + PCO2 + Po2 + Nitrogen

What happens when a person breathes pure O2 in high altitude

Nitrogen that previously occupied the alveoli is flushed out and replaced by O2

What is the acute effect of hypoxia

In unacclimatized person they will start to feel drowsy, lassitude mental and muscle fatigue and sometimes headache and nausea at an altitude of 12,000 ft

What acclimatization and its effects to low O2

When a person remains in high altitudes for many days to years → Get used to low PO2 and therefore are less affected by it

What are the means of acclimatization

Great increase in pulmonary ventilation, increased RBC, increased vascularity in peripheral tissue, increased ability for tissue to use O2

How does increased pulmonary ventilation help against low O2

Low O2 stimulate chemoreceptor → Increases alveolar ventilation + inhibits the brainstem ability to stimulate respiration

How is diffusing capacity increased

Increased pulmonary capillary blood volume, lung air volume and pulmonary arterial BP

What are HIF

DNA factors that respond to low O2 to encode proteins needed to deliver O2 to tissues → Active in hypoxia by inactivation of HIF hydrolase

What are the features of natural acclimatization

Increased chest size, small body size, high ratio of ventilatory capacity to body mass, larger hearts

What are the symptoms of Acute mountain sickness

Headache PLUS nausea, vomiting, dizziness, insomnia etc

What can be done to prevent acute high altitude illness

Ascend at a correct rate + adequate rest, acclimatize before exposure

What is a drug commonly used for altitude sickness

Acetazolamide

What is hyperbarism

Pressure is increased when under water → Lungs collapse if there is not enough air

What is the squeeze

Pressure will effect ears, sinuses and lungs causing ear squeeze and sinus squeeze

What can be done to equalize pressure

Swallowing, rotating jaw, Valsalva technique → DO NOT DIVE WITH COLD OR CONGESTION

What is nitrogen narcosis

Presents with joviality (drunkness) → At 150-200 diver becomes drowsy → 200-250 ft strength wanes → 250> ft diver becomes useless

What is the physiology of nitrogen narcosis

N2 is dissolved in fatty substances in neuronal membrane → Brain activity decrease

What is oxygen toxicity at high pressure

Breathing O2 at 4 ATM of O2 will cause seizure + coma within 30-60 minutes → Exercise before diving will increase risk of O2 toxicity

What is CO2 toxicity

WILL NOT happen if diving gear functions correctly → Caused by rebreathing CO2 that was just exhaled → Respiratory acidosis

What is decompression sickness

Breathing air under high pressure increased N2 dissolution in body tissue → If ascend to fast (pressure change is happening to fast) N2 will form bubbles

What are the symptoms of DCS

Pain in joint and muscle of leg/arm (85-90%), NS symptoms in 10% of patients, pulmonary edema in 2%