Clinical Application of Gas Laws

25 y/o companion drove to 8000 ft then joked to 9,000ft and spent the night, the next day they continued to 11,000ft and on the third day camped at 12,400ft. That night the student developed a mild cough on the morning of the fourth day 60 hr after leaving sea level the group climbed and noted fatigue SOB, hyperventilation, and mental confusion by that afternoon they abandon the climb and defended then the was extremely fatigued and reported intense HA, cough increase and he began coughing up thin straw colored fluid. on the 12th hour of descent the party arrived at the car and the student felt better but was still exhausted.

-Acute Altitude sickness -Low Atmospheric pressure, low O2 -High altitude cerebral edema (confusion) -Pulmonary edema (hemopotis bloody cough) -PAO2 + PaO2 (decrease) -PACO2 + PaCO2 (decrease) -Systemic arterial pH (increase) -Hb concentration (no change) -Hb % Saturation (decrease) -The estimated PAO2 at the highest elevation climbed assume Patm is 500 mmHg, R=1 and PACO2 = 40 mmHg [ (500-47) * .21 ] - (40/1) = 55.13 mmHg -Hyperventilation would not prevent arterial PO2 from decreasing at high altitude

Acclimatization to High Altitude (3 or more days)

-PAO2 + PaO2 (still decreased so no change) -PACO2 + PaCO2 (goes from decreased to increased) -Systemic arterial pH (goes from increased back to normal) -Hb concentration (goes from no change to increased) -Hb % Saturation (still decreased so no change)

41 y/o secretary drove from Alaska to Florida which took 90 hours three days after arrive she started experiencing right sided chest pain cough and dyspnea she went the the ER and developed mild distress with RR 24 she has SOB and mild coughing she denies have been treated fro respiratory problems she takes oral contraceptive and warfarin but missed her dose since moving. She is an obese woman with a BMI of 40 extremities how signs of cyanosis and everything is found to the nml.

-Possible Pulmonary embolism that has travel to her lung affecting ventilation perfusion mismatch -Test arterial blood gases, like PAO2 which is 61 (95-100) and PACO2 is 32 (40) A-a gradient is 37 -CXR shows peripheral infiltrate in the right lower lobe CT reveal an embolus

22 y/o heathy man check out dives for scuba certification preforming an emergency swimming ascent to the surface from 30 m 4 atm immediately on surfacing he cries out in pain and then loses consciousness and is pulseless and dies. Patient was found to have a patent foramen ovale (PFO) between atria.

-Pressure volume density relationships -While ascending to the surface affected from decompression sickness (bubbles) -High barometric pressure causes compression of gases as the diver comes back to the surface surrounding pressure decreases.

Note that

Acutely altitude induced hyperventilation results in respiratory alkalosis resulting in an increase in arterial pH

Note that

Acutely at high altitude the main drive for ventilation changes from CO2 on the central chemoreceptors at sea level to a PO2 drive of the Peripheral chemoreceptors and hyperventilation ensues

Organ System that triggers Hyperventilation

Aortic Bodies => Carotid Bodies, Chemoreceptors

Note that

At high altitude low arterial O2 stimulates the peripheral chemoreceptors resulting in an increase in alveolar ventilation

High Altitude Cerebral edema symptoms

Ataxia, fatigue, altered mental statue, progressive decline in cognitive / mental function, dealing level of consciousness, impaired coordination, and slurred speech.

Lungs reaction to high altitude

Hypoxemia due to high-altitude ( decreased Patm and PAO2) => Initial non productive cough, SOB, Tachypnea -- Progress into productive cough, diffuse inspiratory crackles, exercise intolerance => increase capillary pressure, patchy lung infiltrates, extravascular lung water

Kidneys reaction to high altitude

Hypoxemia due to high-altitude ( decreased Patm and PAO2) => reduced O2 supply to the kidneys => increase EPO recreation RBC mass and Hct High hematocrit and an increase in EPO occurs with high altitude stemming ifrom kidney stress ins chronic prolonged time This is referred to high altitude induced adaptive polycythemia

Brains reaction to high altitudes

Hypoxemia due to high-altitude (decreased Patm and PAO2) => Hypoxia induced cerebral vasodilation, over perfusion of microvascular cerebral beds => increased Capillary leakage, disruption of BBB, and intracranial pressure

High Altitude Pulmonary edema

Occurs 2-4 days after climb and may accompany high altitude cerebral edema.