Respiration under stress
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Transcript of Respiration under stress
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Lectures on respiratory physiologyLectures on respiratory physiology
Respiration under stressRespiration under stress
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Respiration under stress
• Exercise
• High altitude
• Diving
• Space flight
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Exercise
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Respiratory responses to exercise
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Comparison of the increases in blood flow
and ventilation
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Additional changes with exercise
Pulmonary artery, venous and capillary pressures rise
Recruitment and distension of capillaries
Pulmonary vascular resistance falls
Pulmonary diffusing capacity increases
Shifts of the O2 dissociation curve
Capillaries open up in exercising muscle
Systemic vascular resistance falls
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High altitude
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Decrease of barometric pressure with altitude
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Climber on the Everest Summit
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Polycythemia at 4600 m altitude
• Hemoglobin concentration 19.8 g/dl
• Arterial PO2 45 mm Hg
• O2 saturation 81%
• O2 concentration 22.4 ml/dl
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PO2 cascade at sea level and high altitude
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Other features of acclimatization
• Shifts of the O2 dissociation curve
• Increased concentration of capillaries in muscle
• Changes in oxidative enzymes in cells
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Uneven hypoxic pulmonary vasconstriction exposes some capillaries to high pressure
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Diving
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Physiological Stresses with Diving
Mechanism of decompression sickness
Treatment and prevention of decompression sickness
Use of helium-oxygen for breathing
Saturation diving
Inert gas narcosis
CNS toxicity caused by high-pressure oxygen
Pulmonary oxygen toxicity
Hyperbaric oxygen therapy
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Concentration of dissolved O2 in the blood with hyperbaric therapy
• Barometric pressure = 3 x 760 mm Hg• Alveolar and arterial PO2 exceed 2000 • Solubility of O2 is 0.003 ml/dl/mm Hg• Dissolved O2 = 6 ml/dl• This exceeds the normal arterial-venous
difference for O2
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Space flight
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Effects of gravity on the lung
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Shuttle Launch
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Spacelab in the Bay of the Shuttle
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Spacelab under 1 G Conditions
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Spacelab during Microgravity
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Study of Pulmonary Function in Microgravity
• Package of 9 tests• Duration 31 minutes in microgravity• Crew member performs test on
himself• Data available on ground in real time• Comprehensive assessment of
pulmonary function
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Astronaut with the lung function experiment
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Pulmonary function in microgravity I
• Increased pulmonary capillary blood volume
• Increased pulmonary diffusing capacity• Increased cardiac output and stroke
volume• More uniform distribution of blood flow
and ventilation• FRC between upright and supine at 1G• Residual volume reduced• Changes in the deposition of aerosol
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Pulmonary function in microgravity II
• O2 uptake and CO2 output unchanged• Alveolar PO2 and PCO2 unchanged• No significant impairment of lung
function during two weeks of microgravity
• On return from six months on the International Space Station, lung function soon returned to pre-flight conditions