Lectures on respiratory physiology

1
Respiration under stress

• Lectures on respiratory physiology

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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

13
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
16
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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(No Transcript)
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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