Lectures on respiratory physiologyLectures on respiratory physiology

Respiration under stressRespiration under stress

Respiration under stress

• Exercise

• High altitude

• Diving

• Space flight

Exercise

Respiratory responses to exercise

Comparison of the increases in blood flow

and ventilation

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

High altitude

Decrease of barometric pressure with altitude

Climber on the Everest Summit

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

PO2 cascade at sea level and high altitude

Other features of acclimatization

• Shifts of the O2 dissociation curve

• Increased concentration of capillaries in muscle

• Changes in oxidative enzymes in cells

Uneven hypoxic pulmonary vasconstriction exposes some capillaries to high pressure

Diving

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

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

Space flight

Effects of gravity on the lung

Shuttle Launch

Spacelab in the Bay of the Shuttle

Spacelab under 1 G Conditions

Spacelab during Microgravity

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

Astronaut with the lung function experiment

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

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