Cardiopulmonary Physiology Respiratory Cardiovascular Musculoskeletal Vestibular Neurological 2003 David L. Akin - All rights reserved http://spacecraft.ssl.umd.edu
The Human Circulatory System
Lung Measurements From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
Blood Pressure in Circulatory System
Gas Exchange in the Lungs From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
Gas Exchange in the Tissues From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
Metabolic Processes Respiratory Quotient ( RQ ) Function of activity and dietary balance Sugar: Protein: Fat: RQ = Exhaled volume of CO 2 Inhaled volume of O 2 C 6 H 12 O 6 + 6O 2 Æ 6CO 2 + 6H 2 O RQ =1.0 For well-balance diet RQ~0.85 ( ) ( ) ( ) 2C 3 H 7 O 2 N + 6O 2 Æ 5CO 2 + 5 H 2 O RQ = 0.83 C 57 H 104 O 6 + 80O 2 Æ 57CO 2 + 52 H 2 O RQ = 0.71
Respiratory Problems Hypoxia Hypoxic Hypemic Stagnant Histotoxic Hyperoxia Hypocapnia Hypercapnia
Types of Hypoxia Hypoxic (insufficient O 2 present) Decompression Pneumonia Hypemic (insufficient blood capacity) Hemorrhage Anemia Stagnant (insufficient blood transport) Excessive acceleration Heart failure Histotoxic (insufficient tissue absorption) Poisoning
Alveolar Pressures From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
Effects of Supplemental Oxygen From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
Hypoxia Effective Performance Time From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
Oxygen Toxicity From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
Gravity Effects on Arterial Pressure 320 mm 95/55 mmhg 120/80 mmhg 1200 mm 1000 mmh 2 O = 74.1 mmhg 210/170 mmhg
The Human Circulatory System, Revisited
Cardiovascular Effects of Microgravity Cardiovascular deconditioning Upper body blood pooling Changes in blood volume Increased calcium content
Acceleration Effects on Arterial Pressure 320 mm 25/ mmhg 120/80 mmhg 1200 mm At 4 g s longitudinal: 1000 mmh 2 O = 296 mmhg 475/435 mmhg
Decompression Sickness Release of dissolved gases in blood following pressure drop DCS, Caisson Disease, The Bends J. B. S. Haldane modeled DCS as supersaturation of dissolved nitrogen in blood: R = P N 2 = 0.79 (nominally) P ambient Experience indicates symptomatic DCS onset at levels of 1.6-1.8
Haldane Tissue Model Hypothesized that tissues absorb and release dissolved gases at exponential rates dp tissue dt = k( P alveoli - P ) tissue Response to a step change in alveolar pressure P tissue (t) = P tissue,0 + ( P alveoli - P )( tissue 1- e -kt )
Tissue Models, continued Rate coefficient frequently given as time to evolve half of dissolved gases: T 1/2 = ln(2) k Workman added concept of M-values - critical saturation limits for tissues Continued refinement of tissue models for predicting onset of DCS
PADUA (Univ of Pennsylvania) Tissue Model Tissue 1 2 3 4 5 6 7 8 9 10 T 1/2 (minutes) 5 10 20 40 80 120 160 240 320 480 M 0 (bar) 3.040 2.554 2.067 1.611 1.581 1.550 1.520 1.490 1.490 1.459
Tissue Saturation following Descent
Tissue Saturation after Ascent
Bubble Formation and Growth In equilibrium, external pressure balanced by internal gas pressure and surface tension Surface tension forces inversely proportional to radius UNIVERSITY OF
Vestibular System From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
Vestibular Sense Organs From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
Otolith Responses From Roy DeHart, Fundamentals of Aerospace Medicine, Lea & Febiger, 1985
Artificial Gravity 10000 1000 100 10 g rotation =w 2 r Lunar gravity Mars gravity 0.5*Earth gravity 0.75*Earth gravity Earth gravity 1 0 2 4 6 Rotation Rate (rpm)
Allowable Rotation Rates Select groups (highly trained, physically fit) can become acclimated to 7 rpm 95% of population can tolerate 3 rpm Sensitive groups (elderly, young, pregnant women) may have tolerance levels as low as 1 rpm
Short-Term Dose Radiation Effects 10-50 rem - minor blood changes 50-100 rem 5-10% minor nausea and vomiting 100-200 rem 25-50% nausea and vomiting 50% reduction in lymphocytes 200-350 rem Nausea, vomiting, diarrhea, minor hemorrhage 75% reduction in all blood cells 5-50% incidence of death
Short-Term Dose Radiation Effects 350-550 rem Nausea, vomiting, diarrhea, hemorrhage, emaciation 75% reduction in all blood cells 50-90% mortality within 6 weeks 6 month convalescence 550-750 rem Nausea and vomiting within four hours Mortality approaching 100% 750-2000 - survival time <2 weeks 2000+ - incapacitation within hours
NASA Radiation Dose Limits
References R. L. DeHart, ed., Fundamentals of Aerospace Medicine, Second Edition Williams and Wilkins, 1996 A. E. Nicogossian, C. L. Huntoon, and S. L. Pool, Space Physiology and Medicine, Third Edition Lea and Febiger, 1994 A. E. Nicogossian, S. R. Mohler, O. G. Gazenko, and A. I. Grigoriev, eds., Space Biology and Medicine (Volume III, Book 1: Humans in Spaceflight) American Institute of Aeronautics and Astronautics, 1996 J. T. Joiner, ed., NOAA Diving Manual: Diving for Science and Technology, Fourth Edition Best Publishing, 2001