1. Orthostatic intolerance by lower body negative pressure (LBNP) including heart rate, systolic and diastolic blood pressure, percentage change in calf volume, systolic time intervals, and vectorcardiograms (VCGs)
2. Heart size by posterior-anterior chest x-rays (L-15 only)
3. Resting (supine) leg volume
The postflight protocol consisted of:
1. LBNP test performed on recovery day (R+0) on one subject.
2. Chest x-rays
3. Leg volume measurements.
The test protocol for LBNP consisted of following six evaluation periods:
1. Supine resting in the LBNP for five minutes
2. Up to 25 mm Hg negative pressure for two minutes
3. 30 to 35 mm Hg negative pressure for three minutes
4. 40 mm Hg negative pressure for five minutes
5. 50 mm Hg negative pressure for five minutes
6. Recovery supine in LBNP device for five minutes
LBNP level, heart rate, ECG or VCG, and systolic and diastolic blood pressure were monitored continuously. Age, body weight, body temperature, duration of sleep, time since sleep, time since last meal, amount of fluid intake, time of day, ambient temperature, and environmental test conditions were also noted.
During LBNP, time of day, ambient and LBNP temperature, time since last meal, and amount of sleep were all nominal and within desired limits of experimental control. No results were considered beyond acceptable limits. Preflight, one subject experienced one episode of presyncope during the later portion of the 40 mm Hg protocol at L-15. Postflight, only one subject was evaluated by LBNP, this occurring approximately 2 hours 20 minutes after recovery. Two minutes into the 50 mm Hg level of LBNP, the protocol was terminated due to progressively declining blood pressure. The crewmen vehemently denied any associated symptomology. This postflight measurement was made prior to the decision to cease all nondiagnostic and nonclinical testing. This decision was made in response to the medical complications arising from the crew exposure to the toxic gases during reentry.
Because LBNP recordings scheduled immediately after flight were deleted, no useful information was obtained from systolic time intervals, echocardiograms, or VCGs. Strictly resting VCGs were taken on recovery day in conjunction with clinical ECGs. All tracings were considered to within normal limits. One crewmember experienced occasional premature supraventricular beats similar to those observed before flight.
Chest x-rays provided heart size determinations by cardiothoracic (C/T) ratios. No notable or consistent findings developed, but this data must be considered in the light of significant postflight pulmonary involvement.
Apart from the noxious gas event with the recovery of the ASTP crewmen and their ensuing pulmonary consequences, no findings would lead to conclusions different from that reached with all previous US manned space missions: a modest postflight orthostatic intolerance without operational significance was demonstrated.
|Mission||Launch/Start Date||Landing/End Date||Duration|
|ASTP||07/15/1975||07/24/1975||9 days, 7.5 hours|