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PREDICTIVE STUDIES VI (PS VI): Extension of O2 Tolerance by Intermittent Exposure
Major Category: Extension of pulmonary and neurologic O2 tolerance (PS VI)

Background: The Predictive Studies VI Program was designed to investigate Pulmonary and Neurologic hyperoxic oxygen tolerance, by imposing programmed interruptions of oxygen exposure. The Predictive Studies V investigations of continuous oxygen exposure at 2.0 ATA served as the baseline for comparison with patterns of intermittent O2 exposures.

PS VI Program data expands prior Stress Data Center information relating to Pulmonary oxygen tolerance extension at 2.0 ATA (Report: Hendricks, P. L., D. A. Hall, W. L. Hunter, Jr., and P. J. Haley. Extension of pulmonary O2 tolerance in man at 2 ATA by intermittent O2 exposure. J. Appl. Physiol. 42: 593-599, 1977). It adds information concerning extension of visual system (CNS) oxygen tolerance at 2.0 ATA.

Expt. Title: Human tolerance to intermittent O2 exposure at 2.0 ATA. Predictive Studies VI. (Expt. 9.71b)

Date: 1989-1991

Description:

Multiple physiological functions were monitored before, during, and after intermittent O2 exposures at 2.0 ATA with Subjects at rest. Two intermittent protocols were tested.

Protocol 1: 60 min breathing O2 alternating with 15 min breathing a normoxic gas mix.

In 1989-90, 8 Subjects were studied at 2.0 ATA on an intermittent schedule that alternated 60-minute O2 periods with 15-minute normoxic intervals. Six Subjects had a mean exposure duration of 13.6 O2 hours (range 11.4-15.0 hours). The exposure of one subject was stopped at 7.0 O2 hours due to a claustrophobic reaction to breathing through a facemask in an enclosed space. Another subject stopped at 9.0 O2 hours due to severe nausea.

Protocol 2: 30 min breathing O2 alternating with 30 min breathing a normoxic gas mix.

In 1990-91, 6 Subjects were studied at 2.0 ATA on an intermittent schedule that alternated 30-minute O2 periods with 30-minute normoxic intervals. Four of these Subjects continued as planned for 15.0 O2 hours. Two other Subjects stopped at 13.0 O2 hours.

Experiment protocols and measurement modules:

Results: For each intermittent exposure pattern at 2.0 ATA are summarized in the Final Report for "Extension of O2 Tolerance in Man. Predictive Studies VI". Original records preserved in Data Center.

Subcategory

 Measurements

1: Brain cortical electrical activity

 Electroencephalography (available on tape and hard copy).

2: Visual function

 Visual fields, electroretinogram, visual evoked cortical response, visual acuity, accommodation, pupillometry.

3: Auditory and vestibular function 

 Auditory brainstem responses, puretone air and bone conduction audiometry with routine and ultra-high frequencies, tympanometry, acoustic reflex thresholds, reflex decay testing, electronystagmography.

4: Mental and psychomotor function

 Visual digit span test of short term memory, key insertion test of finger dexterity, operations test of number facility and general reasoning ability, visual reaction time test of response speed.

5: Respiratory function

 Expiratory minute volume, frequency, tidal volume, end-tidal PCO2, rate of CO2 elimination at rest, peak inspiratory pressures at functional residual capacity and residual volume, peak expiratory pressures at functional residual capacity and total lung capacity.

6: Respiratory control

 Ventilatory response to hypercapnia, ventilatory response to hypoxia, inspiratory duration, expiratory duration.

7: Body temperature

 Rectal temperature

8: Skeletal muscle strength

 Maximal handgrip, grip duration at 80% maximum.

9: Pulmonary function

 Lung volumes and flow rates (forced expiratory vital capacity, one-second forced expired volume, maximal mid-expiratory flow rate, peak expiratory flow rate, slow vital capacity, inspiratory capacity, expiratory reserve volume), density dependence of flow rates (flow difference at 50% vital capacity, lung volume at equal flow rates), carbon monoxide diffusing capacity, arterial blood gases (PO2, PCO2, pH, HCO3), alveolar-arterial PO2 differences at rest and during exercise, lung compliance, airway resistance.

10: Cardiocirculatory function

 Electrocardiography (heart rate, rhythm), arterial blood pressure (systolic, diastolic, mean), impedance cardiography (stroke volume, cardiac output).

REPORT: Lambertsen, C. J., and J. M. Clark. Biochemical, Endocrine, and Hematological Factors in Human O2 Tolerance Extension (PS VI). IFEM-EBSDC Tech. Report # 3-31-92. Philadelphia, PA: Institute for Environmental Medicine, University of Pennsylvania, 1992.

REPORT: Clark, J.M., R. Gelfand, W.C. Stevens, and C.J. Lambertsen. Comparison of human visual and pulmonary responses to continuous and intermittent O2 exposure at 2.0 ATA in Predictive Studies V and VI (ABSTRACT). Undersea Biomed. Res. 18 (Supp.): 86, 1991.

REPORT: Stevens, W.C., R. Gelfand, J.M. Clark, and C.J. Lambertsen. Core temperature in man during intermittent hyperoxia in Predictive Studies VI (ABSTRACT). Undersea Biomed. Res. 19 (Supp.): 31, 1992.

REPORT: Clark, J.M., R. Gelfand, W.C. Stevens, and C.J. Lambertsen. Unexpected pattern of pulmonary and visual O2 tolerance extension in man during intermittent hyperoxia at 2.0 ATA in Predictive Studies VI (ABSTRACT). Undersea Biomed. Res. 19 (Supp.): 90-91, 1992.

REPORT: Gelfand, R., J.M. Clark, W.C. Stevens, and C.J. Lambertsen. Partial reversal of respiratory control timing effect of O2 toxicity in man during intermittent hyperoxia at 2.0 ATA in Predictive Studies VI (ABSTRACT). Undersea Biomed. Res. 19 (Supp.): 91, 1992.

Extension of O2 tolerance in animals (PS VI)


02 February 2000 10:05:23 AM

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