A Network Analysis of Digital Clock Drawing for Command and Copy Conditions

Graphomotor and time-based variables from the digital Clock Drawing Test (dCDT) characterize cognitive functions. However, no prior publications have quantified the strength of the associations between digital clock variables as they are produced. We hypothesized that analysis of the production of clock features and their interrelationships, as suggested, will differ between the command and copy test conditions. Older adults aged 65+ completed a digital clock drawing to command and copy conditions. Using a Bayesian hill-climbing algorithm and bootstrapping (10,000 samples), we derived directed acyclic graphs (DAGs) to examine network structure for command and copy dCDT variables. Although the command condition showed moderate associations between variables (μ | β z | = 0.34) relative to the copy condition (μ | β z | = 0.25), the copy condition network had more connections (18/18 versus 15/18 command). Network connectivity across command and copy was most influenced by five of the 18 variables. The direction of dependencies followed the order of instructions better in the command condition network. Digitally acquired clock variables relate to one another but differ in network structure when derived from command or copy conditions. Continued analyses of clock drawing production should improve understanding of quintessential normal features to aid in early neurodegenerative disease detection.

The functional connectivity and neuropsychology underlying mental planning operations: data from the digital clock drawing test

We examined the construct of mental planning by quantifying digital clock drawing digit placement accuracy in command and copy conditions, and by investigating its underlying neuropsychological correlates and functional connectivity. We hypothesized greater digit misplacement would associate with attention, abstract reasoning, and visuospatial function, as well as functional connectivity from a major source of acetylcholine throughout the brain: the basal nucleus of Meynert (BNM). Participants (n = 201) included non-demented older adults who completed all metrics within 24 h of one another. A participant subset met research criteria for mild cognitive impairment (MCI; n = 28) and was compared to non-MCI participants on digit misplacement accuracy and expected functional connectivity differences. Digit misplacement and a comparison dissociate variable of total completion time were acquired for command and copy conditions. a priori fMRI seeds were the bilateral BNM. Command digit misplacement is negatively associated with semantics, visuospatial, visuoconstructional, and reasoning (p's < 0.01) and negatively associated with connectivity from the BNM to the anterior cingulate cortex (ACC; p = 0.001). Individuals with MCI had more misplacement and less BNM-ACC connectivity (p = 0.007). Total completion time involved posterior and cerebellar associations only. Findings suggest clock drawing digit placement accuracy may be a unique metric of mental planning and provide insight into neurodegenerative disease.

DCTclock: Clinically-Interpretable and Automated Artificial Intelligence Analysis of Drawing Behavior for Capturing Cognition

Developing tools for efficiently measuring cognitive change specifically and brain health generally—whether for clinical use or as endpoints in clinical trials—is a major challenge, particularly for conditions such as Alzheimer's disease. Technology such as connected devices and advances in artificial intelligence offer the possibility of creating and deploying clinical-grade tools with high sensitivity, rapidly, cheaply, and non-intrusively. Starting from a widely-used paper and pencil cognitive status test—The Clock Drawing Test—we combined a digital input device to capture time-stamped drawing coordinates with a machine learning analysis of drawing behavior to create DCTclock™, an automated analysis of nuances in cognitive performance beyond successful task completion. Development and validation was conducted on a dataset of 1,833 presumed cognitively unimpaired and clinically diagnosed cognitively impaired individuals with varied neurological conditions. We benchmarked DCTclock against existing clock scoring systems and the Mini-Mental Status Examination, a widely-used but lengthier cognitive test, and showed that DCTclock offered a significant improvement in the detection of early cognitive impairment and the ability to characterize individuals along the Alzheimer's disease trajectory. This offers an example of a robust framework for creating digital biomarkers that can be used clinically and in research for assessing neurological function.

Proof of concept: digital clock drawing behaviors prior to transcatheter aortic valve replacement may predict length of hospital stay and cost of care

Aims

Reduced pre-operative cognitive functioning in older adults is a risk factor for postoperative complications, but it is unknown if preoperative digitally-acquired clock drawing test (CDT) cognitive screening variables, which allow for more nuanced examination of patient performance, may predict lengthier hospital stay and greater cost of hospital care. This issue is particularly relevant for older adults undergoing transcatheter aortic valve replacement (TAVR), as this surgical procedure is chosen for intermediate-risk older adults needing aortic replacement. This proof of concept research explored if specific latency and graphomotor variables indicative of planning from digitally-acquired command and copy clock drawing would predict post-TAVR duration and cost of hospitalization, over and above age, education, American Society of Anesthesiologists (ASA) physical status classification score, and frailty.

Methods

Form January 2018 to December 2019, 162 out of 190 individuals electing TAVR completed digital clock drawing as part of a hospital wide cognitive screening program. Separate hierarchical regressions were computed for the command and copy conditions of the CDT and assessed how a-priori selected clock drawing metrics (total time to completion, ideal digit placement difference, and hour hand distance from center; included within the same block) incrementally predicted outcome, as measured by R² change significance values.

Results

Above and beyond age, education, ASA physical status classification score, and frailty, only digitally-acquired CDT copy performance explained significant variance for length of hospital stay (9.5%) and cost of care (8.9%).

Conclusions

Digital variables from clock copy condition provided predictive value over common demographic and comorbidity variables. We hypothesize this is due to the sensitivity of the copy condition to executive dysfunction, as has been shown in previous studies for subtypes of cognitive impairment. Individuals undergoing TAVR procedures are often frail and executively compromised due to their cerebrovascular disease. We encourage additional research on the value of digitally-acquired clock drawing within different surgery types. Type of cognitive impairment and the value of digitally-acquired CDT command and copy parameters in other surgeries remain unknown.

The differential impact of severe childhood trauma on emotion recognition in males and females with first-episode psychosis

Introduction

Childhood trauma increases social functioning deficits, which in turn negatively impact social inclusion in those experiencing first-episode psychosis (FEP). Associations between aberrant higher-order social cognitive processes such as emotion recognition (ER) and trauma severity may be one pathway by which trauma negatively impacts social functioning.

Objectives

Given sex differences identified in the experience of childhood trauma, it is pertinent to evaluate how trauma severity may differentially impact ER in males and females.

Methods

Eighty-three FEP participants (52 males, 31 females) and 69 nonclinical controls (49 males, 20 females) completed the CogState Research Battery. FEP participants completed the Childhood Trauma Questionnaire. A sex × group (FEP, controls) ANOVA examined ER differences and was followed by two-way ANCOVAs investigating the effects of sex and childhood trauma severity (none, low, moderate, severe) on ER and global cognition in FEP.

Results

FEP participants had significantly lower ER scores than controls (p = .035). In FEP, a significant interaction emerged between sex and childhood trauma severity (F(3, 72) = 6.382, p = .001), selective to ER, while controlling for age at onset. Simple effects analyses revealed that females in the severe trauma category exhibited superior ER capacity relative to males.

Conclusions

The differential impact of trauma severity on ER in males and females with FEP may be theoretically interpreted as the distinct way that hypervigilance affects the sexes. Early intervention services should refine social cognitive interventions in male and female trauma survivors to facilitate social functioning improvements.

Disclosure

Funding: This study was supported by the Canadian Institutes of Health Research (#68961) to M.L. and A.M. Salary awards include: The Fonds de recherche du Québec - Santé to M.L. and R.J., the James McGill Professorship to M.L., and the Canada Research Cha

Normative References for Graphomotor and Latency Digital Clock Drawing Metrics for Adults Age 55 and Older: Operationalizing the Production of a Normal Appearing Clock

BACKGROUND

Relative to the abundance of publications on dementia and clock drawing, there is limited literature operationalizing 'normal' clock production.

OBJECTIVE

To operationalize subtle behavioral patterns seen in normal digital clock drawing to command and copy conditions.

METHODS

From two research cohorts of cognitively-well participants age 55 plus who completed digital clock drawing to command and copy conditions (n = 430), we examined variables operationalizing clock face construction, digit placement, clock hand construction, and a variety of time-based, latency measures. Data are stratified by age, education, handedness, and number anchoring.

RESULTS

Normative data are provided in supplementary tables. Typical errors reported in clock research with dementia were largely absent. Adults age 55 plus produce symmetric clock faces with one stroke, with minimal overshoot and digit misplacement, and hands with expected hour hand to minute hand ratio. Data suggest digitally acquired graphomotor and latency differences based on handedness, age, education, and anchoring.

CONCLUSION

Data provide useful benchmarks from which to assess digital clock drawing performance in Alzheimer's disease and related dementias.

Cognitive Correlates of Digital Clock Drawing Metrics in Older Adults with and without Mild Cognitive Impairment

BACKGROUND

A digital version of the clock drawing test (dCDT) provides new latency and graphomotor behavioral measurements. These variables have yet to be validated with external neuropsychological domains in non-demented adults.

OBJECTIVE

The current investigation reports on cognitive constructs associated with selected dCDT latency and graphomotor variables and compares performances between individuals with mild cognitive impairment (MCI) and non-MCI peers.

METHODS

202 non-demented older adults (age 68.79 ± 6.18, 46% female, education years 16.02 ± 2.70) completed the dCDT and a comprehensive neuropsychological protocol. dCDT variables of interest included: total completion time (TCT), pre-first hand latency (PFHL), post-clock face latency (PCFL), and clock face area (CFA). We also explored variables of percent time drawing (i.e., 'ink time') versus percent time not drawing (i.e., 'think time'). Neuropsychological domains of interest included processing speed, working memory, language, and declarative memory.

RESULTS

Adjusting for age and premorbid cognitive reserve metrics, command TCT positively correlated with multiple cognitive domains; PFHL and PCFL negatively associated with worse performance on working memory and processing speed tests. For Copy, TCT, PCFL, and PFHL negatively correlated with processing speed, and CFA negatively correlated with language. Between-group analyses show MCI participants generated slower command TCT, produced smaller CFA, and required more command 'think' (% Think) than 'ink' (% Ink) time.

CONCLUSION

Command dCDT variables of interest were primarily processing speed and working memory dependent. MCI participants showed dCDT differences relative to non-MCI peers, suggesting the dCDT may assist with classification. Results document cognitive construct validation to digital metrics of clock drawing.

Cognitive and connectome properties detectable through individual differences in graphomotor organization

We investigated whether graphomotor organization during a digitized Clock Drawing Test (dCDT) would be associated with cognitive and/or brain structural differences detected with a tractography-derived structural connectome of the brain. 72 non-demented/non-depressed adults were categorized based on whether or not they used 'anchor' digits (i.e., 12, 3, 6, 9) before any other digits while completing dCDT instructions to "draw the face of a clock with all the numbers and set the hands to 10 after 11". 'Anchorers' were compared to 'non-anchorers' across dCDT, additional cognitive measures and connectome-based metrics. In the context of grossly intact clock drawings, anchorers required fewer strokes to complete the dCDT and outperformed non-anchorers on executive functioning and learning/memory/recognition tasks. Anchorers had higher local efficiency for the left medial orbitofrontal and transverse temporal cortices as well as the right rostral anterior cingulate and superior frontal gyrus versus non-anchorers suggesting better regional integration within local networks involving these regions; select aspects of which correlated with cognition. Results also revealed that anchorers' exhibited a higher degree of modular integration among heteromodal regions of the ventral visual processing stream versus non-anchorers. Thus, an easily observable graphomotor distinction was associated with 1) better performance in specific cognitive domains, 2) higher local efficiency suggesting better regional integration, and 3) more sophisticated modular integration involving the ventral ('what') visuospatial processing stream. Taken together, these results enhance our knowledge of the brain-behavior relationships underlying unprompted graphomotor organization during dCDT.

THink: Inferring Cognitive Status from Subtle Behaviors

The digital clock drawing test is a fielded application that provides a major advance over existing neuropsychological testing technology. It captures and analyzes high precision information about both outcome and process, opening up the possibility of detecting subtle cognitive impairment even when test results appear superficially normal. We describe the design and development of the test, document the role of AI in its capabilities, and report on its use over the past seven years. We outline its potential implications for earlier detection and treatment of neurological disorders. We set the work in the larger context of the THink project, which is exploring multiple approaches to determining cognitive status through the detection and analysis of subtle behaviors.

Use of pericranial flaps in the management of cranial base trauma

Pericranial flaps based on the musuloaponeurotic or myofacial layers of the scalp have great utility in the management of acquired and congenital craniofacial deformities. Their use in traumatic deformities is indicated in the presence of craniopharyngeal communications and significant anterior cranial fossa dead space created from frontal sinus obliteration. The indications and operative techniques and the results of the use of these flaps in 10 consecutive patient with extensive cranial base trauma are presented.

Intussusception: a rare cause of abdominal pain in pregnancy

A 34-year-old woman presented at 19 weeks in her third pregnancy with abdominal pain and hyperemesis. This was her third admission during the pregnancy for similar complaints. A few days after admission an exacerbation in her pain was noted, in particular on eating or lying down, and a firm and mobile epigastric mass could be palpated separate from her uterus. The differential diagnosis was a hernia or a degenerating pedunculated fibroid. Sonography revealed a mass separate from the uterus with an appearance consistent with intussusception. Magnetic resonance imaging confirmed the diagnosis. A limited right hemicolectomy was performed. The final diagnosis was adenocarcinoma of the colon. It is difficult to diagnose intussusception during pregnancy. The presenting symptoms of nausea, vomiting, abdominal pain and constipation are common in pregnancy and the displacement of the bowel by the gravid uterus hampers examination. Intussusception is very rare in adults and generally it is associated with tumors. Preoperative diagnosis is difficult but possible with accurate imaging.

Transplantation of embryonic porcine mesencephalic tissue in patients with PD

OBJECTIVE

To assess the safety and the effect on standardized clinical rating measures of transplanted embryonic porcine ventral mesencephalic (VM) tissue in advanced PD.

METHODS

Twelve patients with idiopathic PD underwent unilateral implantation of embryonic porcine VM tissue; six received cyclosporine immunosuppression and six received tissue treated with a monoclonal antibody directed against major histocompatibility complex class I. Patients were followed for 12 months and assessed by clinical examination, MRI, and 18F-levodopa PET. Porcine endogenous retrovirus testing was conducted by PCR-based method on peripheral blood mononuclear cells.

RESULTS

Cell implantation occurred without serious adverse events in all patients. Cultures were negative for bacterial and unknown viral contamination. No porcine endogenous retrovirus DNA sequences were found. MRI demonstrated cannula tracts within the putamen and caudate, with minimal or no edema and no mass effect at the transplant sites. In the medication-off state, total Unified Parkinson's Disease Rating Scale scores improved 19% (p = 0.01). Three patients improved over 30%. There were two patients with improved gait. 18F-levodopa PET failed to show changes on the transplanted side.

CONCLUSIONS

Unilateral transplantation of porcine embryonic VM cells into PD patients was well tolerated with no evidence of transmission of porcine endogenous retrovirus. Changes in standardized clinical PD rating measures were variable, similar to the results of the first trials of unilateral human embryonic allografts that transplanted small amounts of tissue.

Vernix caseosa: an unusual cause of post-cesarean section peritonitis

Surgeons should be aware of a very unusual cause of post-cesarean section peritonitis. This rare form of peritonitis is caused by the spillage of vernix caseosa material into the peritoneal cavity. The exact mechanism of the development of peritonitis in these few cases is unknown. Clinically, vernix caseosa peritonitis should be considered in the post-cesarean section acute abdomen after excluding the more common causes of peritonitis such as appendicitis and perforated viscus. Intraoperatively, the presence of cheese-like yellow patches limited to the serosal layer of visceral organs is the most characteristic feature. Histopathological examination of these serosal patches reveal the desquamated anuclear squamous cells confirming the diagnosis. Postoperative treatment with antibiotics should be continued. The addition of steroids (only after confirming the diagnosis pathologically) has a significant effect on improving the clinical outcome.

Histological evidence of fetal pig neural cell survival after transplantation into a patient with Parkinson's disease

The movement disorder in Parkinson's disease results from the selective degeneration of a small group of dopaminergic neurons in the substantia nigra pars compacta region of the brain. A number of exploratory studies using human fetal tissue allografts have suggested that transplantation of dopaminergic neurons may become an effective treatment for patients with Parkinson's disease and the difficulty in obtaining human fetal tissue has generated interest in finding corresponding non-human donor cells. Here we report a post-mortem histological analysis of fetal pig neural cells that were placed unilaterally into the caudate-putamen brain region of a patient suffering from Parkinson's disease. Long-term (over seven months) graft survival was found and the presence of pig dopaminergic neurons and other pig neural and glial cells is documented. Pig neurons extended axons from the graft sites into the host brain. Furthermore, other graft derived cells were observed several millimeters from the implantation sites. Markers for human microglia and T-cells showed only low reactivity in direct proximity to the grafts. This is the first documentation of neural xenograft survival in the human brain and of appropriate growth of non-human dopaminergic neurons for a potential therapeutic response in Parkinson's disease.

A percutaneous liver biopsy technique in ducks (Anas platyrhynchos) experimentally infected with duck hepatitis B virus

Aylesbury ducks (Anas platyrhynchos) chronically infected with the duck hepatitis B virus provide a useful model for studying hepadna-virus infection, replication and the effects of antiviral therapy. In these studies, it is necessary to have an effective method for obtaining repeat liver specimens for histological and molecular analyses. We have therefore developed a percutaneous liver biopsy technique which has a low rate of complications, can be performed at repeated intervals, and provides sufficient quantities of liver tissue for histological and nucleic acid hybridization analysis.

Hypothermia protects brain function in acute carbon monoxide poisoning

The role of body temperature in the morbidity and mortality resulting from acute severe carbon monoxide (CO) poisoning (2400 ppm CO, 90 min) was investigated using an unanesthetized animal model. Modified Levine prepared female rats (left common carotid artery and jugular cannulated) displayed a lower rate of recovery period (4 hr) re-warming, and an increased mortality rate and behaviorally-assessed neurologic index (NI) compared to normal rats. This indicated their greater susceptibility to CO hypoxia, although the degree of CO-induced hypothermia was the same in both groups. The whole-body cooling of Levine rats to a similar extent prior to CO exposure increased somewhat the post-CO re-warming rate, and marginally decreased NI and mortality during CO exposure (in-CO). In contrast, maintenance of constant body temperature by external heating during CO exposure resulted in a negative post-CO re-warming rate and sharply increased NI and in-CO mortality. Normal euthermic rats were much less severely affected by CO. The results suggest that hypothermia, whether CO-induced or produced by prior cooling, provides measurable protection of brain function during acute severe CO poisoning, and that maintenance of body temperature increases in-CO mortality and interferes with ability to thermoregulate and increases NI in survivors.

Serum markers for prediction of pulmonary radiation syndromes. Part I: Surfactant apoprotein

Detection of a biochemical marker indicating radiation lung injury prior to the onset of clinical pathologic events could prove valuable in patient management. An increased level of alveolar surfactant is one of the earliest detectable changes following lung irradiation, starting within hours of irradiation and persisting a maximum of 2-6 weeks. However, because broncho-alveolar lavage is impracticable and endothelial cell damage due to radiation results in changes in permeability of vessel wall with leakage of alveolar proteins into serum, identification of serum markers was sought. A series of experiments in rabbits are described that clearly demonstrate serum surfactant apoprotein is an accurate marker and predictor for later lethal radiation pneumonitis. At 3-7 days after graded single doses to lung, surfactant was found in the serum paralleling the dose response for lethality. Control studies with a physiologic agent such as terbutaline release alveolar surfactant, but no serum surfactant was detected. Monitoring serum surfactant could direct preventive intervention prior to clinicopathologic manifestation of pulmonary radiation syndromes.

A comparison of the adherence of fimbriated and nonfimbriated Haemophilus influenzae type b to human adenoids in organ culture

Adherence of fimbriated and nonfimbriated variants of a single strain of Haemophilus influenzae type b to organ cultures of human adenoidal tissue was measured by three assays, two of which were quantitative. In one assay, the adherence of radioactively labeled bacteria was measured; the numbers of CFU of bacteria per gram of adenoidal tissue were 16.0 +/- 6.7 for fimbriated bacteria and 10.2 +/- 4.0 for nonfimbriated bacteria (P less than 0.05). In the second assay, adherent CFU were determined directly; the results were 23.4 +/- 17.2 CFU/g of tissue for fimbriated bacteria and 5.1 +/- 2.2 CFU/g for the nonfimbriated variant (P less than 0.02). By combining data from the two assays it appears that fimbriated and nonfimbriated bacteria do not compete for the same site on the tissue, and that the adherent bacteria do not change their state of fimbriation under the assay conditions used. In contrast, the third assay, scanning electron microscopy, showed very poor adherence of nonfimbriated bacteria. Fimbriated bacteria, on the other hand, adhered in clusters to nonciliated epithelial cells. Overall, the data indicate that fimbriae enhance adherence of H. influenzae type b to a type of tissue that is a normal site of human colonization and that nonfimbriated bacteria adhere by a distinctly different mechanism.

Use of carbon labeling to demonstrate the role of blood monocytes as precursors of the 'ameboid cells' present in the corpus callosum of postnatal rats

Cells with features suggestive of ameboid motion and phagocytic properties are observed in the rat corpus callosum during the first few days of life. These cells, hereafter referred to as 'ameboid cells', have been investigated in several ways. An electron microscopic study of the corpus callosum in 5- to 7-day-old rats indicated that most 'ameboid cells' were typical macrophages, but some displayed features of monocytes, while others appeared to be transitional between the two types. These observations raised the possibility that blood monocytes were the precursors of 'ameboid cells'. This possibility was tested by injecting a suspension of carbon particles into the circulation of rats of various ages to label and trace monocytes. Within 15 minutes after injection, carbon particles were seen between cells in blood smears as well as in the lumen of capillaries, but not between cells and axons in corpus callosum. By a half hour, a few of the circulationg monocytes, and with time, up to half of them, contained carbon particles. Five days after injection, carbon particles were observed in cells of the corpus callosum identified as 'ameboid cells' of the monocytic and macrophagic type. Such carbon-containing cells were seen in many of the animals injected at the age of 0-1 day, in few of those injected at 3-5 days, and in none of the older animals. Since free carbon had not been observed in corpus callosum spaces, it was concluded that 'ameboid cells' did not pick up carbon locally. The alternative was that blood monocytes, after ingesting carbon particles in the circulation, migrated to the corpus callosum and settled as 'ameboid cells'. In the hope of obtaining a direct confirmation of this conclusion, blood cells obtained from carbon-injected Lewis rats were centrifuged in a Percoll gradient to obtain a fraction which contained 70-80% monocytes, less than 2% granulocytes, and 20-30% lymphocytes. Carbon was present in up to half of the monocytes and 1% of the granulocytes, but not in the lymphocytes; and it was calculated that over 99% of the carbon-labeled cells were monocytes. The cell fraction was then introduced into the blood circulation of 2- to 3-day-old syngeneic Lewis rats, and the animals were sacrificed 5 days later. Occasional carbon-labeled cells appeared not only in liver, spleen and connective tissue, but also in the corpus callosum, where they were identified as 'ameboid cells' of the monocytic and macrophagic type. Even though such cells were infrequent, their presence conclusively demonstrated that at least some 'ameboid cells' of the corpus callosum were derived from circulating blood monocytes.

Effects of early severe malnutrition on heart and skeletal muscle lactate dehydrogenase

Following weaning, rats from litter sizes of 15 to 20 were subjected to severe food restriction for 10 weeks, and compared to rats from litter size 5 fed ad libitum. Percent M (muscle type) lactate dehydrogenase, M and H (heart type) subunit activity and lactate dehydrogenase activity (per g wet weight) determined both electrophoretically and spectrophotometrically were all significantly lower in separated left and right ventricles of the malnourished rats. There were no differences in skeletal muscle lactate dehydrogenase activity. Following 5 weeks of ad libitum feeding, the previously malnourished rats showed large increases in body weight. Now only the right ventricle showed slight decreases in H subunit and lactate dehydrogenase activity; other measurements in the right ventricle and all in the left ventricle had returned to control levels. Skeletal muscle lactate dehydrogenase activity was not different from controls.

Effect of acute carbon monoxide poisoning on serum lactate dehydrogenase and creatine phosphokinase

Young adult rats were exposed to 1,500 ppm CO in air for 2 hr. Blood carboxyhemoglobin (COHb) concentration immediately postexposure was 55.68 +/- 0.90%. Serum lactate dehydrogenase (LDH) activity peaked at 117% above control 2 hr postexposure, while serum creatine phosphokinase (CPK) activity was maximal at 132% above control immediately following termination of exposure. Serum LDH activity declined to control within 8 hr, while serum CPK undershot controls at 8 hr and returned to the control value by 24 hr.

Hematological alterations and response to acute hypobaric stress

Exposure of rats to simulated altitude (15,000 ft) for 1 day and 3 and 9 wk produced progressive polycythemia, elevated 2,3-diphosphoglycerate levels and raised P50 values; the latter two parameters decreased toward control values after 9 wk. Carbon monoxide (38-43% HbCO) exposure produced polycythemia after 3- and 9-wk exposure, no change in 2,3-DPG and a fall in P50 value. Ten days' treatment with sodium cyanate produced a large decrease in 2,3-DPG and P50. Survival during 90 min of acute hypobaria (0.3 atm) under Nembutal anesthesia was highest with NaOCN (75%), intermediate with 3- and 9-wk exposure to altitude and CO (56-58%) lower in 1-day altitude exposure (44%) and lowest in controls (5%). Heart and ventilation rate was monitored during this hypobaric test and response patterns established for each exposure/treatment. In states of extreme oxygen deprivation the results suggest, in order of importance, the survival value of 1) increased oxygen-hemoglobin affinity, and 2) polycythemia.