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End-tidal PCO2 (end-tidal + pco2)
Selected AbstractsChanges in Cerebral Blood Flow During and After 48 H of Both Isocapnic and Poikilocapnic Hypoxia in HumansEXPERIMENTAL PHYSIOLOGY, Issue 5 2002Marc J. Poulin During acclimatization to the hypoxia of altitude, the cerebral circulation is exposed to arterial hypoxia and hypocapnia, two stimuli with opposing influences on cerebral blood flow (CBF). In order to understand the resultant changes in CBF, this study examined the responses of CBF during a period of constant mild hypoxia both with and without concomitant regulation of arterial PCO2. Nine subjects were each exposed to two protocols in a purpose-built chamber: (1) 48 h of isocapnic hypoxia (Protocol I), where end-tidal PO2 (PET,O2) was held at 60 Torr and end-tidal PCO2 (PET,CO2) at the subject's resting value prior to experimentation; and (2) 48 h of poikilocapnic hypoxia (Protocol P), where PET,O2 was held at 60 Torr and PET,CO2 was uncontrolled. Transcranial Doppler ultrasound was used to assess CBF. At 24 h intervals during and after the hypoxic exposure CBF was measured and the sensitivity of CBF to acute variations in PO2 and PCO2 was determined. During Protocol P, PET,CO2 decreased by 13% (P < 0.001) and CBF decreased by 6% (P < 0.05), whereas during Protocol I, PET,CO2 and CBF remained unchanged. The sensitivity of CBF to acute variations in PO2 and PCO2 increased by 103% (P < 0.001) and 28% (P < 0.01), respectively, over the 48 h period of hypoxia. These changes did not differ between protocols. In conclusion, CBF decreases during mild poikilocapnic hypoxia, indicating that there is a predominant effect on CBF of the associated arterial hypocapnia. This fall occurs despite increases in the sensitivity of CBF to acute variations in PO2/PCO2 arising directly from the hypoxic exposure. [source] Body Position and Cardiac Dynamic and Chronotropic Responses to Steady-State Isocapnic Hypoxaemia in HumansEXPERIMENTAL PHYSIOLOGY, Issue 2 2000S. Deborah Lucy Neural mediation of the human cardiac response to isocapnic (IC) steady-state hypoxaemia was investigated using coarse-graining spectral analysis of heart rate variability (HRV). Six young adults were exposed in random order to a hypoxia or control protocol, in supine and sitting postures, while end-tidal PCO2 (PET,CO2) was clamped at resting eucapnic levels. An initial 11 min period of euoxia (PET,O2 100 mmHg; 13.3 kPa) was followed by a 22 min exposure to hypoxia (PET,O2 55 mmHg; 7.3 kPa), or continued euoxia (control). Harmonic and fractal powers of HRV were determined for the terminal 400 heart beats in each time period. Ventilation was stimulated (P < 0.05) and cardiac dynamics altered only by exposure to hypoxia. The cardiac interpulse interval was shortened (P < 0.001) similarly during hypoxia in both body positions. Vagally mediated high-frequency harmonic power (Ph) of HRV was decreased by hypoxia only in the supine position, while the fractal dimension, also linked to cardiac vagal control, was decreased in the sitting position (P < 0.05). However, low-frequency harmonic power (Pl) and the HRV indicator of sympathetic activity (Pl/Ph) were not altered by hypoxia in either position. These results suggest that, in humans, tachycardia induced by moderate IC hypoxaemia (arterial O2 saturation Sa,O2, 85%) was mediated by vagal withdrawal, irrespective of body position and resting autonomic balance, while associated changes in HRV were positionally dependent. [source] Acute changes in carbon dioxide levels alter the electroencephalogram without affecting cognitive functionPSYCHOPHYSIOLOGY, Issue 4 2000Elisabeth Bloch-Salisbury The partial pressure of carbon dioxide in the arterial blood (PaCO2) is usually tightly regulated, yet it varies among healthy people at rest (range ,32,44 mmHg) as well as within an individual during many natural life situations. The present study examined whether modest changes in end-tidal PCO2 (PetCO2; a noninvasive measure of PaCO2) affect electroencephalographic (EEG) activity, cognitive function, and vigilance. Nine adults were ventilated mechanically using a mouthpiece; respiratory rate and breath size were held constant while PetCO2 was set to levels that produced minimal discomfort. Despite discrete changes in EEG, neither acute PetCO2 increases (mean = 47 mmHg) nor decreases (mean = 30 mmHg) from resting levels (mean = 38 mmHg) affected performance on cognitive tasks, latency or amplitude of the N1, P2, or P3 event-related potential, or alertness. Modest changes in PetCO2 may cause significant alterations in the EEG without disturbing cognitive function. [source] Evaluation of transcutaneous CO2 responses following acute changes in PaCO2 in healthy subjectsRESPIROLOGY, Issue 3 2009Satoshi FUKE ABSTRACT Background and objective: Transcutaneous blood gas-monitoring systems with miniaturized SpO2 (peripheral blood oxygen saturation)/PCO2 combined sensors (TOSCATM) have been widely used. There are no reports of the inter- and intra-individual variability in transcutaneous measurements of PaCO2 (PtcCO2) in response to acute progressive changes in PaCO2. This study examined inter- and intra-individual variability of PtcCO2 measurements under semi-steady-state conditions, and characterized the behaviour of PtcCO2 in response to acute progressive changes in PaCO2. Methods: Subjects breathed mixed gases through a mouthpiece connected to an automatic arterial blood gas controller. Using end-tidal PCO2 and PO2 as guides, PaCO2 was controlled to increase and/or decrease between baseline and , 60 mm Hg, in a stepwise (n = 9) or progressive fashion (n = 6). Arterial blood was sampled when needed. Results: Intra-individual correlation coefficients between PtcCO2 and PaCO2 were excellent in all subjects (0.971,0.989); however, the slope of the regression line varied among subjects (1.040,1.335). Bias and limits of agreement (± 2 SD from bias) between PtcCO2 and PaCO2 were ,1.8 mm Hg and ,7.7 to 4.1 mm Hg. Changes in PtcCO2 in response to acute progressive changes in PaCO2 also varied among subjects. Conclusion: The PtcCO2 measurement system allows reliable estimation of PaCO2 in a given subject. However, caution is needed when comparing absolute values between subjects or when acute changes in PaCO2 occur. [source] Cardiovascular, electrodermal, and respiratory response patterns to fear- and sadness-inducing filmsPSYCHOPHYSIOLOGY, Issue 5 2007Sylvia D. Kreibig Abstract Responses to fear- and sadness-inducing films were assessed using a broad range of cardiovascular (heart rate, T-wave amplitude, low- and high-frequency heart rate variability, stroke volume, preejection period, left-ventricular ejection time, Heather index, blood pressure, pulse amplitude and transit time, and finger temperature), electrodermal (level, response rate, and response amplitude), and respiratory (rate, tidal volume and its variability, inspiratory flow rate, duty cycle, and end-tidal pCO2) measures. Subjective emotional experience and facial behavior (Corrugator Supercilii and Zygomaticus Major EMG) served as control measures. Results indicated robust differential physiological response patterns for fear, sadness, and neutral (mean classification accuracy 85%). Findings are discussed in terms of the fight,flight and conservation,withdrawal responses and possible limitations of a valence-arousal categorization of emotion in affective space. [source] Physiologic Effects of the TASER After ExerciseACADEMIC EMERGENCY MEDICINE, Issue 8 2009Gary M. Vilke MD Abstract Objectives:, Incidents of sudden death following TASER exposure are poorly studied, and substantive links between TASER exposure and sudden death are minimal. The authors studied the effects of a single TASER exposure on markers of physiologic stress in humans. Methods:, This prospective, controlled study evaluated the effects of a TASER exposure on healthy police volunteers after vigorous exercise, compared to a subsequent, identical exercise session that was not followed by TASER exposure. Subjects exercised to 85% of predicted heart rate (HR) on an ergometer and then were given a standard 5-second TASER activation. Measures before and for 60 minutes after the TASER activation included minute ventilation, tidal volume, respiratory rate, end-tidal pCO2, oxygen saturation, HR, blood pressure (systolic BP/diastolic BP), 12-lead electrocardiogram, and arterialized blood for pH, pO2, pCO2, and lactate. Each subject repeated the exercise and data collection session on a subsequent data, without TASER activation. Data were analyzed using paired Student's t-tests with differences and 95% confidence intervals (CIs). Statistical significance was adjusted for multiple comparisons. Results:, A total of 25 officers (21 men and 4 women) completed both portions of the study. After adjusting for multiple comparisons, the TASER group was significantly higher for systolic BP at baseline (difference of 14.1, 95% CI = 8.7 to 19.5, p < 0.001) and HR at 5, 30, and 60 minutes with the largest difference at 30 minutes (difference of 7.0, 95% CI = 2.5 to 11.5, p = 0.004). There were no other significant differences between the two groups in any other measure at any time. Conclusions:, A 5-second exposure of a TASER following vigorous exercise to healthy law enforcement personnel does not result in clinically significant changes in ventilatory or blood parameters of physiologic stress. [source] | ||||||||||