Efectos beneficiosos de la respiración manejada a voluntad sobre la frecuencia cardíaca y temperatura periférica / Beneficial effects of controlled breathing on cardiac frecuency and peripheral temperature

Este estudio trató de mostrar los efectos que tenía la respiración manejada a voluntad en forma de inspiraciones cortas y espiraciones largas. El estudio se realizó con 14 sujetos, empleando 8 sesiones de tratamiento. Los resultados mostraron diferencias significativas en el descenso de la frecuencia cardíaca y en el aumento de la temperatura periférica a la finalización del tratamiento, en relación con los valores previos al tratamiento (AU)

The effect of chemoreceptor stimulation on the centripetal transfer of somatosensory information in the urethane-anaesthetized rat.

In urethane-anaesthetized rats, stimulation of carotid body chemoreceptors desynchronizes the cortical electroencephalogram and increases the sensitivity of thalamic and cortical somatosensory neurones to peripheral sensory nerve stimulation. Peripheral chemoreceptors were stimulated by injecting a bolus (30 ml) or infusing 100 ml of 0.18 M NaCl solution equilibrated with 100% CO2 into an internal carotid artery, the cortical electroencephalogram and ventilation were monitored routinely. This stimulus induced hyperventilation and desynchronization of the cortical electroencephalogram. Anaesthetized rats also showed spontaneous periodic increases in ventilation rate accompanied by changes of the cortical electroencephalogram from high-voltage low frequency to low-voltage high frequency which seemed to be identical with those evoked by stimulating chemoreceptors. The activity of identified somatosensory neurons in the thalamic ventrobasal complex, layer IV of the somatosensory cortex, or the cuneate nucleus was recorded extracellularly during and following chemoreceptor activation. Neurones in the ventrobasal thalamus and somatosensory cortex showed a decrease in latency and an increase in probability of discharge to supramaximal electrical stimulation of the forepaw which was more pronounced following infusion stimulation of the carotid body than following bolus stimulation. In contrast, neurons within the cuneate nucleus showed a slight increase in latency to onset and a decrease in the probability of firing following the same stimulus. The results indicate that stimulation of the carotid body chemoreceptors leads to an enhancement of the response of somatosensory neurons to their normal physiological input.

Effect of reduced body weight on muscle aerobic capacity in patients with COPD.

BACKGROUND: Reduced muscle aerobic capacity in COPD patients has been demonstrated in several laboratories by phosphorus magnetic resonance spectroscopy and by analysis of oxygen uptake (VO2) kinetics. COPD patients are usually elderly, hypoxemic, poorly active with muscle atrophy, and often malnourished. Under these conditions there is usually reduction of O2 delivery to the tissues (bulk O2 flow), redistribution of fiber type within the muscle, capillary rarefaction, and decreased mitochondrial function, alterations all capable of reducing muscle aerobic capacity. In COPD, the effect of reduced body mass on muscle aerobic capacity has not been investigated (to our knowledge). METHODS: We studied 24 patients with stable COPD with moderate-to-severe airway obstruction (68+/-5 [SD] years; FEV1, 39+/-12% predicted; PaO2, 66+/-8 mm Hg; PaCO2, 41+/-3 mm Hg) with poor to normal nutritional status, as indicated by a low-normal percent of ideal body weight (IBW). Each subject first underwent 1-min maximal incremental cycle ergometer exercise for determination of VO2 peak and lactate threshold (LT). Subsequently, they performed a 10-min moderate (80% of LT-VO2) constant load exercise for determination of oxygen deficit (O2DEF) and mean response time VO2 (MRT). VO2, CO2 output (VCO2), and minute ventilation were measured breath by breath. RESULTS: Patients displayed low VO2 peak (1,094+/-47 [SE] mL/min), LT-VO2 (35+/-3% predicted O2 max), and higher MRT-VO2 (67+/-4 s). Univariate regression analysis showed that percent of IBW correlated with indexes of maximal and submaximal aerobic capacity: vs VO2 peak, R=0.53 (p<0.01); vs MRT R=-0.77 (p<0.001). Using stepwise regression analysis, MRT correlated (R2=-0.70) with percent of IBW (p<0.01) and with PaO2 (p<0.05). CONCLUSIONS: Reduced body mass has an independent negative effect on muscle aerobic capacity in COPD patients: this effect may explain the variability in exercise tolerance among patients with comparable ventilatory limitation.

Ventilatory and metabolic responses to cold and hypoxia in conscious rats with discrete hypothalamic lesions.

We tested the hypothesis that hypothalamic nuclei involved in thermoregulatory control could represent a site of integration of the metabolic and ventilatory response to cold and hypoxia. Electrolytic lesions were performed bilaterally under stereotaxic guide, either within the anterior or posterior hypothalamic areas of adult rats. One week later, oxygen consumption (VO2) and ventilation (VE) were measured in the conscious animals during warm (27 degrees C) or cold (12 degrees C) conditions, in normoxia (21% O2) or hypoxia (10% O2), and compared to measurements obtained in control rats, which were either intact or sham-operated. VO2, VE, and body temperature did not differ between lesioned and control rats during warm normoxia. In cold and hypoxia, singly or combined, VE/VO2 was higher in the lesioned rats, because of higher VE. The differences in the cold were mostly confined to rats with anterior lesions, whereas differences in hypoxia were mostly in rats with posterior lesions. We conclude that the integrity of the anterior and posterior hypothalamic areas is important for the proper coupling of metabolism and ventilation during cold or hypoxic stimuli.

The Verbalizer-Visualizer Questionnaire: a review.

The psychometric properties of Richardson's 1977 Verbalizer-Visualizer Questionnaire have been studied by analyzing papers in which this questionnaire was employed. Such review showed that the Verbalizer-Visualizer Questionnaire does not measure a unidimensional construct and does not predict the actual use of mental imagery in thinking. Further, a lack of long-term reliability of the questionnaire emerged. In conclusion, use of the questionnaire to assess the verbal-visual cognitive style appears questionable.

Different strategies of modulation can be operative during hypnotic analgesia: a neurophysiological study.

Nociceptive electrical stimuli were applied to the sural nerve during hypnotically-suggested analgesia in the left lower limb of 18 highly susceptible subjects. During this procedure, the verbally reported pain threshold, the nociceptive flexion (RIII) reflex and late somatosensory evoked potentials were investigated in parallel with autonomic responses and the spontaneous electroencephalogram (EEG). The hypnotic suggestion of analgesia induced a significant increase in pain threshold in all the selected subjects. All the subjects showed large changes (i.e., by 20% or more) in the amplitudes of their RIII reflexes during hypnotic analgesia by comparison with control conditions. Although the extent of the increase in pain threshold was similar in all the subjects, two distinct patterns of modulation of the RIII reflex were observed during the hypnotic analgesia: in 11 subjects (subgroup 1), a strong inhibition of the reflex was observed whereas in the other seven subjects (subgroup 2) there was a strong facilitation of the reflex. All the subjects in both subgroups displayed similar decreases in the amplitude of late somatosensory evoked cerebral potentials during the hypnotic analgesia. No modification in the autonomic parameters or the EEG was observed. These data suggest that different strategies of modulation can be operative during effective hypnotic analgesia and that these are subject-dependent. Although all subjects may shift their attention away from the painful stimulus (which could explain the decrease of the late somatosensory evoked potentials), some of them inhibit their motor reaction to the stimulus at the spinal level, while in others, in contrast, this reaction is facilitated.

Craniosacral rhythm: reliability and relationships with cardiac and respiratory rates.

Craniosacral rhythm (CSR) has long been the subject of debate, both over its existence and its use as a therapeutic tool in evaluation and treatment. Origins of this rhythm are unknown, and palpatory findings lack scientific support. The purpose of this study was to determine the intra- and inter-examiner reliabilities of the palpation of the rate of the CSR and the relationship between the rate of the CSR and the heart or respiratory rates of subjects and examiners. The rates of the CSR of 40 healthy adults were palpated twice by each of two examiners. The heart and respiratory rates of the examiners and the subjects were recorded while the rates of the subjects' CSR were palpated by the examiners. Intraclass correlation coefficients were calculated to determine the intra- and inter-examiner reliabilities of the palpation. Two multiple regression analyses, one for each examiner, were conducted to analyze the relationships between the rate of the CSR and the heart and respiratory rates of the subjects and the examiners. The intraexaminer reliability coefficients were 0.78 for examiner A and 0.83 for examiner B, and the interexaminer reliability coefficient was 0.22. The result of the multiple regression analysis for examiner A was R = 0.46 and adjusted R2 = 0.12 (p = 0.078) and for examiner B was R = 0.63 and adjusted R2 = 0.32 (p = 0.001). The highest bivariate correlation was found between the CSR and the subject's heart rate (r = 0.30) for examiner A and between the CSR and the examiner's heart rate (r = 0.42) for examiner B. The results indicated that a single examiner may be able to palpate the rate of the CSR consistently, if that is what we truly measured. It is possible that the perception of CSR is illusory. The rate of the CSR palpated by two examiners is not consistent. The results of the regression analysis of one examiner offered no validation to those of the other. It appears that a subject's CSR is not related to the heart or respiratory rates of the subject or the examiner.

Low load inspiratory muscle training increases diaphragmatic fiber dimensions in rats.

The effects of 8 wk of inspiratory resistive loading (30 min/d, 3 x/wk) on diaphragm mass, contractile properties, fatigue, and fiber dimensions were studied in 10 male Wistar rats. They were conditioned to breathe through a Hans-Rudolph device. Half of them had to overcome a moderate inspiratory resistance (MR; n = 5), whereas the others only had to overcome the small resistance (SR; n = 5) of the inspiratory valve of the device. Results were compared with control rats (C; n = 5) moving and breathing freely. At the end of training, animals submitted to MR and SR generated mean inspiratory pressures of -2.5 +/- 1.1 and -0.2 +/- 0.05 cm H2O, respectively. TI/Ttot was 0.60 +/- 0.06 and 0.57 +/- 0.05, respectively. Body and diaphragm weight were unaffected by loading. Little or no change in in vitro diaphragmatic twitch kinetics, force generation, and fatigability was found between the three groups. Nevertheless, cross-sectional area of all fiber types increased in the two loaded groups compared with control animals. This increase reached statistical significance for type I fibers in the MR group (846 +/- 74 microm2) compared with the C and SR groups (589 +/- 32 and 683 +/- 96 microm2, respectively, p < 0.05). For IIa fibers both training groups were significantly different from the control group (SR: 768 +/- 99 and MR: 790 +/- 108 versus C: 592 +/- 37 microm2, p < 0.05). A hypertrophy of type IIx/b fibers was seen in MR compared with control animals (C: 1,555 +/- 136, SR: 1,845 +/- 338, MR: 2,053 +/- 326 microm2, p < 0.05). No differences were present in fiber type proportions between the three groups. We conclude that in our training setup, 8 wk of intermittent long-term inspiratory loading stressed the diaphragm already with a small resistance resulting in hypertrophy of predominantly type IIa fibers. A higher resistance resulted in hypertrophy of all fiber types.

Respiratory and arousal responses to acoustic stimulation.

STUDY OBJECTIVES: Although sleep-related obstructive apnea is most often associated with transient arousal, the impact of this arousal on respiratory control remains unclear. We tested the hypotheses that acoustic arousing stimulation can generate a significant respiratory response during sleep in healthy subjects and that the magnitude or timing of this response is affected by the presence of electrocortical arousal or inhaled carbon dioxide. DESIGN: We employed binaural tone bursts (0.5-s duration, 4-KHz center frequency, 99-s interstimulus interval) to elicit repetitive transient arousals from sleep during nocturnal polysomnographic recordings beginning at 10 PM and ending at 6 AM. PARTICIPANTS: Recordings were conducted in five healthy adult volunteers aged 24 to 37 years. INTERVENTIONS: Inspired gas was alternated between room air and 3% to 7% CO2 (titrated to yield an approximate 50% increase in minute ventilation) at 1-h intervals. MEASUREMENTS AND RESULTS: Each 30-s epoch was scored for sleep/wake stage according to standard criteria. Only results obtained during nonrapid eye movement sleep are presented herein. Tone-evoked arousals were detected by computer analysis as increased EEG frequency occurring within 3 s of acoustic stimulation. For each tone, respiratory parameters for each of three prestimulus and four poststimulus breaths were normalized to the overall mean of prestimulus breaths measured during room air breathing for each subject. Tone bursts elicited repetitive transient arousals with a mean duration of approximately 10 s from all stages of sleep. With respect to the three prestimulus breaths, acoustic stimulation was associated with increased tidal volume and decreased inspiratory duration for at least four breaths. These respiratory responses to acoustic stimulation were not significantly influenced by either presence of transient arousal from sleep or inspired gas. CONCLUSIONS: We conclude that transient EEG arousal may be repeatedly evoked from nonrapid eye movement sleep by transient acoustic stimulation in normal sleepers. This sensory stimulation is associated with augmented ventilation, a response that is not significantly affected by inspired hypercapnia or the presence of generalized EEG arousal.

Behavioural and autonomic responses to sound in pre-term and full-term babies.

The pattern of motor (body movement) and autonomic (heart rate and respiration) responses to no sound and sound trials were compared in 20 pre-term and 22 full-term neonates. Sound levels were calibrated using neonatal ear-sized couplers to produce, in the neonatal ear, sound levels of 80, 90 and 100 dB SPL. Accelerations in heart rate (> or = beats per minute for pre-terms; > or = 7 beats per minute for full-terms) were found to be the best criterion for establishing a possible response using bandpass noise at 80, 90 or 100 dB SPL. Respiration rate decreased in response to sound stimuli, this being significant for the pre-term group for the 100 dB SPL stimulus when comparing the 5 s period post-stimulus with the stimulus period. The number of movements detected during the sound trials was higher than for the control trials, being statistically significant for the pre-term group. These changes were elicited in response to stimuli presented at levels some 20-40 dB lower than for other studies and for behavioural screening because sounds were calibrated in an appropriately sized coupler. It is concluded that the response to sound is different in the pre-term group compared with the full-term group.

Effects of supplemental ascorbic acid on the energy conversion of broiler chicks during heat stress and feed withdrawal.

The objectives of this study were 1) to determine the effects of supplemental ascorbic acid (AA) on the energy conversion of broiler chicks maintained at thermoneutral and potential heat stress temperatures using indirect convective calorimetry; and 2) to determine whether changes in energy conversion are reflected in changes in lipid metabolism. In Experiment 1, 120 2-d-old cockerels, housed in two identical environmental chambers, were maintained under constant light (2.0 +/- 0.2 fc) and recommended thermal conditions (29.6 +/- 0.8 C; 33.4 +/- 8.0% RH) and consumed water and feed ad libitum. Beginning on Day 8 posthatch, one-half of the birds inside each chamber were randomly assigned and received feed supplemented with AA. Beginning on Day 9 posthatch, the temperature inside one chamber was increased to 34 C whereas the other chamber remained thermoneutral. This design resulted in four treatments: 1) thermoneutral (TN: 27.7 +/- 0.8 C; 40.9 +/- 9.4% RH) and 0 mg AA/kg feed (ppm); 2) TN and 150 ppm AA; 3) heat stress (H: 33.8 +/- 0.5 C; 43.3 +/- 7.4% RH) and 0 ppm AA; or 4) H and 150 ppm AA. Also beginning on Day 9 posthatch, birds were randomly assigned to one of three identical, indirect convective calorimeters designed to accommodate TN or H. Oxygen consumption, carbon dioxide production, respiratory quotient, and heat production were evaluated daily for 8 h, through Day 17 posthatch. Following calorimetric measurement, birds were returned to their respective caging unit/chamber for the remainder of the study. Weight gain, feed intake, and gain: feed were also measured over the 9-d study. Heat exposure depressed (P < 0.05) weight gain, feed intake, and gain:feed. Ascorbic acid increased (P < 0.10) weight gain. Oxygen consumption and carbon dioxide and heat production per kilogram0.75 decreased (P < 0.05) with age with no change in the respiratory quotient. Heat exposure lowered (P < 0.001) the respiratory quotient. A temperature by AA interaction was detected in which heat-exposed birds expressed lower (P < 0.10) respiratory quotients when consuming the AA-supplemented diet. In Experiment 2, 18 2-d-old cockerels, housed in an environmental chamber, were maintained under constant light and recommended thermal conditions (29.3 +/- 0.4 C; 41.4 +/- 3.3% RH) and consumed water and feed ad libitum. On Day 9 posthatch, birds were deprived of feed for 24 h with ad libitum access to water supplemented with either 0 or 400 mg AA/L. Blood samples were obtained from each bird before and after feed withdrawal and supplementation. Supplemented birds exhibited elevated (P < 0.01) plasma AA, levels that were not affected by feed deprivation. Feed deprivation increased (P < 0.0001) plasma beta-hydroxybutyrate with no effect of AA, and decreased (P < 0.05) plasma triglycerides in the unsupplemented birds. A feed withdrawal by AA interaction was detected in which plasma triglycerides remained elevated in birds supplemented with AA. These data suggest that supplemental AA influences body energy stores that are used for energy purposes during periods of reduced energy intake.

Low-frequency (< 1 Hz) oscillations in the human sleep electroencephalogram.

Low-frequency (< 1 Hz) oscillations in intracellular recordings from cortical neurons were first reported in the anaesthetized cat and then also during natural sleep. The slow sequences of hyperpolarization and depolarization were reflected by slow oscillations in the electroencephalogram. The aim of the present study was to examine whether comparable low-frequency components are present in the human sleep electroencephalogram. All-night sleep recordings from eight healthy young men were subjected to spectral analysis in which the low-frequency attenuation of the amplifier was compensated. During sleep stages with a predominance of slow waves and in the first two episodes of non-rapid-eye-movement sleep, the mean power spectrum showed a peak at 0.7-0.8 Hz (range 0.55-0.95 Hz). The typical decline in delta activity from the first to the second non-rapid-eye-movement sleep episode was not present at frequencies below 2 Hz. To detect very low frequency components in the pattern of slow waves and sleep spindles, a new time series was computed from the mean voltage of successive 0.5 s epochs of the low-pass (< 4.5 Hz) or band-pass (12-15 Hz) filtered electroencephalogram. Spectral analysis revealed a periodicity of 20-30 s in the prevalence of slow waves and a periodicity of 4 s in the occurrence of activity in the spindle frequency range. The results demonstrate that distinct components below 1 Hz are also present in the human sleep electroencephalogram spectrum. The differences in the dynamics between the component with a mean peak value at 0.7-0.8 Hz and delta waves above 2 Hz is in accordance with results from animal experiments.

Waking up the gastric bypass patient.

Waking up the gastric bypass patient in the post-anesthesia care unit (PACU) is a continual challenge. From January 1992 to November 1996, 961 gastric bypasses (GBP) have been performed at Columbia St Mark's Hospital. Of the 961 patients, 957 came to the PACU. Four patients went directly to ICU because of respiratory status requiring mechanical ventilation. There have been no deaths and no respiratory arrests in PACU. Continuous bedside monitoring of the patient's respiratory status coupled with pain management contributed to positive care of the GBP patient. Methods of care for the GBP patient include the use of O2 masks and cannulas, coughing and deep breathing, administering i.v. narcotics until patient controlled analgesia pumps are initiated, encouragement and emotional support, ongoing assessment of patients' status, and treating problems/needs appropriately.

Nitric oxide increases cutaneous and respiratory heat dissipation in conscious rabbits.

The influence of systemic nitric oxide (NO) donor infusion and NO synthase inhibition on major thermoregulatory mechanisms was investigated under thermoneutral conditions (24 degrees C) in the conscious rabbit. Both low (25 nmol.min-1.kg-1) and high-dose (75 nmol.min-1.kg-1) infusion of the NO donors 3-morpholinosydnonimine-hydrochloride and S-nitroso-N-acetylpenicillamine augmented respiratory heat dissipation due to raised respiratory frequency (RF) and evaporative water loss (REWL). At the higher dose of NO donor, RF and REWL increased (from 107 +/- 16 to 156 +/- 19 breaths/min and from 7.12 +/- 0.97 to 11.29 +/- 1.29 mg.min-1.kg-1; P < 0.05), and, combined with a moderate rise in cutaneous heat dissipation (ear skin temperature increased from 29.03 +/- 1.76 to 33.29 +/- 2.71 degrees C; P < 0.05), deep body temperature was slightly reduced (-0.1 degrees C, P > 0.05) without a change in metabolic heat production. In contrast, blockade of endogenous NO synthesis induced a sustained rise in body temperature (0.2 degrees C, P < 0.05), concomitant with a reduction in both RF and REWL (from 131 +/- 11 to 94 +/- 12 breaths/min and from 10.86 +/- 1.14 to 8.70 +/- 0.88 mg.min-1.kg-1, P < 0.05), whereas metabolic heat production decreased slightly and cutaneous heat dissipation was minimally altered. The data indicate that, under thermoneutral conditions, systemically applied NO primarily influences body temperature in the conscious rabbit by modulating the rate of respiratory heat dissipation, whereas the roles of cutaneous heat dissipation and metabolic heat production are relatively minor.

Respiratory sinus arrhythmia versus neck/trapezius EMG and incentive inspirometry biofeedback for asthma: a pilot study.

This pilot study compared biofeedback to increase respiratory sinus arrhythmia (RSA) with EMG and incentive inspirometry biofeedback in asthmatic adults. A three-group design (Waiting List Control n = 5, RSA biofeedback n = 6, and EMG biofeedback n = 6) was used. Six sessions of training were given in each of the biofeedback groups. In each of three testing sessions, five min. of respiratory resistance and EKG were obtained before and after a 20-min biofeedback session. Additional five-min epochs of data were collected at the beginning and end of the biofeedback period (or, in the control group, self-relaxation). Decreases in respiratory impedance occurred only in the RSA biofeedback group. Traub-Hering-Mayer (THM) waves (.03-.12 Hz) in heart period increased significantly in amplitude during RSA biofeedback. Subjects did not report significantly more relaxation during EMG or RSA biofeedback than during the control condition. However, decreases in pulmonary impedance, across groups, were associated with increases in relaxation. The results are consistent with Vaschillo's theory that RSA biofeedback exercises homeostatic autonomic reflex mechanisms through increasing the amplitude of cardiac oscillations. However, deep breathing during RSA biofeedback is a possible alternate explanation.

Hyperventilation syndrome: a chimera?

There is now an impressive body of research to suggest that the concept of a discrete hyperventilation syndrome is no longer tenable. The evidence for this has been carefully gathered and the scientific studies have employed innovative methodological techniques and have introduced a key psychological dimension. Both have led to a greater understanding of the respiratory correlates of anxiety, but in the process have revealed the "hyperventilation syndrome" to be a chimera. Furthermore, there is no evidence to support the view that panic attacks and hyperventilation are synonymous: on the contrary, hyperventilation rarely accompanies panic and, when it does, it is more likely to be a consequence than a cause of the panic. Finally, there is no evidence that "breathing therapy" works by normalizing pCO2; its nonspecific effects on anxiety appear to be mediated in part by slowing respiratory rate. Further research in this field might be more profitably focused on the nature of the association between anxiety disorders and organic lung disease, especially asthma.

Reduced asthma symptoms with n-3 fatty acid ingestion are related to 5-series leukotriene production.

Asthma may respond to dietary modification, thereby reducing the need for pharmacologic agents. This study determined the effectiveness of n-3 polyunsaturated fatty acid (PUFA) ingestion in ameliorating methacholine-induced respiratory distress in an asthmatic population. The ability of urinary leukotriene excretion to predict efficacy of n-3 PUFA ingestion was assessed. After n-3 PUFAs in ratios to n-6 PUFAs of 0.1:1 and 0.5:1 were ingested sequentially for 1 mo each; patient respiratory indexes were assessed after each treatment. Forced vital capacity (FVC), forced expiratory volume for 1 s (FEV1), peak expiratory flow (PEF), and forced expiratory flow 25-75% (FEF 25-75) were measured along with weekly 24-h urinary leukotriene concentrations. With low n-3 PUFA ingestion, methacholine-induced respiratory distress increased. With high n-3 PUFA ingestion, alterations in urinary 5-series leukotriene excretion predicted treatment efficacy. Elevated n-3 PUFA ingestion resulted in a positive methacholine bronchoprovocation dose change in > 40% of the test subjects (responders). The provocative dose to cause a 20% reduction (PD20) in FEV1, FVC, PEF, and FEF25-75 values could not be calculated because of a lack of significant respiratory reduction. Conversely, elevated n-3 PUFA ingestion caused some of the patients (nonresponders) to further lose respiratory capacity. Five-series leukotriene excretion with high n-3 PUFA ingestion was significantly greater for responders than for nonresponders. A urinary ratio of 4-series to 5-series leukotrienes < 1, induced by n-3 PUFA ingestion, may predict respiratory benefit.

Variability in breathing patterns during latent labor. A pilot study.

This study examined the breathing patterns of a small sample of women (n = 21) during latent labor. The study also examined the different thoughts or cognitions the women experienced during their early contractions and assessed whether these cognitions, when classified as associative or dissociative in orientation, were related to breathing styles and length of labor. Respiration rate and tidal volume were monitored during and between contractions using a noninvasive plethysmograph system. The breathing results indicated considerable variation among women in individual respiration rate and tidal volume both between and during contractions. In addition, marked variability was found in both the direction and degree of change in breathing frequency and tidal volume in response to contractions. Women who relied predominantly on associative strategies during early labor had lower breathing rates and higher tidal volumes than did women who employed dissociative strategies.

The protective effect of beta-carotene and retinol on ventilatory function in an asbestos-exposed cohort.

The association between serum beta-carotene or retinol concentration and level of ventilatory function was investigated in a population of asbestos-exposed men with a high rate of current and former cigarette smoking. The study population consisted of 816 subjects enrolled in the pilot component of the Carotene and Retinol Efficacy Trial (CARET), a placebo-controlled trial of supplemental beta-carotene and retinyl palmitate for the chemoprevention of lung cancer. Data available for analysis included baseline questionnaire, spirometry, chest X-ray, food frequency questionnaire, and serum beta-carotene and retinol concentrations. Serum beta-carotene concentration was associated with FEV1 (p < 0.05) and FVC (p < 0.05), with an approximately 100-ml increase over predicted values associated with raising the serum concentration from the 25th to the 75th percentile of the distribution in the study population (absolute difference = 155 ng/ml), even after adjustment for the confounding effects of asbestos exposure and cigarette smoking. Raising the serum retinol concentration from the 25th to the 75th percentile (absolute difference = 211 ng/ml) was associated with an approximately 70 ml increase in FVC (p < 0.05) over the predicted value. These results provide support for the hypothesis that beta-carotene and retinol have a protective effect on loss of ventilatory function.