Effect of blood flow on capillary transit time and oxygenation in excised rabbit lung.

We used an isolated perfused lung preparation of the rabbit to study the effect of increasing blood flow on pulmonary capillary transit time by two methods. In one method, capillary transit time was measured from fluorescent dye dilution curves from arterioles and venules of the subpleural microcirculation. Values of transit time were similar to those for the whole lung determined by dividing capillary blood volume by blood flow.

Effects of changes in ventilation on respiratory discomfort during isocapnic exercise.

We studied the effects of changes in the level of ventilation on respiratory discomfort during isocapnic exercise. Six subjects exercised at 60 W on a cycle ergometer. They initially breathed 2.

Temporal variations in the pattern of breathing.

Breath-to-breath variations in the pattern of breathing can occur as uncorrelated random variations ("white noise"), correlated random changes, or as one of two types of nonrandom variations: periodic oscillations or nonrandom nonperiodic fluctuations. White noise is probably present in all physiological processes. In many cases, periodic variations are due to oscillations originating in chemoreflex feedback loops.

A longitudinal study of the grief of mothers and fathers of children with intellectual disability.

As a follow-up to a single-point-in-time study which suggested support for the proposition that grieving is an ongoing feature of parenting children with intellectual disability, the present investigation reports findings based on annual interviews conducted over a three-year period. Longitudinal outcomes on measures used to define grief largely confirmed the original findings. Of particular interest were (a) indications of the presence of grief over time (b) the finding that the 49 mothers and 49 fathers report similar intensity of continued wishing for what might have been, and (c) the conclusion that the responses of the mothers on the Impact of Event Scale and to current levels of distress when thinking about time of diagnoses are significantly more intense than those of the fathers.

Ventilatory stability to CO2 disturbances in wakefulness and quiet sleep.

Oscillatory ventilatory pattern occurs more frequently in sleep despite the stabilizing factor of sleep-induced reduction in CO2 chemosensitivity. In nine young normal humans, we have tested the hypothesis that, despite a sleep-induced reduction in chemosensitivity, the transient central chemoreceptor-mediated change inspiratory ventilation (VI) caused by a standardized disturbance to chemoreflex ventilatory control is similar in quiet sleep and wakefulness. The equivalent VI response to a single-breath hyperoxic hypercapnic stimulus (i.

Estimation of hypoxic ventilatory dynamics using pseudorandom inputs.

Using experimental and simulation studies, we assessed the applicability of pseudorandom binary hypoxic stimulation (PRBS) for estimating the dynamic respiratory response to a single breath of hypoxia. In experimental studies on rats we tested whether the transient ventilatory response to hypoxia based on the PRBS technique converges to the measured response to a true single breath of hypoxia. Plethysmographic volume recordings were obtained from 7 urethane anesthetized, bilaterally vagotomized rats while the inspired O2 level was switched pseudorandomly between 21% and 12%.

Override of spontaneous respiratory pattern generator reduces cardiovascular parasympathetic influence.

We investigated the effects of voluntary control of breathing on autonomic function in cardiovascular regulation. Variability in heart rate was compared between 5 min of spontaneous and controlled breathing. During controlled breathing, for 5 min, subjects voluntarily reproduced their own spontaneous breathing pattern (both rate and volume on a breath-by-breath basis).

Myofascial pain syndrome: early recognition and comprehensive management.

Fewer conditions in clinical practice have generated more controversy and debate than those that cause musculoskeletal pain and dysfunction. The term myofascial pain refers to a syndrome of musculoskeletal discomfort. Myofascial pain is a significant physical disorder responsible for long term disability.

Voluntary control of breathing does not alter vagal modulation of heart rate.

Variations in respiratory pattern influence the heart rate spectrum. It has been suggested, hence, that metronomic respiration should be used to correctly assess vagal modulation of heart rate by using spectral analysis. On the other hand, breathing to a metronome has been reported to increase heart rate spectral power in the high- or respiratory frequency region; this finding has led to the suggestion that metronomic respiration enhances vagal tone or alters vagal modulation of heart rate.

Physicians' knowledge of drug costs for the elderly.

Objective: To measure physicians' knowledge of the costs of commonly used medications in geriatric practice and how such awareness influences their prescribing decisions.

Design: A survey of pharmacies to determine the prices of 14 commonly used brand name and generic drugs and an in-person survey of physicians asking them to price these drugs.

Setting: Eastern Massachusetts.

Ventilatory variability induced by spontaneous variations of PaCO2 in humans.

We tested the hypothesis that breath-to-breath variations in arterial CO2 partial pressure (PaCO2) during spontaneous breathing of awake humans cause a significant portion of spontaneous ventilatory variability (including periodic oscillations). This hypothesis was tested in two ways. First, using a recently developed adaptive PaCO2 buffering technique we reduced the spontaneous variability in PaCO2 of six awake normal young human subjects during hyperoxia and observed a corresponding decrease in their breath-to-breath ventilatory variations.

Grieving related to development: a preliminary comparison of three age cohorts of parents of children with intellectual disability.

It is argued that a child with intellectual disability represents an ongoing source of loss and grief for parents. A developmental framework was employed to compare three age cohorts of parents. Grief was operationalized within the affective, behavioural and cognitive domains.

Adaptive buffering of breath-by-breath variations of end-tidal CO2 of humans.

We have designed and implemented a computer-controlled system that uses an adaptive control algorithm (generalized minimum variance) to buffer the breath-by-breath variations of the end-tidal CO2 fraction (FETCO2) that occur spontaneously or are exaggerated in certain experimental protocols (e.g., induced hypoxia, any type of induced variations in the ventilatory pattern).

Hyperoxic exposure of developing rat lung decreases tropoelastin mRNA levels that rebound postexposure.

These studies were undertaken to determine whether tropoelastin message expression in lung parenchymal tissue is altered in rats reared in an hyperoxic environment during the period of time that alveolar septation normally occurs. Rat pups were exposed to > 95% oxygen from days 4 to 14 and killed during the exposure and recovery periods. Results of in situ hybridizations indicated a delay in peak tropoelastin (TE) message levels in oxygen-exposed rats vs.

Bifurcations of the respiratory pattern produced with phasic vagal stimulation in the rat.

Geometric methods from nonlinear dynamics are employed to evaluate dynamic processing of vagal afferent information by the respiratory central pattern generator (RCPG). While measuring airflow and diaphragm EMG, we applied brief electrical stimuli (40- to 130-ms duration) to one afferent vagus of bilaterally vagotomized urethan-anesthetized rats during every breath at various phases of the respiratory cycle. Stimuli applied during early or late inspiration of every breath evoke highly predictable one-dimensional responses: reversible (graded inhibition) or irreversible (off-switching) inhibition of inspiratory activity, respectively.

Role of deflation-sensitive feedback in control of end-expiratory volume in rats.

Rats breathing from reduced end-expiratory volumes (EEV) exhibit transient bursting of inspiratory airflow local to the expiratory-inspiratory transition (E-I) accompanied by increases in inspiration-to-expiration duration ratio. Continuous positive (CPAP) and negative (CNAP) airway pressures (+3 to -9 cmH2O) were applied to tracheal openings of 17 unilaterally vagotomized rats (urethan anesthetized) to evaluate the feedback mechanisms associated with these oscillatory "expiratory interrupts." Whole nerve recordings of afferent vagus (Vag) were primarily inspiratory with CPAP.

Bifurcations of the respiratory pattern associated with reduced lung volume in the rat.

Rats with intact vagal reflexes exhibit patterns of breathing that contain greater degrees of freedom than those seen after vagotomy. To determine how alterations in end-expiratory volume modify the respiratory pattern, continuous positive (CPAP) and negative (CNAP) airway pressure was applied to tracheal openings of nine urethan-anesthetized vagi-intact rats (+3 to -9 cmH2O). Phase portraits (e.

The carotid body in the motorneuron response to protriptyline.

Protriptyline (PRT) has been shown to preferentially stimulate upper airway inspiratory motorneurons relative to phrenic activity in hyperoxic hypercapnia in the decerebrate cat via a carotid body-independent mechanism. Since previous studies indicated that carotid body stimulation results in preferential activation of upper airway respiratory muscles during both hypercapnia and hypoxemia, we hypothesized that if PRT preferentially stimulated upper airway motorneurons, the mechanism of action might involve the carotid body. We investigated the effect of PRT on carotid body function by comparing the electrical activity of the hypoglossal (HYP) with that of the phrenic (PHR) nerve in carotid sinus nerve intact (CSNI) and CSN-sectioned (CSNX) anesthetized rats, before and after PRT (0.

Thrombosis of the portal vein in eleven dogs.

Case records from the small animal necropsy service of the University of Pennsylvania (Philadelphia, PA) from January 1981 through August 1990 were searched for reports of animals with grossly visible portal vein thrombi. Eleven dogs identified from their case materials as having portal vein thrombosis were used for this study. The age of the dogs ranged from 2 to 13 years, and there were five spayed females and six males--four intact and two castrated.

Long-lasting ventilatory response of humans to a single breath of hypercapnia in hyperoxia.

It has often been assumed that under normoxia, closed-loop ventilatory responses to transient CO2 stimulation (i.e., lasting for 1-3 breaths) are less likely to be mediated by the slow-responding central (medullary) chemoreflex.

The role of midline ventral medullary structures in generation of respiratory motor high frequency oscillations.

Lesions 1-2 mm deep in the midline of the ventral medulla (VM) abolished high frequency oscillations (HFO) in the respiratory motor output in cat and rabbit. Raising arterial pCO2 increased phrenic nerve activity to its prelesion level but did not restore HFO. We conclude that the neuronal pathways crossing the midline of the VM are crucial for reinforcement of respiratory activity and HFO generation.

Cardiorespiratory responses to glutamatergic antagonists in the caudal ventrolateral medulla of rats.

The role of caudal ventrolateral medullary (CVLM) depressor neurons in influencing arterial pressure and ventilation as well as the baroreflex control of arterial pressure was investigated, and the part played by excitatory N-methyl-D-aspartate (NMDA) and non-NMDA receptors in mediating the responses was determined. In urethane-anesthetized, spontaneously breathing rats unilateral microinjections into the caudal depressor area of the broad-band glutamatergic antagonist kynurenic acid (KYN, 5 nmol or 1.58 nmol), or NMDA antagonist 2-amino-5-phosphonovaleric acid (2-APV, 2.

Mathematical model of cellular basis for the respiratory sinus arrhythmia.

The respiratory sinus arrhythmia (RSA) is a vagally mediated oscillation in cardiac cycle length at the frequency of breathing. We developed a mathematical model that predicted the temporal and frequency dependence of the RSA. We used the mathematical model to examine the underlying cellular basis for the RSA at the level of the sinus node.

Vagal afferent activity increases dynamical dimension of respiration in rats.

Geometric and numerical techniques from nonlinear dynamics are employed to characterize the respiratory patterns of adult rats. In phase space constructions from volume measurements, the respiratory behavior of the vagotomized rat is seen to be unimodal and periodic, whereas that of the vagi-intact animal is bimodal and sensitive to initial conditions and displays stretching and folding of trajectories. By use of the correlation integral, the dimension and entropy were estimated for the respiratory patterns of five urethan-anesthetized rats (before and after vagotomy) and two awake animals (resting, vagi intact only).