Mean Respiratory Frequency Research Articles

High-frequency transcutaneous electrical nerve stimulation reduces pain and cardio-respiratory parameters in an animal model of acute pain: Participation of peripheral serotonin

The objective of this study was to investigate the effect of high-frequency transcutaneous electrical nerve stimulation (HF-TENS) in antihyperalgesia, assessed through changes of sciatic nerve activity and its effects on cardiorespiratory parameters, using formalin-induced nociception in anesthetized rats. The animals were divided into formalin (FORM) and HF-TENS groups. All rats received injections of 5% formalin (50 μl, right hind-paw). The sciatic nerve activity and cardiopulmonary parameters (mean arterial pressure, heart rate, and respiratory frequency) were measured, and then the serum levels of serotonin (5-HT) were determined by an enzyme-linked immunosorbent assay kit. The formalin injection was able to increase the sciatic nerve activity, heart rate, and respiratory frequency. The treatment with HF-TENS significantly reduced the sciatic nerve activity and respiratory frequency 20 minutes after formalin injection and was able to increase serum 5-HT. Furthermore, when comparing the groups, reductions in the mean arterial pressure, heart rate, respiratory frequency, and sciatic nerve activity were shown at different times. Thus, we concluded that HF-TENS was capable of inducing analgesia, which was most likely related to increased serotonin release. Moreover, we demonstrated that TENS was able to block the adverse cardiovascular and respiratory changes induced by pain. Further neurophysiological studies are necessary to clarify the intrinsic mechanisms underlying HF-TENS-induced analgesia.

Monitoring Breathing Rate at Home Allows Early Identification of COPD Exacerbations

Respiratory frequency increases during exacerbations of COPD (ECOPD). We hypothesized that this increase can be detected at home before ECOPD hospitalization. To test this hypothesis, respiratory frequency was monitored at home daily for 3 months in 89 patients with COPD (FEV₁, 42.3% ± 14.0%; reference) who were receiving domiciliary oxygen therapy (9.6 ± 4.0 h/d). During follow-up, 30 patients (33.7%) required hospitalization because of ECOPD. In 21 of them (70%), mean respiratory frequency increased (vs baseline) during the 5 days that preceded it (from 15.2 ± 4.3/min to 19.1 ± 5.9/min, P < .05). This was not the case in patients without ECOPD (16.1 ± 4.8/min vs 15.9 ± 4.9/min). Receiver operating characteristic analysis showed that 24 h before hospitalization, a mean increase of 4.4/min (30% from baseline) provided the best combination of sensitivity (66%) and specificity (93%) (area under the curve [AUC] = 0.79, P < .05). Two days before hospitalization, a mean increase of 2.3/min (15% change from baseline) was associated with a sensitivity of 72% and a specificity of 77% (AUC = 0.76, P < .05). Respiratory frequency can be monitored daily at home in patients with COPD receiving domiciliary oxygen therapy. In these patients, breathing rate increases significantly days before they require hospitalization because of ECOPD. This may offer a window of opportunity for early intervention.

Sertraline inhibits formalin-induced nociception and cardiovascular responses

The objective of the present study was to determine the antihyperalgesic effect of sertraline, measured indirectly by the changes of sciatic afferent nerve activity, and its effects on cardiorespiratory parameters, using the model of formalin-induced inflammatory nociception in anesthetized rats. Serum serotonin (5-HT) levels were measured in order to test their correlation with the analgesic effect. Male Wistar rats (250-300 g) were divided into 4 groups (N = 8 per group): sertraline-treated group (Sert + Saline (Sal) and Sert + Formalin (Form); 3 mg·kg−1·day−1, ip, for 7 days) and saline-treated group (Sal + Sal and Sal + Form). The rats were injected with 5% (50 µL) formalin or saline into the right hind paw. Sciatic nerve activity was recorded using a silver electrode connected to a NeuroLog apparatus, and cardiopulmonary parameters (mean arterial pressure, heart rate and respiratory frequency), assessed after arterial cannulation and tracheotomy, were monitored using a Data Acquisition System. Blood samples were collected from the animals and serum 5-HT levels were determined by ELISA. Formalin injection induced the following changes: sciatic afferent nerve activity (+50.8 ± 14.7%), mean arterial pressure (+1.4 ± 3 mmHg), heart rate (+13 ± 6.8 bpm), respiratory frequency (+4.6 ± 5 cpm) and serum 5-HT increased to 1162 ± 124.6 ng/mL. Treatment with sertraline significantly reduced all these parameters (respectively: +19.8 ± 6.9%, -3.3 ± 2 mmHg, -13.1 ± 10.8 bpm, -9.8 ± 5.7 cpm) and serum 5-HT level dropped to 634 ± 69 ng/mL (P < 0.05). These results suggest that sertraline plays an analgesic role in formalin-induced nociception probably through a serotonergic mechanism.

Cliaical observation of remifentanil and ketamine combined with sevoflurane applied in pediatric surgery

Objective To explore the clinical effect of remifentanil and ketamine with sevoflurane in pediatric surgery. Methods 80 cases of ASAⅠ～Ⅱ grade line surgery in children, were randomly divided into remifentanil group(A group) and the ketamine group(B group). Intramuscular midazolam 0.3mg/kg basic anesthesia catheter later. A group 2min before skin incision to give 0. 5μg/kg remifentanil infusion pump micro pump remifentanil 30μg(kg/h) add sevoflurane inhalation 3MAC until surgery. B group 2min before skin incision 2mg/kg ketamine infusion then pump ketamine 3mg(kg/h) add sevoflurane inhalation 3MAC until surgery; Record separately the two groups before skin incision in children with 2 min(T0) ,atskin incision(T1),after skin incision 15min(T2) ,when surgery (T3) in children with the mean arterial pressure (MAP),heart rate(HR),respiratory frequency(R)and oxygen saturation (SpO2) ,and record the total number of children with secretions (sputum volume) , awake time and the availability of laryngeal spasm,restlessness,nausea, vomiting and other adverse reactions. Results A group sputum volume was less than B group(P＜0.01) and A Group awake time was shorter than B Group(P＜0.01) ;Two groups of patients R infants had no inter-group differences(P＞0.05) ,two groups of children during quiet sleep,analgesic perfect, no significant respiratory depression,no laryngeal spasm,restlessness and nausea,vomiting and other adverse reactions. Conclusion Remifentanil composite Sevoflurane for surgery in children than ketamine was more stable during the cycle, secretions less quickly after waking up was a safe and reliable method of anesthesia. Key words: Remifentanil; Ketamine; sevoflurane; Children; Surgical procedures operative

Hypotensive Effects of the Crotalus Durissus Cascavella Venom: Involvement of NO

Crotalus durissus cascavella is a snake native of northeastern Brazil. The aim of the study was to investigate the effects of C. d. cascavella venom on rat mean arterial pressure and vascular reactivity in the mesenteric vascular bed. The venom evoked a dose-dependent decrease in mean arterial pressure, cardiac and respiratory frequency with increased plasma nitrite levels. L-NAME (10 mg/kg) blunted both the hypotension and increased nitrite production observed after the venom administration. To investigate the effects of C. d. cascavella in resistance vessels, the vascular mesenteric bed was studied, and the results suggested that the hypotensive effect of the venom is not dependent on a direct vasodilatory activity. In conclusion, C. d. cascavella venom presented indirect hypotensive effects with the involvement of nitric oxide.

Influence of time-varying mean heart rate in coronary artery disease diagnostic performance of heart rate variability indices from exercise stress testing

In this study, the influence of the time-varying mean heart rate (HR) and respiratory frequency in the ability of HR variability (HRV) indices to diagnose coronary artery disease has been studied. The autonomic nervous system activity has been assessed using a methodology that comprises correction of the HRV signal by the time-varying mean HR and redefinition of the classical high-frequency band to include respiratory frequencies above 0.4 Hz. The obtained clinical indices discriminate patients with coronary artery disease from patients with Framingham risk index lower than 5% with a moderate accuracy of 76%, which is lower than the reported in literature for HRV indices. We claim that time-varying mean HR and respiratory frequency, if not taken into account, introduce apparent improvement of diagnostic performance of HRV indices, adding information nonrelated to the autonomic nervous system activity, which is not what HRV is supposed to measure.

Inner ear insult suppresses the respiratory response to carbon dioxide

Compensated respiratory acidosis has been observed in a significant number of patients with active vestibular disease. We therefore hypothesized that the inner ear may play an unrecognized integral role in respiratory control. To test this premise, we investigated whether mice with induced inner ear injury demonstrated any alteration in their respiratory response to inhaled carbon dioxide (CO2). Experimental mice and control mice were included in two separate experiments. Intra-tympanic gentamycin injections were administered to induce inner ear damage in experimental animals. Hearing loss and vestibular dysfunction were tested 1-week after injections to confirm presence of inner ear insult, following which the animal's respiratory response to inhalation of 8% CO2 was examined. Mice with inner ear injury (n=60) displayed a significantly diminished hypercapnic ventilatory response (HCVR). This contrasted with the normal HCVR seen in control mice that had not undergone tympanic injections (n=30), controls that received tympanic injections with saline (n=5), and controls that had gentamicin administered systemically (n=5). In response to inspired CO2, the mean respiratory frequency of control mice increased by an average of 50% over their baseline values for both parts of the experiment. In contrast, the ear-damaged experimental group mean values increased by only three breaths per minute (bpm) (2%) in the first experiment and by 28 bpm (11%) in the second experiment. Inner ear damage significantly reduces the respiratory response to CO2 inhalation. In addition to the established role of the inner ear organ in hearing and balance, this alludes to an unidentified function of the inner ear and its interconnecting neuronal pathways in respiratory regulation. This finding may offer valuable new clues for disease states with abnormal respiratory control where inner ear dysfunction may be present.

Efeitos cardiorrespiratórios frente à posição do corpo em recém-nascidos pré-termo submetidos ao aumento do volume gástrico

The increase of the gastric volume observed in the gavage feeding is likely to cause consequences to the premature newborn, modifying the respiratory indicators. To investigate the alterations in the cardiorespiratory system of premature newborns submitted to an increase of the gastric volume by gavage feeding, according to four different body positioning methods. The study is a randomized crossover trial using a sample of 16 newborns with gestational age from 31 to 34 weeks and birth weight less or equal to 2.500 g. The newborns were included in the study if they had from 7 to 10 days of life, feeding by orogastric tube, total volume of 150 mL/kg/day and absence of supplemental oxygen-therapy. A different positioning method was used at each gavage (all raised to 30 degrees), or say, right lateral, left lateral, prone and supine positions. The following response variables were considered: respiratory and cardiac frequencies, saturation of oxygen, drawing of intercostals, beating of nasal wing and grunting. These measures were collected in intervals of 2 minutes during 5 minutes after the gavage feeding, during whole period of the gavage feeding, and during 5 minutes before the gavage feeding. The mean gestational age was 32 weeks (standard deviation 1.3) and the mean weight of the newborns was 1.722 g (standard deviation 276.3). The newborns presented higher values of the mean respiratory frequency in supine and left lateral body positions. In the right lateral and prone positions, the newborns presented lower mean cardiac frequency. The mean oxygen saturation had the lowest values in the left lateral and supine positions. The right lateral and prone positions presented low frequencies of intercostals drawing, beating of nasal wing and grunting. Our results indicate that right lateral and prone positions have influence on the cardiorespiratory effect, where left lateral and supine are the positions who presented higher negative effect in the newborns submitted to the increase of the gastric volume.

Análisis de 4 escalas de valoración de la sedación en el paciente crítico

Background This study aimed to verify the relationship between different Sedation Rating Scales (SRSs) for critical patients on mechanical ventilation and to know the relationship between the SRSs, clinical information and the dose of sedative and analgesia drugs (SAD). Material and methods A longitudinal, prospective analytic pilot study conducted in a Medical-Surgical Intensive Care Unit of a tertiary hospital from October-December 2006. The sample included patients who required administration of SAP and mechanical ventilation. The following biological parameters and scales were evaluated: patient's demographics, RAMSAY, Sedation Agitation Scale (SAS), Richmond Agitation Sedation Scale (RASS), Motor Activity Assessment Scale (MASS), SAD dose, mean blood pressure, cardiac rate, pupil diameter and respiratory frequency. Spearman coefficient of interrelation was used to compare the relationship between the different scales. Results A total of 2.412 measurements were made for each variable: SRS, clinical information and SAD dose in 30 patients with different diseases, 63 % males, age 52 ± 19 years, APACHEII 24 ± 8, SAPSII 44 ± 16, with an ICU mortality UCI 34 %. Median and IQ range of stay in ICU 15.5 and 20 days, of mechanical ventilation 9 and 14 days, of SAD 6 and 5.5 days and of paralyzing drugs (PD) 2 and 5 days, respectively. Interrelation was detected between all the SRSs, with p < 0.0001. The relationship between SAS, RASS and MASS was direct, whereas these were related inversely to RAMSAY. No evidence of interrelation was found between the SRSs, the clinical information and the SAD doses. Conclusion The RAMSAY scale that has not been validated in ICU patients has a strong interrelation with the other already validated SRSs. SRSs are subjective and do not correlate with the clinical information and the SAD doses, probably due to the sample's small size and heterogeneity.

Acute airway effects of ozone-initiated d-limonene chemistry: Importance of gaseous products

There are concerns about ozone-initiated chemistry, because the formation of gaseous oxidation products and ultrafine particles may increase complaints, morbidity and mortality. Here we address the question whether the gaseous products or the ultrafine particles from the ozone-initiated chemistry of limonene, a common and abundant indoor pollutant, cause acute airway effects. The effects on the airways by d-limonene, a ca. 16 s old ozone/ d-limonene mixture, and clean air were evaluated by a mice bioassay, from which sensory irritation of the upper airways, airflow limitation, and pulmonary irritation can be obtained. A denuder was inserted to separate the ultrafine particles from the gaseous products prior to the exposure chamber. Reduction of mean respiratory frequency (>30%) and 230% increase of time of brake were observed without denuder, during 30 min exposure, to the ozonolyzed d-limonene mixture, which are indicative of prominent sensory effects. The initial concentrations (ppm) were 40 d-limonene and 4 ozone. The exposure concentrations (ppm) were about 35 d-limonene and 0.05 ozone. Formaldehyde and residual d-limonene, the salient sensory irritants, accounted for up to three-fourth of the sensory irritation. The upper airway effects reversed to baseline upon cessation of exposure. An effect on the conducting airways was also significant, which did not reverse completely upon cessation. Airway effects were absent with the denuder inserted, which did not alter the size distribution of ultrafine particles (∼10 mg/m 3), significantly. The result was statistically indistinguishable from clean dry air. It is concluded that ultrafine particles that are generated from ozone-initiated d-limonene chemistry and denuded are not causative of sensory effects in the airways.

Involvement of nitric oxide (NO) in the nucleus tractus solitarii (NTS) on respiratory but not in cardiovascular responses to chemoreflex activation in awake rats

There is evidence that NO is a neuromodulator in the NTS. In the present study we evaluated the effect of nitric oxide synthase (NOS) inhibition in the caudal nucleus tractus solitarii (cNTS) on: a) the baseline cardiovascular and respiratory functions, and b) the changes on mean arterial pressure (MAP), heart rate (HR) and respiratory frequency (RF) in response to chemoreflex activation in awake rats. Rats received bilateral guide‐cannulas in the cNTS and the femoral artery and vein were cannulated. RF was evaluated by body‐plethysmography. Chemoreflex was activated with KCN (iv) before and after bilateral microinjections of a non‐selective NOS inhibitor L‐NAME (n=8) or a selective neuronal NOS inhibitor N‐Propyl (n=7) into cNTS. Microinjection of L‐NAME into cNTS produced a significant increase in baseline MAP (100 ± 2 vs 112 ± 3 mmHg) but no changes in HR and RF. Microinjection of N‐Propyl into cNTS did not affect baseline MAP, HR and RF. Microinjection of L‐NAME (138 ± 10 vs 81 ± 11 cpm) or N‐Propyl (159 ± 13 vs 90 ± 17 cpm) into cNTS significantly reduced the tachypneic but had no effect on the magnitude of cardiovascular responses to chemoreflex. The data shows that the activation of the respiratory component of the chemorreflex in the caudal NTS involves nNOS‐derived NO production, while NO does not modulate the cardiovascular responses. Supported by CNPq and FAPESP.

Backpack load positioning and walking surface slope effects on physiological responses in infantry soldiers

The primary purpose of this study was to survey a sample of infantry soldiers to determine their preferred backpack load distribution. The second objective was to examine the effect of backpack load position, walking speed and surface grade on the physiological responses of infantry soldiers. In the first phase of the study, analysis of 500 questionnaires indicated that backpack item arrangement was typically determined by convenience and habit. About 33.6% and 30.6% of the soldiers reported placing heavier items in the lower and higher positions, respectively. In the second experimental phase of the study, five male infantry soldiers who had completed basic training (including 30 km tactical road march) each performed eight treadmill walking bouts at one of two speeds (i.e., 3.2 and 6.4 km/h) and two surface grades (0% and 6%) carrying 15% of their body weight in a backpack with two chambers (upper and lower). Respiratory frequency, minute ventilation, oxygen consumption and heart rate were recorded using the Quark pulmonary system. The MANOVA results indicate that the effect of walking speed was strongly significant for all physiological indices. In addition, as might be expected, walking on a 6% grade was associated with higher oxygen consumption and heart rate compared to level going. In terms of load position, the mean respiratory frequency was significantly higher where the load was carried in the upper position. Furthermore, there was a significant interaction between load position and walking grade on oxygen consumption. Where participants were walking at zero incline, there was no significant difference in mean oxygen consumption. By contrast, the mean oxygen consumption was significantly higher where loads were carried in the upper position and negotiating the 6% grade. Previous research has found that, ideally, load carriage should complement stability, bringing the load's center of gravity as close to the body as possible and making use of the larger muscles. However, carrying heavy loads close to the trunk can affect lung function. Thus, load placement is an important factor in physiological response to load carriage, and optimum choice of upper or lower position when distributing items in a backpack may be dependent on the walking grade. Relevance to industry The need to carry heavy loads for long distances is common to a range of human endeavor, with physical transport used by soldiers, various types of workers and recreational hikers. Load distribution and walking gradient are important factors in terms of the efficiency of load carriage and should be taken into consideration in both the design and loading of backpacks. Thus, the findings of the present study will be relevant to infantry soldiers, mountain climbers or of manual material handling (MMH) in industry, providing practical implications for tasks associated with exposure to uneven walking/working surfaces.

Modulation of respiratory activity by locomotion in lampreys

In vertebrates, locomotion is associated with changes in respiratory activity, but the neural mechanisms by which this occurs remain unknown. We began examining this in lampreys using a semi-intact preparation of young adult Petromyzon marinus, in which respiratory and locomotor behaviors can be recorded simultaneously with the activity of the underlying neural control systems. Spontaneous fictive respiration was recorded with suction electrodes positioned over the glossopharyngeal or the rostral vagal motor nucleus. In this preparation, locomotor activity, characterized by symmetrical tail movements (electromyogram recordings), was evoked by mechanical stimulation of the skin. During locomotion, the mean respiratory frequency and the mean area of the motor bursts were significantly increased (81.6±28.6% and 62.8±25.4%, respectively; P<0.05). The frequency returned to normal 92±51 s after the end of locomotion. There were fluctuations in the instantaneous respiratory and locomotor frequencies that were rhythmical but antiphasic for the two rhythmic activities. The changes in respiratory activity were also examined during bouts of locomotion occurring spontaneously, and it was found that a modification in respiratory activity preceded the onset of spontaneous locomotion by 3.5±2.6 s. This suggests that the early respiratory changes are anticipatory and are not caused by feedback generated by locomotion. The increase in respiratory frequency during locomotion induced by sensory stimulation persisted after removal of the mesencephalon. When both the mesencephalon and spinal cord were removed, resulting in the isolation of the rhombencephalon, changes in the respiratory activity were also present following skin stimulations that would have normally induced locomotion. Altogether, the results suggest that respiratory changes are programmed to adjust ventilation prior to motor activity, and that a central rhombencephalic mechanism is involved.

Respiratory and autonomic responses to microinjection of NMDA and AMPA into the commissural subnucleus of the NTS of awake rats

The changes in mean arterial pressure (MAP) and respiratory frequency (RF) in response to microinjection of NMDA or AMPA into the commissural subnucleus of the NTS (comNTS) at the calamus scriptorius level of awake rats were evaluated. Under tribromoethanol anesthesia, the rats received guide-cannulae in direction of the NTS and a catheter was inserted into the femoral artery for measurement of arterial pressure. Changes in RF were evaluated with the rats inside a plethysmographic chamber. Randomly microinjections of 5 doses of NMDA (0.001, 0.01, 0.1, 1.0 and 2 nmol/50 nL; n = 10) or AMPA (1, 5, 10, 25 and 50 pmol/50 nL; n = 8) into the comNTS were performed at 15 min intervals and produced a dose-dependent increase in MAP [NMDA (3 ± 2, 4 ± 3, 25 ± 4, 41 ± 4 and 51 ± 4 mm Hg) and AMPA (0 ± 1, 14 ± 4, 17 ± 3, 27 ± 5 and 34 ± 3 mm Hg)]. Microinjection of NMDA (1 nmol/50 nL; n = 7) or AMPA (50 pmol/50 nL; n = 4) into the comNTS produced a long lasting apnea. The pressor responses to microinjection of NMDA or AMPA into the comNTS were blocked by prazosin, a α 1-adrenoceptor antagonist, indicating that the increase in arterial pressure in both cases was sympathetically mediated. The data show that microinjection of NMDA and AMPA into the comNTS produced pressor response and apnea, indicating that both ionotropic l-glutamate receptors may play a role in the neurotransmission/neuromodulation of the autonomic and respiratory components of the cardiovascular reflexes at this level.

Influence of acute unilateral vestibular lesions on the respiratory rhythm after active change of posture in human subjects

The influence of acute unilateral vestibular lesions on respiratory rhythm after active change of posture, was evaluated by comparing responses from patients with acute vestibular neuritis, with those from normal subjects with minor injuries other than vestibular (e.g. epistaxis, headache) and patients with chronic bilateral vestibular dysfunction. Respiratory movements of the thorax-abdomen were recorded during 5 minutes in supine position, 5 minutes of back-unsupported sitting and 5 minutes of upright stance. Compared to supine position, sitting-up induced different responses in each group (p < 0.05, ANOVA). The healthy subjects showed a consistent decrease in the mean respiratory frequency related to an increase of the expiration time, which was absent in patients with vestibular neuritis. Subjects with minor injuries showed the opposite changes of expiration time and inspiration time with no change of the respiratory frequency and patients with bilateral vestibular dysfunction showed a trend to increase their respiratory frequency. Standing-up did not evoke any further changes in any group. We conclude that the vestibular system modulates the respiratory response to reorientation of the head and trunk to upright position and this influence is reduced during the acute stage of a vestibular lesion.

Fog-induced Respiratory Responses Are Attenuated by Nedocromil Sodium in Humans

Fog inhalation induces cough and bronchoconstriction in patients with asthma, but only cough in normal subjects; whether it also influences the pattern of breathing is unclear. Nedocromil sodium (NCS) inhibits the cough response to inhalation of several pharmacological agents but its effects on fog-induced cough and changes in the pattern of breathing are unknown. We evaluated the effects of no drug, placebo, and 4- and 8-mg NCS administration on the cough threshold and changes in the pattern of breathing during fog inhalation in 14 healthy subjects. Measurements of tidal volume (VT), duration of inspiratory and expiratory times (TI and TE, respectively), total duration of the respiratory cycle (TT), mean inspiratory flow (VT/TI), duty cycle (TI/TT), respiratory frequency (f, 60/TT), and inspiratory minute ventilation (V I) were obtained by inductive plethysmography. Median cough threshold values were unaffected by placebo, but were increased (p < 0.01) by both NCS doses. In no-drug and placebo trials, inhalation of the threshold fog concentration caused increases in both VT/TI and V I (p always < 0.05) due to selective increases (p < 0.01) in VT. These changes were markedly attenuated by both NCS doses administration. Thus, fog induces coughing and increases in VT, VT/ TI, and V I in healthy subjects; NCS possesses antitussive effects and attenuates fog-induced changes in the pattern of breathing, possibly through inhibition of rapidly adapting "irritant" receptors.

Effect of the mechanical ventilatory cycle on thermodilution right ventricular volumes and cardiac output.

The purpose of this study was to evaluate right ventricular (RV) loading and cardiac output changes, by using the thermodilution technique, during the mechanical ventilatory cycle. Fifteen critically ill patients on mechanical ventilation, with 5 cmH(2)O of positive end-expiratory pressure, mean respiratory frequency of 18 breaths/min, and mean tidal volume of 708 ml, were studied with help of a rapid-response thermistor RV ejection fraction pulmonary artery catheter, allowing 5-ml room-temperature 5% isotonic dextrose thermodilution measurements of cardiac index (CI), stroke volume (SV) index, RV ejection fraction (RVEF), RV end-diastolic volume (RVEDV), and RV end-systolic volume (RVESV) indexes at 10% intervals of the mechanical ventilatory cycle. The ventilatory modulation of CI and RV volumes varied from patient to patient, and the interindividual variability was greater for the latter variables. Within patients also, RV volumes were modulated more by the ventilatory cycle than CI and SV index. Around a mean value of 3.95 +/- 1.18 l. min(-1). m(-2) (= 100%), CI varied from 87.3 +/- 5.2 (minimum) to 114.3 +/- 5.1% (maximum), and RVESV index varied between 61.5 +/- 17.8 and 149.3 +/- 34.1% of mean 55.1 +/- 17.9 ml/m(2) during the ventilatory cycle. The variations in the cycle exceeded the measurement error even though the latter was greater for RVEF and volumes than for CI and SV index. For mean values, there was an inspiratory decrease in RVEF and increase in RVESV, whereas a rise in RVEDV largely prevented a fall in SV index. We conclude that cyclic RV afterloading necessitates multiple thermodilution measurements equally spaced in the ventilatory cycle for reliable assessment of RV performance during mechanical ventilation of patients.

Effects of the serotonin synthesis inhibitor p-CPA on the expression of the crossed phrenic phenomenon 4 h following C2 spinal cord hemisection.

The present study assesses the effects of para-chlorophenylalanine (p-CPA), a serotonin-depleting drug, on the recovery of respiratory-related activity in the phrenic nerve induced by asphyxia 4 h following ipsilateral C2 hemisection in young adult rats. HPLC analysis was used to quantify levels of serotonin (5-HT), dopamine (DA), norepinephrine, and the 5-HT metabolite, 5-hydroxyindoleacetic acid, in the C4 segment of the spinal cord, all of which were significantly lower in p-CPA-treated hemisected rats compared to hemisected controls receiving saline. Hemisection alone was found to significantly increase 5-HT levels and significantly decrease DA levels compared to normal controls. Eight of eight saline-injected rats expressed recovery of respiratory-related activity in the ipsilateral phrenic nerve during asphyxia 4 h following hemisection, while only 4/8 rats in the p-CPA-treated group expressed recovery in the ipsilateral nerve. Quantification of integrated phrenic nerve wave-forms indicated that the mean amplitude of respiratory-related activity in the ipsilateral phrenic nerve was significantly lower in p-CPA-treated rats than in saline controls. In addition, saline controls demonstrated significant increases in mean respiratory frequency and mean amplitude of contralateral phrenic nerve activity during asphyxia, compared to normocapnia. However, p-CPA-treated rats did not express significant differences in either mean respiratory frequency or mean amplitude of integrated respiratory wave-forms during asphyxia, compared to normocapnia. The results suggest that p-CPA treatment attenuates the recovery of respiratory-related activity in the phrenic nerve 4 h following ipsilateral C2 hemisection and attenuates asphyxia-induced increases in respiratory frequency and respiratory burst amplitude recorded from the contralateral phrenic nerve.

How Effective Are Supplementary Doses of Opioids for Dyspnea in Terminally Ill Cancer Patients? A Randomized Continuous Sequential Clinical Trial

Supplementary doses of opioids are recommended to relieve dyspnea in terminally ill cancer patients. We conducted a randomized continuous sequential clinical trial to evaluate their efficacy. We recruited 33 terminally ill cancer patients from three palliative care centers, all of whom had persistent dyspnea after rest and treatment with oxygen. Patients formed 15 successive pairs matched on route of administration. Within each pair, the order of allocation was randomly assigned, one patient receiving 25%, the other 50% of his 4-hourly opioid dose. Five measurements of dyspnea intensity and respiratory frequency were made during 4 hours of follow-up. For each pair, a preference was attributed to the more effective regimen. The two regimens received an almost equal number of paired preferences (8 vs. 7). Overall, both mean dyspnea intensity and respiratory frequency decreased significantly relative to baseline. Dyspnea reduction was relatively greater in patients with initially low and moderate dyspnea intensity. In terminally ill cancer patients with persistent dyspnea, 25% of the equivalent 4-hourly dose of opioid may be sufficient to reduce both dyspnea intensity and tachypnea for 4 hours.

Energy Metabolism of Thoracic Surgical Patients in the Early Postoperative Period: Effect of Posture

To determine the effect of elective thoracic surgery on energy metabolism and gas exchange and to evaluate whether the 30-degree sitting position would affect these variables. Prospective, unblinded, controlled study. Surgical ICU in a university hospital. Twenty-two adult patients undergoing elective pulmonary resection. Posture change from supine to 30-degree sitting position. Oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory quotient (RQ), and energy expenditure (EE) were measured by means of computerized indirect calorimetry before and after surgery. Heart rate and respiratory frequency were measured continuously during gas exchange measurement. Blood gases were analyzed with an automated blood gas analyzer. Preoperatively, altering position did not affect energy metabolism, gas exchange, and cardiopulmonary variables. Postoperatively, the measured EE was 116% of the expected value. Mean EE and VO2 values for each position were higher than the preoperative values for the corresponding postures (p<0.05 for each position), while VCO2 increased only in the supine position (p<0.05). Mean percent increases in EE, VO2, and VCO2 were significantly lower in the 30-degree sitting position than in the supine position (EE: 7.9+/-2.7% vs 14.4+/-2.3%; p<0.001; VO2: 9.0+/-3.0% vs 16.4+/- 2.6%; p<0.001; VCO2: 3.2+/-2.1% vs 6.5+/-1.4%: p<0.05). Arterial oxygen tension and all the physiologic indexes of gas exchange for each position were worse than the preoperative values for the corresponding postures (p<0.05 for each position). Mean arterial pressure, heart rate, and respiratory frequency for each position were higher than the preoperative values for the corresponding postures (p<0.05 for each position). No changes in mean values of these variables occurred between the two positions postoperatively. The early postoperative period of patients undergoing elective thoracic surgery is characterized by a condition of impaired gas exchange and by a hypermetabolic state. Hypermetabolism can be partly mitigated by assuming the 30-degree sitting position.