Depth Of Respiration Research Articles

Relationship between respiration, end-tidal CO2, and BOLD signals in resting-state fMRI

A significant component of BOLD fMRI physiological noise is caused by variations in the depth and rate of respiration. It has previously been demonstrated that a breath-to-breath metric of respiratory variation (respiratory volume per time; RVT), computed from pneumatic belt measurements of chest expansion, has a strong linear relationship with resting-state BOLD signals across the brain. RVT is believed to capture breathing-induced changes in arterial CO2, which is a cerebral vasodilator; indeed, separate studies have found that spontaneous fluctuations in end-tidal CO2 (PETCO2) are correlated with BOLD signal time series. The present study quantifies the degree to which RVT and PETCO2 measurements relate to one another and explain common aspects of the resting-state BOLD signal. It is found that RVT (particularly when convolved with a particular impulse response, the “respiration response function”) is highly correlated with PETCO2, and that both explain remarkably similar spatial and temporal BOLD signal variance across the brain. In addition, end-tidal O2 is shown to be largely redundant with PETCO2. Finally, the latency at which PETCO2 and respiration belt measures are correlated with the time series of individual voxels is found to vary across the brain and may reveal properties of intrinsic vascular response delays.

SU‐GG‐J‐197: Video‐Coaching as Biofeedback‐Tool to Improve Gated Treatments: 2 Years Clinical Experience

Purpose: Gated treatments using the Varian RPM—gating™ System include in a standard configuration a coaching tool based on voice commands (“breathe‐in”/“breathe‐out”) called audio‐coaching. As this configuration does not include feedback information like amplitude and breathing period, there are limitations concerning respiration depth and breathing pattern. The aim of this study was to evaluate the impact of video‐coaching as biofeedback to achieve more regular breathing and — as a consequence — quality improvements of the 4D‐CT scans as well as duty cycle enhancements. Method and Materials: Varian RPM‐gating system is used for acquisition of the CT‐Scan (4D‐CT) as well as the treatments; for the latter it manages the controlled switching of the radiation beam during a pre‐selected specific phase of the respiratory cycle. 80 patients with gated treatments have been analyzed, whereas 40 were only audio‐coached and 40 audio‐coached with video‐feedback. We evaluated periodicity and amplitude changes as well as compliance with regard to the theoretically calculated duty cycle and determined the dependency of the parameters on the coaching type. Results: For the CT acquisitions several changes has been observed, i.e. fluctuations of the inspiration maxima are significantly smaller (p=0.005) and the breathing curves are smoother. The compliance during the treatment course was significantly increased: almost all video‐coached patients reached in average their theoretical duty cycle, whereas 60% of the patients with audio‐coaching only had more than 25% longer treatment times due to inappropriate amplitudes (p=0.001). Conclusion: Video‐coaching is suitable to significantly improve the quality of 4D scans and allows optimizing the treatment time due to better compliance. We also implemented this feedback technology combined with voluntary end‐inspiration breath hold technique thus allowing the patient to control the treatment themselves in a direct way. These results indicate that this approach could suit the individual patient need in a better way.

Injection of Mesobuthus tamulus venom in distal segment of femoral artery evokes hyperventilatory and hypertensive responses in anaesthetised rats

Intra-arterial (i.a.) injection of Indian red scorpion (Mesobuthus tamulus; BT) venom produces cardiorespiratory changes by involving perivascular receptors. The afferents involved in mediating these reflex responses are not known. The present investigation was conducted to examine the afferents mediating the vasosensory reflexes evoked by i.a. injection of BT venom in the peripheral end of femoral artery in urethane anaesthetised rats. Blood pressure (BP), ECG (for heart rate), and respiratory movements (for rate and depth) were recorded for 30min after the i.a. injection of venom. Minute ventilation (MV) was computed by using appropriate calibrations for depth and rate of respiration. After the injection of venom, there was immediate hyperventilatory, intermediate hypertensive and delayed bradycardiac response. Equal volume of saline (0.10ml, i.a.) did not produce any cardiorespiratory changes thus, eliminating the possibility of stretch mediated responses. Sectioning of ipsilateral sciatic and femoral nerves attenuated the hyperventilatory and hypertensive responses produced by venom significantly. After the neurotomy, the latency of bradycardiac response was shortened significantly. Even the time to reach the peak bradycardiac response was also shortened. The data provide evidences for the partial involvement of somatic nerves in mediating the vascular reflexes.

Prediction of Mortality Using Measures of Cardiac Autonomic Dysfunction in the Diabetic and Nondiabetic Population

To evaluate whether reduced heart rate variability (HRV), prolonged corrected QT (QTc) interval, or increased QT dispersion (QTD) are predictors of mortality in the general diabetic and nondiabetic population. Nondiabetic (n = 1,560) and diabetic (n = 160) subjects aged 55-74 years were assessed to determine whether reduced HRV, prolonged QTc interval, and increased QTD may predict all-cause mortality. Lowest quartiles for the maximum-minimum R-R interval difference (max-min, as measured at baseline from a 20-s standard 12-lead resting electrocardiogram without controlling for depth and rate of respiration), QTc >440 ms and QTD >60 ms, were used as cutpoints. During a 9-year follow-up, 10.5% of the nondiabetic and 30.6% of the diabetic population deceased. In the nondiabetic individuals, multivariate Cox proportional hazard models adjusted for cardiovascular risk factors and demographic variables showed that prolonged QTc interval (hazard ratio 2.02 [95% CI 1.29-3.17]; P = 0.002) but not low max-min (0.93 [0.65-1.34]; P = 0.700), and increased QTD (0.98 [0.60-1.60]; P = 0.939) were associated with increased mortality. In the diabetic subjects, prolonged QTc was also a predictor of mortality (3.00 [1.34-6.71]; P = 0.007), while a trend for an increased risk was noted in those with low max-min (1.74 [0.95-3.18]; P = 0.075), whereas increased QTD did not predict mortality (0.42 [0.06-3.16]; P = 0.402). Prolonged QTc interval, but not increased QTD, is an independent predictor of a twofold and threefold increased risk of mortality in the nondiabetic and diabetic elderly general population, respectively. Low HRV during spontaneous breathing tends to be associated with excess mortality in the diabetic but not nondiabetic population.

The respiration response function: The temporal dynamics of fMRI signal fluctuations related to changes in respiration

Changes in the subject’s breathing rate or depth, such as a breath-hold challenge, can cause significant MRI signal changes. However, the response function that best models breath-holding-induced signal changes, as well as those resulting from a wider range of breathing variations including those occurring during rest, has not yet been determined. Respiration related signal changes appear to be slower than neuronally induced BOLD signal changes and are not modeled accurately using the typical hemodynamic response functions used in fMRI. In this study, we derive a new response function to model the average MRI signal changes induced by variations in the respiration volume (breath-to-breath changes in the respiration depth and rate). This was done by averaging the response to a series of single deep breaths performed once every 40 s amongst otherwise constant breathing. The new “respiration response function” consists of an early overshoot followed by a later undershoot (peaking at approximately 16 s), and accurately models the MRI signal changes resulting from breath-holding as well as cued depth and rate changes.

Video-Coaching as Biofeedback-tool to Improve Gated Treatments: 2 Years Clinical Experience

Gated treatments using the Varian RPM-gating TM System include in a standard configuration a coaching tool based on voice commands (“breathe-in”/”breathe-out”) called audio-coaching. As this configuration does not include feedback information like amplitude and breathing period, there are limitations concerning respiration depth and breathing pattern. The aim of this study was to evaluate the impact of video-coaching as biofeedback to achieve more regular breathing and–as a consequence–quality improvements of the 4D CT scans as well as duty cycle reductions.

Observing the sick child: Part 2b Respiratory palpation

Assessment is a major nursing role, and expanding assessment techniques, traditionally seen as the remit of the medical profession, can assist nursing assessment and the provision of appropriate care. This is the third article in a series of five articles. Parts 1 and 2a provided a practical critical review of the validity and reliability of basic respiratory assessment focusing on measurement of respiratory rate, rhythm and depth. This article provides a practical step-by-step introduction to the theory and practice of advanced respiratory assessment using palpation. Next month we will build on these skills and provide a practical step-by-step introduction to using auscultation in order to augment basic respiratory assessment skills.

Observing the sick child: Part 2a Respiratory assessment

As the focus on evidence-based healthcare delivery gains momentum, nurses need to critically reflect on their traditional practice base. Assessment is the cornerstone of safe and effective practice and goes hand in hand with the process of prioritising a sick child's needs. This article begins with a practical and critical review of the validity and reliability of basic respiratory assessment focused on measurement of respiratory rate, rhythm and depth. Part 2b in February 2007 will be a practical step-by-step introduction to the theory and practice of advanced respiratory assessment using palpation. Part 2c in the following month will focus on respiratory auscultation methods.

The Donders Model of the Circulation in Normo- and Pathophysiology

The solution of some recent as well as of long standing problems, unanswerable due to experimental inaccessibility or moral objections are addressed. In this report, a model of the closed human cardiovascular loop is developed. This model, using one set of 88 equations, allows variations from normal resting conditions to exercise, as well as to the ultimate condition of a circulation following cardiac arrest. The principal purpose of the model is to evaluate the continuum of physiological conditions to cardiopulmonary resuscitation (CPR) effects within the circulation.Within the model, Harvey's view of the circulation has been broadened to include impedance-defined flow as a unifying concept, and as a mechanism in CPR. The model shows that depth of respiration, sympathetic stimulation of cardiac contractile properties and baroreceptor activity can exert powerful influences on the increase in cardiac output, while heart and respiratory rate increases tend to exert an inhibiting influence, with the pressure and flow curves compatible with accepted references. Impedance-defined flow encompasses both positive and negative effects.The model also demonstrates the limitations to cardiopulmonary resuscitation caused by external force applied to intrathoracic structures, with effective cardiac output being limited by collapse and sloshing. Stroke volumes from 6 to 51 ml are demonstrated. It shows that the clinical inclination to apply high pressures to intrathoracic structures may not be rewarded with improved net flow.

SU‐FF‐T‐454: Video‐Coaching as a Biofeedback Tool to Improve Gated Treatments

Purpose: Gated treatments using the Varian RPM—gating™ System include in a standard configuration a coaching tool based on voice commands (“breathe‐in”/“breathe‐out”) called audio‐coaching. As this configuration does not include feedback information like amplitude and breathing period, there are limitations concerning respiration depth and breathing pattern. The aim of this study was to evaluate the impact of video‐coaching as biofeedback to improve gated treatments of breast cancer. Method and Materials: Varian RPM‐gating system is used for acquisition of the CT‐Scan (4D‐CT) as well as the treatments; for the latter it manages the controlled switching of the radiation beam during a pre‐selected specific phase of the respiratory cycle. 100 patients with gated treatments have been analyzed, whereas 50 were only audio‐coached and 50 audio‐coached with video‐feedback. We evaluated periodicity and amplitude changes as well as compliance with regard to the theoretically calculated duty cycle and determined the dependency of the parameters on the coaching type. Results: For the CT acquisition several changes has been observed, i.e. amplitude fluctuations are significantly smaller (p=0.005) and the breathing curves are smoother. This leads to an increased compliance during the treatment course: almost all video‐coached patients reached in average their theoretical duty cycle, whereas 60% of the patients with audio‐coaching only had more than 25% longer treatment times due to inappropriate amplitudes. Periodicity is not dependent on the kind of coaching (p=0.01). Conclusion: Video‐coaching is suitable to significantly improve the quality of 4D scans and allows optimizing the treatment time due to better compliance. In a next step we are currently implementing this feedback technology combined with deep inspiration breath hold technique thus allowing the patient to control the treatment themselves in a direct way. Preliminary results indicate that this approach could suit the individual patient need in a better way.

Risperidone Withdrawal-Related Respiratory Dyskinesia

Risperidone is a frequently used member of a new class of atypical antipsychotics-the serotonin-dopamine antagonists (SDAs)-due to its comparatively high efficacy and low D2/5HT2 binding ratio, which results in a low incidence of extrapyramidal side effects including tardive dyskinesia (TD). The authors present an elderly patient with mixed dementia who developed TD at multiple sites, (including respiratory dyskinesia [RD], limb dyskinesia, and orofacial dyskinesia) following abrupt withdrawal of risperidone therapy. RD is not a rare condition, but is often misdiagnosed and is potentially lethal. Therefore, clinicians should pay close attention to possible onset of RD in patients with multiple risk factors for TD, even when SDA therapy is used. If RD is suspected, assessment should include spirography combined with fibroscopy for examination of irregularities in the rate, rhythm, and depth of respiration.

D1-dopamine receptor agonists prevent and reverse opiate depression of breathing but not antinociception in the cat

Opioids depress respiration and decrease chest wall compliance. A previous study in this laboratory showed that dopamine-D(1) receptor (D(1)R) agonists restored phrenic nerve activity after arrest by fentanyl in immobilized, mechanically ventilated cats. The reinstated phrenic nerve rhythm was slower than control, so it was not known whether D(1)R agonists can restore spontaneous breathing to levels that provide favorable alveolar gas exchange and blood oxygenation. It was also not known whether the agonists counteract opioid analgesia. In the present study, anesthetized, spontaneously breathing cats were given intravenous doses of fentanyl (18.0 +/- 3.4 microg/kg) that severely depressed depth and rate of respiration, lowered arterial hemoglobin oxygenation (HbO(2)), elevated end-tidal carbon dioxide (ETCO(2)), and abolished the nociceptive hind limb crossed-extensor reflex. Fentanyl (30 microg/kg) also evoked tonic discharges of caudal medullary expiratory neurons in paralyzed mechanically ventilated cats, which might explain decreased chest compliance. The selective D(1)R agonists 6-chloro APB (3 mg/kg) or dihydrexidine (DHD, 1 mg/kg) increased depth and rate of spontaneous breathing after opioid depression and returned HbO(2) and ETCO(2) to control levels. Opioid arrest of the nociceptive reflex remained intact. Pretreatment with DHD prevented significant depression of spontaneous breathing by fentanyl (17.5 +/- 4.3 microg/kg). Tonic firing evoked by fentanyl in expiratory neurons was converted to rhythmic respiratory discharges by DHD (1 mg/kg). The results suggest that D(1)R agonists might be therapeutically useful for the treatment of opioid disturbances of breathing without impeding analgesia.

Effects of doxapram HCl on laryngeal function of normal dogs and dogs with naturally occurring laryngeal paralysis

ObjectivesTo compare the effects of IV doxapram on glottic size and arytenoid motion in normal dogs and in dogs with laryngeal paralysis. Study designProspective experimental and clinical trials. AnimalsSix healthy dogs weighing 24.5 ± 3.9 kg and six dogs weighing 27.4 ± 11.5 kg suspected of having laryngeal paralysis. MethodsDogs were pre-medicated with acepromazine and butorphanol, and a light plane of anesthesia was induced with isoflurane by mask. Videoendoscopic examination of laryngeal function was recorded before (baseline) and after IV doxapram administration. Normalized glottal gap area (NGGA) at maximal inspiration and expiration, and percentage change in height, width, area, and NGGA were calculated with measurements from digitized images of the glottal gap. ResultsActive arytenoid motion was present in all normal dogs at baseline. After doxapram administration, depth of respiration appeared greater, but arytenoid motion, as measured by percentage change in NGGA, and in area and width, did not significantly increase in normal dogs. No arytenoid motion was detected in dogs with laryngeal paralysis at baseline; however, rima glottidis NGGA of dogs with laryngeal paralysis was greater at inspiration and expiration than normal dogs. After doxapram administration, dogs with laryngeal paralysis developed paradoxical arytenoid motion and significant, negative percentage change in area (−61%) and NGGA (−145%) because of inward collapse of the arytenoids during inspiration. Conclusions and clinical relevanceAdministration of doxapram during laryngeal examination is useful for differentiating normal dogs from dogs with laryngeal paralysis. Dogs with laryngeal paralysis may suffer extreme glottic constriction with vigorous respirations, and may require intubation during examination.

Respiration patterns in the deep ocean

The biological pump affects atmospheric CO2 levels and fuels most heterotrophic activity in the deep ocean. The efficiency of this pump depends on the rate of carbon fixation, export out of the euphotic zone and the depth of respiration. Here we study the depth dependence of respiration patterns, hence particulate carbon flux, using a compiled data set of sediment oxygen consumption rates. We show that the depth relationship can best be described by a double exponential model. For the upper part of the ocean, our resulting equation is similar to previous flux‐depth relationships but predicted fluxes are significantly larger in deeper waters. This implies a more efficient biological pump. Total oceanic respiration below the shelf break (200 m) is estimated to be 827 Tmol O2 yr−1.

Respiration and vertical carbon flux in the Gulf of Maine water column

The transport of carbon from ocean surface waters to the deep sea is a critical factor in calculations of planetary carbon cycling and climate change. This vertical carbon e ux can be calculated by integrating the vertical proe le of the seawater respiration rate but is rarely done because measuring seawater respiration is so dife cult. However, seawater respiratory oxygen consumption is the product of the combined activity of all the respiratory electron transfer systems in a seawater community of bacterioplankton, phytoplankton, and zooplankton. This respiratory electron transfer system (ETS) is the membrane bound enzymatic system that controls oxygen consumption and ATP production in all eukaryots and in almost all bacteria and archaea. As such, it represents potential respiratory oxygen consumption. Exploiting this, we measured plankton-community ETS activity in water column proe les in the Gulf of Maine to give the potential-respiration of the water column. To interpret these potentials in terms of actual seawater respiration we made use of previous measurements of respiratory oxygen consumption and ETS activity in the Gulf of Maine to calculate a ratio of respiratory potential to actual respiration. Armed with this ratio we calculated seawater respiration depth proe les from the ETS activity measurements. These proe les were characterized by: (1) high oxygen consumption rates in the euphotic zone; (2) subsurface maxima near the subsurface chlorophyll maxima (SCM); (3) rapid declines associated with thermoclines; (4) low declining rates below 50 m; (5) and elevated values occasionally near the bottom. Sea surface values ranged from 229 to 489 pmol O 2 min 2 1

Clinical profile and outcome of acute respiratory failure.

To examine the etiological factors, clinical features, treatment modalities and outcome of acute respiratory failure in children. This hospital-based prospective observational study was conducted over 15 months. Fifty children with acute respiratory failure, diagnosed by serial arterial blood gas analysis, were consecutively enrolled. Ventilation therapy was initiated when the FiO2 requirement went above 0.6. Pulmonary diseases accounted for majority (68%) of cases, followed by nervous system (12%); and cardiovascular and skeletal muscle system diseases (10%, each). Bronchopneumonia was the commonest cause of acute respiratory failure (11 cases). The majority of cases were in the age group 1 month to < 1 year (26 cases). The commonest signs were altered depth and pattern of respiration (100%), chest wall retractions (88%), flaring of alae nasae (88%), tachypnea (84%), tachycardia (82%), and irritability (64%). Cyanosis was noticed in only 26 (52%) cases. Thirty-six (72%) children required ventilation therapy. The overall mortality was 58%. The mortality was high (55.9% to 66.7%), irrespective of the primary system involved. Significantly higher mortality was associated with co-existent malnutrition (p<0.001), Type I failure (p=0.039) and ventilation therapy (p<0.0001). Acute respiratory failure has varied etiology and clinical manifestations, and a high mortality. Its outcome is independent of age of the child and the primary system involved. Malnutrition and Type I failure are factors associated with a poor outcome.

Contribution of tonic vagal modulation of heart rate, central respiratory drive, respiratory depth, and respiratory frequency to respiratory sinus arrhythmia during mental stress and physical exercise

This study tested various sources of changes in respiratory sinus arrhythmia (RSA). Twenty-two healthy participants participated in three experimental conditions (mental stress, relaxation, and mild physical exercise) that each consisted of three breathing parts (normal breathing, breathing compressed room air, and breathing compressed 5% CO2-enriched air). Independent contributions to changes in RSA were found for changes in tonic vagal modulation of heart rate, central respiratory drive (i.e., PaCO2), respiratory depth, and respiratory frequency. The relative contributions to changes in RSA differed for mental stress and physical exercise. It is concluded that uncorrected RSA will suffice to index within-subject changes in tonic vagal modulation of heart rate in most situations. However, if the central respiratory drive is expected to change, RSA should ideally be corrected for changes in PaCO2, respiratory depth, and respiratory frequency.

Contribution of tonic vagal modulation of heart rate, central respiratory drive, respiratory depth, and respiratory frequency to respiratory sinus arrhythmia during mental stress and physical exercise

This study tested various sources of changes in respiratory sinus arrhythmia (RSA). Twenty‐two healthy participants participated in three experimental conditions (mental stress, relaxation, and mild physical exercise) that each consisted of three breathing parts (normal breathing, breathing compressed room air, and breathing compressed 5% CO2‐enriched air). Independent contributions to changes in RSA were found for changes in tonic vagal modulation of heart rate, central respiratory drive (i.e., PaCO2), respiratory depth, and respiratory frequency. The relative contributions to changes in RSA differed for mental stress and physical exercise. It is concluded that uncorrected RSA will suffice to index within‐subject changes in tonic vagal modulation of heart rate in most situations. However, if the central respiratory drive is expected to change, RSA should ideally be corrected for changes in PaCO2, respiratory depth, and respiratory frequency.

Toxic effect of single treatment with bromantane on neurological status of experimental animals.

Neurotoxicological profile of actoprotector bromantane was studied on rats using S. Irwin's protocol of multi-test observation. The drug in doses of 30-300 mg/kg stimulated and in doses of 600-9,600 mg/kg suppressed behavioral activity. Spontaneous motor activity increased after single treatment with bromantane in doses of 30-300 mg/kg, did not change after treatment in doses of 600 mg/kg, and was inhibited after treatment in doses above 600 mg/kg. In doses of 300-600 mg/kg the drug reduced pain sensitivity threshold and in doses above 600 mg/kg elevated the pain threshold and tactile sensitivity and reaction to knock. Bromantane induced mydriasis in all studied doses; in doses above 10 g/kg the preparation induced blepharoptosis. In doses above 5 g/kg bromantane slightly increased respiration rate and depth (Kussmaul-like respiration). In some animals bromantane in high doses induced regurgitation, diarrhea, and polyuria. Rectal temperature decreased by 0.5-1 degrees C after virtually all doses. Behavioral effects of bromantane in doses of 30 and 600 mg/kg were associated with stimulation of the central dopamine and suppression of muscarinic and nicotinic cholinergic structures, n-cholinolytic effects of bromantane was more pronounced at a dose of 30 mg/kg than at a dose of 600 mg/kg.

Effect of adenosine on cerebral blood flow velocity.

Evidence suggests that adenosine (ADN) is a potent vasodilator of cerebral vessels. However, the feasibility of manipulating human cerebral vascular resistance with ADN has not been assessed by means of TCD. The purpose of this study was to quantitatively estimate the change in middle cerebral artery cerebral blood flow velocity (CBFV) in response to intravenous ADN infusion in humans. Eleven patients with subacute cerebrovascular events (ischemic stroke, transient ischemic attack, or hemorrhage) undergoing adenosine-thallium stress testing were studied before, during, and after ADN infusion to evaluate the effect of ADN on cerebral blood flow velocity. Continuous blood pressure (BP), heart rate (HR), respiration rate (RR), end-tidal CO2 (ET-CO2), and transcranial Doppler ultrasonography monitoring of CBFV and pulsatility index (PI) in both middle cerebral arteries were performed. The mean CBFVs were 65.4 +/- 19.2 cm/s before, 55.4 +/- 18.1 cm/s during, and 64.1 +/- 22.5 cm/s after ADN infusion, which represents a statistically significant decrease during ADN test compared with both baseline (P = .007) and posttest levels (P = .017). The PI was increased during the test (0.91 +/- 0.2) when compared with baseline (0.71 +/- 0.1) (P = .007). During ADN injection, mean HR increased (P = .004) and mean ET-CO2 levels decreased significantly (P = .003). Mean BP and RR did not change significantly. The authors hypothesize that any direct vasodilatory effect of ADN on the distal cerebral peripheral vasculature may be negated by an effect of ADN on depth of respiration resulting in hypocapnia and secondary distal vasoconstriction.