Respiratory Mode Research Articles

Effects of reduced mouth opening capacity (trismus) on pulmonary function

In this study, pulmonary function test data were obtained from 15 healthy volunteers and 15 patients with slightly impaired ventilation during both normal and maximally reduced opening of the mouth (trismus, intercuspal position). The aim of the study was to examine the effects of complete trismus on pulmonary function using objective and subjective parameters. In maximally reduced mouth opening, both groups showed an impairment of all subjective and objective pulmonary function test data. In healthy volunteers, the significant changes in test data (P<0.05) stimulated mild to moderate pulmonary impairment, whereas patients with an already impaired pulmonary function showed a marked deterioration of their initial respiratory condition. The results of the subjective and objective parameters examined indicate that an intercuspal position (trismus) further aggravates pulmonary functional impairment. Complete trismus can be considered a risk factor to pulmonary function in patients using mouth breathing as a primary or supportive mode of respiration.

Expression and longevity of toluene dioxygenase in Pseudomonas putida F1 induced at different dissolved oxygen concentrations

Toluene dioxygenase (TDO) in Pseudomonas putida F1 (PpF1) was used as a model to determine if enzymes that initiate aerobic BTEX degradation can be expressed at very low dissolved oxygen (DO) concentrations. Emphasis was placed on characterizing how the DO concentration during induction affects the level of enzyme expression. TDO was expressed at similar levels in PpF1 cells induced on toluene at different DO concentrations (ca. 1, 4, and 8 mg L −1). TDO activity decayed exponentially with cell age at 0.25–0.48 day −1. Nevertheless, the DO concentration during induction did not significantly affect TDO expression or longevity. PpF1 also grew on toluene at 0.1 mg L −1 DO, showing that TDO can be expressed at very low DO levels. This suggests that aerobic biotransformations are likely to contribute to BTX bioremediation even when an aerotolerant anaerobic respiration mode (e.g., denitrification) is prevalent.

Mechatronics in medical engineering: advanced control of a ventilation device

A typical mechatronics system consists of a mechanical process, electromechanical actuators, electronic sensors and a controller unit with the corresponding software. In this paper a microcontroller-based digital feedback control of a positioning device for a ventilation machine is presented. This kind of machine should allow either a volume- or a pressure-based controlled ventilation. The interdependence between the two important physiological variables, respiration volume and lung pressure, is highlighted and the requirements on the control system are discussed. Based on a mathematical model for the respiration device and the characteristics of the patient's lung a feedback control concept for both respiration modes has been developed and is presented in this paper. By means of simulations the control concept has been tested. To sum up some simulation and experimental results are shown.

Anoxic cardiac performance in Amazonian and north-temperate-zone teleosts

Amazonian fish face periodic conditions of hypoxic water not commonly encountered by most other species. We examined the impact of simulated anoxia on cardiac performance of Amazonian species relative to north-temperate-zone species to assess whether the ability to maintain anoxic heart performance is related to either respiratory strategy or geographic location. Four Amazonian species (acará-açu (Astronotus ocellatus), acari-bodó (Lipossarcus pardalis), tambaqui (Colossoma macropomum), and tamoatá (Hoplosternum littorale)) and four north-temperate-zone species (American eel (Anguilla rostrata), bullhead (Ictalurus punctatus), yellow perch (Perca flavescens), and rainbow trout (Oncorhynchus mykiss)) were studied. The Amazonian species display a range of respiratory modes from obligate gill-breather to facultative air-breather. The performance of isolated ventricular strips under conditions of impaired oxidative phosphorylation was monitored under the same conditions of temperature (25°C) and contraction frequency (30 bpm) for all species. In all cases, ventricular strips showed a decrease in the force of contraction with sodium cyanide (NaCN) treatment. Ventricular strips from two Amazonian and one north-temperate-zone species showed signs of recovery from NaCN treatment. There was considerable diversity in the ability of ventricular strips to develop force under conditions of impaired oxidative phosphorylation that was not related to the ability to obtain oxygen from the air or to geographic location. However, there was a major difference between Amazonian and north-temperate-zone species in the ability of ventricular strips to maintain resting tension under NaCN treatment. Resting tension increased under conditions of simulated anoxia in ventricular strips from all north-temperate-zone species, but there was no change in resting tension in ventricular strips from Amazonian species. We propose that hearts from the Amazonian species are better able to reduce cytoplasmic calcium levels, possibly through a more highly developed sarcoplasmic reticulum.

Carbon dioxide exchange via the mucosa in healthy middle ear.

Recent studies have shown that gas exchange via the middle ear mucosa, which is performed between the middle ear cleft and capillaries in the submucosal connective tissue, has an essential role in ventilation and pressure regulation in the middle ear cleft. We speculated that gas exchange via the mucosa is induced by the gas diffusion caused by the partial pressure gradient of gas between the middle ear cleft and submucosal capillaries. To evaluate the capacity of the gas exchange via the mucosa in the healthy middle ear of humans by examining the effect of the respiratory mode on middle ear pressure. We selected 13 volunteers ranging in age from 25 to 44 years with healthy ear drums and type A tympanograms. Middle ear pressure was measured in 1 ear of each subject every 2 minutes using tympanometry while the respiratory mode was altered, with the subject in the supine position. The partial pressure of carbon dioxide in the venous blood (PvCO2) and middle ear pressure were decreased by hyperventilation and increased by hypoventilation. The partial pressure of oxygen in the venous blood showed little change. Carbon dioxide diffused into the blood from the middle ear cleft in accord with the partial pressure gradient when the PvCO2 was reduced by hyperventilation, resulting in a decrease of middle ear pressure, whereas CO2 diffused into the middle ear cleft when the PvCO2 was elevated by hypoventilation, resulting in an increase of middle ear pressure. These findings suggest that a bidirectional CO2 exchange via the middle ear mucosa functions in the normal human middle ear.

Dentofacial morphology and upper respiratory function in 8-10-year-old children.

The aim of this preliminary study was to assess the nature of associations between selected dentofacial morphological variables and respiratory mode as measured by percent nasality (%N) as part of an ongoing longitudinal study. Cross-sectional cohort study. The Pediatric Clinical Study Center, Children's Hospital, Columbus, OH. Ninety-eight normal children were tested. Normal variation in %N. Selected dentofacial morphological variables including total and lower anterior face heights, face width, and palatal arch width and %N were estimated. Small associations between morphologic features and respiratory mode were found, but none were statistically significant. No evidence exists for the classic association between 'mouth breathing' and the stereotype of the 'adenoid facies'.

The effect of respiratory mode on human middle ear pressure

The purpose of this study was to examine the effect of respiratory mode on the human middle ear pressure. The partial pressure of carbon dioxide in the venous blood (PvCO 2) and the middle ear pressure were increased by hypoventilation, and decreased by hyperventilation. The partial pressure of oxygen in the venous blood showed little change. It was considered that CO 2 diffused into the middle ear cleft according to the partial pressure gradient when the PvCO 2 was elevated by hypoventilation, resulting in increase of the middle ear pressure, whereas CO 2 diffused into the blood from the middle ear cleft when the PvCO 2 was reduced by hyperventilation, resulting in decrease of the middle ear pressure. These findings suggest that bidirectional gas exchange via the middle ear mucosa functions actively in the human middle ear and plays an essential role in the regulation of the middle ear pressure.

Optimization and mechanism of step–leap respiration exercise in treating of cor pulmonale

The interaction between cardiovascular system and the respiratory system is complicated and may be used for the rehabilitation of the cor pulmonale disease. To study the effects of different breathing mode on the cardiac and pulmonary systems, a mathematical model is established based on the previous work. Using this model, computer simulation experiments are carried out for searching an optimal respiration mode in treating of cor pulmonale disease. Results indicate that the step–leap respiration mode could provide a better assistant to the rehabilitation of the cor pulmonale patients in the sense of increasing coronary flow, reducing pulmonary arterial pressure and reducing the working load for the right heart. This result is also proven by the clinical experiments. This work may suggest that a proper directed respiration exercise can be used in the treatment of cor pulmonale disease.

Inhibition of masseteric electromyographic activity during oral respiration

Although the effects of oral respiration on the growth and development of craniofacial structure have been studied previously, little is known about how altered respiration affects the activity of the jaw-closing muscles. Obstruction of the nasal airway in the cat significantly inhibited the masseteric stretch reflex and discharges of masseteric motor units but did not affect the electromyographic activity of the diaphragm. This inhibition was greater during inspiration than during expiration. In addition, the amplitude of the masseteric monosynaptic reflex elicited by electrical stimulation of the mesencephalic trigeminal nucleus showed no significant change in association with the altered respiratory mode. These findings suggest that masseteric electromyographic activity is inhibited during oral respiration and that the γ-system is involved in this inhibition. (Am J Orthod Dentofacial Orthop 1998;113:518-25.)

Bioenergetics of sulphate-reducing bacteria in relation to their environmental impact.

The cellular physiology of the sulphate-reducing bacteria, and of other sulphidogenic species, is determined by the energetic requirements consequent upon their respiratory mode of metabolism with sulphate and other oxyanions of sulphur as terminal electron acceptors. As a further consequence of their, relatively, restricted catabolic activities and their requirement for conditions of anaerobiosis, sulphidogenic bacteria are almost invariably found in nature as component organisms within microbial consortia. The capacity to generate significant quantities of sulphide influences the overall metabolic activity and species diversity of these consortia, and is the root cause of the environmental impact of the sulphidogenic species: corrosion, pollution and the souring of hydrocarbon reservoirs.

Simulation Study of the Interaction between Respiration and the Cardiovascular System

Many studies have been done on the respiratory and the cardiovascular system. Among them, only a few are on the interaction of these two physiologic systems. To explore the mechanism of the integration of these two physiological systems, computer simulation has been done; we report the preliminary results obtained in our laboratory. In this study, a mathematical model of the cardiovascular system integrated with the respiratory mechanical system has been established. The model is based on our previous work on cardiovascular modeling. The previous lumped lung model has been replaced by a multielement model with more detail. Interthoracic and abdominal pressures and modeled as external pressure sources on the related cardiovascular elements. Using this model, a sequence of simulation studies have been carried out. Different respiratory modes have been simulated and the different effects are observed in the simulation results. The results indicate that by following a certain respiratory pattern, the circulation status can be improved. These results agree with clinical observations.

Biochemical and spectroscopic characterization of two new cytochromes isolated from Desulfuromonas acetoxidans.

The multimeric cytochromes described to date in sulfate- and sulfur-reducing bacteria are associated with diverse respiratory modes involving the use of elemental sulfur or oxidized sulfur compounds as terminal acceptors. They exhibit no structural similarity with the other cytochrome c classes and are characterized by a bis-histidinyl axial iron coordination and low redox potentials. We have purified two new cytochromes c with markedly different molecular masses (10 000 and 50 000) from the bacterium Desulfuromonas acetoxidans, which uses anaerobic sulfur respiration as its sole energy source. The characterization by electrochemistry and optical and EPR spectroscopies revealed the cytochrome c (Mr = 10 000) to be the first monohemic cytochrome c exhibiting a bis-histidinyl axial coordination and a low redox potential (-220 mV). The cytochrome c (Mr = 50 000) contains four hemes of low potential (-200, -210, -370, and -380 mV) with the same axial coordination. The N-terminal amino acid sequences were compared with that of the trihemic cytochrome c7, previously described in D. acetoxidans and which is related to tetrahemic cytochrome c3 from sulfate reducing bacteria. Some homology was found between cytochrome c (Mr = 10 000) and cytochrome c7. Both D. acetoxidans cytochromes c are located in the periplasmic space and their biochemical and spectroscopic properties indicate that they belong to the class III cytochromes.

Comparison of Pressure Support Ventilation and Assist-Control Ventilation in the Treatment of Respiratory Failure

To assess whether pressure support ventilation (PSV) could be used as an alternative ventilatory mode to assist-control (A/C) ventilation in the treatment of respiratory failure. A short-term (4-h) prospective study in which the beneficial effect of PSV on respiratory mechanics, gas exchange, arterial oxygenation, cardiovascular hemodynamics, and oxygen consumption was compared with A/C ventilation. ICU of a community hospital. Forty-five patients (mean age, 62.8 [11.8] years) with respiratory failure secondary to COPD, restrictive disorders, or neuromuscular disease requiring mechanical ventilatory support in the ICU were selected for study. The mean duration of mechanical ventilation before the study was 7.16 (8.64) days. Patients were switched to the PSV mode of the mechanical ventilator for a period of 4 h after which conventional A/C ventilation was resumed. Patients supported with PSV compared with A/C ventilation showed significantly higher tidal volume, minute ventilation, and inspiratory time in association with significantly lower pressure in the airway and I:E ratio. With regard to gas exchange data, an increase in dead space/tidal volume ratio (VD/VT), decrease in PaO2, and statistically but not clinically significant alteration of arterial oxygenation indexes were noted. However, when patients with COPD, restrictive disorders, and neuromuscular disease were compared, significant changes in arterial oxygenation parameters were found only in patients with restrictive disorders. There were significant decreases in heart rate, systolic pulmonary artery pressure, and pulmonary capillary wedge pressure when PSV was applied. Oxygen transport and oxygen consumption were unchanged. PSV could be a possible alternative to A/C ventilation in patients with respiratory failure. PSV caused an increase in VD/VT in association with a significantly lower pressure in the airway and I:E ratio. Randomized studies are needed to define the long-term benefits of both respiratory modes and the conditions in which PSV may be a valuable alternative to A/C ventilation.

Cerebral blood flow velocity and pulsation in neonatal respiratory distress syndrome and periventricular hemorrhage

The present study addressed the hypotheses that cerebral ischemia and/or excessive cerebral blood pulsation contribute to periventricular hemorrhage in preterm newborns with respiratory distress and that the pulse width is a valuable tool to estimate the contribution of cerebral blood pulsation. These hypotheses were tested by following preterm newborns at risk for respiratory distress and periventricular hemorrhage. We monitored for cerebral blood flow velocity (CBFV), cerebral pulse width, and cerebral pulsatility index; for patent ductus arteriosus, capillary Pco 2, heart rate (HR) and behavior; and for the occurrence of respiratory distress and periventricular hemorrhage (PVH). The data obtained were analyzed with linear regression with the mode of respiration (spontaneous or supported) and postnatal age as additional covariates. We observed that (a) respiratory distress, either uncomplicated or complicated by PVH, correlates with a low CBFV and a high cerebral pulsatility index; (b) PVH also correlates with a high cerebral pulse width; (c) the increased pulse width precedes the onset of the hemorrhage; and (d) these CBF alterations can be partly attributed to ductal shunting and are ameliorated by mechanical ventilation.

Clinical study of PEtCO2 in one-lung ventilation

Fourty-eight patients (ASA physical status I — I) undergoing selected thoracotomy and pulmonectomy were studied. They were divided into two groups according to different respiratory modes, two-lung ventilation (TLV) and onelung ventilation (OLV) or TLV and OLV with a Bain cyclic system for CPAP on the side of operated lung. PetCO2 and PaCO2 were measured after 30 min TLV, 30 min and 60 min OLV, and repeated TLV (R-TLV) 30 min after pulmonectomy, to evaluate the difference between PetCO2 and PaCO2 in OLV and to observe the effect of abating hypoxemia and discharge of CO2 in OLV with Bain system. Our results showed that the PaCO2 and PetCO2 in different test groups were normal though the measured values in OLV were slightly higher than that in TLV (P 0. 05). There was no significant difference between group 1. and 2. in OLV (P>0. 05). There was a close correlation between PetCO2 and PaCO2(P<0.05). The differences of the calculated P(a-et)CO2 and radio of PetCO2/ PaCO2 in different ventilation modes were not significant. Hypoxemia in OLV was corrected by Bain system, but the discharge of CO2 was not affected. The results showed that measurement of Pet CO2 as a non-invasive procedure can be commonly used to monitor OLV.

Semi-continuous versus injectate cardiac output measurement in intensive care patients after cardiac surgery.

Commercially available semi-continuous cardiac output (SCCO) monitoring systems are based on the pulsed warm thermodilution technique. There is evidence that SCCO fails to correlate with standard intermittent bolus cardiac output (ICO) in clinical situations with thermal instability in the pulmonary artery. Furthermore, ventilation may potentially influence thermodilution measurements by enhanced respiratory variations in pulmonary artery blood temperature and by cyclic changes in venous return. Therefore, we evaluated the correlation, accuracy and precision of SCCO versus ICO measurements before and after extubation. Prospective cohort study. Intensive care unit (ICU) of a university hospital. 22 cardiac surgical ICU patients. None. SCCO and ICO data were obtained at nine postoperative time points while the patients were on controlled mechanical ventilation. Further sets of measurements were taken during the weaning phase 20 min before extubation, and 5 min, 20 min and 1 h after extubation. SCCO and ICO measurements yielded 286 data pairs with a range of 1.8-9.9 l/min for SCCO and 1.9-9.8 l/min for ICO. The correlation between SCCO and ICO was highly significant (r = 0.92; p < 0.01), accompanied by a bias of -0.052 l/min and a precision of 0.56 l/min. Correlation, accuracy and precision were not influenced by the mode of respiration. Our results demonstrate excellent correlation, accuracy and precision between SCCO and ICO measurements in postoperative cardiac surgical ICU patients. We conclude that SCCO monitoring offers a reliable clinical method of cardiac output monitoring in ICU patients following cardiac surgery.

Model-based QSAR for ionizable compounds: Toxicity of phenols against Tetrahymena pyriformis

The previously described pseudo-equilibrium model for kinetics of distribution of extraneous chemicals in biological systems has been used for the development of the QSAR equation expressing toxicity of phenols against Tetrahymena pyriformis as a non-linear function of their hydrophobicity and acidity. The model assumes binding of all the tested compounds to a single class of the receptors (i.e., it does not discriminate between possible narcotic and respiratory uncoupling modes of action of phenols) with the association constant related to the electronic structure of the molecules rather than to their hydrophobicity. Non-linear regression analysis revealed satisfying agreement between the model and published biological data measured after a single dose.

Respiratory and cutaneous evaporative water loss at high environmental temperatures in a small bird

We measured rates of respiratory and cutaneous evaporative water loss as a function of air temperature in a small desert bird, the verdin Auriparus flaviceps. Birds were placed in a two-compartment metabolic chamber that separately collected water evaporated from the bird's head and body. Cutaneous and respiratory evaporative water loss, as well as CO2 production, were measured in resting birds at 2 &deg;C intervals between 30 and 50 &deg;C. Metabolic rate was lowest at 38 &deg;C (19 mW g-1) and increased to 28 mW g-1 at 50 &deg;C. At the lowest air temperature, 30 &deg;C, resting metabolic rate was 34 mW g-1. As air temperature increased from 30 to 50 &deg;C, cutaneous water loss increased from 3.3 to 10.3 mg g-1 h-1 and respiratory water loss increased from 2.1-64.1 mg g-1 h-1. At moderate air temperatures (30-36 &deg;C), water loss was divided almost evenly between respiratory and cutaneous components. As air temperature increased, however, verdins became heavily dependent on respiratory evaporation for heat dissipation. Evaporative water loss data for other species at high air temperatures suggest that partitioning of water loss may follow two different patterns. Evaporative heat dissipation may depend primarily on either cutaneous or respiratory modes of evaporative heat transfer. The physiological mechanisms and functional significance of these contrasting patterns of evaporative heat loss remain unknown.

Nasorespiratory characteristics and craniofacial morphology

The relationship between respiration and craniofacial morphology has been debated for many years. Despite numerous studies, the term 'mouth breathing' remains ill-defined. Still, medical and surgical treatments are performed in order to modify respiration and 'improve' facial growth. This clinical belief continues, in the absence of conclusive evidence, that a causal relationship exists between oral respiration and facial growth, or that such treatment modalities and their associated risks actually modify respiratory mode. Moreover, diagnostic indicators have been postulated for the identification of patients for whom such therapy would be beneficial. The purpose of this study was to investigate the strength of association between mode of respiration and craniofacial morphology. In addition, the precision level was calculated for two popular cephalometric tests for possible nasal impairment. The results suggest that: (1) cephalometric analyses are poor indicators of nasal impairment and should not be used in clinical decision making, and (2) facial morphology and respiratory mode are unrelated.

Effect of low-level PEEP on inspiratory work of breathing in intubated patients, both with healthy lungs and with COPD

Evaluation of low-level PEEP (5 cm H2O) and the two different CPAP trigger modes in the Bennett 7200a ventilator (demand-valve and flow-by trigger modes) on inspiratory work of breathing (Wi) during the weaning phase. Prospective controlled study. The intensive care unit of a university hospital. Six intubated patients with normal lung function (NL), ventilated because of non-pulmonary trauma or post-operative stay in the ICU, and six patients recovering from acute respiratory failure due to exacerbation of chronic obstructive pulmonary disease (COPD), breathing either FB-CPAP or DV-CPAP with the Bennett 7200a ventilator. The patients studied were breathing with zero end-expiratory pressure (ZEEP), as well as CPAP of 5 cm H2O (PEEP), with the following respiratory modes: the demand-valve trigger mode, pressure support of 5 cm H2O, and the flow-by trigger mode (base flow of 20 l/min and flow trigger of 2 l/min). Furthermore, Wi during T-piece breathing was evaluated. Wi was determined using a modified Campbell's diagram. Total inspiratory work (Wi), work against flow-resistive resistance (W(ires)), work against elastic resistance (Wiel), work imposed by the ventilator system (W(imp)), dynamic intrinsic positive end-expiratory pressure (PEEPidyn), airway pressure decrease during beginning inspiration (P(aw)) and spirometric parameters were measured. In the NL group, only minor, clinically irrelevant changes in the measured variables were detected. In the COPD group, in contrast, PEEP reduced Wi and its components W(ires) and Wiel significantly compared to the corresponding ZEEP settings. This was due mainly to a significant decrease in PEEPidyn when external PEEP was applied. Flow-by imposed less Wi on the COPD patients during PEEP than did demand-valve CPAP. Differences in W(imp) between the flow-by and demand-valve trigger models were significant for both groups. However, in relation to Wi these differences were small. We conclude that the application of low-level external PEEP benefits COPD patients because it reduces inspiratory work, mainly by lowering the inspiratory threshold represented by PEEPidyn. Differences between the trigger modes of the ventilator used in this study were small and can be compensated for by the application of a small amount of pressure support.