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At least 19 recordsLinked to original sources
PubMed2003

Assessment of the single-occlusion technique for measurements of respiratory mechanics and respiratory drive in healthy term neonates using a commercially available computerized pulmonary function testing system.

In this study, a critical assessment of the single-occlusion technique as a means of measuring passive respiratory mechanics and respiratory drive (P0.1) was performed in nonintubated spontaneously breathing healthy term neonates using commercially available computerized equipment (PEDS system). In general, we found that quality parameters only partially conformed to the international established standards for measuring passive respiratory mechanics. There was a failure rate of technically acceptable occlusions of about 50% for respiratory mechanics measurements and 20% for P0.1 measurements. Intersubject variability of the data was between 10 and 40%. After studying different lengths of occlusion times (Tocc; 0.2, 0.3, 0.4 and 0.5 s), it was found that acceptable occlusions for passive respiratory mechanics were obtained only if the expiratory Tocc exceeded 0.2 s. Increasing the Tocc had no effect on the absolute values of respiratory mechanics but showed a significant trend towards more technically acceptable occlusions. We speculate that a Tocc of at least 0.4 s may be a prerequisite for obtaining reliable results for respiratory mechanics in healthy term neonates.

Electronic Data Processing↗
PubMed1983

Comparative mammalian respiratory mechanics.

Respiratory mechanics can be studied in mammals of all sizes by the same methods used in man, although some definitions need to be modified and special attention given to small size and fast events. Mechanical properties vary with body size in regular ways. Operating pressures are invariant with size, volumes and compliances varying with body mass (M) approximately to the first power, and ventilation and conductance with M3/4. Thus, time constants vary with M1/4 and frequencies with M -1/4. Tracheal cross-section varies with M3/4 and appears to be constrained by expiratory flow-limitation mechanics. Smaller mammals have more compliant chest walls and lower relaxation volumes, so FRC is more likely to be influenced by reflex and dynamic mechanisms. Methods and procedures are not standardized; variability of observations is great and our ability to discriminate specialized characteristics is undeveloped. Recent fundamental challenges to conceptual foundations of scaling are unresolved. Thus, uncertainty and skepticism about existing views are appropriate.

Animals↗
PubMed1998

Studies on the respiratory system in alkaliphilic Bacillus; a proposed new respiratory mechanism.

Respiratory electron transfer systems in two alkaliphilic Bacillus species, YN-1 and YN-2000, were investigated In the cyanide-sensitive pathway of the obligate alkaliphilic Bacillus YN-1, the terminal enzyme was a caa3-type cytochrome c oxidase constituting up to just 10% of the total oxygen-reducing activity, while 90% of the respiratory activity was due to cyanide-insensitive, nonproteinaceous material with a molecular weight of 662. These results were consistent with the cyanide-tolerant growth of the bacterium. The molecular and catalytic properties of the nonproteinaceous material were not identical with those of menaquinones extracted from the bacterium. Furthermore, the nonproteinaceous material was also found in the facultative alkaliphilic Bacillus YN-2000, when that bacterium was cultivated in alkaline conditions. A new respiratory oxygen-reducing mechanism comprising a nonproteinaceous component and a catalase is proposed for these alkaliphilic Bacillus species.

Bacillus↗
PubMed1996

[Variation in inspiratory gas flow in pressure support ventilation. The effect on respiratory mechanics and respiratory work].

UNLABELLED: During pressure support ventilation (PSV), the timing of the breathing cycle is mainly controlled by the patient. Therefore, the delivered flow pattern during PSV might be better synchronised with the patient's demands than during volume-assisted ventilation. In several modern ventilators, inspiration is terminated when the inspiratory flow decreases to 25% of the initial peak value. However, this timing algorithm might cause premature inspiration termination if the initial peak flow is high. This could result not only in an increased risk of dyssynchronization between the patient and the ventilator, but also in reduced ventilatory support. On the other hand, a decreased peak flow might inappropriately increase the patient's inspiratory effort. The aim of our study was to evaluate the influence of the variation of the initial peak-flow rate during PSV on respiratory pattern and mechanical work of breathing. PATIENTS: Six patients with chronic obstructive pulmonary disease (COPD) and six patients with no or minor nonobstructive lung pathology (control) were studied during PSV with different inspiratory flow rates by variations of the pressurisation time (Evita I, Drägerwerke, Lübeck, Germany). During the study period all patients were in stable circulatory conditions and in the weaning phase. METHOD: Patients were studied in a 45 degrees semirecumbent position. Using the medium pressurization time (l s) during PSV the inspiratory pressure was individually adjusted to obtain a tidal volume of about 8 ml/kg body weight. Thereafter, measurements were performed during five pressurization times (< 0.1, 0.5, 1, 1.5, 2 s defined as T 0.1, T 0.5, T 1, T 1.5 and T 2) in random order, while maintaining the pressure support setting at the ventilator. Between each measurement steady-state was attained. Positive end-exspiratory pressure (PEEP) and FIO2 were maintained at prestudy levels and remained constant during the study period. Informed consent was obtained from each patient or his next of kin. The study protocol was approved by the ethics committee of our medical faculty. Gas flow was measured at the proximal end of the endotracheal tube with a pneumotachometer (Fleisch no. 2, Fleisch, Lausanne, Switzerland) and a differential pressure transducer. Tracheal pressure (Paw) was determined in the same position with a second differential pressure transducer (Dr. Fenyves & Gut, Basel, Switzerland). Esophageal pressure (Pes) was obtained by a nasogastric balloon-catheter (Mallinckrodt, Argyle, NY, USA) connected to a further differential pressure transducer of the same type as described above. The balloon was positioned 2-3 cm above the dome of the diaphragm. The correct balloon position was verified by an occlusion test as described elsewhere. The data were sampled after A/D conversion with a frequency of 20 Hz and processed on an IBM-compatible PC. Software for data collection and processing was self-programmed using a commercially available software program (Asyst 4.0, Asyst Software Technologies, Rochester, NY, USA). Patient's inspiratory work of breathing Wpi (mJ/l) was calculated from Pes/ volume plots according to the modified Campbell's diagram. Dynamic intrinsic PEEP (PEEPidyn) was obtained from esophageal pressure tracings relative to airway pressure as the deflection in Pes before the initiation of inspiratory flow Patient's additive work of breathing (Wadd) against ventilator system resistance was calculated directly from Paw/V tracings when Paw was lower than the pressure on the compliance curve. Two-way analysis of variance (ANOVA) was used for statistical analysis, followed by post hoc testing of the least significant difference between means for multiple comparisons. Probability values less than 0.05 were considered as significant. RESULTS: COPD patients had significantly higher pressure support than control patients. With decreasing inspiratory flow, Wpi increased significantly in COPD patients.(ABSTRACT TRUNCATED)

Adult↗
PubMed1982

[Respiratory mechanics and respiratory regulation in healthy and respiratory-diseased newborn infants of different gestational ages].

The interaction of lung mechanics, peripheral lung reflexes and chemosensitivity of the respiratory center were studied in over 80 newborns. Healthy newborns (gestational age between 30 and 41 weeks) and newborns with respiratory distress syndrome (RDS) (gestational age between 29 and 40 weeks) were studied on the first day of life. Spontaneously breathing newborns were examined using the airway occlusion technique (AOT), and intubated babies using the injection technique (IT) to measure the compliance of the respiratory system (Crs), the strength of the inspiration inhibiting reflex (IIR) and inspiratory time during airway occlusion (Ti occ), and index of chemosensitivity of the respiratory center. Crs in healthy newborns increased only slightly but statistically significant (p less than 0.001) with gestational age. Crs of newborns with RDS had an overwhelming influence on their prognosis. Newborns with Crs of less than or equal to 1 developed respiratory failure and needed ventilatory support. Newborns with a Crs less than or equal to 0.5 died despite respiratory therapy. The activity of the peripheral vagally mediated reflex system also depended on the Crs. Our results indicate that the decrease in reflex activity with gestational age is not brought about by neurologic maturation but is caused by the increasing Crs. We conclude that the peripheral vagally mediated reflexes remain the same throughout life, just the boundary condition Crs, which is given by the lung mechanics, is different for premature or mature newborns and changes with age. The chemosensitivity of the respiratory center for CO2 was characterized by the inspiratory time after an expiratory occlusion (Ti occ) which is not influenced by lung mechanics. Ti occ correlated significantly with pCO2. The relation between Ti occ and pCO2 was similar for premature and mature, healthy and respiratory ill newborns. Consequently, chemosensitivity, expressed as the ratio of Ti occ and pCO2, is independent of gestational age.

Carbon Dioxide↗
PubMed2001

Optimal tracheal tube cuff inflation in infants: implications for mechanical ventilation and respiratory mechanics.

Uncuffed tracheal tubes (TT) are used to intubate infants and children to avoid laryngotracheal tissue injury. The geometric mismatch resulting from such intubation limits the efficacy of mechanical ventilation, and reliability of derived respiratory mechanical properties. This study tested the hypotheses that (1) normal stresses applied to the cuff surface by leak flows during ventilation result in intracuff pressure (Pcuff) fluctuations proportionate to leak magnitudes, and (2) these fluctuations reach a steady minimum when cuff volume reaches a critical value (Vcrit) at which the TT-airway mismatch is removed. Physical model and piglet measurements showed that, during simultaneous cuff inflation and mechanical ventilation, Pcuff consisted of a leak-dependent (Pcuff,l) component that cycles with the ventilator superimposed on a ramp rise due to cuff inflation. The breath-to-breath peak Pcuff,l (max Pcuff,l) decreased as leak flows are reduced, and these were relatively greater for higher ventilator flows and when the load impedance is increased such as by disease. These results describe a reproducible method of TT cuff inflation that removes leaks without increased risk of laryngotracheal tissue injury. Moreover, inflation of the TT cuff more securely improved ventilation efficacy and allowed for accurate respiratory mechanics.

Airway Resistance↗
PubMed1997

Effects of nebulized salbutamol on respiratory mechanics in adult respiratory distress syndrome.

OBJECTIVE: To determine whether nebulized salbutamol improves the respiratory mechanics of patients with adult respiratory distress syndrome (ARDS). We also assessed the mechanisms that contribute to high respiratory system resistances during this disease. PATIENTS AND SETTING: Eleven consecutive patients with ARDS without clinical evidence of chronic obstructive pulmonary disease, admitted to a polivalent intensive care unit, and mechanically ventilated with Siemens Elema Servo C ventilator at constant inspiratory flow. METHOD: Peak airway pressure (Ppeak), airway pressure immediately after end inspiratory occlusion (P1), plateau pressure (P2) and intrinsic positive end-expiratory pressure (PEEPi) were measured at baseline condition and then 5, 15, and 30 min after 1 mg of salbutamol had been administered via a nebulizer through the endotracheal tube. Partial pressure of arterial oxygen (PaO2), heart rate (HR) and mean blood pressure (BP) were monitored and minimal respiratory system resistances (Rrs, m), additional resistances (DRrs) and static compliance (Cst) were computed. RESULTS: Between baseline and post-salbutamol, we observed changes in Ppeak, P1, P2, PEEPi and Rrs, m. As there were no significant differences between values at the different intervals during post administration, the results are described comparing baseline and 15 min post-salbutamol administration values. We found a significant decrease in Ppeak (4.9 +/- 0.8 cmH2O). P1 (3 +/- 0.6 cmH2O). P2 (2.1 +/- 0.6 cmH2O), PEEPi (1.9 +/- 0.5 cmH2O) and Rrs, m (1.9 +/- 0.3 cmH2O/1 s-1); DR, rs decreased in five patients, did not change in four and increased in two. HR, PaO2 and BP did not change. CONCLUSIONS: a) Salbutamol administered through the endotracheal tube by a nebulizer device lessens respiratory system resistances and airway and alveolar pressures, and therefore could decrease the risk of barotrauma and alveolar damage; b) high respiratory system resistances in ARDS have an increased smooth muscle tone component that can be reversible with salbutamol.

Adult↗
PubMed1997

Effects of ventilation in ventral decubitus position on respiratory mechanics in adult respiratory distress syndrome.

OBJECTIVE: To assess the potential benefits of a period of ventilation in ventral decubitus (VD) on oxygenation and respiratory mechanics in the adult respiratory distress syndrome (ARDS). DESIGN: In a stable condition during baseline ventilation in dorsal decubitus (DD), after 15 min of ventilation in VD and after 10 min of restored DD, the following parameters were studied: arterial blood gas tension, haemodynamics and static respiratory compliance (Crs), evaluated with the rapid airway occlusion technique. SETTING: The study was completed in the intensive care units of university hospitals as part of the management of the patients studied. PATIENTS: Twelve patients (7 males, 5 females, mean age 51.8 +/- 16.6 years) suffering from ARDS of different aetiologies. INTERVENTIONS: Before and during each evaluation, the patients were kept under stable haemodynamic and metabolic conditions. The ventilatory setting was kept constant. All the patients were sedated, paralysed and mechanically ventilated. RESULTS: A statistically significant increase in the ratio between the arterial partial pressure of oxygen and fractional inspired oxygen (p < 0.01) was observed between the baseline conditions (mean 123.9 +/- 22.6) and VD (mean 153.0 +/- 16.9), while no statistical significant was noted between baseline conditions and after 10 min of restored DD (mean 141.1 +/- 19.7). A significant increase in Crs (p < 0.001) was observed between baseline conditions (mean 42 +/- 10.1) and VD (mean 48.8 +/- 9.6) and between baseline conditions and restored DD (mean 44.7 +/- 10.6). Two patients were considered nonresponders. All the patients were haemodynamically stable. No side effects were noted. CONCLUSIONS: We observed an increase in oxygenation and Crs when the patients were turned from the supine to the prone position with the upper thorax and pelvis supported.

Adult↗
PubMed1995

Respiratory mechanics after tube thoracostomy in rats.

The purpose of the present study was to determine the mechanical respiratory profile after the insertion of a catheter into the pleural cavity of anesthetized, paralyzed, mechanically ventilated rats, thus stimulating the common use of chest tubes in clinical situations. Using the method of end-inflation occlusion during constant inspiratory flow in 7 adult Wistar rats, respiratory system, lung, and chest wall total resistance (0.353 +/- 0.058, 0.260 +/- 0.651, 0.091 +/- 0.012 (mean +/- SD) cmH2O.ml-1.s, respectively), viscous resistance (0.140 +/- 0.007, 0.100 +/- 0.007, 0.040 +/- 0.003 cmH2O.ml-1.s< respectively), and viscoelastic resistance (0.213 +/- 0.017, 0.160 +/- 0.022, 0.053 +/- 0.011 cmH2O.ml-1.s, respectively) as well as respiratory system, lung, and chest wall static elastance (4.51 +/- 0.27, 3.85 +/- 0.28, 0.66 +/- 0.12 cmH2O.ml-1, respectively), and dynamic elastance (5.72 +/- 0.24, 4.76 +/- 0.32, 0.96 +/- 0.17 cmH2O.ml-1, respectively) were not significantly modified after the insertion of a tube into the second right intercostal stage. We conclude that, under the present experimental conditions, a catheter inserted into the pleural space per se is not responsible for any alterations in respiratory mechanics.

Airway Resistance↗
PubMed1983

[Respiratory physiotherapy and respiratory mechanics of chronic respiratory insufficiency].

The effect of short, medium and long term physiotherapy remain controversial. The theoretical objectives of the method are to reduce dyspnoea and respiratory disability while improving exercise performance and expectation of life. As regards respiratory mechanics, the goals are to reduce bronchial obstruction and the mechanical properties of the chest wall. A rise in expiratory flow might result in an increased drainage of secretions, a reduction in transmural bronchial pressure and a raised level of ventilation at end-tidal volume. The correction of parietal distortions by physiotherapy has as an objective a diminution of thoracic elastance. Muscular training, a new aspect of respiratory physiotherapy, consists of increased both the endurance and the force of contraction of the respiratory muscles. The beneficial effects of these recent methods require confirmation with long term clinical studies. The correct indications for the diverse techniques proposed require a better understanding of the mechanism of action of respiratory physiotherapy, an essential complement to effective treatment of chronic airflow obstruction.

Biomechanical Phenomena↗
PubMed1998

How stiff is the armadillo? A comparison with the allometrics of mammalian respiratory mechanics.

Static respiratory mechanics were examined in the armadillo (Dasypus novemcinctus) and compared with allometric relationships newly derived for adult mammals from values in the literature. Normalised by body weight, chest wall compliance (Cw) in the armadillo is lower than predicted. Lung compliance (Cl) is also low in the armadillo, however it is appropriately matched to the resting lung volume (Vr) (ie. Cl/Vr infinity Mass0.0) and the ratio of Cw/Cl is appropriate for the size of the animal. Respiratory system resistance is high in the armadillo, presumably because of smaller airways associated with the small lung. The power of breathing in the armadillo is comparatively high, mainly due to the high resistive forces. Indeed, the oxidative cost of breathing is approximately double that of a mammal with similar Vr. Hypoxia or hypercapnia are known to invoke an attenuated ventilatory response in the armadillo and one that relies more on changes in frequency rather than volume. While such a breathing pattern helps to reduce the power of breathing it also compromises the degree of hyperventilation achieved.

Airway Resistance↗
PubMed2000

[The effects of different patterns of mechanical ventilation on the respiratory mechanics and gas exchange in dogs severely injured by steam inhalation].

OBJECTIVE: To study the effects of conventional mechanical ventilation (CMV), high-frequency jet ventilation (HFJV) and high-frequency bidirectional jet ventilation (HFTJV) on the respiratory mechanics and gas exchange in dogs inflicted severely by steam inhalation injury. METHODS: Nine mongrel dogs inflicted by steam inhalation to severe inhalation injury were served as the model. Indices of respiratory mechanics, hemodynamics and blood gas analysis were monitored respectively with the above three patterns of mechanical ventilation. RESULTS: (1) Total respiratory resistance (Rrs) and resistance of lungs (R(L)) were evidently higher with the ventilations than those in control (P < 0.01). And total respiratory compliance (Crs) and compliance of lungs (C(L)) were obviously lower with the ventilations than those in control (P < 0.05) but with no significant differences among the changes of Rrs, R(L), Crs and C(L). (2) Carbon dioxide (CO(2)) retention could be induced by CMV and HFJV. HFTJV was much more effective than HFJV in enhancing the expiration of CO(2) (P < 0.01). (3) There was no remarkable difference in functional residual capacity (FRC) and PaO2 between dogs with three patterns of ventilations. CONCLUSION: All these three patterns of ventilations could overcome the respiratory resistance and help respiration, but they couldn't restore the high airway resistance and low compliance of lungs already established postburn. The efficiency of CMV was similar to that by HFJV, but that of HFTJV was much better than that of HFJV.

Animals↗
PubMed2006

[Study on the method of measurement of respiratory mechanical parameters].

Respiratory mechanical parameters are the key indexes in evaluating the respiratory function of an anaesthetized patient during operation. The measurement of respiratory parameters plays an important role in clinic, and can dynamically monitor the working state of a respirator, direct the use of a respirator and monitor the respiratory function of a patient in intensive care unit(ICU). This paper introduces a new method that will break the traditional limitations, can measure eleven respiratory parameters and demonstrate the results by digital and diagrams.

Equipment Design↗
PubMed2000

Effects of periodic lung recruitment maneuvers on gas exchange and respiratory mechanics in mechanically ventilated acute respiratory distress syndrome (ARDS) patients.

OBJECTIVE: We wished to investigate whether volume recruitment maneuvers (VRMs) could improve alveolar recruitment and oxygenation in acute respiratory distress syndrome (ARDS) patients, ventilated at relatively low positive end-expiratory pressure (PEEP). SETTING: General intensive care unit (ICU) located in a teaching hospital. PATIENTS: 15 PEEP responder ARDS patients undergoing continuous positive pressure ventilation (CPPV) with sedation and muscle paralysis. INTERVENTIONS: We identified a low (9.4 +/- 3 cmH2O) and a high (16.0 +/- 2 cmH2O) level of PEEP associated with target oxygenation values. Using a custom modified mechanical ventilator, we applied in random order three steps lasting 30 min: (1) CPPV at the low PEEP level (CPPV(LO)); (2) CPPV at the high PEEP level (CPPV(HI)); (3) CPPV at low PEEP with the superimposition of periodic VRMs (CPPV(VRM)). VRMs were performed twice a minute by increasing PEEP to the high level for two breaths. Each brace of two breaths was spaced 30 seconds from the preceding one. MEASUREMENTS AND RESULTS: We measured gas exchange, hemodynamics, respiratory mechanics, and the end expiratory lung volume (EELV). Compared to CPPV(LO), CPPV(VRM) resulted in higher PaO2 (117.9 +/- 40.6 vs 79.4 +/- 13.6 mmHg, P < 0.01) and EELV (1.50 +/- 0.62 vs 1.26 +/- 0.50 l, P < 0.05), and in lower venous admixture (Q(VA)/Q(T)) (0.42 +/- 0.07 vs 0.48 +/- 0.07, P < 0.01). During CPPV(HI), we observed significantly higher PaO2 (139.3 +/- 32.5 mmHg) and lower Q(VA)/Q(T) (0.37 +/- 0.08) compared to CPPV(LO) (P < 0.01) and to CPPV(VRM) (P < 0.05). CONCLUSIONS: VRMs can improve oxygenation and alveolar recruitment during CPPV at relatively low PEEP, but are relatively less effective than a continuous high PEEP level.

Adult↗