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At least 793 records · Page 44Linked to original sources
PubMed1992

A new ventilator converter with the Siemens Servo Ventilator--evaluation in a lung model.

A ventilator converter device (Anmedic) for connecting a non-rebreathing ventilator (Servo Ventilator 900 B; Siemens-Elema) to a circle anaesthesia system was evaluated in a lung model. Recorded minute ventilation was slightly lower than dialled in most cases. We furthermore found inadequate expiratory expansion of the ventilator converter bellows, with progressive loss of tidal volume and consequently recorded minute volume, when fresh gas flow to the circle system was low (1 l.min-1), expiratory time was short (less than 40%) and respiratory obstruction was present.

Airway Obstruction↗
PubMed1998

Effects of isoflurane on oxygenation during one-lung ventilation in pulmonary emphysema patients.

BACKGROUND: Hypoxic pulmonary vasoconstriction has an important role in human one-lung ventilation (OLV) in the lateral decubitus position under general anesthesia. During OLV, inhalational anesthesia may inhibit hypoxic pulmonary vasoconstriction and the decrease in arterial oxygenation. We studied the effect of isoflurane administration on arterial oxygen tension in chronic obstructive pulmonary disease patients. METHODS: Ten patients who had thoracoscopic laser ablation of bullous emphysema were studied. Patients received 2% isoflurane in oxygen from induction until the first 20 min of OLV in the lateral decubitus position, then were switched to 1% isoflurane lasting 20 min and next were switched to 0.5% isoflurane lasting 20 min. After each 20-min inhalation, pulmonary and hemodynamic parameters were measured. The given concentrations for isoflurane were merely vapor meter concentrations. RESULTS: PaO2/FIO2, Qs/Qt respiratory rate peak inspiratory pressure and PaCO2 showed no significant changes at each point of isoflurane. Expiratory tidal volume significantly decreased (P < 0.05) with 0.5% isoflurane compared to that with 2% isoflurane. Cardiac output, mean arterial pressure, mean pulmonary arterial pressure, systemic vascular resistance and pulmonary vascular resistance showed no significant changes at each point of isoflurane. CONCLUSIONS: In patients with pulmonary emphysema, arterial oxygenation is not affected by low isoflurane concentration during OLV in the lateral decubitus position.

Aged↗
PubMed1998

Effects of recruitment of collapsed lung units on the elastic pressure-volume relationship in anaesthetised healthy adults.

BACKGROUND: The elastic pressure-volume (Pel-V) curve of the respiratory system can be used as a guide for improved ventilator management. The understanding of curves recorded for sick patients can be improved with better knowledge of the Pel-V relationship observed in healthy humans. Dynamic Pel-V curves were determined over an extended volume range in 15 anaesthetised and muscle-relaxed healthy humans. The influence of a recruitment manoeuvre was studied. METHODS: Dynamic Pel-V curves were determined during a single prolonged insufflation before and after the recruitment manoeuvre. A mathematical three-segment model of the curve including a linear intermediate segment, delineated by the lower (LIP) and upper (UIP) inflection points, was used for characterisation of the recorded curves. RESULTS: The model gave an adequate description of the recorded Pel-V curves. Before the recruitment manoeuvre, compliance increased until the LIP was reached at 20 cm H2O (1.9 L). Then followed a long linear segment. After the recruitment manoeuvre, compliance increased during insufflation until a LIP was reached at 13 cm H2O (1.2 L). Above the LIP followed a shorter linear segment (compliance = 140 mL/cm H2O) and then an upper segment with decreasing compliance. CONCLUSION: Pel-V curves recorded before and after the recruitment manoeuvre show that large lung compartments close during anaesthesia and that high pressures are needed to achieve recruitment even in the normal lung. Accordingly, the LIP does not define the end of recruitment during insufflation.

Adult↗
PubMed1986

Pulmonary interstitial emphysema in infants less than 1000 g at birth.

Eighty (32%) of 249 infants weighing less than 1000 g at birth developed pulmonary interstitial emphysema (PIE); its incidence was 42% in infants at 500-799 g, 29% at 800-899 g and 20% at 900-999 g. Fifty-five per cent occurred in the first 24 h and 43% were associated with other forms of air leak. The incidence and mortality of PIE did not improve between 1977 and 1984. The mortality rates in infants with or without PIE were not significantly different in the first 4 years of the study period (53% vs 45%). As the mortality improved in infants without PIE during the second 4 years, the difference in mortality rates in infants with or without PIE became significant (68% vs 29%). PIE continues to be associated with serious mortality and morbidity in extremely low birthweight infants. Effective measures to prevent PIE are required before further improvement in their outcome can be achieved.

Female↗
PubMed2005

Predictive equations and the reliability of the impulse oscillatory system in Japanese adult subjects.

BACKGROUND: The impulse oscillation system (IOS) measures respiratory impedance (Zrs) in terms of resistance (Rrs) and reactance (Xrs) at multiples of 5 Hz. These measurements can be used clinically to help diagnose and monitor respiratory disorders, independent of effort. METHODOLOGY: The predictive equation for resistance at 5 and 20 Hz and impedance at 5 Hz (R5, R20, X5), for the first time, in 299 Japanese adult subjects was determined. In addition, the within single day variation and between day variation were determined. RESULTS: The predictive equation for R5, R20 and X5 revealed a clear difference with respect to the subject's smoking history (lifelong non-smoker, n = 166, adjusted r = 0.55, 0.46 and 0.57, respectively, vs. smoker, n = 133, adjusted r = 0.47, 0.42 and 0.47, respectively). This difference was less obvious with respect to gender (female, n = 120, adjusted r = 0.42, 0.20 and 0.47, respectively, vs. male, n = 179, adjusted r = 0.46, 0.37 and 0.47, respectively). The predictive equations were dependent on the log of height (H) for both R5 and R20, and on age and log of height for X5. The equations were: R5 (KPa/L/s) = -3.841167 x logH + 8.671580; R20 (KPa/L/s) = -2.546561 x logH + 5.841867; and X5 (KPa/L/s) = -0.000097 x Age + 1.018597 x logH - 2.343672. For these parameters there were no statistically significant differences for within day repeatability or between day variations (P > 0.05), suggesting a high degree of reproducibility for IOS measurements. CONCLUSION: It was possible to determine a predictive equation and confirm a high degree of reliability of IOS parameters in Japanese adult subjects.

Adult↗
PubMed1988

Does airway closure affect lung sound generation?

The purpose of this experiment was to test the hypothesis that airway closure impedes the production of lung sounds at low lung volume. We recorded breath sounds in three healthy men during inspiratory vital capacity manoeuvres in upright, head-down and lateral decubitus postures. We then compared the rate of increase of breath sound intensity (BSI) between the dependent and non-dependent lung zones. Closing volumes, measured separately, were normal in the upright but increased in the head-down postures. The data revealed no consistent lag in the rate of increase of BSI over the dependent lung zones in any of the postures. Our data suggest that airway closure does not influence lung sound generation. If true, this implies that lung sounds are produced proximally to the site of physiologic airway closure.

Adult↗
PubMed1997

Helium/oxygen breathing improves hypoxemia after cardiac surgery.

The effects of helium/oxygen (He/O2) on oxygenation (respiratory index [PaO2/FiO2] and intrapulmonary shunt [Qs/Qt]) and on lung parameters (dynamic compliance [Cdyn] and peak inspiratory pressure [PIP]) were studied in 12 patients. After cardiac surgery, they had impairment of oxygenation without physiological findings and with normal chest radiographs despite having a positive end expiratory pressure of up to 10 cm H2O. After 90 min of inhalation of He/O2, oxygenation had improved significantly; that is, PaO2/FidO2 increased significantly (from 113 to 174 mm Hg; mean values are given; p < 0.01), and there was a significant fall in Qs/Qt (from 29 to 19%; p < 0.001) together with an increase in Cdyn (from 60 ml/cm H2O to 64 ml/cm H2O; p < 0.05). These results suggest that He/O2 may have improved oxygenation by recruiting previously obstructed small airways and alveoli.

Administration, Inhalation↗
PubMedDate not supplied

An unusual cause of increasing airway pressure during anesthesia.

A mare with a thoracic laceration was anesthetized with halothane-O2 for surgical repair. Shortly after initiation of controlled ventilation, inspiratory plateau pressure began to increase. The increase in pressure continued despite decreasing the tidal volume. Tension pneumothorax was suspected, but because arterial PCO2 and PO2 were normal, the anesthetic apparatus was examined. Excess gas continued to exit through the bellows pop-off valve even when the fresh gas flow was turned off. It was determined that driving gas from the ventilator was entering the breathing circuit through a hole in the bellows. Testing the integrity of the bellows before use is suggested to avoid this potentially harmful complication.

Anesthesia, Closed-Circuit↗
PubMed2002

Alterations in pulmonary function in inflammatory bowel disease are frequent and persist during remission.

OBJECTIVES: Information on the occurrence and frequency of pulmonary involvement in patients with inflammatory bowel disease (IBD) is inconsistent. The aim of this prospective study was to determine the frequency and type of pulmonary dysfunction in patients with IBD. METHODS: Sixty-six patients with IBD (35 with Crohn's disease [CD] and 31 with ulcerative colitis [UC]) and 30 control patients were investigated with respect to the following pulmonary function tests: forced expiratory volume in 1 s (FEV1), inspiratory vital capacity (IVC), Tiffeneau value (FEV1/IVC), and lung CO transfer capacity (D(LCO)). Disease activity in IBD patients was assessed by the CD activity index for CD and the Truelove index for UC, respectively. Smoking habits and medication were documented in every patient. RESULTS: Fourteen of 36 CD patients (39%) and 14 of 31 UC patients (45%) but only one of the controls exhibited at least one pathological (<80% of predicted value) pulmonary function test. In both CD and UC lung function tests were significantly decreased in comparison to the control group. This could be shown for FEV1 (-14% of predicted value in CD and -17% in UC, p < 0.01), IVC (-10% in CD and -12% in UC, p < 0.05), and DLCO (-20% in CD and -31% in UC, p < 0.01) without significant differences between both disease entities. The impairment of pulmonary function tests was more pronounced in patients with active disease than in those with inactive disease (FEV1, 81.4% vs 93.4% predicted, p < 0.02; IVC, 84.4% vs 93.7%, p < 0.05; DLCO, 80.4% vs 95.8%, ns). CONCLUSIONS: IBD patients show significantly decreased lung function tests in comparison to healthy controls. The impairment in active disease exceeded that during remission.

Adult↗
PubMed1994

Effect of sustained inflations applied directly after cord clamping on lung function in premature newborn lambs.

We studied the possibility of improving lung volume and therefore clinical outcome in premature newborn lambs by increasing the inspiratory volumes during the first minute after birth. Sixteen lambs from eight were delivered by hysterotomy after 130-131 days' gestation. In eight lambs the lungs were inflated with a bag with a sustained inspiratory inflation (SI) of 5 s and expiratory time of 5 s during the first four inflations after cord clamping and then mechanically ventilated. Their siblings did not receive SI and served as a control group. At 8 h postnatally, the SI and control groups showed the following results (mean +/- SEM): mean airway pressure 14.8 +/- 1.8 cmH2O versus 11.9 +/- 1.1 cmH2O, PaO2 41.5 +/- 7.3 kPa versus 31.3 +/- 7.7 kPa, alveolar-arterial oxygen gradient 359 +/- 55 mmHg versus 437 +/- 58 mmHg. Clinical course, incidence of pneumothorax, oxygenation index, total static compliance, parenchymal-alveolar air area ratio or mortality rate were not different. There was no significant difference between the two groups at this time or at any other time during the experiments.

Animals↗
PubMed1976

Excitability changes of the inspiratory "off-switch" mechanism tested by electrical stimulation in nucleus parabrachialis in the cat.

The time course of the excitability of the inspiratory "off-switch" mechanism with and without phasic vagal stretch receptor feedback has been studied in cats under light pentobarbitone anesthesia by electrical stimulation in the rostral pons using brief tetanic stimulation (300 Hz for 0.2 s). The threshold strength required just to elicit inspiratory "off-switch" was high early in inspiration and fell steeply with time. The threshold curves were steeper with than without phasic vagal feedback, and the difference reflects the phasic vagal contribution to the excitability of the inspiratory "off-switch" the absence of phasic vagal vagal feedback the time course of this threshold curve usually corresponded closely to that of the "integrated" phrenic activity at all PCO2 levels and body temperatures tested indicating that the "integrated" phrenic activity can be used as an index of the centrally generated inspiratory activity. In response to a rise in PCO2 both the rate of change of excitability of the inspiratory "off-switch" mechanism and its initial threshold level was increased. Changes in body temperature caused no change in the initial threshold but produced marked changes in the rate of rise of the "off-switch" excitability; Following an "augmented breath" the inspiratory "off-switch" threshold was markedly reduced

Animals↗
PubMed1988

Effects of exercise and CO2 inhalation on the breathing pattern in man.

Conflicting opinions exist concerning the breathing pattern in man during resting and stimulated ventilation. Some but not all investigators have reported the existence of an abrupt change, a 'breakpoint', in the relation between mean tidal volume and mean inspiratory time. Different opinions exist as to whether the slope and the intercept for the relation between mean minute ventilation and mean tidal volume are identical regardless of the mode of stimulating the ventilation. We have studied 10 subjects, at rest and during graded stimulation of ventilation by CO2 inhalation and exercise. No breakpoint was observed in the relations between (1) mean tidal volume and mean inspiratory time and (2) mean tidal volume and mean expiratory time, even if a wide range of tidal volumes was achieved in our subjects. Carbon dioxide inhalation (normoxic or hyperoxic) and exercise gave different regression lines for the relation between mean minute ventilation and mean tidal volume in 8 out of 10 subjects with a larger slope during exercise. At exercise inspiratory time decreased with any increase in tidal volume, while during CO2 breathing no consistent change in inspiratory time was seen. Mean inspiratory flow was linearly related to exercise load and apparently also to arterial carbon dioxide pressure. We conclude that CO2 breathing gives a breathing pattern which is different from that obtained with exercise in the majority of normal subjects. Furthermore, we could not confirm the existence of breakpoints in relations describing the breathing pattern of normal man.

Adult↗
PubMed1980

Changes in the perception of inspiratory resistive loads during partial curarization.

1. The ability of normal subjects to estimate the magnitude of resistive loads and to detect resistive loads was determined using standard psychophysical techniques. The experiments were repeated during maintained partial neuromuscular blockade with D-tubocurarine. 2. During curarization the ability to detect the presence of a small inspiratory resistive load was not significantly impaired. This finding is consistent with the view that changes in the usual breath-by-breath relation between pressure and flow mediate detection. 3. The size of resistive loads was over-estimated during partial curarization. Subjects thus placed more reliance on sensing the increased motor command required during curarization than on alternative peripheral signals related to pressure, flow or resistance. 4. The exponent for the power function relating the perceived magnitude of a resistive load to its actual size (Stevens, 1957) was reduced during partial neuromuscular blockade. 5. These results suggest that detection of resistive loads depends upon sensing apparent information arising from an unexpected pressure-flow disturbance but that estimation of the size of an added load depends, in part, on sensing the outgoing motor command.

Adult↗
PubMed2005

Effect of inspiratory muscle work on peripheral fatigue of locomotor muscles in healthy humans.

The work of breathing required during maximal exercise compromises blood flow to limb locomotor muscles and reduces exercise performance. We asked if force output of the inspiratory muscles affected exercise-induced peripheral fatigue of locomotor muscles. Eight male cyclists exercised at > or = 90% peak O2 uptake to exhaustion (CTRL). On a separate occasion, subjects exercised for the same duration and power output as CTRL (13.2 +/- 0.9 min, 292 W), but force output of the inspiratory muscles was reduced (-56% versus CTRL) using a proportional assist ventilator (PAV). Subjects also exercised to exhaustion (7.9 +/- 0.6 min, 292 W) while force output of the inspiratory muscles was increased (+80%versus CTRL) via inspiratory resistive loads (IRLs), and again for the same duration and power output with breathing unimpeded (IRL-CTRL). Quadriceps twitch force (Q(tw)), in response to supramaximal paired magnetic stimuli of the femoral nerve (1-100 Hz), was assessed pre- and at 2.5 through to 70 min postexercise. Immediately after CTRL exercise, Q(tw) was reduced -28 +/- 5% below pre-exercise baseline and this reduction was attenuated following PAV exercise (-20 +/- 5%; P < 0.05). Conversely, increasing the force output of the inspiratory muscles (IRL) exacerbated exercise-induced quadriceps muscle fatigue (Q(tw) = -12 +/- 8% IRL-CTRL versus-20 +/- 7% IRL; P < 0.05). Repeat studies between days showed that the effects of exercise per se, and of superimposed inspiratory muscle loading on quadriceps fatigue were highly reproducible. In conclusion, peripheral fatigue of locomotor muscles resulting from high-intensity sustained exercise is, in part, due to the accompanying high levels of respiratory muscle work.

Adult↗
PubMed2002

Effect of posture on oxygenation and respiratory muscle strength in convalescent infants.

OBJECTIVE: To determine if differences in respiratory muscle strength could explain any posture related effects on oxygenation in convalescent neonates. METHODS: Infants were examined in three postures: supine, supine with head up tilt of 45 degrees, and prone. A subsequent study was performed to determine the influence of head position in the supine posture. In each posture/head position, oxygen saturation (SaO2) was determined and respiratory muscle strength assessed by measurement of the maximum inspiratory pressure (PIMAX). PATIENTS: Twenty infants, median gestational age 34.5 weeks (range 25-43), and 10 infants, median gestational age 33 weeks (range 30-36), were entered into the first and second study respectively. RESULTS: Oxygenation was higher in the prone and supine with 45 degrees head up tilt postures than in the supine posture (p<0.001), whereas PIMAX was higher in the supine and supine with head up tilt of 45 degrees postures than in the prone posture (p<0.001). Head position did not influence the effect of posture on PIMAX or oxygenation. CONCLUSION: Superior oxygenation in the prone posture in convalescent infants was not explained by greater respiratory muscle strength, as this was superior in the supine posture.

Female↗
PubMed1976

Dead space ventilation in normal children and children with obstructive airways diease.

Anatomical dead space was measured in 72 normal children aged from 5 to 16 years, using the single breath method. There was a linear increase in this measurement with height, weight, and end-inspiratory lung volume. Physiological dead space was measured in 52 normal children using the Bohr equation and substituting a rebreathing PCO2 for alveolar PCO2. There was a parallel increase in this measurement with height, weight, and end-inspiratory lung volume. The difference between the two dead space measurements constitutes the alveolar dead space and was constant over the whole age range at 45 +/- 22 ml. The ratio of physiological dead space to tidal volume was 33-6 +/-4-6% and was unaltered by age or change in lung volume. The effect of airways obstruction on the dead space volumes was studied in 36 children with asthma and 28 with cystic fibrosis. Physiological dead space increased with increasing airways obstruction. Anatomical dead space remained constant in spite of marked increases in lung volume associated with the airways obstruction.

Adolescent↗