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PubMed1983

[Stimulation of limited sperm motility and mucociliary clearance of the lung with theophyllin-ethylendiamin].

The influence of oral aminophylline (Phyllotemp ret., 2 X 225 mg) on the mucociliary clearance of the lung and on sperm motility was examined in 13 patients with asthenospermia vs. placebo because the anatomic structure of the cilia of the sperm cells and of the respiratory epithelium cells is similar. The mucociliary clearance was measured by means of radioactive tagged (99 mTc) monodisperse particles (erythrocytes from the patients). To attain a reproducible deposition pattern, the particles were inhaled during a slow inspiratory vital capacity maneuvre. The i.v. application of aminophylline (6 mg/kg body weight) to four normal subjects increased the mucociliary clearance in three of the four volunteers vs. placebo. The elimination rate of the particles increased under treatment with aminophylline from 29% +/- 12% to 46% +/- 19%, but only in seven of the 13 patients with asthenospermia. Sperm motility increased in all of the patients from 33% +/- 12% to 54% +/- 14%. No correlation was found between the increase in the mucociliary clearance and the sperm motility. The reasons for this difference will be discussed. Theophylline can be recommended for the treatment of male infertility in cases of asthenospermia.

Aminophylline↗
PubMed1992

Evaluation of indexes predicting the outcome of ventilator weaning and value of adding supplemental inspiratory load.

OBJECTIVE: To assess the diagnostic accuracy of several measured and calculated indexes for early prediction of weaning outcome, and to study the value of supplemental inspiratory load in improving the accurate prediction of successful weaning. DESIGN: Prospective study. SETTING: ICU of a University Hospital. PATIENTS: Thirty consecutive patients under prolonged mechanical ventilation and without chronic obstructive pulmonary disease (COPD). INTERVENTIONS: Forty weaning trials were performed. Data were recorded at 15, 30 (adding inspiratory flow resistance), 60 and 120 min. MEASUREMENTS AND MAIN RESULTS: The threshold values and the accuracy of three indexes were determined: Inspiratory airway occlusion pressure at 0.1 sec. (P01) to maximum inspiratory pressure ratio (P01/MIP), inspiratory effort quotient (IEQ), and the ratio of respiratory frequency to tidal volume (F/Vt). All three were useful predictors for weaning success with a diagnostic accuracy between 82%-87%. At 15 min of spontaneous breathing, a P01/MIP ratio < 0.14 predicts weaning success with a sensitivity of 82% and specificity of 83%. In our group of patients no reintubation was necessary. The application of mechanical inspiratory load significantly increased P01 values (3.16 +/- 1.22 to 3.60 +/- 1.19, p < 0.001). The degree of the P01 increase did not provide prediction of weaning outcome. CONCLUSIONS: a) P01/MIP, IEQ and F/Vt ratio were accurate, early predictors of weaning outcome. b) The addition of a moderate mechanical inspiratory load did not enhance the diagnostic accuracy of P01 measurements. c) In our patients, a period of two hours seemed to be sufficient for development and detection of weaning failure.

Adult↗
PubMed1993

Inspiratory pressure/maximal inspiratory pressure ratio: a predictive index of weaning outcome.

OBJECTIVE: To compare the accuracy of PI/PImax ratio and other commonly used indices in predicting weaning outcome. DESIGN: A prospective study. SETTING: Intensive care unit. PATIENTS: 31 stable intubated patients ready to undergo weaning trial. METHODS: A simple method was developed to measure the PI and PImax in intubated patients. The accuracy of PI/PImax ratio and other commonly used indices in predicting outcome were compared. All indices were measured prior to weaning trial using standardized methods. MEASUREMENTS AND RESULTS: Minute ventilation of the successful patients (13.00 +/- 0.67 (SE) l/min) was not significantly different from the failure patients (10.64 +/- 1.26 l/min, p = 0.10). The PI and PImax for the successful patients (11.48 +/- 1.25 cmH2O and 47.77 +/- 4.48 cmH2O, respectively) and the unsuccessful patients (14.32 +/- 2.31 cmH2O and 40.16 +/- 4.55 cmH2O, respectively) were also not significantly different (p = 0.28 and 0.24, respectively). The PI/PImax ratio was lower for the weaning successes (0.26 +/- 0.03) than for the weaning failures (0.36 +/- 0.04, p < 0.05). The threshold value of 0.3 for PI/PImax provided the best separation between weaning success and failure patients. The combined usage of rapid shallow breathing index and PI/PImax ratio provided the highest accuracy with sensitivity of 0.81 and specificity of 0.93. CONCLUSION: The PI/PImax ratio provided a good separation between the patients who were successfully weaned and those who failed. It provides additional discriminative power to f/VT.

Aged↗
PubMed1992

Inspiratory work imposed by continuous positive airway pressure (CPAP) machines: the effect of CPAP level and endotracheal tube size.

Inspiratory work imposed by Continuous Positive Airway Pressure (CPAP) machines has been a matter of concern. The imposed inspiratory work of CPAP machine circuits (Wcir) and the effect of the total breathing apparatus with endotracheal tube (ETT) and connector included in the circuit (Wapp), were measured in three continuous flow (CF) and various configurations of three demand flow (DF) CPAP machines. The performance was assessed at 0, 5, 10 and 15 cmH2O CPAP using a Michigan Instruments Test Lung Model 1600, internal compliance set at 50 ml/cmH2O, driven at square wave inspiratory flows (VI) of 20, 40 and 60 l/min at a tidal volume of 500 ml. Work, expressed in mJ/l, was calculated from the area of pressure-volume loops. Inspiratory work, Wcir and Wapp, was dependent upon the particular CPAP machine, VI and ETT size, but not upon CPAP level, being maximum at VI 601/min and with ETT 7.0 mm i.d. Work values (Wcir) varied from 50 to 325 mJ/l with both CF and DF machines and up to 1100 mJ/l with ETT and connector (Wapp). No consistent advantage of CF over DF machines was demonstrated. There was little advantage of high gas flows (greater than 5 l/min) in various DF circuits. Within an individual machine maximum negative pressures generated during inspiration correlated with both Wcir and Wapp.

Equipment Design↗
PubMed1996

Physiological effects of reduced tidal volume at constant minute ventilation and inspiratory flow rate in acute respiratory distress syndrome.

OBJECTIVE: To assess the effect of changes in tidal volume (VT) with a constant inspiratory flow and minute ventilation (VE) on gas exchange and oxygen transport in acute respiratory distress syndrome (ARDS). DESIGN: A crossover study of three VT in two study groups, using patients as their own controls. SETTING: A medical-surgical intensive care unit in a tertiary care center. PATIENTS: Eight patients with ARDS and seven postoperative cardiac surgery patients with uncomplicated recoveries were studied during volume-controlled mechanical ventilation. INTERVENTIONS: During controlled mechanical ventilation, patients were first ventilated with a VT of 9-11 ml/kg. VT was then increased to 12-14 ml/kg (+ 25%) for 30 min and subsequently decreased to 6-8 ml/kg (- 25%) for 30 min by adjusting the respiratory rate (RR) while the inspiratory flow rate, VE, and inspiratory duty cycle (TL/T(TOT)) were kept constant. At the end, patients were ventilated with the baseline settings for another 30 min. MEASUREMENTS AND RESULTS: VE, carbon dioxide production (VCO2) and oxygen consumption (VO2) were measured continuously with a gas exchange monitor, and cardiac output and arterial and mixed venous blood samples were taken at the end of each 30-min period to assess CO2 removal and oxygen transport. Alveolar minute ventilation (VA) and the deadspace to tidal volume ratio (VD/VT) were calculated from the Bohr equation. Despite large changes in VT, arterial oxygenation (PaO2) and oxygen transport (DO2) were unchanged throughout the study. When VT was increased, physiological VD increased from 448 +/- 34 ml to 559 +/- 46 ml (mean +/- SE) in ARDS (P < 0.001) and from 281 +/- 22 ml to 357 +/- 35 ml in CABG (P < 0.05). With the small VT, VD decreased to 357 +/- 22 ml in ARDS (P < 0.01), and to 234 +/- 24 ml in CABG (P < 0.05). In ARDS, VD/VT decreased from 0.57 +/- 0.03 to 0.55 +/- 0.03 (P < 0.05) with the large VT, and increased to 0.60 +/- 0.03 (P < 0.01), when VT was reduced. In CABG, VD/VT did not change significantly. ARDS patients had a higher PaCO2 than cardiac patients (P < 0.001), and only minor changes in PaCO2 were observed (for ARDS and CABG respectively, baseline 5.9 +/- 0.3 kPa and 4.1 +/- 0.1 kPa, large VT 5.7 +/- 0.3 kPa and 4.1 +/- 0.2 kPa, small VT 6.2 +/- 0.3 kPa and 4.2 +/- 0.2 kPa; P < 0.05). CONCLUSIONS: Tidal volumes can be reduced to 6-8 ml/kg in ARDS patients without compromising oxygen transport, while adequate CO2 elimination can be maintained.

Adult↗
PubMed1996

Inspiratory pressure/maximal inspiratory pressure: does it predict successful extubation in critically ill infants and children?

OBJECTIVE: To evaluate the accuracy of the initial negative inspiratory pressure (PI) to maximal negative inspiratory pressure (PImax) ratio in predicting extubation outcome for intubated infants and children. DESIGN: A prospective study. SETTING: Pediatric intensive care unit. PATIENTS: A sample of 50 stable intubated pediatric patients who were judged clinically ready for extubation. METHODS: Using a one-way valve, PI and PImax were measured in all patients, after which the < or = ratio PI/PImax was calculated and its accuracy in predicting extubation outcome evaluated. MEASUREMENTS AND RESULTS: A total of 39 patients (78%) were successfully extubated and 11 patients (22%) were not. The mean PI/PImax ratio was not significantly different between extubation successes (0.36 +/- 0.14) and failures (0.45 +/- 0.1) (P > 0.05). The cut-off value of 0.3 for PI/PImax identified in adult patients did not discriminate between extubation success and failure in children. Furthermore, a discriminatory cut-off value other than 0.3 could not be identified for infants and children. CONCLUSION: The PI/PImax ratio cannot be used to predict extubation outcome in pediatric patients. Indices that predict extubation outcome in adults should not be extrapolated to infants and children before testing and validation.

Adolescent↗
PubMed1990

Risk factors for fatal pulmonary interstitial emphysema in neonates.

Among 315 infants treated for respiratory distress syndrome (RDS) over a 2 year period, 32 prematures were studied retrospectively with the diagnosis of pulmonary interstitial emphysema (PIE). Eighteen died. In this group, birth weight below 1600 g, need for oxygen above 0.6 on the 1st day and appearance of bilateral pulmonary interstitial emphysema within the first 48 h of life were significant risk factors, with a mortality rate of 94%. In order to recognize one or more early criteria predictive of fatal PIE, we compared ventilation parameters on day 1 between neonates with fatal PIE and those with the same birth weight and initial severity of RDS but without PIE treated during the same period. High positive inspiratory pressure on day 1 was found to be the most significant parameter associated with further appearance of fatal pulmonary interstitial emphysema. A cut-off level of 26 cm H2O was found to be discriminant. These criteria may be useful in selecting those neonates who might best benefit from a new therapy such as high frequency ventilation, before irreversible lesions appear.

Birth Weight↗
PubMed1996

Ventilatory and metabolic responses of a bat, Phyllostomus discolor, to hypoxia and CO2: implications for the allometry of respiratory control.

The ventilatory and metabolic responses of lesser spear-nosed bats to hypoxia and hypercapnia were measured to determine whether these corresponded to preliminary allometries and a positive relationship between hypoxic ventilatory threshold and P50. Ventilatory responses of lesser spear-nosed bats to 3, 5 and 7% CO2 differed significantly from ventilation on air and each other. The magnitude of their ventilatory response to CO2 is consistent with the prediction of a smaller ventilatory response to hypercapnia in small compared to large mammals [% delta V varies MB0.130; Williams et al. (1994)]. Among 12, 10 and 8% O2 treatments only the ventilatory response to 8% O2 differed significantly from ventilation on air or the other treatments. Metabolic rate was significantly reduced at both 10 and 8% O2. The hypoxic ventilatory response of these bats does not support the prediction of a greater response in small compared to large mammals [% delta V veries MB0.273; Boggs and Tenney (1984)]. Their metabolic response is consistent with the hypoxic hypometabolism typical of small mammals, though not of comparable magnitude. The response, expressed as percent change in convection requirement (V/VO2), is also less than that observed in other small mammals. This relative insensitivity to hypoxia may be associated with this bat's unusually high affinity hemoglobin (P50 = 27.5 torr).

Anaerobiosis↗
PubMed1990

Optimum stimulus frequency for contracting the inspiratory muscles with chest-surface electrodes to produce artificial respiration.

Electroventilation is the term used to describe the production of inspiration by applying a train of short-duration pulses to chest-surface electrodes. Studies were conducted in the dog to determine the optimum frequency to produce a smooth air flow in the trachea. It was found that a stimulus frequency of 25/sec or slightly higher meets this criterion. To illustrate that electroventilation can be carried out for a prolonged period using these parameters, electroventilation was applied continuously for 5 hours in a dog without a noticeable change in blood pressure.

Animals↗
PubMed1987

Effect of posture on ventilation and breathing pattern during room air breathing at rest.

We measured minute ventilation (VE), tidal volume (VT), mean inspiratory flow (VT/TI), and occlusion pressure (P.1) in 10 resting subjects breathing room air, in sitting, supine, right and left lateral positions, and compared them with corresponding data on static lung compliance [Cst(l)], dynamic lung compliance [Cdyn(l)], and pulmonary flow resistance [R(l)]. Highest values for VT, VE, VT/TI, P.1, and effective inspiratory impedance [P.1/(VT/Ti)] were observed in the supine posture. Values for P.1 and P.1/(VT/TI in lateral decubitus were intermediate to those obtained when seated and supine. While the increases in P.1 and P.1/(VT/TI) in recumbent postures were qualitatively similar to the decrease in Cdyn(l) and increase in R(l), there was no significant correlation between them, probably reflecting the complex relationship between P.1/(VT/TI) and lung compliance and resistance, as the former, in addition to lung mechanics, also depends on the shape of the inspiratory driving pressure wave, the active inspiratory impedance, the mechanics of the chest wall, and the duration of inspiration.

Adult↗
PubMed1989

Control of breathing in patients with short-term primary hypothyroidism.

In 8 patients (3 men and 5 women) with short-term primary hypothyroidism before and during replacement therapy, and in an age-matched control group (9 men and 7 women), we assessed maximal inspiratory muscle force (Pimax) and the ventilatory control system at neural (EMG), muscular (P0.1), and ventilatory (VE and Vt/Ti) levels. While hypothyroid, patients exhibited a significantly lower Pimax. During a CO2 rebreathing test, hypothyroid patients exhibited similar diaphragmatic electromyographic (EMGd) and ventilatory (VE) response slopes to increasing end-tidal CO2 tension (delta EMGd/delta Pet CO2 and delta VE/delta PetCO2), but significantly less delta P0.1/delta PetCO2 (p less than 0.05) and delta(Vt/Ti)/delta PetCO2 (p less than 0.05) response slopes. During replacement therapy with L-triiodothyronine (L-T3), Pimax (p less than 0.05), delta P0.1/delta PetCO2, and delta(Vt/Ti)/delta PetCO2 response slopes were found to be significantly increased (p less than 0.05 for both) while neither EMGd nor VE response changed significantly. We concluded that short-term hypothyroidism does not seem to be associated with blunted neural inspiratory output (EMGd), the respiratory control system seems to be affected mostly at a peripheral (muscular) level, and L-T3 increases both force (P0.1 and Pimax) and velocity (Vt/Ti) of inspiratory muscle contraction.

Adult↗
PubMed1989

Lung function, maximum and submaximum exercise testing in COPD patients: reproducibility over a long interval.

This study was designed to investigate the reproducibility and clinical relevance of several lung function and exercise test indices in a sample of patients with stable severe chronic obstructive pulmonary disease (COPD). Twenty subjects (ages 67.8 +/- 2.0 years, forced expiratory volume in 1s, [FEV1] 39.7 +/- 2.8% predicted) receiving conventional medical therapy and pulmonary rehabilitation were tested 4 times at 1 month intervals. Testing procedures included lung function (inspiratory vital capacity [IVC], FEV1, plethysmographic functional residual capacity [FRC], specific conductance of the airways (sGaw), single breath transfer factor divided by the alveolar volume [TL/VA]); incremental, progressive, symptom-limited, cycle exercise (maximum work load [Wmax], maximum heart rate [HRmax], maximum ventilation [VEmax], maximum oxygen uptake [VO2max]); and 2 modes of submaximum exercise (12 min walking test [12 MWD] and endurance cycle test). The mean of the absolute value of the individual patient, session-to-session, variation was found to be 0.131 for FEV1, 102 ml/min for VO2max. The within-subject variability was the smallest for HRmax and IVC (mean intrasubject coefficient of variation, [CV intra] 5.0 and 6.5%) and the greatest for TL/VA, the work performed during the endurance cycle test (EW) and sGaw (CV intra 16.5, 19.4, and 22.7%), while it was reasonably low (8.1-10.2%) for all the other variables studied. Calculation of the F ratio of the intersubject variance to the residual (total minus intersubject) variance, interpreted as a signal-to-noise, ratio, yielded the following, in decreasing order: TL/VA, EW, VEmax, VO2max, IVC, FEV1, HRmax, Wmax, sGaw, 12 MWD, FRC. If we assume that a useful variable should combine a low within-subject variability (CV intra less than or equal to 10%) with a high signal-to-noise ratio, we conclude that, among all the variables studied, IVC, FEV1, VEmax, and VO2max are those with the greatest clinical potential for functional assessment in patients with COPD.

Aged↗
PubMed1979

Effect of doxapram on control of breathing in cats.

The effects of doxapram infusion (0.25 mg.kg-1. min-1) were studied in cats anaesthetized with pentobarbitone (35 mg . kg-1 intraperitoneally). Cats were studied breathing 50 per cent oxygen and the responses to two concentrations of inspired carbon dioxide were measured. Doxapram infusion increased pulmonary ventilation by increasing both tidal volume and respiratory frequency, and also caused increases in the volume inspired in the first 0.5 second after the onset of an inspiration (V0.5) and the pressure generated in the airway 0.5 second after the onset of an inspiration when the airway had been occluded (P degrees 0.5). V 0.5, P degrees 0.5 and the mean inspiratory flow rate (VT/VI) were essentially equivalent indices of inspiratory drive. Doxapram infusion did not alter the effective impedance of the respiratory system (P degrees 0.5/V 0.5). Doxapram infusion increased the ventilatory response to carbon dioxide. The slope of the ventilatory response to carbon dioxide was increased and the response line was shifted to the left. We conclude that the increase in pulmonary ventilation caused by doxapram infusion is due almost entirely to increased inspiratory neuromuscular drive (P degrees 0.5).

Animals↗
PubMed1992

Pressure controlled-inverse ratio ventilation and pulmonary gas exchange during lower abdominal surgery.

Although pressure controlled-inverse ratio ventilation (PC-IRV) has been used successfully in the treatment of respiratory failure, it has not been applied to the treatment of respiratory dysfunction during anaesthesia. With PC-IRV the inspiratory wave form is fundamentally altered so that inspiratory time is prolonged (inverse I:E), inspiratory flow rate is low, and the peak inspiratory pressure is limited. Positive end-expiratory pressure (PEEP) can be applied and the mean airway pressure is higher than with conventional ventilation. To assess the clinical efficacy of this new mode of ventilation we studied ten patients having lower abdominal gynaecologic surgery in the Trendelenburg position under general anaesthesia. Pulmonary O2 exchange was determined during four steady states: awake control (AC), after 30 and 60 min of PC-IRV during surgery, and at the end of surgery. Patients' lungs were ventilated with air/O2 by a Siemens 900C servo ventilator in the PC-IRV mode with an I:E ratio of 2:1 and 5 cm H2O of PEEP. The FIO2 was controlled at 0.5 and arterial blood gases were used to calculate the oxygen tension-based indices of gas exchange. There were significant increases of (A-a) DO2 at 30 and 60 min (41 and 43%). These changes were less than those reported in a previous study using conventional tidal volume ventilation (7.5 ml.kg-1) and were similar to those in patients whose lungs were ventilated with high tidal volumes (12.7 ml.kg-1). Thus, in this clinical model of compromised gas exchange, arterial oxygenation was better with PC-IRV than with conventional ventilation, but not better than with large tidal volume ventilation.

Abdomen↗
PubMed1998

Respiratory compliance during laparoscopic hiatal and inguinal hernia repair.

PURPOSE: Side stream spirometry with dynamic compliance displayed as pressure-volume loops, has enabled early detection of CO2 pneumothorax during pneumoperitoneum. We compared dynamic compliance profiles of two laparoscopic procedures with different patient positions. METHODS: In 26 patients, scheduled either for laparoscopic fundoplication in a head-up tilt or inguinal herniorrhaphy in a head-down tilt, dynamic compliance was measured with continuous spirometry from anaesthesia induction until skin closure. Control pressure-volume loops were saved in the horizontal position before surgery and compared with succeeding loops in the head-up/head-down tilt before pneumoperitoneum, during pneumoperitoneum in the horizontal and the tilt position, after evacuation of pneumoperitoneum in the tilt and finally in the horizontal position. RESULTS: Pneumoperitoneum reduced compliance in both groups by 35% (P < 0.01). Head-down tilt decreased compliance by 12% before and during pneumoperitoneum (P < 0.01). Head-up tilt increased compliance by 4% before pneumoperitoneum (P < 0.05), but during pneumoperitoneum it had no effect. After evacuation of pneumoperitoneum compliance returned immediately to control in head-up tilt, but remained reduced in head-down tilt and was not at control after adopting horizontal position (P < 0.05). Difference between the groups was significant (P < 0.01) in the head-up/head-down tilt before, during and immediately after pneumoperitoneum. CONCLUSION: Both pneumoperitoneum and head-up and head-down positions had characteristic effects on dynamic compliance. Simultaneous display of sequential pressure-volume loops enabled immediate detection of changes in respiratory mechanics.

Adolescent↗