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PubMed1989

Inspired oxygen concentration during general anaesthesia for caesarean section.

The effects on maternal oxygen saturation, foetal wellbeing and umbilical blood gases were compared when parturients received either 30 or 50% oxygen prior to delivery by Caesarean section under general anaesthesia. Maternal arterial oxygen saturation was significantly increased in the group receiving 50% oxygen. There was no difference between the two groups in terms of Apgar score minus colour, time to sustained respiration or umbilical cord blood gas estimations. The use of 30% inspired oxygen during uncomplicated Caesarean section is advocated.

Adult↗
PubMed1989

Relationship between the perception of breathlessness and inspiratory resistive loading: report on a clinical trial.

We investigated the relationship between the sensation of breathlessness and progressively higher resistive inspiratory loadings in nine normal subjects (31 +/- 17 yr; forced expiratory volume in one second (FEV1) = 105 +/- 9% of predicted) and in eighteen chronic obstructive pulmonary disease (COPD) patients (63 +/- 7 yr; FEV1 = 43 +/- 17% of predicted). The sensation of breathlessness correlated with mouth pressure both in normals (r = 0.94) and in COPD patients (r = 0.95), with a steeper slope in patients. On this basis we studied the effect of inspiratory muscle training on the sensation of breathlessness in sixteen COPD patients (63 +/- 8 yr; FEV1 = 52 +/- 19% of predicted). After a baseline assessment of lung function, MIP (maximal inspiratory pressure), inspiratory muscle endurance and the sensation of breathlessness (Borg scale) at different inspiratory loads, the patients were divided into two groups: the first was trained by means of resistive breathing, the second used a placebo device. At the end of the training, MIP increased more in the trained group (56 +/- 10 to 69 +/- 15 cmH2O; p less than 0.001) than in the placebo group (50 +/- 17 to 56 +/- 22 cmH2O; p = NS). The Borg score fell significantly at all the considered inspiratory loads in trained patients, but not in the placebo group. We conclude that the training with inspiratory resistances decreased the sensation of breathlessness via an increase in inspiratory muscle strength and endurance.

Adult↗
PubMed1988

Ventilatory responses to hypercapnia during bupivacaine spinal anesthesia.

The effect of spinal anesthesia with isobaric 0.5% bupivacaine on ventilatory responsiveness to CO2 rebreathing was studied in ten unpremedicated patients. Minute ventilation (VE) at end-tidal PCO2 = 55 mm Hg increased from 18.7 +/- 6.7 L/min (mean +/- SD) to 22.3 +/- 10.1 L/min after induction of spinal anesthesia (P less than 0.05). Occlusion pressure (P0.1) at PCO2 = 55 mm Hg also increased, from 3.8 +/- 1.5 to 5.0 +/- 1.7 cm H2O (P less than 0.05). Spinal anesthesia was not associated with significant changes in vital capacity, maximal inspiratory pressure, resting end-tidal PCO2, or the slopes or intercepts of the lines relating VE or P0.1 to PCO2. These results show an increased ventilatory responsiveness to CO2 with bupivacaine spinal anesthesia.

Adult↗
PubMed1988

Inhalation rate of sodium cromoglycate determines plasma pharmacokinetics and protection against AMP-induced bronchoconstriction in asthma.

We have investigated whether the inspiratory flow at which sodium cromoglycate (SCG) is inhaled influences the efficacy of SCG. Seven atopic asthmatic subjects (age 25 +/- 2 yrs) inhaled dry powder SCG from a Spinhaler on separate occasions at three flow rates, maximum (V1), 100 l.min-1 (V2), and 50 l.min-1 (V3), or placebo, according to a double-blind structured study. Thirty minutes after administration a bronchial provocation test was performed with adenosine 5'-monophosphate (AMP). Blood samples for measurement of plasma SCG concentration were taken and the area under the plasma concentration-time curve (AUC) calculated for each flow rate. Both inspiratory flow rate and AUC correlated significantly with the degree of protection afforded against AMP-induced bronchoconstriction (r = 0.73, p less than 0.001; r = 0.66, p less than 0.001). These findings indicate that the flow rate used to inhale powdered SCG is a major factor in determining the protective efficacy of this drug against bronchial challenge and therefore has important clinical implications.

Adenosine Monophosphate↗
PubMed1986

[Aerodynamic studies of the upper respiratory tract].

The usefulness of flow-volume curves for the assessment of upper airway function is emphasized. The different behaviour of intra- and extra-thoracic airways, submitted to different transmural pressures, results in the reduction of maximum expiratory flows in cases of variable intrathoracic airways stenosis, whereas in the presence of an extrathoracic stenosis, the inspiratory maximum flows are mainly affected. Sleep apnea syndrome and "asthma-like" syndromes with a glottic origin are further examples of the potentials of flow-volume loops in the assessment of upper airway function.

Asthma↗
PubMed1985

[Analysis of the dependence of respiratory data during spontaneous ventilation at rest].

Inspiratory duration (TI), cycle duration (TTOT), and tidal volume (VT) were continuously measured in 11 normal subjects during 400 respiratory cycles. Small breath to breath changes in these variables were separately analyzed. For each of these variables, successive observations are not statistically independent; "large" values tend to be followed by "large" values. A respiratory feedback may be involved in this sequential dependence. In that case, any known system of respiratory control could be associated with it, even those with time constant or delay longer than one cycle duration.

Adolescent↗
PubMed1985

[Theoretical bases in the treatment of chronic obstructive bronchopneumopathies].

The natural history and pathophysiology of chronic airflow obstruction (BPCO) remain poorly understood. Therapy cannot cure the disease but should be aimed at palliating its effects: to reduce dyspnoea, to improve the exercise performance, to minimise the complications, to stabilise the disease and improve the quality of life, to prevent by combatting those factors which favour the development of the disease e.g. pollutants, tobacco, infections etc. The pre-requisite of any therapeutic action should be to recognise those factors which contribute to the pathology and the compensatory phenomena with which the organ opposes them. According to whether the compensation is insufficient or inappropriate the therapy should be either increased or designed to combat it. The therapeutic perspective demands a better understanding of the relationship between the respiratory centre and effector muscles on the one hand and the relationship between ventilation and pulmonary perfusion on the other.

Bronchi↗
PubMed1985

[Reproducibility of the flow-volume indices of healthy persons and patients with lung diseases].

Reproducibility of the flow-volume indicators at forced expiration and inspiration was calculated during examination of 210 healthy subjects and 420 patients with different pulmonary diseases. Reproducibility of the flow-volume indicators of the median and end part of the forced expiration which reflect largely the function proper of the patency of the distal parts of the bronchial tree was essentially higher in patients and tended toward increase with a rise in the degree of ventilation abnormalities. Reproducibility of the conventional spirographic parameters in healthy subjects and patients with ERF abnormalities did not differ whatever their character and degree.

Adult↗
PubMed1984

Using conventional infant ventilators at unconventional rates.

The effect of progressive increases in ventilator rate on delivered tidal and minute volumes, and the effect of changing peak inspiratory pressure (Pmax), positive end-expiratory pressure (PEEP), and inspiration to expiration (I:E) ratio at different ventilator rates were examined. Five different continuous-flow, time-cycled, pressure-preset infant ventilators were studied using a pneumotachograph, an airway pressure monitor, and a lung simulator. As rates increased from 10 to 150 breaths per minute, tidal volume stayed constant until 25 to 30 breaths per minute; then progressively decreased. In all, tidal volume began to decrease when proximal airway pressure waves lost inspiratory pressure plateaus. As rates increased, minute volume increased until 75 breaths per minute, then leveled off, then decreased. Substituting helium for O2 increased the ventilator rate at which this minute volume plateau effect occurred. Increasing peak inspiratory pressure consistently increased tidal volume. Increasing positive end-expiratory pressure decreased tidal volume. At rates less than 75 breaths per minute, inspiratory time (inspiration to expiration ratio) had little effect on delivered volume. At rates greater than 75 breaths per minute, inspiratory time became an important determinant of minute volume. For any given combination of lung compliance and airway resistance: there is a maximum ventilator rate beyond which tidal volume progressively decreases and another maximum ventilator rate beyond which minute volume progressively decreases; at slower rates, delivered volumes are determined primarily by changes in proximal airway pressures; at very rapid rates, inspiratory time becomes a key determinant of delivered volume.

Humans↗