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PubMed1979

Density dependence of the maximal expiratory flow volume curves in normal and asthmatic children.

We have studied the maximal expiratory flow volume curves with air and with an 80% helium-oxygen mixture, using 12 normal and 33 asthmatic children chosen according to clinical, functional and immunological criteria. In the normal children, the average delta Vmax (difference between the maximal flow in HeO2 and in air at corresponding lung volumes) was 49% and was similar from 60% to 20% of vital capacity. The iso flow volume (lung volume level at which the HeO2 and air flow volume curves intersect) was 3% of vital capacity. Eleven of the asthmatics were non-responders to the helium mixture (no significant differences in flow between HeO2 and air curves), five at 50% and 25% VC and six at only 25% VC. The other 22 asthmatics were responders, but nine of them showed a rise of the iso flow volume. Eight subjects showed no obstruction according to the flow volume curves in air; three of these had an abnormal response to the helium mixture. All the non-responders at 50% VC and half of the non-responders at 25% VC had a clinical history of recurrent infections. These results suggest, firstly, that when there is no history of recurrent infections, the site of obstruction in asthmatic children is mainly central. This does not exclude a coexisting peripheral obstruction which could persist after recovery of the central component. Secondly, by studying the HeO2 response at 25% VC, we can get more information than by measuring only the delta Vmax50 or iso flow volumes.

Adolescent↗
PubMedDate not supplied

Disturbances in pulmonary mechanics during serotonin perfusion.

The effect of i.v. perfused serotonin (75 microgram.kg-1.min-1) on bronchomotor tone was assessed in dogs by mechanical studies, with the result in an increase in total lung resistance. The increased residual volume (RV), closing capacity (CC) and slope of phase III (nitrogen single-breath washout) as well as the reduction of the helium response at low lung volumes suggest a peripheral action of the drug. Because of the large increase in total lung resistance and the decreased dead space (VD), bronchoconstriction of large airways must also be present. Vagal tone inhibition is incomplete whether by volume history or bilateral vagotomy and could be limited mainly to a segment which is situated between the equal pressure point and the most peripheral airways: maximal flows during partial expiratory flow-volume manoeuvres (PEFV) are lower than during maximal expiratory flow-volume manoeuvres (MEFV) and the volume of isoflow is higher in PEFV than in MEFV manoeuvers, suggesting that full inspiration reduces the bronchoconstriction induced by serotonin. On the other hand, the bilateral vagotomy did not reverse CC, RV, slope of phase III or VD back to control values. Isoproterenol i.v. injection improved all physiological measurements almost to the level of control values: beta-adrenergic stimulating drugs seem to inhibit completely serotonin induced bronchospasm, at all levels of the bronchial tree.

Airway Resistance↗
PubMed1979

[Interest of helium-oxygen flow volume and isoflow volume curves in chronic obstructive lung disease (author's transl)].

We have compared changes in maximal flows induced by breathing gases of different density in 54 patients suffering from emphysema and chronic bronchitis. We considered as positive responders those subjects displaying an increase by at least 20% of maximal expiratory flows while breathing gases of lower density. Such a response was demonstrated in 21 cases, the remainder (33 cases) being non-responders. Hence, in such patients, airways obstruction may primarily be localised in central or peripheral airways. There was no correlation between the nature of this response and the clinical diagnosis, but non-responders, in general, were those in whom respiratory insufficiency was more severe. There seemed to be no additional information gained by measuring isoflow-volume (iso V vol.) in comparison with measuring differences in maximal flows at 50% of vital capacity.

Bronchitis↗
PubMed1978

Maximum expiratory flow and transpulmonary pressure in the hamster.

Maximum expiratory flow was measured in 19 normal, anesthetized, tracheostomized, supine hamsters from records of forced deflation produced by the application of varying degrees of negative pressure to the tracheostomies of animals whose lungs had been previously inflated to a transpulmonary pressure (PL) of 25 cmH2O. Flow was measured with a pneumotachograph, volume with a constant-volume pressure plethysmograph and pleural surface pressure (Ppl) with a water-filled esophageal catheter. The esophageal pressure measurement overestimated Ppl and a simple technique was based on an estimate of the resting volume of the chest wall. This volume, at which the Ppl is zero, was calculated for anesthetized supine hamsters from the measurement of respiratory-system pressure and PL made independently of esophageal pressure and was found to be about 30% of vital capacity (VC). Flow limitation was present below 70% of VC with a tracheal deflation pressure of -30cmH2O. Negative effort dependence of flow was seen in small segments of the flow-volume curves. Mean +/- SD maximum expiratory flow at 50% VC was 52 +/- 9.5 ml/s or 9.1 VC/s. Upstream resistance was 0.09 +/- 0.03 cmH2O/ml per s.

Airway Resistance↗
PubMed1978

Indications for pulmonary function testing.

Pulmonary function testing is needed to determine the pathophysiology present in the patient with cardiopulmonary disease. Blood gases and pH should be obtained during emergency situations and during cranial, thoracic, and extensive cervical or abdominal surgery. Lung function tests can be divided in global such as spirometry and diffusing capacity which study the ventilation and transfer of gases and regional determinations of ventilation and perfusion. Both types of tests complement each other and should be used together. The spirometry should consist at least of determination of the vital capacity and is determined in the first second to ascertain if there is obstructive lung disease. Some tests such as flow-volume curves, alveolar-arterial gradients and closing volume are very useful to detect early pulmonary disease before any symptoms or findings are present. This is probably one of the most important medical indications for pulmonary function testing. Before certain types of surgery pulmonary function testing is indicated; if the spirometry and diffusing capacity tests are normal, there is no pulmonary contraindication for the planned surgery. In chest surgery if there is significant compromise of the spirometry and diffusing capacity regional lung function tests are indicated to study the pathophysiology at regional level, thus trying to circumscribe the lung resection to the diseased areas.

Blood Gas Analysis↗