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PubMed1977

Further studies of rimiterol and salbutamol administered by intermittent positive-pressure ventilation, and an important observation on the technique of using the Bennett ventilator.

1. Using the same technique of administering drugs by intermittent positive-pressure ventilation as used in previous studies a source of contamination of solutions nebulized was discovered. This was rectified by using a new ventilator and completely separate patient circuits for each solution nebulized. 2 Salbutamol 0.5% and 0.25% solutions achieved the same degree of bronchodilatation, but there was a significantly greater increase in heart rate produced by salbutamol 0.5%. 3 Rimiterol 0.5% and salbutamol 0.25% produced similar peak mean improvements in FEV and also induced the same degree of tachycardia, but the duration of these effects were significantly shorter in the case of rimiterol. 4 The sustained degree of bronchodilatation achieved by salbutamol 0.25% could not be mirrored by giving two doses of rimiterol 0.5%, the second dose 2 h after the first. 5 Rimiterol 0.5% induced a degree of tachycardia which was similar in peak effect to that observed after salbutamol 0.25%. However, in the controls the second dose of rimiterol, given 2 h after the first, was responsible for only a small increase in heart rate which was not significantly different than that after saline in the other three treatment groups.

Adult↗
PubMed1979

Continuous positive airway pressure during mechanical and spontaneous ventilation. Effects on central haemodynamics and oxygen transport.

The effect of continuous positive airway pressure during continuous mechanical (CMV + PEEP) and spontaneous (CPAP) ventilation on central haemodynamics and systemic oxygen transport was studied in 10 male patients who had undergone aortocoronary bypass graft operation 18 h earlier. With the change from CMV + PEEP 5 cmH2O to CPAP 5 cmH2O, cardiac index was found to increase from 2.58 +/- 0.44 (s.e. mean) to 2.88 +/- 0.19 l/min/m2 (P less than 0.005), and systemic oxygen transport improved from 8.5 +/- 0.6 to 9.5 +/- 1.0 ml/min/kg (P less than 0.05). Arterial oxygen tension and content did not change, but mixed venous blood oxygen tension increased from 3.5 +/- 0.2 to 4.2 +/- 0.2 kPa (P less than 0.005), reflecting the increase in cardiac output. Arteriovenous oxygen content difference decreased from 4.6 +/- 0.5 (CMV + PEEP) to 3.6 +/- 0.2 (CPAP) ml/100 ml (P less than 0.05), while total oxygen consumption remained unchanged. Mean systemic arterial pressure was found to increase from 10.8 +/- 0.4 to 11.6 +/- 0.4 kPa (P less than 0.05) and mean pulmonary arterial pressure changed from 2.2 +/- 0.1 to 2.4 +/- 0.1 kPa (P less than 0.05). Right atrial and pulmonary capillary wedge pressures did not change. Our observations suggest that, in terms of central haemodynamics and tissue oxygen supply, CPAP offers a noteworthy alternative weaning method and an alternative to CMV + PEEP in cases where therapy is prolonged and the patient is able to breathe spontaneously.

Adult↗
PubMed1977

Effect of continuous positive airway pressure breathing on cardiorespiratory function in infants with respiratory distress syndrome.

A method of investigating the cardiorespiratory responses to continuous positive airway presslre (CPAP) in infants with respiratory distress syndrome is described. All measurements were made immediately before and within five minutes of application or any change in level of CPAP. Ventilation was derived from a pneumotachograph and dynamic compliance calculated. We have also measured arterial pH, oxygen and carbon dioxide tensions, arterial blood pressure and central venous pressure. Arterial oxygen tension increased in association with a decrease in the alveolar-arterial oxygen gradient. No consistent changes occurred in pH or carbon dioxide tension. Heart rate and mean arterial blood pressure remained the same but the arterial pulse pressure narrowed and the increase in central venous pressure averaged 17% of the applied airway pressure. There were less variations in both tidal volumes and instantaneous respiratory rates with CPAP compared with spontaneous breathing without CPAP. The respiratory rate decreased, but there were no consistent changes in tidal volume, resulting in a lesser reduction of minute ventilation. Dynamic compliance decreased on CPAP. With correct use of CPAP, and improvement in oxygenation generally occurs without obvious adverse cardiorespiratory effects. CPAP must nevertheless be used cautiously and in conjunction with close monitoring; because when the appropriate pressures are exceeded, it is possible that both circulatory and ventilatory function might be severely compromised.

Blood Pressure↗
PubMed1977

The changes in configuration of the rib cage and abdomen during breathing in the anaesthetized cat.

1. The external surface of the rib cage and abdominal wall in anaesthetized cats was surgically exposed in order to record their movements cinematographically in spontaneous breathing and in paralysed cats, during artificial positive pressure ventilation. 2. Cine-stereophotography was used to allow the recording of the movements of a set of markers placed on the external surface of the trunk wall and the corresponding stereometric data were numerically and graphically processed into three-dimensional drawings. The cine-film frames corresponding to the phases of maximum inflation and deflation of the lungs were analysed to reveal the changes in configuration associated with the respiratory movements of the trunk wall. 3. The changes in shape of the diaphragm and the diaphragm and the displacements of the abdominal viscera between extreme inflation and deflation were recorded by X-ray photography. 4. During spontaneous inspiratory movements, the ribs rotated outwards and rostrally about the costovertebral joints, bringing about an increase in the transverse dimensions of the cage all along its length; these movements were accompanied by a clear-cut caudad displacement of the sternum, caused by the straightening of the costal cartilages and by the widening of the angles defined at sternochondral joints between the sternum and each of the costal cartilages. 5. Neuromuscular blockade abolished muscle tone in the trunk wall, allowing the weight of the viscera markedly to deform its configuration. 6. The inspiratory rib movements of the paralysed animal during artificial inspiration were similar to those during spontaneous breathing but the movements of the sternum were inverted and showed small cranial displacements. 7. The loss of muscular tone under neuromuscular blockade made the abdominal wall more compliant than the rib cage to the positive lung pressure and allowed greater mobility of the viscera with consequent distortion of the shape of the diaphragm. 8. The role of rib cage muscle tone in meeting requirements of purely configurational character in such a shell-like structure is discussed in relation to the optimal mechanical performance of the diaphragm.

Abdominal Muscles↗
PubMed2026

Impact of real-time respiratory function monitoring on neonatal mask ventilation training: a multicentre simulation-based crossover study.

OBJECTIVE: To evaluate whether visibility of respiratory function monitor (RFM) feedback improves mask ventilation performance and influences subsequent ventilation performance during neonatal resuscitation training. DESIGN: multicentre randomised crossover simulation study. PARTICIPANTS: Healthcare professionals involved in neonatal resuscitation training across participating centres. INTERVENTION: Participants performed positive pressure ventilation (PPV) on both term and premature manikins under two conditions: with visible RFM feedback and with the display masked. The order of feedback visibility was randomised. Each participant completed ventilation assessments in both conditions. MAIN OUTCOME MEASURES: Primary outcomes were expired tidal volume (Vte) and mask leak (%). The proportion of breaths within the target Vte range (4-8 mL/kg) was calculated as a performance indicator. Secondary outcomes included variability in Vte and mask leak to assess ventilation stability between conditions. RESULTS: Visible RFM feedback was associated with lower mask leak and improved ventilation stability in the preterm manikin and with tidal volumes entering the target range in the term manikin. Participants initially ventilated with visible feedback maintained performance after feedback removal, suggesting a carry-over learning effect. CONCLUSION: In this multicentre crossover simulation study, visible RFM feedback was associated with changes in mask ventilation performance and evidence of a carry-over learning effect following feedback removal. Real-time visibility of respiratory parameters may strengthen neonatal resuscitation training.

Humans↗
PubMed1975

Changes in strength of lung inflation reflex during prolonged inflation.

Recovery from respiratory inhibition produced by the lung inflation reflex was studied in anesthetized dogs, paralyzed and ventilated with a respiratory pump. During constant ventilation the lungs were periodically inflated using positive end-expiratory pressure, while the respiratory motor output was monitored in the phrenic nerve. Inhibition of the phrenic discharge was followed by gradual recovery throughout 8-min inflation periods despite constant blood gases. Recording afferent potentials in a vagus nerve indicated that adaptation of pulmonary stretch receptors contributed to the initial recovery of the phrenic discharge, but this recovery continued after the receptor discharge had stabilized. The phrenic discharge also recovered after initial inhibition in two situations which avoided stretch receptor adaptation: a) when the stretch receptor discharge from the separate lungs was alternated in an overlapping manner by asynchronous pulmonary ventilation, and b) during continuous electrical stimulation of a vagus nerve. Phrenic activity was temporarily increased above its control value after periods of lung inflation, asynchronous ventilation and vagal stimulation. It is concluded that the lung inflation reflex gradually attenuates during prolonged stimulation due to both stretch receptor adaptation and changes within the central pathways.

Adaptation, Physiological↗
PubMed1976

Effects of continuous positive-pressure ventilation in experimental pulmonary edema.

We compared the effects of continuous positive-pressure ventilation (CPPV), using 10 cmH2O positive end-expiratory pressure (PEEP), with intermittent positive-pressure ventilation (IPPV), on pulmonary extravascular water volume (PEWV) and lung function in dogs with pulmonary edema caused by elevated left atrial pressure and decreased colloid osmotic pressure. The PEWV was measured by gravimetric and double-isotope indicator dilution methods. Animals with high (22-33 mmHg), moderately elevated (12-20 mmHg), and normal (3-11 mmHg) left atrial pressures (Pla) were studied. The PEWV by both methods was significantly increased in the high and moderate Pla groups, the former greater than the latter (P less than 0.05). There was no difference in the PEWV between animals receiving CPPV and those receiving IPPV in both the high and moderately elevated Pla groups. However, in animals with high Pla, the Pao2 was significantly better maintained and the inflation pressure required to deliver a tidal volume of 12 ml/kg was significantly less with the use of CPPV than with IPPV. We conclude that in pulmonary edema associated with high Pla, PEEP does not reduce PEWV but does improve pulmonary function.

Animals↗
PubMed1976

Nasal continuous positive airway pressure. Improvement in arterial oxygenation in hyaline membrane disease.

Continuous positive airway pressure (CPAP) was employed using nasal prongs in 30 neonates with hyaline membrane disease (HMD). There was a significant improvement in mean PaO2 (from 47 to 80 mmHg;p less than 0.001) with no significant change in PaCO2 or pH within a mean 36 min of therapy. Use of the technique allowed reduction of FiO2 to less than 0.60 in less than 20 h in 18 infants. Infants treated within 24 h of birth had significantly greater improvements in PaO2. Complications were infrequent and only 3 of 30 babies developed a pneumothorax while on nasal CPAP. Only 1 of the 23 survivors required mechanical ventilation in addition to nasal CPAP.

Carbon Dioxide↗
PubMed1979

Presence of negative inotropic agents in canine plasma during positive end-expiratory pressure.

Application of positive end-expiratory pressure (PEEP) will reduce cardiac output (CO). Humoral mediation of this event by circulating negative inotropic agents was examined using a rat papillary muscle bioassay. Twenty-seven dogs were anesthetized with an iv pentobarbital infusion. Plasma was obtained before and after 30 minutes of PEEP. The plasma was oxygenated in a small (4.5-ml) papillary muscle chamber using a diffusion membrane. An average PO2 of 416 mm Hg was achieved. PEEP plasma reduced developed tension (Tpd) from 2.16 +/- 1.0 to 1.90 +/- 1.05 g (P less than 0.0001). A fall in Tpd was observed whether or not CO was maintained constant with fluid infusion. Resting tension was unchanged. The percent reduction in Tpd correlated with the fall in CO (r = 0.63, P less than 0.01) when fluid was not infused to maintain CO. Reapplication of control plasma restored Tpd. Barbiturate levels in anesthetized dogs rose from 17.3 to 19.4 microns/ml during PEEP (P less than 0.1). Addition of pentobarbital to normal plasma led to a slight decrease in Tpd only when the concentration exceeded 99 microns/ml. In three experiments on ex vivo perfused hearts, application of PEEP led to lowering of peak systolic pressure (PSP) within 5 minutes. Removal of PEEP restored PSP in a similar time. The results support the hypothesis that the decline in CO with PEEP is mediated in part by a circulating negative inotropic agent.

Acid-Base Equilibrium↗
PubMed1975

Central alveolar hypoventilation in a child: an evaluation using a whole body plethysmograph.

A disorder in the central nervous system control of breathing is thought to be responsible for the clinical syndrome of "primary" or central alveolar hypoventilation. Only 2 of the 7 reported cases in children have included any functional evaluation of this control system disorder. We report the case of a 2-year-old girl with central alveolar hypoventilation attributed to an abnormality in be central nervous system of unknown etiology. In evaluating her ventilatory control system, we used a method (whole body pleildren and small animals but has since received little clinical use. The findings included an irregular respiratory rhythm and a diminished ventilatory response to inhaled CO2, which suggested a functional abnormality of brainstem neurons responsible for rhythmic effective breathing and the CO2 response. A relatively normal change in breathing with sleep and exercise as well as qualitively normal peripheral chemoreceptor function suggested that these aspects of the control system were undisturbed. These findings are contrasted to those in other children; it is suggested that the syndrome of central alveolar hypoventilation may reflect a variety of functional abnormalities in the nervous system control of ventilation.

Brain Diseases↗
PubMed1979

A clinical score for predicting the level of respiratory care in infants with respiratory distress syndrome.

A scoring system was developed to predict the need for transferring infants with respiratory distress syndrome (RDS) from community hospitals to specialized respiratory care centers. Five clinical and laboratory determinations (birthweight, clinical RDS score, FI02, PCO2 and pH) recorded from 100 infants with RDS during one year were utilized in a score with values ranging from 0 to 10. Application of the score to 159 infants with RDS during the following year showed that: (1) 73 per cent of infants scoring less than or equal to 3 received only oxygen by hood; (2) 75 per cent of infants scoring 4--5 required continuous positive airway pressure (CPAP); and (3) 87 per cent of infants scoring greater than or equal to 6 needed mechanical ventilation (7V). Mean scores were significantly different (p less than 0.02) for each type of respiratory therapy employed: oxygen by hood (2.30 +/- 0.19 S.E.M.); CPAP (4.27 +/- 0.16 S.E.M.); MV (6.72 +/- 0.25 S.E.M.). The accuracy and simplicity of the score make it valuable for the physician in the community hospital to assist in deciding when to transfer a neonate with RDS for more intensive respiratory therapy.

Birth Weight↗
PubMed1975

Elective postoperative I.P.P.V. for extensive head and neck skin grafting.

Patients with extensive skin-grafting of the head and neck are managed for the first 24-48 hours postoperatively in the Intensive Care Unit with muscle paralysis, controlled ventilation, timed parenteral analgesia and sedation. The aims are to provide full immobilization of the graft and to allow pressure dressings without embarrassment to the airway. The regime is suggested as an added indication for intensive care therapy.

Adenocarcinoma↗
PubMedDate not supplied

Low-frequency positive pressure ventilation with extracorporeal carbon dioxide removal (LFPPV-ECCO2R): an experimental study.

We describe a new form of mechanical pulmonary ventilation, low-frequency positive pressure ventilation with extracorporeal CO2 removal (LEPPV-ECCO2R). In a series of animal studies the rate of mechanical ventilation was 0.66, 1, 2, and 4 min-1 at a tidal volume of 3, 10, and 15 ml kg-1. We were able to maintain normal blood gases and normal lung volumes and lung mechanics even at the lowest ventilator rate with tidal volumes of 10 or 15 ml kg-1. Each experiment lasted 7 hours. Our data suggest a possible new dimension in the management of a difficult patient on mechanical pulmonary ventilation.

Animals↗
PubMed1978

Ventilation-perfusion scans in neonatal regional pulmonary emphysema complicating ventilatory assistance.

Two cases of ventilator-related neonatal lobar overexpansion with similar radiographic appearance, but probably different pathogenesis, are presented. In one infant, persistent interstitial lobar emphysema was confirmed by markedly decreased perfusion shown on scintigraphy; this information was of great value in predicting the beneficial effect of lobectomy. In the other case, ventilation and perfusion scans indicated functional value of the emphysematous lobe and correctly suggested conservative management. Radioisotope lung scans may provide valuable information regarding lung function in regional pulmonary emphysema associated with assisted ventilation in neonatal respiratory distress syndrome, and thus determine patient management.

Humans↗