Continuous Positive Pressure Breathing Research Articles

Behavior of expiratory neurons in response to mechanical and chemical loading

The response of medullary expiratory neurons to added mechanical and chemical loads was studied in anesthetized cats. Alterations in burst characteristics and central timing were compared in the intact and bilaterally vagotomized cat. The following results were obtained: (1) Graded expiratory airflow resistances caused progressive increase in burst duration, spikes per burst and firing rate; similar effects were noted for end-inspiratory tracheal occlusions and continuous positive pressure breathing; all facilitation was eliminated by vagotomy. (2) Graded inspiratory airflow resistances delayed the onset of an expiratory burst but did not change the overall burst characteristics. (3) Acute hypercapnia increased ventilation without noticeable changes in expiratory burst characteristics; acute hypoxia produced a reduction in burst duration concomitant with changes in ventilation. It is concluded that (1) expiratory neurons are responsive to vagally mediated volume information and (2) transient hypoxia and hypercapnia sufficient to increase ventilation does not increase the firing rate of expiratory neurons but exerts differential effects with respect to timing. It is suggested that expiratory duration is related to the time integral of expired volume and that the increase in FRC imposed by expiratory loads does not alter the central timing of the next inspiration.

Continuous positive pressure ventilation in children with bronchopneumonia

The application of a small end-expiratory pressure of 5 cmH2O to the assisted ventilation of nineteen children (mean age 19 months) with bronchopneumonia was compared with intermittent positive pressure ventilation. Within 1 h of introducing continuous positive pressure ventilation the alveolar-to-arterial oxygen gradient was reduced in most patients, with an increase in functional residual capacity and a decrease in total pulmonary blood shunt. Physiological dead space was also reduced, a feature not observed in other studies, and the significance of this finding is discussed. The use of continuous positive pressure ventilation in broncho-pulmonary infection was shown to be effective even at small pressures, and can be recommended especially for patients requiring long-term ventilation.

Tissue Oxygen Available as a Criterion for the Effectiveness of Continuous Positive Pressure Breathing

As little as 3-5 cm H2O increase in proximal airway pressure applied to normal lung reduces cardiac output. It is postulated that decreased pulmonary compliance in respiratory distress syndrome (RDS) acts as a barrier thus offsetting this effect. Since cardiac output is not routinely measured, severe reduction in it could accompany regression of disease while maintaining the same airway pressure. This study was undertaken to determine whether tissue oxygen available (O2a) could be used to detect changes in perfusion during continuous positive pressure breating (CPPB). CPPB was evaluated in 10 normal rabbits (CL = 9.5 +/- 1.8 cc/g at 25 cm H2O) and in 10 pulmonary-damaged rabbits (CL = 5.5 +/- 1.4 cc/g at 25 cm H2O) produced by subjecting them to 100% O2. Airway pressure was increased from 0-15 cm H2O in 3 cm H2O increments at 10-min intervals. O2a and PaO2 were monitored continuously. In the normal group, O2a decreased at 3 cm H2O airway pressure, reaching 22% of control at 12 cm H2O, at which pressure PaO2 decreased. Breathing 100% O2 at this airway pressure increased PaO2 to 408 mm Hg, whereas O2a returned to 45% of control. In the experimental group, O2a decreased at 9 cm H2O airway pressure, at 12 cm H2O it was 36% of control at which pressure PaO2 decreased slightly. Breathing 100% O2 at this airway pressure increased PaO2 to 316 mm Hg, and increased O2a to 200% of control. These data indicate that with excessive airway pressure, muscle hypoxia may exist during systemic hyperoxemia and that a low compliance lung exerts a protective effect on O2a. Since changes in cardiac output during CPPB are compliance dependent, and since O2a is perfusion dependent, tissue oxygen available could provide a means of selecting optimal airway pressure during CPPB.

Vagal control of diaphragm timing in cat while breathing at elevated lung volumes

This paper proposes and tests an hypothesis to account for the roles of the volume and rate components of vagal feedback in determining the steady-state pattern of breathing during continuous positive pressure breathing (PPB) and expiratory threshold loading (ETL) in Dial anesthetized cats. During PPB the duration of diaphragm activity (Tdi) is shortened; the duration of its expiratory pause (Tep) is lengthened with little or no change in cycle duration (Tt); with onset of inspiration, flow (dV/dt) is increased; as inspiration proceeds, flow decelerates (d 2/dt 2). During ETL Tdi, Tep and Tt are all prolonged; dV/dt is decreased at onset of inspiration, with either no change or an acceleration in flow as inspiration proceeds. PPB and ETL cause similar increases in resting lung volume and Tep, and high negative correlations between Tdi and flow. These relationships suggest that the ‘volume component’ of vagal feedback is one important factor controlling Tep whereas the ‘rate component’ contributes to the restraint of Tdi.

Influence of early introduction of continuous positive pressure breathing on the course of hyaline membrane disease.

John, Elizabeth, Thomas, D. B. and Burnard, E. D. (1976). Aust. paediat. J., 12, 276–280. Influence of early introduction of continuous positive pressure breathing on the course of hyaline membrane disease. An alternate case study was carried out in babies with moderate to severe hyaline membrane disease to determine the effect of early introduction of continuous distending pressure on the course of the disease. 21 pairs of babies, matched for gestation, entered the trial. It was found that the early introduction of continuous distending pressure shortened both the duration of the disease and the time of exposure to high concentrations of oxygen. There was no important difference in complications.

Tissue oxygen available (O2alpha) as a criterion for the effectiveness of continuous positive pressure breathing (CPPB).

Tissue oxygen available (O2alpha) as a criterion for the effectiveness of continuous positive pressure breathing (CPPB).

A modification of the Bird Mark VIII ventilator to deliver continuous positive pressure breathing and intermittent mandatory ventilation.

A Bird Mark VIII ventilator was modified to produce a simple and inexpensive C.P.P.B. and I.M.V. circuit. A Bain Breathing Circuit allowed the manifold to be placed near the ventilator. The negative pressure and flow to the injector produce C.P.P.B. The continuous flow of the Mapleson D Modification furnished constant inflow to provide humidified fresh gas to the reservoir and the patient circuit for I.M.V. An accompanying graph illustrates suggested flow rates and CO2 elimination (Figure 2).

Tonic vagal influences on inspiratory duration

The tidal volume (V T), inspiratory (Ti) and expiratory (Te) durations were determined in anesthetized rabbits, cats and dogs under normal conditions, during continuous positive or negative pressure breathing. Elastic loads up to complete occlusion of the airways were applied in order to determine the V T-Ti and Te-Ti relationships. The larger the end-expiratory lung volume the steeper the V T-Ti relationship, the smaller the increase of Ti and the greater the increase of Te produced by the load. Hence, the larger the end-expiratory lung volume the steeper the Te-Ti relationship. In vagotomized animals airways occlusion did not affect Ti and Te. Ti of occluded breaths in vagotomized animals was longer than that of occluded breaths in intact animals, whereas Te was similar at the resting volume of the respiratory system (FRC), shorter above FRC and longer below FRC. These results show that both phasic and tonic vagal discharges determine Ti and Te.

The Peripheral Hemodynamic Effects of Continuous Positive Transpulmonary Pressure Breathing In Neonates Free From Cardiorespiratory Disease

We applied continuous positive transpulmonary pressure (CPTP) by face mask to 22 spontaneously breathing infants who were free from cardiorespiratory disease, and measured resultant changes in peak esophageal pressure (Pes) and peripheral perfusion (Q1). We measured Pes by balloon and transducer, and Q1 by venous occlusion plethysmography with a mercury-in-rubber strain gauge. Application of 7.6 cm H2O CPTP led to a 13% decrease in Q1 (paired t-test=2.39; P less than .02). Thirty-two percent of the applied CPTP was detected as a change in Pes. The biological significance of a 13% decrease in peripheral perfusion is probably minimal.

Editorial: Practical method to regulate PEEP.

As we all know, scientific research is often criticized because its results are not widely known or are so esoteric that their applicability is ignored. Four years ago, I prepared an editorial1 on a very interesting paper2 reviving an old area of research — namely, the effects of continuous vs. intermittent positive-pressure breathing. Since then, numerous related studies have been performed and the benefits of positive end-expiratory pressure (PEEP) have been carefully analyzed and clearly demonstrated. In their paper in this issue, Suter and his associates review the various indexes that have been used to assess the efficiency of PEEP; . . .

Effect of positive-pressure breathing on aADN2 in hyaline membrane disease

In seven subjects with hyaline membrane disease and breathing 40-70% oxygen in nitrogen, the effect of continuous positive-pressure breathing (CPPB) was examined by application of a continuous negative pressure (10 cm water) about the thorax and assessment of the alveolar-arterial tension differences for nitrogen (aADn2) and oxygen (AaDo2). On CPPB, there was a decrease in the aADn2 by a mean 9 mmHg and a decrease in the AaDo2 by a mean 44 mmHg. This corresponded to a decrease in the total venous admixture (Qva/Qt) of 0.20 and to a decrease in the venous admixture due to a true right-to-left shunt (Qs/Qt) of 0.19. These data were interpreted to mean a significant improvement in Va/Qc imbalance within open ventilated parts of the lung, which could be responsible, particularly by relief of local alveolar hypoxia, for reduction of the pulmonary vascular resistance and the true right-to-left shunt.

Respirator weaning of the newborn

Weaning of neonates from assisted ventilation or continous positive pressure breathing is a complex process. Unfortunately, at present we lack sensitive indices to measure the infant's ability to sustain spontaneous breathing. In the absence of such criteria we should rely heavily on clinical findings correlated with available biochemical data. Good clinical acumen and experience is necessary for successful weaning.

Acute "adult respiratory distress syndrome"

SummaryFirstly, the different physiopathological pulmonary mechanisms of hypoxaemia are briefly described : alveolar hypoventilation, impairment of diffusion, venous-to-arterial shunts, together with the influence of inhalation of O2 and exercise.Secondly, a more extensive review is given about the appearance, the etiology and pathogenesis, the pathology, radiology and clinical features of the acute respiratory insufficiency produced by intrapulmonary venous-to-arterial shunts. Some specific aspects of the treatment are discussed : administration of large amounts of oxygen, continuous positive pressure breathing and administration of corticosteroids.

Recognition and Management of the Adult Respiratory Distress Syndrome

Severe alveolar-capillary membrane injury from a variety of causes leads to a recognizable clinical-pathologic syndrome we have termed the adult respiratory distress syndrome (ARDS). 1 Ashbaugh DG Bigelow DB Petty TL et al. Acute respiratory distress in adults. Lancet. 1967; 2 PubMed Google Scholar , 2 Ashbaugh DG Petty TL Bigelow DB et al. Continuous positive pressure breathing (CPPB) in adult respiratory distress syndrome. J Thorac Cardiovasc Surg. 1969; 57 PubMed Google Scholar , 3 Petty TL Ashbaugh DG The adult respiratory distress syndrome: Clinical features, factors influencing prognosis and principles of management. Chest. 1971; 60 Google Scholar Identification of the primary cause of ARDS, whether sepsis, hemorrhagic shock, overwhelming viremia, pancreatitis, thoracic or nonthoracic trauma, fat embolism, aspiration, or diffuse intravascular coagulation is basic to the initiation of therapy.

Treatment of the Isolated Edematous Canine Lung with Graded PEEP

Since the clinical introduction of continuous positive pressure breathing (CPPB) in 1967 by Ashbaugh et al,1 this therapy has gained increasing acceptance for treatment of the adult and infant respiratory distress syndromes.2-4 It has been observed to depress cardiac output however, and in an effort to eliminate this variable we have investigated the effects of PEEP (positive end-expiratory pressure) in the isolated canine lung made edematous by venous constriction. Ten mongrel dogs weighing 14 to 24 kg were used: four provided control lungs and six were treated with graduated levels of PEEP.

A New Method of Providing Continuous Positive Pressure Breathing in Infants

A simpler device for the production of CPPB has been described which is smaller, lighter, but functions as well as most conventional apparatus.

THE EFFECT OF POSITIVE PRESSURE BREATHING ON a-A.DN2 IN HYALINE MEMBRANE DISEASE

In 7 subjects with hyaline membrane disease breathing 40-70% oxygen in nitrogen, the effect of continuous positive pressure breathing (C.P.P.B.) was examined by application of a continuous negative pressure (10 cm. water) about the thorax and measurement of the changes in PaN2, PaO2, and PaCO2. On C.P.P.B. all sugjects showed improvement, the PaO2 was a mean 38 mm Hg. higher, the SaO2 was 9%, higher, the A-a.DO2 was reduced from 279 to 235 mm Hg. and the a-A.DN2 was reduced from 23 to 14 mm Hg. Assuming values for the composition of mixed venous blood, this meant that on C.P.P.B., the total venous admixture (Qva/Qt) was 0.20 lower, the true right-to-left shunt (Qs/Qt) was 0.19 lower and the venous admixture produced by open low V/Q units (Qo/Qt) was 0.01 lower. Whilst recruitment of collapsed alveoli certainly occurred and was responsible for some of the improvement in A-3.DO2, consideration of the La Place relationship and the overall decrease in a-A.DN2 indicates that another important mechanism was improvement in ventilation of an open, extremely low V/Q compartment. This could be responsible, particularly by relief of local alveolar hypoxia, for reduction of the pulmonary vascular resistance and the true right-to-left shunt. * Presently Baylor College of Medicine, Houston. ** Presently Brown University, Providence.

CARDIOVASCULAR RESPONSES TO CONTINUOUS POSITIVE PRESSURE BREATHING IN THE PIGLET

Continuous positive pressure breathing (CPPB) has recently been used in the management of Respiratory Distress Syndrome of the newborn. The healthy piglet was chosen as a model to study the effects of CPPB on heart rate (HR), mean arterial blood pressure (BP) and cardiac output (CO). Fourteen piglets, 3 to 24 days old, were lightly anesthetized with halothane or pentobarbitol and artificially ventilated with a mixture of O2 and N2O. The end-tidal pressure (ETP) was varied from 0 to 17 cm H2O measured by an intratracheal catheter. CO was determined by dye dilution technique using cardiogreen. Arterial blood gases were measured at frequent intervals. The HR changes varied. BP decreased in each of 14 piglets when the ETP was raised to +3 cm H2O. For an ETP of 10-17 cm H2O there was a decrease in BP which varied from 6% to 63%. CO decreased in each of 9 animals in which CO was studied when the ETP was raised to +5 cm H2O. For an ETP of 12-17 cm H2O there was a decrease in CO which varied from 30% to 38%. Tnere was a significant inverse relationship between BP and CO with respect to level of ETP. These results show that CPPB decreases BP and CO in piglets.

Radiological manifestations in patients on continuous positive-pressure breathing.

Chest films of patients on continuous positive-pressure breathing (CPPB) occasionally prove difficult to interpret. Diaphragmatic paralysis may be masked, and lobar atelectasis may present with confusing findings. If the radiologist is not aware that the patient is receiving CPPB, two other findings may be confusing: (a) hyperinflation of the lungs and (b) unusually rapid clearing of pulmonary edema, atelectasis, or both. Complications of CPPB include acute gastric dilatation, oxygen toxicity, pneumothorax, pneumomediastinum, and pulmonary interstitial emphysema. In some cases, prolonged intubation may result in tracheal stenosis and/or malacia.

Phrenic nerve palsy treated by continuous positive pressure breathing by nasal cannula.

Phrenic nerve palsy treated by continuous positive pressure breathing by nasal cannula.