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Many patients with acute asthma are treated with intermittent positive-pressure breathing (I.P.P.B.) devices. The development of pneumothorax in two fatal cases and its association with I.P.P.B suggests that this complication may be an important hazard in the treatment of acute asthma.
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This study establishes the mean values, variations, and trend of pulmonary function during the first few hours of life in premature lambs. Measurements of intraesophaheal and tracheal pressure, air flow, tidal volume, and functional residual capacity enabled calculations of lung compliance, specific lung compliance, and inspiratory and expiratory resistance of the lungs. Arterial carbon dioxide tension and pH were maintained within a physiologic range. Mean arterial oxygen tension (PO2) at elevated inspired oxygen tension, varied in the individual animals from 51 to 185 mm Hg at an inspired oxygen concentration of 46 to 71%. It was found that the lungs of premature lambs delivered by cesarean section were mechanically unstable; the lambs were all ineffectual at breathing and required some form of mechanical ventilation. During the first 6 hours of postnatal life the lungs of premature lambs are characterized by a wide range of mechanical values and blood gas tensions.
29 patients using a home respirator have been studied. Management of the respirator and inhalation were correct in 86%. Bacteriologic contamination in home treatment poses few problems. Blood gases and spirometric lung function tests do not demonstrate amelioration but show stabilization in long term treatment. Costs are high. Nevertheless, this treatment is indicated in certain carefully selected patients. Follow-up checks are essential.
First prophylactic and therapeutic possibilities in cor pulmonale are shown on the basis of its pathogenesis. Our own results illustrate the effect of therapy of the underlying lung disease and of the concomitant respiratory insufficiency on the pulmonary arterial hypertension. The relationship between pulmonary artery pressure (PAp), arterial oxygen tension, forced expiratory volume of 1 second (FEV1%VC) and slow inspired viral capacity (VC) is analysed. In obstructive respiratory disorders the PAp rises when FEV1 falls below 40% of VC, in restrictive disorders when VC falls below 70% of predicted rate. 27 patients with chronic obstructive lung disease were treated with bronchodilator aerosols by intermittent positive pressure breathing (IPPB) during 2 years after a control period of 2 years: VC and FEV1 improved, the increase of total lung capacity and the deterioration of arterial blood gases came to a halt. The elevated PAp was always significantly reduced by oxygen therapy or IPPB or the combination of both. Finally, the rationale for avoiding physical stress in established cor pulmonale is illustrated: in healthy men PAp increases by less than 20% when cardiac output is doubled. In patients with cor pulmonale PAp rises to three times the initial value under the same conditions.
Functional residual capacity (FRC) was measured in 12 postoperative patients and in one preoperative patient before and after they received intermittent positive pressure breathing (IPPB) with room air for ten minutes at a peak delivered pressure of 15 cm H2O. Ten patients had a normal or low pretreatment FRC. After cessation of IPPB, the mean FRC decreased further. Arterial oxygen tensions, measured in 11 of the 13 patients, decreased in all 11 from a pretreatment mean of 67.8 +/- 4.3 mm Hg to an immediate posttreatment mean of 57.7 +/- 4.2 mm Hg. In five patients repeated arterial blood gases were measured. At 30 minutes, their arterial oxygen tensions had returned to the pre-IPPB values. This study demonstrates that the routine use of IPPB in postoperative patients accentuates preexisting hypoxia and, therefore, must be used with caution.
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.
The effect on the systemic and pulmonary circulation of unsupplemented nitrous oxide in about 30% oxygen, with and without IPPV, was investigated in five cardiac patients and compared with control periods at rest with air breathing. The results of this investigation show that nitrous oxide in conventional oxygen concentration does not cause any great haemodynamic changes. During tracheal intubation, however, significant increases in both systemic and pulmonary blood pressures were registered. However, these pressures reverted to the control values immediately after the tracheal intubation. The results of this study support many earlier clinicaly good experiences obtained when using this conventional nitrous oxide-oxygen mixture in cardiac patients.
After considering the indications for tracheotomy on his intensive care unit, the author describes the risks of this operation and the means of avoiding them. Out of 1940 patients admitted over a period of 5 years on the intensive care unit of the Royal Victoria Infirmary, Newcastle-on-Tyne, 175 were tracheotomised, inclusing 133 who were submitted to intermittent positive pressure ventilation. Only three patients had complications linked to the tracheotomy, complications which were the cause of the death of two of them.
High frequency, positive pressure ventilation during anesthesia for bronchoscopy, uses the intermittent delivery of oxygen and an anesthetic gas mixture thus avoiding the risks of hypoxia, retention of carbon dioxide and concomitant acidosis. This technique may be used with low pressures in the airways (8 to 10 cm of water during insufflation).
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A comparative study of the venous contamination (Qs/Qt = (Cc'O2 - CaO2) / (Cc'O2 - C-vO2) under FIO2 = 0.45 - 0.6 and under FIO2 = 1, was realised in 9 patients with lesions of pulmonary oedema. Increasing the FIO2 lead to an increase in the venous contamination three times (average increase was 36 p. 100 of the initial value), to no change two times and a decrease four times (average decrease of 34 p. 100). The values of the venous contamination under average FIO2 are statistically lower in the group where it rises on increasing the FIO2 than in that in which it falls or remains unchanged (p is less than 0.005).
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