Diffusing capacities and ventilation: perfusion ratios in patients with the clinical syndrome of alveolar capillary block.

Studies were performed on 10 patients with the clinical syndrome of alveolar capillary block while each patient was breathing four different inspired oxygen mixtures. The data were interpreted using the principle of the Bohr integral isopleth with which alveolar oxygen tension in the differently ventilated parts of the lung can initially be treated as unknown. It is then possible to determine the distribution of ventilation, of perfusion, of diffusing capacity, of lung volume, and of alveolar and end capillary blood oxygen tension in the variously functioning parts of the lung. In two patients shunts were the major factor interfering with oxygen transfer. In four others inequalities in ventilation: perfusion ratios and in diffusing capacity in different parts of the lung were the factors interfering with oxygen transfer. In four more patients ventilation: perfusion ratios were the same throughout the lung, the only disturbance of oxygen transfer being in the total diffusing capacity or in its distribution between the different parts of the lung.

Acute respiratory failure in scoliosis or kyphosis: prolonged survival and treatment.

Acute respiratory failure (ARF) in adults with severe thoracic spinal deformity is said to be a preterminal event with a median survival of one year. Twenty patients with ARF (mean +/- S.D., arterial oxygen tension [PaO2] 35 +/- 7 mm Hg, arterial carbon dioxide tension [PaCO2] 63 +/- 9 mm Hg, pH 7.34 +/- 0.08) due to severe scoliosis or kyphosis (spinal curve 113 +/- 28 degrees ) were seen between 1965 and 1980. All 20 survived the initial episode of ARF and during the follow-up period (median, six years) experienced 2.4 additional episodes of ARF. The age at presentation was 52 years (mean, range 13 to 78), and the cause of spinal deformity was idiopathic (seven patients), poliomyelitis (seven), tuberculosis (five), and arthrogryposis multiplex congenita (one). ARF was treated with controlled low dose oxygen by Venturi mask and intensive general measures in 13 patients and by mechanical ventilation in seven. Of the latter seven patients, ventilatory failure was treated in two with a tank respirator and a cuirass, avoiding endotracheal intubation. Outpatient management was similar to conventional therapy for chronic obstructive pulmonary disease (COPD). Severe restrictive ventilatory impairment characterized the group after recovery from the first episode of ARF: vital capacity (VC) 906 +/- 362 ml (31 percent predicted) and FEV1 589 +/- 197 ml (23 percent). During follow-up, the VC decreased by 1.5 ml/year and the FEV1 by 13.9 ml/year. The PaO2 increased by 2.6 mm Hg/year and the PaCO2 increased by 1.7 mm Hg/year. Successful management of ARF due to severe scoliosis or kyphosis is possible in the great majority of patients, and long-term survival may be expected. Unlike COPD, pulmonary function following ARF in kyphosis or scoliosis deteriorates at a slower than expected rate and, in fact, may improve with treatment over many years.

Does impaired diffusion for oxygen exist in diseased lungs?

The historical development of ideas concerning impairment of diffusion in the lungs (alveolar-capillary block) is described. The major publications by Riley and Cournand, and others, which showed that impairment of diffusion exists in some diseased lungs were based on careful measurements of the arterial oxygen tension or saturation of patients. These papers described work carried out in the State of New York. Other workers claim to have shown that impairment of diffusion does not exist in diseased lungs: the impairment of oxygen transfer in alveolar-capillary block is said to be due to uneven ventilation-perfusion ratios. The publications which adopt this point of view are mostly based on measurements of the concentration of inert gases in the arterial blood. By chance, the workers who found that diffusion is not impaired in diseased lungs were all in the State of California. It is pointed out here that the California workers have failed to recognize that diffusion, like ventilation and perfusion, is distributed, i.e. varies greatly in different alveoli. This led them to ignore the fact that in some alveoli in diseased lungs, diffusion is so greatly impaired that some inert gases do not reach equilibrium at the end of the pulmonary capillary: the tension of inert gas in end-capillary blood is different from the tension of the same gas in alveolar gas. This invalidates the basic assumption underlying the inert gas method.

Relief of hypoxia-related bronchoconstriction by breathing 30 per cent oxygen.

Airway resistance decreases when hypoxemic subjects with chronic obstructive pulmonary disease (COPD) breathe 30% O2. To verify this finding and to localize the site of action of O2, flow-volume curves on air and helium-O2 mixtures were obtained before and after subjects breathed 30% O2. Patients with COPD and hypoxemia showed an increase in flow rates and a decrease in the density dependence of flow while breathing 30% O2. Atropine produced a similar change in flow rates and density dependence, but then no further change occurred with 30% O2. Five control subjects with COPD, who performed the same sequence of tests without breathing 30% O2, showed no change in flow rates or density dependence. Normal control subjects also showed no change in flow rates or density dependence while breathing 30% O2. Breathing 30% O2, relieves hypoxia-induced bronchoconstriction and appears to act on large airways.

Oxygen concentration from room air. A new source for oxygen therapy in the home.

Most oxygen concentrators use molecular sieves that selectively adsorb molecules according to their size and polarity. Their present rental cost is about half that of the traditional oxygen tanks or liquid-oxygen systems. Two concentrators have been tested. They are able to produce both high oxygen concentrations (95% oxygen at 2 L/min) and high flow rates (10 L/min with 40% oxygen), which remained stable for one week. After 24 hours of continuous use, neither machine concentrated toxic gases from room air in a city. Both were suitable for use with 24% and 28% Venturi masks.

Potentiation of pulmonary vasoconstrictor response with repeated intermittent hypoxia.

To determine the consistency of the pulmonary vasoconstrictor response to hypoxia, dogs were anesthetized, intubated, and ventilated alternately with air and 10% oxygen. Catheters were placed in the pulmonary artery for measurement of pulmonary artery pressure (PAP), pulmonary capillary wedge pressure, and cardiac output and in the femoral artery for monitoring systemic blood pressure and arterial blood gases. Arterial PCO2 and pH were kept at steady levels throughout by ventilating the dogs with a respirator so that only the isolated effect of hypoxia on the pulmonary vasculature was studied. It was found that there was a progressive rise in the PAP with repeated exposure to the same hypoxic stimulus. In 12 dogs, the mean increase in the PAP was 28% above the base line on the 1st hypoxic exposure, rising to 99% by the 10th exposure over the course of 5 h. It was concluded that interpretation of action of agents blocking or enhancing the hypoxic response must take into account this inherent potentiation of the response on repeated exposure to hypoxia.

Pulmonary function in asymptomatic adolescents with idiopathic scoliosis.

Pulmonary function studies were performed in 28 asymptomatic adolescents with idiopathic scoliosis. Tests included spirometry, flow volume curve, measurements of inspired gas distribution, diffusing capacity, closing volume, ventilatory response to carbon dioxide, and arterial blood gas analysis. In addition to the well-known decreases in lung volumes, a reduction in diffusing capacity, arterial oxygen tension, and ventilatory response to carbon dioxide were also documented. Significant correlations existed between the severity of the spinal curvature and the decrease in lung volumes. A significant correlation was also found between the degree of hypoxemia and the reduction in the diffusing capacity, suggesting that a low diffusing could be the cause of the observed arterial hypoxemia.

Diffusing capacity in idiopathic scoliosis and its interpretation regarding alveolar development.

We measured lung volumes, diffusing capacity by the single breath method (DL), membrane permeability (DM), and capillary blood volume (Vc) in 22 subjects with idiopathic scoliosis (mean angle of curvature, 66 degrees). Compared with an age-matched group, vital capacity, total lung capacity, and functional residual capacity were respectively, 21% (p less than 0.0001), 18% (p less than 0.01), and 15% (p less than 0.05) lower. The DL was 17% lower (p less than 0.01), but specific DL (DL divided by alveolar volume = DLVA) was the same. For both groups, DLVA was inversely correlated with VA. The same qualitative relationship existed between DM, Vc, their specific values, and VA except for a larger spread of Vc in the scoliotic group. The data show that DL and its components, DM and Vc, are normal in idiopathic scoliosis when reduced lung volumes are allowed for. These findings are consistent with partial failure of alveolar enlargement as a result of the thoracic deformity rather than any atrophy of the alveoli or pulmonary vasculature. Thus scoliosis results in a delay of lung development, such that in a group of symptomatic patients with moderate degrees of deformity (mean angle of curvature, 66 degrees), lung volumes and DL are about 80% of that of an age-matched control group; the alveolar characteristics of a 12-yr-old with scoliosis are therefore similar to those of a 9-yr-old normal child.