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This paper reports a method of sampling fluid from the peribronchial-perivascular space (PBVS) of the lungs in intact closed chest dogs. The PBVS was sampled by introducing a wick catheter into the PBVS through a mediastinoscope. The right lymph duct was cannulated by the method of Vriem and Ohkuda [J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 54: 199, 1983] for collection of lymph to compare to peribronchial fluid. The colloid osmotic pressure (COP) of PVBS and right lymph duct fluid (RLDF) were compared in a series of dogs infused with lactated Ringer's solution (LR) and lactated Ringer's combined with three other conditions: left atrial balloon inflation (LRB), oleic acid infusion (LRO), and oleic acid infusion and left atrial balloon inflation (LROB). Prior to LR infusion, the volume of samples of fluid from the PBVS wicks was inadequate for measuring COP (less than 4 microliters). This difference was significantly only in the later samples at 3, 4, and 5 hr in the LR and LRB groups. In the LRO and LROB groups, protein content and amount of fluid sampled were greater than in the LR and LRB groups, but the mean COPs of the wick PBVS and RLDF were not significantly different. This method of directly sampling interstitial fluid from the lungs of dogs without thoracotomy confirms the high COP of fluid from the lung interstitium. This method of PBVS fluid sampling is potentially feasible in a human patient undergoing mediastinoscopy.

This study compared radiographic measurements of regional lung volume with corresponding physiologic measurements. The database included 48 normal, supine adults who had previously undergone spirometry and helium-dilution lung volume measurements to determine physiologic functional residual capacity (G-FRC) and total lung capacity (G-TLC). Chest x-rays had also been obtained for these subjects at functional residual capacity and total lung capacity. To calculate radiographic lung volumes at functional residual capacity and total lung capacity (R-FRC and R-TLC, respectively), we traced the lung outline from the chest x-ray, and digitized each outline. We then calculated total and regional lung volumes, using equations previously derived from computed tomographic scans. R-FRC and R-TLC were closely correlated (r = 0.973, maximum SEE 6.8%) with G-FRC and G-TLC, whether or not separate equations were used for regions below the diaphragm. Using only maximum anteroposterior diameter reduced the r-value to 0.957 (SEE 9.6%). The accuracy of our method of radiographic measurement of regional lung volume was validated by the concurrence between the physiologic and radiographic measurements.

Transpulmonary pressure, air flow, and end-tidal carbon dioxide levels were measured in normal human volunteers during hypocapnic, eucapnic, and hypercapnic hyperventilation. Respiratory rate and tidal volumes were well matched at a minute ventilation of 52 L. on three inspired gas mixtures: 21 per cent oxygen and 79 per cent nitrogen; 5 per cent carbon dioxide, 21 per cent oxygen and 74 per cent nitrogen; and 12 per cent carbon dioxide, 21 per cent oxygen and 67 per cent nitrogen. Respiratory rate, tidal volume, lung compliance, resistance, and resistive work per liter were calculated with a digital computer. In 13 experiments in 7 normal volunteers, no net bronchoconstriction or bronchodilatation was observed when eucapnic hyperventilation was compared to hypocapnic or hypercapnic hyperventilation. During hyperventilation of this degree, a change in bronchomotor tone owing to alteration in arterial or alveolar PCO2 either does not occur or else is masked by other reflexes or mechanical factors acting on the bronchi.

Computed tomographic scans show true cross-sectional area of a segment of the chest. Measurement of the cross-sectional area of the lung at several adjacent levels permits calculation of a geometrically defined volume. CT scans from 26 cases were used to derive equations to predict regional volume from measurements which can be obtained from plain PA and lateral chest films. Separate equations were derived for slices above and below the top of the diaphragm. The best correlation between linear dimensions and true volume was obtained with equations that used lung width and antero-posterior (AP) diameter of each scan, maximum AP lung diameter, and relative scan level (apex to base). These equations predicted the volumes of individual slices above the diaphragm with a correlation coefficient (r) of 0.99 on the right, 0.97 on the left. Below top of the diaphragm, r was 0.91 on the right, 0.92 on the left. Total lung volume was predicted with an r of 0.98 (s.e. 4.8%) on the right and 0.97 (s.e. 5.3%) on the left. Using total chest width instead of AP diameter of each slice reduced r to 0.96 for the volume of either lung. This method compares favorably with previous regression or geometric approximation methods for total lung volume and also makes it possible to obtain estimates of portions of lung volume from chest films.

Gravity has significant effects on the microvascular pressure in the lungs and thus on regional fluid filtration in the lungs. Below the level of the heart, gravity increases the microvascular pressure with respect to the left atrial pressure; above the level of the heart, microvascular pressure is less than atrial pressure. To assess the contribution of gravity to fluid filtration in the lungs independent of left-heart filling pressure, the distribution of lung volume above and below the left atrium must first be determined. To permit calculation of the contribution of hydrostatic pressure per unit of lung volume, 26 computed tomographic scans of the entire chest were traced and measured, marking the level of the center of the left atrium (LAL) on each slice. The intrathoracic volume above and below the left atrium was measured by multiplying scan slice thickness by the area of the lung above or below the LAL measured on each scan slice. On 16 scans, intrathoracic volumes of 1-cm horizontal layers of lung above and below the LAL were also calculated by measuring corresponding segments of the transverse scan slices. The calculations indicate that in the supine posture more lung is dependent than when upright, and that elevation of a patient to 30 degrees reduces the volume of lung below the LAL nearly as much as does the upright posture.

This paper describes a method of determining the amount of work on the lungs done by the patient and the ventilator using various modes of ventilation. The method uses a pneumotachograph to measure air flow, and measures pressure from an esophageal balloon and at the airway. The patient's work is separated from the ventilator work by analysis of the esophageal pressure. When esophageal pressure is below end-expiratory esophageal pressure during inspiration, work is being done by the patient. When esophageal pressure is above end-expiratory level, the ventilator is doing the work. The calculations are done using an IBM PC computer. The studies of normal subjects show that in the assist mode with increased airway resistance, significant work by the subject is required to trigger the ventilator. Two patients are presented when the assist mode resulted in excessive amounts of work and fatal outcomes. Measurement of the mechanical work required of the patient can provide useful information for the control of ventilator therapy.