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M F Petrini

Publications and source records attributed to M F Petrini.

25 records · Page 2Linked to original sources
PubMed1983

Interaction of series and parallel dead space in the lung.

The volume of ventilation delivered to unperfused zones of the respiratory system (respiratory dead space) can be divided into the volume occupied by the conducting airways (series dead space) and the volume of unperfused alveolar space (parallel dead space). The effect of the interaction between these two components of dead space on steady-state gas exchange was first evaluated with a mathematical model. The presence of both parallel and series dead space was predicted to underestimate the dead space measured by the inert gas elimination technique (VDIG). This error was largest when the volumes of parallel and series dead space were equal. The size of the parallel dead space in the model could be calculated from measurements of VDIG made before and after adding a series dead space of known volume. In 16 anesthetized dogs series and parallel dead space were quantitated using the multiple inert gas elimination technique with addition of known volumes of series dead space. In five normal dogs, the series and parallel dead space averaged 20% and 13% of the tidal volume, respectively. In eleven dogs with the left pulmonary artery occluded the parallel dead space averaged 26%. This method represents the first means of quantitating these two anatomically separate components of wasted ventilation.

Animals↗
PubMed1983

A computerized timing algorithm for determination of pulmonary tissue volume.

We developed a computerized method to measure pulmonary tissue volume (Vt) and capillary blood flow (Qc) that requires only a single interface for measurement of a soluble and an insoluble gas. The method uses a timing algorithm that replaces either a marker gas (C18O) or a volume signal. Gas concentrations are stored in digitized form. The data analysis consists of three parts: 1) initial and end-tidal samples found by using minima and maxima; 2) a timing algorithm derived from the end-tidal dead space method (ETDS, J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44: 782-795, 1978); and 3) calculations of Vt and Qc, also by the ETDS method. Both the timing and Vt and Qc agree well with the hand-calculated values, but the coefficient of variation of Vt is slightly improved (6 vs. 7% manually). We conclude that our computerized method is equivalent to the manual ETDS method, but it is faster and more accurate; in addition, it has the advantage of requiring only one interface without the use of expensive gases.

Capillaries↗
PubMed1982

Uneven gas mixing during rebreathing assessed by simultaneously measuring dead space.

To evaluate the rate of gas mixing in human lungs during rebreathing maneuvers used to measure pulmonary tissue volume (Vt) and pulmonary capillary blood flow (Qc), we devised a method to determine the dead space during rebreathing (VRD). Required measurements are initial concentration of a foreign inert insoluble gas in the rebreathing bag, first mixed expired concentration, equilibrated concentration, volume inspired, and volume of the first expired breath. In subjects breathing rapidly at 30 breaths/min with inspired volumes in excess of 2 liters, VRD had values three or more times greater than the predicted anatomical dead space (VD). Breath holding after the first inspiration progressively diminished VRD so that after 10-15 s, it approximately equaled predicted VD. VRD measured with helium was smaller than VRD measured with sulfur hexafluoride. The reported degree of uneven ventilation from gravitational forces in normal humans can account for only about one-third of the difference between VRD and VD. These findings support the concept that mixing by diffusion between peripheral parallel airways is incomplete at normal breathing rates in humans and can result in errors as high as 25% in Vt and Qc.

Humans↗
PubMed1978

Pulmonary tissue volume in dogs during pulmonary edema.

Pulmonary tissue volume (Vt) and pulmonary capillary blood flow (Qc) were measured in anesthetized dogs by analyzing end-expiratory concentrations of dimethyl ether (DME), acetylene (C2H2), and sulfur hexafluoride during a 30-s rebreathing maneuver. Vt was compared to the postmortem lung weight of control dogs and dogs with hemodynamic and nonhemodynamic (alloxan) pulmonary edema. Qc was compared to the cardiac output measured by dye dilution. A 100-ml increase in alveolar volume (VA) in the range of 1-2 liters resulted in a 9 +/- 3 ml increase in Vt. Vt measured at a VA of 1.9 liters measures 114 +/- 18% of the postmortem lung weight in 20 control dogs and in 6 dogs with moderate edema (lung weight < 250% of predicted). Vt measured only 53 +/- 14% of the lung weight in 11 dogs with more severe edema. DME and C2H2 gave the smae mean values of Vt, but the reproducibility of a series of 3-7 measurements was greater with DME (coefficient of variation was 5% with DME and 8% C2H2). Qc measured 96 +/ 15% of the cardiac output during the rebreathing maneuver, but the maneuver caused a 4-40% fall in the cardiac output. These data show that Vt determined by rebreathing DME is between 86% and 135% of the lung weight in dogs with pulmonary edema until the lung weight is greater than 250% of the predicted value.

Animals↗
PubMedDate not supplied

A Gaussian method to improve work-of-breathing calculations.

The work of breathing is a calculated index of pulmonary function in ventilated patients that may be useful in deciding when to wean and when to extubate. However, the accuracy of the calculated work of breathing of the patient (WOBp) can suffer from artifacts introduced by coughing, swallowing, and other non-breathing maneuvers. The WOBp in this case will include not only the usual work of inspiration, but also the work of performing these non-breathing maneuvers. The authors developed a method to objectively eliminate the calculated work of these movements from the work of breathing, based on fitting to a Gaussian curve the variable P, which is obtained from the difference between the esophageal pressure change and the airway pressure change during each breath. In spontaneously breathing adults the normal breaths fit the Gaussian curve, while breaths that contain non-breathing maneuvers do not. In this Gaussian breath-elimination method (GM), breaths that are two standard deviations from that mean obtained by the fit are eliminated. For normally breathing control adult subjects, GM had little effect on WOBp, reducing it from 0.49 to 0.47 J/L (n = 8), while there was a 40% reduction in the coefficient of variation. Non-breathing maneuvers were simulated by coughing, which increased WOBp to 0.88 (n = 6); with the GM correction, WOBp was 0.50 J/L, a value not significantly different from that of normal breathing. Occlusion also increased WOBp to 0.60 J/L, but GM-corrected WOBp was 0.51 J/L, a normal value. As predicted, doubling the respiratory rate did not change the WOBp before or after the GM correction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Variability, reproducibility, and data-collection time of pulmonary bedside monitoring.

Breath-by-breath pulmonary function testing at the bedside is now available both with special-purpose stand-alone equipment and with the new generation of ventilators. The authors studied the variability of, reproducibility of, and ideal length of data collection for nine indices of pulmonary function that may be useful for ventilatory management, weaning, and patient comfort. Work of breathing (as both J/L and J/min), pressure-time product, rapid shallow breathing index, respiratory time fraction, respiratory drive, change in esophageal pressure during inspiration, expiratory airway resistance, and dynamic compliance were measured in ten normal subjects and in eight patients being weaned from mechanical ventilation. All nine indices were reproducible when compared by paired t-test with two separate sets of data collected in normal subjects. Repeated measures in the normal subjects allowed calculation of 95% confidence intervals for the nine variables. There was no statistically significant difference between data collections of 5 minutes compared with those of 10 and 15 minutes. Breath-by-breath variability ranged from a coefficient of variation of 3% for the shallow breathing index in one patient to 131% for the work of breathing in J/min in another. Population variability ranged from values reported previously for other pulmonary parameters to nearly double for some parameters. The authors conclude that a 5-minute data collection time is sufficient to obtain reliable breath-by-breath data at the bedside. While taken together these indices may provide clinically useful information, their usefulness individually remains to be demonstrated because of their large variability.

Adult↗