Non-invasive assessment of lung elastance in patients with acute respiratory distress syndrome.

BACKGROUND: Chest wall mechanics can be abnormal in patients with acute respiratory disease syndrome (ARDS). Therefore, partitioning respiratory system between lungs and chest wall at the bedside is useful to optimize ventilator settings. A non-invasive method for assessing lung elastance (EL), called lung barometry, was previously described on an animal model. METHODS: This prospective study was designed to compare EL assessed by lung barometry (ELLB) versus esophageal pressure (ELPeso). In sedated, paralyzed patients, PEEP was progressively increased from 5 to 40cmH2O then decreased from 40 to 5cmH2O by step of 5cmH2O every two minutes. ELLB was assessed for each step as the ratio between the change in PEEP and the induced end-expiratory lung volume change measured by direct spirometry. ELPeso was calculated from esophageal pressure measurement at each PEEP. EL and the ratio between EL and respiratory system elastance (ERS) calculated with the two methods were compared. RESULTS: Twenty six adult patients with early onset moderate or severe ARDS were included. There was a linear correlation between ELLB and ELPeso during the increase and decrease of PEEP (R²=0.26 and 0.42, respectively). Concordance using Bland and Altman method demonstrated bias and large limits of agreement during the increase (-0.5 cmH2O/L; -25 to 24 cmH2O/L) and during the decrease in PEEP (-0.3 cmH2O/L; -21 to 20 cmH2O/L). There were no linear correlation between ELLB/ERS and ELPeso/ERS during the increase and the decrease of PEEP (R²=0.00; R²=0.00, respectively). CONCLUSION: In ARDS patients, lung barometry method cannot be used instead of the esophageal pressure measurement to assess EL.

[Management of severe post-partum hemorrhage using selective arterial embolization]. / Prise en charge des hémorragies graves du post-partum par embolisation artérielle sélective.

OBJECTIVES: To evaluate the efficacy and safety of uterine embolization in the management of intractable post-partum hemorrhage. MATERIALS AND METHODS: From July 1994 to December 1997, 51 patients with severe primary (n = 37) or secondary (n = 14) post-partum hemorrhage were treated by arterial uterine embolization. In all cases, hemostatic uterine embolization was performed because of persistent hemorrhage despite adapted obstetrical measures and early introduction of uterotonic drugs. RESULTS: In case of immediate post-partum hemorrhage, primary and secondary success rates were 89% et 97% respectively. In one patient with placenta accreta, delayed hysterectomy was necessary. One patient died of associated cerebral hemorrhage while vaginal bleeding had stopped. The success rate reached 100% in case of secondary post-partum hemorrhage. CONCLUSION: Emergency arterial embolization is a safe and effective means of controlling severe post-partum hemorrhage after failure with medical treatment.

Pulmonary air trapping during two-lung and one-lung ventilation.

OBJECTIVE: Evaluation of the magnitude of pulmonary air trapping during routine thoracic surgery and single-lung transplantation. DESIGN: Prospective study on consecutive patients. SETTING: Single institution, university hospital. PARTICIPANTS: Sixteen patients with no or moderate obstructive lung disease undergoing routine thoracic surgery (group 1), six patients with severe emphysema (group 2), and six patients with severe fibrosis (group 3) undergoing single-lung transplantation. INTERVENTIONS: Occlusion maneuver timed at the end of expiration to measure auto-positive end-expiratory pressure (auto-PEEP) and trapped volume (delta FRC). The maneuver was performed during two-lung ventilation in supine (2LV supine) and lateral decubitus (2LV lateral) positions and during one-lung ventilation (OLV) in lateral decubitus position. At the same time, airway pressures and PaO2 measurements were performed. MEASUREMENTS AND MAIN RESULTS: In group 1, consistent values of auto-PEEP and delta FRC occurred only during OLV: 4.8 +/- 2.5 cm H2O and 109 +/- 61 mL (mean +/- standard deviation). In group 2, auto-PEEP and delta FRC values were 11.7 +/- 6.9 cm H2O and 355 +/- 125 mL during 2LV supine, 8.8 +/- 5.7 cm H2O and 320 +/- 122 mL during 2LV lateral, and 15.9 +/- 3.9 cm H2O and 284 +/- 45 mL during OLV. In group 3, pulmonary air trapping was low. For the three groups together, auto-PEEP and delta FRC (p < 0.0001) related inversely to the ratio of forced expired volume in 1 second (FEV1) to forced vital capacity (FVC) expressed in percent (FEV1/FVC%) during OLV. In contrast, there was no correlation between PaO2 and auto-PEEP or delta FRC. CONCLUSION: Pulmonary air trapping must be suspected in patients with no or moderate obstructive lung disease during OLV and in those with severe obstructive disease as soon as 2LV is initiated.

Inhaled nitric oxide fraction is influenced by both the site and the mode of administration.

OBJECTIVE: Inhaled nitric oxide (NO) can be delivered continuously or sequentially (= during inspiration) at different locations of the ventilation circuit. We have tested the influence of locations, modes of NO administration and the ratio of the inspiratory time over the respiratory cycle time (I/I + E ratio) on the accuracy of NO fractions, delivered by 2 devices: Opti-NO and Flowmeter. METHODS: We used a simplified lung model consisting of a ventilation circuit with a Y piece, a tracheal tube, a 150 ml dead-space volume and a 5 liter balloon. Three fractions (3, 6, 9 ppm) were administered continuously or sequentially, in controlled volume, in 4 different sites on the inspiratory branch above the Y piece: i) just after the water trap, ii) just before the Y piece; below the Y piece: iii) just after the Y piece, iv) into the endotracheal tube. In addition, different I/I + E ratios (25, 33, 50, 80%) were studied. The delivered NO fractions were measured in the balloon by chemiluminescence (CLD 700, Ecophysics). A linear regression analysis was used to test the relationship between administered and measured NO fractions for the 3 fractions (3, 6 and 9 ppm) in sequential and continuous modes. Intercept values were compared to zero and slopes to the identity line. RESULTS: When NO was administered in the continuous mode upstream the Y piece, NO fractions measured in the balloon corresponded to the administered fractions. In contrast, below the Y piece, the measured NO fractions were significantly lower than the administered NO fractions. In the sequential mode, above and below the Y piece, the delivered NO fractions were within the manufacturer's range. CONCLUSIONS: For the continuous NO delivery, locations above the Y piece are mandatory. However, locations below the Y piece imposes a sequential system, which can also be used for the sites located above the Y piece.

The effects of inhaled nitric oxide and its combination with intravenous almitrine on Pao2 during one-lung ventilation in patients undergoing thoracoscopic procedures.

UNLABELLED: The aim of this study was to assess whether hypoxemia during one-lung ventilation (OLV) can be prevented by inhaled nitric oxide (NO) (Part I) or by its combination with intravenous (IV) almitrine (Part II) in 40 patients undergoing thoracoscopic procedures. In Part I, 20 patients were divided into two groups: one received O2 (Group 1) and one received O2/NO (Group 2). In Part II, 20 patients were divided into two groups: one received O2 (Group 3) and one received O2/NO/almitrine (Group 4). In Groups 2 and 4, NO (20 ppm) was administered during the entire period of OLV, and almitrine was continuously infused (16 microg x kg(-1) x min[-1]) in Group 4. Arterial blood gases were measured during two-lung ventilation with patients in the supine position, after positioning in the lateral decubitus position, and then every 5 min for a 30-min period during OLV. During OLV, Pao2 values decreased similarly in Groups 1 and 2. After 30 min of OLV, the mean Pao2 values in Groups 1 and 2 were 132 +/- 14 mm Hg (mean +/- sem) and 149 +/- 27 mm Hg (not significant [NS]), and the Pao2 value was less than 100 mm Hg in four patients in Group 1 and five patients in Group 2. Pao2 values were greater in Group 4 than in Group 3 after 15 and 30 min of OLV. After 30 min of OLV, the mean Pao2 values were 146 +/- 16 mm Hg in Group 3 and 408 +/- 33 mm Hg in Group 4 (P < 0.001). Pao2 was less than 100 mm Hg during OLV (NS) in four patients in Group 3 and in no patient in Group 4. We conclude that NO inhalation alone has no effect on Pao2 evolution during OLV, although its combination with IV almitrine limits the decrease of Pao2 during OLV. This beneficial effect of NO/almitrine could be attributed to an improvement in ventilation-perfusion relationships. IMPLICATIONS: Decrease in oxygenation during one-lung ventilation is quite common. Our study showed that inhaled nitric oxide alone did not influence Pao2 evolution. We then tried adding intravenous almitrine to nitric oxide with amazingly good results on Pao2. This nonventilatory technique should be of great use during special thoracic acts, such as thoracoscopic procedures.

Mechanical and energetic effects of cromakalim on guinea pig left ventricular papillary muscle.

The mechanical and energetic effects of the adenosine triphosphate-sensitive potassium channel opener cromakalim at 50 microM and 100 microM were determined on guinea pig left ventricular papillary muscles and compared with those of low calcium concentration (n = 9 in each group). Both concentrations of cromakalim induced a negative inotropic effect (decrease in maximum shortening velocity at preload only and maximum extent of muscle shortening at preload only, P < .01 and P < .001 at 50 and 100 microM, respectively; maximum isometric active force normalized per cross-sectional area during the isometric twitch, P < .001; positive peak of the isometric force derivative normalized per cross-sectional area, P < .001) and a negative lusitropic effect (decrease in maximum lengthening velocity at preload only and negative peak of the isometric force derivative normalized per cross-sectional area, P < .01 and P < .001 at 50 and 100 microM, respectively). At 100 microM, the decrease in relaxation parameters was more marked than that in contraction parameters under isotonic conditions, as shown by the decrease in the slope of the relationship between peak lengthening velocity and maximum extent of muscle shortening (P < .01); this result reflects an intrinsic negative relaxant effect. No relaxant effect was found under isometric conditions at either concentration. The mechanical effects of low calcium were similar to those of cromakalim 100 microM, which suggests that the drug acted mainly by reducing the cellular calcium entry. Despite the negative mechanical effect of cromakalim, mechanical efficiency was preserved. This could partly explain the cardioprotective effect of cromakalim during ischemia.