Responsiveness to intravenous administration of salbutamol in chronic obstructive pulmonary disease patients with acute respiratory failure.

OBJECTIVE: In chronic obstructive pulmonary disease (COPD) patients with acute respiratory failure (ARF), bronchodilating agents administered by inhalation have, in general, little effect on dynamic hyperinflation and concurrent static intrinsic positive end-expiratory pressure (PEEPi,st). Since in COPD the severely obstructed segments of the lung may not be reached by inhaled medication, we reasoned that drug efficiency may be enhanced by intravenous administration of the agent. DESIGN: Physiological study. SETTING: Two four-bed surgical-medical ICUs of a university hospital. PATIENTS: Fourteen COPD patients were studied within 36 h from the onset of ARF. MEASUREMENTS AND RESULTS: Static compliance (Cst,rs), minimal (Rmin,rs) and additional (DeltaRrs) resistance of the respiratory system, and PEEPi,st were measured before and after intravenous administration of salbutamol. All patients had limitation of air flow before and after salbutamol administration. On average, after salbutamol there was a small, though significant, decrease in Rmin,rs (-9%), DeltaRrs (-12%) and PEEPi,st (-8%). CONCLUSION: The changes in resistance and PEEPi,st after intravenous administration of salbutamol were too small to be of clinical significance.

Predictors of weaning outcome in chronic obstructive pulmonary disease patients.

Several threshold values for predicting weaning outcome from mechanical ventilation have been proposed. These values, however, have been obtained in nonhomogeneous patient populations. The aim of the present study was to determine the threshold values in chronic obstructive pulmonary disease (COPD) patients and compare them to those reported for nonhomogeneous patient populations. The initial weaning trial included 81 COPD patients. Fifty-three of them underwent a successful weaning trial, whereas 28 failed it. The latter were enrolled into the present investigation, and were restudied during a subsequent successful trial. The weaning indices used were those reported in the literature. The threshold values obtained were within 10% of those reported for a nonhomogeneous patients population only for tidal volume and effective compliance. The classification error was <20% for maximal inspiratory pressure (MIP), occluded inspiratory pressure swing (deltaPI)/MIP, rapid and shallow breathing (respiratory frequency/tidal volume), and compliance, rate, oxygenation, pressure index (CROP), whereas the area under the receiver operating characteristic curves was >0.9 only for deltaPI/MIP and CROP. In conclusion, the threshold values obtained in chronic obstructive pulmonary disease patients who failed the first weaning attempt differed from those previously reported. Although a gold standard weaning index is not available for chronic obstructive pulmonary disease patients, the occluded inspiratory pressure swing/ maximal inspiratory pressure and compliance, rate, oxygenation, pressure index may be candidates for such a role.

Respiratory mechanics during and after anaesthesia for major vascular surgery.

To evaluate the effects of major vascular surgery on respiratory mechanics, 11 patients undergoing general anaesthesia for abdominal aortic surgery were studied. Before aortic cross-clamping, chest wall elastance and resistance both increased (by 126% and 58%, respectively) when surgical retractors were placed. After aortic cross-clamping, lung elastance increased by 29%, accompanied by a decrease in cardiac index (22%) and an increase in pulmonary (17%) and systemic (15%) vascular resistance. After aortic unclamping, lung elastance decreased, although it remained higher than baseline values (by 12%). All cardiovascular variables returned to the values obtained before aortic cross-clamping.

Respiratory effects of pharingeal gas insufflation in patients with chronic obstructive pulmonary disease.

OBJECTIVE: To evaluate the effects of pharyngeal gas insufflation (PGI) in clinically stable patients with chronic obstructive pulmonary disease (COPD). DESIGN: Prospective study in humans. SETTING: Department of Intensive Care Medicine at a University Hospital. PATIENTS: Seven clinically stable COPD patients. INTERVENTION: Pharyngeal dry fresh air insufflation (PGI) with a continuous flow rate of 4 L/min was given via a nasal catheter placed into the oropharynx. Baseline measurements with zero flow were made at the beginning and end of the test. After an equilibration period of 1 h at each stage, arterial blood samples were analyzed every 5 min until PaCO2 variation less than 5% confirmed the achievement of a steady state. Thereafter expiratory flow signal and expiratory gas were collected over a period of 3 min and arterial blood was sampled after 1'30" and 2'30" from the beginning of the test for the measurement of effective expiratory volume (VE eff), respiratory rate (RR), tidal volume (VT), dead space fraction (VD/VT), dead space (VD), alveolar ventilation (VA), total expiratory time (TE min), and PaCO2, respectively. RESULTS: During PGI VT, VD/VT, VD and VE eff fell significantly from baseline values, RR was slightly reduced and VA, TE min and PaCO2 remained unchanged throughout the study. CONCLUSIONS: Although in our study the effect of PGI on VD could be overestimated since our device for expiratory gas flow measurement and collection significantly enlarged the anatomical dead space receiving the washout effect of the fresh gas insufflation, under the experimental conditions PGI produces a reduction in VD and VD/VT, and, as a consequence, a significative reduction in respiratory requirements in clinically stable COPD patients. If confirmed in clinical settings, potential advantages of PGI could include: a) reduction of the work of breathing in patients with intact neuro-respiratory coupling; b) minimizing hypercapnic side effects of oxygen therapy often seen in COPD patients.

Additional inspiratory resistance imposed by the laryngeal mask airway: in vitro versus in vivo comparison.

The present study was designed: (a) to compare the additional inspiratory laryngeal mask airway (LMA) resistance measured in vitro during simulated ventilation and in vivo in five anaesthetised and mechanically ventilated patients; and (b) to evaluate the resistive pressure drop along the length of the LMA. After the differential pressure across the mask was measured, the pressure-flow relationship was characterised by Rohrer's equation and in vitro and in vivo resistance was calculated. Thereafter, the distal pressure measuring point was moved along the length of the LMA and differential pressure was measured at each point under in vitro and in vivo conditions. Values for resistance were approximately twice as great in vivo as those obtained in vitro, with most of the resistive pressure drop occurring across the vertical bars, especially when measured in vivo. We conclude that in vivo positioning of the LMA significantly increases resistance because of the configurational changes occurring when the LMA is in situ.

[Survival in intensive care of patients with chronic obstructive bronchopneumopathy and acute respiratory failure undergoing mechanical ventilation. Retrospective study]. / La sopravvivenza in Terapia Intensiva di pazienti con broncopneumopatia cronica ostruttiva e insufficienza respiratoria acuta sottoposti a ventilazione meccanica. Studio retrospettivo.

OBJECTIVE: To collect valuable informations for the evaluation of the patients' clinical evolution and to perform a cost-effectiveness analysis on the utilization of resources in the management of patients with chronic obstructive pulmonary disease (COPD) undergoing mechanical ventilation (MV) for acute respiratory failure (ARF). SETTING: General ICU. University Hospital. PATIENTS: 87 BPCO patients (mean age: 69.6 +/- 8.5) undergoing MV for ARF due to non surgical or traumatic events, for a total of 108 consecutive ICU admissions between January 1983 and December 1993. METHODS: Retrospective study in which the following data were collected: severity of the underlying chronic respiratory disease before the occurrence of ARF. For this aim patients have been divided into five classes (O-IV) according with ATS classification of dyspnea; causes of ARF; SAPS score; TISS score; OMEGA score; complications occurred in ICU; duration of MV; duration of stay in ICU; ICU and hospital outcome. RESULTS: In 48 cases (44.4%) clinical history was positive for a severe dyspnea (classes III-IV). Slight airway flogosis or infection were responsible of ARF in 78 cases; pneumonia was present in 24 cases while in 6 cases ARF was due to congestive heart failure. The study population was divided into two groups according with outcome. No statistically significant difference was observed in mean SAPS and TISS scores between the two groups (12.5 +/- 3 vs 13 +/- 4.8 and 18.4 +/- 2.3 vs 19 +/- 4.2). Mean OMEGA score was 155 +/- 11.7 (ES). With reference to ICU outcome the utilization rate or resources was 72.15% with a mean loss of resources of 43.2. Compli-cations were manly due to airway infection (16 cases) which was responsible in one case of the patient's death. Overall incidence of complications was relatively low and five of them led to patients' death in ICU. Mean duration of MV did not differ between the two groups (13.4 +/- 11.7 vs 14.3 +/- 11.7) but it was significantly longer in those patients whose clinical history was positive for severe dyspnea (classes III and IV) than in patients without this report (16.6 +/- 14.9 vs 10.9 +/- 6.9; p < 0.05). Mean stay in ICU did not differ significantly between survivors and non-survivors (21.4 +/- 18.6 vs 19.7 +/- 13). ICU mortality rate was 6.48% (7 patients) and hospital mortality rate was 20.3% (22 patients). CONCLUSIONS: Our results demonstrate that hospital outcome in COPD patients with ARF requiring mechanical ventilation is quite good. Prolonged mechanical ventilation and--severity of underlying chronic respiratory disease do not affect significatively the prognosis. The high costs of the treatment of these patients are counterbalanced by a good efficiency of utilization of resources and appreciable clinical results.