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Biomedical subjects

A Pesenti

Publications and source records attributed to A Pesenti.

At least 19 recordsLinked to original sources
PubMed1992

An interrupter technique for measuring respiratory mechanics and the pressure generated by respiratory muscles during partial ventilatory support.

We evaluated the airway occlusion maneuver as a method to estimate respiratory resistance, respiratory elastance and the pressure generated by respiratory muscles in ICU patients breathing in the PSV mode. The airflow was interrupted at selected flows or volumes during inspiration by a computer-driven rapid occlusion pneumatic valve. The airway occlusion was maintained for 2 to 3 s. From the airway pressure tracing we obtained various measurements of pressure. We then computed the pressure generated by the patient's inspiratory muscles. The method was validated by two different approaches in two groups of patients: the Pes and the CMV protocols. We conclude that the airflow interruption method can be used to measure basic respiratory mechanical parameters in PSV patients. The method also offers an opportunity to evaluate Pmusc,aw and the respiratory work performed by the patient.

Adolescent↗
PubMed1991

Body position changes redistribute lung computed-tomographic density in patients with acute respiratory failure.

Ten patients with parenchymal acute respiratory failure (ARF) underwent computed tomography (CT) scans while in the supine and prone positions. At equal levels of positive end-expiratory pressure, the authors measured the changes of CT density in dorsal and ventral basilar lung regions induced by the change of position as well as alterations of gas exchange. The level of venous admixture did not change with body position. The CT scan image of each lung was fractionated into ten levels from dorsal to ventral, each constituting 10% of the lung height. After measuring each lung fraction, the volume, the average CT number, its frequency distribution, and the expected normal value, we computed the lung tissue mass, the excess tissue mass, and the fraction of normally inflated tissue (excess tissue mass = amount of "tissue," which includes edema, cells, and blood in excess of the expected normal value). We also estimated the superimposed hydrostatic pressure on each lung region. We found that the excess lung tissue mass is independent of position. However, in patients in the supine position, lung CT density increased and regional inflation decreased from ventral to dorsal, suggesting progressive deflation of gas-containing alveoli along the gravity gradient. A similar ventral-dorsal deflation pattern occurred within 10 min in patients in the prone position. We conclude that the lung in patients with ARF behaves like an elastic body with a diffusely increased mass; dependent lung regions are compressed by the pressure of overlying structures.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1991

The effects of positive end-expiratory pressure on respiratory resistance in patients with the adult respiratory distress syndrome and in normal anesthetized subjects.

We investigated the effects of positive end-expiratory pressure (PEEP) upon respiratory resistance during mechanical ventilation in 21 subjects anesthetized for surgery (normal subjects) and in 11 patients with the adult respiratory distress syndrome (ARDS). We measured tracheal pressure (Ptr) near the end of the endotracheal tube through a 1.5-mm ID catheter and airflow (V) at 0, 5, and 10 cm H2O PEEP (normal subjects) and at 0, 5, 10, 15, and 20 cm H2O PEEP (patients with ARDS). We computed respiratory system static elastance (Estrs), maximal (Rrsmax) and minimal (Rrsmin) inspiratory resistance by the end-inspiratory occlusion method during constant-flow inflation. Rrsmin represents the ohmic respiratory resistance, whereas Rrsmax is Rrsmin plus the additional respiratory impedance caused by the stress adaptation phenomena of the respiratory system tissues and to time constant inhomogeneities between lung units (pendelluft). The difference (Rrsmax - Rrsmin) has been termed DRrs. We also computed expiratory resistance (Rrsexp) at preselected volume (50% of expiration; Rrsexp50) and flow (0.3 L/s; Rrsexp0.3) using the equation: Rrsexp = (Pelrs(t) - Ptr(t]/Flow(t), where elastic recoil pressure (Pelrs) at time t was computed as:Estrs . V(t) + PEEP, in which V(t) is the volume above end-expiratory volume at time t. We found that (1) at PEEP 0, expiratory resistances (Rrsexp50: 7.38 +/- 1.92 versus 5.35 +/- 1.97 cm H2O.L-1.s) and DRrs (3.08 +/- 1.9 versus 1.66 +/- 0.77 cm H2O.L-1.s) were significantly higher in the ARDS group than in the normal group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

The value of portable chest roentgenography in adult respiratory distress syndrome. Comparison with computed tomography.

In 17 patients with adult respiratory distress syndrome, we used data derived from computed tomographic (CT) scan densitometric analysis to validate the value of portable chest roentgenograms in objectively estimating the amount of pulmonary edema. Chest roentgenograms and CT scans were taken in the same ventilatory conditions (apnea at 10 cm H2O of positive end-expiratory pressure [PEEP]); blood gas samples and hemodynamic parameters were collected at the same time. Roentgenographic analysis was undertaken by independent observers using two standardized scoring systems proposed in the literature. CT scan analysis was performed using the CT number frequency distribution and the gas lung volume (measured by helium dilution technique) to estimate quantitatively the lung density, the lung weight, and the percentage of normally aerated and nonaerated tissue. Knowing the mean CT number of the pulmonary parenchyma in a group of normal subjects, we also inferred the ideal lung weight expected in the study population and computed the excess tissue mass as the difference between actual and ideal lung weight. Both the roentgenographic scoring systems showed direct correlation with the pulmonary impairment as detected by CT scan densitometric analysis (CT number, percentage of nonaerated tissue, lung weight, and excess tissue mass; p less than 0.01) and inverse relation with the percentage of normally aerated tissue (p less than 0.01). We also found a relationship between roentgenographic scores and the impairment in gas exchange as detected by shunt fraction (p less than 0.05). We conclude that standardized reading of portable chest roentgenograms by means of scoring tables is a valuable tool in estimating the amount of pulmonary edema in a patient with adult respiratory distress syndrome.

Absorptiometry, Photon↗
PubMed1990

Physiopathology and management of coagulation during long-term extracorporeal respiratory assistance.

Thrombohemorrhagic risk is one of the main limiting factors in extracorporeal circulation. We describe here our experience in managing some life-threatening hematological complications in 58 patients with acute respiratory failure treated with long-term extracorporeal assistance. These patients were studied by clinical and laboratory means to assess questions related to heparin monitoring, coagulation complications and bleeding incidence. We found that two clotting tests, activated partial thromboplastin time (APTT) and activated clotting time (ACT) can be easily used to assess the safety of anticoagulant treatment (therapeutic ranges: APTT from 55 to 95 sec and ACT from 170 to 220 sec). A certain degree of coagulation activation, despite heparin, was indicated by the constant finding of thrombin-antithrombin complexes, while fibrinolytic activation, measured as plasminogen activator activity, was confined to the time of bypass connection and was of no clinical consequence. Platelet function was always impaired without relation to the platelet loss. Disseminated intravascular coagulation (DIC) (13 episodes) and severe bleeding (11 episodes) were major complications. DIC was corrected with a good outcome for 8 of 13 patients, while severe bleeding was correlated with a poor outcome in 8 of the 11 patients, probably because of the severity of the underlying disease.

Adolescent↗
PubMed1989

Cerebral blood flow velocity and cerebrospinal fluid pressure after single bolus of propofol.

The effects of propofol on cerebral blood flow velocity, cerebrospinal fluid pressure, cerebral perfusion pressure and mean arterial pressure were studied during induction in 25 patients scheduled for elective craniotomy. Premedication consisted of only atropine sulphate 0.007 mg/kg (im) 45 min before induction. Measurements were made or derived at time zero and 1, 2, 3, 4 and 5 min after an induction dose of propofol (2.5 mg/kg). Patients were retrospectively stratified into two groups, according to cerebrospinal pressure basal values: (i) lower than 10 mmHg (10 pts) and (ii) higher than 10 mmHg (15 pts). Cerebral blood flow velocity, measured by transcranial Doppler, fell in all the patients, but the reduction was significant at 1, 2, 3 and 4 min only in the group with high CSF pressure, while it never reached the critical value of 10 cm/s. Cerebrospinal fluid pressure and mean arterial pressure decreased in both groups of patients and the fall reached a statistical significance at 1 and 2 min in the group with higher baseline CSF pressure, only at 1 min: a parallel decrease of CPP was recorded, but it was not significant. Thus propofol decreases CSF pressure without hazardous effects on cerebral blood velocity and on cerebral perfusion pressure and seems to be a suitable anaesthetic agent in controlling high cerebrospinal fluid pressure in neuroanaesthesia.

Adult↗