Elastic pressure-volume curves of the respiratory system reveal a high tendency to lung collapse in young pigs

Objective: To study pressure-volume (P/V) curves over a wide pressure and volume range in pigs.¶Design: Dynamic and static P/V curves (P_dyn/V and P_st/V) and compliance of the respiratory system were studied. The effects of recruitment, positive end-expiratory pressure (PEEP) and body position were analysed.¶Setting: Research animal laboratory.¶Materials: Seven anaesthetised, paralysed and ventilated healthy pigs of 21 kg.¶Measurements: P/V curves up to a pressure of about 40 cmH₂O were recorded with a computer-controlled ventilator. P_st/V curves were obtained with the static occlusion method and P_dyn/V curves during an insufflation at a low, constant flow rate.¶Results: P_dyn/V recording showed a complex pattern. During the insufflation compliance increased, fell, increased and fell again. A 2nd ¶P_dyn/V recording immediately following the 1st one was displaced towards higher volumes and showed only one maximum of compliance. The difference between the two curves reflected: (1) lung collapse during a period of 5 min of ventilation at zero end-expiratory pressure (ZEEP) following a recruitment manoeuvre, (2) recruitment during the measurement of the 1st P_dyn/V curve. These observations were similar in the supine and in the left lateral position. After ventilation at PEEP, 4 cmH₂O, the signs of collapse and recruitment were reduced. It was confirmed that PEEP offers a partial protection against collapse. P_st/V curves showed higher volumes and higher compliance values compared to P_dyn/V curves. This reflects the influence of viscoelastance on P_dyn/V curves.¶Conclusion: The study demonstrates a particularly strong tendency to lung collapse in pigs.     

Aspiration of dead space allows normocapnic ventilation at low tidal volumes in man

Objective: Aspiration of dead space (ASPIDS) improves carbon dioxide (CO₂) elimination by replacing dead space air rich in CO₂ with fresh gas during expiration. The hypothesis was that ASPIDS allows normocapnia to be maintained at low tidal volumes (V_T). Design: Prospective study. Setting: Adult intensive care unit in a university hospital. Patients: Seven patients ventilated for neurological reasons were studied. All patients were clinically and haemodynamically stable and monitored according to clinical needs. Interventions: ASPIDS implies that, during expiration, gas is aspirated through a catheter inserted in the tracheal tube. Simultaneously, a compensatory flow of fresh gas is injected into the inspiratory line. ASPIDS was achieved with a computer/ventilator system controlling two solenoid valves for aspiration and injection. Results: At the basal respiratory rate of 12.6 breaths min^–1, with ASPIDS V_T decreased from 602 to 456 ml, as did the airway pressures to a corresponding degree. PaCO₂ and PaO₂ remained stable. At a frequency of 20 breaths min^–1, with ASPIDS V_T was further reduced to 305 ml with preserved normocapnia. ASPIDS did not interfere with the positive end-expiratory pressure (PEEP) level. No intrinsic PEEP developed. All patients remained stable. No haemodynamic or other side effects of ASPIDS were noticed. Conclusion: The results of this study suggest that ASPIDS may be a useful and safe modality of mechanical ventilation that limits alveolar pressure and minute ventilation requirements while keeping PaCO₂ constant. Received: 21 December 1998 Final revision received: 28 April 1999 Accepted: 3 May 1999     

The maltose-inducible 43 kDa major outer membrane protein in Vibrio cholerae is immunogenic and common to different isolates

We have previously demonstrated the presence of a maltose-inducible major outer membrane protein of 43 kDa in an El Tor Inaba strain of Vibrio cholerae. The occurrence of similar proteins was examined in several isolates of V. cholerae 01. The results indicate that the 43 kDa protein is common to all of the isolates as evidenced by Western blotting analysis with antiserum raised against this protein. The 43 kDa protein was maltose-inducible in most isolates although some strains exhibited a constitutive production of the protein. This protein was present also on V. cholerae 01 organisms harvested directly from the small intestine of rabbits with experimental cholera and it gave rise to specific antibodies after immunization with in vivo grown vibrios.     

Treatment of drug-induced agranulocytosis with recombinant GM-CSF

A 53-year male patient, treated for rheumatoid arthritis with sulphasalazine, developed a total agranulocytosis. When this state had prevailed for at least 10 d no bone marrow granulocyte progenitor cells were detectable. Intravenous GM-CSF treatment was initiated 5 d later, and the patient recovered within the next 6 d. GM-CSF treatment for severe agranulocytosis deserves further investigation.     

Dual-photon absorptiometry for determination of bone mineral content in the calcaneus with correction for fat

A portable dual-photon absorptiometry system for the determination of the bone mineral content BMC in vivo in the calcaneal bone is described. With knowledge of the total thickness of the heel at the measuring point the BMC can be corrected for fat and lean soft tissue. The system is capable of measuring the BMC in the heel bone with a precision of 1.2% in vitro and 1.8% in vivo at an absorbed dose to the skin of 0.2 mSv.     

Numerical analysis of pressure and flow pulsations in a segment of the arterial tree

The arterial blood pressure and the rate of volume pulsations were measured experimentally as functions of time for a segment of the human arm. Using these curves and a type of identification program, common in control engineering, a mathematical model was calculated for the arterial tree included in the segment. This mathematical model led to the construction of an electrical analogue circuit for simulating the time-dependence of the rate of volume pulsations on the arterial pressure. In both cases the results show a close agreement between the simulated curves and the physiological curves determined experimentally. The inertia of blood and vessels is shown to be negligible, while non-linear compliances must be included when dealing with wide pressure ranges.