Evaluation of the Pneupac Ventipac portable ventilator in critically ill patients

McCluskey A (1), Gwinnutt CL (2), Hardy L (1), Haslett R (2), Bowles B (2), Kishen R (2)
(1) Consultant Anaesthetist, Department of Anaesthesia, Stockport NHS Trust, Stepping Hill Hospital (2) Consultant Anaesthetist, Department of Anaesthesia, Salford Royal Hospital NHS Trust, Hope Hospital

Summary
We assessed adequacy of ventilation in 20 critically ill patients with multiple organ failure using a Pneupac ventiPAC portable ventilator and the effects on patients’ haemodynamic stability. Baseline data were recorded over 15 minutes for a range of respiratory, haemodynamic and oxygen transport variables during ventilation with a standard intensive care ventilator (Engstrõm Erica). Patients were then ventilated for 40 minutes using the portable ventilator. Finally, they were ventilated for a further 40 minutes using the standard intensive care ventilator. Heart rate, arterial and pulmonary artery pressures were recorded at 5 minute intervals throughout the study period. Cardiac index and other haemodynamic data derived from a pulmonary artery catheter were recorded at 20 minute intervals. Blood gas analysis was performed and oxygen transport data (oxygen delivery, oxygen consumption and physiological shunt) were calculated at the end of each of the three periods of ventilation. In general, no significant adverse effects of ventilation using the portable ventilator were observed for any of the variables studied. Arterial PO2 increased significantly during ventilation with the portable ventilator, reflecting the use of a higher inspired oxygen fraction during this part of the study. Oxygen consumption decreased significantly in one patient during ventilation by the portable ventilator although none of the other variables measured in this patient was altered. We concluded that ventilation of the critically ill patients using the Pneupac ventiPAC portable ventilator was safe, satisfactory and associated with minimal adverse effects on respiratory, haemodynamic and oxygen transport variables.

The CompPAC and PortaPAC portable ventilators bench tests and field experience.

Roberts MJ, Bell GT, Wong LSS
Nuffield Department of Anaesthesia, John Radcliffe Hospital, Headington, Oxford.

Summary
The military and some civilian rescue agencies have a requirement for portable ventilators in the anaesthetic, resuscitation and pre-hospital environment. This paper describes the compPAC and PortaPAC portable ventilators specifically designed to satisfy the military requirement for lightweight, robust and versatile equipment, which can also be used in a contaminated environment.

Organosphosphate Poisoning: Aspects of Emergency & Critical Care Management

Baker D.J.

Abstract
Poisoning from organophosphate (OP) compounds is a worldwide problem and particularly affects developing nations. Although the acute cholinergic features following intoxication by pesticide and other OP compounds are well recognized there is now increasing information, as a result of critical care management of cases, about longer-term effects including the changing nature of the neuromuscular paralysis, myopathic, neurological, pulmonary and cardiac problems. Effective prehospital and hospital emergency care involving life support and aggressive antidote therapy can result in a successful outcome even in severely poisoned cases.

'Out-of-hospital cardiac arrests' treated by the West Midlands Ambulance Service over a 2-year period.

Robinson JS, Davies MK, Johns BM, Edwards SN
West Midlands Ambulance Service NHS Trust, Dudley, UK.

Summary
We aimed to determine whether our results were any better or worse than other published reports and to examine the efficacy of the West Midlands Ambulance Service (WMAS) policy of applying cardiopulmonary resuscitation (CPR) and manual ventilation to all unwitnessed cardiac arrests in preference to immediate defibrillation. All cardiac arrests were studied from October 1994 to September 1996. In all unwitnessed arrests, crews undertook CPR and manually ventilated the lungs via a mask or an endotracheal tube with a bag and valve or a mechanical resuscitator using an FIO2 of 1 or 0.21 for at least 2 min before defibrillation was attempted. There were 3403 diagnosed cardiac arrests but, in these, the diagnosis was not certain. CPR and advanced life support (ALS) were applied in 3380 patients and return of spontaneous circulation (ROSC) was obtained in 554, giving a success rate of 16.4%. A total of 364 patients were accepted into hospital, 90 patients died in A&E but 274 patients were admitted to ICU/CCU. Seventy died within 24 h, 69 died after 24 h and 135 were discharged alive and well without cerebral damage. The final success to discharge rate was 49.27%. Of those discharged, 69 had a circulatory arrest period of more than 4 min but in only 10 was a bystander available to start CPR. The European Resuscitation Council Guidelines recommending immediate defibrillation for unwitnessed arrests are not supported by these results. The apparent lack of cerebral damage and the percentage success suggests that resuscitation considerations should be as brain orientated as they are heart orientated. The elapsed time periods reported challenge several shibboleths.

Testing of adult and paediatric ventilators for use in a magnetic resonance imaging unit.

Williams EJ, Jones NS, Carpenter TA, Bunch CS, Menon DK
Wolfson Brain Imaging Centre, School of Clinical Medicine, Box 65, Addenbrooke's Hospital, Cambridge CB2 2QQ, UK.

Summary
We have assessed the performance of a series of ventilators (modified versions of the ventiPAC, paraPAC and babyPAC ventilators; SIMS pneuPAC Ltd, Luton, UK) in a magnetic resonance imaging (MRI) scanning environment, with MR safety and compatibility issues being addressed. Following initial modifications to remove ferromagnetic components and replace them with MR-safe materials, all three ventilators performed well in a series of tests in static magnetic fields up to 2 T. Ventilator performance was unaffected by static fields, switching gradients or radio frequency fields within the MR suite. Furthermore, the devices produced no degradation of image quality when used during MR scanning. We discuss management strategies for the care of critically ill ventilated patients during MR procedures.

The CompPAC: A new approach to field and general emergency ventilation

Dr. D.J. Baker 
France

Summary
Organophosphates, in the form of nerve agents, remain a potent military hazard which has increased since the end of the Cold War. Sarin has recently been used in terrorists attacks in Japan.

OP agents affect airways through cholinergic receptors which gives rise to multiple attack on respiratory system. Traditional methods of management have used anticholinergic and antidode therapy but ventilatory and other advanced life support has been regarded as being possible only after decontamination.

Recently, however, this view has changed and ventilation is now possible in the contaminated zone, nusing compressed filtered air supplemented by low pressure oxygen. The CompPAC ventilator has been developed after collaboration with both the British and French armies and provides an automonous ventilator for use both in toxic and conventional medical resuscitation.

Comparison of automated and manual ventilation in a prehospital pediatric model.

Auble TE, Menegazzi JJ, Nicklas KA
Department of Emergency Medicine, University of Pittsburgh School of Medicine, PA 15213, USA.

Summary
OBJECTIVE: Portable transport ventilators (TV) and demand valves (DV) may be effective and easy-to-use alternatives to bag-valve (BV) for prehospitalventilation of adults. The purpose of the study was to determine whether such devices maintain arterial blood gases and airway pressures similar to those for BV in a pediatric swine model. METHOD: This study was a prospective, randomized, crossover design using immature swine (9.6 +/- 0.9 kg) to model ventilation in small children. Anesthetized, intubated, paralyzed, and cannulated animals were ventilated initially on standard mechanical hospital ventilation (HV). They were then assigned in random order to 10-minute intervals of ventilation using BV, TV, low-frequency jet ventilation (JV), and DV. Data were analyzed using repeated-measures ANOVA and Tukey multiple comparisons (alpha = 0.05). RESULTS: The PaO2 exceeded 90 mm Hg for all animal/ventilation combinations. Blood PaCO2 was lower for BV and DV than it was for TV, JV, or HV. In contrast, blood pH was higher for BV and DV than it was for TV, JV, or HV. Peak airway pressure was higher for BV than it was for HV, TV, or JV; it was lower for JV than it was for HV, TV, or BV. CONCLUSION: This animal model suggests that automated TV and JV may provide more effective ventilation of children than do manual BV or DV devices. Although promising, these findings require application in children under prehospital emergent conditions.

Ventilatory support in the field.

Johannigman JA, Branson RD
Department of Surgery, University of Cincinnati Medical Center, Ohio, USA.

Summary
Ventilatory support during cardiopulmonary resuscitation can be accomplished with an array of methods and devices. These run the gamut from expired air resuscitation, including mouth-to-mouth and mouth-to-mask, to the use of ventilators including ventilator-to-mask and ventilator-to-artificial airway techniques. Appropriate application of these techniques depends on the clinical situation, rescuer training, and availability of equipment. This article discusses the proposed standards of emergency ventilatory support, the advantages and disadvantages of the techniques and devices used, and current controversies surrounding this topic.

Evaluation of the Pneupac Ventipac portable ventilator: comparison of performance in a mechanical lung and anaesthetized patients.

McCluskey A, Gwinnutt CL
Department of Anaesthesia, Salford Royal Hospitals NHS Trust, Hope Hospital

Summary
The performance of the Pneupac Ventipac portable gas-powered ventilator was evaluated in two stages. The accuracy of delivery of the ventilator was assessed using a mechanical lung model at different combinations of compliance and airway resistance to simulate normal and diseased lungs. The performance of the ventilator was then assessed in 20 anaesthetized patients. The tidal volume delivered by the ventilator in airmix mode (nominal inspiratory oxygen fraction (FIO2) 0.45) was between -20 and +30% of the preset tidal volume with the mechanical lung model adjusted to normal adult values of compliance and airway resistance. The corresponding value with the ventilator set to deliver 100% oxygen was between -22 and -7% of the preset tidal volume. The performance of the ventilator decreased when either compliance was reduced or airway resistance was increased in the mechanical lung model; this effect was greater in airmix mode. Delivered tidal volume was between -19 and +12% of the present tidal volume in the group of anaesthetized patients using the ventilator in airmix mode. The ventilator was reliable and simple to use, and performance was within acceptable limits in the anaesthetized patients. However, we recommend that a means of verifying the adequacy of ventilation should always be used when transporting critically ill or anaesthetized patients with any portable ventilator, particularly when lung compliance or airway resistance may be abnormal.

Anesthetic and respiratory care for patients undergoing magnetic resonance imaging.

Article in Japanese

Watanabe H, Nagai H, Igarashi M, Namiki A
Department of Anesthesiology, Sapparo Medical University School of Medicine.

Summary
Simple and small ventilators, paraPAC and ventiPAC (pneuPAC) were used for anesthetic and respiratory care of patients undergoing magnetic resonance imaging (MRI), combined with or without MRI-compatible anesthetic machine, Ohmeda (R) Excell 210. These ventilators can be connected to Excell by the addition of a conventional below for ventilator (Ohmeda). The 1.5 tesla room shield type MRI machine (SIGNA, GE) did not interfere with the functions of the ventilator and anesthetic machine placed near the patient. Oscillometric blood pressure monitor (BP-203, Nippon Colin) and a gas and pulse oximetry (RGM, Ohmeda) monitor were used with 6 m extended lines for monitoring in the next room. Pulse oximetry signals were disturbed sometimes only by radiofrequency pulses for 3 to 10 minutes, but a pulse oximeter was one of the most useful monitors. Two representative cases were reported here. These ventilators can be used for almost all MRI cases with or without MRI compatible anesthetic machines.

The pneuPAC hyperbaric variant HB: a ventilator suitable for use within a one-man hyperbaric chamber.

Spittal MJ, Hunter SJ, Jones L
Anaesthetic Department, Princess Alexandra Hospital, Wroughton, Swindon, Wiltshire.

Summary
We describe the performance of the pneuPAC hyperbaric variant HB, a ventilator designed for use in a one-man hyperbaric chamber. The ventilator delivered minute volumes of 11-23 litre at 1 atm abs to 7.6-16 litre at 2.5 atm abs. The delivered minute volume may be controlled easily from outside the chamber by manipulation of the ventilator rate, 11.5-31 b.p.m.

Conv. Méd (1987), 6, 1 (article in French)

Gabé J.L., Metadier D., Marchadier C., Mercadal L., Abbeys J.M. Hervé C.

Summary
Emergency medical service’s physicians use 8 light ventilators to do the transportation of patients. 3 of these seem to be inadapted to the new principles to ventilate. From a specific form, a classification, which includes performances. O2 consumption, PEP and alarms data, is proposed by the authors.

The pneuPAC ventilator with new patient valve and air compressors.

Park GR, Manara AR, Bodenham AR, Moss CJ
Department of Anaesthesia, Addenbrooke's Hospital, Cambridge.

Summary
The pneuPAC Model 2-R pneumatic logic ventilator with a new air entrainment valve that offers the option of an FIO2 of 1.0 or 0.45 is described. Its robustness, portability, variable FIO2, choice of positive end expiratory pressure and pressure relief valves make it versatile and suitable for transporting critically ill patients, as well as for resuscitation use when adverse conditions may be encountered. Two new medical air compressors, one mains driven and the other battery powered, designed for use with the ventilator, are also described. The function of the ventilator with the new valve was assessed using a piped gas supply and then reassessed when powered by the compressors.