Manual and ventilator hyperinflation parameters used by intensive care physiotherapists in Sri Lanka: An online survey

INTRODUCTION

Hyperinflation is a common procedure to clear secretion, increase lung compliance and enhance oxygenation in mechanically ventilated patients. Hyperinflation can be provided as manual hyperinflation (MHI) or ventilator hyperinflation (VHI), where outcomes depend upon the methods of application. Hence it is crucial to assess the application of techniques employed in Sri Lanka due to observed variations from recommended practices.

OBJECTIVE

This study is aimed to evaluate the application and parameters used for MHI and VHI by physiotherapists in intensive care units (ICUs) in Sri Lanka.

METHODOLOGY

An online survey was conducted among physiotherapists who are working in ICUs in Sri Lanka using WhatsApp groups and other social media platforms.

RESULTS

A total of 96 physiotherapists responded. The survey comprised of three sections to obtain information about socio-demographic data, MHI practices and VHI practices. Most of the respondents (47%) worked in general hospitals and 74% of participants had a bachelor's degree in physiotherapy; 31.3% had 3-6 years of experience; 93.8% used hyperinflation, and 78.9% used MHI. MHI was performed routinely and as needed to treat low oxygen levels, abnormal breath sounds, and per physician orders while avoiding contraindications. Self-inflation bags are frequently used for MHI (40.6%). Only a few participants (26%) used a manometer or tracked PIP. In addition to the supine position, some participants (37.5%) used the side-lying position. Most physiotherapists followed the recommended MHI technique: slow squeeze (57.3%), inspiratory pause (45.8%), and quick release (70.8%). VHI was practised by 19.8%, with medical approval and it was frequently performed by medical staff compared to physiotherapists. Treatment time, number of breaths, and patient positioning varied, and parameters were not well-defined.

CONCLUSION

The study found that MHI was not applied with the recommended PIP, and VHI parameters were not identified. The study indicates a need to educate physiotherapists about current VHI and MHI practice guidelines.

An Update on Cardiorespiratory Physiotherapy during Mechanical Ventilation

Physiotherapists are integral members of the multidisciplinary team managing critically ill adult patients. However, the scope and role of physiotherapists vary widely internationally, with physiotherapists in some countries moving away from providing early and proactive respiratory care in the intensive care unit (ICU) and focusing more on early mobilization and rehabilitation. This article provides an update of cardiorespiratory physiotherapy for patients receiving mechanical ventilation in ICU. Common and some more novel assessment tools and treatment options are described, along with the mechanisms of action of the treatment options and the evidence and physiology underpinning them. The aim is not only to summarize the current state of cardiorespiratory physiotherapy but also to provide information that will also hopefully help support clinicians to deliver personalized and optimal patient care, based on the patient's unique needs and guided by accurate interpretation of assessment findings and the current evidence. Cardiorespiratory physiotherapy plays an essential role in optimizing secretion clearance, gas exchange, lung recruitment, and aiding with weaning from mechanical ventilation in ICU. The physiotherapists' skill set and scope is likely to be further optimized and utilized in the future as the evidence base continues to grow and they get more and more integrated into the ICU multidisciplinary team, leading to improved short- and long-term patient outcomes.

Selecting the best ventilator hyperinflation technique based on physiologic markers: A randomized controlled crossover study

BACKGROUND

Ventilator hyperinflation (VHI) is effective in improving respiratory mechanics, secretion removal, and gas exchange in mechanically ventilated subjects; however, there are no recommendations for the best ventilator settings to perform the technique.

OBJECTIVE

To compare six modes of VHI, concerning physiological markers of efficacy and safety criteria to support the selection of optimal settings.

METHODS

Thirty mechanically ventilated patients underwent six modes of VHI in a randomized order. The delivered volume, expiratory flow bias criteria, overdistension, patient-ventilator asynchronies and hemodynamic variables were assessed during the interventions.

RESULTS

Volume-controlled ventilation with inspiratory flow of 20 lpm (VC-CMV20) and pressure support ventilation (PSV) achieved the best effectiveness scores (P < 0.05). The target peak pressure of 40 cmH₂O was associated with a high incidence of overdistension. PSV showed a lower incidence of patient-ventilator asynchronies.

CONCLUSIONS

The modes VC-CMV20 and PSV are the most effective for VHI. Alveolar overdistension and patient-ventilator asynchronies must be considered when applying VHI.

Physiotherapy in the neurotrauma intensive care unit: A scoping review

PURPOSE

This scoping review summarizes the literature on the safety and effectiveness of physiotherapy interventions in patients with neurological and/or traumatic injuries in the intensive care unit (ICU), identifies literature gaps and provides recommendations for future research.

MATERIALS AND METHODS

We searched five databases from inception to June 2, 2018. We included published retrospective studies, case studies, observation and randomized controlled trials describing physiotherapy interventions in ICU patients with neurotrauma injuries. Two reviewers reviewed the databases and independently screened English articles for eligibility. Data extracted included purpose, study design, population (s), outcome measures, interventions and results. Thematic analysis and descriptive numerical summaries are presented by intervention type.

RESULTS

12,846 titles were screened and 72 met the inclusion criteria. Most of the studies were observational studies (44 (61.1%)) and RCTs (14 (19.4%)). Early mobilization, electrical stimulation, range of motion, and chest physiotherapy techniques were the most common interventions in the literature. Physiotherapy interventions were found to be safe with few adverse events.

CONCLUSIONS

Gaps in the literature suggest that future studies require assessment of long term functional outcomes and quality of life, examination of homogenous populations and more robust methodologies including clinical trials and larger samples.

Respiratory physiotherapy in intensive care unit: Bibliographic review

INTRODUCTION AND AIMS

Patients in intensive care unit are susceptible to complications due to different causes (underlying disease, immobilisation, infection risk…) The current main intervention in order to prevent these complications is respiratory physiotherapy, a common practice for nurses on a daily basis. Therefore, we decided to carry out this bibliographic review to describe the most efficient respiratory physiotherapy methods for the prevention and treatment of lung complications in patients in intensive care, taking into account the differences between intubated and non-intubated patients.

METHODOLOGY

The bibliographic narrative review was carried out on literature available in Pubmed, Cinahl and Cochrane Library. The established limits were language, evidence over the last 15 years and age.

RESULTS

Techniques involving lung expansion, cough, vibration, percussion, postural drainage, incentive inspirometry and oscillatory and non-oscillatory systems are controversial regarding their efficacy as respiratory physiotherapy methods. However, non-invasive mechanical ventilation shows clear benefits. In the case of intubated patients, manual hyperinflation and secretion aspirations are highly efficient methods for the prevention of the potential complications mentioned above. In this case, other RP methods showed no clear efficiency when used individually.

DISCUSSION AND CONCLUSIONS

Non-invasive mechanical ventilation (for non-intubated patients) and manual hyperinflation (for intubated patients) proved to be the respiratory physiotherapy methods with the best results. The other techniques are more controversial and the results are not so clear. In both types of patients this literature review suggests that combined therapy is the most efficient.

Interventions during Donor Care before Lung Transplantation

Improvement in the ratio of PaO2 to the fraction of inspired oxygen and treatment of pulmonary infections in donors have been cited as important goals for improving lungs before implantation and restoring marginal lungs to the donor pool. Likewise, improving donor PaO2 is often critical for other organs during donor care. The common physiological mechanisms responsible for hypoxemia are ventilation/perfusion mismatching, abnormal oxygen diffusion, and hypoventilation. These mechanisms are discussed and treatment options are considered.

Acute effects of physiotherapeutic respiratory maneuvers in critically ill patients with craniocerebral trauma

OBJECTIVE

To evaluate the effects of physiotherapeutic respiratory maneuvers on cerebral and cardiovascular hemodynamics and blood gas variables.

METHOD

A descriptive, longitudinal, prospective, nonrandomized clinical trial that included 20 critical patients with severe craniocerebral trauma who were receiving mechanical ventilation and who were admitted to the intensive care unit. Each patient was subjected to the physiotherapeutic maneuvers of vibrocompression and increased manual expiratory flow (5 minutes on each hemithorax), along with subsequent airway suctioning with prior instillation of saline solution, hyperinflation and hyperoxygenation. Variables related to cardiovascular and cerebral hemodynamics and blood gas variables were recorded after each vibrocompression, increased manual expiratory flow and airway suctioning maneuver and 10 minutes after the end of airway suctioning.

RESULTS

The hemodynamic and blood gas variables were maintained during vibrocompression and increased manual expiratory flow maneuvers; however, there were increases in mean arterial pressure, intracranial pressure, heart rate, pulmonary arterial pressure and pulmonary capillary pressure during airway suctioning. All of the values returned to baseline 10 minutes after the end of airway suctioning.

CONCLUSION

Respiratory physiotherapy can be safely performed on patients with severe craniocerebral trauma. Additional caution must be taken when performing airway suctioning because this technique alters cerebral and cardiovascular hemodynamics, even in sedated and paralyzed patients.

Efeitos da higienização brônquica nas variáveis cardiorrespiratórias de pacientes em ventilação mecânica

INTRODUÇÃO: Durante a ventilação mecânica (VM) as vias aéreas podem acumular secreção. Pacientes em VM são submetidos a Fisioterapia Respiratória (FR) e a aspiração traqueal, associados ou isoladamente, com objetivo de higienizar as vias aéreas. OBJETIVO: Comparar os efeitos da aplicação de diferentes protocolos de higiene brônquica na pressão arterial, frequência cardíaca, saturação de oxigênio e frequência respiratória de pacientes submetidos à VM. MATERIAIS E MÉTODOS: Realizou-se estudo prospectivo e aleatório, controlado do tipo cruzado, com amostra não probabilística intencional no Hospital das Clínicas da Faculdade de Medicina de Marília. Foram incluídos pacientes em VM invasiva que foram submetidos a três protocolos de higienização brônquica: PFR - protocolo de fisioterapia (compressão torácica manual e hiperinsuflação manual); PAT - protocolo de aspiração; e PFR + PAT. Frequência respiratória, pressão arterial sistólica (PAS), pressão arterial diastólica (PAD), saturação periférica de oxigênio e frequência cardíaca foram avaliadas em três momentos: antes (M1), imediatamente após (M2), e 30 minutos após (M3) cada protocolo. As diferenças entre protocolos e momentos foram verificadas por meio do teste ANOVA e pos-hoc de Student Newman-Keus (p < 0,05). RESULTADOS: Foram avaliados 18 pacientes com 71,2 ± 13,9 anos de idade e com 15,1 ± 17,7 dias de VM. Não houve diferenças entre os protocolos. Diminuíram de forma significativa a PAS (p = 0,0261) e a PAD (p = 0,0119) de M2 para M3 no protocolo de aspiração. CONCLUSÃO: Pacientes em VM apresentaram diminuição da pressão arterial após 30 minutos de aspiração e não apresentaram alteração nas outras variáveis estudadas. Não houve diferença entre os protocolos.

Benefits and risks of manual hyperinflation in intubated and mechanically ventilated intensive care unit patients: a systematic review

Introduction

Manual hyperinflation (MH), a frequently applied maneuver in critically ill intubated and mechanically ventilated patients, is suggested to mimic a cough so that airway secretions are mobilized toward the larger airways, where they can easily be removed. As such, MH could prevent plugging of the airways.

Methods

We performed a search in the databases of Medline, Embase, and the Cochrane Library from January 1990 to April 2012. We systematically reviewed the literature on evidence for postulated benefits and risks of MH in critically ill intubated and mechanically ventilated patients.

Results

The search identified 50 articles, of which 19 were considered relevant. We included 13 interventional studies and six observational studies. The number of studies evaluating physiological effects of MH is limited. Trials differed too much to permit meta-analysis. It is uncertain whether MH was applied similarly in the retrieved studies. Finally, most studies are underpowered to show clinical benefit of MH. Use of MH is associated with short-term improvements in lung compliance, oxygenation, and secretion clearance, without changes in outcomes. MH has been reported to be associated with short-term and probably clinically insignificant side effects, including decreases in cardiac output, alterations of heart rates, and increased central venous pressures.

Conclusions

Studies have failed to show that MH benefits critically ill intubated and mechanically ventilated patients. MH is infrequently associated with short-term side effects.

Airflow distribution with manual hyperinflation as assessed through gamma camera imaging: a crossover randomised trial

OBJECTIVES

Manual hyperinflation (MHI) has been shown to improve lung compliance, reduce airway resistance, and enhance secretion removal and peak expiratory flow. The aims of this study were to investigate whether there is a difference in airflow distribution through patients' lungs when using the Laerdal and Mapleson-C circuits at a set level of positive end-expiratory pressure (PEEP), and to establish whether differences in lung compliance and haemodynamic status exist when patients are treated with both these MHI circuits.

DESIGN

Crossover randomised controlled trial.

SETTING

Adult multidisciplinary intensive care unit (ICU) at an academic hospital.

PARTICIPANTS

Fifteen adult patients were recruited and served as their own controls.

INTERVENTION

In the Nuclear Medicine Department, MHI with PEEP 7.5 cmH(2)O was performed in the supine position (Day 1) with either Laerdal or Mapleson-C circuits, in a random order, while technetium-99m (Tc-99m) aerosol was administered and images were taken with a gamma camera. Changes in heart rate (HR), mean arterial pressure (MAP) and dynamic lung compliance (C(D)) were documented at baseline, immediately after return to ICU, and 10, 20 and 30 minutes after return to ICU. The alternative circuit was used on Day 2.

RESULTS

Tc-99m deposition was greater in the right lung field (62% and 63% for Laerdal and Mapleson-C circuits, respectively) than the left lung field (38% and 37%, respectively) for all patients, and least deposition occurred in the left lower segments (6% and 6%, respectively). No differences in Tc-99m deposition in the lungs, HR, MAP or C(D) were noted between the two MHI circuits.

CONCLUSION

Airflow distribution through patients' lungs was similar when the Laerdal and Mapleson-C MHI circuits were compared using a set level of PEEP in the supine position.

Manual hyperinflation partly prevents reductions of functional residual capacity in cardiac surgical patients--a randomized controlled trial

INTRODUCTION

Cardiac surgery is associated with post-operative reductions of functional residual capacity (FRC). Manual hyperinflation (MH) aims to prevent airway plugging, and as such could prevent the reduction of FRC after surgery. The main purpose of this study was to determine the effect of MH on post-operative FRC of cardiac surgical patients.

METHODS

This was a randomized controlled trial of patients after elective coronary artery bypass graft and/or valve surgery admitted to the intensive care unit (ICU) of a university hospital. Patients were randomly assigned to a "routine MH group" (MH was performed within 30 minutes after admission to the ICU and every 6 hours thereafter, and before tracheal extubation), or a "control group" (MH was performed only if perceptible (audible) sputum was present in the larger airways causing problems with mechanical ventilation, or if oxygen saturation (SpO2) dropped below 92%). The primary endpoint was the reduction of FRC from the day before cardiac surgery to one, three, and five days after tracheal extubation. Secondary endpoints were SpO2 (at similar time points) and chest radiograph abnormalities, including atelectasis (at three days after tracheal extubation).

RESULTS

A total of 100 patients were enrolled. Patients in the routine MH group showed a decrease of FRC on the first post-operative day to 71% of the pre-operative value, versus 57% in the control group (P = 0.002). Differences in FRC became less prominent over time; differences between the two study groups were no longer statistically significant at Day 5. There were no differences in SpO2 between the study groups. Chest radiographs showed more abnormalities (merely atelectasis) in the control group compared to patients in the routine MH group (P = 0.002).

CONCLUSIONS

MH partly prevents the reduction of FRC in the first post-operative days after cardiac surgery.

TRIAL REGISTRATION

Netherlands Trial Register (NTR): NTR1384. http://www.trialregister.nl.

Effect of multimodality chest physiotherapy in prevention of ventilator-associated pneumonia: A randomized clinical trial

Background:

Despite remarkable progress that has been achieved in the recent years in the diagnosis, prevention, and therapy for ventilator-associated pneumonia (VAP), this disease continues to create complication during the course of treatment in a significant proportion of patients while receiving mechanical ventilation.

Objective:

This study was designed to evaluate the effect of multimodality chest physiotherapy in intubated and mechanically ventilated patients undergoing treatment in the intensive care units (ICUs) for prevention of VAP.

Patients and Methods:

A total of 101 adult intubated and mechanically ventilated patients were included in this study. Manual hyperinflation (MH) and suctioning were administered to patients in the control group (n = 51), and positioning and chest wall vibrations in addition to MH plus suctioning (multimodality chest physiotherapy) were administered to patients in the study group (n = 50) till they were extubated. Both the groups were subjected to treatment twice a day. Standard care in the form of routine nursing care, pharmacological therapy, inhalation therapy, as advised by the concerned physician/surgeon was strictly implemented throughout the intervention period.

Results:

Data were analyzed using SPSS window version 9.0. The Clinical Pulmonary infection Score (CPIS) Score showed significant decrease at the end of extubation/successful outcome or discharge in both the groups (P = 0.00). In addition, significant decrease in mortality rate was noted in the study group (24%) as compared to the control group (49%) (P = 0.007).

Conclusions:

It was observed in this study that twice-daily multimodality chest physiotherapy was associated with a significant decrease in the CPIS Scores in the study group as compared to the control group suggesting a decrease in the occurrence of VAP. There was also a significant reduction in the mortality rates with the use of multimodality chest physiotherapy in mechanically ventilated patients.

Comparison of flow rates produced by two frequently used manual hyperinflation circuits: a benchtop study

BACKGROUND

Manual hyperinflation is a treatment technique commonly used by physiotherapists in intensive care units to reverse or prevent atelectasis and mobilize airway secretions in intubated patients. The aim of this study was to determine which of the Magill (Rusch Manufacturing Ltd, Craigavon, UK) or Mapleson-C (CIG DF 655, CIG Medishield, Sydney, Australia) manual hyperinflation circuits was theoretically more effective at mobilizing secretions.

METHODS

A semi-blinded crossover study of 12 physiotherapists with tertiary level intensive care unit experience was conducted on a benchtop model. The order of circuits and compliance settings was randomized.

RESULTS

The Mapleson-C circuit produced a significantly faster peak expiratory flow (F[1, 210]=14.51, P < or = .01) and smaller inspiratory to expiratory flow ratio (F[1, 210]=28.44, P < or = .01) than the Magill circuit regardless of compliance settings.

CONCLUSION

The results of this study suggest that the Mapleson-C manual hyperinflation circuit may be more effective at mobilizing secretions.

The effect of additional physiotherapy to hospital inpatients outside of regular business hours: A systematic review

Provision of out of regular business hours (OBH) physiotherapy to hospital inpatients is widespread in the hospital setting. This systematic review evaluated the effect of additional OBH physiotherapy services on patient length of stay (LOS), pulmonary complications, discharge destination, discharge mobility status, quality of life, cost saving, adverse events, and mortality compared with physiotherapy only within regular business hours. A literature search was completed on databases with citation tracking using key words. Two reviewers completed data extraction and quality assessment independently by using modified scales for historical cohorts and case control studies as well as the PEDro scale for randomized controlled trials and quasi-randomised controlled trials. This search identified nine articles of low to medium quality. Four reported a significant reduction in LOS associated with additional OBH physiotherapy, with two articles reporting overall significance and two reporting only for specific subgroups. Two studies reported significant reduction in pulmonary complications for two different patient groups in an intensive care unit (ICU) with additional OBH physiotherapy. Three studies accounted for discharge destination and/or discharge mobility status with no significant difference reported. Quality of life, adverse events, and mortality were not reported in any studies. Cost savings were considered in three studies, with two reporting a cost saving. This systematic review was unable to conclude that the provision of additional OBH physiotherapy made significant improvement to patient outcomes for all subgroups of inpatients. One study in critical care reported that overnight physiotherapy decreased LOS and reduced pulmonary complications of patients in the ICU. However, the studies in the area of orthopaedics, neurology, postcardiac surgery, and rheumatology, which all considered additional daytime weekend physiotherapy intervention, did not provide strong evidence to indicate effective reduction in patient LOS or improving patient discharge mobility status or discharge destination. Investigation should continue in this area, but future trials should ensure factors such as random allocation, groups equal at baseline, blinded investigators, and proven intervention are included in the study design.

Physiotherapy in intensive care is safe: an observational study

QUESTION

How often do adverse events (including adverse physiological changes) occur during physiotherapy intervention in intensive care?

DESIGN

A multi-centre prospective observational study.

PARTICIPANTS

Five tertiary level university-affiliated intensive care units.

OUTCOME MEASURES

All physiotherapy intervention in five intensive care units over a three month period. When certain specified changes occurred during physiotherapy intervention, details were noted including diagnosis of patient, intervention, vital signs, radiological changes, co-morbidities, chemical pathology, and fluid balance.

RESULTS

12 281 physiotherapy interventions were completed with 27 interventions resulting in adverse physiological changes (0.2%). This incidence was significantly lower than a previous study of adverse physiological changes (663 events in 247 patients over a 24-hour period); the incidence during physiotherapy intervention was lower than during general intensive care. Common factors in the patients who had an adverse physiological change were a deterioration in cardiovascular status (ie, decrease in blood pressure or arrhythmia) in patients on medium to high doses of inotropes/vasopressors, unstable baseline hemodynamic values, previous cardiac co-morbidities and intervention consisting of positive pressure or right side lying.

CONCLUSION

The incidence of adverse events during physiotherapy intervention in these five tertiary hospitals was low, demonstrating that physiotherapy intervention in intensive care is safe.

The Mapleson C circuit clears more secretions than the Laerdal circuit during manual hyperinflation in mechanically-ventilated patients: a randomised cross-over trial

QUESTION

What is the effect of the Mapleson C circuit compared with the Laerdal circuit in removing secretions and improving ventilation and gas exchange during manual hyperinflation?

DESIGN

Prospective, randomised, cross-over trial.

PARTICIPANTS

Twenty patients from a tertiary-level intensive care unit who were being mechanically ventilated.

INTERVENTION

Manual hyperinflation in side-lying with both the Mapleson C or Laerdal circuit on the one day, one circuit in the morning and one in the afternoon, with a washout period of at least three hours between them.

OUTCOME MEASURES

Secretion clearance was measured as sputum weight, ventilation was measured as respiratory compliance and tidal volume, while gas exchange was measured as oxygenation and CO2 removal.

RESULTS

The Mapleson C circuit cleared 0.89 g (95% CI 0.80 to 1.15) more secretions than the Laerdal circuit (p < 0.02). There was no difference between the Mapleson C and the Laerdal circuits on respiratory compliance (p = 0.81), tidal volume (p = 0.45), oxygenation (p = 0.28), or CO2 removal (p = 0.17).

CONCLUSION

Although more secretions were cleared using the Mapleson C compared with the Laerdal circuit in this study, this had no consequence in terms of oxygenation and compliance only trended to improve. As the study was underpowered the clinical significance of these findings is not clear.

Comparison of the effectiveness of manual and ventilator hyperinflation at different levels of positive end-expiratory pressure in artificially ventilated and intubated intensive care patients

BACKGROUND

Manual hyperinflation (MHI) and ventilator hyperinflation (VHI) are two methods of recruitment maneuvers used in ventilated patients to improve lung compliance and secretion mobilization. The use of VHI may minimize the adverse effects of disconnection from the ventilator, but it is uncertain whether high levels of positive end-expiratory pressure (PEEP) would decrease the peak expiratory flow rate (PEFR) and consequently affect secretion clearance.

OBJECTIVES

The aim of this study was to compare the effectiveness of MHI and VHI in terms of clearing pulmonary secretions (sputum wet weight and PEFR), improving static respiratory system compliance and oxygenation (arterial oxygen tension/fraction of inspired oxygen), and altering mean arterial pressure, heart rate, and carbon dioxide output at different levels of PEEP.

METHODS

This was a randomized crossover study involving 14 general intensive care patients who were intubated and mechanically ventilated.

RESULTS

Sputum production was similar in both techniques and levels of PEEP. There were no differences in improvement in oxygenation and static respiratory system compliance between MHI and VHI. However, VHI increased Cst significantly at 30 minutes posttreatment (P = .012), and a significant difference was observed between levels 5 and 7.5 cmH(2)O (P = .02) of PEEP for MHI. MHI generated higher PEFR than VHI (P < .05). No adverse change in heart rate or mean arterial pressure was observed during either technique; however, VCO(2) was significantly different for techniques (P = .045) and over time (P = .05).

CONCLUSION

The VHI technique seems to promote greater improvements in respiratory mechanics with less metabolic disturbance compared with MHI. Other variables such as sputum production, hemodynamics, and oxygenation were affected similarly by both techniques.

Manual hyperinflation causes norepinephrine release

OBJECTIVE

To measure hemodynamics and plasma catecholamines during manual hyperinflation (MHI) in ventilated patients.

METHODS

MHI was performed with a Mapleson "C" circuit, 2l-reservoir bag; peak inspiratory pressure was standardized to 35 mL water; and positive expiratory-end pressure of 5 mL water was administered to seven mechanically ventilated patients with septic (6) and cardiogenic (1) shock (67.2 +/- 5.2 years, Acute Physiology Assessment and Chronic Health Evaluation II score 22.1 +/- 3.1). Diastolic (DAP) and mean arterial pressure (MAP), continuous cardiac index, pulmonary artery occlusion pressure, dynamic compliance, plasma norepinephrine and epinephrine, and arterial blood gases were recorded, and systemic vascular resistance index (SVRI) and oxygenation ratio were calculated.

RESULTS

There were no significant changes in pulmonary artery occlusion pressure, mean arterial pressure, or PaO2/FiO2. There were significant increases in SVRI (P < .001), DAP (P < .001), dynamic compliance (P < .01), and plasma norepinephrine (P < .001) and a decrease in cardiac index (P < .05) after MHI.

CONCLUSIONS

The increases in DAP, SVRI, and plasma norepinephrine suggest a sympathetic vasoconstrictive response during the application of MHI.

Effect of manual hyperinflation on haemodynamics in an animal model

BACKGROUND AND PURPOSE

Manual hyperinflation is a physiotherapy technique that improves static compliance and mobilizes secretions, but has the potential to alter haemodynamic function. The aim of the present study was to investigate the effects of manual hyperinflation on haemodynamic function in a healthy animal model, without the usual confounding effects inherent in an heterogeneous intensive care population.

METHOD

The study used a within-subjects design, in an animal research theatre. Nine healthy sheep (eight Border Leicester, one Merino, mean weight 39.5 kg, standard deviation (SD) 1.6 kg) completed the study. The sheep were induced (thiopentane 15-20 ml), intubated, ventilated and surgically instrumented for an arterial line and pulmonary artery catheter. Anaesthesia was maintained by 1.5% halothane/oxygen. Manual hyperinflation was delivered for two minutes with a Mapleson C circuit, using a peak inspiratory pressure of 35 cmH2O and an inspiratory:expiratory ratio of 2:1.

RESULTS

Mean tidal volume during manual hyperinflation was 294% (SD 22%) of the ventilator tidal volume. A paired Student's t-test demonstrated that cardiac output (thermodilution method) decreased significantly (p < 0.05) and systemic vascular resistance increased significantly (p < 0.01) after manual hyperinflation. A repeated-measures analysis of variance (ANOVA) and a least-significant difference pairwise comparison revealed that mean arterial pressure and pulse pressure decreased significantly during (p < 0.01) and increased significantly (mean arterial pressure, p < 0.05 and mean pulse pressure p < 0.001) after the technique. Pulmonary artery pressure also increased significantly during manual hyperinflation (p < 0.01). There were no significant effects on right atrial pressure, pulmonary artery occlusion pressure or heart rate.

CONCLUSION

Significant haemodynamic changes occurred in this animal model. The increased intrathoracic pressure, applied for an increased period during inspiration, decreased cardiac output with compensatory vasoconstriction evident by the increased systemic vascular resistance and mean arterial pressure. The results suggest that there may be a decrease in cardiac output after increased positive pressure in subjects with normal cardiac and respiratory function.

The effect of positive end-expiratory pressure level on peak expiratory flow during manual hyperinflation

Including positive end-expiratory pressure (PEEP) in the manual resuscitation bag (MRB) may render manual hyperinflation (MHI) ineffective as a secretion maneuver technique in mechanically ventilated patients. In this study we aimed to determine the effect of increased PEEP or decreased compliance on peak expiratory flow rate (PEF) during MHI. A blinded, randomized study was performed on a lung simulator by 10 physiotherapists experienced in MHI and intensive care practice. PEEP levels of 0-15 cm H(2)O, compliance levels of 0.05 and 0.02 L/cm H(2)O, and MRB type were randomized. The Mapleson-C MRB generated significantly higher PEF (P < 0.01, d = 2.72) when compared with the Laerdal MRB for all levels of PEEP. In normal compliance (0.05 L/cm H(2)O) there was a significant decrease in PEF (P < 0.01, d = 1.45) for a PEEP more than 10 cm H(2)O in the Mapleson-C circuit. The Laerdal MRB at PEEP levels of more than 10 cm H(2)O did not generate a PEF that is theoretically capable of producing two-phase gas-liquid flow and, consequently, mobilizing pulmonary secretions. If MHI is indicated as a result of mucous plugging, the Mapleson-C MRB may be the most effective method of secretion mobilization.

The effect on expiratory flow rate of maintaining bag compression during manual hyperinflation

Operator performance during the expiratory phase of manual hyperinflation appears to vary between physiotherapists for Mapleson-B or C circuits. Some physiotherapists release the valve but maintain compression of the bag, whereas others release both the valve and the bag. The effect of this difference on peak expiratory flow rate (PEFR) has not been reported. The aim of this study was to document the effect of maintaining bag compression during expiration on PEFR and inspiratory to expiratory flow rate ratio (I:E). Six physiotherapists with experience using manual hyperinflation participated. A within-subjects repeated measures design was used. Subjects performed manual hyperinflation using a Mapleson-C circuit with 'rapid release', releasing the valve only, or releasing both the bag and the valve, during expiration in a test lung model. Inspiratory time was controlled using a metronome and flows were measured with a heated pneumotachometer. Maintaining bag compression significantly reduced PEFR (1.54 (0.08) vs 2.00 (0.07) l/sec, p = 0.008) and increased I:E flow rate ratio (0.65 (0.04) vs 0.50 (0.02), p = 0.02) for the Mapleson-C circuit at a 1.4 litre target volume. There were no significant differences for these measures between techniques when subjects emptied the bag. The effect needs to be confirmed in the clinical setting.