Ventilation modes in intensive care guide Nov 2014

Important note This brochure does not replace the instructions for use. Prior to using a ventilator the corresponding instructions for use must always be read and understood.

Ventilation modes in intensive care Karin Deden

04|05

CONTENTS Important note Preface Introduction Mechanical ventilation Volume-controlled ventilation AutoFlow VC-CMV VC-AC VC-SIMV VC-MMV Pressure-controlled ventilation Volume guarantee PC-CMV PC-AC PC-SIMV PC-BIPAP PC-APRV PC-PSV Spontaneous/assisted ventilation SPN-CPAP/PS Variable PS SPN-CPAP/VS SPN-PPS Specific neonatal ventilation modes SPN-CPAP PC-HFO PC-MMV Extended ventilation settings Nomenclature comparison Glossary References

02 06 09 11 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70

VENTILATION MODES IN INTENSIVE CARE |

PREFACE

Preface TOWARDS A CLASSIFICATION FOR VENTILATION

In 1977, Steven McPherson wrote the first popular book on ventilation equipment in the USA. Ventilation was discussed on 65 percent of the pages, but only 3 ventilation modes were explained in detail: “controlled”, “assisted” and “spontaneous breathing”. Some modes were not mentioned in the specification tables for ventilators in the book. Instead, the book focused on specific drive mechanisms and configurations as well as on how configurations could be combined into identifiable operating modes. The description of a ventilator in the book was, for example, akin to an “… electrically driven rotating piston, double circuit, timed, time and volume limited controller …”. It must be taken into account that the concept of “IMV” (Intermittent Mandatory Ventilation) had only been invented four years earlier. The seventh edition of McPherson’s ventilator book was published in 2004. Interestingly, about two thirds of the book are still dedicated to the topic of ventilation. In this edition, only 22 ventilation modes are described on 19 pages. However, on the subsequent pages where specific ventilators are described, 93 different ventilation modes are mentioned. These are, however, not 93 different modes. In many instances, different names are used for identical modes (e.g. the pressure control ventilation plus adaptive pressure ventilation in the Hamilton Galileo corresponds to the pressure regulated volume control in the Maquet Servo 300), and in some cases, the same name is used for different modes (assist/control in the Puritan Bennett 840 is a kind of volume-controlled ventilation, whilst assist/control in the Bear Cub ventilator for infants is a kind of pressure-controlled ventilation). As in many other fields, the technical complexity has increased significantly in ventilation. Today modern ventilators might feature more than two dozen modes; some even utilize computer-assisted artificial intelligence. Within a single human generation, ventilators have spanned approximately 5 generations

06|07

in development. What has not been developed is a standardized system sufficiently describing this technical complexity. This causes four main problems: (1) published studies about ventilation are difficult to compare making it hard to compile and describe factual statements; (2) there is little consistency between medical training programs with regard to the nomenclature and descriptions of how ventilators work; (3) clinical staff working in clinics where ventilators of different manufacturers are used (which is quite common) do not have the time or training resources for adequate training and practice in using all modes in all ventilators, making optimum patient care difficult and (4) manufacturers cannot discuss the precise operation of their products easily with future customers, limiting the effectiveness of sales and training and in turn reinforcing the other problems. To date, neither manufacturers nor professional associations have found a common consensus about a classification for ventilation. However, certain efforts have already been made: The committee TC 121 (Anesthetic and Respiratory Equipment) of the International Organization for Standardization has a subcommittee (SC3 Lung Ventilators and Related Equipment) working on a standardized terminology. „Integrating the Healthcare Enterprise“ (IHE) is an initiative of experts and health care companies to improve the exchange of information between computer systems in the health care sector. The IHE domain „Patient Care Device“ works on the basis of an RTM profile (Rosetta Terminology Mapping) connecting provider-specific terminology with standardized terminology (based on ISO/IEEE 11073-10101), predominantly for emergency care equipment such as ventilators. Its aim is the uniform representation of key equipment data, especially if these are communicated to a gateway for health care applications. The increasing use of electronic patient files in hospitals worldwide makes the efforts of these organizations indispensable. Finding a consensus between so many different interested parties is a long and difficult process. With the compilation of a common nomenclature for all patient groups in intensive care, anesthesia and during monitoring, Dräger makes an important contribution to these efforts. Dräger recognizes the necessity of practical clarity when

VENTILATION MODES IN INTENSIVE CARE |

PREFACE

describing modes. As in other companies, the advanced product designs of Dräger: has its advantages and disadvantages They provide the latest lifesaving technology, but they are also confusingly complex, hampering the expansion of this technology. The purpose of this booklet is to describe the available modes for the Dräger ventilators in a systematic and informative manner. Although this might not serve as a universal classification for the modes, we hope that it will improve the understanding of the many available ventilation modes for Dräger devices and therefore ultimately improve patient care.

Robert L. Chatburn, BS, RRT-NPS, FAARC Clinical Research Manager Respiratory Institute Cleveland Clinic Adjunct Associate Professor Department of Medicine Lerner College of Medicine of Case Western Reserve University Cleveland, Ohio, USA

08|09

Introduction If you follow a patient from an initial event such as an accident location all the way until he/she is released from hospital, you will notice that mechanical ventilation is necessary and used in many areas of patient care. Already at the accident location and during transportation, ventilation is provided using an emergency ventilator. During the operation in the hospital an anesthesia machine provides ventilation. Intensive care ventilators are available during the critical stay in intensive care. Even during the subsequent treatment on intermediate care wards, some patients require mechanical breathing support. Mechanical ventilation is required in all areas of the hospital. For neonatal patients, the mechanical ventilation starts soon after birth using a ventilator or manual ventilation bag, usually in the labor room or operating room. After a brief transport to the neonatal intensive care ward, these small patients are ventilated mechanically until their condition is stable. In the various departments with their corresponding patient groups, different ventilation modes were developed on the basis of the individual needs and requirements. Different names for principally identical modes cause confusion and place heavy demands on the user. Within international literature, too, different names are used for the same ventilation mode. For example, the literature often mentions CMV/AC whereas for the ventilation of adults with Dräger equipment the term IPPV/IPPVassist is used. Dräger recognizes how difficult the current situation is for the user and therefore developed a uniform nomenclature for ventilation modes from emergency provision through anesthesia and intensive care to monitoring/IT. This brochure intends to facilitate the move from the old to the new nomenclature. For this reason, the properties and control principles of the individual ventilation modes are briefly outlined. The focus of the mode descriptions is the intensive care ventilation for adults, pediatric patients and neonatal patients. For a precise comparison of the designations, the brochure concludes with a comparison of the ventilation modes in the previous and the new

VENTILATION MODES IN INTENSIVE CARE |

INTRODUCTION

nomenclature. The comparison of the designations is given for the intensive care ventilation of adults and neonatal patients as well as for anesthesia.

10|11

Mechanical ventilation When operating a ventilator, patients can be ventilated in many different ways. Differentiation is made between mandatory and spontaneous breathing methods. When utilizing mandatory breathing methods the equipment fully or partially controls the breathing. During spontaneous breathing methods the patient is either fully capable of breathing independently at the PEEP level or receive support from the equipment. The ventilation modes of Dräger equipment can be divided into three ventilation groups: volume-controlled modes, pressure-controlled modes and spontaneous/assisted modes. Mandatory ventilation methods Volume-controlled modes Pressure-controlled modes

Spontaneous breathing method Spontaneous/assisted modes

To indicate to which group a ventilation mode belongs, the modes are preceded by prefixes. – VC‑ for volume‑controlled – PC‑ for pressure‑controlled – SPN‑ for spontaneous The prefixes are followed by the name of the ventilation mode which explains the ventilation mode and its operation in more detail. This results in the following ventilation modes described in more detail in this brochure:

VENTILATION MODES IN INTENSIVE CARE |

Volume-controlled VC-CMV VC-AC VC-SIMV VC-MMV

MECHANICAL VENTILATION

Pressure-controlled PC-CMV PC-AC PC-SIMV PC-BIPAP PC-APRV PC-PSV PC-HFO PC-MMV

Spontaneous/assisted SPN-CPAP/PS SPN-CPAP/VS SPN-PPS SPN-CPAP

For some ventilation modes, there are extended configurations, such as AutoFlow® (AF), Volume Guarantee (VG) or PS (Pressure Support). These extended configurations are explained in more detail in this brochure. In order to understand the particularities of the modes, it is important to know the control and actuating variables. FORMS OF MANDATORY BREATH

The control variable, primary affected or controlled by the equipment, is identified by the prefix VC or PC. The control variables are discussed in more detail in the sections on volume- and pressure-controlled ventilation. When controlling the mandatory ventilation, a difference is made between the control of the start of inspiration and the control of the start of expiration. CONTROL VARIABLE - START OF INSPIRATION

The inspiration can be initiated by the patient or by the equipment. This is called patient-triggered or mechanically triggered mandatory breath.

12|13

Paw

PEEP t

Flow Trigger threshold

D-273-2010

t

Figure 1: Trigger threshold

PATIENT-TRIGGERED

In patient-triggered mandatory breath, the patient breathes independently. The equipment detects this inspiration attempt and triggers the inspiration. In many ventilators, a flow trigger is used to detect inspiration. The sensitivity of the trigger, the so-called trigger threshold, after which a mandatory breath is applied, can be configured according to the patient (Figure 1). Trigger windows have been set up for many ventilation modes. Inspiration attempts of the patient triggering the mandatory breaths are detected only within this range. This ensures that the set ventilation frequency of the mandatory breaths remains constant. MECHANICALLY TRIGGERED

The mechanically triggered mandatory breaths are triggered without patient activity. They are always timed. This means that the patient has no influence on the time of inspiration. The start of inspiration depends exclusively on the

VENTILATION MODES IN INTENSIVE CARE |

MECHANICAL VENTILATION

Paw

Start of inspiration

t

End of inspiration

Flow 100 %

D-275-2010

x% t

Figure 2: Termination criteria (peak inspiration flow)

configured time parameters, e.g. the frequency (RR), the inspiration/expiration cycle (I:E ratio) or the inspiratory time (Ti). CONTROL VARIABLE - START OF EXPIRATION

Expiration can be triggered either flow or time cycled. FLOW-CYCLED

With flow cycling, the start of expiration depends on the breathing and lung mechanics of the patient. The inspiration phase is concluded as soon as the inspiratory flow has reached a defined share of the maximum inspiratory flow. This means that the patient determins the beginning of the expiratory phase (Figure 2).

14|15

TIME-CYCLED

If the start of expiration is time-cycled, then only the inspiratory time (Ti) determines the starting point of expiration. The patient has no, or in some modes only a minor, influence on the duration of the inspiration phase.

Control principles Start of inspiration Patient-triggered Machine triggered

Start of expiration Flow-cycled Time-cycled

WHICH VENTILATION MODE FOR WHICH TREATMENT PHASE?

During the ventilation treatment, a patient goes through different phases marked by different support requirements (Figure 3). At the start, the patient might be fully sedated. His breathing control is not operating and he depends on controlled ventilation. If the sedation is subsequently reduced, breathing control may be active to a certain extent, albeit unstable. However, the breathing muscles may be too weak to cope with the breathing task independently. A mixed ventilation is required that permits spontaneous breathing but shares the breathing load between the patient and the equipment. Once the patient has achieved independent and stable breathing, but remains weak, he requires gentle support in breathing. The patient’s breathing can be supported using spontaneous/assisted ventilation. If the patient has recovered sufficiently to regain his full breathing ability and his breathing muscles have regained their strength, he can breathe spontaneously by himself.

VENTILATION MODES IN INTENSIVE CARE |

MECHANICAL VENTILATION

Spontaneous breathing

Controlled ventilation

Respiratory muscle

Breathing control system

Respiratory muscle

Breathing control system

sufficient

intact

intact or paralyzed

not available

Patient Assisted spontaneous breathing

Mixed ventilation

Breathing control system

Respiratory muscles

Breathing control system

weak

intact

weak

restricted or unstable

D-274-2010

Respiratory muscles

Figure 3: Forms of breathing / ventilation

The symbols with the circles filled in at different levels represent the respective therapy status of the patient. These symbols are provided for each mode description and assist in determining for which therapy stage the described mode can be used. ALARM LIMITS:

During the treatment of a patient, the overall status can change several times; this also applies to the pulmonary situation of the patient. It can therefore become necessary to adapt therapeutic objectives or treatment strategies. Indicative alarm limits therefore protect the patient and help finding the correct time for adapting the ventilation settings.

16|17

With every patient admission and every change in ventilation mode, the alarm limits should be checked and adjusted to the patient and the ventilation mode. Changes in the lung properties and thus the Resistance (R) and Compliance (C) have different effects in the different ventilation modes. For volume-controlled ventilation modes, the pressures are resulting variables. It is therefore important to adjust the alarm limit Phigh appropriately. In the case of pressure-controlled ventilation modes, the applied tidal volume changes with a change of Resistance and Compliance. Here, particular attention must be paid to the alarm limits for VThigh, VTlow, MVhigh, MVlow and RRhigh to ensure patient protection.

VENTILATION MODES IN INTENSIVE CARE |

VOLUME-CONTROLLED VENTILATION

Volume-controlled ventilation

During volume-controlled ventilation, the set tidal volume is supplied by the ventilator at a constant flow. The inspiratory pressure is the resulting variable and changes dependent on the changing lung mechanics. The value controlled and kept at the target value by the equipment is the tidal volume (VT). The tidal volume and the number of mandatory breaths per minute (f) can be adjusted. This results in the minute volume (MV). The velocity at which the breathing volume (VT) is applied is adjusted by the flow, the constant inspiratory flow. A breath can be divided into an inspiratory and expiratory phase. The duration of the inspiratory phase is defined by the inspiration time (Ti). If the inspiratory flow is so high that the set breathing volume is reached before the set inspiratory time (Ti) has passed, there will be a pause in inspiration. Because the pressures in the lung can vary in volume-controlled ventilation with a change in lung properties and thus the Resistance (R) and Compliance (C), it is important to set the alarm limit Phigh based on the patient. To ensure free breathing ability during the complete breathing cycle, and thus increase patient comfort, AutoFlow can be enabled during volume-controlled ventilation. Volume-controlled ventilation modes are not available for the neonatal patient category.

D-255-2010

18|19

21

520

1.70

12.0

5.0

21

FiO2

VT

Ti

RR

PEEP

Flow

Figure 4: Possible ventilation settings for volume-controlled ventilation modes for adult patient category

Due to the pressure limitation it is possible that the set VT is not always achieved Minute volume MV = VT * RR AutoFlow can be enabled for all volume-controlled modes

Set the alarm limit Phigh patient-specific > Not available in the neonatal patient category  Volume-controlled modes VC-CMV VC-AC VC-SIMV VC-MMV

Paw

Insp. Pause Pplat

PEEP Ti Flow

D-5-2010

Insp. Flow

Figure 5: Volume-controlled ventilation

Te 1 RR

VENTILATION MODES IN INTENSIVE CARE |

CONTENTS

AUTOFLOW

– extended ventilation configuration for all volume-controlled ventilation modes (Figure 6) AutoFlow ensures that the set tidal volume (VT) is applied with the necessary minimum pressure for all mandatory breaths. If the Resistance (R) or Compliance (C) changes, the pressure adapts gradually in order to administer the set tidal volume (VT). This means that both the pressure and the flow are adjusted automatically. During the whole breathing cycle, both during inspiration and expiration, the patient can breathe spontaneously.

20|21

Decelerating flow curve Pressure peaks are prevented Free breathing ability during the breathing cycle Guaranteed tidal volume

Paw

Pinsp = f (VT, C) PEEP

Flow

D-6-2010

VT

Figure 6: AutoFlow