The following waveforms display volume control ventilation with a descending ramp pattern of inspiratory flow. All breaths are patient-triggered, as indicated by a pressure drop preceding inspiration. The pressure-time scalar shows a downward deflection below baseline, reflecting strong inspiratory efforts that generate negative intrathoracic pressure. This pattern suggests work shifting, where a significant portion of the breathing workload is transferred from the ventilator

These ventilator scalars are from a patient on volume control ventilation. The airway pressure trace shows a brief dip below baseline during inspiration, suggesting strong inspiratory efforts. The flow-time scalar displays a rounded inspiratory contour instead of the typical straight line seen in volume control mode with constant flow. This occurs due to a ventilator feature called flow adaptation, in which the ventilator senses strong inspiratory effort and automatically adj

A major limitation of volume control ventilation is that it delivers a fixed inspiratory flow, regardless of the patient’s effort. This can increase the patient’s work of breathing, a phenomenon known as work shifting. To improve patient comfort, some ventilator manufacturers have introduced a feature called flow adaptation, which allows the ventilator to sense strong inspiratory efforts and provide additional flow as needed. This feature can significantly modify the waveform

Flow adaptation is a term used by some ventilator manufacturers to describe the delivery of additional flow during volume control ventilation in response to strong patient inspiratory efforts. In this example, a downward deviation of the airway pressure waveform during the first half of inspiration indicates the patient’s vigorous inspiratory effort. The ventilator senses this increased demand and provides supplemental flow, producing a small upward bump above the otherwise c

Flow starvation is a type of patient–ventilator dyssynchrony that occurs when the ventilator’s flow delivery fails to meet the patient’s inspiratory demand, resulting in a scooped appearance of the inspiratory pressure–time waveform. The term “work shifting” is now preferred, as it more accurately describes the phenomenon in which part of the inspiratory workload shifts from the ventilator to the patient. This can be recognized by a downward deformation of the inspiratory air

These waveforms illustrate multiple patient–ventilator dyssynchronies, highlighting the consequences of inappropriate ventilator settings. In the pressure–time scalar, immediately after the breath is triggered, the airway pressure drops to the level of PEEP, indicating a strong inspiratory effort and significant work shifting from the ventilator to the patient. This is followed by a steep rise in pressure, which reflects inspiratory muscle relaxation and expiratory muscle con

The following volume control waveforms demonstrate severe work shifting, late cycling dyssynchrony, and active expiratory effort. In the pressure–time scalar, a pronounced drop below the baseline during the early inspiratory phase indicates significant work shifting (previously referred to as flow starvation ), where the ventilator’s delivered flow does not meet the patient’s inspiratory demand. As the inspiratory muscles relax and the expiratory muscles contract, the airway

The flow-time scalar typically exhibits an exponential decay when a patient exerts minimal inspiratory effort. This pattern may also indicate that the patient has a low respiratory drive and is exerting minimal work during breathing. Moreover, this appearance can also be observed in cases of false triggering, where the patient is in a passive state. The rounded appearance of the inspiratory flow-time scalar is commonly observed when a patient exerts substantial inspiratory ef

Work shifting: During the initial phase of inspiration, the pressure is lower than the set Positive End-Expiratory Pressure (PEEP). This is a result of the patient's strong inspiratory effort (Pinsp mus).  Late cycling (delayed cycling): As the inspiratory muscles relax, the pressure waveform rises above the baseline. Some patients may engage their expiratory muscles to actively facilitate the expulsion of air from the lungs, leading to a sharp increase in pressure.  The pa

The first breath is initiated by the ventilator through a time-triggered mechanism. Since the patient is passive (Pmus= zero), all the work is done by the ventilator to inflate the lungs.  However, starting from the second breath and continuing through the third and fourth breaths, a noticeable deformation of the inspiratory pressure-time scalar becomes apparent. The gradual shift of pressure-time scalar toward the baseline is a result of the patient's increasing inspiratory

Work shifting: During the initial phase of inspiration, the pressure is lower than the set Positive End-Expiratory Pressure (PEEP) because of the large inspiratory efforts (strong Pmus). Late cycling (delayed cycling): As the inspiratory muscles relax and expiratory muscles contract, the pressure waveform rises above the baseline. The patient completes a breath (inspiration and expiration) and begins another breath within the set inspiratory time. This can be identified by

Work shifting: During early inspiratory phase, the pressure-time scalar is deviated towards the baseline indicating strong inspiratory effort  Late Cycling: with relaxation of inspiratory muscles and contraction of expiratory muscles the pressure rises above the baseline. Patient completes one breath and starts another breath during the same inspiratory phase (identified by the pressure drop during late inspiratory phase). This pressure drop is sensed by the ventilator and

These breaths are initiated by the patient, and the inspiratory limb of the pressure-time scalar dips below the baseline due to the patient's strong inspiratory efforts (Pmus). This negative intrathoracic pressure, created by the inspiratory muscles, is reflected on the pressure-time scalar. This phenomenon, previously referred to as flow starvation, is now termed work shifting. The steep pressure rise during the inspiratory pause suggests relaxation of the inspiratory muscle

In volume control mode, the morphology of the flow-time scalar is fixed and unaffected by respiratory system mechanics or Pmus. However, in pressure control mode, a strong Pmus can alter the morphology of the pressure-time scalar. Instead of the normal exponential decay, a sinusoidal waveform may appear in the presence of strong Pmus, and there may be an increase in the peak inspiratory flow.  The inspiratory limb of the flow-time scalar may reach the baseline early when ther

In pressure control mode, the pressure remains constant regardless of the respiratory mechanics. Conversely, in volume control mode, the morphology of the pressure-time scalar is influenced by Pmus (muscle pressure generated by inspiratory muscles), resistance, and compliance of the respiratory system.  In volume control mode a stronger Pmus can cause a downward deviation in the pressure-time scalar. Increased resistance results in a higher peak inspiratory pressure and a gre

Work shifting in mechanical ventilation refers to a type of asynchrony where significant work of breathing transferred from the ventilator to the patient.  Suspect work shifting in volume control mode when the inspiratory limb of the pressure time scalar deforms toward the baseline in a patient triggered breath.