Intubated asthmatic patients should continue to receive aggressive treatment with ? in the initial hours after intubation, in an effort to relax the chest wall musculature and gain control of the situation.
Please note that neuromuscular blockade only works on skeletal muscle and therefore, will not bronchodilate smooth muscle in the airways. In addition, it is very critical to be aware of the patient's ? status, as the excess positive pressure can lead to hemodynamic collapse. Moreover, the excess pressure, including the auto-PEEP, can result in barotrauma, such as the development of a pneumothorax very quickly in this patient population.
Four ventilator maneuvers increase expiratory time, namely, ? Of these, decreasing the respiratory rate is the most effective means to allow more time to exhale.
In addition to a slow respiratory rate, a low I:E ratio, a short inspiratory time and/or a fast inspiratory flow rate, asthmatics should also be ventilated with low tidal volumes. Considering that the larger the tidal volume, the more the patient has to exhale, this is fairly intuitive.
initial vent settings in asthma:
Tidal Volume-- ?
Respiratory Rate -- ?breaths/minute, allowing for permissive hypercapnia
PEEP~ ? cmH2O
FiO2- Decrease as tolerated, SpO2 ≥ 92%
Most patients with COPD are now managed with BPAP, with improved outcomes over intubation. However, on occasion, a patient with COPD is not a candidate for BPAP or fails to improve with a trial of BPAP, mandating intubation and invasive mechanical ventilation.
With the destruction of parenchyma, the small airways can collapse with exhalation, trapping air behind. In this circumstance, this trapped air leads to autoPEEP. Increasing the set PEEP, to match the autoPEEP, is not necessarily an intuitive solution. However, as illustrated by the diagram below, increasing the PEEP to prevent collapse of these small airways can allow the patient to exhale more fully.
Lastly, patients with COPD are often chronically hypoxemic. Indications of chronic hypoxemia physical exam findings of chronic hypoxemia can be demonstrated with nail clubbing. Additionally, can include an elevated hemoglobin level on the CBC, indicating the patient's compensation for their chronic lung disease. Because these patients are baseline hypoxemic, and ventilation is often a relatively greater issue for them than hypoxemia, the oxygen saturation for a patient with COPD should be targeted at 88-92% in most circumstances.
initial vent settings for COPDr:
Tidal Volume--6-8 ml/kg PBW
Respiratory Rate-- 6 - 20 breaths/minute, allowing for permissive hypercapnia
FiO2-- Decrease as tolerated, SpO2 target 88-92%
To understand patient behavior, it is important to understand asynchrony, which includes:
in mechanically ventilated patients a P0.1 >? is considered abnormal
In pressure assist control, patient effort should change the flow waveform. In this, it is important to check if the flow ? during inspiration or if there is ? during exhalation to ensure the patient is not experiencing asynchrony with breath timing. This can be adjusted by shortening or lengthening the inspiratory time. Similarly, p0.1 can be monitored to evaluate whether a patient is experiencing excessive effort in which increasing ?. ? can also be adjusted to attempt to improve the patient's drive.
In pressure support, it may be necessary to alter the ? that causes cycling off to eliminate asynchrony. If the patient is demonstrating excessive effort, increasing the pressure support will help decrease the patient's drive. However, if increasing pressure support does not decrease the p0.1, reducing the drive must be prioritized. PEEP can also be adjusted to attempt to improve the patient's drive.
Delayed cycling is another phenomena where the patient wants to ? but ?. In pressure assist control, if there is an increase ? with a subsequent ?, then the patient is most likely experiencing delayed cycling. As a result, the inspiratory time should be ?. However, the time should be not shortened so much that it causes ?, in which the patient's effort lasts longer than the ventilator's cycle off criteria. This will manifest as a dampening in the?. Premature cycling can also occur in pressure support, when the ?. This flow scalar will look similar to that for premature cycling in pressure assist control.
Ineffective efforts are another form of asynchrony that generally occurs when patients are ?. Delayed cycling is a common cause of ineffective efforts.
Reverse triggering is another form of asynchrony where the ventilator triggers a breath that then triggers an effort from the patient. This can also lead to breath stacking. The first thing to check when noting reverse triggering is to see if it is bad timing or reflex. To check this, first ?. After reducing the respiratory rate, if the patient is triggering the breaths, it was simply bad timing.
However, if the reverse triggering still continues, a few steps should be taken:
Turn off ?
Keep plateau pressure less than or equal to 27 cmH2O, and less than 30cmH2O for COVID-19 patients (typical ARDS guidelines).
If there is a known injurious pattern (breath stacking) and sedation cannot be stopped, consider ?