Performance of Noninvasive Airway Occlusion Maneuvers to Assess Lung Stress and Diaphragm Effort in Mechanically Ventilated Critically Ill Patients

Abstract

Background Monitoring and controlling lung stress and diaphragm effort has been hypothesized to limit lung injury and diaphragm injury. The occluded inspiratory airway pressure (Pocc) and the airway occlusion pressure at 100ms (P0.1) have been used as non-invasive methods to assess lung stress and respiratory muscle effort, but comparative performance of these measures and their correlation to diaphragm effort is unknown. We hypothesized that Pocc and P0.1 correlate to diaphragm effort and lung stress, and would have strong discriminative performance in identifying extremes of lung stress and diaphragm effort. Methods Secondary analysis of two studies. Transdiaphragmatic pressure (ΔPdi) and transpulmonary pressure (ΔPL) were obtained with double-balloon nasogastric catheters in critically ill patients (n = 38). Pocc and P0.1 were measured every 1-3 hours. Correlations between Pocc and P0.1 with ΔPL and ΔPdi were computed from patients from the first cohort. Accuracy of Pocc and P0.1 to identify patients with extremes of lung stress (ΔPL>20cmH2O) and diaphragm effort (ΔPdi <3cmH2O and >12cmH2O) in the preceding hour was assessed with area under receiver-operator characteristic curves (AUROC). Cut-offs were validated in patients from the second cohort (n = 13). Results Pocc and P0.1 correlate with ΔPL (r2=0.62 and 0.51, respectively) and ΔPdi (r2 = 0.53 and 0.22, respectively). AUROC to detect high lung stress is 0.90 (0.86–0.94) for Pocc and 0.88 (0.84-0.92) for P0.1. AUROC to detect low diaphragm effort is 0.97 (0.87–1.00) for Pocc and 0.93 (0.81–0.99) for P0.1. AUROC to detect high diaphragm effort is 0.86 (0.81–0.91) for Pocc and 0.73 (0.66-0.79) for P0.1. Performance was similar in the external dataset. Conclusions Pocc and P0.1 correlate with lung stress and diaphragm effort in the preceding hour. Diagnostic performance of Pocc and P0.1 to detect extremes in these parameters is reasonable to excellent. Pocc is more accurate in detecting high diaphragm effort.

State of the art: Monitoring of the respiratory system during veno-venous extracorporeal membrane oxygenation

“…This negative pressure should be inclusive of the change from total PEEP and can be used to estimate P mus and ΔP L associated with inspiratory efforts (Table 4). [151][152][153] The P0.1 can also be used to estimate P mus and ΔP L but it is less accurate than the P occ . 153 Estimated ΔP L using P occ has been validated for a very high 'excessive' threshold of ΔP L >20 in the literature.…”

“…The P occ and P0.1 can be used to estimate the ΔP L as has been recently described and validated although the P occ is more accurate. 151,153 In awake patients, self-reported dyspnoea is a helpful adjunct to these measures. Depending on the individual assessment, we use these tools to guide interventions to correct high or low efforts, aiming for a balance of low MP (<6-10 J/min), low P L (End inspiratory P L <20 cmH 2 O or Panel A: Although the superiority of one approach over the other has not been demonstrated, given the downsides of setting PEEP empirically or according to oxygenation or compliance, we routinely assess recruitability using a variety of approaches including low flow pressure volume loops including metrics such as the NMD, measuring the R:I or assessing imaging such as CT at multiple airway pressure levels.…”

“…151–153 The P0.1 can also be used to estimate P mus and ΔP L but it is less accurate than the P occ . 153 Estimated ΔP L using P occ has been validated for a very high ‘excessive’ threshold of ΔP L >20 in the literature. 151–153 In practice, for patients supported with ECMO we generally target a lower ΔP L of <10–12 cmH 2 O, although the accuracy of P occ has not yet been validated for this lower target range.(3) Careful visual assessment of flow curves during assisted ventilation can also be helpful in assessing high inspiratory effort (panel B Figure 3).…”

“…153 Estimated ΔP L using P occ has been validated for a very high ‘excessive’ threshold of ΔP L >20 in the literature. 151–153 In practice, for patients supported with ECMO we generally target a lower ΔP L of <10–12 cmH 2 O, although the accuracy of P occ has not yet been validated for this lower target range.(3) Careful visual assessment of flow curves during assisted ventilation can also be helpful in assessing high inspiratory effort (panel B Figure 3). 154 …”

Monitoring Respiratory Effort and Lung-distending Pressure Noninvasively during Mechanical Ventilation: Ready for Prime Time

“…In this edition of Anesthesiology , de Vries et al 4 evaluated the performance of two noninvasive techniques for monitoring respiratory effort and lung-distending pressure: the inspiratory occlusion pressure (Pocc), and the airway occlusion pressure in the first 100 ms (P 0.1 ). Using data from 38 patients enrolled in a randomized trial testing a strategy to facilitate safe spontaneous breathing during mechanical ventilation, they demonstrate the utility of these measurements to monitor diaphragmatic effort and lung-distending pressure during mechanical ventilation.…”