The following is a summary of “Physiological effects of awake prone position in acute hypoxemic respiratory failure,” published in the August 2023 issue of Critical Care by Grieco et al.

Gaining insight into breathing pattern changes in hypoxemic patients through awake-prone positioning. Researchers conducted a retrospective crossover trial to evaluate the awake prone position’s physiological impact on acute hypoxemic respiratory failure patients.

They observed fifteen patients with acute hypoxemic respiratory failure (PaO₂/FiO₂< 200 mmHg) who underwent high-flow nasal oxygen in both supine and prone positions for different timeframes. Following each study phase, they measured various parameters, including arterial blood gases, inspiratory effort (ΔP_ES), transpulmonary driving pressure (ΔP_L), respiratory rate and esophageal pressure simplified–time product per minute (sPTP_ES) using esophageal manometry. Tidal volume (V_T), end-expiratory lung impedance (EELI), lung compliance, airway resistance, time constant, dynamic strain (V_T/EELI), and pendelluft extent via electrical impedance tomography were assessed.

The results showed prone position, as compared to supine, raised PaO₂/FiO₂(median [Interquartile range]: 104 mmHg [76–129] vs. 74 [69–93], P< 0.001), lowered respiratory rate (24 breaths/min [22–26] vs. 27 [26–30], P= 0.05), and elevated ΔP_ES (12 cmH2O [11–13] vs. 9 [8–12], P= 0.04). The sPTP_ES (131 [75–154] cmH₂O s min−^-1 vs. 105 [81–129], P> 0.99) and Δ_PL (9 [7–11] cmH₂O vs. 8 [5–9], P= 0.17) remained similar. Prone showed higher airway resistance and time constant compared to supine (9 cmH₂O s arbitrary units^-3 [4–11] vs. 6 [4–9], P= 0.05; 0.53 s [0.32–61] vs. 0.40 [0.37–0.44], P= 0.03). EELI increased in prone (3887 arbitrary units [3414–8547] vs. 1456 [959–2420], P= 0.002), promoting V_T distribution to dorsal lung regions without altering V_T size and lung compliance, yielding lower dynamic strain (0.21 [0.16–0.24] vs. 0.38 [0.30–0.49], P= 0.004). Pendelluft phenomenon’s magnitude didn’t differ between study phases (55% [7–57] of V_T in prone vs. 31% [14–55] in supine, P> 0.99).

They concluded that the prone position improves V_T, EELI, Δ_PL, pendelluft magnitude, and lung compliance without affecting V_T size.

Source: ccforum.biomedcentral.com/articles/10.1186/s13054-023-04600-9