Uses and misuses of oxygen in hospitalized patients.

PURPOSE: To document the use/misuse of oxygen therapy as compared with antibiotics in internal medicine inpatients. To determine whether the same care was being taken in the prescription and administration of both forms of therapy. PATIENTS: Ninety-six eligible patients at a university teaching hospital were entered into a study examining the use of oxygen. They were compared with 60 patients for whom antibiotics were prescribed. MATERIAL AND METHODS: Three hundred thirty consecutive newly admitted patients were screened for the presence of either (1) oxygen apparatus at the bedside, (2) physician orders for oxygen, or (3) oxygen orders noted in nursing kardex. Those meeting one of these three criteria were observed on up to four occasions over 48 hours following study entry. Similarly, patients were screened for medical orders or nursing medication kardex notation for antibiotics and were also observed for proper prescription and administration of medication. Procedural errors, determined by kardex audit and direct patient observation, were compared for the individuals with specific oxygen orders and those receiving antibiotics. RESULTS: Oxygen delivery apparatus was found in the room in 17 of 96 patients without it ever having been ordered by the physician or noted in the nursing kardex. In 27 of 96 patients, oxygen was noted in the nursing kardex and administered to patients without a physician order. There were no cases of antibiotic therapy without a physician order. Observations of 47 patients with specific orders for oxygen revealed the following errors: (1) physician order incorrectly transcribed to nursing kardex (16%), (2) flow meter off (34%), (3) oxygen delivery apparatus improperly worn (57%), (4) wrong fractional inspired oxygen concentration (58%). Improper transcription of antibiotic orders occurred on only one occasion (2%), and antibiotics were improperly administered in 5%. Arterial blood gas determinations preceded oxygen orders in 61%, whereas microbiologic cultures preceded antibiotic orders in 87% of the patients. CONCLUSIONS: We conclude that oxygen therapy is neither prescribed nor administered with the same attention that is given to other drugs such as antibiotics. Oxygen prescription and/or delivery is associated with significantly greater error than that seen with antibiotics. Education of medical personnel should stress more prudent prescription and use of oxygen in hospitalized patients.

Assessment of transdiaphragmatic pressure in humans.

Maximal force developed by the diaphragm at functional residual capacity is a useful index to establish muscle weakness; however, great disparity in its reproducibility can be observed among reports in the literature. We evaluated five maneuvers to measure maximal transdiaphragmatic pressure (Pdimax) in order to establish best reproducibility and value. Thirty-five naïve subjects, including 10 normal subjects (group 1), 12 patients with chronic obstructive pulmonary disease (group 2), and 13 patients with restrictive pulmonary disease (group 3), were studied. Each subject performed five separate maneuvers in random order that were repeated until reproducible values were obtained. The maneuvers were Mueller with (A) and without mouthpiece (B), abdominal expulsive effort with open glottis (C), two-step (maneuver C combined with Mueller effort) (D), and feedback [two-step with visual feedback of pleural (Ppl) and abdominal (Pab) pressure] (E). The greatest reproducible Pdimax values were obtained with maneuver E (P less than 0.01) (group 1: 180 +/- 14 cmH2O). The second best maneuvers were A, B, and D (group 1: 154 +/- 25 cmH2O). Maneuver C produced the lowest values. For all maneuvers, group 1 produced higher values than groups 2 and 3 (P less than 0.001), which were similar. The Ppl to Pdi ratio was 0.6 in maneuvers A and B, 0.4 in D and E, and 0.2 in C. We conclude that visual feedback of Ppl and Pab helped the subjects to elicit maximal diaphragmatic effort in a reproducible fashion. It is likely that the great variability of values in Pdimax previously reported are the result of inadequate techniques.

Influence of site of tracheal pressure measurement on in situ estimation of endotracheal tube resistance.

In situ measurement of distal tracheal pressure (Ptr) via an intraluminal side-hole catheter (IC) has been used to determine endotracheal tube (Rett) and intrinsic patient (Rpt) resistances in intubated subjects. Because of differences in cross-sectional area between the endotracheal tube (ETT) and trachea, fluid dynamic principles predict that IC position should critically influence these results. Accordingly, the aim of this study was to determine the effect of IC position on Rett. Ptr was recorded in vitro through an IC from 2 cm inside, at the tip of, or 2 cm outside an ETT (7, 8, and 9 mm ID) situated within an artificial trachea (13, 18, and 22 mm ID). A reference value of Rett was also obtained. Results were unaffected by IC position during inspiration, overestimating Rett by 7.9 +/- 0.7% (SE). In contrast, during expiration, Rett fell as IC position changed from outside to inside the ETT and was underestimated by 41.3 +/- 3.6% with Ptr recorded inside the ETT. Varying ETT or tracheal size had little effect on the relative error in Rett. The IC itself did increase Rett due to a reduction in effective cross-sectional area, the change varying directly with IC size and inversely with ETT caliber. In vivo values in 11 intubated patients were comparable to in vitro results. In summary, IC position and size can have important consequences on in situ measurements of Ptr and should be considered when clinically monitoring Rett or Rpt.

Prevention of venous thromboembolism in critically ill surgery patients: a cross-sectional study.

BACKGROUND: The risk for venous thromboembolism (VTE) and the risk for bleeding among critically ill surgical patients are both important in the early postoperative period. MATERIALS AND METHODS: To record VTE prophylaxis prescribed for surgical patients in the intensive care unit (ICU) within the first postoperative week. We conducted a prospective observational cross-sectional study of Canadian university affiliated ICUs. RESULTS: Of 29 ICU Directors approached, 28 (96.6%) participated, representing 34 ICUs and 589 ICU beds across Canada. Among 89 patients, surgical procedures were 32 abdominal (36.0%), 19 vascular (21.3%), 10 orthopedic (11.2%), 9 trauma (10.1%), 8 neurologic (9.0%), 5 thoracic (5.6%), 5 gynecologic (5.6%), and 1 for necrotizing fasciitis (1.1%). VTE prophylaxis with unfractionated heparin, low molecular weight heparin, and intermittent pneumatic compression was used in 35 of 89 (39.3%), 8 of 89 (9.0%), and 9 of 89 (10.1%) patients, respectively, whereas 8 of 89 (9.0%) patients were receiving therapeutic anticoagulation. Two methods of VTE prophylaxis were prescribed for 20 of 89 (22.5%) patients. Prophylaxis with unfractionated or low molecular weight heparin was significantly less likely to be prescribed for postoperative ICU patients requiring mechanical ventilation compared with those weaned from mechanical ventilation (odds ratio [OR] 0.36, P =.03). The use of intermittent pneumatic compression devices was significantly associated with current hemorrhage (OR 13.5, P =.02), and risk for future hemorrhage (OR 19.3, P =.001). CONCLUSIONS: VTE prevention for surgical ICU patients within the first postoperative week appear to be individualized, and influenced by current and future risks of thrombosis and bleeding.

The Austin bunionectomy: a follow-up study.

The Austin procedure, a distal metaphyseal "V" osteotomy for the management of hallux valgus was evaluated in several distinct patient groups. The results of the procedure were found to be both reproducible and predictable. Medial capsular reefing in an attempt to maintain the intermetatarsal angle reduction or hallux alignment does not appear to enhance the postoperative results.

Respiratory phase locking during mechanical ventilation in anesthetized human subjects.

The coupling patterns between the rhythm of a mechanical ventilator and the rhythm of spontaneous breathing were studied in enflurane-anesthetized adult human subjects. The spontaneous breathing pattern was altered in response to different frequencies and amplitudes of forced lung inflations. A 1:1 phase locking (the frequency of the mechanical ventilator is matched by the frequency of spontaneous breathing with a fixed phase between the 2 rhythms) was observed in a range of up to +/- 40% of some of the subject's spontaneous breathing frequencies. During 1:1 phase locking, there were marked changes in the expiratory duration as measured from the electromyogram of the diaphragm. The phase relationship between onset of inflation and onset of inspiration depended on the frequency and amplitude of mechanical inflation. At ventilator settings that did not give 1:1 phase locking, other simple phase-locked patterns, such as 1:2 and 2:1, or irregular non-phase-locked patterns were observed. Reflexes arising from lung inflation, which may underlie the entrainment, are discussed in the context of these results.

Proportional assist ventilation in acute respiratory failure: effects on breathing pattern and inspiratory effort.

Proportional assist ventilation (PAV) is a new mode of assisted ventilation which, by applying pressure in proportion to volume (volume assist, VA) and flow (flow assist, FA), should specifically reduce the inspiratory effort needed to overcome respiratory system elastance (Ers) and resistance (Rrs), respectively. The aims of this study were to determine (1) the effects of varying the level of VA on breathing pattern, inspiratory effort, and work of breathing, and (2) the interaction between VA and FA. In eight intubated patients with acute respiratory failure, four levels of VA (20 to 80% Ers) with and without a fixed amount of FA (approximately 50% Rrs) were evaluated. Compared with spontaneous breathing, VA increased tidal volume (VT) while respiratory rate (RR) was unchanged or fell slightly. The increase in minute ventilation (VE) was small and not significant. The addition of FA further increased VT while RR was significantly reduced so that VE remained unchanged. Increasing VA produced a graded reduction in inspiratory effort, reflected by decreases in the pressure-time integral of the diaphragm and the inspiratory muscles. These were further reduced when FA was added. VA decreased the elastic work of breathing (Wel) whereas resistive work (Wres) tended to increase so that the fall in total work (W/tot) was less than expected. At each VA setting, the addition of FA significantly reduced Wres and, as a result, Wtot. These results demonstrate that PAV can improve breathing pattern while reducing inspiratory effort by specifically decreasing Wel and Wres, and that VA and FA should be used together to optimize reductions in Wtot and the efficacy of assistance provided.

Absorbable fixation of first ray osteotomies.

A study was undertaken to evaluate the use of ORTHOSORB absorbable pin fixation for distal first ray osteotomies, in the management of hallux valgus. Data presented include 20 osteotomies fixated with ORTHOSORB absorbable pins in a crossing fashion, performed in 14 patients with an average follow-up period of 11 months. The patient population presented with an average age of 30, all were female. The patient pool was evaluated for hallux abductus, metatarsus primus varus, tibial sesamoid position, quality and quantity of range of motion at the first metatarsophalangeal joint, metatarsalgia, and osteolysis, both before and after surgery. No osteotomy displacement, delayed healing, or osteonecrosis was noted in this study. No adverse clinical reactions were observed in response to the ORTHOSORB pins.

Endothelin-1 in acute lung injury and the adult respiratory distress syndrome.

Endothelial damage is a hallmark of acute lung injury. Endothelial mediators may increase pulmonary vascular tone and induce pulmonary arterial muscularization, thereby contributing to the pulmonary hypertension seen with acute lung injury. We measured plasma levels and net pulmonary clearance of endothelin-1, a potent endothelium-derived vasoconstrictor peptide and smooth muscle mitogen, in 26 patients with early acute lung injury, the adult respiratory distress syndrome, and pulmonary hypertension. Nineteen had another data collection at clinical improvement or worsening. Control subjects (n = 25) had no pulmonary hypertension or lung injury. Initial mixed venous and systemic arterial plasma endothelin-1 levels were elevated (4.6 +/- 0.6 SEM and 4.9 +/- 0.6 pg/ml, respectively) as compared with control subjects (0.9 +/- 0.1 and 0.6 +/- 0.1 pg/ml). The systemic arterial/venous endothelin-1 ratio was 1.1 +/- 0.1 (0.7 +/- 0.1 in control subjects), indicating a reduction in normal net pulmonary endothelin-1 clearance. With clinical improvement, as compared with clinical worsening, mean plasma endothelin-1 levels, arterial/venous ratio, and pulmonary arterial pressure fell significantly towards normal. Thus, patients with acute lung injury have marked early increases in circulating plasma endothelin-1 levels, associated with abnormal pulmonary endothelin-1 metabolism. These abnormalities reverse in patients who recover. Through its actions, endothelin-1 could contribute to the pulmonary hypertension seen in acute lung injury.